| /* |
| * Copyright 2012-2021 The OpenSSL Project Authors. All Rights Reserved. |
| * |
| * Licensed under the OpenSSL license (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.h" |
| #include "ssl_local.h" |
| #include "internal/cryptlib.h" |
| |
| #include <openssl/md5.h> |
| #include <openssl/sha.h> |
| |
| /* |
| * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's |
| * length field. (SHA-384/512 have 128-bit length.) |
| */ |
| #define MAX_HASH_BIT_COUNT_BYTES 16 |
| |
| /* |
| * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support. |
| * Currently SHA-384/512 has a 128-byte block size and that's the largest |
| * supported by TLS.) |
| */ |
| #define MAX_HASH_BLOCK_SIZE 128 |
| |
| /* |
| * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in |
| * little-endian order. The value of p is advanced by four. |
| */ |
| #define u32toLE(n, p) \ |
| (*((p)++)=(unsigned char)(n), \ |
| *((p)++)=(unsigned char)(n>>8), \ |
| *((p)++)=(unsigned char)(n>>16), \ |
| *((p)++)=(unsigned char)(n>>24)) |
| |
| /* |
| * These functions serialize the state of a hash and thus perform the |
| * standard "final" operation without adding the padding and length that such |
| * a function typically does. |
| */ |
| static void tls1_md5_final_raw(void *ctx, unsigned char *md_out) |
| { |
| MD5_CTX *md5 = ctx; |
| u32toLE(md5->A, md_out); |
| u32toLE(md5->B, md_out); |
| u32toLE(md5->C, md_out); |
| u32toLE(md5->D, md_out); |
| } |
| |
| static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out) |
| { |
| SHA_CTX *sha1 = ctx; |
| l2n(sha1->h0, md_out); |
| l2n(sha1->h1, md_out); |
| l2n(sha1->h2, md_out); |
| l2n(sha1->h3, md_out); |
| l2n(sha1->h4, md_out); |
| } |
| |
| static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out) |
| { |
| SHA256_CTX *sha256 = ctx; |
| unsigned i; |
| |
| for (i = 0; i < 8; i++) { |
| l2n(sha256->h[i], md_out); |
| } |
| } |
| |
| static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out) |
| { |
| SHA512_CTX *sha512 = ctx; |
| unsigned i; |
| |
| for (i = 0; i < 8; i++) { |
| l2n8(sha512->h[i], md_out); |
| } |
| } |
| |
| #undef LARGEST_DIGEST_CTX |
| #define LARGEST_DIGEST_CTX SHA512_CTX |
| |
| /* |
| * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function |
| * which ssl3_cbc_digest_record supports. |
| */ |
| char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) |
| { |
| switch (EVP_MD_CTX_type(ctx)) { |
| case NID_md5: |
| case NID_sha1: |
| case NID_sha224: |
| case NID_sha256: |
| case NID_sha384: |
| case NID_sha512: |
| return 1; |
| default: |
| return 0; |
| } |
| } |
| |
| /*- |
| * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS |
| * record. |
| * |
| * ctx: the EVP_MD_CTX from which we take the hash function. |
| * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX. |
| * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written. |
| * md_out_size: if non-NULL, the number of output bytes is written here. |
| * header: the 13-byte, TLS record header. |
| * data: the record data itself, less any preceding explicit IV. |
| * data_plus_mac_size: the secret, reported length of the data and MAC |
| * once the padding has been removed. |
| * data_plus_mac_plus_padding_size: the public length of the whole |
| * record, including padding. |
| * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS. |
| * |
| * On entry: by virtue of having been through one of the remove_padding |
| * functions, above, we know that data_plus_mac_size is large enough to contain |
| * a padding byte and MAC. (If the padding was invalid, it might contain the |
| * padding too. ) |
| * Returns 1 on success or 0 on error |
| */ |
| int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx, |
| unsigned char *md_out, |
| size_t *md_out_size, |
| const unsigned char *header, |
| const unsigned char *data, |
| size_t data_plus_mac_size, |
| size_t data_plus_mac_plus_padding_size, |
| const unsigned char *mac_secret, |
| size_t mac_secret_length, char is_sslv3) |
| { |
| union { |
| double align; |
| unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; |
