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crypto.c

// TODO key loading, generating, saving
#include "quakedef.h"
#include "crypto.h"
#include "common.h"

#include "hmac.h"
#include "libcurl.h"

cvar_t crypto_developer = {CVAR_SAVE, "crypto_developer", "0", "print extra info about crypto handshake"};
cvar_t crypto_servercpupercent = {CVAR_SAVE, "crypto_servercpupercent", "10", "allowed crypto CPU load in percent for server operation (0 = no limit, faster)"};
cvar_t crypto_servercpumaxtime = {CVAR_SAVE, "crypto_servercpumaxtime", "0.01", "maximum allowed crypto CPU time per frame (0 = no limit)"};
cvar_t crypto_servercpudebug = {CVAR_SAVE, "crypto_servercpudebug", "0", "print statistics about time usage by crypto"};
static double crypto_servercpu_accumulator = 0;
static double crypto_servercpu_lastrealtime = 0;
cvar_t crypto_aeslevel = {CVAR_SAVE, "crypto_aeslevel", "1", "whether to support AES encryption in authenticated connections (0 = no, 1 = supported, 2 = requested, 3 = required)"};
int crypto_keyfp_recommended_length;
static const char *crypto_idstring = NULL;
static char crypto_idstring_buf[512];

#define PROTOCOL_D0_BLIND_ID FOURCC_D0PK
#define PROTOCOL_VLEN (('v' << 0) | ('l' << 8) | ('e' << 16) | ('n' << 24))

// BEGIN stuff shared with crypto-keygen-standalone
#define FOURCC_D0PK (('d' << 0) | ('0' << 8) | ('p' << 16) | ('k' << 24))
#define FOURCC_D0SK (('d' << 0) | ('0' << 8) | ('s' << 16) | ('k' << 24))
#define FOURCC_D0PI (('d' << 0) | ('0' << 8) | ('p' << 16) | ('i' << 24))
#define FOURCC_D0SI (('d' << 0) | ('0' << 8) | ('s' << 16) | ('i' << 24))
#define FOURCC_D0IQ (('d' << 0) | ('0' << 8) | ('i' << 16) | ('q' << 24))
#define FOURCC_D0IR (('d' << 0) | ('0' << 8) | ('i' << 16) | ('r' << 24))
#define FOURCC_D0ER (('d' << 0) | ('0' << 8) | ('e' << 16) | ('r' << 24))
#define FOURCC_D0IC (('d' << 0) | ('0' << 8) | ('i' << 16) | ('c' << 24))

static unsigned long Crypto_LittleLong(const char *data)
{
      return
            ((unsigned char) data[0]) |
            (((unsigned char) data[1]) << 8) |
            (((unsigned char) data[2]) << 16) |
            (((unsigned char) data[3]) << 24);
}

static void Crypto_UnLittleLong(char *data, unsigned long l)
{
      data[0] = l & 0xFF;
      data[1] = (l >> 8) & 0xFF;
      data[2] = (l >> 16) & 0xFF;
      data[3] = (l >> 24) & 0xFF;
}

static size_t Crypto_ParsePack(const char *buf, size_t len, unsigned long header, const char **lumps, size_t *lumpsize, size_t nlumps)
{
      size_t i;
      size_t pos;
      pos = 0;
      if(header)
      {
            if(len < 4)
                  return 0;
            if(Crypto_LittleLong(buf) != header)
                  return 0;
            pos += 4;
      }
      for(i = 0; i < nlumps; ++i)
      {
            if(pos + 4 > len)
                  return 0;
            lumpsize[i] = Crypto_LittleLong(&buf[pos]);
            pos += 4;
            if(pos + lumpsize[i] > len)
                  return 0;
            lumps[i] = &buf[pos];
            pos += lumpsize[i];
      }
      return pos;
}

static size_t Crypto_UnParsePack(char *buf, size_t len, unsigned long header, const char *const *lumps, const size_t *lumpsize, size_t nlumps)
{
      size_t i;
      size_t pos;
      pos = 0;
      if(header)
      {
            if(len < 4)
                  return 0;
            Crypto_UnLittleLong(buf, header);
            pos += 4;
      }
      for(i = 0; i < nlumps; ++i)
      {
            if(pos + 4 + lumpsize[i] > len)
                  return 0;
            Crypto_UnLittleLong(&buf[pos], lumpsize[i]);
            pos += 4;
            memcpy(&buf[pos], lumps[i], lumpsize[i]);
            pos += lumpsize[i];
      }
      return pos;
}
// END stuff shared with xonotic-keygen

#define USE_AES

#ifdef CRYPTO_STATIC

#include <d0_blind_id/d0_blind_id.h>

#define d0_blind_id_dll 1
#define Crypto_OpenLibrary() true
#define Crypto_CloseLibrary()

#define qd0_blind_id_new d0_blind_id_new
#define qd0_blind_id_free d0_blind_id_free
//#define qd0_blind_id_clear d0_blind_id_clear
#define qd0_blind_id_copy d0_blind_id_copy
//#define qd0_blind_id_generate_private_key d0_blind_id_generate_private_key
//#define qd0_blind_id_generate_private_key_fastreject d0_blind_id_generate_private_key_fastreject
//#define qd0_blind_id_read_private_key d0_blind_id_read_private_key
#define qd0_blind_id_read_public_key d0_blind_id_read_public_key
//#define qd0_blind_id_write_private_key d0_blind_id_write_private_key
//#define qd0_blind_id_write_public_key d0_blind_id_write_public_key
#define qd0_blind_id_fingerprint64_public_key d0_blind_id_fingerprint64_public_key
//#define qd0_blind_id_generate_private_id_modulus d0_blind_id_generate_private_id_modulus
#define qd0_blind_id_read_private_id_modulus d0_blind_id_read_private_id_modulus
//#define qd0_blind_id_write_private_id_modulus d0_blind_id_write_private_id_modulus
#define qd0_blind_id_generate_private_id_start d0_blind_id_generate_private_id_start
#define qd0_blind_id_generate_private_id_request d0_blind_id_generate_private_id_request
//#define qd0_blind_id_answer_private_id_request d0_blind_id_answer_private_id_request
#define qd0_blind_id_finish_private_id_request d0_blind_id_finish_private_id_request
//#define qd0_blind_id_read_private_id_request_camouflage d0_blind_id_read_private_id_request_camouflage
//#define qd0_blind_id_write_private_id_request_camouflage d0_blind_id_write_private_id_request_camouflage
#define qd0_blind_id_read_private_id d0_blind_id_read_private_id
//#define qd0_blind_id_read_public_id d0_blind_id_read_public_id
#define qd0_blind_id_write_private_id d0_blind_id_write_private_id
//#define qd0_blind_id_write_public_id d0_blind_id_write_public_id
#define qd0_blind_id_authenticate_with_private_id_start d0_blind_id_authenticate_with_private_id_start
#define qd0_blind_id_authenticate_with_private_id_challenge d0_blind_id_authenticate_with_private_id_challenge
#define qd0_blind_id_authenticate_with_private_id_response d0_blind_id_authenticate_with_private_id_response
#define qd0_blind_id_authenticate_with_private_id_verify d0_blind_id_authenticate_with_private_id_verify
#define qd0_blind_id_fingerprint64_public_id d0_blind_id_fingerprint64_public_id
#define qd0_blind_id_sessionkey_public_id d0_blind_id_sessionkey_public_id
#define qd0_blind_id_INITIALIZE d0_blind_id_INITIALIZE
#define qd0_blind_id_SHUTDOWN d0_blind_id_SHUTDOWN
#define qd0_blind_id_util_sha256 d0_blind_id_util_sha256
#define qd0_blind_id_sign_with_private_id_sign d0_blind_id_sign_with_private_id_sign
#define qd0_blind_id_sign_with_private_id_sign_detached d0_blind_id_sign_with_private_id_sign_detached

#else

// d0_blind_id interface
#define D0_EXPORT
#ifdef __GNUC__
#define D0_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
#else
#define D0_WARN_UNUSED_RESULT
#endif
#define D0_BOOL int

typedef struct d0_blind_id_s d0_blind_id_t;
typedef D0_BOOL (*d0_fastreject_function) (const d0_blind_id_t *ctx, void *pass);
static D0_EXPORT D0_WARN_UNUSED_RESULT d0_blind_id_t *(*qd0_blind_id_new) (void);
static D0_EXPORT void (*qd0_blind_id_free) (d0_blind_id_t *a);
//static D0_EXPORT void (*qd0_blind_id_clear) (d0_blind_id_t *ctx);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_copy) (d0_blind_id_t *ctx, const d0_blind_id_t *src);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_generate_private_key) (d0_blind_id_t *ctx, int k);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_generate_private_key_fastreject) (d0_blind_id_t *ctx, int k, d0_fastreject_function reject, void *pass);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_read_private_key) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_read_public_key) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_write_private_key) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_write_public_key) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_fingerprint64_public_key) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_generate_private_id_modulus) (d0_blind_id_t *ctx);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_read_private_id_modulus) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_write_private_id_modulus) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_generate_private_id_start) (d0_blind_id_t *ctx);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_generate_private_id_request) (d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_answer_private_id_request) (const d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_finish_private_id_request) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_read_private_id_request_camouflage) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_write_private_id_request_camouflage) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_read_private_id) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_read_public_id) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_write_private_id) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
//static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_write_public_id) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_authenticate_with_private_id_start) (d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL send_modulus, const char *message, size_t msglen, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_authenticate_with_private_id_challenge) (d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL recv_modulus, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen, D0_BOOL *status);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_authenticate_with_private_id_response) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_authenticate_with_private_id_verify) (d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *msg, size_t *msglen, D0_BOOL *status);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_fingerprint64_public_id) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_sessionkey_public_id) (const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen); // can only be done after successful key exchange, this performs a modpow; key length is limited by SHA_DIGESTSIZE for now; also ONLY valid after successful d0_blind_id_authenticate_with_private_id_verify/d0_blind_id_fingerprint64_public_id
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_INITIALIZE) (void);
static D0_EXPORT void (*qd0_blind_id_SHUTDOWN) (void);
static D0_EXPORT void (*qd0_blind_id_util_sha256) (char *out, const char *in, size_t n);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_sign_with_private_id_sign) (d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL send_modulus, const char *message, size_t msglen, char *outbuf, size_t *outbuflen);
static D0_EXPORT D0_WARN_UNUSED_RESULT D0_BOOL (*qd0_blind_id_sign_with_private_id_sign_detached) (d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL send_modulus, const char *message, size_t msglen, char *outbuf, size_t *outbuflen);
static dllfunction_t d0_blind_id_funcs[] =
{
      {"d0_blind_id_new", (void **) &qd0_blind_id_new},
      {"d0_blind_id_free", (void **) &qd0_blind_id_free},
      //{"d0_blind_id_clear", (void **) &qd0_blind_id_clear},
      {"d0_blind_id_copy", (void **) &qd0_blind_id_copy},
      //{"d0_blind_id_generate_private_key", (void **) &qd0_blind_id_generate_private_key},
      //{"d0_blind_id_generate_private_key_fastreject", (void **) &qd0_blind_id_generate_private_key_fastreject},
      //{"d0_blind_id_read_private_key", (void **) &qd0_blind_id_read_private_key},
      {"d0_blind_id_read_public_key", (void **) &qd0_blind_id_read_public_key},
      //{"d0_blind_id_write_private_key", (void **) &qd0_blind_id_write_private_key},
      //{"d0_blind_id_write_public_key", (void **) &qd0_blind_id_write_public_key},
      {"d0_blind_id_fingerprint64_public_key", (void **) &qd0_blind_id_fingerprint64_public_key},
      //{"d0_blind_id_generate_private_id_modulus", (void **) &qd0_blind_id_generate_private_id_modulus},
      {"d0_blind_id_read_private_id_modulus", (void **) &qd0_blind_id_read_private_id_modulus},
      //{"d0_blind_id_write_private_id_modulus", (void **) &qd0_blind_id_write_private_id_modulus},
      {"d0_blind_id_generate_private_id_start", (void **) &qd0_blind_id_generate_private_id_start},
      {"d0_blind_id_generate_private_id_request", (void **) &qd0_blind_id_generate_private_id_request},
      //{"d0_blind_id_answer_private_id_request", (void **) &qd0_blind_id_answer_private_id_request},
      {"d0_blind_id_finish_private_id_request", (void **) &qd0_blind_id_finish_private_id_request},
      //{"d0_blind_id_read_private_id_request_camouflage", (void **) &qd0_blind_id_read_private_id_request_camouflage},
      //{"d0_blind_id_write_private_id_request_camouflage", (void **) &qd0_blind_id_write_private_id_request_camouflage},
      {"d0_blind_id_read_private_id", (void **) &qd0_blind_id_read_private_id},
      //{"d0_blind_id_read_public_id", (void **) &qd0_blind_id_read_public_id},
      {"d0_blind_id_write_private_id", (void **) &qd0_blind_id_write_private_id},
      //{"d0_blind_id_write_public_id", (void **) &qd0_blind_id_write_public_id},
      {"d0_blind_id_authenticate_with_private_id_start", (void **) &qd0_blind_id_authenticate_with_private_id_start},
      {"d0_blind_id_authenticate_with_private_id_challenge", (void **) &qd0_blind_id_authenticate_with_private_id_challenge},
      {"d0_blind_id_authenticate_with_private_id_response", (void **) &qd0_blind_id_authenticate_with_private_id_response},
      {"d0_blind_id_authenticate_with_private_id_verify", (void **) &qd0_blind_id_authenticate_with_private_id_verify},
      {"d0_blind_id_fingerprint64_public_id", (void **) &qd0_blind_id_fingerprint64_public_id},
      {"d0_blind_id_sessionkey_public_id", (void **) &qd0_blind_id_sessionkey_public_id},
      {"d0_blind_id_INITIALIZE", (void **) &qd0_blind_id_INITIALIZE},
      {"d0_blind_id_SHUTDOWN", (void **) &qd0_blind_id_SHUTDOWN},
      {"d0_blind_id_util_sha256", (void **) &qd0_blind_id_util_sha256},
      {"d0_blind_id_sign_with_private_id_sign", (void **) &qd0_blind_id_sign_with_private_id_sign},
      {"d0_blind_id_sign_with_private_id_sign_detached", (void **) &qd0_blind_id_sign_with_private_id_sign_detached},
      {NULL, NULL}
};
// end of d0_blind_id interface

