/*
- * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2019 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
*/
-#include "internal/constant_time_locl.h"
+#include "internal/constant_time.h"
#include <stdio.h>
-#include "internal/cryptlib.h"
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/rand.h>
+/* Just for the SSL_MAX_MASTER_KEY_LENGTH value */
+#include <openssl/ssl.h>
+#include "internal/cryptlib.h"
+#include "crypto/rsa.h"
int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,
const unsigned char *from, int flen)
if (flen > (tlen - RSA_PKCS1_PADDING_SIZE)) {
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_1,
RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
- return (0);
+ return 0;
}
p = (unsigned char *)to;
p += j;
*(p++) = '\0';
memcpy(p, from, (unsigned int)flen);
- return (1);
+ return 1;
}
int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,
* D - data.
*/
- if (num < 11)
+ if (num < RSA_PKCS1_PADDING_SIZE)
return -1;
/* Accept inputs with and without the leading 0-byte. */
if ((num != (flen + 1)) || (*(p++) != 0x01)) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_BLOCK_TYPE_IS_NOT_01);
- return (-1);
+ return -1;
}
/* scan over padding data */
} else {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_BAD_FIXED_HEADER_DECRYPT);
- return (-1);
+ return -1;
}
}
p++;
if (i == j) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_NULL_BEFORE_BLOCK_MISSING);
- return (-1);
+ return -1;
}
if (i < 8) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_BAD_PAD_BYTE_COUNT);
- return (-1);
+ return -1;
}
i++; /* Skip over the '\0' */
j -= i;
if (j > tlen) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, RSA_R_DATA_TOO_LARGE);
- return (-1);
+ return -1;
}
memcpy(to, p, (unsigned int)j);
- return (j);
+ return j;
}
int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen,
int i, j;
unsigned char *p;
- if (flen > (tlen - 11)) {
+ if (flen > (tlen - RSA_PKCS1_PADDING_SIZE)) {
RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_2,
RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
- return (0);
+ return 0;
}
p = (unsigned char *)to;
j = tlen - 3 - flen;
if (RAND_bytes(p, j) <= 0)
- return (0);
+ return 0;
for (i = 0; i < j; i++) {
if (*p == '\0')
do {
if (RAND_bytes(p, 1) <= 0)
- return (0);
+ return 0;
} while (*p == '\0');
p++;
}
*(p++) = '\0';
memcpy(p, from, (unsigned int)flen);
- return (1);
+ return 1;
}
int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
int i;
/* |em| is the encoded message, zero-padded to exactly |num| bytes */
unsigned char *em = NULL;
- unsigned int good, found_zero_byte;
+ unsigned int good, found_zero_byte, mask;
int zero_index = 0, msg_index, mlen = -1;
- if (tlen < 0 || flen < 0)
+ if (tlen <= 0 || flen <= 0)
return -1;
/*
* section 7.2.2.
*/
- if (flen > num)
- goto err;
-
- if (num < 11)
- goto err;
+ if (flen > num || num < RSA_PKCS1_PADDING_SIZE) {
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
+ RSA_R_PKCS_DECODING_ERROR);
+ return -1;
+ }
- em = OPENSSL_zalloc(num);
+ em = OPENSSL_malloc(num);
if (em == NULL) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE);
return -1;
}
/*
- * 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.
*/
- 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;
+ }
good = constant_time_is_zero(em[0]);
good &= constant_time_eq(em[1], 2);
+ /* scan over padding data */
found_zero_byte = 0;
for (i = 2; i < num; i++) {
unsigned int equals0 = constant_time_is_zero(em[i]);
- zero_index =
- constant_time_select_int(~found_zero_byte & equals0, i,
- zero_index);
+
+ zero_index = constant_time_select_int(~found_zero_byte & equals0,
+ i, zero_index);
found_zero_byte |= equals0;
}
* If we never found a 0-byte, then |zero_index| is 0 and the check
* also fails.