| } md_state; |
| void (*md_final_raw) (void *ctx, unsigned char *md_out); |
| void (*md_transform) (void *ctx, const unsigned char *block); |
| size_t md_size, md_block_size = 64; |
| size_t sslv3_pad_length = 40, header_length, variance_blocks, |
| len, max_mac_bytes, num_blocks, |
| num_starting_blocks, k, mac_end_offset, c, index_a, index_b; |
| size_t bits; /* at most 18 bits */ |
| unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES]; |
| /* hmac_pad is the masked HMAC key. */ |
| unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE]; |
| unsigned char first_block[MAX_HASH_BLOCK_SIZE]; |
| unsigned char mac_out[EVP_MAX_MD_SIZE]; |
| size_t i, j; |
| unsigned md_out_size_u; |
| EVP_MD_CTX *md_ctx = NULL; |
| /* |
| * mdLengthSize is the number of bytes in the length field that |
| * terminates * the hash. |
| */ |
| size_t md_length_size = 8; |
| char length_is_big_endian = 1; |
| int ret; |
| |
| /* |
| * This is a, hopefully redundant, check that allows us to forget about |
| * many possible overflows later in this function. |
| */ |
| if (!ossl_assert(data_plus_mac_plus_padding_size < 1024 * 1024)) |
| return 0; |
| |
| switch (EVP_MD_CTX_type(ctx)) { |
| case NID_md5: |
| if (MD5_Init((MD5_CTX *)md_state.c) <= 0) |
| return 0; |
| md_final_raw = tls1_md5_final_raw; |
| md_transform = |
| (void (*)(void *ctx, const unsigned char *block))MD5_Transform; |
| md_size = 16; |
| sslv3_pad_length = 48; |
| length_is_big_endian = 0; |
| break; |
| case NID_sha1: |
| if (SHA1_Init((SHA_CTX *)md_state.c) <= 0) |
| return 0; |
| md_final_raw = tls1_sha1_final_raw; |
| md_transform = |
| (void (*)(void *ctx, const unsigned char *block))SHA1_Transform; |
| md_size = 20; |
| break; |
| case NID_sha224: |
| if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0) |
| return 0; |
| md_final_raw = tls1_sha256_final_raw; |
| md_transform = |
| (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; |
| md_size = 224 / 8; |
| break; |
| case NID_sha256: |
| if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0) |
| return 0; |
| md_final_raw = tls1_sha256_final_raw; |
| md_transform = |
| (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; |
| md_size = 32; |
| break; |
| case NID_sha384: |
| if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0) |
| return 0; |
| md_final_raw = tls1_sha512_final_raw; |
| md_transform = |
| (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; |
| md_size = 384 / 8; |
| md_block_size = 128; |
| md_length_size = 16; |
| break; |
| case NID_sha512: |
| if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0) |
| return 0; |
| md_final_raw = tls1_sha512_final_raw; |
| md_transform = |
| (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; |
| md_size = 64; |
| md_block_size = 128; |
| md_length_size = 16; |
| break; |
| default: |
| /* |
| * ssl3_cbc_record_digest_supported should have been called first to |
| * check that the hash function is supported. |
| */ |
| if (md_out_size != NULL) |
| *md_out_size = 0; |
| return ossl_assert(0); |
| } |
| |
| if (!ossl_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES) |
| || !ossl_assert(md_block_size <= MAX_HASH_BLOCK_SIZE) |
| || !ossl_assert(md_size <= EVP_MAX_MD_SIZE)) |
| return 0; |
| |
| header_length = 13; |
| if (is_sslv3) { |
| header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence |
| * number */ + |
| 1 /* record type */ + |
| 2 /* record length */ ; |
| } |
| |
| /* |
| * variance_blocks is the number of blocks of the hash that we have to |
| * calculate in constant time because they could be altered by the |
| * padding value. In SSLv3, the padding must be minimal so the end of |
| * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively |
| * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes |
| * of hash termination (0x80 + 64-bit length) don't fit in the final |
| * block, we say that the final two blocks can vary based on the padding. |
| * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not |
| * required to be minimal. Therefore we say that the final |variance_blocks| |
