s3_cbc.c revision 296341
11541Srgrimes/* ssl/s3_cbc.c */ 21541Srgrimes/* ==================================================================== 31541Srgrimes * Copyright (c) 2012 The OpenSSL Project. All rights reserved. 45455Sdg * 55455Sdg * Redistribution and use in source and binary forms, with or without 61541Srgrimes * modification, are permitted provided that the following conditions 71541Srgrimes * are met: 81541Srgrimes * 91541Srgrimes * 1. Redistributions of source code must retain the above copyright 101541Srgrimes * notice, this list of conditions and the following disclaimer. 111541Srgrimes * 121541Srgrimes * 2. Redistributions in binary form must reproduce the above copyright 131541Srgrimes * notice, this list of conditions and the following disclaimer in 141541Srgrimes * the documentation and/or other materials provided with the 151541Srgrimes * distribution. 161541Srgrimes * 171541Srgrimes * 3. All advertising materials mentioning features or use of this 181541Srgrimes * software must display the following acknowledgment: 191541Srgrimes * "This product includes software developed by the OpenSSL Project 201541Srgrimes * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 211541Srgrimes * 221541Srgrimes * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 231541Srgrimes * endorse or promote products derived from this software without 241541Srgrimes * prior written permission. For written permission, please contact 251541Srgrimes * openssl-core@openssl.org. 261541Srgrimes * 271541Srgrimes * 5. Products derived from this software may not be called "OpenSSL" 281541Srgrimes * nor may "OpenSSL" appear in their names without prior written 291541Srgrimes * permission of the OpenSSL Project. 301541Srgrimes * 311541Srgrimes * 6. Redistributions of any form whatsoever must retain the following 321541Srgrimes * acknowledgment: 331541Srgrimes * "This product includes software developed by the OpenSSL Project 34116182Sobrien * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 35116182Sobrien * 36116182Sobrien * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 3732929Seivind * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 3832929Seivind * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 391541Srgrimes * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 401549Srgrimes * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 4141168Sbde * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 421541Srgrimes * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 4360041Sphk * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 441541Srgrimes * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 451541Srgrimes * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 4641124Sdg * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 471541Srgrimes * OF THE POSSIBILITY OF SUCH DAMAGE. 481541Srgrimes * ==================================================================== 4968885Sdillon * 506621Sdg * This product includes cryptographic software written by Eric Young 5110541Sdyson * (eay@cryptsoft.com). This product includes software written by Tim 5210541Sdyson * Hudson (tjh@cryptsoft.com). 5348545Smckusick * 541541Srgrimes */ 5521002Sdyson 5621002Sdyson#include "../crypto/constant_time_locl.h" 5791690Seivind#include "ssl_locl.h" 5891690Seivind 5921002Sdyson#include <openssl/md5.h> 6021002Sdyson#include <openssl/sha.h> 61167214Swkoszek 6241124Sdg/* 63251897Sscottl * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's 64251897Sscottl * length field. (SHA-384/512 have 128-bit length.) 65251897Sscottl */ 66251897Sscottl#define MAX_HASH_BIT_COUNT_BYTES 16 67251897Sscottl 68141628Sphk/* 691541Srgrimes * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support. 7048545Smckusick * Currently SHA-384/512 has a 128-byte block size and that's the largest 7191690Seivind * supported by TLS.) 7291690Seivind */ 7348545Smckusick#define MAX_HASH_BLOCK_SIZE 128 74219699Sivoras 75112080Sjeff/*- 76112080Sjeff * ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC 77112080Sjeff * record in |rec| by updating |rec->length| in constant time. 78250906Sscottl * 79250906Sscottl * block_size: the block size of the cipher used to encrypt the record. 80250906Sscottl * returns: 81250906Sscottl * 0: (in non-constant time) if the record is publicly invalid. 8291690Seivind * 1: if the padding was valid 8312973Sbde * -1: otherwise. 