static dllhandle_t d0_blind_id_dll = NULL;
static qboolean Crypto_OpenLibrary (void)
{
      const char* dllnames [] =
      {
#if defined(WIN32)
            "libd0_blind_id-0.dll",
#elif defined(MACOSX)
            "libd0_blind_id.0.dylib",
#else
            "libd0_blind_id.so.0",
            "libd0_blind_id.so", // FreeBSD
#endif
            NULL
      };

      // Already loaded?
      if (d0_blind_id_dll)
            return true;

      // Load the DLL
      return Sys_LoadLibrary (dllnames, &d0_blind_id_dll, d0_blind_id_funcs);
}

static void Crypto_CloseLibrary (void)
{
      Sys_UnloadLibrary (&d0_blind_id_dll);
}

#endif

#ifdef CRYPTO_RIJNDAEL_STATIC

#include <d0_blind_id/d0_rijndael.h>

#define d0_rijndael_dll 1
#define Crypto_Rijndael_OpenLibrary() true
#define Crypto_Rijndael_CloseLibrary()

#define qd0_rijndael_setup_encrypt d0_rijndael_setup_encrypt
#define qd0_rijndael_setup_decrypt d0_rijndael_setup_decrypt
#define qd0_rijndael_encrypt d0_rijndael_encrypt
#define qd0_rijndael_decrypt d0_rijndael_decrypt

#else

// no need to do the #define dance here, as the upper part declares out macros either way

D0_EXPORT int (*qd0_rijndael_setup_encrypt) (unsigned long *rk, const unsigned char *key,
  int keybits);
D0_EXPORT int (*qd0_rijndael_setup_decrypt) (unsigned long *rk, const unsigned char *key,
  int keybits);
D0_EXPORT void (*qd0_rijndael_encrypt) (const unsigned long *rk, int nrounds,
  const unsigned char plaintext[16], unsigned char ciphertext[16]);
D0_EXPORT void (*qd0_rijndael_decrypt) (const unsigned long *rk, int nrounds,
  const unsigned char ciphertext[16], unsigned char plaintext[16]);
#define D0_RIJNDAEL_KEYLENGTH(keybits) ((keybits)/8)
#define D0_RIJNDAEL_RKLENGTH(keybits)  ((keybits)/8+28)
#define D0_RIJNDAEL_NROUNDS(keybits)   ((keybits)/32+6)
static dllfunction_t d0_rijndael_funcs[] =
{
      {"d0_rijndael_setup_decrypt", (void **) &qd0_rijndael_setup_decrypt},
      {"d0_rijndael_setup_encrypt", (void **) &qd0_rijndael_setup_encrypt},
      {"d0_rijndael_decrypt", (void **) &qd0_rijndael_decrypt},
      {"d0_rijndael_encrypt", (void **) &qd0_rijndael_encrypt},
      {NULL, NULL}
};
// end of d0_blind_id interface

static dllhandle_t d0_rijndael_dll = NULL;
static qboolean Crypto_Rijndael_OpenLibrary (void)
{
      const char* dllnames [] =
      {
#if defined(WIN32)
            "libd0_rijndael-0.dll",
#elif defined(MACOSX)
            "libd0_rijndael.0.dylib",
#else
            "libd0_rijndael.so.0",
            "libd0_rijndael.so", // FreeBSD
#endif
            NULL
      };

      // Already loaded?
      if (d0_rijndael_dll)
            return true;

      // Load the DLL
      return Sys_LoadLibrary (dllnames, &d0_rijndael_dll, d0_rijndael_funcs);
}

static void Crypto_Rijndael_CloseLibrary (void)
{
      Sys_UnloadLibrary (&d0_rijndael_dll);
}

#endif

// various helpers
void sha256(unsigned char *out, const unsigned char *in, int n)
{
      qd0_blind_id_util_sha256((char *) out, (const char *) in, n);
}

static size_t Crypto_LoadFile(const char *path, char *buf, size_t nmax)
{
      qfile_t *f = NULL;
      fs_offset_t n;
      if(*fs_userdir)
            f = FS_SysOpen(va("%s%s", fs_userdir, path), "rb", false);
      if(!f)
            f = FS_SysOpen(va("%s%s", fs_basedir, path), "rb", false);
      if(!f)
            return 0;
      n = FS_Read(f, buf, nmax);
      if(n < 0)
            n = 0;
      FS_Close(f);
      return (size_t) n;
}

static qboolean PutWithNul(char **data, size_t *len, const char *str)
{
      // invariant: data points to insertion point
      size_t l = strlen(str);
      if(l >= *len)
            return false;
      memcpy(*data, str, l+1);
      *data += l+1;
      *len -= l+1;
      return true;
}

static const char *GetUntilNul(const char **data, size_t *len)
{
      // invariant: data points to next character to take
      const char *data_save = *data;
      size_t n;
      const char *p;

      if(!*data)
            return NULL;

      if(!*len)
      {
            *data = NULL;
            return NULL;
      }

      p = (const char *) memchr(*data, 0, *len);
      if(!p) // no terminating NUL
      {
            *data = NULL;
            *len = 0;
            return NULL;
      }
      else
      {
            n = (p - *data) + 1;
            *len -= n;
            *data += n;
            if(*len == 0)
                  *data = NULL;
            return (const char *) data_save;
      }
      *data = NULL;
      return NULL;
}

// d0pk reading
static d0_blind_id_t *Crypto_ReadPublicKey(char *buf, size_t len)
{
      d0_blind_id_t *pk = NULL;
      const char *p[2];
      size_t l[2];
      if(Crypto_ParsePack(buf, len, FOURCC_D0PK, p, l, 2))
      {
            pk = qd0_blind_id_new();
            if(pk)
                  if(qd0_blind_id_read_public_key(pk, p[0], l[0]))
                        if(qd0_blind_id_read_private_id_modulus(pk, p[1], l[1]))
                              return pk;
      }
      if(pk)
            qd0_blind_id_free(pk);
      return NULL;
}

// d0si reading
static qboolean Crypto_AddPrivateKey(d0_blind_id_t *pk, char *buf, size_t len)
{
      const char *p[1];
      size_t l[1];
      if(Crypto_ParsePack(buf, len, FOURCC_D0SI, p, l, 1))
      {
            if(qd0_blind_id_read_private_id(pk, p[0], l[0]))
                  return true;
      }
      return false;
}

#define MAX_PUBKEYS 16
static d0_blind_id_t *pubkeys[MAX_PUBKEYS];
static char pubkeys_fp64[MAX_PUBKEYS][FP64_SIZE+1];
static qboolean pubkeys_havepriv[MAX_PUBKEYS];
static char pubkeys_priv_fp64[MAX_PUBKEYS][FP64_SIZE+1];
static char challenge_append[1400];
static size_t challenge_append_length;

static int keygen_i = -1;
static char keygen_buf[8192];

#define MAX_CRYPTOCONNECTS 16
#define CRYPTOCONNECT_NONE 0
#define CRYPTOCONNECT_PRECONNECT 1
#define CRYPTOCONNECT_CONNECT 2
#define CRYPTOCONNECT_RECONNECT 3
#define CRYPTOCONNECT_DUPLICATE 4
00457 typedef struct server_cryptoconnect_s
{
      double lasttime;
      lhnetaddress_t address;
      crypto_t crypto;
      int next_step;
}
server_cryptoconnect_t;
static server_cryptoconnect_t cryptoconnects[MAX_CRYPTOCONNECTS];

static int cdata_id = 0;
00468 typedef struct
{
      d0_blind_id_t *id;
      int s, c;
      int next_step;
      char challenge[2048];
      char wantserver_idfp[FP64_SIZE+1];
      qboolean wantserver_aes;
      int cdata_id;
}
crypto_data_t;

// crypto specific helpers
#define CDATA ((crypto_data_t *) crypto->data)
#define MAKE_CDATA if(!crypto->data) crypto->data = Z_Malloc(sizeof(crypto_data_t))
#define CLEAR_CDATA if(crypto->data) { if(CDATA->id) qd0_blind_id_free(CDATA->id); Z_Free(crypto->data); } crypto->data = NULL

static crypto_t *Crypto_ServerFindInstance(lhnetaddress_t *peeraddress, qboolean allow_create)
{
      crypto_t *crypto; 
      int i, best;

      if(!d0_blind_id_dll)
            return NULL; // no support

      for(i = 0; i < MAX_CRYPTOCONNECTS; ++i)
            if(LHNETADDRESS_Compare(peeraddress, &cryptoconnects[i].address))
                  break;
      if(i < MAX_CRYPTOCONNECTS && (allow_create || cryptoconnects[i].crypto.data))
      {
            crypto = &cryptoconnects[i].crypto;
            cryptoconnects[i].lasttime = realtime;
            return crypto;
      }
      if(!allow_create)
            return NULL;
      best = 0;
      for(i = 1; i < MAX_CRYPTOCONNECTS; ++i)
            if(cryptoconnects[i].lasttime < cryptoconnects[best].lasttime)
                  best = i;
      crypto = &cryptoconnects[best].crypto;
      cryptoconnects[best].lasttime = realtime;
      memcpy(&cryptoconnects[best].address, peeraddress, sizeof(cryptoconnects[best].address));
      CLEAR_CDATA;
      return crypto;
}

qboolean Crypto_ServerFinishInstance(crypto_t *out, crypto_t *crypto)
{
      // no check needed here (returned pointers are only used in prefilled fields)
      if(!crypto || !crypto->authenticated)
      {
            Con_Printf("Passed an invalid crypto connect instance\n");
            memset(out, 0, sizeof(*out));
            return false;
      }
      CLEAR_CDATA;
      memcpy(out, crypto, sizeof(*out));
      memset(crypto, 0, sizeof(crypto));
      return true;
}

crypto_t *Crypto_ServerGetInstance(lhnetaddress_t *peeraddress)
{
      // no check needed here (returned pointers are only used in prefilled fields)
      return Crypto_ServerFindInstance(peeraddress, false);
}