| * blocks can |
| * vary based on the padding. Later in the function, if the message is |
| * short and there obviously cannot be this many blocks then |
| * variance_blocks can be reduced. |
| */ |
| variance_blocks = is_sslv3 ? 2 : ( ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1); |
| /* |
| * From now on we're dealing with the MAC, which conceptually has 13 |
| * bytes of `header' before the start of the data (TLS) or 71/75 bytes |
| * (SSLv3) |
| */ |
| len = data_plus_mac_plus_padding_size + header_length; |
| /* |
| * max_mac_bytes contains the maximum bytes of bytes in the MAC, |
| * including * |header|, assuming that there's no padding. |
| */ |
| max_mac_bytes = len - md_size - 1; |
| /* num_blocks is the maximum number of hash blocks. */ |
| num_blocks = |
| (max_mac_bytes + 1 + md_length_size + md_block_size - |
| 1) / md_block_size; |
| /* |
| * In order to calculate the MAC in constant time we have to handle the |
| * final blocks specially because the padding value could cause the end |
| * to appear somewhere in the final |variance_blocks| blocks and we can't |
| * leak where. However, |num_starting_blocks| worth of data can be hashed |
| * right away because no padding value can affect whether they are |
| * plaintext. |
| */ |
| num_starting_blocks = 0; |
| /* |
| * k is the starting byte offset into the conceptual header||data where |
| * we start processing. |
| */ |
| k = 0; |
| /* |
| * mac_end_offset is the index just past the end of the data to be MACed. |
| */ |
| mac_end_offset = data_plus_mac_size + header_length - md_size; |
| /* |
| * c is the index of the 0x80 byte in the final hash block that contains |
| * application data. |
| */ |
| c = mac_end_offset % md_block_size; |
| /* |
| * index_a is the hash block number that contains the 0x80 terminating |
| * value. |
| */ |
| index_a = mac_end_offset / md_block_size; |
| /* |
| * index_b is the hash block number that contains the 64-bit hash length, |
| * in bits. |
| */ |
| index_b = (mac_end_offset + md_length_size) / md_block_size; |
| /* |
| * bits is the hash-length in bits. It includes the additional hash block |
| * for the masked HMAC key, or whole of |header| in the case of SSLv3. |
| */ |
| |
| /* |
| * For SSLv3, if we're going to have any starting blocks then we need at |
| * least two because the header is larger than a single block. |
| */ |
| if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) { |
| num_starting_blocks = num_blocks - variance_blocks; |
| k = md_block_size * num_starting_blocks; |
| } |
| |
| bits = 8 * mac_end_offset; |
| if (!is_sslv3) { |
| /* |
| * Compute the initial HMAC block. For SSLv3, the padding and secret |
| * bytes are included in |header| because they take more than a |
| * single block. |
| */ |
| bits += 8 * md_block_size; |
| memset(hmac_pad, 0, md_block_size); |
| if (!ossl_assert(mac_secret_length <= sizeof(hmac_pad))) |
| return 0; |
| memcpy(hmac_pad, mac_secret, mac_secret_length); |
| for (i = 0; i < md_block_size; i++) |
| hmac_pad[i] ^= 0x36; |
| |
| md_transform(md_state.c, hmac_pad); |
| } |
| |
| if (length_is_big_endian) { |
| memset(length_bytes, 0, md_length_size - 4); |
| length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24); |
| length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16); |
| length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8); |
| length_bytes[md_length_size - 1] = (unsigned char)bits; |
| } else { |
| memset(length_bytes, 0, md_length_size); |
| length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24); |
| length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16); |
| length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8); |
| length_bytes[md_length_size - 8] = (unsigned char)bits; |
| } |
| |
| if (k > 0) { |
| if (is_sslv3) { |
| size_t overhang; |
| |
| /* |
| * The SSLv3 header is larger than a single block. overhang is |
| * the number of bytes beyond a single block that the header |
| * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no |
| * ciphersuites in SSLv3 that are not SHA1 or MD5 based and |