845455Sdg */ 8591690Seivindint ssl3_cbc_remove_padding(const SSL *s, 8691690Seivind SSL3_RECORD *rec, 8791690Seivind unsigned block_size, unsigned mac_size) 8810541Sdyson{ 891549Srgrimes unsigned padding_length, good; 90251144Sscottl const unsigned overhead = 1 /* padding length byte */ + mac_size; 91251144Sscottl 921541Srgrimes /* 93251144Sscottl * These lengths are all public so we can test them in non-constant time. 94251144Sscottl */ 95251144Sscottl if (overhead > rec->length) 96251144Sscottl return 0; 97251144Sscottl 98251144Sscottl padding_length = rec->data[rec->length - 1]; 99251144Sscottl good = constant_time_ge(rec->length, padding_length + overhead); 100251144Sscottl /* SSLv3 requires that the padding is minimal. */ 101251144Sscottl good &= constant_time_ge(block_size, padding_length + 1); 102251144Sscottl padding_length = good & (padding_length + 1); 10321002Sdyson rec->length -= padding_length; 104177493Sjeff rec->type |= padding_length << 8; /* kludge: pass padding length */ 10596572Sphk return constant_time_select_int(good, 1, -1); 106112080Sjeff} 107112080Sjeff 10810541Sdyson/*- 1091541Srgrimes * tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC 1101541Srgrimes * record in |rec| in constant time and returns 1 if the padding is valid and 111177493Sjeff * -1 otherwise. It also removes any explicit IV from the start of the record 112251897Sscottl * without leaking any timing about whether there was enough space after the 113251897Sscottl * padding was removed. 11421002Sdyson * 1155455Sdg * block_size: the block size of the cipher used to encrypt the record. 11621002Sdyson * returns: 11721002Sdyson * 0: (in non-constant time) if the record is publicly invalid. 11821002Sdyson * 1: if the padding was valid 11951797Sphk * -1: otherwise. 120112080Sjeff */ 121112080Sjeffint tls1_cbc_remove_padding(const SSL *s, 122112080Sjeff SSL3_RECORD *rec, 123112080Sjeff unsigned block_size, unsigned mac_size) 124112080Sjeff{ 12521002Sdyson unsigned padding_length, good, to_check, i; 12621002Sdyson const unsigned overhead = 1 /* padding length byte */ + mac_size; 1275455Sdg /* Check if version requires explicit IV */ 1285455Sdg if (s->version >= TLS1_1_VERSION || s->version == DTLS1_BAD_VER) { 129251897Sscottl /* 13021002Sdyson * These lengths are all public so we can test them in non-constant 13112767Sdyson * time. 1325455Sdg */ 1335455Sdg if (overhead + block_size > rec->length) 1345455Sdg return 0; 1355455Sdg /* We can now safely skip explicit IV */ 1365455Sdg rec->data += block_size; 1371541Srgrimes rec->input += block_size; 13821002Sdyson rec->length -= block_size; 1395455Sdg } else if (overhead > rec->length) 14021002Sdyson return 0; 14121002Sdyson 14221002Sdyson padding_length = rec->data[rec->length - 1]; 14321002Sdyson 144177493Sjeff /* 14548225Smckusick * NB: if compression is in operation the first packet may not be of even 14699737Sdillon * length so the padding bug check cannot be performed. This bug 14799737Sdillon * workaround has been around since SSLeay so hopefully it is either 14899737Sdillon * fixed now or no buggy implementation supports compression [steve] 14999737Sdillon */ 150136767Sphk if ((s->options & SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand) { 151112080Sjeff /* First packet is even in size, so check */ 15221002Sdyson if ((CRYPTO_memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0", 8) == 0) && 15321002Sdyson !(padding_length & 1)) { 15421002Sdyson s->s3->flags |= TLS1_FLAGS_TLS_PADDING_BUG; 15548677Smckusick } 156151621Sups if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && padding_length > 0) { 157151621Sups padding_length--; 15821002Sdyson } 159151621Sups } 160151621Sups 161151621Sups if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) { 162151621Sups /* padding is already verified */ 163112080Sjeff rec->length -= padding_length + 1; 164151621Sups return 1; 165151621Sups } 16621002Sdyson 167177493Sjeff good = constant_time_ge(rec->length, overhead + padding_length); 16821002Sdyson /* 1695839Sdg * The padding consists of a length byte at the end of the record and 17010541Sdyson * then that many bytes of padding, all with the same value as the length 17121002Sdyson * byte. Thus, with the length byte included, there are i+1 bytes of 17221002Sdyson * padding. We can't check just |padding_length+1| bytes because that 17321002Sdyson * leaks decrypted information. Therefore we always have to check the 174111886Sjeff * maximum amount of padding possible. (Again, the length of the record 175111886Sjeff * is public information so we can use it.) 176111886Sjeff */ 177111886Sjeff to_check = 255; /* maximum amount of padding. */ 17821002Sdyson if (to_check > rec->length - 1) 17942453Seivind to_check = rec->length - 1; 180111886Sjeff 181250906Sscottl for (i = 0; i < to_check; i++) { 18242453Seivind unsigned char mask = constant_time_ge_8(padding_length, i); 18342408Seivind unsigned char b = rec->data[rec->length - 1 - i]; 18442453Seivind /* 185111886Sjeff * The final |padding_length+1| bytes should all have the value 186112080Sjeff * |padding_length|. Therefore the XOR should be zero. 187111886Sjeff */ 188111886Sjeff good &= ~(mask & (padding_length ^ b)); 189250906Sscottl } 190250906Sscottl 191250906Sscottl /* 192250906Sscottl * If any of the final |padding_length+1| bytes had the wrong value, one 193250906Sscottl * or more of the lower eight bits of |good| will be cleared. 