-/* 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. */
+/*
+ * Copyright 1999-2020 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) */
-/* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
- * <URL: http://www.shoup.net/papers/oaep.ps.Z>
- * for problems with the security proof for the
- * original OAEP scheme, which EME-OAEP is based on.
- *
- * A new proof can be found in E. Fujisaki, T. Okamoto,
- * D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
- * Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
- * The new proof has stronger requirements for the
- * underlying permutation: "partial-one-wayness" instead
- * of one-wayness. For the RSA function, this is
- * an equivalent notion.
+/*
+ * See Victor Shoup, "OAEP reconsidered," Nov. 2000, <URL:
+ * http://www.shoup.net/papers/oaep.ps.Z> for problems with the security
+ * proof for the original OAEP scheme, which EME-OAEP is based on. A new
+ * proof can be found in E. Fujisaki, T. Okamoto, D. Pointcheval, J. Stern,
+ * "RSA-OEAP is Still Alive!", Dec. 2000, <URL:
+ * http://eprint.iacr.org/2000/061/>. The new proof has stronger requirements
+ * for the underlying permutation: "partial-one-wayness" instead of
+ * one-wayness. For the RSA function, this is an equivalent notion.
*/
-#define OPENSSL_FIPSAPI
+/*
+ * RSA low level APIs are deprecated for public use, but still ok for
+ * internal use.
+ */
+#include "internal/deprecated.h"
+#include "internal/constant_time.h"
-#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
#include <stdio.h>
-#include "cryptlib.h"
+#include "internal/cryptlib.h"
#include <openssl/bn.h>
-#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <openssl/sha.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);
- }
-
-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)
- {
- int i, emlen = tlen - 1;
- unsigned char *db, *seed;
- unsigned char *dbmask, seedmask[EVP_MAX_MD_SIZE];
- int mdlen;
-
- if (md == NULL)
- md = EVP_sha1();
- if (mgf1md == NULL)
- mgf1md = md;
-
- mdlen = EVP_MD_size(md);
-
- if (flen > emlen - 2 * mdlen - 1)
- {
- RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1,
- 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);
- return 0;
- }
-
- to[0] = 0;
- seed = to + 1;
- db = to + mdlen + 1;
-
- if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL))
- return 0;
- 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);
+ const unsigned char *from, int flen,
+ const unsigned char *param, int plen)
+{
+ return ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(NULL, to, tlen, from, flen,
+ param, plen, NULL, NULL);
+}
+
+/*
+ * 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 ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(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 = NULL;
+ unsigned char seedmask[EVP_MAX_MD_SIZE];
+ int mdlen, dbmask_len = 0;
+
+ if (md == NULL) {
+#ifndef FIPS_MODULE
+ 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(0, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
+ return 0;
+ }
+
+ if (emlen < 2 * mdlen + 1) {
+ 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))
+ 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);
+ /* step 3d: generate random byte string */
+ if (RAND_bytes_ex(libctx, seed, mdlen) <= 0)
+ goto err;
+
+ dbmask_len = emlen - mdlen;
+ dbmask = OPENSSL_malloc(dbmask_len);
+ if (dbmask == NULL) {
+ RSAerr(0, ERR_R_MALLOC_FAILURE);
+ goto err;
+ }
+
+ /* step 3e: dbMask = MGF(mgfSeed, nLen - HLen - 1) */
+ if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0)
+ goto err;
+ /* step 3f: maskedDB = DB XOR dbMask */
+ for (i = 0; i < dbmask_len; i++)
+ db[i] ^= dbmask[i];
+
+ /* 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];
+ rv = 1;
+
+ err:
+ OPENSSL_cleanse(seedmask, sizeof(seedmask));
