/*
- * Copyright 1999-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1999-2020 The OpenSSL Project Authors. All Rights Reserved.
*
- * Licensed under the OpenSSL license (the "License"). You may not use
+ * 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
* one-wayness. For the RSA function, this is an equivalent notion.
*/
-#include "internal/constant_time_locl.h"
+/*
+ * RSA low level APIs are deprecated for public use, but still ok for
+ * internal use.
+ */
+#include "internal/deprecated.h"
+
+#include "internal/constant_time.h"
#include <stdio.h>
#include "internal/cryptlib.h"
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <openssl/sha.h>
-#include "rsa_locl.h"
+#include "rsa_local.h"
int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
const unsigned char *from, int flen,
const unsigned char *param, int plen)
{
- return RSA_padding_add_PKCS1_OAEP_mgf1(to, tlen, from, flen,
- param, plen, NULL, NULL);
+ return rsa_padding_add_PKCS1_OAEP_mgf1_with_libctx(NULL, to, tlen, from,
+ flen, param, plen, NULL,
+ NULL);
}
-int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
- const unsigned char *from, int flen,
- const unsigned char *param, int plen,
- const EVP_MD *md, const EVP_MD *mgf1md)
+/*
+ * Perform ihe padding as per NIST 800-56B 7.2.2.3
+ * from (K) is the key material.
+ * param (A) is the additional input.
+ * Step numbers are included here but not in the constant time inverse below
+ * to avoid complicating an already difficult enough function.
+ */
+int rsa_padding_add_PKCS1_OAEP_mgf1_with_libctx(OPENSSL_CTX *libctx,
+ unsigned char *to, int tlen,
+ const unsigned char *from,
+ int flen,
+ 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;
+#ifndef FIPS_MODE
if (md == NULL)
md = EVP_sha1();
+#else
+ RSAerr(0, ERR_R_PASSED_NULL_PARAMETER);
+ return 0;
+#endif
if (mgf1md == NULL)
mgf1md = md;
mdlen = EVP_MD_size(md);
+ /* step 2b: check KLen > nLen - 2 HLen - 2 */
if (flen > emlen - 2 * mdlen - 1) {
- RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1,
- RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
+ RSAerr(0, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
return 0;
}
if (emlen < 2 * mdlen + 1) {
- RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1,
- RSA_R_KEY_SIZE_TOO_SMALL);
+ RSAerr(0, RSA_R_KEY_SIZE_TOO_SMALL);
return 0;
}
+ /* step 3i: EM = 00000000 || maskedMGF || maskedDB */
to[0] = 0;
seed = to + 1;
db = to + mdlen + 1;
+ /* step 3a: hash the additional input */
if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL))
- return 0;
+ goto err;
+ /* step 3b: zero bytes array of length nLen - KLen - 2 HLen -2 */
memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1);
+ /* step 3c: DB = HA || PS || 00000001 || K */
db[emlen - flen - mdlen - 1] = 0x01;
memcpy(db + emlen - flen - mdlen, from, (unsigned int)flen);
- if (RAND_bytes(seed, mdlen) <= 0)
- return 0;
+ /* step 3d: generate random byte string */
+ if (RAND_bytes_ex(libctx, seed, mdlen) <= 0)
+ 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;
+ RSAerr(0, ERR_R_MALLOC_FAILURE);
+ goto err;
}
- if (PKCS1_MGF1(dbmask, emlen - mdlen, seed, mdlen, mgf1md) < 0)
+ /* step 3e: dbMask = MGF(mgfSeed, nLen - HLen - 1) */
+ if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0)
goto err;
- for (i = 0; i < emlen - mdlen; i++)
+ /* step 3f: maskedDB = DB XOR dbMask */
+ for (i = 0; i < dbmask_len; i++)
db[i] ^= dbmask[i];
- if (PKCS1_MGF1(seedmask, mdlen, db, emlen - mdlen, mgf1md) < 0)
+ /* step 3g: mgfSeed = MGF(maskedDB, HLen) */
+ if (PKCS1_MGF1(seedmask, mdlen, db, dbmask_len, mgf1md) < 0)
goto err;
+ /* stepo 3h: maskedMGFSeed = mgfSeed XOR mgfSeedMask */
for (i = 0; i < mdlen; i++)
seed[i] ^= seedmask[i];
-
- OPENSSL_free(dbmask);
- return 1;
+ rv = 1;
err:
- OPENSSL_free(dbmask);
- return 0;
+ OPENSSL_cleanse(seedmask, sizeof(seedmask));
+ OPENSSL_clear_free(dbmask, dbmask_len);
+ return rv;
+}
+
+int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
+ const unsigned char *from, int flen,
+ const unsigned char *param, int plen,
+ const EVP_MD *md, const EVP_MD *mgf1md)
+{
+ return rsa_padding_add_PKCS1_OAEP_mgf1_with_libctx(NULL, to, tlen, from,
+ flen, param, plen, md,
+ mgf1md);
}
int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
const EVP_MD *mgf1md)
{
int i, dblen = 0, mlen = -1, one_index = 0, msg_index;
- unsigned int good, found_one_byte;
+ 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 =
phash[EVP_MAX_MD_SIZE];
int mdlen;
- if (md == NULL)
+ if (md == NULL) {
+#ifndef FIPS_MODE
md = EVP_sha1();
+#else
+ RSAerr(0, ERR_R_PASSED_NULL_PARAMETER);
+ return -1;
+#endif
+ }
+
if (mgf1md == NULL)
mgf1md = md;
* |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);
+
+ /*
+ * Move the result in-place by |dblen|-|mdlen|-1-|mlen| bytes to the left.