194250906Sscottl */ 195250906Sscottl good = constant_time_eq(0xff, good & 0xff); 196111886Sjeff padding_length = good & (padding_length + 1); 197111886Sjeff rec->length -= padding_length; 198111886Sjeff rec->type |= padding_length << 8; /* kludge: pass padding length */ 19921002Sdyson 20021002Sdyson return constant_time_select_int(good, 1, -1); 201111886Sjeff} 202111886Sjeff 203111886Sjeff/*- 20421002Sdyson * ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in 205111886Sjeff * constant time (independent of the concrete value of rec->length, which may 206111886Sjeff * vary within a 256-byte window). 207111886Sjeff * 208111886Sjeff * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to 20921002Sdyson * this function. 210112080Sjeff * 211111886Sjeff * On entry: 212111886Sjeff * rec->orig_len >= md_size 213111886Sjeff * md_size <= EVP_MAX_MD_SIZE 214111886Sjeff * 215112080Sjeff * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with 216111886Sjeff * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into 21721002Sdyson * a single or pair of cache-lines, then the variable memory accesses don't 218111886Sjeff * actually affect the timing. CPUs with smaller cache-lines [if any] are 219111886Sjeff * not multi-core and are not considered vulnerable to cache-timing attacks. 220111886Sjeff */ 221111886Sjeff#define CBC_MAC_ROTATE_IN_PLACE 222112080Sjeff 223111886Sjeffvoid ssl3_cbc_copy_mac(unsigned char *out, 224112080Sjeff const SSL3_RECORD *rec, 225112080Sjeff unsigned md_size, unsigned orig_len) 226112080Sjeff{ 22721002Sdyson#if defined(CBC_MAC_ROTATE_IN_PLACE) 228251897Sscottl unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE]; 22934694Sdyson unsigned char *rotated_mac; 23010541Sdyson#else 23158345Sphk unsigned char rotated_mac[EVP_MAX_MD_SIZE]; 23258345Sphk#endif 23310541Sdyson 2348876Srgrimes /* 2351541Srgrimes * mac_end is the index of |rec->data| just after the end of the MAC. 2365455Sdg */ 2375455Sdg unsigned mac_end = rec->length; 238112080Sjeff unsigned mac_start = mac_end - md_size; 2395455Sdg /* 2405455Sdg * scan_start contains the number of bytes that we can ignore because the 24170374Sdillon * MAC's position can only vary by 255 bytes. 24236275Sdyson */ 24370374Sdillon unsigned scan_start = 0; 24458934Sphk unsigned i, j; 24558934Sphk unsigned div_spoiler; 24658345Sphk unsigned rotate_offset; 24748333Speter 248121205Sphk OPENSSL_assert(orig_len >= md_size); 249136927Sphk OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); 250170174Sjeff 2515455Sdg#if defined(CBC_MAC_ROTATE_IN_PLACE) 25234611Sdyson rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63); 2535455Sdg#endif 254112080Sjeff 2555455Sdg /* This information is public so it's safe to branch based on it. */ 256112080Sjeff if (orig_len > md_size + 255 + 1) 257112080Sjeff scan_start = orig_len - (md_size + 255 + 1); 258112080Sjeff /* 259112080Sjeff * div_spoiler contains a multiple of md_size that is used to cause the 260112080Sjeff * modulo operation to be constant time. Without this, the time varies 261112080Sjeff * based on the amount of padding when running on Intel chips at least. 262112080Sjeff * The aim of right-shifting md_size is so that the compiler doesn't 263112080Sjeff * figure out that it can remove div_spoiler as that would require it to 264112080Sjeff * prove that md_size is always even, which I hope is beyond it. 265112080Sjeff */ 266112080Sjeff div_spoiler = md_size >> 1; 267112080Sjeff div_spoiler <<= (sizeof(div_spoiler) - 1) * 8; 268112080Sjeff rotate_offset = (div_spoiler + mac_start - scan_start) % md_size; 269112080Sjeff 270112080Sjeff memset(rotated_mac, 0, md_size); 271112080Sjeff for (i = scan_start, j = 0; i < orig_len; i++) { 272251897Sscottl unsigned char mac_started = constant_time_ge_8(i, mac_start); 273112080Sjeff unsigned char mac_ended = constant_time_ge_8(i, mac_end); 274112838Sjeff unsigned char b = rec->data[i]; 275112838Sjeff rotated_mac[j++] |= b & mac_started & ~mac_ended; 276112838Sjeff j &= constant_time_lt(j, md_size); 277112838Sjeff } 278112080Sjeff 279251897Sscottl /* Now rotate the MAC */ 280112838Sjeff#if defined(CBC_MAC_ROTATE_IN_PLACE) 281112838Sjeff j = 0; 282112838Sjeff for (i = 0; i < md_size; i++) { 283112838Sjeff /* in case cache-line is 32 bytes, touch second line */ 284112838Sjeff ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32]; 285112080Sjeff out[j++] = rotated_mac[rotate_offset++]; 286112080Sjeff rotate_offset &= constant_time_lt(rotate_offset, md_size); 287112080Sjeff } 288112080Sjeff#else 289112080Sjeff memset(out, 0, md_size); 29058345Sphk rotate_offset = md_size - rotate_offset; 29113490Sdyson rotate_offset &= constant_time_lt(rotate_offset, md_size); 292112080Sjeff for (i = 0; i < md_size; i++) { 2935455Sdg for (j = 0; j < md_size; j++) 294112080Sjeff out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset); 295112080Sjeff rotate_offset++; 296112080Sjeff rotate_offset &= constant_time_lt(rotate_offset, md_size); 297112080Sjeff } 298112080Sjeff#endif 299112080Sjeff} 300112080Sjeff 301121205Sphk/* 302136927Sphk * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in 303170174Sjeff * little-endian order. The value of p is advanced by four. 3045455Sdg */ 305112080Sjeff#define u32toLE(n, p) \ 30621002Sdyson (*((p)++)=(unsigned char)(n), \ 30759762Sphk *((p)++)=(unsigned char)(n>>8), \ 30821002Sdyson *((p)++)=(unsigned char)(n>>16), \ 30921002Sdyson *((p)++)=(unsigned char)(n>>24)) 3101541Srgrimes 3111541Srgrimes/* 3121541Srgrimes * These functions serialize the state of a hash and thus perform the 3131541Srgrimes * standard "final" operation without adding the padding and length that such 3141541Srgrimes * a function typically does. 3151541Srgrimes */ 3161541Srgrimesstatic void tls1_md5_final_raw(void *ctx, unsigned char *md_out) 31710541Sdyson{ 318251897Sscottl MD5_CTX *md5 = ctx; 319251897Sscottl u32toLE(md5->A, md_out); 3201541Srgrimes u32toLE(md5->B, md_out); 321177493Sjeff u32toLE(md5->C, md_out); 32210541Sdyson u32toLE(md5->D, md_out); 3231541Srgrimes} 324195122Salc 325195122Salcstatic void tls1_sha1_final_raw(void *ctx, unsigned char *md_out) 326195122Salc{ 3271541Srgrimes SHA_CTX *sha1 = ctx; 32842408Seivind l2n(sha1->h0, md_out); 329122537Smckusick l2n(sha1->h1, md_out); 330122537Smckusick l2n(sha1->h2, md_out); 33142453Seivind l2n(sha1->h3, md_out); 33212767Sdyson l2n(sha1->h4, md_out); 33312767Sdyson} 33412767Sdyson 33512767Sdyson#define LARGEST_DIGEST_CTX SHA_CTX 3361541Srgrimes 33712767Sdyson#ifndef OPENSSL_NO_SHA256 33810541Sdysonstatic void tls1_sha256_final_raw(void *ctx, unsigned char *md_out) 33921002Sdyson{ 34021002Sdyson SHA256_CTX *sha256 = ctx; 34158345Sphk unsigned i; 34221002Sdyson 343251897Sscottl for (i = 0; i < 8; i++) { 34421002Sdyson l2n(sha256->h[i], md_out); 34521002Sdyson } 34658345Sphk} 34758345Sphk 34821002Sdyson# undef LARGEST_DIGEST_CTX 34910541Sdyson# define LARGEST_DIGEST_CTX SHA256_CTX 35016086Sdyson#endif 35116086Sdyson 35210541Sdyson#ifndef OPENSSL_NO_SHA512 35310541Sdysonstatic void tls1_sha512_final_raw(void *ctx, unsigned char *md_out) 35442957Sdillon{ 35510541Sdyson SHA512_CTX *sha512 = ctx; 35610541Sdyson unsigned i; 35710541Sdyson 35885272Sdillon for (i = 0; i < 8; i++) { 35985272Sdillon l2n8(sha512->h[i], md_out); 36085272Sdillon } 36185272Sdillon} 36285272Sdillon 36385272Sdillon# undef LARGEST_DIGEST_CTX 36458345Sphk# define LARGEST_DIGEST_CTX SHA512_CTX 365251897Sscottl#endif 366251897Sscottl 367251897Sscottl/* 368251897Sscottl * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function 369251897Sscottl * which ssl3_cbc_digest_record supports. 370251897Sscottl */ 371251897Sscottlchar ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) 37258345Sphk{ 3735455Sdg#ifdef OPENSSL_FIPS 3745455Sdg if (FIPS_mode()) 3755455Sdg return 0; 37634611Sdyson#endif 37742453Seivind switch (EVP_MD_CTX_type(ctx)) { 3785455Sdg case NID_md5: 3791541Srgrimes case NID_sha1: 38012404Sdyson#ifndef OPENSSL_NO_SHA256 3811541Srgrimes case NID_sha224: 3825455Sdg case NID_sha256: 3835455Sdg#endif 3845455Sdg#ifndef OPENSSL_NO_SHA512 3855455Sdg case NID_sha384: 3861541Srgrimes case NID_sha512: 387177493Sjeff#endif 38810541Sdyson return 1; 3895455Sdg default: 39012767Sdyson return 0; 39185272Sdillon } 39210541Sdyson} 39385272Sdillon 39410978Sdyson/*- 395251897Sscottl * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS 396251897Sscottl * record. 39712767Sdyson * 398111886Sjeff * ctx: the EVP_MD_CTX from which we take the hash function. 399111886Sjeff * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX. 400111886Sjeff * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written. 40134611Sdyson * md_out_size: if non-NULL, the number of output bytes is written here. 40271230Sdillon * header: the 13-byte, TLS record header. 40385272Sdillon * data: the record data itself, less any preceeding explicit IV. 40485272Sdillon * data_plus_mac_size: the secret, reported length of the data and MAC 40585272Sdillon * once the padding has been removed. 40685272Sdillon * data_plus_mac_plus_padding_size: the public length of the whole 40785272Sdillon * record, including padding. 