236 lines
6.1 KiB
C
236 lines
6.1 KiB
C
/* crypto/rsa/rsa_oaep.c */
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/* Written by Ulf Moeller. This software is distributed on an "AS IS"
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basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. */
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/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
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/* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
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* <URL: http://www.shoup.net/papers/oaep.ps.Z>
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* for problems with the security proof for the
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* original OAEP scheme, which EME-OAEP is based on.
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*
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* A new proof can be found in E. Fujisaki, T. Okamoto,
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* D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
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* Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
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* The new proof has stronger requirements for the
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* underlying permutation: "partial-one-wayness" instead
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* of one-wayness. For the RSA function, this is
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* an equivalent notion.
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*/
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#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
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#include <stdio.h>
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#include "cryptlib.h"
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#include <openssl/bn.h>
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#include <openssl/rsa.h>
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#include <openssl/evp.h>
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#include <openssl/rand.h>
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#include <openssl/sha.h>
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static int MGF1(unsigned char *mask, long len,
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const unsigned char *seed, long seedlen);
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int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
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const unsigned char *from, int flen,
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const unsigned char *param, int plen)
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{
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int i, emlen = tlen - 1;
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unsigned char *db, *seed;
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unsigned char *dbmask, seedmask[SHA_DIGEST_LENGTH];
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if (flen > emlen - 2 * SHA_DIGEST_LENGTH - 1)
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{
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RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP,
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RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
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return 0;
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}
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if (emlen < 2 * SHA_DIGEST_LENGTH + 1)
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{
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RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_KEY_SIZE_TOO_SMALL);
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return 0;
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}
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to[0] = 0;
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seed = to + 1;
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db = to + SHA_DIGEST_LENGTH + 1;
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if (!EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL))
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return 0;
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memset(db + SHA_DIGEST_LENGTH, 0,
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emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
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db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
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memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int) flen);
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if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0)
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return 0;
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#ifdef PKCS_TESTVECT
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memcpy(seed,
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"\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
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20);
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#endif
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dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
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if (dbmask == NULL)
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{
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RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
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return 0;
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}
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if (MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH) < 0)
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return 0;
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for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
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db[i] ^= dbmask[i];
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if (MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH) < 0)
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return 0;
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for (i = 0; i < SHA_DIGEST_LENGTH; i++)
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seed[i] ^= seedmask[i];
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OPENSSL_free(dbmask);
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return 1;
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}
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int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
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const unsigned char *from, int flen, int num,
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const unsigned char *param, int plen)
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{
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int i, dblen, mlen = -1;
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const unsigned char *maskeddb;
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int lzero;
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unsigned char *db = NULL, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
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unsigned char *padded_from;
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int bad = 0;
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if (--num < 2 * SHA_DIGEST_LENGTH + 1)
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/* 'num' is the length of the modulus, i.e. does not depend on the
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* particular ciphertext. */
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goto decoding_err;
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lzero = num - flen;
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if (lzero < 0)
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{
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/* signalling this error immediately after detection might allow
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* for side-channel attacks (e.g. timing if 'plen' is huge
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* -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
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* Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
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* so we use a 'bad' flag */
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bad = 1;
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lzero = 0;
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flen = num; /* don't overflow the memcpy to padded_from */
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}
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dblen = num - SHA_DIGEST_LENGTH;
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db = OPENSSL_malloc(dblen + num);
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if (db == NULL)
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{
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
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return -1;
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}
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/* Always do this zero-padding copy (even when lzero == 0)
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* to avoid leaking timing info about the value of lzero. */
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padded_from = db + dblen;
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memset(padded_from, 0, lzero);
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memcpy(padded_from + lzero, from, flen);
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maskeddb = padded_from + SHA_DIGEST_LENGTH;
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if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen))
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return -1;
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for (i = 0; i < SHA_DIGEST_LENGTH; i++)
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seed[i] ^= padded_from[i];
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if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH))
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return -1;
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for (i = 0; i < dblen; i++)
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db[i] ^= maskeddb[i];
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if (!EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL))
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return -1;
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if (CRYPTO_memcmp(db, phash, SHA_DIGEST_LENGTH) != 0 || bad)
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goto decoding_err;
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else
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{
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for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
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if (db[i] != 0x00)
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break;
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if (i == dblen || db[i] != 0x01)
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goto decoding_err;
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else
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{
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/* everything looks OK */
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mlen = dblen - ++i;
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if (tlen < mlen)
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{
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
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mlen = -1;
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}
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else
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memcpy(to, db + i, mlen);
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}
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}
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OPENSSL_free(db);
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return mlen;
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decoding_err:
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/* to avoid chosen ciphertext attacks, the error message should not reveal
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* which kind of decoding error happened */
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
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if (db != NULL) OPENSSL_free(db);
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return -1;
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}
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int PKCS1_MGF1(unsigned char *mask, long len,
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const unsigned char *seed, long seedlen, const EVP_MD *dgst)
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{
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long i, outlen = 0;
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unsigned char cnt[4];
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EVP_MD_CTX c;
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unsigned char md[EVP_MAX_MD_SIZE];
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int mdlen;
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int rv = -1;
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EVP_MD_CTX_init(&c);
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mdlen = EVP_MD_size(dgst);
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if (mdlen < 0)
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goto err;
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for (i = 0; outlen < len; i++)
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{
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cnt[0] = (unsigned char)((i >> 24) & 255);
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cnt[1] = (unsigned char)((i >> 16) & 255);
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cnt[2] = (unsigned char)((i >> 8)) & 255;
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cnt[3] = (unsigned char)(i & 255);
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if (!EVP_DigestInit_ex(&c,dgst, NULL)
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|| !EVP_DigestUpdate(&c, seed, seedlen)
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|| !EVP_DigestUpdate(&c, cnt, 4))
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goto err;
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if (outlen + mdlen <= len)
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{
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if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
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goto err;
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outlen += mdlen;
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}
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else
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{
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if (!EVP_DigestFinal_ex(&c, md, NULL))
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goto err;
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memcpy(mask + outlen, md, len - outlen);
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outlen = len;
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}
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}
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rv = 0;
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err:
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EVP_MD_CTX_cleanup(&c);
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return rv;
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}
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static int MGF1(unsigned char *mask, long len, const unsigned char *seed,
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long seedlen)
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{
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return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
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}
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#endif
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