*/
- good &= constant_time_ge((unsigned int)(zero_index), 2 + 8);
+ good &= constant_time_ge(zero_index, 2 + 8);
/*
* Skip the zero byte. This is incorrect if we never found a zero-byte
mlen = num - msg_index;
/*
- * For good measure, do this check in constant time as well; it could
- * leak something if |tlen| was assuming valid padding.
+ * For good measure, do this check in constant time as well.
*/
- good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen));
+ good &= constant_time_ge(tlen, mlen);
/*
- * We can't continue in constant-time because we need to copy the result
- * and we cannot fake its length. This unavoidably leaks timing
- * information at the API boundary.
+ * Move the result in-place by |num|-RSA_PKCS1_PADDING_SIZE-|mlen| bytes to the left.
+ * Then if |good| move |mlen| bytes from |em|+RSA_PKCS1_PADDING_SIZE 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)).
*/
- if (!good) {
- mlen = -1;
- goto err;
+ tlen = constant_time_select_int(constant_time_lt(num - RSA_PKCS1_PADDING_SIZE, tlen),
+ num - RSA_PKCS1_PADDING_SIZE, tlen);
+ for (msg_index = 1; msg_index < num - RSA_PKCS1_PADDING_SIZE; msg_index <<= 1) {
+ mask = ~constant_time_eq(msg_index & (num - RSA_PKCS1_PADDING_SIZE - mlen), 0);
+ for (i = RSA_PKCS1_PADDING_SIZE; i < num - msg_index; i++)
+ em[i] = constant_time_select_8(mask, em[i + msg_index], em[i]);
+ }
+ for (i = 0; i < tlen; i++) {
+ mask = good & constant_time_lt(i, mlen);
+ to[i] = constant_time_select_8(mask, em[i + RSA_PKCS1_PADDING_SIZE], to[i]);
}
- memcpy(to, em + msg_index, mlen);
-
- err:
OPENSSL_clear_free(em, num);
- if (mlen == -1)
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
- RSA_R_PKCS_DECODING_ERROR);
- return mlen;
+#ifndef FIPS_MODE
+ /*
+ * 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_TYPE_2, RSA_R_PKCS_DECODING_ERROR);
+ err_clear_last_constant_time(1 & good);
+#endif
+
+ return constant_time_select_int(good, mlen, -1);
+}
+
+/*
+ * rsa_padding_check_PKCS1_type_2_TLS() checks and removes the PKCS1 type 2
+ * padding from a decrypted RSA message in a TLS signature. The result is stored
+ * in the buffer pointed to by |to| which should be |tlen| bytes long. |tlen|
+ * must be at least SSL_MAX_MASTER_KEY_LENGTH. The original decrypted message
+ * should be stored in |from| which must be |flen| bytes in length and padded
+ * such that |flen == RSA_size()|. The TLS protocol version that the client
+ * originally requested should be passed in |client_version|. Some buggy clients
+ * can exist which use the negotiated version instead of the originally
+ * requested protocol version. If it is necessary to work around this bug then
+ * the negotiated protocol version can be passed in |alt_version|, otherwise 0
+ * should be passed.
+ *
+ * If the passed message is publicly invalid or some other error that can be
+ * treated in non-constant time occurs then -1 is returned. On success the
+ * length of the decrypted data is returned. This will always be
+ * SSL_MAX_MASTER_KEY_LENGTH. If an error occurs that should be treated in
+ * constant time then this function will appear to return successfully, but the
+ * decrypted data will be randomly generated (as per
+ * https://tools.ietf.org/html/rfc5246#section-7.4.7.1).
+ */
+int rsa_padding_check_PKCS1_type_2_TLS(unsigned char *to, size_t tlen,
+ const unsigned char *from, size_t flen,
+ int client_version, int alt_version)
+{
+ unsigned int i, good, version_good;
+ unsigned char rand_premaster_secret[SSL_MAX_MASTER_KEY_LENGTH];
+
+ /*
+ * If these checks fail then either the message in publicly invalid, or
+ * we've been called incorrectly. We can fail immediately.