40871230Sdillon * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS. 409177493Sjeff * 410119521Sjeff * On entry: by virtue of having been through one of the remove_padding 411119521Sjeff * functions, above, we know that data_plus_mac_size is large enough to contain 412119521Sjeff * a padding byte and MAC. (If the padding was invalid, it might contain the 413177493Sjeff * padding too. ) 41413490Sdyson */ 4155455Sdgvoid ssl3_cbc_digest_record(const EVP_MD_CTX *ctx, 4165455Sdg unsigned char *md_out, 417177493Sjeff size_t *md_out_size, 41810541Sdyson const unsigned char header[13], 41985272Sdillon const unsigned char *data, 42085272Sdillon size_t data_plus_mac_size, 42185272Sdillon size_t data_plus_mac_plus_padding_size, 42285272Sdillon const unsigned char *mac_secret, 42385272Sdillon unsigned mac_secret_length, char is_sslv3) 424195122Salc{ 425195122Salc union { 426137010Sphk double align; 427195122Salc unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; 428195122Salc } md_state; 429195122Salc void (*md_final_raw) (void *ctx, unsigned char *md_out); 430195122Salc void (*md_transform) (void *ctx, const unsigned char *block); 431195122Salc unsigned md_size, md_block_size = 64; 432121269Salc unsigned sslv3_pad_length = 40, header_length, variance_blocks, 433121269Salc len, max_mac_bytes, num_blocks, 434195122Salc num_starting_blocks, k, mac_end_offset, c, index_a, index_b; 435195122Salc unsigned int bits; /* at most 18 bits */ 43610541Sdyson unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES]; 437195122Salc /* hmac_pad is the masked HMAC key. */ 438195122Salc unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE]; 43971230Sdillon unsigned char first_block[MAX_HASH_BLOCK_SIZE]; 440137010Sphk unsigned char mac_out[EVP_MAX_MD_SIZE]; 441195122Salc unsigned i, j, md_out_size_u; 44234611Sdyson EVP_MD_CTX md_ctx; 44310541Sdyson /* 44410541Sdyson * mdLengthSize is the number of bytes in the length field that 44510541Sdyson * terminates * the hash. 44685272Sdillon */ 44785272Sdillon unsigned md_length_size = 8; 44885272Sdillon char length_is_big_endian = 1; 44921002Sdyson 45021002Sdyson /* 45185272Sdillon * This is a, hopefully redundant, check that allows us to forget about 45285272Sdillon * many possible overflows later in this function. 45385272Sdillon */ 45485272Sdillon OPENSSL_assert(data_plus_mac_plus_padding_size < 1024 * 1024); 45585272Sdillon 45685272Sdillon switch (EVP_MD_CTX_type(ctx)) { 45785272Sdillon case NID_md5: 45885272Sdillon MD5_Init((MD5_CTX *)md_state.c); 45958345Sphk md_final_raw = tls1_md5_final_raw; 46058345Sphk md_transform = 46112767Sdyson (void (*)(void *ctx, const unsigned char *block))MD5_Transform; 46210541Sdyson md_size = 16; 46310541Sdyson sslv3_pad_length = 48; 46410541Sdyson length_is_big_endian = 0; 46510541Sdyson break; 46610541Sdyson case NID_sha1: 4671541Srgrimes SHA1_Init((SHA_CTX *)md_state.c); 46848333Speter md_final_raw = tls1_sha1_final_raw; 46948333Speter md_transform = 47048333Speter (void (*)(void *ctx, const unsigned char *block))SHA1_Transform; 47148333Speter md_size = 20; 47248333Speter break; 47312404Sdyson#ifndef OPENSSL_NO_SHA256 47412404Sdyson case NID_sha224: 475137010Sphk SHA224_Init((SHA256_CTX *)md_state.c); 4765455Sdg md_final_raw = tls1_sha256_final_raw; 47710541Sdyson md_transform = 47810541Sdyson (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; 47938799Sdfr md_size = 224 / 8; 48038517Sdfr break; 48110541Sdyson case NID_sha256: 48212413Sdyson SHA256_Init((SHA256_CTX *)md_state.c); 48310541Sdyson md_final_raw = tls1_sha256_final_raw; 48410541Sdyson md_transform = 48510541Sdyson (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; 486193643Salc md_size = 32; 48718737Sdyson break; 4881541Srgrimes#endif 489137010Sphk#ifndef OPENSSL_NO_SHA512 49085511Sdillon case NID_sha384: 49185511Sdillon SHA384_Init((SHA512_CTX *)md_state.c); 49285511Sdillon md_final_raw = tls1_sha512_final_raw; 49385511Sdillon md_transform = 49485511Sdillon (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; 49585511Sdillon md_size = 384 / 8; 49685511Sdillon md_block_size = 128; 49785511Sdillon md_length_size = 16; 49885511Sdillon break; 49985511Sdillon case NID_sha512: 50085511Sdillon SHA512_Init((SHA512_CTX *)md_state.c); 5011541Srgrimes md_final_raw = tls1_sha512_final_raw; 50218737Sdyson md_transform = 50385272Sdillon (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; 50485272Sdillon md_size = 64; 50585272Sdillon md_block_size = 128; 50685272Sdillon md_length_size = 16; 507137010Sphk break; 50885272Sdillon#endif 509121269Salc default: 510193643Salc /* 51118737Sdyson * ssl3_cbc_record_digest_supported should have been called first to 51218737Sdyson * check that the hash function is supported. 