00536 typedef struct crypto_storedhostkey_s
{
      struct crypto_storedhostkey_s *next;
      lhnetaddress_t addr;
      int keyid;
      char idfp[FP64_SIZE+1];
      int aeslevel;
}
crypto_storedhostkey_t;
static crypto_storedhostkey_t *crypto_storedhostkey_hashtable[CRYPTO_HOSTKEY_HASHSIZE];

static void Crypto_InitHostKeys(void)
{
      int i;
      for(i = 0; i < CRYPTO_HOSTKEY_HASHSIZE; ++i)
            crypto_storedhostkey_hashtable[i] = NULL;
}

static void Crypto_ClearHostKeys(void)
{
      int i;
      crypto_storedhostkey_t *hk, *hkn;
      for(i = 0; i < CRYPTO_HOSTKEY_HASHSIZE; ++i)
      {
            for(hk = crypto_storedhostkey_hashtable[i]; hk; hk = hkn)
            {
                  hkn = hk->next;
                  Z_Free(hk);
            }
            crypto_storedhostkey_hashtable[i] = NULL;
      }
}

static qboolean Crypto_ClearHostKey(lhnetaddress_t *peeraddress)
{
      char buf[128];
      int hashindex;
      crypto_storedhostkey_t **hkp;
      qboolean found = false;

      LHNETADDRESS_ToString(peeraddress, buf, sizeof(buf), 1);
      hashindex = CRC_Block((const unsigned char *) buf, strlen(buf)) % CRYPTO_HOSTKEY_HASHSIZE;
      for(hkp = &crypto_storedhostkey_hashtable[hashindex]; *hkp && LHNETADDRESS_Compare(&((*hkp)->addr), peeraddress); hkp = &((*hkp)->next));

      if(*hkp)
      {
            crypto_storedhostkey_t *hk = *hkp;
            *hkp = hk->next;
            Z_Free(hk);
            found = true;
      }

      return found;
}

static void Crypto_StoreHostKey(lhnetaddress_t *peeraddress, const char *keystring, qboolean complain)
{
      char buf[128];
      int hashindex;
      crypto_storedhostkey_t *hk;
      int keyid;
      char idfp[FP64_SIZE+1];
      int aeslevel;

      if(!d0_blind_id_dll)
            return;
      
      // syntax of keystring:
      // aeslevel id@key id@key ...

      if(!*keystring)
            return;
      aeslevel = bound(0, *keystring - '0', 3);
      while(*keystring && *keystring != ' ')
            ++keystring;

      keyid = -1;
      while(*keystring && keyid < 0)
      {
            // id@key
            const char *idstart, *idend, *keystart, *keyend;
            ++keystring; // skip the space
            idstart = keystring;
            while(*keystring && *keystring != ' ' && *keystring != '@')
                  ++keystring;
            idend = keystring;
            if(!*keystring)
                  break;
            ++keystring;
            keystart = keystring;
            while(*keystring && *keystring != ' ')
                  ++keystring;
            keyend = keystring;

            if(idend - idstart == FP64_SIZE && keyend - keystart == FP64_SIZE)
            {
                  for(keyid = 0; keyid < MAX_PUBKEYS; ++keyid)
                        if(pubkeys[keyid])
                              if(!memcmp(pubkeys_fp64[keyid], keystart, FP64_SIZE))
                              {
                                    memcpy(idfp, idstart, FP64_SIZE);
                                    idfp[FP64_SIZE] = 0;
                                    break;
                              }
                  if(keyid >= MAX_PUBKEYS)
                        keyid = -1;
            }
      }

      if(keyid < 0)
            return;

      LHNETADDRESS_ToString(peeraddress, buf, sizeof(buf), 1);
      hashindex = CRC_Block((const unsigned char *) buf, strlen(buf)) % CRYPTO_HOSTKEY_HASHSIZE;
      for(hk = crypto_storedhostkey_hashtable[hashindex]; hk && LHNETADDRESS_Compare(&hk->addr, peeraddress); hk = hk->next);

      if(hk)
      {
            if(complain)
            {
                  if(hk->keyid != keyid || memcmp(hk->idfp, idfp, FP64_SIZE+1))
                        Con_Printf("Server %s tried to change the host key to a value not in the host cache. Connecting to it will fail. To accept the new host key, do crypto_hostkey_clear %s\n", buf, buf);
                  if(hk->aeslevel > aeslevel)
                        Con_Printf("Server %s tried to reduce encryption status, not accepted. Connecting to it will fail. To accept, do crypto_hostkey_clear %s\n", buf, buf);
            }
            hk->aeslevel = max(aeslevel, hk->aeslevel);
            return;
      }

      // great, we did NOT have it yet
      hk = (crypto_storedhostkey_t *) Z_Malloc(sizeof(*hk));
      memcpy(&hk->addr, peeraddress, sizeof(hk->addr));
      hk->keyid = keyid;
      memcpy(hk->idfp, idfp, FP64_SIZE+1);
      hk->next = crypto_storedhostkey_hashtable[hashindex];
      hk->aeslevel = aeslevel;
      crypto_storedhostkey_hashtable[hashindex] = hk;
}

qboolean Crypto_RetrieveHostKey(lhnetaddress_t *peeraddress, int *keyid, char *keyfp, size_t keyfplen, char *idfp, size_t idfplen, int *aeslevel)
{
      char buf[128];
      int hashindex;
      crypto_storedhostkey_t *hk;

      if(!d0_blind_id_dll)
            return false;

      LHNETADDRESS_ToString(peeraddress, buf, sizeof(buf), 1);
      hashindex = CRC_Block((const unsigned char *) buf, strlen(buf)) % CRYPTO_HOSTKEY_HASHSIZE;
      for(hk = crypto_storedhostkey_hashtable[hashindex]; hk && LHNETADDRESS_Compare(&hk->addr, peeraddress); hk = hk->next);

      if(!hk)
            return false;

      if(keyid)
            *keyid = hk->keyid;
      if(keyfp)
            strlcpy(keyfp, pubkeys_fp64[hk->keyid], keyfplen);
      if(idfp)
            strlcpy(idfp, hk->idfp, idfplen);
      if(aeslevel)
            *aeslevel = hk->aeslevel;

      return true;
}
int Crypto_RetrieveLocalKey(int keyid, char *keyfp, size_t keyfplen, char *idfp, size_t idfplen) // return value: -1 if more to come, +1 if valid, 0 if end of list
{
      if(keyid < 0 || keyid >= MAX_PUBKEYS)
            return 0;
      if(keyfp)
            *keyfp = 0;
      if(idfp)
            *idfp = 0;
      if(!pubkeys[keyid])
            return -1;
      if(keyfp)
            strlcpy(keyfp, pubkeys_fp64[keyid], keyfplen);
      if(idfp)
            if(pubkeys_havepriv[keyid])
                  strlcpy(idfp, pubkeys_priv_fp64[keyid], keyfplen);
      return 1;
}
// end

// init/shutdown code
static void Crypto_BuildChallengeAppend(void)
{
      char *p, *lengthptr, *startptr;
      size_t n;
      int i;
      p = challenge_append;
      n = sizeof(challenge_append);
      Crypto_UnLittleLong(p, PROTOCOL_VLEN);
      p += 4;
      n -= 4;
      lengthptr = p;
      Crypto_UnLittleLong(p, 0);
      p += 4;
      n -= 4;
      Crypto_UnLittleLong(p, PROTOCOL_D0_BLIND_ID);
      p += 4;
      n -= 4;
      startptr = p;
      for(i = 0; i < MAX_PUBKEYS; ++i)
            if(pubkeys_havepriv[i])
                  PutWithNul(&p, &n, pubkeys_fp64[i]);
      PutWithNul(&p, &n, "");
      for(i = 0; i < MAX_PUBKEYS; ++i)
            if(!pubkeys_havepriv[i] && pubkeys[i])
                  PutWithNul(&p, &n, pubkeys_fp64[i]);
      Crypto_UnLittleLong(lengthptr, p - startptr);
      challenge_append_length = p - challenge_append;
}

static void Crypto_LoadKeys(void)
{
      char buf[8192];
      size_t len, len2;
      int i;

      // load keys
      // note: we are just a CLIENT
      // so we load:
      //   PUBLIC KEYS to accept (including modulus)
      //   PRIVATE KEY of user

      crypto_idstring = NULL;
      dpsnprintf(crypto_idstring_buf, sizeof(crypto_idstring_buf), "%d", d0_rijndael_dll ? crypto_aeslevel.integer : 0);
      for(i = 0; i < MAX_PUBKEYS; ++i)
      {
            memset(pubkeys_fp64[i], 0, sizeof(pubkeys_fp64[i]));
            memset(pubkeys_priv_fp64[i], 0, sizeof(pubkeys_fp64[i]));
            pubkeys_havepriv[i] = false;
            len = Crypto_LoadFile(va("key_%d.d0pk", i), buf, sizeof(buf));
            if((pubkeys[i] = Crypto_ReadPublicKey(buf, len)))
            {
                  len2 = FP64_SIZE;
                  if(qd0_blind_id_fingerprint64_public_key(pubkeys[i], pubkeys_fp64[i], &len2)) // keeps final NUL
                  {
                        Con_Printf("Loaded public key key_%d.d0pk (fingerprint: %s)\n", i, pubkeys_fp64[i]);
                        len = Crypto_LoadFile(va("key_%d.d0si", i), buf, sizeof(buf));
                        if(len)
                        {
                              if(Crypto_AddPrivateKey(pubkeys[i], buf, len))
                              {
                                    len2 = FP64_SIZE;
                                    if(qd0_blind_id_fingerprint64_public_id(pubkeys[i], pubkeys_priv_fp64[i], &len2)) // keeps final NUL
                                    {
                                          Con_Printf("Loaded private ID key_%d.d0si for key_%d.d0pk (fingerprint: %s)\n", i, i, pubkeys_priv_fp64[i]);
                                          pubkeys_havepriv[i] = true;
                                          strlcat(crypto_idstring_buf, va(" %s@%s", pubkeys_priv_fp64[i], pubkeys_fp64[i]), sizeof(crypto_idstring_buf));
                                    }
                                    else
                                    {
                                          // can't really happen
                                          // but nothing leaked here
                                    }
                              }
                        }
                  }
                  else
                  {
                        // can't really happen
                        qd0_blind_id_free(pubkeys[i]);
                        pubkeys[i] = NULL;
                  }
            }
      }
      crypto_idstring = crypto_idstring_buf;

      keygen_i = -1;
      Crypto_BuildChallengeAppend();

      // find a good prefix length for all the keys we know (yes, algorithm is not perfect yet, may yield too long prefix length)
      crypto_keyfp_recommended_length = 0;
      memset(buf+256, 0, MAX_PUBKEYS + MAX_PUBKEYS);
      while(crypto_keyfp_recommended_length < FP64_SIZE)
      {
            memset(buf, 0, 256);
            for(i = 0; i < MAX_PUBKEYS; ++i)
                  if(pubkeys[i])
                  {
                        if(!buf[256 + i])
                              ++buf[(unsigned char) pubkeys_fp64[i][crypto_keyfp_recommended_length]];
                        if(pubkeys_havepriv[i])
                              if(!buf[256 + MAX_PUBKEYS + i])
                                    ++buf[(unsigned char) pubkeys_priv_fp64[i][crypto_keyfp_recommended_length]];
                  }
            for(i = 0; i < MAX_PUBKEYS; ++i)
                  if(pubkeys[i])
                  {
                        if(!buf[256 + i])
                              if(buf[(unsigned char) pubkeys_fp64[i][crypto_keyfp_recommended_length]] < 2)
                                    buf[256 + i] = 1;
                        if(pubkeys_havepriv[i])
                              if(!buf[256 + MAX_PUBKEYS + i])
                                    if(buf[(unsigned char) pubkeys_priv_fp64[i][crypto_keyfp_recommended_length]] < 2)
                                          buf[256 + MAX_PUBKEYS + i] = 1;
                  }
            ++crypto_keyfp_recommended_length;
            for(i = 0; i < MAX_PUBKEYS; ++i)
                  if(pubkeys[i])
                  {
                        if(!buf[256 + i])
                              break;
                        if(pubkeys_havepriv[i])
                              if(!buf[256 + MAX_PUBKEYS + i])
                                    break;
                  }
            if(i >= MAX_PUBKEYS)
                  break;
      }
      if(crypto_keyfp_recommended_length < 7)
            crypto_keyfp_recommended_length = 7;
}

static void Crypto_UnloadKeys(void)
{
      int i;
      keygen_i = -1;
      for(i = 0; i < MAX_PUBKEYS; ++i)
      {
            if(pubkeys[i])
                  qd0_blind_id_free(pubkeys[i]);
            pubkeys[i] = NULL;
            pubkeys_havepriv[i] = false;
            memset(pubkeys_fp64[i], 0, sizeof(pubkeys_fp64[i]));
            memset(pubkeys_priv_fp64[i], 0, sizeof(pubkeys_fp64[i]));
            challenge_append_length = 0;
      }
      crypto_idstring = NULL;
}

void Crypto_Shutdown(void)
{
      crypto_t *crypto;
      int i;

