358 lines
11 KiB
C
Executable file
358 lines
11 KiB
C
Executable file
/* $OpenBSD: rsa_oaep.c,v 1.35 2022/02/20 19:16:34 tb Exp $ */
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/*
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* Copyright 1999-2018 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. All advertising materials mentioning features or use of this
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* software must display the following acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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*
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* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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* endorse or promote products derived from this software without
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* prior written permission. For written permission, please contact
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* openssl-core@openssl.org.
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*
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* 5. Products derived from this software may not be called "OpenSSL"
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* nor may "OpenSSL" appear in their names without prior written
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* permission of the OpenSSL Project.
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*
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* 6. Redistributions of any form whatsoever must retain the following
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* acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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*
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* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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* ====================================================================
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*
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* This product includes cryptographic software written by Eric Young
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* (eay@cryptsoft.com). This product includes software written by Tim
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* Hudson (tjh@cryptsoft.com).
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*
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*/
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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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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <openssl/bn.h>
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#include <openssl/err.h>
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#include <openssl/evp.h>
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#include <openssl/rsa.h>
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#include <openssl/sha.h>
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#include "constant_time_locl.h"
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#include "evp_locl.h"
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#include "rsa_locl.h"
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int
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RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
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const unsigned char *from, int flen, const unsigned char *param, int plen)
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{
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return RSA_padding_add_PKCS1_OAEP_mgf1(to, tlen, from, flen, param,
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plen, NULL, NULL);
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}
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int
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RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
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const unsigned char *from, int flen, const unsigned char *param, int plen,
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const EVP_MD *md, const EVP_MD *mgf1md)
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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 = NULL;
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unsigned char seedmask[EVP_MAX_MD_SIZE];
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int mdlen, dbmask_len = 0;
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int rv = 0;
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if (md == NULL)
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md = EVP_sha1();
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if (mgf1md == NULL)
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mgf1md = md;
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if ((mdlen = EVP_MD_size(md)) <= 0)
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goto err;
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if (flen > emlen - 2 * mdlen - 1) {
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RSAerror(RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
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goto err;
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}
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if (emlen < 2 * mdlen + 1) {
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RSAerror(RSA_R_KEY_SIZE_TOO_SMALL);
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goto err;
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}
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to[0] = 0;
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seed = to + 1;
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db = to + mdlen + 1;
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if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL))
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goto err;
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memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1);
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db[emlen - flen - mdlen - 1] = 0x01;
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memcpy(db + emlen - flen - mdlen, from, flen);
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arc4random_buf(seed, mdlen);
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dbmask_len = emlen - mdlen;
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if ((dbmask = malloc(dbmask_len)) == NULL) {
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RSAerror(ERR_R_MALLOC_FAILURE);
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goto err;
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}
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if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0)
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goto err;
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for (i = 0; i < dbmask_len; i++)
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db[i] ^= dbmask[i];
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if (PKCS1_MGF1(seedmask, mdlen, db, dbmask_len, mgf1md) < 0)
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goto err;
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for (i = 0; i < mdlen; i++)
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seed[i] ^= seedmask[i];
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rv = 1;
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err:
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explicit_bzero(seedmask, sizeof(seedmask));
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freezero(dbmask, dbmask_len);
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return rv;
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}
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int
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RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
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const unsigned char *from, int flen, int num, const unsigned char *param,
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int plen)
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{
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return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from, flen, num,
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param, plen, NULL, NULL);
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}
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int
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RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
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const unsigned char *from, int flen, int num, const unsigned char *param,
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int plen, const EVP_MD *md, const EVP_MD *mgf1md)
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{
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int i, dblen = 0, mlen = -1, one_index = 0, msg_index;
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unsigned int good = 0, found_one_byte, mask;
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const unsigned char *maskedseed, *maskeddb;
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unsigned char seed[EVP_MAX_MD_SIZE], phash[EVP_MAX_MD_SIZE];
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unsigned char *db = NULL, *em = NULL;
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int mdlen;
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if (md == NULL)
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md = EVP_sha1();
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if (mgf1md == NULL)
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mgf1md = md;
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if ((mdlen = EVP_MD_size(md)) <= 0)
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return -1;
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if (tlen <= 0 || flen <= 0)
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return -1;
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/*
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* |num| is the length of the modulus; |flen| is the length of the
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* encoded message. Therefore, for any |from| that was obtained by
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* decrypting a ciphertext, we must have |flen| <= |num|. Similarly,
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* |num| >= 2 * |mdlen| + 2 must hold for the modulus irrespective
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* of the ciphertext, see PKCS #1 v2.2, section 7.1.2.
