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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.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
*/
#include "tomcrypt.h"
/**
@file rng_get_bytes.c
portable way to get secure random bits to feed a PRNG (Tom St Denis)
*/
#ifdef DEVRANDOM
/* on *NIX read /dev/random */
static unsigned long rng_nix(unsigned char *buf, unsigned long len,
void (*callback)(void))
{
#ifdef LTC_NO_FILE
return 0;
#else
FILE *f;
unsigned long x;
#ifdef TRY_URANDOM_FIRST
f = fopen("/dev/urandom", "rb");
if (f == NULL)
#endif /* TRY_URANDOM_FIRST */
f = fopen("/dev/random", "rb");
if (f == NULL) {
return 0;
}
/* disable buffering */
if (setvbuf(f, NULL, _IONBF, 0) != 0) {
fclose(f);
return 0;
}
x = (unsigned long)fread(buf, 1, (size_t)len, f);
fclose(f);
return x;
#endif /* LTC_NO_FILE */
}
#endif /* DEVRANDOM */
/* on ANSI C platforms with 100 < CLOCKS_PER_SEC < 10000 */
#if defined(CLOCKS_PER_SEC)
#define ANSI_RNG
static unsigned long rng_ansic(unsigned char *buf, unsigned long len,
void (*callback)(void))
{
clock_t t1;
int l, acc, bits, a, b;
if (XCLOCKS_PER_SEC < 100 || XCLOCKS_PER_SEC > 10000) {
return 0;
}
l = len;
bits = 8;
acc = a = b = 0;
while (len--) {
if (callback != NULL) callback();
while (bits--) {
do {
t1 = XCLOCK(); while (t1 == XCLOCK()) a ^= 1;
t1 = XCLOCK(); while (t1 == XCLOCK()) b ^= 1;
} while (a == b);
acc = (acc << 1) | a;
}
*buf++ = acc;
acc = 0;
bits = 8;
}
acc = bits = a = b = 0;
return l;
}
#endif
/* Try the Microsoft CSP */
#ifdef WIN32
#define _WIN32_WINNT 0x0400
#include <windows.h>
#include <wincrypt.h>
static unsigned long rng_win32(unsigned char *buf, unsigned long len,
void (*callback)(void))
{
HCRYPTPROV hProv = 0;
if (!CryptAcquireContext(&hProv, NULL, MS_DEF_PROV, PROV_RSA_FULL,
(CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET)) &&
!CryptAcquireContext (&hProv, NULL, MS_DEF_PROV, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET | CRYPT_NEWKEYSET))
return 0;
if (CryptGenRandom(hProv, len, buf) == TRUE) {
CryptReleaseContext(hProv, 0);
return len;
} else {
CryptReleaseContext(hProv, 0);
return 0;
}
}
#endif /* WIN32 */
/**
Read the system RNG
@param out Destination
@param outlen Length desired (octets)
@param callback Pointer to void function to act as "callback" when RNG is slow. This can be NULL
@return Number of octets read
*/
unsigned long rng_get_bytes(unsigned char *out, unsigned long outlen,
void (*callback)(void))
{
unsigned long x;
LTC_ARGCHK(out != NULL);
#if defined(DEVRANDOM)
x = rng_nix(out, outlen, callback); if (x != 0) { return x; }
#endif
#ifdef WIN32
x = rng_win32(out, outlen, callback); if (x != 0) { return x; }
#endif
#ifdef ANSI_RNG
x = rng_ansic(out, outlen, callback); if (x != 0) { return x; }
#endif
return 0;
}
/* $Source: /cvs/libtom/libtomcrypt/src/prngs/rng_get_bytes.c,v $ */
/* $Revision: 1.3 $ */
/* $Date: 2005/05/05 14:35:59 $ */
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