      Crypto_Rijndael_CloseLibrary();

      if(d0_blind_id_dll)
      {
            // free memory
            for(i = 0; i < MAX_CRYPTOCONNECTS; ++i)
            {
                  crypto = &cryptoconnects[i].crypto;
                  CLEAR_CDATA;
            }
            memset(cryptoconnects, 0, sizeof(cryptoconnects));
            crypto = &cls.crypto;
            CLEAR_CDATA;

            Crypto_UnloadKeys();

            qd0_blind_id_SHUTDOWN();

            Crypto_CloseLibrary();
      }
}

void Crypto_Init(void)
{
      if(!Crypto_OpenLibrary())
            return;

      if(!qd0_blind_id_INITIALIZE())
      {
            Crypto_Rijndael_CloseLibrary();
            Crypto_CloseLibrary();
            Con_Printf("libd0_blind_id initialization FAILED, cryptography support has been disabled\n");
            return;
      }

      Crypto_Rijndael_OpenLibrary(); // if this fails, it's uncritical

      Crypto_InitHostKeys();
      Crypto_LoadKeys();
}
// end

// keygen code
static void Crypto_KeyGen_Finished(int code, size_t length_received, unsigned char *buffer, void *cbdata)
{
      const char *p[1];
      size_t l[1];
      static char buf[8192];
      static char buf2[8192];
      size_t bufsize, buf2size;
      qfile_t *f = NULL;
      d0_blind_id_t *ctx, *ctx2;
      D0_BOOL status;
      size_t len2;

      if(!d0_blind_id_dll)
      {
            Con_Print("libd0_blind_id DLL not found, this command is inactive.\n");
            keygen_i = -1;
            return;
      }

      if(keygen_i >= MAX_PUBKEYS || !pubkeys[keygen_i])
      {
            Con_Printf("overflow of keygen_i\n");
            keygen_i = -1;
            return;
      }
      if(keygen_i < 0)
      {
            Con_Printf("Unexpected response from keygen server:\n");
            Com_HexDumpToConsole(buffer, length_received);
            return;
      }
      if(!Crypto_ParsePack((const char *) buffer, length_received, FOURCC_D0IR, p, l, 1))
      {
            if(length_received >= 5 && Crypto_LittleLong((const char *) buffer) == FOURCC_D0ER)
            {
                  Con_Printf("Error response from keygen server: %.*s\n", (int)(length_received - 5), buffer + 5);
            }
            else
            {
                  Con_Printf("Invalid response from keygen server:\n");
                  Com_HexDumpToConsole(buffer, length_received);
            }
            keygen_i = -1;
            return;
      }
      if(!qd0_blind_id_finish_private_id_request(pubkeys[keygen_i], p[0], l[0]))
      {
            Con_Printf("d0_blind_id_finish_private_id_request failed\n");
            keygen_i = -1;
            return;
      }

      // verify the key we just got (just in case)
      ctx = qd0_blind_id_new();
      if(!ctx)
      {
            Con_Printf("d0_blind_id_new failed\n");
            keygen_i = -1;
            return;
      }
      ctx2 = qd0_blind_id_new();
      if(!ctx2)
      {
            Con_Printf("d0_blind_id_new failed\n");
            qd0_blind_id_free(ctx);
            keygen_i = -1;
            return;
      }
      if(!qd0_blind_id_copy(ctx, pubkeys[keygen_i]))
      {
            Con_Printf("d0_blind_id_copy failed\n");
            qd0_blind_id_free(ctx);
            qd0_blind_id_free(ctx2);
            keygen_i = -1;
            return;
      }
      if(!qd0_blind_id_copy(ctx2, pubkeys[keygen_i]))
      {
            Con_Printf("d0_blind_id_copy failed\n");
            qd0_blind_id_free(ctx);
            qd0_blind_id_free(ctx2);
            keygen_i = -1;
            return;
      }
      bufsize = sizeof(buf);
      if(!qd0_blind_id_authenticate_with_private_id_start(ctx, 1, 1, "hello world", 11, buf, &bufsize))
      {
            Con_Printf("d0_blind_id_authenticate_with_private_id_start failed\n");
            qd0_blind_id_free(ctx);
            qd0_blind_id_free(ctx2);
            keygen_i = -1;
            return;
      }
      buf2size = sizeof(buf2);
      if(!qd0_blind_id_authenticate_with_private_id_challenge(ctx2, 1, 1, buf, bufsize, buf2, &buf2size, &status) || !status)
      {
            Con_Printf("d0_blind_id_authenticate_with_private_id_challenge failed (server does not have the requested private key)\n");
            qd0_blind_id_free(ctx);
            qd0_blind_id_free(ctx2);
            keygen_i = -1;
            return;
      }
      bufsize = sizeof(buf);
      if(!qd0_blind_id_authenticate_with_private_id_response(ctx, buf2, buf2size, buf, &bufsize))
      {
            Con_Printf("d0_blind_id_authenticate_with_private_id_response failed\n");
            qd0_blind_id_free(ctx);
            qd0_blind_id_free(ctx2);
            keygen_i = -1;
            return;
      }
      buf2size = sizeof(buf2);
      if(!qd0_blind_id_authenticate_with_private_id_verify(ctx2, buf, bufsize, buf2, &buf2size, &status) || !status)
      {
            Con_Printf("d0_blind_id_authenticate_with_private_id_verify failed (server does not have the requested private key)\n");
            qd0_blind_id_free(ctx);
            qd0_blind_id_free(ctx2);
            keygen_i = -1;
            return;
      }
      qd0_blind_id_free(ctx);
      qd0_blind_id_free(ctx2);

      // we have a valid key now!
      // make the rest of crypto.c know that
      len2 = FP64_SIZE;
      if(qd0_blind_id_fingerprint64_public_id(pubkeys[keygen_i], pubkeys_priv_fp64[keygen_i], &len2)) // keeps final NUL
      {
            Con_Printf("Received private ID key_%d.d0pk (fingerprint: %s)\n", keygen_i, pubkeys_priv_fp64[keygen_i]);
            pubkeys_havepriv[keygen_i] = true;
            strlcat(crypto_idstring_buf, va(" %s@%s", pubkeys_priv_fp64[keygen_i], pubkeys_fp64[keygen_i]), sizeof(crypto_idstring_buf));
            crypto_idstring = crypto_idstring_buf;
            Crypto_BuildChallengeAppend();
      }
      // write the key to disk
      p[0] = buf;
      l[0] = sizeof(buf);
      if(!qd0_blind_id_write_private_id(pubkeys[keygen_i], buf, &l[0]))
      {
            Con_Printf("d0_blind_id_write_private_id failed\n");
            keygen_i = -1;
            return;
      }
      if(!(buf2size = Crypto_UnParsePack(buf2, sizeof(buf2), FOURCC_D0SI, p, l, 1)))
      {
            Con_Printf("Crypto_UnParsePack failed\n");
            keygen_i = -1;
            return;
      }

      if(*fs_userdir)
      {
            FS_CreatePath(va("%skey_%d.d0si", fs_userdir, keygen_i));
            f = FS_SysOpen(va("%skey_%d.d0si", fs_userdir, keygen_i), "wb", false);
      }
      if(!f)
      {
            FS_CreatePath(va("%skey_%d.d0si", fs_basedir, keygen_i));
            f = FS_SysOpen(va("%skey_%d.d0si", fs_basedir, keygen_i), "wb", false);
      }
      if(!f)
      {
            Con_Printf("Cannot open key_%d.d0si\n", keygen_i);
            keygen_i = -1;
            return;
      }
      FS_Write(f, buf2, buf2size);
      FS_Close(f);

      Con_Printf("Saved to key_%d.d0si\n", keygen_i);
      keygen_i = -1;
}

static void Crypto_KeyGen_f(void)
{
      int i;
      const char *p[1];
      size_t l[1];
      static char buf[8192];
      static char buf2[8192];
      size_t buf2l, buf2pos;
      if(!d0_blind_id_dll)
      {
            Con_Print("libd0_blind_id DLL not found, this command is inactive.\n");
            return;
      }
      if(Cmd_Argc() != 3)
      {
            Con_Printf("usage:\n%s id url\n", Cmd_Argv(0));
            return;
      }
      i = atoi(Cmd_Argv(1));
      if(!pubkeys[i])
      {
            Con_Printf("there is no public key %d\n", i);
            return;
      }
      if(pubkeys_havepriv[i])
      {
            Con_Printf("there is already a private key for %d\n", i);
            return;
      }
      if(keygen_i >= 0)
      {
            Con_Printf("there is already a keygen run on the way\n");
            return;
      }
      keygen_i = i;
      if(!qd0_blind_id_generate_private_id_start(pubkeys[keygen_i]))
      {
            Con_Printf("d0_blind_id_start failed\n");
            keygen_i = -1;
            return;
      }
      p[0] = buf;
      l[0] = sizeof(buf);
      if(!qd0_blind_id_generate_private_id_request(pubkeys[keygen_i], buf, &l[0]))
      {
            Con_Printf("d0_blind_id_generate_private_id_request failed\n");
            keygen_i = -1;
            return;
      }
      buf2pos = strlen(Cmd_Argv(2));
      memcpy(buf2, Cmd_Argv(2), buf2pos);
      if(!(buf2l = Crypto_UnParsePack(buf2 + buf2pos, sizeof(buf2) - buf2pos - 1, FOURCC_D0IQ, p, l, 1)))
      {
            Con_Printf("Crypto_UnParsePack failed\n");
            keygen_i = -1;
            return;
      }
      if(!(buf2l = base64_encode((unsigned char *) (buf2 + buf2pos), buf2l, sizeof(buf2) - buf2pos - 1)))
      {
            Con_Printf("base64_encode failed\n");
            keygen_i = -1;
            return;
      }
      buf2l += buf2pos;
      buf[buf2l] = 0;
      if(!Curl_Begin_ToMemory(buf2, 0, (unsigned char *) keygen_buf, sizeof(keygen_buf), Crypto_KeyGen_Finished, NULL))
      {
            Con_Printf("curl failed\n");
            keygen_i = -1;
            return;
      }
      Con_Printf("key generation in progress\n");
}
// end

// console commands
static void Crypto_Reload_f(void)
{
      Crypto_ClearHostKeys();
      Crypto_UnloadKeys();
      Crypto_LoadKeys();
}

static void Crypto_Keys_f(void)
{
      int i;
      if(!d0_blind_id_dll)
      {
            Con_Print("libd0_blind_id DLL not found, this command is inactive.\n");
            return;
      }
      for(i = 0; i < MAX_PUBKEYS; ++i)
      {
            if(pubkeys[i])
            {
                  Con_Printf("%2d: public key key_%d.d0pk (fingerprint: %s)\n", i, i, pubkeys_fp64[i]);
                  if(pubkeys_havepriv[i])
                        Con_Printf("    private ID key_%d.d0si (fingerprint: %s)\n", i, pubkeys_priv_fp64[i]);
            }
      }
}

static void Crypto_HostKeys_f(void)
{
      int i;
      crypto_storedhostkey_t *hk;
      char buf[128];

      if(!d0_blind_id_dll)
      {
            Con_Print("libd0_blind_id DLL not found, this command is inactive.\n");
            return;
      }
      for(i = 0; i < CRYPTO_HOSTKEY_HASHSIZE; ++i)
      {
            for(hk = crypto_storedhostkey_hashtable[i]; hk; hk = hk->next)
            {
                  LHNETADDRESS_ToString(&hk->addr, buf, sizeof(buf), 1);
                  Con_Printf("%d %s@%.*s %s\n",
                              hk->aeslevel,
                              hk->idfp,
                              crypto_keyfp_recommended_length, pubkeys_fp64[hk->keyid],
                              buf);
            }
      }
}

static void Crypto_HostKey_Clear_f(void)
{
      lhnetaddress_t addr;
      int i;

      if(!d0_blind_id_dll)
      {
            Con_Print("libd0_blind_id DLL not found, this command is inactive.\n");
            return;
      }

      for(i = 1; i < Cmd_Argc(); ++i)
      {
            LHNETADDRESS_FromString(&addr, Cmd_Argv(i), 26000);
            if(Crypto_ClearHostKey(&addr))
            {
                  Con_Printf("cleared host key for %s\n", Cmd_Argv(i));
            }
      }
}

void Crypto_Init_Commands(void)
{
      if(d0_blind_id_dll)
      {
            Cmd_AddCommand("crypto_reload", Crypto_Reload_f, "reloads cryptographic keys");
            Cmd_AddCommand("crypto_keygen", Crypto_KeyGen_f, "generates and saves a cryptographic key");
            Cmd_AddCommand("crypto_keys", Crypto_Keys_f, "lists the loaded keys");
            Cmd_AddCommand("crypto_hostkeys", Crypto_HostKeys_f, "lists the cached host keys");
            Cmd_AddCommand("crypto_hostkey_clear", Crypto_HostKey_Clear_f, "clears a cached host key");
            Cvar_RegisterVariable(&crypto_developer);
            if(d0_rijndael_dll)
                  Cvar_RegisterVariable(&crypto_aeslevel);
            else
                  crypto_aeslevel.integer = 0; // make sure
            Cvar_RegisterVariable(&crypto_servercpupercent);
            Cvar_RegisterVariable(&crypto_servercpumaxtime);
            Cvar_RegisterVariable(&crypto_servercpudebug);
      }
}
// end

// AES encryption
static void aescpy(unsigned char *key, const unsigned char *iv, unsigned char *dst, const unsigned char *src, size_t len)
{
      const unsigned char *xorpos = iv;
      unsigned char xorbuf[16];
      unsigned long rk[D0_RIJNDAEL_RKLENGTH(DHKEY_SIZE * 8)];
      size_t i;
      qd0_rijndael_setup_encrypt(rk, key, DHKEY_SIZE * 8);
      while(len > 16)
      {
            for(i = 0; i < 16; ++i)
                  xorbuf[i] = src[i] ^ xorpos[i];
            qd0_rijndael_encrypt(rk, D0_RIJNDAEL_NROUNDS(DHKEY_SIZE * 8), xorbuf, dst);
            xorpos = dst;
            len -= 16;
            src += 16;
            dst += 16;
      }
      if(len > 0)
      {
            for(i = 0; i < len; ++i)
                  xorbuf[i] = src[i] ^ xorpos[i];
            for(; i < 16; ++i)
                  xorbuf[i] = xorpos[i];
            qd0_rijndael_encrypt(rk, D0_RIJNDAEL_NROUNDS(DHKEY_SIZE * 8), xorbuf, dst);
      }
}
static void seacpy(unsigned char *key, const unsigned char *iv, unsigned char *dst, const unsigned char *src, size_t len)
{
      const unsigned char *xorpos = iv;
      unsigned char xorbuf[16];
      unsigned long rk[D0_RIJNDAEL_RKLENGTH(DHKEY_SIZE * 8)];
      size_t i;
      qd0_rijndael_setup_decrypt(rk, key, DHKEY_SIZE * 8);
      while(len > 16)
      {
            qd0_rijndael_decrypt(rk, D0_RIJNDAEL_NROUNDS(DHKEY_SIZE * 8), src, xorbuf);
            for(i = 0; i < 16; ++i)
                  dst[i] = xorbuf[i] ^ xorpos[i];
            xorpos = src;
            len -= 16;
            src += 16;
            dst += 16;
      }
      if(len > 0)
      {
            qd0_rijndael_decrypt(rk, D0_RIJNDAEL_NROUNDS(DHKEY_SIZE * 8), src, xorbuf);
            for(i = 0; i < len; ++i)
                  dst[i] = xorbuf[i] ^ xorpos[i];
      }
}

// NOTE: we MUST avoid the following begins of the packet:
//   1. 0xFF, 0xFF, 0xFF, 0xFF
//   2. 0x80, 0x00, length/256, length%256
// this luckily does NOT affect AES mode, where the first byte always is in the range from 0x00 to 0x0F
const void *Crypto_EncryptPacket(crypto_t *crypto, const void *data_src, size_t len_src, void *data_dst, size_t *len_dst, size_t len)
{
      unsigned char h[32];
      int i;
      if(crypto->authenticated)
      {
            if(crypto->use_aes)
            {
                  // AES packet = 1 byte length overhead, 15 bytes from HMAC-SHA-256, data, 0..15 bytes padding
                  // 15 bytes HMAC-SHA-256 (112bit) suffice as the attacker can't do more than forge a random-looking packet
                  // HMAC is needed to not leak information about packet content
                  if(developer_networking.integer)
                  {
                        Con_Print("To be encrypted:\n");
                        Com_HexDumpToConsole((const unsigned char *) data_src, len_src);
                  }
                  if(len_src + 32 > len || !HMAC_SHA256_32BYTES(h, (const unsigned char *) data_src, len_src, crypto->dhkey, DHKEY_SIZE))
                  {
                        Con_Printf("Crypto_EncryptPacket failed (not enough space: %d bytes in, %d bytes out)\n", (int) len_src, (int) len);
                        return NULL;
                  }
                  *len_dst = ((len_src + 15) / 16) * 16 + 16; // add 16 for HMAC, then round to 16-size for AES
                  ((unsigned char *) data_dst)[0] = *len_dst - len_src;
                  memcpy(((unsigned char *) data_dst)+1, h, 15);
                  aescpy(crypto->dhkey, (const unsigned char *) data_dst, ((unsigned char *) data_dst) + 16, (const unsigned char *) data_src, len_src);
                  //                    IV                                dst                                src                               len
            }
            else
            {
                  // HMAC packet = 16 bytes HMAC-SHA-256 (truncated to 128 bits), data
                  if(len_src + 16 > len || !HMAC_SHA256_32BYTES(h, (const unsigned char *) data_src, len_src, crypto->dhkey, DHKEY_SIZE))
                  {
                        Con_Printf("Crypto_EncryptPacket failed (not enough space: %d bytes in, %d bytes out)\n", (int) len_src, (int) len);
                        return NULL;
                  }
                  *len_dst = len_src + 16;
                  memcpy(data_dst, h, 16);
                  memcpy(((unsigned char *) data_dst) + 16, (unsigned char *) data_src, len_src);

                  // handle the "avoid" conditions:
                  i = BuffBigLong((unsigned char *) data_dst);
                  if(
                        (i == (int)0xFFFFFFFF) // avoid QW control packet
                        ||
                        (i == (int)0x80000000 + (int)*len_dst) // avoid NQ control packet
                  )
                        *(unsigned char *)data_dst ^= 0x80; // this will ALWAYS fix it
            }
            return data_dst;
      }
      else
      {
            *len_dst = len_src;
            return data_src;
      }
}

const void *Crypto_DecryptPacket(crypto_t *crypto, const void *data_src, size_t len_src, void *data_dst, size_t *len_dst, size_t len)
{
      unsigned char h[32];
      int i;

      // silently handle non-crypto packets
      i = BuffBigLong((unsigned char *) data_src);
      if(
            (i == (int)0xFFFFFFFF) // avoid QW control packet
            ||
            (i == (int)0x80000000 + (int)len_src) // avoid NQ control packet
      )
            return NULL;

      if(crypto->authenticated)
      {
            if(crypto->use_aes)
            {
                  if(len_src < 16 || ((len_src - 16) % 16))
                  {
                        Con_Printf("Crypto_DecryptPacket failed (not enough space: %d bytes in, %d bytes out)\n", (int) len_src, (int) len);
                        return NULL;
                  }
                  *len_dst = len_src - ((unsigned char *) data_src)[0];
                  if(len < *len_dst || *len_dst > len_src - 16)
                  {
                        Con_Printf("Crypto_DecryptPacket failed (not enough space: %d bytes in, %d->%d bytes out)\n", (int) len_src, (int) *len_dst, (int) len);
                        return NULL;
                  }
                  seacpy(crypto->dhkey, (unsigned char *) data_src, (unsigned char *) data_dst, ((const unsigned char *) data_src) + 16, *len_dst);
                  //                    IV                          dst                         src                                      len
                  if(!HMAC_SHA256_32BYTES(h, (const unsigned char *) data_dst, *len_dst, crypto->dhkey, DHKEY_SIZE))
                  {
                        Con_Printf("HMAC fail\n");
                        return NULL;
                  }
                  if(memcmp(((const unsigned char *) data_src)+1, h, 15)) // ignore first byte, used for length
                  {
                        Con_Printf("HMAC mismatch\n");
                        return NULL;
                  }
                  if(developer_networking.integer)
                  {
                        Con_Print("Decrypted:\n");
                        Com_HexDumpToConsole((const unsigned char *) data_dst, *len_dst);
                  }
                  return data_dst; // no need to copy
            }
            else
            {
                  if(len_src < 16)
                  {
                        Con_Printf("Crypto_DecryptPacket failed (not enough space: %d bytes in, %d bytes out)\n", (int) len_src, (int) len);
                        return NULL;
                  }
                  *len_dst = len_src - 16;
                  if(len < *len_dst)
                  {
                        Con_Printf("Crypto_DecryptPacket failed (not enough space: %d bytes in, %d->%d bytes out)\n", (int) len_src, (int) *len_dst, (int) len);
                        return NULL;
                  }
                  //memcpy(data_dst, data_src + 16, *len_dst);
                  if(!HMAC_SHA256_32BYTES(h, ((const unsigned char *) data_src) + 16, *len_dst, crypto->dhkey, DHKEY_SIZE))
                  {
                        Con_Printf("HMAC fail\n");
                        Com_HexDumpToConsole((const unsigned char *) data_src, len_src);
                        return NULL;
                  }

                  if(memcmp((const unsigned char *) data_src, h, 16)) // ignore first byte, used for length
                  {
                        // undo the "avoid conditions"
                        if(
                                    (i == (int)0x7FFFFFFF) // avoided QW control packet
                                    ||
                                    (i == (int)0x00000000 + (int)len_src) // avoided NQ control packet
                          )
                        {
                              // do the avoidance on the hash too
                              h[0] ^= 0x80;
                              if(memcmp((const unsigned char *) data_src, h, 16)) // ignore first byte, used for length
                              {
                                    Con_Printf("HMAC mismatch\n");
                                    Com_HexDumpToConsole((const unsigned char *) data_src, len_src);
                                    return NULL;
                              }
                        }
                        else
                        {
                              Con_Printf("HMAC mismatch\n");
                              Com_HexDumpToConsole((const unsigned char *) data_src, len_src);
                              return NULL;
                        }
                  }
                  return ((const unsigned char *) data_src) + 16; // no need to copy, so data_dst is not used
            }
      }
      else
      {
            *len_dst = len_src;
            return data_src;
      }
}
// end

const char *Crypto_GetInfoResponseDataString(void)
{
      crypto_idstring_buf[0] = '0' + crypto_aeslevel.integer;
      return crypto_idstring;
}