513137010Sphk */ 51420054Sdyson OPENSSL_assert(0); 51537559Sbde if (md_out_size) 51637559Sbde *md_out_size = -1; 51720054Sdyson return; 51818737Sdyson } 519251897Sscottl 520251897Sscottl OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES); 521251897Sscottl OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE); 522251897Sscottl OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); 5235455Sdg 5241541Srgrimes header_length = 13; 5251541Srgrimes if (is_sslv3) { 5261541Srgrimes header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence 5271541Srgrimes * number */ + 5281541Srgrimes 1 /* record type */ + 5291541Srgrimes 2 /* record length */ ; 5301541Srgrimes } 5311541Srgrimes 532141628Sphk /* 5331541Srgrimes * variance_blocks is the number of blocks of the hash that we have to 5341541Srgrimes * calculate in constant time because they could be altered by the 5351541Srgrimes * padding value. In SSLv3, the padding must be minimal so the end of 53612404Sdyson * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively 5371541Srgrimes * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes 5381541Srgrimes * of hash termination (0x80 + 64-bit length) don't fit in the final 5391541Srgrimes * block, we say that the final two blocks can vary based on the padding. 5401541Srgrimes * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not 5411541Srgrimes * required to be minimal. Therefore we say that the final six blocks can 54258934Sphk * vary based on the padding. Later in the function, if the message is 5431541Srgrimes * short and there obviously cannot be this many blocks then 5441541Srgrimes * variance_blocks can be reduced. 545251897Sscottl */ 546251897Sscottl variance_blocks = is_sslv3 ? 2 : 6; 547251897Sscottl /* 548251897Sscottl * From now on we're dealing with the MAC, which conceptually has 13 5491541Srgrimes * bytes of `header' before the start of the data (TLS) or 71/75 bytes 5501541Srgrimes * (SSLv3) 5511541Srgrimes */ 5521541Srgrimes len = data_plus_mac_plus_padding_size + header_length; 55321002Sdyson /* 55412404Sdyson * max_mac_bytes contains the maximum bytes of bytes in the MAC, 55521002Sdyson * including * |header|, assuming that there's no padding. 5561541Srgrimes */ 55758934Sphk max_mac_bytes = len - md_size - 1; 5581541Srgrimes /* num_blocks is the maximum number of hash blocks. */ 55946349Salc num_blocks = 56046349Salc (max_mac_bytes + 1 + md_length_size + md_block_size - 56158934Sphk 1) / md_block_size; 56258934Sphk /* 56377115Sdillon * In order to calculate the MAC in constant time we have to handle the 56477115Sdillon * final blocks specially because the padding value could cause the end 56577115Sdillon * to appear somewhere in the final |variance_blocks| blocks and we can't 56677115Sdillon * leak where. However, |num_starting_blocks| worth of data can be hashed 56777115Sdillon * right away because no padding value can affect whether they are 56877115Sdillon * plaintext. 56977115Sdillon */ 57077115Sdillon num_starting_blocks = 0; 57177115Sdillon /* 57246349Salc * k is the starting byte offset into the conceptual header||data where 57359249Sphk * we start processing. 5741541Srgrimes */ 575137719Sphk k = 0; 57642957Sdillon /* 5771541Srgrimes * mac_end_offset is the index just past the end of the data to be MACed. 5781541Srgrimes */ 5791541Srgrimes mac_end_offset = data_plus_mac_size + header_length - md_size; 58048545Smckusick /* 58148545Smckusick * c is the index of the 0x80 byte in the final hash block that contains 58248545Smckusick * application data. 58348545Smckusick */ 58448545Smckusick c = mac_end_offset % md_block_size; 58548545Smckusick /* 58648545Smckusick * index_a is the hash block number that contains the 0x80 terminating 58748545Smckusick * value. 58848545Smckusick */ 58948545Smckusick index_a = mac_end_offset / md_block_size; 590251897Sscottl /* 591251897Sscottl * index_b is the hash block number that contains the 64-bit hash length, 59248545Smckusick * in bits. 59348545Smckusick */ 59448545Smckusick index_b = (mac_end_offset + md_length_size) / md_block_size; 595250947Sscottl /* 59648545Smckusick * bits is the hash-length in bits. It includes the additional hash block 59748545Smckusick * for the masked HMAC key, or whole of |header| in the case of SSLv3. 59848545Smckusick */ 59948545Smckusick 600102412Scharnier /* 60148545Smckusick * For SSLv3, if we're going to have any starting blocks then we need at 602251897Sscottl * least two because the header is larger than a single block. 603102412Scharnier */ 60448545Smckusick if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) { 605102412Scharnier num_starting_blocks = num_blocks - variance_blocks; 60648545Smckusick k = md_block_size * num_starting_blocks; 60748545Smckusick } 60848545Smckusick 60948545Smckusick bits = 8 * mac_end_offset; 61048545Smckusick if (!is_sslv3) { 61148545Smckusick /* 6121541Srgrimes * Compute the initial HMAC block. For SSLv3, the padding and secret 6131541Srgrimes * bytes are included in |header| because they take more than a 6141541Srgrimes * single block. 