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dropbear/libtomcrypt/src/prngs/rc4.c

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/* 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.
*/
#include "tomcrypt.h"
/**
@file prngs/rc4.c
RC4 PRNG, Tom St Denis
*/
#ifdef LTC_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);
prng->ready = 0;
/* set entropy (key) size to zero */
prng->rc4.s.x = 0;
/* clear entropy (key) buffer */
XMEMSET(&prng->rc4.s.buf, 0, sizeof(prng->rc4.s.buf));
LTC_MUTEX_INIT(&prng->lock)
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)
{
unsigned char buf[256];
unsigned long i;
int err;
LTC_ARGCHK(prng != NULL);
LTC_ARGCHK(in != NULL);
LTC_ARGCHK(inlen > 0);
LTC_MUTEX_LOCK(&prng->lock);
if (prng->ready) {
/* rc4_ready() was already called, do "rekey" operation */
if ((err = rc4_stream_keystream(&prng->rc4.s, buf, sizeof(buf))) != CRYPT_OK) goto LBL_UNLOCK;
for(i = 0; i < inlen; i++) buf[i % sizeof(buf)] ^= in[i];
/* initialize RC4 */
if ((err = rc4_stream_setup(&prng->rc4.s, buf, sizeof(buf))) != CRYPT_OK) goto LBL_UNLOCK;
/* drop first 3072 bytes - https://en.wikipedia.org/wiki/RC4#Fluhrer.2C_Mantin_and_Shamir_attack */
for (i = 0; i < 12; i++) rc4_stream_keystream(&prng->rc4.s, buf, sizeof(buf));
zeromem(buf, sizeof(buf));
}
else {
/* rc4_ready() was not called yet, add entropy to the buffer */
while (inlen--) prng->rc4.s.buf[prng->rc4.s.x++ % sizeof(prng->rc4.s.buf)] ^= *in++;
}
err = CRYPT_OK;
LBL_UNLOCK:
LTC_MUTEX_UNLOCK(&prng->lock);
return err;
}
/**
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 buf[256] = { 0 };
unsigned long len;
int err, i;
LTC_ARGCHK(prng != NULL);
LTC_MUTEX_LOCK(&prng->lock);
if (prng->ready) { err = CRYPT_OK; goto LBL_UNLOCK; }
XMEMCPY(buf, prng->rc4.s.buf, sizeof(buf));
/* initialize RC4 */
len = MIN(prng->rc4.s.x, 256); /* TODO: we can perhaps always use all 256 bytes */
if ((err = rc4_stream_setup(&prng->rc4.s, buf, len)) != CRYPT_OK) goto LBL_UNLOCK;
/* drop first 3072 bytes - https://en.wikipedia.org/wiki/RC4#Fluhrer.2C_Mantin_and_Shamir_attack */
for (i = 0; i < 12; i++) rc4_stream_keystream(&prng->rc4.s, buf, sizeof(buf));
prng->ready = 1;
LBL_UNLOCK:
LTC_MUTEX_UNLOCK(&prng->lock);
return err;
}
/**
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)
{
if (outlen == 0 || prng == NULL || out == NULL) return 0;
LTC_MUTEX_LOCK(&prng->lock);
if (!prng->ready) { outlen = 0; goto LBL_UNLOCK; }
if (rc4_stream_keystream(&prng->rc4.s, out, outlen) != CRYPT_OK) outlen = 0;
LBL_UNLOCK:
LTC_MUTEX_UNLOCK(&prng->lock);
return outlen;
}
/**
Terminate the PRNG
@param prng The PRNG to terminate
@return CRYPT_OK if successful
*/
int rc4_done(prng_state *prng)
{
int err;
LTC_ARGCHK(prng != NULL);
LTC_MUTEX_LOCK(&prng->lock);
prng->ready = 0;
err = rc4_stream_done(&prng->rc4.s);
LTC_MUTEX_UNLOCK(&prng->lock);
LTC_MUTEX_DESTROY(&prng->lock);
return err;
}
/**
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)
{
unsigned long len = rc4_desc.export_size;
LTC_ARGCHK(prng != NULL);
LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL);
if (*outlen < len) {
*outlen = len;
return CRYPT_BUFFER_OVERFLOW;
}
if (rc4_read(out, len, prng) != len) {
return CRYPT_ERROR_READPRNG;
}
*outlen = len;
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(prng != NULL);
LTC_ARGCHK(in != NULL);
if (inlen < (unsigned long)rc4_desc.export_size) return CRYPT_INVALID_ARG;
if ((err = rc4_start(prng)) != CRYPT_OK) return err;
if ((err = rc4_add_entropy(in, inlen, prng)) != CRYPT_OK) return err;
return CRYPT_OK;
}
/**
PRNG self-test
@return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled
*/
int rc4_test(void)
{
#ifndef LTC_TEST
return CRYPT_NOP;
#else
prng_state st;
unsigned char en[] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a,
0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14,
0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e,
0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32 };
unsigned char dmp[500];
unsigned long dmplen = sizeof(dmp);
unsigned char out[1000];
unsigned char t1[] = { 0xE0, 0x4D, 0x9A, 0xF6, 0xA8, 0x9D, 0x77, 0x53, 0xAE, 0x09 };
unsigned char t2[] = { 0xEF, 0x80, 0xA2, 0xE6, 0x50, 0x91, 0xF3, 0x17, 0x4A, 0x8A };
unsigned char t3[] = { 0x4B, 0xD6, 0x5C, 0x67, 0x99, 0x03, 0x56, 0x12, 0x80, 0x48 };
int err;
if ((err = rc4_start(&st)) != CRYPT_OK) return err;
/* add entropy to uninitialized prng */
if ((err = rc4_add_entropy(en, sizeof(en), &st)) != CRYPT_OK) return err;
if ((err = rc4_ready(&st)) != CRYPT_OK) return err;
if (rc4_read(out, 10, &st) != 10) return CRYPT_ERROR_READPRNG; /* 10 bytes for testing */
if (compare_testvector(out, 10, t1, sizeof(t1), "RC4-PRNG", 1)) return CRYPT_FAIL_TESTVECTOR;
if (rc4_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
/* add entropy to already initialized prng */
if ((err = rc4_add_entropy(en, sizeof(en), &st)) != CRYPT_OK) return err;
if (rc4_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
if ((err = rc4_export(dmp, &dmplen, &st)) != CRYPT_OK) return err;
if (rc4_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
if (rc4_read(out, 10, &st) != 10) return CRYPT_ERROR_READPRNG; /* 10 bytes for testing */
if (compare_testvector(out, 10, t2, sizeof(t2), "RC4-PRNG", 2)) return CRYPT_FAIL_TESTVECTOR;
if ((err = rc4_done(&st)) != CRYPT_OK) return err;
if ((err = rc4_import(dmp, dmplen, &st)) != CRYPT_OK) return err;
if ((err = rc4_ready(&st)) != CRYPT_OK) return err;
if (rc4_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
if (rc4_read(out, 10, &st) != 10) return CRYPT_ERROR_READPRNG; /* 10 bytes for testing */
if (compare_testvector(out, 10, t3, sizeof(t3), "RC4-PRNG", 3)) return CRYPT_FAIL_TESTVECTOR;
if ((err = rc4_done(&st)) != CRYPT_OK) return err;
return CRYPT_OK;
#endif
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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