/* 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.
*/
/* the idea of re-keying loosely follows the approach used in:
* http://bxr.su/OpenBSD/lib/libc/crypt/arc4random.c
*/
#include "tomcrypt.h"
#ifdef LTC_CHACHA20_PRNG
const struct ltc_prng_descriptor chacha20_prng_desc =
{
"chacha20",
40,
&chacha20_prng_start,
&chacha20_prng_add_entropy,
&chacha20_prng_ready,
&chacha20_prng_read,
&chacha20_prng_done,
&chacha20_prng_export,
&chacha20_prng_import,
&chacha20_prng_test
};
/**
Start the PRNG
@param prng The PRNG state to initialize
@return CRYPT_OK if successful
*/
int chacha20_prng_start(prng_state *prng)
{
LTC_ARGCHK(prng != NULL);
prng->ready = 0;
XMEMSET(&prng->chacha.ent, 0, sizeof(prng->chacha.ent));
prng->chacha.idx = 0;
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 chacha20_prng_add_entropy(const unsigned char *in, unsigned long inlen, prng_state *prng)
{
unsigned char buf[40];
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) {
/* chacha20_prng_ready() was already called, do "rekey" operation */
if ((err = chacha_keystream(&prng->chacha.s, buf, sizeof(buf))) != CRYPT_OK) goto LBL_UNLOCK;
for(i = 0; i < inlen; i++) buf[i % sizeof(buf)] ^= in[i];
/* key 32 bytes, 20 rounds */
if ((err = chacha_setup(&prng->chacha.s, buf, 32, 20)) != CRYPT_OK) goto LBL_UNLOCK;
/* iv 8 bytes */
if ((err = chacha_ivctr64(&prng->chacha.s, buf + 32, 8, 0)) != CRYPT_OK) goto LBL_UNLOCK;
/* clear KEY + IV */
zeromem(buf, sizeof(buf));
}
else {
/* chacha20_prng_ready() was not called yet, add entropy to ent buffer */
while (inlen--) prng->chacha.ent[prng->chacha.idx++ % sizeof(prng->chacha.ent)] ^= *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 chacha20_prng_ready(prng_state *prng)
{
int err;
LTC_ARGCHK(prng != NULL);
LTC_MUTEX_LOCK(&prng->lock);
if (prng->ready) { err = CRYPT_OK; goto LBL_UNLOCK; }
/* key 32 bytes, 20 rounds */
if ((err = chacha_setup(&prng->chacha.s, prng->chacha.ent, 32, 20)) != CRYPT_OK) goto LBL_UNLOCK;
/* iv 8 bytes */
if ((err = chacha_ivctr64(&prng->chacha.s, prng->chacha.ent + 32, 8, 0)) != CRYPT_OK) goto LBL_UNLOCK;
XMEMSET(&prng->chacha.ent, 0, sizeof(prng->chacha.ent));
prng->chacha.idx = 0;
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 chacha20_prng_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 (chacha_keystream(&prng->chacha.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 chacha20_prng_done(prng_state *prng)
{
int err;
LTC_ARGCHK(prng != NULL);
LTC_MUTEX_LOCK(&prng->lock);
prng->ready = 0;
err = chacha_done(&prng->chacha.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 chacha20_prng_export(unsigned char *out, unsigned long *outlen, prng_state *prng)
{
unsigned long len = chacha20_prng_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 (chacha20_prng_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 chacha20_prng_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)chacha20_prng_desc.export_size) return CRYPT_INVALID_ARG;
if ((err = chacha20_prng_start(prng)) != CRYPT_OK) return err;
if ((err = chacha20_prng_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 chacha20_prng_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[300];
unsigned long dmplen = sizeof(dmp);
unsigned char out[500];
unsigned char t1[] = { 0x59, 0xB2, 0x26, 0x95, 0x2B, 0x01, 0x8F, 0x05, 0xBE, 0xD8 };
unsigned char t2[] = { 0x47, 0xC9, 0x0D, 0x03, 0xE4, 0x75, 0x34, 0x27, 0xBD, 0xDE };
unsigned char t3[] = { 0xBC, 0xFA, 0xEF, 0x59, 0x37, 0x7F, 0x1A, 0x91, 0x1A, 0xA6 };
int err;
if ((err = chacha20_prng_start(&st)) != CRYPT_OK) return err;
/* add entropy to uninitialized prng */
if ((err = chacha20_prng_add_entropy(en, sizeof(en), &st)) != CRYPT_OK) return err;
if ((err = chacha20_prng_ready(&st)) != CRYPT_OK) return err;
if (chacha20_prng_read(out, 10, &st) != 10) return CRYPT_ERROR_READPRNG; /* 10 bytes for testing */
if (compare_testvector(out, 10, t1, sizeof(t1), "CHACHA-PRNG", 1)) return CRYPT_FAIL_TESTVECTOR;
if (chacha20_prng_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
/* add entropy to already initialized prng */
if ((err = chacha20_prng_add_entropy(en, sizeof(en), &st)) != CRYPT_OK) return err;
if (chacha20_prng_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
if ((err = chacha20_prng_export(dmp, &dmplen, &st)) != CRYPT_OK) return err;
if (chacha20_prng_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
if (chacha20_prng_read(out, 10, &st) != 10) return CRYPT_ERROR_READPRNG; /* 10 bytes for testing */
if (compare_testvector(out, 10, t2, sizeof(t2), "CHACHA-PRNG", 2)) return CRYPT_FAIL_TESTVECTOR;
if ((err = chacha20_prng_done(&st)) != CRYPT_OK) return err;
if ((err = chacha20_prng_import(dmp, dmplen, &st)) != CRYPT_OK) return err;
if ((err = chacha20_prng_ready(&st)) != CRYPT_OK) return err;
if (chacha20_prng_read(out, 500, &st) != 500) return CRYPT_ERROR_READPRNG; /* skip 500 bytes */
if (chacha20_prng_read(out, 10, &st) != 10) return CRYPT_ERROR_READPRNG; /* 10 bytes for testing */
if (compare_testvector(out, 10, t3, sizeof(t3), "CHACHA-PRNG", 3)) return CRYPT_FAIL_TESTVECTOR;
if ((err = chacha20_prng_done(&st)) != CRYPT_OK) return err;
return CRYPT_OK;
#endif
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */