view libtomcrypt/src/prngs/rc4.c @ 1156:a8f4dade70e5

avoid getpass when not used some systems (like android's bionic) do not provide getpass. you can disable ENABLE_CLI_PASSWORD_AUTH & ENABLE_CLI_INTERACT_AUTH to avoid its use (and rely on pubkey auth), but the link still fails because the support file calls getpass. do not define this func if both of those auth methods are not used.
author Mike Frysinger <vapier@gentoo.org>
date Wed, 21 Oct 2015 22:39:55 +0800
parents 0cbe8f6dbf9e
children f849a5ca2efc
line wrap: on
line source

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 * Tom St Denis, [email protected], http://libtomcrypt.com
 */
#include "tomcrypt.h"

/**
  @file rc4.c
  RC4 PRNG, Tom St Denis
*/  

#ifdef RC4

const struct ltc_prng_descriptor rc4_desc = 
{
   "rc4", 32,
    &rc4_start,
    &rc4_add_entropy,
    &rc4_ready,
    &rc4_read,
    &rc4_done,
    &rc4_export,
    &rc4_import,
    &rc4_test
};

/**
  Start the PRNG
  @param prng     [out] The PRNG state to initialize
  @return CRYPT_OK if successful
*/  
int rc4_start(prng_state *prng)
{
    LTC_ARGCHK(prng != NULL);

    /* set keysize to zero */
    prng->rc4.x = 0;
    
    return CRYPT_OK;
}

/**
  Add entropy to the PRNG state
  @param in       The data to add
  @param inlen    Length of the data to add
  @param prng     PRNG state to update
  @return CRYPT_OK if successful
*/  
int rc4_add_entropy(const unsigned char *in, unsigned long inlen, prng_state *prng)
{
    LTC_ARGCHK(in  != NULL);
    LTC_ARGCHK(prng != NULL);
 
    /* trim as required */
    if (prng->rc4.x + inlen > 256) {
       if (prng->rc4.x == 256) {
          /* I can't possibly accept another byte, ok maybe a mint wafer... */
          return CRYPT_OK;
       } else {
          /* only accept part of it */
          inlen = 256 - prng->rc4.x;
       }       
    }

    while (inlen--) {
       prng->rc4.buf[prng->rc4.x++] = *in++;
    }

    return CRYPT_OK;
    
}

/**
  Make the PRNG ready to read from
  @param prng   The PRNG to make active
  @return CRYPT_OK if successful
*/  
int rc4_ready(prng_state *prng)
{
    unsigned char key[256], tmp, *s;
    int keylen, x, y, j;

    LTC_ARGCHK(prng != NULL);

    /* extract the key */
    s = prng->rc4.buf;
    XMEMCPY(key, s, 256);
    keylen = prng->rc4.x;

    /* make RC4 perm and shuffle */
    for (x = 0; x < 256; x++) {
        s[x] = x;
    }

    for (j = x = y = 0; x < 256; x++) {
        y = (y + prng->rc4.buf[x] + key[j++]) & 255;
        if (j == keylen) {
           j = 0; 
        }
        tmp = s[x]; s[x] = s[y]; s[y] = tmp;
    }
    prng->rc4.x = 0;
    prng->rc4.y = 0;

#ifdef LTC_CLEAN_STACK
    zeromem(key, sizeof(key));
#endif

    return CRYPT_OK;
}

/**
  Read from the PRNG
  @param out      Destination
  @param outlen   Length of output
  @param prng     The active PRNG to read from
  @return Number of octets read
*/  
unsigned long rc4_read(unsigned char *out, unsigned long outlen, prng_state *prng)
{
   unsigned char x, y, *s, tmp;
   unsigned long n;

   LTC_ARGCHK(out != NULL);
   LTC_ARGCHK(prng != NULL);

#ifdef LTC_VALGRIND
   zeromem(out, outlen);
#endif

   n = outlen;
   x = prng->rc4.x;
   y = prng->rc4.y;
   s = prng->rc4.buf;
   while (outlen--) {
      x = (x + 1) & 255;
      y = (y + s[x]) & 255;
      tmp = s[x]; s[x] = s[y]; s[y] = tmp;
      tmp = (s[x] + s[y]) & 255;
      *out++ ^= s[tmp];
   }
   prng->rc4.x = x;
   prng->rc4.y = y;
   return n;
}

/**
  Terminate the PRNG
  @param prng   The PRNG to terminate
  @return CRYPT_OK if successful
*/  
int rc4_done(prng_state *prng)
{
   LTC_ARGCHK(prng != NULL);
   return CRYPT_OK;
}

/**
  Export the PRNG state
  @param out       [out] Destination
  @param outlen    [in/out] Max size and resulting size of the state
  @param prng      The PRNG to export
  @return CRYPT_OK if successful
*/  
int rc4_export(unsigned char *out, unsigned long *outlen, prng_state *prng)
{
   LTC_ARGCHK(outlen != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(prng   != NULL);

   if (*outlen < 32) {
      *outlen = 32;
      return CRYPT_BUFFER_OVERFLOW;
   }

   if (rc4_read(out, 32, prng) != 32) {
      return CRYPT_ERROR_READPRNG;
   }
   *outlen = 32;

   return CRYPT_OK;
}
 
/**
  Import a PRNG state
  @param in       The PRNG state
  @param inlen    Size of the state
  @param prng     The PRNG to import
  @return CRYPT_OK if successful
*/  
int rc4_import(const unsigned char *in, unsigned long inlen, prng_state *prng)
{
   int err;
   LTC_ARGCHK(in   != NULL);
   LTC_ARGCHK(prng != NULL);

   if (inlen != 32) {
      return CRYPT_INVALID_ARG;
   }
   
   if ((err = rc4_start(prng)) != CRYPT_OK) {
      return err;
   }
   return rc4_add_entropy(in, 32, prng);
}

/**
  PRNG self-test
  @return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled
*/  
int rc4_test(void)
{
#if !defined(LTC_TEST) || defined(LTC_VALGRIND)
   return CRYPT_NOP;
#else
   static const struct {
      unsigned char key[8], pt[8], ct[8];
   } tests[] = {
{
   { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef },
   { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef },
   { 0x75, 0xb7, 0x87, 0x80, 0x99, 0xe0, 0xc5, 0x96 }
}
};
   prng_state prng;
   unsigned char dst[8];
   int err, x;

   for (x = 0; x < (int)(sizeof(tests)/sizeof(tests[0])); x++) {
       if ((err = rc4_start(&prng)) != CRYPT_OK) {
          return err;
       }
       if ((err = rc4_add_entropy(tests[x].key, 8, &prng)) != CRYPT_OK) {
          return err;
       }
       if ((err = rc4_ready(&prng)) != CRYPT_OK) {
          return err;
       }
       XMEMCPY(dst, tests[x].pt, 8);
       if (rc4_read(dst, 8, &prng) != 8) {
          return CRYPT_ERROR_READPRNG;
       }
       rc4_done(&prng);
       if (XMEMCMP(dst, tests[x].ct, 8)) {
#if 0
          int y;
          printf("\n\nRC4 failed, I got:\n"); 
          for (y = 0; y < 8; y++) printf("%02x ", dst[y]);
          printf("\n");
#endif
          return CRYPT_FAIL_TESTVECTOR;
       }
   }
   return CRYPT_OK;
#endif
}

#endif


/* $Source: /cvs/libtom/libtomcrypt/src/prngs/rc4.c,v $ */
/* $Revision: 1.9 $ */
/* $Date: 2006/11/16 00:32:18 $ */