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/* nettle.cmod -*- c -*- */ 
 
#include "global.h" 
#include "interpret.h" 
#include "svalue.h" 
/* For this_object() */ 
#include "object.h" 
#include "operators.h" 
#include "module_support.h" 
#include "threads.h" 
#include "pike_memory.h" 
 
#include "nettle_config.h" 
 
#ifdef HAVE_LIBNETTLE 
 
#include "nettle.h" 
 
#include <nettle/yarrow.h> 
 
#include <stdio.h> 
#include <stdarg.h> 
 
DECLARATIONS 
 
/*! @module Nettle 
 *! Low level crypto functions used by the @[Crypto] module. Unless 
 *! you are doing something very special, you would want to use the 
 *! Crypto module instead. 
 */ 
 
/*! @decl string version() 
 *! Returns the version of the Nettle library, e.g. "3.1". 0 is 
 *! returned when runtime version is unknown. 
 */ 
PIKEFUN string version() 
{ 
#ifdef HAVE_NETTLE_VERSION_H 
  push_constant_text("%d.%d"); 
#ifdef HAVE_NETTLE_VERSION_MAJOR 
  push_int( nettle_version_major() ); 
  push_int( nettle_version_minor() ); 
#else 
  /* Probably Nettle 3.1.1. */ 
  push_int( NETTLE_VERSION_MAJOR ); 
  push_int( NETTLE_VERSION_MINOR ); 
#endif 
  f_sprintf(3); 
#else 
  push_int(0); 
#endif 
} 
 
/*! @class Yarrow 
 *! 
 *! Yarrow is a family of pseudo-randomness generators, designed for 
 *! cryptographic use, by John Kelsey, Bruce Schneier and Niels Ferguson. 
 *! Yarrow-160 is described in a paper at 
 *! @url{http://www.schneier.com/paper-yarrow.html@}, and it uses SHA1 and 
 *! triple-DES, and has a 160-bit internal state. Nettle implements 
 *! Yarrow-256, which is similar, but uses SHA256 and AES to get an 
 *! internal state of 256 bits. 
 */ 
PIKECLASS Yarrow 
program_flags PROGRAM_CLEAR_STORAGE; 
{ 
  CVAR struct yarrow256_ctx ctx; 
  CVAR struct yarrow_source *sources; 
 
  DECLARE_STORAGE; 
 
  /*! @decl void create(void|int sources) 
   *! The number of entropy sources that will feed entropy to the 
   *! random number generator is given as an argument to Yarrow 
   *! during instantiation. 
   *! @seealso 
   *!   @[update] 
   */ 
  PIKEFUN void create(void|int arg) 
    flags ID_PROTECTED; 
  { 
    INT32 num = 0; 
 
    if(arg) { 
      if (TYPEOF(*arg) != PIKE_T_INT) 
        Pike_error("Bad argument type.\n"); 
      num = arg->u.integer; 
      if(num < 0) 
        Pike_error("Invalid number of sources.\n"); 
      free (THIS->sources); 
      THIS->sources = xalloc(sizeof(struct yarrow_source)*num); 
    } 
    else 
    { 
      free (THIS->sources); 
      THIS->sources = NULL; 
    } 
    yarrow256_init(&THIS->ctx, num, THIS->sources); 
  } 
 
  /*! @decl Yarrow seed(string(0..255) data) 
   *! 
   *! The random generator needs to be seeded before it can be used. 
   *! The seed must be at least 32 characters long. The seed could be 
   *! stored from a previous run by inserting the value returned from 
   *! previous @[random_string] call. 
   *! 
   *! @returns 
   *!   Returns the called object. 
   *! @seealso 
   *!   @[min_seed_size], @[is_seeded] 
   */ 
  PIKEFUN object seed(string(0..255) data) 
    optflags OPT_SIDE_EFFECT; 
  { 
    if(data->len < YARROW256_SEED_FILE_SIZE) 
      Pike_error("Seed must be at least %d characters.\n", 
                 YARROW256_SEED_FILE_SIZE); 
 
    NO_WIDE_STRING(data); 
    yarrow256_seed(&THIS->ctx, data->len, STR0(data)); 
    RETURN this_object(); 
  } 
 
  /*! @decl int(0..) min_seed_size() 
   *! Returns the minimal number of characters that the @[seed] 
   *! needs to properly seed the random number generator. 
   *! @seealso 
   *!   @[seed] 
   */ 
  PIKEFUN int(0..) min_seed_size() 
    optflags OPT_TRY_OPTIMIZE; 
  { 
    RETURN YARROW256_SEED_FILE_SIZE; 
  } 
 
