/*
- * Written by Ulf Moeller. This software is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied.
+ * Copyright 1999-2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License"). You may not use
+ * this file except in compliance with the License. You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
*/
/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
const unsigned char *param, int plen,
const EVP_MD *md, const EVP_MD *mgf1md)
{
+ int rv = 0;
int i, emlen = tlen - 1;
unsigned char *db, *seed;
- unsigned char *dbmask, seedmask[EVP_MAX_MD_SIZE];
- int mdlen;
+ unsigned char *dbmask = NULL;
+ unsigned char seedmask[EVP_MAX_MD_SIZE];
+ int mdlen, dbmask_len = 0;
if (md == NULL)
md = EVP_sha1();
db = to + mdlen + 1;
if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL))
- return 0;
+ goto err;
memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1);
db[emlen - flen - mdlen - 1] = 0x01;
memcpy(db + emlen - flen - mdlen, from, (unsigned int)flen);
if (RAND_bytes(seed, mdlen) <= 0)
- return 0;
-#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
+ goto err;
- dbmask = OPENSSL_malloc(emlen - mdlen);
+ dbmask_len = emlen - mdlen;
+ dbmask = OPENSSL_malloc(dbmask_len);
if (dbmask == NULL) {
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE);
- return 0;
+ goto err;
}
- if (PKCS1_MGF1(dbmask, emlen - mdlen, seed, mdlen, mgf1md) < 0)
- return 0;
- for (i = 0; i < emlen - mdlen; i++)
+ if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0)
+ goto err;
+ for (i = 0; i < dbmask_len; i++)
db[i] ^= dbmask[i];
- if (PKCS1_MGF1(seedmask, mdlen, db, emlen - mdlen, mgf1md) < 0)
- return 0;
+ if (PKCS1_MGF1(seedmask, mdlen, db, dbmask_len, mgf1md) < 0)
+ goto err;
for (i = 0; i < mdlen; i++)
seed[i] ^= seedmask[i];
+ rv = 1;
- OPENSSL_free(dbmask);
- return 1;
+ err:
+ OPENSSL_cleanse(seedmask, sizeof(seedmask));
+ OPENSSL_clear_free(dbmask, dbmask_len);
+ return rv;
}
int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
int plen, const EVP_MD *md,
const EVP_MD *mgf1md)
{
- int i, dblen, mlen = -1, one_index = 0, msg_index;
- unsigned int good, found_one_byte;
+ int i, dblen = 0, mlen = -1, one_index = 0, msg_index;
+ unsigned int good = 0, found_one_byte, mask;
const unsigned char *maskedseed, *maskeddb;
/*
* |em| is the encoded message, zero-padded to exactly |num| bytes: em =
* |num| is the length of the modulus; |flen| is the length of the
* encoded message. Therefore, for any |from| that was obtained by
* decrypting a ciphertext, we must have |flen| <= |num|. Similarly,
- * num < 2 * mdlen + 2 must hold for the modulus irrespective of
+ * |num| >= 2 * |mdlen| + 2 must hold for the modulus irrespective of
* the ciphertext, see PKCS #1 v2.2, section 7.1.2.
* This does not leak any side-channel information.
*/
- if (num < flen || num < 2 * mdlen + 2)
- goto decoding_err;
+ if (num < flen || num < 2 * mdlen + 2) {
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1,
+ RSA_R_OAEP_DECODING_ERROR);
+ return -1;
+ }
dblen = num - mdlen - 1;
db = OPENSSL_malloc(dblen);
- em = OPENSSL_malloc(num);
- if (db == NULL || em == NULL) {
+ if (db == NULL) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE);
goto cleanup;
}
+ em = OPENSSL_malloc(num);
+ if (em == NULL) {
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1,
+ ERR_R_MALLOC_FAILURE);
+ goto cleanup;
+ }
+
/*
- * Always do this zero-padding copy (even when num == flen) to avoid
- * leaking that information. The copy still leaks some side-channel
- * information, but it's impossible to have a fixed memory access
- * pattern since we can't read out of the bounds of |from|.
- *
- * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL.
+ * Caller is encouraged to pass zero-padded message created with
+ * BN_bn2binpad. Trouble is that since we can't read out of |from|'s
+ * bounds, it's impossible to have an invariant memory access pattern
+ * in case |from| was not zero-padded in advance.
*/
- memset(em, 0, num);
- memcpy(em + num - flen, from, flen);
+ for (from += flen, em += num, i = 0; i < num; i++) {
+ mask = ~constant_time_is_zero(flen);
+ flen -= 1 & mask;
+ from -= 1 & mask;
+ *--em = *from & mask;
+ }
/*
* The first byte must be zero, however we must not leak if this is
* so plaintext-awareness ensures timing side-channels are no longer a
* concern.
*/
- if (!good)
- goto decoding_err;
-
msg_index = one_index + 1;
mlen = dblen - msg_index;
- if (tlen < mlen) {
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_DATA_TOO_LARGE);
- mlen = -1;
- } else {
- memcpy(to, db + msg_index, mlen);
- goto cleanup;
+ /*
+ * For good measure, do this check in constant time as well.
+ */
+ good &= constant_time_ge(tlen, mlen);
+
+ /*
+ * Even though we can't fake result's length, we can pretend copying
+ * |tlen| bytes where |mlen| bytes would be real. Last |tlen| of |dblen|
+ * bytes are viewed as circular buffer with start at |tlen|-|mlen'|,
+ * where |mlen'| is "saturated" |mlen| value. Deducing information
+ * about failure or |mlen| would take attacker's ability to observe
+ * memory access pattern with byte granularity *as it occurs*. It
+ * should be noted that failure is indistinguishable from normal
+ * operation if |tlen| is fixed by protocol.
+ */
+ tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen),
+ dblen - mdlen - 1, tlen);
+ msg_index = constant_time_select_int(good, msg_index, dblen - tlen);
+ mlen = dblen - msg_index;
+ for (mask = good, i = 0; i < tlen; i++) {
+ unsigned int equals = constant_time_eq(msg_index, dblen);
+
+ msg_index -= tlen & equals; /* rewind at EOF */
+ mask &= ~equals; /* mask = 0 at EOF */
+ to[i] = constant_time_select_8(mask, db[msg_index++], to[i]);
}
- decoding_err:
/*
* To avoid chosen ciphertext attacks, the error message should not
* reveal which kind of decoding error happened.
*/
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1,
RSA_R_OAEP_DECODING_ERROR);
+ err_clear_last_constant_time(1 & good);
cleanup:
- OPENSSL_free(db);
- OPENSSL_free(em);
- return mlen;
+ OPENSSL_cleanse(seed, sizeof(seed));
+ OPENSSL_clear_free(db, dblen);
+ OPENSSL_clear_free(em, num);
+
+ return constant_time_select_int(good, mlen, -1);
}
int PKCS1_MGF1(unsigned char *mask, long len,
}
rv = 0;
err:
+ OPENSSL_cleanse(md, sizeof(md));
EVP_MD_CTX_free(c);
return rv;
}
projects / openssl.git / blobdiff