+ OPENSSL_clear_free(dbmask, dbmask_len);
+ return rv;
+}
- dbmask = OPENSSL_malloc(emlen - mdlen);
- if (dbmask == NULL)
- {
- RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE);
- return 0;
- }
-
- if (PKCS1_MGF1(dbmask, emlen - mdlen, seed, mdlen, mgf1md) < 0)
- return 0;
- for (i = 0; i < emlen - mdlen; i++)
- db[i] ^= dbmask[i];
-
- if (PKCS1_MGF1(seedmask, mdlen, db, emlen - mdlen, mgf1md) < 0)
- return 0;
- for (i = 0; i < mdlen; i++)
- seed[i] ^= seedmask[i];
-
- OPENSSL_free(dbmask);
- return 1;
- }
+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 ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(NULL, to, tlen, from, flen,
+ param, plen, md, mgf1md);
+}
int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
- const unsigned char *from, int flen, int num,
- const unsigned char *param, int plen)
- {
- return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from , flen, num,
- param, plen,
- NULL, NULL);
- }
+ const unsigned char *from, int flen, int num,
+ const unsigned char *param, int plen)
+{
+ return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from, flen, num,
+ param, plen, NULL, NULL);
+}
int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
- const unsigned char *from, int flen, int num,
- const unsigned char *param, int plen,
- const EVP_MD *md, const EVP_MD *mgf1md)
- {
- int i, dblen, mlen = -1;
- const unsigned char *maskeddb;
- int lzero;
- unsigned char *db = NULL, seed[EVP_MAX_MD_SIZE], phash[EVP_MAX_MD_SIZE];
- unsigned char *padded_from;
- int bad = 0;
- int mdlen;
-
- if (md == NULL)
- md = EVP_sha1();
- if (mgf1md == NULL)
- mgf1md = md;
-
- mdlen = EVP_MD_size(md);
-
- if (--num < 2 * mdlen + 1)
- /* 'num' is the length of the modulus, i.e. does not depend on the
- * particular ciphertext. */
- goto decoding_err;
-
- lzero = num - flen;
- if (lzero < 0)
- {
- /* signalling this error immediately after detection might allow
- * for side-channel attacks (e.g. timing if 'plen' is huge
- * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
- * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
- * so we use a 'bad' flag */
- bad = 1;
- lzero = 0;
- flen = num; /* don't overflow the memcpy to padded_from */
- }
-
- dblen = num - mdlen;
- db = OPENSSL_malloc(dblen + num);
- if (db == NULL)
- {
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE);
- return -1;
- }
-
- /* Always do this zero-padding copy (even when lzero == 0)
- * to avoid leaking timing info about the value of lzero. */
- padded_from = db + dblen;
- memset(padded_from, 0, lzero);
- memcpy(padded_from + lzero, from, flen);
-
- maskeddb = padded_from + mdlen;
-
- if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md))
- return -1;
- for (i = 0; i < mdlen; i++)
- seed[i] ^= padded_from[i];
-
- if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md))
- return -1;
- for (i = 0; i < dblen; i++)
- db[i] ^= maskeddb[i];
-
- if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL))
- return -1;
-
- if (CRYPTO_memcmp(db, phash, mdlen) != 0 || bad)
- goto decoding_err;
- else
- {
- for (i = mdlen; i < dblen; i++)
- if (db[i] != 0x00)
- break;
- if (i == dblen || db[i] != 0x01)
- goto decoding_err;
- else
- {
- /* everything looks OK */
-
- mlen = dblen - ++i;
- if (tlen < mlen)
- {
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_DATA_TOO_LARGE);
- mlen = -1;
- }
- else
- memcpy(to, db + i, mlen);
- }
- }
- OPENSSL_free(db);
- return mlen;
-
-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);
- if (db != NULL) OPENSSL_free(db);
- return -1;
- }
-
-int PKCS1_MGF1(unsigned char *mask, long len,
- const unsigned char *seed, long seedlen, const EVP_MD *dgst)
- {
- long i, outlen = 0;
- unsigned char cnt[4];
- EVP_MD_CTX c;
- unsigned char md[EVP_MAX_MD_SIZE];
- int mdlen;
- int rv = -1;
-