  /*! @decl int(0..1) is_seeded() 
   *! Returns 1 if the random generator is seeded and ready 
   *! to generator output. 0 otherwise. 
   *! @seealso 
   *!   @[seed] 
   */ 
  PIKEFUN int(0..1) is_seeded() 
    optflags OPT_EXTERNAL_DEPEND; 
  { 
    RETURN yarrow256_is_seeded(&THIS->ctx); 
  } 
 
  /*! @decl void force_reseed() 
   *! By calling this function entropy is moved from the slow 
   *! pool to the fast pool. Read more about Yarrow before using 
   *! this. 
   */ 
  PIKEFUN void force_reseed() 
    optflags OPT_SIDE_EFFECT; 
  { 
#ifdef HAVE_NETTLE_YARROW256_SLOW_RESEED 
    /* From change notes for Nettle 2.0: 
     * 
     * * Changes to the yarrow256 interface. The function 
     *   yarrow256_force_reseed has been replaced by the two 
     *   functions yarrow256_fast_reseed and yarrow256_slow_reseed, 
     *   which were previously static. 
     */ 
    yarrow256_slow_reseed(&THIS->ctx); 
#else 
    yarrow256_force_reseed(&THIS->ctx); 
#endif 
  } 
 
  /*! @decl int(0..1) update(string(0..255) data, int source, int entropy) 
   *! Inject additional entropy into the random number generator. 
   *! 
   *! @seealso 
   *!   @[create] 
   */ 
  PIKEFUN int(0..1) update(string(0..255) data, int source, int entropy) 
    optflags OPT_SIDE_EFFECT; 
  { 
    int ret; 
    /* FIXME: Wide strings could actually be supported here */ 
    NO_WIDE_STRING(data); 
    if( !THIS->sources ) 
      Pike_error("This random generator has no sources.\n"); 
    if( source<0 || (unsigned)source>=THIS->ctx.nsources ) 
      Pike_error("Invalid random source.\n"); 
    if( entropy<0 ) 
      Pike_error("Entropy must be positive.\n"); 
    if( entropy>(data->len*8) ) 
      Pike_error("Impossibly large entropy value.\n"); 
    ret = yarrow256_update(&THIS->ctx, source, entropy, data->len, 
                           (const uint8_t *)data->str); 
    RETURN ret; 
  } 
 
  /*! @decl int(0..) needed_sources() 
   *! The number of sources that must reach the threshold before a 
   *! slow reseed will happen. 
   */ 
  PIKEFUN int(0..) needed_sources() 
    optflags OPT_EXTERNAL_DEPEND; 
  { 
    RETURN yarrow256_needed_sources(&THIS->ctx); 
  } 
 
  /*! @decl string(0..255) random_string(int length) 
   *! Returns a pseudo-random string of the requested @[length]. 
   */ 
  PIKEFUN string(0..255) random_string(int length) 
    optflags OPT_EXTERNAL_DEPEND|OPT_SIDE_EFFECT; 
  { 
    struct pike_string *rnd; 
    if(length < 0) 
      Pike_error("Invalid length, must be positive.\n"); 
    if( !yarrow256_is_seeded(&THIS->ctx) ) 
      Pike_error("Random generator not seeded.\n"); 
    rnd = begin_shared_string(length); 
    yarrow256_random(&THIS->ctx, length, (uint8_t *)rnd->str); 
    RETURN end_shared_string(rnd); 
  } 
 
  /*! @decl string(0..255) get_seed() 
   *!   Returns part of the internal state so that it can be saved for 
   *!   later seeding. This method is deprecated. Instead read the 
   *!   @[min_seed_size] number of bytes from the @[random_string] 
   *!   method. 
   *! 
   *! @seealso 
   *!   @[seed()], @[random_string()] 
   */ 
  PIKEFUN string(0..255) get_seed() 
    optflags OPT_EXTERNAL_DEPEND; 
    rawtype tDeprecated(tFunc(tNone, tStr8)); 
  { 
    push_int(YARROW256_SEED_FILE_SIZE); 
    f_Nettle_Yarrow_random_string(1); 
  } 
 
  INIT 
  { 
    THIS->sources = NULL; 
    yarrow256_init(&THIS->ctx, 0, NULL); 
  } 
 
  EXIT 
    gc_trivial; 
  { 
    if( THIS->sources ) 
    { 
      free(THIS->sources); 
    } 
  } 
} 
 