6151541Srgrimes */ 6161541Srgrimes bits += 8 * md_block_size; 6171541Srgrimes memset(hmac_pad, 0, md_block_size); 6181541Srgrimes OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad)); 6191541Srgrimes memcpy(hmac_pad, mac_secret, mac_secret_length); 6201541Srgrimes for (i = 0; i < md_block_size; i++) 6211541Srgrimes hmac_pad[i] ^= 0x36; 622135858Sphk 6231541Srgrimes md_transform(md_state.c, hmac_pad); 624251144Sscottl } 625251144Sscottl 626251144Sscottl if (length_is_big_endian) { 627251144Sscottl memset(length_bytes, 0, md_length_size - 4); 628251144Sscottl length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24); 629251144Sscottl length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16); 630251144Sscottl length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8); 631251144Sscottl length_bytes[md_length_size - 1] = (unsigned char)bits; 6325455Sdg } else { 6335455Sdg memset(length_bytes, 0, md_length_size); 6345455Sdg length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24); 63512404Sdyson length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16); 6361541Srgrimes length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8); 637251897Sscottl length_bytes[md_length_size - 8] = (unsigned char)bits; 638251897Sscottl } 639251897Sscottl 64032286Sdyson if (k > 0) { 641231936Skib if (is_sslv3) { 64232286Sdyson unsigned overhang; 64332286Sdyson 64432286Sdyson /* 64532286Sdyson * The SSLv3 header is larger than a single block. overhang is 64632286Sdyson * the number of bytes beyond a single block that the header 6475455Sdg * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no 64842408Seivind * ciphersuites in SSLv3 that are not SHA1 or MD5 based and 64934694Sdyson * therefore we can be confident that the header_length will be 6501541Srgrimes * greater than |md_block_size|. However we add a sanity check just 6511541Srgrimes * in case 6521541Srgrimes */ 6531541Srgrimes if (header_length <= md_block_size) { 6545455Sdg /* Should never happen */ 6555455Sdg return; 65651797Sphk } 6571541Srgrimes overhang = header_length - md_block_size; 6581541Srgrimes md_transform(md_state.c, header); 6591541Srgrimes memcpy(first_block, header + md_block_size, overhang); 6608876Srgrimes memcpy(first_block + overhang, data, md_block_size - overhang); 6611541Srgrimes md_transform(md_state.c, first_block); 6625455Sdg for (i = 1; i < k / md_block_size - 1; i++) 6635455Sdg md_transform(md_state.c, data + md_block_size * i - overhang); 6645455Sdg } else { 6655455Sdg /* k is a multiple of md_block_size. */ 66658909Sdillon memcpy(first_block, header, 13); 66758909Sdillon memcpy(first_block + 13, data, md_block_size - 13); 66858909Sdillon md_transform(md_state.c, first_block); 66958909Sdillon for (i = 1; i < k / md_block_size; i++) 67058909Sdillon md_transform(md_state.c, data + md_block_size * i - 13); 67158909Sdillon } 67258909Sdillon } 6731541Srgrimes 6741541Srgrimes memset(mac_out, 0, sizeof(mac_out)); 67534611Sdyson 67610541Sdyson /* 67758909Sdillon * We now process the final hash blocks. For each block, we construct it 67848677Smckusick * in constant time. If the |i==index_a| then we'll include the 0x80 679251897Sscottl * bytes and zero pad etc. For each block we selectively copy it, in 68058909Sdillon * constant time, to |mac_out|. 68110541Sdyson */ 68210541Sdyson for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks; 68310541Sdyson i++) { 68410541Sdyson unsigned char block[MAX_HASH_BLOCK_SIZE]; 685251897Sscottl unsigned char is_block_a = constant_time_eq_8(i, index_a); 68610541Sdyson unsigned char is_block_b = constant_time_eq_8(i, index_b); 68710541Sdyson for (j = 0; j < md_block_size; j++) { 68810541Sdyson unsigned char b = 0, is_past_c, is_past_cp1; 68910541Sdyson if (k < header_length) 69058909Sdillon b = header[k]; 69158909Sdillon else if (k < data_plus_mac_plus_padding_size + header_length) 69258909Sdillon b = data[k - header_length]; 69358909Sdillon k++; 69458909Sdillon 69558909Sdillon is_past_c = is_block_a & constant_time_ge_8(j, c); 69610541Sdyson is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1); 69710541Sdyson /* 69810541Sdyson * If this is the block containing the end of the application 69910541Sdyson * data, and we are at the offset for the 0x80 value, then 70010541Sdyson * overwrite b with 0x80. 