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/* crypto/rsa/rsa_oaep.c */
/* Written by Ulf Moeller. This software is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. */
/* EME_OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
#include <stdio.h>
#include "cryptlib.h"
#include "bn.h"
#include "rsa.h"
#include "sha.h"
#include "rand.h"
int MGF1(unsigned char *mask, long len, unsigned char *seed, long seedlen);
int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
unsigned char *from, int flen, unsigned char *param, int plen)
{
int i, emlen = tlen - 1;
unsigned char *db, *seed;
unsigned char *dbmask, seedmask[SHA_DIGEST_LENGTH];
if (flen > emlen - 2 * SHA_DIGEST_LENGTH - 1)
{
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP,
RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
return (0);
}
if (emlen < 2 * SHA_DIGEST_LENGTH + 1)
{
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_KEY_SIZE_TOO_SMALL);
return (0);
}
dbmask = Malloc(emlen - SHA_DIGEST_LENGTH);
if (dbmask == NULL)
{
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
return (0);
}
to[0] = 0;
seed = to + 1;
db = to + SHA_DIGEST_LENGTH + 1;
SHA1(param, plen, db);
memset(db + SHA_DIGEST_LENGTH, 0,
emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int) flen);
RAND_bytes(seed, SHA_DIGEST_LENGTH);
#ifdef PKCS_TESTVECT
memcpy(seed,
"\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
20);
#endif
MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH);
for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
db[i] ^= dbmask[i];
MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH);
for (i = 0; i < SHA_DIGEST_LENGTH; i++)
seed[i] ^= seedmask[i];
Free(dbmask);
return (1);
}
int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
unsigned char *from, int flen, int num, unsigned char *param,
int plen)
{
int i, dblen, mlen = -1;
unsigned char *maskeddb;
unsigned char *db, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
if (flen < 2 * SHA_DIGEST_LENGTH + 1)
{
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
return (-1);
}
dblen = flen - SHA_DIGEST_LENGTH;
db = Malloc(dblen);
if (db == NULL)
{
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
return (-1);
}
maskeddb = from + SHA_DIGEST_LENGTH;
MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
for (i = 0; i < SHA_DIGEST_LENGTH; i++)
seed[i] ^= from[i];
MGF1(db, dblen, seed, SHA_DIGEST_LENGTH);
for (i = 0; i < dblen; i++)
db[i] ^= maskeddb[i];
SHA1(param, plen, phash);
if (memcmp(db, phash, SHA_DIGEST_LENGTH) != 0)
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
else
{
for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
if (db[i] != 0x00)
break;
if (db[i] != 0x01 || i++ >= dblen)
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP,
RSA_R_OAEP_DECODING_ERROR);
else
{
mlen = dblen - i;
if (tlen < mlen)
{
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
mlen = -1;
}
else
memcpy(to, db + i, mlen);
}
}
Free(db);
return (mlen);
}
int MGF1(unsigned char *mask, long len, unsigned char *seed, long seedlen)
{
long i, outlen = 0;
unsigned char cnt[4];
SHA_CTX c;
unsigned char md[SHA_DIGEST_LENGTH];
for (i = 0; outlen < len; i++)
{
cnt[0] = (i >> 24) & 255, cnt[1] = (i >> 16) & 255,
cnt[2] = (i >> 8) & 255, cnt[3] = i & 255;
SHA1_Init(&c);
SHA1_Update(&c, seed, seedlen);
SHA1_Update(&c, cnt, 4);
if (outlen + SHA_DIGEST_LENGTH <= len)
{
SHA1_Final(mask + outlen, &c);
outlen += SHA_DIGEST_LENGTH;
}
else
{
SHA1_Final(md, &c);
memcpy(mask + outlen, md, len - outlen);
outlen = len;
}
}
return (0);
}
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