// network protocol
qboolean Crypto_ServerAppendToChallenge(const char *data_in, size_t len_in, char *data_out, size_t *len_out, size_t maxlen_out)
{
      // cheap op, all is precomputed
      if(!d0_blind_id_dll)
            return false; // no support
      // append challenge
      if(maxlen_out <= *len_out + challenge_append_length)
            return false;
      memcpy(data_out + *len_out, challenge_append, challenge_append_length);
      *len_out += challenge_append_length;
      return false;
}

static int Crypto_ServerError(char *data_out, size_t *len_out, const char *msg, const char *msg_client)
{
      if(!msg_client)
            msg_client = msg;
      Con_DPrintf("rejecting client: %s\n", msg);
      if(*msg_client)
            dpsnprintf(data_out, *len_out, "reject %s", msg_client);
      *len_out = strlen(data_out);
      return CRYPTO_DISCARD;
}

static int Crypto_SoftServerError(char *data_out, size_t *len_out, const char *msg)
{
      *len_out = 0;
      Con_DPrintf("%s\n", msg);
      return CRYPTO_DISCARD;
}

static int Crypto_ServerParsePacket_Internal(const char *data_in, size_t len_in, char *data_out, size_t *len_out, lhnetaddress_t *peeraddress)
{
      // if "connect": reject if in the middle of crypto handshake
      crypto_t *crypto = NULL;
      char *data_out_p = data_out;
      const char *string = data_in;
      int aeslevel;
      D0_BOOL aes;
      D0_BOOL status;

      if(!d0_blind_id_dll)
            return CRYPTO_NOMATCH; // no support

      if (len_in > 8 && !memcmp(string, "connect\\", 8) && d0_rijndael_dll && crypto_aeslevel.integer >= 3)
      {
            const char *s;
            int i;
            // sorry, we have to verify the challenge here to not reflect network spam

            if (!(s = SearchInfostring(string + 4, "challenge")))
                  return CRYPTO_NOMATCH; // will be later accepted if encryption was set up
            // validate the challenge
            for (i = 0;i < MAX_CHALLENGES;i++)
                  if(challenge[i].time > 0)
                        if (!LHNETADDRESS_Compare(peeraddress, &challenge[i].address) && !strcmp(challenge[i].string, s))
                              break;
            // if the challenge is not recognized, drop the packet
            if (i == MAX_CHALLENGES) // challenge mismatch is silent
                  return CRYPTO_DISCARD; // pre-challenge: rather be silent

            crypto = Crypto_ServerFindInstance(peeraddress, false);
            if(!crypto || !crypto->authenticated)
                  return Crypto_ServerError(data_out, len_out, "This server requires authentication and encryption to be supported by your client", NULL);
      }
      else if(len_in > 5 && !memcmp(string, "d0pk\\", 5) && ((LHNETADDRESS_GetAddressType(peeraddress) == LHNETADDRESSTYPE_LOOP) || sv_public.integer > -3))
      {
            const char *cnt, *s, *p;
            int id;
            int clientid = -1, serverid = -1;
            cnt = SearchInfostring(string + 4, "id");
            id = (cnt ? atoi(cnt) : -1);
            cnt = SearchInfostring(string + 4, "cnt");
            if(!cnt)
                  return CRYPTO_DISCARD; // pre-challenge: rather be silent
            GetUntilNul(&data_in, &len_in);
            if(!data_in)
                  return CRYPTO_DISCARD; // pre-challenge: rather be silent
            if(!strcmp(cnt, "0"))
            {
                  int i;
                  if (!(s = SearchInfostring(string + 4, "challenge")))
                        return CRYPTO_DISCARD; // pre-challenge: rather be silent
                  // validate the challenge
                  for (i = 0;i < MAX_CHALLENGES;i++)
                        if(challenge[i].time > 0)
                              if (!LHNETADDRESS_Compare(peeraddress, &challenge[i].address) && !strcmp(challenge[i].string, s))
                                    break;
                  // if the challenge is not recognized, drop the packet
                  if (i == MAX_CHALLENGES) // challenge mismatch is silent
                        return CRYPTO_DISCARD; // pre-challenge: rather be silent

                  if (!(s = SearchInfostring(string + 4, "aeslevel")))
                        aeslevel = 0; // not supported
                  else
                        aeslevel = bound(0, atoi(s), 3);
                  switch(bound(0, d0_rijndael_dll ? crypto_aeslevel.integer : 0, 3))
                  {
                        default: // dummy, never happens, but to make gcc happy...
                        case 0:
                              if(aeslevel >= 3)
                                    return Crypto_ServerError(data_out, len_out, "This server requires encryption to be not required (crypto_aeslevel <= 2)", NULL);
                              aes = false;
                              break;
                        case 1:
                              aes = (aeslevel >= 2);
                              break;
                        case 2:
                              aes = (aeslevel >= 1);
                              break;
                        case 3:
                              if(aeslevel <= 0)
                                    return Crypto_ServerError(data_out, len_out, "This server requires encryption to be supported (crypto_aeslevel >= 1, and d0_rijndael library must be present)", NULL);
                              aes = true;
                              break;
                  }

                  p = GetUntilNul(&data_in, &len_in);
                  if(p && *p)
                  {
                        for(i = 0; i < MAX_PUBKEYS; ++i)
                        {
                              if(pubkeys[i])
                                    if(!strcmp(p, pubkeys_fp64[i]))
                                          if(pubkeys_havepriv[i])
                                                if(serverid < 0)
                                                      serverid = i;
                        }
                        if(serverid < 0)
                              return Crypto_ServerError(data_out, len_out, "Invalid server key", NULL);
                  }
                  p = GetUntilNul(&data_in, &len_in);
                  if(p && *p)
                  {
                        for(i = 0; i < MAX_PUBKEYS; ++i)
                        {
                              if(pubkeys[i])
                                    if(!strcmp(p, pubkeys_fp64[i]))
                                          if(clientid < 0)
                                                clientid = i;
                        }
                        if(clientid < 0)
                              return Crypto_ServerError(data_out, len_out, "Invalid client key", NULL);
                  }

                  crypto = Crypto_ServerFindInstance(peeraddress, true);
                  if(!crypto)
                        return Crypto_ServerError(data_out, len_out, "Could not create a crypto connect instance", NULL);
                  MAKE_CDATA;
                  CDATA->cdata_id = id;
                  CDATA->s = serverid;
                  CDATA->c = clientid;
                  memset(crypto->dhkey, 0, sizeof(crypto->dhkey));
                  CDATA->challenge[0] = 0;
                  crypto->client_keyfp[0] = 0;
                  crypto->client_idfp[0] = 0;
                  crypto->server_keyfp[0] = 0;
                  crypto->server_idfp[0] = 0;
                  crypto->use_aes = aes != 0;

                  if(CDATA->s >= 0)
                  {
                        // I am the server, and my key is ok... so let's set server_keyfp and server_idfp
                        strlcpy(crypto->server_keyfp, pubkeys_fp64[CDATA->s], sizeof(crypto->server_keyfp));
                        strlcpy(crypto->server_idfp, pubkeys_priv_fp64[CDATA->s], sizeof(crypto->server_idfp));

                        if(!CDATA->id)
                              CDATA->id = qd0_blind_id_new();
                        if(!CDATA->id)
                        {
                              CLEAR_CDATA;
                              return Crypto_ServerError(data_out, len_out, "d0_blind_id_new failed", "Internal error");
                        }
                        if(!qd0_blind_id_copy(CDATA->id, pubkeys[CDATA->s]))
                        {
                              CLEAR_CDATA;
                              return Crypto_ServerError(data_out, len_out, "d0_blind_id_copy failed", "Internal error");
                        }
                        PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\1\\id\\%d\\aes\\%d", CDATA->cdata_id, crypto->use_aes));
                        if(!qd0_blind_id_authenticate_with_private_id_start(CDATA->id, true, false, "XONOTIC", 8, data_out_p, len_out)) // len_out receives used size by this op
                        {
                              CLEAR_CDATA;
                              return Crypto_ServerError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_start failed", "Internal error");
                        }
                        CDATA->next_step = 2;
                        data_out_p += *len_out;
                        *len_out = data_out_p - data_out;
                        return CRYPTO_DISCARD;
                  }
                  else if(CDATA->c >= 0)
                  {
                        if(!CDATA->id)
                              CDATA->id = qd0_blind_id_new();
                        if(!CDATA->id)
                        {
                              CLEAR_CDATA;
                              return Crypto_ServerError(data_out, len_out, "d0_blind_id_new failed", "Internal error");
                        }
                        if(!qd0_blind_id_copy(CDATA->id, pubkeys[CDATA->c]))
                        {
                              CLEAR_CDATA;
                              return Crypto_ServerError(data_out, len_out, "d0_blind_id_copy failed", "Internal error");
                        }
                        PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\5\\id\\%d\\aes\\%d", CDATA->cdata_id, crypto->use_aes));
                        if(!qd0_blind_id_authenticate_with_private_id_challenge(CDATA->id, true, false, data_in, len_in, data_out_p, len_out, &status))
                        {
                              CLEAR_CDATA;
                              return Crypto_ServerError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_challenge failed", "Internal error");
                        }
                        CDATA->next_step = 6;
                        data_out_p += *len_out;
                        *len_out = data_out_p - data_out;
                        return CRYPTO_DISCARD;
                  }
                  else
                  {
                        CLEAR_CDATA;
                        return Crypto_ServerError(data_out, len_out, "Missing client and server key", NULL);
                  }
            }
            else if(!strcmp(cnt, "2"))
            {
                  size_t fpbuflen;
                  crypto = Crypto_ServerFindInstance(peeraddress, false);
                  if(!crypto)
                        return CRYPTO_NOMATCH; // pre-challenge, rather be silent
                  if(id >= 0)
                        if(CDATA->cdata_id != id)
                              return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\id\\%d when expecting %d", id, CDATA->cdata_id));
                  if(CDATA->next_step != 2)
                        return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\cnt\\%s when expecting %d", cnt, CDATA->next_step));

                  PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\3\\id\\%d", CDATA->cdata_id));
                  if(!qd0_blind_id_authenticate_with_private_id_response(CDATA->id, data_in, len_in, data_out_p, len_out))
                  {
                        CLEAR_CDATA;
                        return Crypto_ServerError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_response failed", "Internal error");
                  }
                  fpbuflen = DHKEY_SIZE;
                  if(!qd0_blind_id_sessionkey_public_id(CDATA->id, (char *) crypto->dhkey, &fpbuflen))
                  {
                        CLEAR_CDATA;
                        return Crypto_ServerError(data_out, len_out, "d0_blind_id_sessionkey_public_id failed", "Internal error");
                  }
                  if(CDATA->c >= 0)
                  {
                        if(!qd0_blind_id_copy(CDATA->id, pubkeys[CDATA->c]))
                        {
                              CLEAR_CDATA;
                              return Crypto_ServerError(data_out, len_out, "d0_blind_id_copy failed", "Internal error");
                        }
                        CDATA->next_step = 4;
                  }
                  else
                  {
                        // session key is FINISHED (no server part is to be expected)! By this, all keys are set up
                        crypto->authenticated = true;
                        CDATA->next_step = 0;
                  }
                  data_out_p += *len_out;
                  *len_out = data_out_p - data_out;
                  return CRYPTO_DISCARD;
            }
            else if(!strcmp(cnt, "4"))
            {
                  crypto = Crypto_ServerFindInstance(peeraddress, false);
                  if(!crypto)
                        return CRYPTO_NOMATCH; // pre-challenge, rather be silent
                  if(id >= 0)
                        if(CDATA->cdata_id != id)
                              return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\id\\%d when expecting %d", id, CDATA->cdata_id));
                  if(CDATA->next_step != 4)
                        return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\cnt\\%s when expecting %d", cnt, CDATA->next_step));
                  PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\5\\id\\%d", CDATA->cdata_id));
                  if(!qd0_blind_id_authenticate_with_private_id_challenge(CDATA->id, true, false, data_in, len_in, data_out_p, len_out, &status))
                  {
                        CLEAR_CDATA;
                        return Crypto_ServerError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_challenge failed", "Internal error");
                  }
                  CDATA->next_step = 6;
                  data_out_p += *len_out;
                  *len_out = data_out_p - data_out;
                  return CRYPTO_DISCARD;
            }
            else if(!strcmp(cnt, "6"))
            {
                  static char msgbuf[32];
                  size_t msgbuflen = sizeof(msgbuf);
                  size_t fpbuflen;
                  int i;
                  unsigned char dhkey[DHKEY_SIZE];
                  crypto = Crypto_ServerFindInstance(peeraddress, false);
                  if(!crypto)
                        return CRYPTO_NOMATCH; // pre-challenge, rather be silent
                  if(id >= 0)
                        if(CDATA->cdata_id != id)
                              return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\id\\%d when expecting %d", id, CDATA->cdata_id));
                  if(CDATA->next_step != 6)
                        return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\cnt\\%s when expecting %d", cnt, CDATA->next_step));

                  if(!qd0_blind_id_authenticate_with_private_id_verify(CDATA->id, data_in, len_in, msgbuf, &msgbuflen, &status))
                  {
                        CLEAR_CDATA;
                        return Crypto_ServerError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_verify failed (authentication error)", "Authentication error");
                  }
                  if(status)
                        strlcpy(crypto->client_keyfp, pubkeys_fp64[CDATA->c], sizeof(crypto->client_keyfp));
                  else
                        crypto->client_keyfp[0] = 0;
                  memset(crypto->client_idfp, 0, sizeof(crypto->client_idfp));
                  fpbuflen = FP64_SIZE;
                  if(!qd0_blind_id_fingerprint64_public_id(CDATA->id, crypto->client_idfp, &fpbuflen))
                  {
                        CLEAR_CDATA;
                        return Crypto_ServerError(data_out, len_out, "d0_blind_id_fingerprint64_public_id failed", "Internal error");
                  }
                  fpbuflen = DHKEY_SIZE;
                  if(!qd0_blind_id_sessionkey_public_id(CDATA->id, (char *) dhkey, &fpbuflen))
                  {
                        CLEAR_CDATA;
                        return Crypto_ServerError(data_out, len_out, "d0_blind_id_sessionkey_public_id failed", "Internal error");
                  }
                  // XOR the two DH keys together to make one
                  for(i = 0; i < DHKEY_SIZE; ++i)
                        crypto->dhkey[i] ^= dhkey[i];

