src/pbkdf2.cpp
// Copyright (c) 2013 NovaCoin Developers
#include <string.h>
#include "pbkdf2.h"
static inline uint32_t
be32dec(const void *pp)
{
const uint8_t *p = (uint8_t const *)pp;
return ((uint32_t)(p[3]) + ((uint32_t)(p[2]) << 8) +
((uint32_t)(p[1]) << 16) + ((uint32_t)(p[0]) << 24));
}
static inline void
be32enc(void *pp, uint32_t x)
{
uint8_t * p = (uint8_t *)pp;
p[3] = x & 0xff;
p[2] = (x >> 8) & 0xff;
p[1] = (x >> 16) & 0xff;
p[0] = (x >> 24) & 0xff;
}
/* Initialize an HMAC-SHA256 operation with the given key. */
void
HMAC_SHA256_Init(HMAC_SHA256_CTX * ctx, const void * _K, size_t Klen)
{
unsigned char pad[64];
unsigned char khash[32];
const unsigned char * K = (const unsigned char *)_K;
size_t i;
/* If Klen > 64, the key is really SHA256(K). */
if (Klen > 64) {
SHA256_Init(&ctx->ictx);
SHA256_Update(&ctx->ictx, K, Klen);
SHA256_Final(khash, &ctx->ictx);
K = khash;
Klen = 32;
}
/* Inner SHA256 operation is SHA256(K xor [block of 0x36] || data). */
SHA256_Init(&ctx->ictx);
memset(pad, 0x36, 64);
for (i = 0; i < Klen; i++)
pad[i] ^= K[i];
SHA256_Update(&ctx->ictx, pad, 64);
/* Outer SHA256 operation is SHA256(K xor [block of 0x5c] || hash). */
SHA256_Init(&ctx->octx);
memset(pad, 0x5c, 64);
for (i = 0; i < Klen; i++)
pad[i] ^= K[i];
SHA256_Update(&ctx->octx, pad, 64);
/* Clean the stack. */
memset(khash, 0, 32);
}
/* Add bytes to the HMAC-SHA256 operation. */
void
HMAC_SHA256_Update(HMAC_SHA256_CTX * ctx, const void *in, size_t len)
{
/* Feed data to the inner SHA256 operation. */
SHA256_Update(&ctx->ictx, in, len);
}
/* Finish an HMAC-SHA256 operation. */
void
HMAC_SHA256_Final(unsigned char digest[32], HMAC_SHA256_CTX * ctx)
{
unsigned char ihash[32];
/* Finish the inner SHA256 operation. */
SHA256_Final(ihash, &ctx->ictx);
/* Feed the inner hash to the outer SHA256 operation. */
SHA256_Update(&ctx->octx, ihash, 32);
/* Finish the outer SHA256 operation. */
SHA256_Final(digest, &ctx->octx);
/* Clean the stack. */
memset(ihash, 0, 32);
}
/**
* PBKDF2_SHA256(passwd, passwdlen, salt, saltlen, c, buf, dkLen):
* Compute PBKDF2(passwd, salt, c, dkLen) using HMAC-SHA256 as the PRF, and
* write the output to buf. The value dkLen must be at most 32 * (2^32 - 1).
*/
void
PBKDF2_SHA256(const uint8_t * passwd, size_t passwdlen, const uint8_t * salt,
size_t saltlen, uint64_t c, uint8_t * buf, size_t dkLen)
{
HMAC_SHA256_CTX PShctx, hctx;
size_t i;
uint8_t ivec[4];
uint8_t U[32];
uint8_t T[32];
uint64_t j;
int k;
size_t clen;
/* Compute HMAC state after processing P and S. */
HMAC_SHA256_Init(&PShctx, passwd, passwdlen);
HMAC_SHA256_Update(&PShctx, salt, saltlen);
/* Iterate through the blocks. */
for (i = 0; i * 32 < dkLen; i++) {
/* Generate INT(i + 1). */
be32enc(ivec, (uint32_t)(i + 1));
/* Compute U_1 = PRF(P, S || INT(i)). */
memcpy(&hctx, &PShctx, sizeof(HMAC_SHA256_CTX));
HMAC_SHA256_Update(&hctx, ivec, 4);
HMAC_SHA256_Final(U, &hctx);
/* T_i = U_1 ... */
memcpy(T, U, 32);
for (j = 2; j <= c; j++) {
/* Compute U_j. */
HMAC_SHA256_Init(&hctx, passwd, passwdlen);
HMAC_SHA256_Update(&hctx, U, 32);
HMAC_SHA256_Final(U, &hctx);
/* ... xor U_j ... */
for (k = 0; k < 32; k++)
T[k] ^= U[k];
}
/* Copy as many bytes as necessary into buf. */
clen = dkLen - i * 32;
if (clen > 32)
clen = 32;
memcpy(&buf[i * 32], T, clen);
}
/* Clean PShctx, since we never called _Final on it. */
memset(&PShctx, 0, sizeof(HMAC_SHA256_CTX));
}