| * therefore we can be confident that the header_length will be |
| * greater than |md_block_size|. However we add a sanity check just |
| * in case |
| */ |
| if (header_length <= md_block_size) { |
| /* Should never happen */ |
| return 0; |
| } |
| overhang = header_length - md_block_size; |
| md_transform(md_state.c, header); |
| memcpy(first_block, header + md_block_size, overhang); |
| memcpy(first_block + overhang, data, md_block_size - overhang); |
| md_transform(md_state.c, first_block); |
| for (i = 1; i < k / md_block_size - 1; i++) |
| md_transform(md_state.c, data + md_block_size * i - overhang); |
| } else { |
| /* k is a multiple of md_block_size. */ |
| memcpy(first_block, header, 13); |
| memcpy(first_block + 13, data, md_block_size - 13); |
| md_transform(md_state.c, first_block); |
| for (i = 1; i < k / md_block_size; i++) |
| md_transform(md_state.c, data + md_block_size * i - 13); |
| } |
| } |
| |
| memset(mac_out, 0, sizeof(mac_out)); |
| |
| /* |
| * We now process the final hash blocks. For each block, we construct it |
| * in constant time. If the |i==index_a| then we'll include the 0x80 |
| * bytes and zero pad etc. For each block we selectively copy it, in |
| * constant time, to |mac_out|. |
| */ |
| for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks; |
| i++) { |
| unsigned char block[MAX_HASH_BLOCK_SIZE]; |
| unsigned char is_block_a = constant_time_eq_8_s(i, index_a); |
| unsigned char is_block_b = constant_time_eq_8_s(i, index_b); |
| for (j = 0; j < md_block_size; j++) { |
| unsigned char b = 0, is_past_c, is_past_cp1; |
| if (k < header_length) |
| b = header[k]; |
| else if (k < data_plus_mac_plus_padding_size + header_length) |
| b = data[k - header_length]; |
| k++; |
| |
| is_past_c = is_block_a & constant_time_ge_8_s(j, c); |
| is_past_cp1 = is_block_a & constant_time_ge_8_s(j, c + 1); |
| /* |
| * If this is the block containing the end of the application |
| * data, and we are at the offset for the 0x80 value, then |
| * overwrite b with 0x80. |
| */ |
| b = constant_time_select_8(is_past_c, 0x80, b); |
| /* |
| * If this block contains the end of the application data |
| * and we're past the 0x80 value then just write zero. |
| */ |
| b = b & ~is_past_cp1; |
| /* |
| * If this is index_b (the final block), but not index_a (the end |
| * of the data), then the 64-bit length didn't fit into index_a |
| * and we're having to add an extra block of zeros. |
| */ |
| b &= ~is_block_b | is_block_a; |
| |
| /* |
| * The final bytes of one of the blocks contains the length. |
| */ |
| if (j >= md_block_size - md_length_size) { |
| /* If this is index_b, write a length byte. */ |
| b = constant_time_select_8(is_block_b, |
| length_bytes[j - |
| (md_block_size - |
| md_length_size)], b); |
| } |
| block[j] = b; |
| } |
| |
| md_transform(md_state.c, block); |
| md_final_raw(md_state.c, block); |
| /* If this is index_b, copy the hash value to |mac_out|. */ |
| for (j = 0; j < md_size; j++) |
| mac_out[j] |= block[j] & is_block_b; |
| } |
| |
| md_ctx = EVP_MD_CTX_new(); |
| if (md_ctx == NULL) |
| goto err; |
| if (EVP_DigestInit_ex(md_ctx, EVP_MD_CTX_md(ctx), NULL /* engine */ ) <= 0) |
| goto err; |
| if (is_sslv3) { |
| /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */ |
| memset(hmac_pad, 0x5c, sslv3_pad_length); |
| |
| if (EVP_DigestUpdate(md_ctx, mac_secret, mac_secret_length) <= 0 |
| || EVP_DigestUpdate(md_ctx, hmac_pad, sslv3_pad_length) <= 0 |
| || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0) |
| goto err; |
| } else { |
| /* Complete the HMAC in the standard manner. */ |
| for (i = 0; i < md_block_size; i++) |
| hmac_pad[i] ^= 0x6a; |
| |
| if (EVP_DigestUpdate(md_ctx, hmac_pad, md_block_size) <= 0 |
| || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0) |
| goto err; |
| } |
| /* TODO(size_t): Convert me */ |
| ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u); |
| if (ret && md_out_size) |
| *md_out_size = md_out_size_u; |
| EVP_MD_CTX_free(md_ctx); |
| |
| return 1; |
| err: |
| EVP_MD_CTX_free(md_ctx); |
| return 0; |
| } |