/* crypto/rsa/rsa_ssl.c */ /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. * * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to. The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code. The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). * * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * "This product includes cryptographic software written by * Eric Young (eay@cryptsoft.com)" * The word 'cryptographic' can be left out if the rouines from the library * being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from * the apps directory (application code) you must include an acknowledgement: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" * * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */ #include #include "cryptlib.h" #include #include #include #include "constant_time_locl.h" int RSA_padding_add_SSLv23(unsigned char *to, int tlen, const unsigned char *from, int flen) { int i, j; unsigned char *p; if (flen > (tlen - 11)) { RSAerr(RSA_F_RSA_PADDING_ADD_SSLV23, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); return (0); } p = (unsigned char *)to; *(p++) = 0; *(p++) = 2; /* Public Key BT (Block Type) */ /* pad out with non-zero random data */ j = tlen - 3 - 8 - flen; if (RAND_bytes(p, j) <= 0) return (0); for (i = 0; i < j; i++) { if (*p == '\0') do { if (RAND_bytes(p, 1) <= 0) return (0); } while (*p == '\0'); p++; } memset(p, 3, 8); p += 8; *(p++) = '\0'; memcpy(p, from, (unsigned int)flen); return (1); } /* * Copy of RSA_padding_check_PKCS1_type_2 with a twist that rejects padding * if nul delimiter is preceded by 8 consecutive 0x03 bytes. It also * preserves error code reporting for backward compatibility. */ int RSA_padding_check_SSLv23(unsigned char *to, int tlen, const unsigned char *from, int flen, int num) { int i; /* |em| is the encoded message, zero-padded to exactly |num| bytes */ unsigned char *em = NULL; unsigned int good, found_zero_byte, mask, threes_in_row; int zero_index = 0, msg_index, mlen = -1, err; if (flen < 10) { RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, RSA_R_DATA_TOO_SMALL); return (-1); } em = OPENSSL_malloc(num); if (em == NULL) { RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, ERR_R_MALLOC_FAILURE); return -1; } /* * 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; } from = em; good = constant_time_is_zero(from[0]); good &= constant_time_eq(from[1], 2); err = constant_time_select_int(good, 0, RSA_R_BLOCK_TYPE_IS_NOT_02); mask = ~good; /* scan over padding data */ found_zero_byte = 0; threes_in_row = 0; for (i = 2; i < num; i++) { unsigned int equals0 = constant_time_is_zero(from[i]); zero_index = constant_time_select_int(~found_zero_byte & equals0, i, zero_index); found_zero_byte |= equals0; threes_in_row += 1 & ~found_zero_byte; threes_in_row &= found_zero_byte | constant_time_eq(from[i], 3); } /* * PS must be at least 8 bytes long, and it starts two bytes into |from|. * If we never found a 0-byte, then |zero_index| is 0 and the check * also fails. */ good &= constant_time_ge(zero_index, 2 + 8); err = constant_time_select_int(mask | good, err, RSA_R_NULL_BEFORE_BLOCK_MISSING); mask = ~good; good &= constant_time_lt(threes_in_row, 8); err = constant_time_select_int(mask | good, err, RSA_R_SSLV3_ROLLBACK_ATTACK); mask = ~good; /* * Skip the zero byte. This is incorrect if we never found a zero-byte * but in this case we also do not copy the message out. */ msg_index = zero_index + 1; mlen = num - msg_index; /* * For good measure, do this check in constant time as well. */ good &= constant_time_ge(tlen, mlen); err = constant_time_select_int(mask | good, err, RSA_R_DATA_TOO_LARGE); /* * Even though we can't fake result's length, we can pretend copying * |tlen| bytes where |mlen| bytes would be real. Last |tlen| of |num| * 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(num, tlen), num, tlen); msg_index = constant_time_select_int(good, msg_index, num - tlen); mlen = num - msg_index; for (from += msg_index, mask = good, i = 0; i < tlen; i++) { unsigned int equals = constant_time_eq(i, mlen); from -= tlen & equals; /* if (i == mlen) rewind */ mask &= mask ^ equals; /* if (i == mlen) mask = 0 */ to[i] = constant_time_select_8(mask, from[i], to[i]); } OPENSSL_cleanse(em, num); OPENSSL_free(em); RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, err); err_clear_last_constant_time(1 & good); return constant_time_select_int(good, mlen, -1); }