- EVP_MD_CTX_init(&c);
- mdlen = M_EVP_MD_size(dgst);
- if (mdlen < 0)
- goto err;
- for (i = 0; outlen < len; i++)
- {
- 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);
- if (!EVP_DigestInit_ex(&c,dgst, NULL)
- || !EVP_DigestUpdate(&c, seed, seedlen)
- || !EVP_DigestUpdate(&c, cnt, 4))
- goto err;
- if (outlen + mdlen <= len)
- {
- if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
- goto err;
- outlen += mdlen;
- }
- else
- {
- if (!EVP_DigestFinal_ex(&c, md, NULL))
- goto err;
- memcpy(mask + outlen, md, len - outlen);
- outlen = len;
- }
- }
- rv = 0;
- err:
- EVP_MD_CTX_cleanup(&c);
- return rv;
- }
-
+ const unsigned char *from, int flen,
+ int num, const unsigned char *param,
+ int plen, const EVP_MD *md,
+ const EVP_MD *mgf1md)
+{
+ 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 =
+ * Y || maskedSeed || maskedDB
+ */
+ unsigned char *db = NULL, *em = NULL, seed[EVP_MAX_MD_SIZE],
+ phash[EVP_MAX_MD_SIZE];
+ int mdlen;
+
+ if (md == NULL) {
+#ifndef FIPS_MODULE
+ md = EVP_sha1();
+#else
+ RSAerr(0, ERR_R_PASSED_NULL_PARAMETER);
+ return -1;
#endif
+ }
+
+ if (mgf1md == NULL)
+ mgf1md = md;
+
+ mdlen = EVP_MD_size(md);
+
+ if (tlen <= 0 || flen <= 0)
+ return -1;
+ /*
+ * |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
+ * 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) {
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1,
+ RSA_R_OAEP_DECODING_ERROR);
+ return -1;
+ }
+
+ dblen = num - mdlen - 1;
+ db = OPENSSL_malloc(dblen);
+ 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;
+ }
+
+ /*
+ * 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.
+ */
+ 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
+ * true. See James H. Manger, "A Chosen Ciphertext Attack on RSA
+ * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001).
+ */
+ good = constant_time_is_zero(em[0]);
+
+ maskedseed = em + 1;
+ maskeddb = em + 1 + mdlen;
+
+ if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md))
+ goto cleanup;
+ for (i = 0; i < mdlen; i++)
+ seed[i] ^= maskedseed[i];
+
+ if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md))
+ goto cleanup;
+ for (i = 0; i < dblen; i++)
+ db[i] ^= maskeddb[i];
+
+ if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL))
+ goto cleanup;
+
+ good &= constant_time_is_zero(CRYPTO_memcmp(db, phash, mdlen));
+
+ found_one_byte = 0;
+ for (i = mdlen; i < dblen; i++) {
+ /*
+ * Padding consists of a number of 0-bytes, followed by a 1.
+ */
+ unsigned int equals1 = constant_time_eq(db[i], 1);
+ unsigned int equals0 = constant_time_is_zero(db[i]);
+ one_index = constant_time_select_int(~found_one_byte & equals1,
+ i, one_index);
+ found_one_byte |= equals1;
+ good &= (found_one_byte | equals0);
+ }
+
+ good &= found_one_byte;
+
+ /*
+ * At this point |good| is zero unless the plaintext was valid,
+ * so plaintext-awareness ensures timing side-channels are no longer a
+ * concern.
+ */
+ msg_index = one_index + 1;
+ mlen = dblen - msg_index;
+
+ /*
+ * 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]);
+ }
+
+#ifndef FIPS_MODULE
+ /*
+ * 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 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)
+{
+ long i, outlen = 0;
+ unsigned char cnt[4];
+ EVP_MD_CTX *c = EVP_MD_CTX_new();
+ unsigned char md[EVP_MAX_MD_SIZE];
+ int mdlen;
+ int rv = -1;
+
+ if (c == NULL)
+ goto err;
+ 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))
+ goto err;
+ if (outlen + mdlen <= len) {
+ if (!EVP_DigestFinal_ex(c, mask + outlen, NULL))
+ goto err;
+ outlen += mdlen;
+ } else {
+ if (!EVP_DigestFinal_ex(c, md, NULL))
+ goto err;
+ memcpy(mask + outlen, md, len - outlen);
+ outlen = len;
+ }
+ }
+ rv = 0;
+ err:
+ OPENSSL_cleanse(md, sizeof(md));
+ EVP_MD_CTX_free(c);
+ return rv;
+}
projects / openssl.git / blobdiff