                  // session key is FINISHED (no server part is to be expected)! By this, all keys are set up
                  crypto->authenticated = true;
                  CDATA->next_step = 0;
                  // send a challenge-less challenge
                  PutWithNul(&data_out_p, len_out, "challenge ");
                  *len_out = data_out_p - data_out;
                  --*len_out; // remove NUL terminator
                  return CRYPTO_MATCH;
            }
            return CRYPTO_NOMATCH; // pre-challenge, rather be silent
      }
      return CRYPTO_NOMATCH;
}

int Crypto_ServerParsePacket(const char *data_in, size_t len_in, char *data_out, size_t *len_out, lhnetaddress_t *peeraddress)
{
      int ret;
      double t = 0;
      static double complain_time = 0;
      const char *cnt;
      qboolean do_time = false;
      qboolean do_reject = false;
      if(crypto_servercpupercent.value > 0 || crypto_servercpumaxtime.value > 0)
            if(len_in > 5 && !memcmp(data_in, "d0pk\\", 5))
            {
                  do_time = true;
                  cnt = SearchInfostring(data_in + 4, "cnt");
                  if(cnt)
                        if(!strcmp(cnt, "0"))
                              do_reject = true;
            }
      if(do_time)
      {
            // check if we may perform crypto...
            if(crypto_servercpupercent.value > 0)
            {
                  crypto_servercpu_accumulator += (realtime - crypto_servercpu_lastrealtime) * crypto_servercpupercent.value * 0.01;
                  if(crypto_servercpumaxtime.value)
                        if(crypto_servercpu_accumulator > crypto_servercpumaxtime.value)
                              crypto_servercpu_accumulator = crypto_servercpumaxtime.value;
            }
            else
            {
                  if(crypto_servercpumaxtime.value > 0)
                        if(realtime != crypto_servercpu_lastrealtime)
                              crypto_servercpu_accumulator = crypto_servercpumaxtime.value;
            }
            crypto_servercpu_lastrealtime = realtime;
            if(do_reject && crypto_servercpu_accumulator < 0)
            {
                  if(realtime > complain_time + 5)
                        Con_Printf("crypto: cannot perform requested crypto operations; denial service attack or crypto_servercpupercent/crypto_servercpumaxtime are too low\n");
                  *len_out = 0;
                  return CRYPTO_DISCARD;
            }
            t = Sys_DoubleTime();
      }
      ret = Crypto_ServerParsePacket_Internal(data_in, len_in, data_out, len_out, peeraddress);
      if(do_time)
      {
            t = Sys_DoubleTime() - t;
            if(crypto_servercpudebug.integer)
                  Con_Printf("crypto: accumulator was %.1f ms, used %.1f ms for crypto, ", crypto_servercpu_accumulator * 1000, t * 1000);
            crypto_servercpu_accumulator -= t;
            if(crypto_servercpudebug.integer)
                  Con_Printf("is %.1f ms\n", crypto_servercpu_accumulator * 1000);
      }
      return ret;
}

static int Crypto_ClientError(char *data_out, size_t *len_out, const char *msg)
{
      dpsnprintf(data_out, *len_out, "reject %s", msg);
      *len_out = strlen(data_out);
      return CRYPTO_REPLACE;
}

static int Crypto_SoftClientError(char *data_out, size_t *len_out, const char *msg)
{
      *len_out = 0;
      Con_Printf("%s\n", msg);
      return CRYPTO_DISCARD;
}

int Crypto_ClientParsePacket(const char *data_in, size_t len_in, char *data_out, size_t *len_out, lhnetaddress_t *peeraddress)
{
      crypto_t *crypto = &cls.crypto;
      const char *string = data_in;
      const char *s;
      D0_BOOL aes;
      char *data_out_p = data_out;
      D0_BOOL status;

      if(!d0_blind_id_dll)
            return CRYPTO_NOMATCH; // no support

      // if "challenge": verify challenge, and discard message, send next crypto protocol message instead
      // otherwise, just handle actual protocol messages

      if (len_in == 6 && !memcmp(string, "accept", 6) && cls.connect_trying && d0_rijndael_dll)
      {
            int wantserverid = -1;
            Crypto_RetrieveHostKey(&cls.connect_address, &wantserverid, NULL, 0, NULL, 0, NULL);
            if(!crypto || !crypto->authenticated)
            {
                  if(wantserverid >= 0)
                        return Crypto_ClientError(data_out, len_out, "Server tried an unauthenticated connection even though a host key is present");
                  if(crypto_aeslevel.integer >= 3)
                        return Crypto_ClientError(data_out, len_out, "This server requires encryption to be not required (crypto_aeslevel <= 2)");
            }
            return CRYPTO_NOMATCH;
      }
      else if (len_in >= 1 && string[0] == 'j' && cls.connect_trying && d0_rijndael_dll && crypto_aeslevel.integer >= 3)
      {
            int wantserverid = -1;
            Crypto_RetrieveHostKey(&cls.connect_address, &wantserverid, NULL, 0, NULL, 0, NULL);
            if(!crypto || !crypto->authenticated)
            {
                  if(wantserverid >= 0)
                        return Crypto_ClientError(data_out, len_out, "Server tried an unauthenticated connection even though a host key is present");
                  if(crypto_aeslevel.integer >= 3)
                        return Crypto_ClientError(data_out, len_out, "This server requires encryption to be not required (crypto_aeslevel <= 2)");
            }
            return CRYPTO_NOMATCH;
      }
      else if (len_in >= 13 && !memcmp(string, "infoResponse\x0A", 13))
      {
            s = SearchInfostring(string + 13, "d0_blind_id");
            if(s)
                  Crypto_StoreHostKey(peeraddress, s, true);
            return CRYPTO_NOMATCH;
      }
      else if (len_in >= 15 && !memcmp(string, "statusResponse\x0A", 15))
      {
            char save = 0;
            const char *p;
            p = strchr(string + 15, '\n');
            if(p)
            {
                  save = *p;
                  * (char *) p = 0; // cut off the string there
            }
            s = SearchInfostring(string + 15, "d0_blind_id");
            if(s)
                  Crypto_StoreHostKey(peeraddress, s, true);
            if(p)
            {
                  * (char *) p = save;
                  // invoking those nasal demons again (do not run this on the DS9k)
            }
            return CRYPTO_NOMATCH;
      }
      else if(len_in > 10 && !memcmp(string, "challenge ", 10) && cls.connect_trying)
      {
            const char *vlen_blind_id_ptr = NULL;
            size_t len_blind_id_ptr = 0;
            unsigned long k, v;
            const char *challenge = data_in + 10;
            const char *p;
            int i;
            int clientid = -1, serverid = -1, wantserverid = -1;
            qboolean server_can_auth = true;
            char wantserver_idfp[FP64_SIZE+1];
            int wantserver_aeslevel;

            // if we have a stored host key for the server, assume serverid to already be selected!
            // (the loop will refuse to overwrite this one then)
            wantserver_idfp[0] = 0;
            Crypto_RetrieveHostKey(&cls.connect_address, &wantserverid, NULL, 0, wantserver_idfp, sizeof(wantserver_idfp), &wantserver_aeslevel);
            // requirement: wantserver_idfp is a full ID if wantserverid set

            // if we leave, we have to consider the connection
            // unauthenticated; NOTE: this may be faked by a clever
            // attacker to force an unauthenticated connection; so we have
            // a safeguard check in place when encryption is required too
            // in place, or when authentication is required by the server
            crypto->authenticated = false;

            GetUntilNul(&data_in, &len_in);
            if(!data_in)
                  return (wantserverid >= 0) ? Crypto_ClientError(data_out, len_out, "Server tried an unauthenticated connection even though a host key is present") :
                        (d0_rijndael_dll && crypto_aeslevel.integer >= 3) ? Crypto_ServerError(data_out, len_out, "This server requires encryption to be not required (crypto_aeslevel <= 2)", NULL) :
                        CRYPTO_NOMATCH;

            // FTEQW extension protocol
            while(len_in >= 8)
            {
                  k = Crypto_LittleLong(data_in);
                  v = Crypto_LittleLong(data_in + 4);
                  data_in += 8;
                  len_in -= 8;
                  switch(k)
                  {
                        case PROTOCOL_VLEN:
                              if(len_in >= 4 + v)
                              {
                                    k = Crypto_LittleLong(data_in);
                                    data_in += 4;
                                    len_in -= 4;
                                    switch(k)
                                    {
                                          case PROTOCOL_D0_BLIND_ID:
                                                vlen_blind_id_ptr = data_in;
                                                len_blind_id_ptr = v;
                                                break;
                                    }
                                    data_in += v;
                                    len_in -= v;
                              }
                              break;
                        default:
                              break;
                  }
            }

            if(!vlen_blind_id_ptr)
                  return (wantserverid >= 0) ? Crypto_ClientError(data_out, len_out, "Server tried an unauthenticated connection even though authentication is required") :
                        (d0_rijndael_dll && crypto_aeslevel.integer >= 3) ? Crypto_ServerError(data_out, len_out, "This server requires encryption to be not required (crypto_aeslevel <= 2)", NULL) :
                        CRYPTO_NOMATCH;

            data_in = vlen_blind_id_ptr;
            len_in = len_blind_id_ptr;

            // parse fingerprints
            //   once we found a fingerprint we can auth to (ANY), select it as clientfp
            //   once we found a fingerprint in the first list that we know, select it as serverfp

            for(;;)
            {
                  p = GetUntilNul(&data_in, &len_in);
                  if(!p)
                        break;
                  if(!*p)
                  {
                        if(!server_can_auth)
                              break; // other protocol message may follow
                        server_can_auth = false;
                        if(clientid >= 0)
                              break;
                        continue;
                  }
                  for(i = 0; i < MAX_PUBKEYS; ++i)
                  {
                        if(pubkeys[i])
                        if(!strcmp(p, pubkeys_fp64[i]))
                        {
                              if(pubkeys_havepriv[i])
                                    if(clientid < 0)
                                          clientid = i;
                              if(server_can_auth)
                                    if(serverid < 0)
                                          if(wantserverid < 0 || i == wantserverid)
                                                serverid = i;
                        }
                  }
                  if(clientid >= 0 && serverid >= 0)
                        break;
            }

            // if stored host key is not found:
            if(wantserverid >= 0 && serverid < 0)
                  return Crypto_ClientError(data_out, len_out, "Server CA does not match stored host key, refusing to connect");

            if(serverid >= 0 || clientid >= 0)
            {
                  // TODO at this point, fill clientside crypto struct!
                  MAKE_CDATA;
                  CDATA->cdata_id = ++cdata_id;
                  CDATA->s = serverid;
                  CDATA->c = clientid;
                  memset(crypto->dhkey, 0, sizeof(crypto->dhkey));
                  strlcpy(CDATA->challenge, challenge, sizeof(CDATA->challenge));
                  crypto->client_keyfp[0] = 0;
                  crypto->client_idfp[0] = 0;
                  crypto->server_keyfp[0] = 0;
                  crypto->server_idfp[0] = 0;
                  memcpy(CDATA->wantserver_idfp, wantserver_idfp, sizeof(crypto->server_idfp));

                  if(CDATA->wantserver_idfp[0]) // if we know a host key, honor its encryption setting
                  switch(bound(0, d0_rijndael_dll ? crypto_aeslevel.integer : 0, 3))
                  {
                        default: // dummy, never happens, but to make gcc happy...
                        case 0:
                              if(wantserver_aeslevel >= 3)
                                    return Crypto_ServerError(data_out, len_out, "This server requires encryption to be not required (crypto_aeslevel <= 2)", NULL);
                              CDATA->wantserver_aes = false;
                              break;
                        case 1:
                              CDATA->wantserver_aes = (wantserver_aeslevel >= 2);
                              break;
                        case 2:
                              CDATA->wantserver_aes = (wantserver_aeslevel >= 1);
                              break;
                        case 3:
                              if(wantserver_aeslevel <= 0)
                                    return Crypto_ServerError(data_out, len_out, "This server requires encryption to be supported (crypto_aeslevel >= 1, and d0_rijndael library must be present)", NULL);
                              CDATA->wantserver_aes = true;
                              break;
                  }