+ */
+ if (flen < RSA_PKCS1_PADDING_SIZE + SSL_MAX_MASTER_KEY_LENGTH
+ || tlen < SSL_MAX_MASTER_KEY_LENGTH) {
+ ERR_raise(ERR_LIB_RSA, RSA_R_PKCS_DECODING_ERROR);
+ return -1;
+ }
+
+ /*
+ * Generate a random premaster secret to use in the event that we fail
+ * to decrypt.
+ */
+ if (RAND_priv_bytes(rand_premaster_secret,
+ sizeof(rand_premaster_secret)) <= 0) {
+ ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
+ return -1;
+ }
+
+ good = constant_time_is_zero(from[0]);
+ good &= constant_time_eq(from[1], 2);
+
+ /* Check we have the expected padding data */
+ for (i = 2; i < flen - SSL_MAX_MASTER_KEY_LENGTH - 1; i++)
+ good &= ~constant_time_is_zero_8(from[i]);
+ good &= constant_time_is_zero_8(from[flen - SSL_MAX_MASTER_KEY_LENGTH - 1]);
+
+
+ /*
+ * If the version in the decrypted pre-master secret is correct then
+ * version_good will be 0xff, otherwise it'll be zero. The
+ * Klima-Pokorny-Rosa extension of Bleichenbacher's attack
+ * (http://eprint.iacr.org/2003/052/) exploits the version number
+ * check as a "bad version oracle". Thus version checks are done in
+ * constant time and are treated like any other decryption error.
+ */
+ version_good =
+ constant_time_eq(from[flen - SSL_MAX_MASTER_KEY_LENGTH],
+ (client_version >> 8) & 0xff);
+ version_good &=
+ constant_time_eq(from[flen - SSL_MAX_MASTER_KEY_LENGTH + 1],
+ client_version & 0xff);
+
+ /*
+ * The premaster secret must contain the same version number as the
+ * ClientHello to detect version rollback attacks (strangely, the
+ * protocol does not offer such protection for DH ciphersuites).
+ * However, buggy clients exist that send the negotiated protocol
+ * version instead if the server does not support the requested
+ * protocol version. If SSL_OP_TLS_ROLLBACK_BUG is set then we tolerate
+ * such clients. In that case alt_version will be non-zero and set to
+ * the negotiated version.
+ */
+ if (alt_version > 0) {
+ unsigned int workaround_good;
+
+ workaround_good =
+ constant_time_eq(from[flen - SSL_MAX_MASTER_KEY_LENGTH],
+ (alt_version >> 8) & 0xff);
+ workaround_good &=
+ constant_time_eq(from[flen - SSL_MAX_MASTER_KEY_LENGTH + 1],
+ alt_version & 0xff);
+ version_good |= workaround_good;
+ }
+
+ good &= version_good;
+
+
+ /*
+ * Now copy the result over to the to buffer if good, or random data if
+ * not good.
+ */
+ for (i = 0; i < SSL_MAX_MASTER_KEY_LENGTH; i++) {
+ to[i] =
+ constant_time_select_8(good,
+ from[flen - SSL_MAX_MASTER_KEY_LENGTH + i],
+ rand_premaster_secret[i]);
+ }
+
+ /*
+ * We must not leak whether a decryption failure occurs because of
+ * Bleichenbacher's attack on PKCS #1 v1.5 RSA padding (see RFC 2246,
+ * section 7.4.7.1). The code follows that advice of the TLS RFC and
+ * generates a random premaster secret for the case that the decrypt
+ * fails. See https://tools.ietf.org/html/rfc5246#section-7.4.7.1
+ * So, whether we actually succeeded or not, return success.
+ */
+
+ return SSL_MAX_MASTER_KEY_LENGTH;
}