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* This does not leak any side-channel information.
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*/
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if (num < flen || num < 2 * mdlen + 2) {
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RSAerror(RSA_R_OAEP_DECODING_ERROR);
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return -1;
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}
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dblen = num - mdlen - 1;
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if ((db = malloc(dblen)) == NULL) {
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RSAerror(ERR_R_MALLOC_FAILURE);
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goto cleanup;
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}
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if ((em = malloc(num)) == NULL) {
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RSAerror(ERR_R_MALLOC_FAILURE);
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goto cleanup;
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}
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/*
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* Caller is encouraged to pass zero-padded message created with
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* BN_bn2binpad. Trouble is that since we can't read out of |from|'s
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* bounds, it's impossible to have an invariant memory access pattern
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* in case |from| was not zero-padded in advance.
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*/
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for (from += flen, em += num, i = 0; i < num; i++) {
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mask = ~constant_time_is_zero(flen);
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flen -= 1 & mask;
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from -= 1 & mask;
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*--em = *from & mask;
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}
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/*
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* The first byte must be zero, however we must not leak if this is
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* true. See James H. Manger, "A Chosen Ciphertext Attack on RSA
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* Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001).
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*/
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good = constant_time_is_zero(em[0]);
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maskedseed = em + 1;
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maskeddb = em + 1 + mdlen;
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if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md))
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goto cleanup;
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for (i = 0; i < mdlen; i++)
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seed[i] ^= maskedseed[i];
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if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md))
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goto cleanup;
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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, md, NULL))
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goto cleanup;
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good &= constant_time_is_zero(timingsafe_memcmp(db, phash, mdlen));
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found_one_byte = 0;
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for (i = mdlen; i < dblen; i++) {
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/*
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* Padding consists of a number of 0-bytes, followed by a 1.
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*/
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unsigned int equals1 = constant_time_eq(db[i], 1);
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unsigned int equals0 = constant_time_is_zero(db[i]);
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one_index = constant_time_select_int(~found_one_byte & equals1,
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i, one_index);
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found_one_byte |= equals1;
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good &= (found_one_byte | equals0);
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}
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good &= found_one_byte;
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/*
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* At this point |good| is zero unless the plaintext was valid,
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* so plaintext-awareness ensures timing side-channels are no longer a
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* concern.
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*/
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msg_index = one_index + 1;
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mlen = dblen - msg_index;
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/*
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* For good measure, do this check in constant time as well.
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*/
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good &= constant_time_ge(tlen, mlen);
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/*
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* Even though we can't fake result's length, we can pretend copying
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* |tlen| bytes where |mlen| bytes would be real. The last |tlen| of
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* |dblen| bytes are viewed as a circular buffer starting at |tlen|-|mlen'|,
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* where |mlen'| is the "saturated" |mlen| value. Deducing information
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* about failure or |mlen| would require an attacker to observe
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* memory access patterns with byte granularity *as it occurs*. It
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* should be noted that failure is indistinguishable from normal
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* operation if |tlen| is fixed by protocol.
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*/
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tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen),
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dblen - mdlen - 1, tlen);
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msg_index = constant_time_select_int(good, msg_index, dblen - tlen);
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mlen = dblen - msg_index;
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for (mask = good, i = 0; i < tlen; i++) {
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unsigned int equals = constant_time_eq(msg_index, dblen);
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msg_index -= tlen & equals; /* rewind at EOF */
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mask &= ~equals; /* mask = 0 at EOF */
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to[i] = constant_time_select_8(mask, db[msg_index++], to[i]);
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}
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/*
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* To avoid chosen ciphertext attacks, the error message should not
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* reveal which kind of decoding error happened.
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*/
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RSAerror(RSA_R_OAEP_DECODING_ERROR);
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err_clear_last_constant_time(1 & good);
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cleanup:
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explicit_bzero(seed, sizeof(seed));
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freezero(db, dblen);
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freezero(em, num);
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return constant_time_select_int(good, mlen, -1);
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}
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int
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PKCS1_MGF1(unsigned char *mask, long len, const unsigned char *seed,
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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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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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if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
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goto err;
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outlen += mdlen;
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} else {
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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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