                  // build outgoing message
                  // append regular stuff
                  PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\0\\id\\%d\\aeslevel\\%d\\challenge\\%s", CDATA->cdata_id, d0_rijndael_dll ? crypto_aeslevel.integer : 0, challenge));
                  PutWithNul(&data_out_p, len_out, serverid >= 0 ? pubkeys_fp64[serverid] : "");
                  PutWithNul(&data_out_p, len_out, clientid >= 0 ? pubkeys_fp64[clientid] : "");

                  if(clientid >= 0)
                  {
                        // I am the client, and my key is ok... so let's set client_keyfp and client_idfp
                        strlcpy(crypto->client_keyfp, pubkeys_fp64[CDATA->c], sizeof(crypto->client_keyfp));
                        strlcpy(crypto->client_idfp, pubkeys_priv_fp64[CDATA->c], sizeof(crypto->client_idfp));
                  }

                  if(serverid >= 0)
                  {
                        if(!CDATA->id)
                              CDATA->id = qd0_blind_id_new();
                        if(!CDATA->id)
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "d0_blind_id_new failed");
                        }
                        if(!qd0_blind_id_copy(CDATA->id, pubkeys[CDATA->s]))
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "d0_blind_id_copy failed");
                        }
                        CDATA->next_step = 1;
                        *len_out = data_out_p - data_out;
                  }
                  else if(clientid >= 0)
                  {
                        // skip over server auth, perform client auth only
                        if(!CDATA->id)
                              CDATA->id = qd0_blind_id_new();
                        if(!CDATA->id)
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "d0_blind_id_new failed");
                        }
                        if(!qd0_blind_id_copy(CDATA->id, pubkeys[CDATA->c]))
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "d0_blind_id_copy failed");
                        }
                        if(!qd0_blind_id_authenticate_with_private_id_start(CDATA->id, true, false, "XONOTIC", 8, data_out_p, len_out)) // len_out receives used size by this op
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_start failed");
                        }
                        CDATA->next_step = 5;
                        data_out_p += *len_out;
                        *len_out = data_out_p - data_out;
                  }
                  else
                        *len_out = data_out_p - data_out;

                  return CRYPTO_DISCARD;
            }
            else
            {
                  if(wantserver_idfp[0]) // if we know a host key, honor its encryption setting
                  if(wantserver_aeslevel >= 3)
                        return Crypto_ClientError(data_out, len_out, "Server insists on encryption, but neither can authenticate to the other");
                  return (d0_rijndael_dll && crypto_aeslevel.integer >= 3) ? Crypto_ServerError(data_out, len_out, "This server requires encryption to be not required (crypto_aeslevel <= 2)", NULL) :
                        CRYPTO_NOMATCH;
            }
      }
      else if(len_in > 5 && !memcmp(string, "d0pk\\", 5) && cls.connect_trying)
      {
            const char *cnt;
            int id;
            cnt = SearchInfostring(string + 4, "id");
            id = (cnt ? atoi(cnt) : -1);
            cnt = SearchInfostring(string + 4, "cnt");
            if(!cnt)
                  return Crypto_ClientError(data_out, len_out, "d0pk\\ message without cnt");
            GetUntilNul(&data_in, &len_in);
            if(!data_in)
                  return Crypto_ClientError(data_out, len_out, "d0pk\\ message without attachment");

            if(!strcmp(cnt, "1"))
            {
                  if(id >= 0)
                        if(CDATA->cdata_id != id)
                              return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\id\\%d when expecting %d", id, CDATA->cdata_id));
                  if(CDATA->next_step != 1)
                        return Crypto_SoftClientError(data_out, len_out, va("Got d0pk\\cnt\\%s when expecting %d", cnt, CDATA->next_step));

                  cls.connect_nextsendtime = max(cls.connect_nextsendtime, realtime + 1); // prevent "hammering"

                  if((s = SearchInfostring(string + 4, "aes")))
                        aes = atoi(s);
                  else
                        aes = false;
                  // we CANNOT toggle the AES status any more!
                  // as the server already decided
                  if(CDATA->wantserver_idfp[0]) // if we know a host key, honor its encryption setting
                  if(!aes && CDATA->wantserver_aes)
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "Stored host key requires encryption, but server did not enable encryption");
                  }
                  if(aes && (!d0_rijndael_dll || crypto_aeslevel.integer <= 0))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "Server insists on encryption too hard");
                  }
                  if(!aes && (d0_rijndael_dll && crypto_aeslevel.integer >= 3))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "Server insists on plaintext too hard");
                  }
                  crypto->use_aes = aes != 0;

                  PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\2\\id\\%d", CDATA->cdata_id));
                  if(!qd0_blind_id_authenticate_with_private_id_challenge(CDATA->id, true, false, data_in, len_in, data_out_p, len_out, &status))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_challenge failed");
                  }
                  CDATA->next_step = 3;
                  data_out_p += *len_out;
                  *len_out = data_out_p - data_out;
                  return CRYPTO_DISCARD;
            }
            else if(!strcmp(cnt, "3"))
            {
                  static char msgbuf[32];
                  size_t msgbuflen = sizeof(msgbuf);
                  size_t fpbuflen;

                  if(id >= 0)
                        if(CDATA->cdata_id != id)
                              return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\id\\%d when expecting %d", id, CDATA->cdata_id));
                  if(CDATA->next_step != 3)
                        return Crypto_SoftClientError(data_out, len_out, va("Got d0pk\\cnt\\%s when expecting %d", cnt, CDATA->next_step));

                  cls.connect_nextsendtime = max(cls.connect_nextsendtime, realtime + 1); // prevent "hammering"

                  if(!qd0_blind_id_authenticate_with_private_id_verify(CDATA->id, data_in, len_in, msgbuf, &msgbuflen, &status))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_verify failed (server authentication error)");
                  }
                  if(status)
                        strlcpy(crypto->server_keyfp, pubkeys_fp64[CDATA->s], sizeof(crypto->server_keyfp));
                  else
                        crypto->server_keyfp[0] = 0;
                  memset(crypto->server_idfp, 0, sizeof(crypto->server_idfp));
                  fpbuflen = FP64_SIZE;
                  if(!qd0_blind_id_fingerprint64_public_id(CDATA->id, crypto->server_idfp, &fpbuflen))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "d0_blind_id_fingerprint64_public_id failed");
                  }
                  if(CDATA->wantserver_idfp[0])
                  if(memcmp(CDATA->wantserver_idfp, crypto->server_idfp, sizeof(crypto->server_idfp)))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "Server ID does not match stored host key, refusing to connect");
                  }
                  fpbuflen = DHKEY_SIZE;
                  if(!qd0_blind_id_sessionkey_public_id(CDATA->id, (char *) crypto->dhkey, &fpbuflen))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "d0_blind_id_sessionkey_public_id failed");
                  }

                  // cache the server key
                  Crypto_StoreHostKey(&cls.connect_address, va("%d %s@%s", crypto->use_aes ? 1 : 0, crypto->server_idfp, pubkeys_fp64[CDATA->s]), false);

                  if(CDATA->c >= 0)
                  {
                        // client will auth next
                        PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\4\\id\\%d", CDATA->cdata_id));
                        if(!qd0_blind_id_copy(CDATA->id, pubkeys[CDATA->c]))
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "d0_blind_id_copy failed");
                        }
                        if(!qd0_blind_id_authenticate_with_private_id_start(CDATA->id, true, false, "XONOTIC", 8, data_out_p, len_out)) // len_out receives used size by this op
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_start failed");
                        }
                        CDATA->next_step = 5;
                        data_out_p += *len_out;
                        *len_out = data_out_p - data_out;
                        return CRYPTO_DISCARD;
                  }
                  else
                  {
                        // session key is FINISHED (no server part is to be expected)! By this, all keys are set up
                        crypto->authenticated = true;
                        CDATA->next_step = 0;
                        // assume we got the empty challenge to finish the protocol
                        PutWithNul(&data_out_p, len_out, "challenge ");
                        *len_out = data_out_p - data_out;
                        --*len_out; // remove NUL terminator
                        return CRYPTO_REPLACE;
                  }
            }
            else if(!strcmp(cnt, "5"))
            {
                  size_t fpbuflen;
                  unsigned char dhkey[DHKEY_SIZE];
                  int i;

                  if(id >= 0)
                        if(CDATA->cdata_id != id)
                              return Crypto_SoftServerError(data_out, len_out, va("Got d0pk\\id\\%d when expecting %d", id, CDATA->cdata_id));
                  if(CDATA->next_step != 5)
                        return Crypto_SoftClientError(data_out, len_out, va("Got d0pk\\cnt\\%s when expecting %d", cnt, CDATA->next_step));

                  cls.connect_nextsendtime = max(cls.connect_nextsendtime, realtime + 1); // prevent "hammering"

                  if(CDATA->s < 0) // only if server didn't auth
                  {
                        if((s = SearchInfostring(string + 4, "aes")))
                              aes = atoi(s);
                        else
                              aes = false;
                        if(CDATA->wantserver_idfp[0]) // if we know a host key, honor its encryption setting
                        if(!aes && CDATA->wantserver_aes)
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "Stored host key requires encryption, but server did not enable encryption");
                        }
                        if(aes && (!d0_rijndael_dll || crypto_aeslevel.integer <= 0))
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "Server insists on encryption too hard");
                        }
                        if(!aes && (d0_rijndael_dll && crypto_aeslevel.integer >= 3))
                        {
                              CLEAR_CDATA;
                              return Crypto_ClientError(data_out, len_out, "Server insists on plaintext too hard");
                        }
                        crypto->use_aes = aes != 0;
                  }

                  PutWithNul(&data_out_p, len_out, va("d0pk\\cnt\\6\\id\\%d", CDATA->cdata_id));
                  if(!qd0_blind_id_authenticate_with_private_id_response(CDATA->id, data_in, len_in, data_out_p, len_out))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "d0_blind_id_authenticate_with_private_id_response failed");
                  }
                  fpbuflen = DHKEY_SIZE;
                  if(!qd0_blind_id_sessionkey_public_id(CDATA->id, (char *) dhkey, &fpbuflen))
                  {
                        CLEAR_CDATA;
                        return Crypto_ClientError(data_out, len_out, "d0_blind_id_sessionkey_public_id failed");
                  }
                  // XOR the two DH keys together to make one
                  for(i = 0; i < DHKEY_SIZE; ++i)
                        crypto->dhkey[i] ^= dhkey[i];
                  // session key is FINISHED! By this, all keys are set up
                  crypto->authenticated = true;
                  CDATA->next_step = 0;
                  data_out_p += *len_out;
                  *len_out = data_out_p - data_out;
                  return CRYPTO_DISCARD;
            }
            return Crypto_SoftClientError(data_out, len_out, "Got unknown d0_blind_id message from server");
      }

      return CRYPTO_NOMATCH;
}

size_t Crypto_SignData(const void *data, size_t datasize, int keyid, void *signed_data, size_t signed_size)
{
      if(keyid < 0 || keyid >= MAX_PUBKEYS)
            return 0;
      if(!pubkeys_havepriv[keyid])
            return 0;
      if(qd0_blind_id_sign_with_private_id_sign(pubkeys[keyid], true, false, (const char *)data, datasize, (char *)signed_data, &signed_size))
            return signed_size;
      return 0;
}

size_t Crypto_SignDataDetached(const void *data, size_t datasize, int keyid, void *signed_data, size_t signed_size)
{
      if(keyid < 0 || keyid >= MAX_PUBKEYS)
            return 0;
      if(!pubkeys_havepriv[keyid])
            return 0;
      if(qd0_blind_id_sign_with_private_id_sign_detached(pubkeys[keyid], true, false, (const char *)data, datasize, (char *)signed_data, &signed_size))
            return signed_size;
      return 0;
}

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