+ * Then if |good| move |mlen| bytes from |db|+|mdlen|+1 to |to|.
+ * Otherwise leave |to| unchanged.
+ * Copy the memory back in a way that does not reveal the size of
+ * the data being copied via a timing side channel. This requires copying
+ * parts of the buffer multiple times based on the bits set in the real
+ * length. Clear bits do a non-copy with identical access pattern.
+ * The loop below has overall complexity of O(N*log(N)).
+ */
+ tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen),
+ dblen - mdlen - 1, tlen);
+ for (msg_index = 1; msg_index < dblen - mdlen - 1; msg_index <<= 1) {
+ mask = ~constant_time_eq(msg_index & (dblen - mdlen - 1 - mlen), 0);
+ for (i = mdlen + 1; i < dblen - msg_index; i++)
+ db[i] = constant_time_select_8(mask, db[i + msg_index], db[i]);
+ }
+ for (i = 0; i < tlen; i++) {
+ mask = good & constant_time_lt(i, mlen);
+ to[i] = constant_time_select_8(mask, db[i + mdlen + 1], to[i]);
}
- decoding_err:
+#ifndef FIPS_MODE
/*
* To avoid chosen ciphertext attacks, the error message should not
* reveal which kind of decoding error happened.
+ *
+ * This trick doesn't work in the FIPS provider because libcrypto manages
+ * the error stack. Instead we opt not to put an error on the stack at all
+ * in case of padding failure in the FIPS provider.
*/
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1,
RSA_R_OAEP_DECODING_ERROR);
+ err_clear_last_constant_time(1 & good);
+#endif
cleanup:
+ OPENSSL_cleanse(seed, sizeof(seed));
OPENSSL_clear_free(db, dblen);
OPENSSL_clear_free(em, num);
- return mlen;
+
+ return constant_time_select_int(good, mlen, -1);
}
+/*
+ * Mask Generation Function corresponding to section 7.2.2.2 of NIST SP 800-56B.
+ * The variables are named differently to NIST:
+ * mask (T) and len (maskLen)are the returned mask.
+ * seed (mgfSeed).
+ * The range checking steps inm the process are performed outside.
+ */
int PKCS1_MGF1(unsigned char *mask, long len,
const unsigned char *seed, long seedlen, const EVP_MD *dgst)
{
mdlen = EVP_MD_size(dgst);
if (mdlen < 0)
goto err;
+ /* step 4 */
for (i = 0; outlen < len; i++) {
+ /* step 4a: D = I2BS(counter, 4) */
cnt[0] = (unsigned char)((i >> 24) & 255);
cnt[1] = (unsigned char)((i >> 16) & 255);
cnt[2] = (unsigned char)((i >> 8)) & 255;
cnt[3] = (unsigned char)(i & 255);
+ /* step 4b: T =T || hash(mgfSeed || D) */
if (!EVP_DigestInit_ex(c, dgst, NULL)
|| !EVP_DigestUpdate(c, seed, seedlen)
|| !EVP_DigestUpdate(c, cnt, 4))
}
rv = 0;
err:
+ OPENSSL_cleanse(md, sizeof(md));
EVP_MD_CTX_free(c);
return rv;
}
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