/*! @endclass 
 */ 
 
#define INCREMENT(size, ctr)                    \ 
  do {                                          \ 
    unsigned increment_i = (size) - 1;          \ 
    if (++(ctr)[increment_i] == 0)              \ 
      while (increment_i > 0                    \ 
             && ++(ctr)[--increment_i] == 0 )   \ 
        ;                                       \ 
  } while (0) 
 
/*! @class Fortuna 
 *! 
 *! Implements the Fortuna PRNG generator, designed by Niels Ferguson and 
 *! Bruce Schneier and described in Practical Cryptography. Web 
 *! published exerpt at https://www.schneier.com:443/fortuna.pdf 
 *! 
 *! This implementation uses AES256 to generate output and SHA256 to 
 *! generate keys. 
 *! 
 *! To use this class an entropy accumulator needs to be implemented 
 *! and supply the @[reseed()] method with new entopy. 
 */ 
PIKECLASS Fortuna 
program_flags PROGRAM_CLEAR_STORAGE; 
{ 
  CVAR struct aes_ctx aes_ctx; 
  CVAR struct sha256_ctx sha_ctx; 
  CVAR uint8_t *key; 
  CVAR uint8_t *ctr; 
  CVAR uint8_t *data; 
 
  DECLARE_STORAGE; 
 
#ifndef AES256_KEY_SIZE 
#define AES256_KEY_SIZE (256>>3) 
#endif 
 
  static void fortuna_generate(void) 
  { 
    aes_encrypt(&THIS->aes_ctx, 16, THIS->data, THIS->ctr); 
    INCREMENT(16, THIS->ctr); 
  } 
 
  static void fortuna_rekey(void) 
  { 
    fortuna_generate(); 
    memcpy(THIS->key, THIS->data, 16); 
    fortuna_generate(); 
    memcpy(THIS->key+16, THIS->data, 16); 
    aes_set_encrypt_key(&THIS->aes_ctx, AES256_KEY_SIZE, THIS->key); 
  } 
 
  /*! @decl void reseed(string(8bit) data) 
   *! Generates new a new key based on the provided additional 
   *! entropy. 
   */ 
  PIKEFUN void reseed(string(8bit) data) 
  { 
    sha256_update(&THIS->sha_ctx, 32, THIS->key); 
    sha256_update(&THIS->sha_ctx, data->len, (const uint8_t *)data->str); 
    sha256_digest(&THIS->sha_ctx, 32, THIS->key); 
    aes_set_encrypt_key(&THIS->aes_ctx, AES256_KEY_SIZE, THIS->key); 
    INCREMENT(16, THIS->ctr); 
  } 
 
  /*! @decl string(8bit) random_string(int(0..) len) 
   *! 
   *! Generates @[len] amount of pseudo random data. In contrast with 
   *! the Fortuna PseudoRandomData function, which only allows 2^20 
   *! bytes of random data per call, the necessary rekey operations 
   *! are here performed internally, so no such restrictions apply. 
   */ 
  PIKEFUN string(8bit) random_string(int len) 
  { 
    int stored = 0; 
    struct string_builder s; 
 
    if(len<0) Pike_error("Length has to be positive.\n"); 
    init_string_builder_alloc(&s, len+16, 0); 
 
    while( stored < len ) 
    { 
      fortuna_generate(); 
      string_builder_binary_strcat(&s, (const char *)THIS->data, 
                                   MINIMUM(16, (len-stored))); 
 
      /* This should really be MINIMUM(16, (len-stored)) instead of 
         16, but it is only less than 16 in the last round, so it 
         doesn't matter if we rekey here or not. */ 
      stored += 16; 
 
      if( !(stored % (1<<20)) ) 
        fortuna_rekey(); 
    } 
 
    /* Inverse of the above conditional, to avoid having fortuna_rekey 
       applied twice in the rare condition that the string length is a 
       multiple of 1<<20. */ 
    if( (stored % (1<<20)) ) 
      fortuna_rekey(); 
 
    RETURN finish_string_builder(&s); 
  } 
 
  INIT 
  { 
    THIS->ctr = xcalloc(1,16); 
    THIS->key = xcalloc(1,32); 
    aes_set_encrypt_key(&THIS->aes_ctx, AES256_KEY_SIZE, THIS->key); 
    sha256_init(&THIS->sha_ctx); 
    THIS->data = xalloc(16); 
  } 
 
  EXIT 
    gc_trivial; 
  { 
    free(THIS->ctr); 
    free(THIS->key); 
    free(THIS->data); 
  } 
} 
 