70158909Sdillon */ 70258909Sdillon b = constant_time_select_8(is_past_c, 0x80, b); 70358909Sdillon /* 704251897Sscottl * If this the the block containing the end of the application 70558909Sdillon * data and we're past the 0x80 value then just write zero. 70610541Sdyson */ 70710541Sdyson b = b & ~is_past_cp1; 70810541Sdyson /* 70910541Sdyson * If this is index_b (the final block), but not index_a (the end 71010541Sdyson * of the data), then the 64-bit length didn't fit into index_a 71110541Sdyson * and we're having to add an extra block of zeros. 71210541Sdyson */ 71310541Sdyson b &= ~is_block_b | is_block_a; 71410541Sdyson 71510541Sdyson /* 71610541Sdyson * The final bytes of one of the blocks contains the length. 71710541Sdyson */ 71810541Sdyson if (j >= md_block_size - md_length_size) { 7191541Srgrimes /* If this is index_b, write a length byte. */ 7201541Srgrimes b = constant_time_select_8(is_block_b, 7215455Sdg length_bytes[j - 7225455Sdg (md_block_size - 7235455Sdg md_length_size)], b); 7241541Srgrimes } 72532286Sdyson block[j] = b; 72634611Sdyson } 7277613Sdg 72810551Sdyson md_transform(md_state.c, block); 72910541Sdyson md_final_raw(md_state.c, block); 7301541Srgrimes /* If this is index_b, copy the hash value to |mac_out|. */ 7311541Srgrimes for (j = 0; j < md_size; j++) 7321541Srgrimes mac_out[j] |= block[j] & is_block_b; 7331541Srgrimes } 7341541Srgrimes 7351541Srgrimes EVP_MD_CTX_init(&md_ctx); 7361541Srgrimes EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */ ); 7375455Sdg if (is_sslv3) { 73812404Sdyson /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */ 7391541Srgrimes memset(hmac_pad, 0x5c, sslv3_pad_length); 74013490Sdyson 7415455Sdg EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length); 7421541Srgrimes EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length); 7435455Sdg EVP_DigestUpdate(&md_ctx, mac_out, md_size); 7441541Srgrimes } else { 7451541Srgrimes /* Complete the HMAC in the standard manner. */ 7461541Srgrimes for (i = 0; i < md_block_size; i++) 74758909Sdillon hmac_pad[i] ^= 0x6a; 74858909Sdillon 74958909Sdillon EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size); 7501541Srgrimes EVP_DigestUpdate(&md_ctx, mac_out, md_size); 75112404Sdyson } 752251897Sscottl EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u); 753251897Sscottl if (md_out_size) 754251897Sscottl *md_out_size = md_out_size_u; 755251897Sscottl EVP_MD_CTX_cleanup(&md_ctx); 7561541Srgrimes} 7571541Srgrimes 75868885Sdillon#ifdef OPENSSL_FIPS 75968885Sdillon 76068885Sdillon/* 76168885Sdillon * Due to the need to use EVP in FIPS mode we can't reimplement digests but 76268885Sdillon * we can ensure the number of blocks processed is equal for all cases by 76358909Sdillon * digesting additional data. 7641541Srgrimes */ 7655455Sdg 7661541Srgrimesvoid tls_fips_digest_extra(const EVP_CIPHER_CTX *cipher_ctx, 7671541Srgrimes EVP_MD_CTX *mac_ctx, const unsigned char *data, 76858909Sdillon size_t data_len, size_t orig_len) 7691541Srgrimes{ 7701541Srgrimes size_t block_size, digest_pad, blocks_data, blocks_orig; 7711541Srgrimes if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE) 7721541Srgrimes return; 7731541Srgrimes block_size = EVP_MD_CTX_block_size(mac_ctx); 7741541Srgrimes /*- 7751541Srgrimes * We are in FIPS mode if we get this far so we know we have only SHA* 7761541Srgrimes * digests and TLS to deal with. 7771541Srgrimes * Minimum digest padding length is 17 for SHA384/SHA512 and 9 7781541Srgrimes * otherwise. 7791541Srgrimes * Additional header is 13 bytes. To get the number of digest blocks 78012767Sdyson * processed round up the amount of data plus padding to the nearest 781251144Sscottl * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise. 7821541Srgrimes * So we have: 783251144Sscottl * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size 784251144Sscottl * equivalently: 785251144Sscottl * blocks = (payload_len + digest_pad + 12)/block_size + 1 786251144Sscottl * HMAC adds a constant overhead. 787251144Sscottl * We're ultimately only interested in differences so this becomes 788251144Sscottl * blocks = (payload_len + 29)/128 789251144Sscottl * for SHA384/SHA512 and 790251144Sscottl * blocks = (payload_len + 21)/64 79112404Sdyson * otherwise. 792177493Sjeff */ 793145734Sjeff digest_pad = block_size == 64 ? 21 : 29; 79412767Sdyson blocks_orig = (orig_len + digest_pad) / block_size; 79512404Sdyson blocks_data = (data_len + digest_pad) / block_size; 79635595Sbde /* 797251897Sscottl * MAC enough blocks to make up the difference between the original and 798251897Sscottl * actual lengths plus one extra block to ensure this is never a no op. 799251897Sscottl * The "data" pointer should always have enough space to perform this 800177493Sjeff * operation as it is large enough for a maximum length TLS buffer. 80112767Sdyson */ 80271230Sdillon EVP_DigestSignUpdate(mac_ctx, data, 80371230Sdillon (blocks_orig - blocks_data + 1) * block_size); 80471230Sdillon} 80572080Sasmodai#endif 80671230Sdillon