/*! @endclass 
 */ 
 
/*! @decl int(0..) rsa_unpad(string(0..255) data, int type) 
 *! 
 *! Unpads a message that has been padded according to 
 *! RSAES-PKCS1-V1_5-ENCODE(message) in PKCS#1 v2.2. The padding 
 *! method used on the original message must be provided in the 
 *! @[type] parameter. All content dependent processing is done in 
 *! constant time for the same padding type and @[data] length. 
 */ 
PIKEFUN int rsa_unpad(string(0..255) data, int type) 
{ 
  int i, pad=0, nonpad=0, pos=0; 
  unsigned char *str; 
 
  NO_WIDE_STRING(data); 
 
  /* Indata is smaller than minimum size, so we can exit immediately 
     without timing issue. 1 type + 8 padding + 1 delimiter + 1 value 
     = 11 bytes. */ 
  if(data->len < 11 ) RETURN 0; 
  str = (unsigned char*)data->str + data->len - 1; 
 
  for(i=data->len-1; i>0; i--,str--) 
  { 
    switch(*str) 
    { 
    case 0:     pos=i; break; 
    case 0xff:  pad=i; break; 
    default: nonpad=i; break; 
    } 
  } 
 
  if( type==2 ) 
  { 
    nonpad=pos+1; 
    pad=1; 
  } 
 
  if( (pad==1) + (nonpad>pos) + (*str==type) + (pos>8) == 4 ) 
    RETURN pos+1; 
  RETURN 0; 
} 
 
 
/*! @decl string(0..127) crypt_md5(string(0..255) password, @ 
 *!                                string(0..255) salt,@ 
 *!                                void|string(0..255) magic) 
 *! Does the crypt_md5 abrakadabra (MD5 + snakeoil). It is assumed 
 *! that @[salt] does not contain "$". 
 *! 
 *! The @[password] memory will be cleared before released. 
 */ 
PIKEFUN string(0..127) crypt_md5(string pw, string salt, 
                                 void|string magic) 
  optflags OPT_TRY_OPTIMIZE; 
  /* NB: We use a weaker type above to allow us to delay 
   *     throwing errors on wide strings until we've had 
   *     time to censor the password string. 
   */ 
  rawtype tFunc(tStr8 tStr8 tOr(tStr8, tVoid), tStr7); 
{ 
  char *hash; 
 
  /* Censor the password. */ 
  push_string(pw); 
  args++; 
  add_ref(Pike_sp[-args].u.string = MK_STRING("censored")); 
 
  NO_WIDE_STRING(pw); 
  NO_WIDE_STRING(salt); 
 
  pw->flags |= STRING_CLEAR_ON_EXIT; 
 
  if(!magic) 
  { 
    hash = pike_crypt_md5(pw->len, pw->str, salt->len, salt->str, 
                          3, "$1$"); 
  } 
  else 
  { 
    NO_WIDE_STRING(magic); 
    hash = pike_crypt_md5(pw->len, pw->str, salt->len, salt->str, 
                          magic->len, magic->str); 
  } 
 
  push_text(hash); 
} 
 
/*! @endmodule 
 */ 
 
#endif /* HAVE_LIBNETTLE */ 
 
PIKE_MODULE_INIT 
{ 
#ifdef __NT__ 
  struct program *nt_program = NULL; 
  struct object *nt_object = NULL; 
#endif /* __NT__ */ 
  INIT; 
#ifdef HAVE_LIBNETTLE 
  hash_init(); 
  mac_init(); 
  cipher_init(); 
  aead_init(); 
#endif /* HAVE_LIBNETTLE */ 
#ifdef __NT__ 
  start_new_program(); 
  nt_init(); 
  nt_program = end_program(); 
  add_object_constant("NT", nt_object=clone_object(nt_program,0), 0); 
  free_object(nt_object); 
  free_program(nt_program); 
#endif /* __NT__ */ 
#ifdef HAVE_LIBHOGWEED 
  hogweed_init(); 
#endif 
} 
 
PIKE_MODULE_EXIT 
{ 
#ifdef HAVE_LIBNETTLE 
  aead_exit(); 
  cipher_exit(); 
  mac_exit(); 
  hash_exit(); 
#endif /* HAVE_LIBNETTLE */ 
#ifdef __NT__ 
  nt_exit(); 
#endif /* __NT__ */ 
#ifdef HAVE_LIBHOGWEED 
  hogweed_exit(); 
#endif 
  EXIT; 
}