diff options
Diffstat (limited to 'src/crypto/cipher_extra/tls_cbc.c')
| -rw-r--r-- | src/crypto/cipher_extra/tls_cbc.c | 208 |
1 files changed, 104 insertions, 104 deletions
diff --git a/src/crypto/cipher_extra/tls_cbc.c b/src/crypto/cipher_extra/tls_cbc.c index 2372c5c0..6f95130a 100644 --- a/src/crypto/cipher_extra/tls_cbc.c +++ b/src/crypto/cipher_extra/tls_cbc.c @@ -62,13 +62,13 @@ #include "../fipsmodule/cipher/internal.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.) */ +// 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.) */ +// 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 int EVP_tls_cbc_remove_padding(crypto_word_t *out_padding_ok, size_t *out_len, @@ -76,7 +76,7 @@ int EVP_tls_cbc_remove_padding(crypto_word_t *out_padding_ok, size_t *out_len, size_t block_size, size_t mac_size) { const size_t overhead = 1 /* padding length byte */ + mac_size; - /* These lengths are all public so we can test them in non-constant time. */ + // These lengths are all public so we can test them in non-constant time. if (overhead > in_len) { return 0; } @@ -84,16 +84,16 @@ int EVP_tls_cbc_remove_padding(crypto_word_t *out_padding_ok, size_t *out_len, size_t padding_length = in[in_len - 1]; crypto_word_t good = constant_time_ge_w(in_len, overhead + padding_length); - /* The padding consists of a length byte at the end of the record and - * then that many bytes of padding, all with the same value as the - * length byte. Thus, with the length byte included, there are i+1 - * bytes of padding. - * - * We can't check just |padding_length+1| bytes because that leaks - * decrypted information. Therefore we always have to check the maximum - * amount of padding possible. (Again, the length of the record is - * public information so we can use it.) */ - size_t to_check = 256; /* maximum amount of padding, inc length byte. */ + // The padding consists of a length byte at the end of the record and + // then that many bytes of padding, all with the same value as the + // length byte. Thus, with the length byte included, there are i+1 + // bytes of padding. + // + // We can't check just |padding_length+1| bytes because that leaks + // decrypted information. Therefore we always have to check the maximum + // amount of padding possible. (Again, the length of the record is + // public information so we can use it.) + size_t to_check = 256; // maximum amount of padding, inc length byte. if (to_check > in_len) { to_check = in_len; } @@ -101,19 +101,19 @@ int EVP_tls_cbc_remove_padding(crypto_word_t *out_padding_ok, size_t *out_len, for (size_t i = 0; i < to_check; i++) { uint8_t mask = constant_time_ge_8(padding_length, i); uint8_t b = in[in_len - 1 - i]; - /* The final |padding_length+1| bytes should all have the value - * |padding_length|. Therefore the XOR should be zero. */ + // The final |padding_length+1| bytes should all have the value + // |padding_length|. Therefore the XOR should be zero. good &= ~(mask & (padding_length ^ b)); } - /* If any of the final |padding_length+1| bytes had the wrong value, - * one or more of the lower eight bits of |good| will be cleared. */ + // If any of the final |padding_length+1| bytes had the wrong value, + // one or more of the lower eight bits of |good| will be cleared. good = constant_time_eq_w(0xff, good & 0xff); - /* Always treat |padding_length| as zero on error. If, assuming block size of - * 16, a padding of [<15 arbitrary bytes> 15] treated |padding_length| as 16 - * and returned -1, distinguishing good MAC and bad padding from bad MAC and - * bad padding would give POODLE's padding oracle. */ + // Always treat |padding_length| as zero on error. If, assuming block size of + // 16, a padding of [<15 arbitrary bytes> 15] treated |padding_length| as 16 + // and returned -1, distinguishing good MAC and bad padding from bad MAC and + // bad padding would give POODLE's padding oracle. padding_length = good & (padding_length + 1); *out_len = in_len - padding_length; *out_padding_ok = good; @@ -126,7 +126,7 @@ void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in, uint8_t *rotated_mac = rotated_mac1; uint8_t *rotated_mac_tmp = rotated_mac2; - /* mac_end is the index of |in| just after the end of the MAC. */ + // mac_end is the index of |in| just after the end of the MAC. size_t mac_end = in_len; size_t mac_start = mac_end - md_size; @@ -134,10 +134,10 @@ void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in, assert(in_len >= md_size); assert(md_size <= EVP_MAX_MD_SIZE); - /* scan_start contains the number of bytes that we can ignore because - * the MAC's position can only vary by 255 bytes. */ + // scan_start contains the number of bytes that we can ignore because + // the MAC's position can only vary by 255 bytes. size_t scan_start = 0; - /* This information is public so it's safe to branch based on it. */ + // This information is public so it's safe to branch based on it. if (orig_len > md_size + 255 + 1) { scan_start = orig_len - (md_size + 255 + 1); } @@ -153,15 +153,15 @@ void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in, mac_started |= is_mac_start; uint8_t mac_ended = constant_time_ge_8(i, mac_end); rotated_mac[j] |= in[i] & mac_started & ~mac_ended; - /* Save the offset that |mac_start| is mapped to. */ + // Save the offset that |mac_start| is mapped to. rotate_offset |= j & is_mac_start; } - /* Now rotate the MAC. We rotate in log(md_size) steps, one for each bit - * position. */ + // Now rotate the MAC. We rotate in log(md_size) steps, one for each bit + // position. for (size_t offset = 1; offset < md_size; offset <<= 1, rotate_offset >>= 1) { - /* Rotate by |offset| iff the corresponding bit is set in - * |rotate_offset|, placing the result in |rotated_mac_tmp|. */ + // Rotate by |offset| iff the corresponding bit is set in + // |rotate_offset|, placing the result in |rotated_mac_tmp|. const uint8_t skip_rotate = (rotate_offset & 1) - 1; for (size_t i = 0, j = offset; i < md_size; i++, j++) { if (j >= md_size) { @@ -171,9 +171,9 @@ void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in, constant_time_select_8(skip_rotate, rotated_mac[i], rotated_mac[j]); } - /* Swap pointers so |rotated_mac| contains the (possibly) rotated value. - * Note the number of iterations and thus the identity of these pointers is - * public information. */ + // Swap pointers so |rotated_mac| contains the (possibly) rotated value. + // Note the number of iterations and thus the identity of these pointers is + // public information. uint8_t *tmp = rotated_mac; rotated_mac = rotated_mac_tmp; rotated_mac_tmp = tmp; @@ -182,8 +182,8 @@ void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in, OPENSSL_memcpy(out, rotated_mac, md_size); } -/* u32toBE serialises an unsigned, 32-bit number (n) as four bytes at (p) in - * big-endian order. The value of p is advanced by four. */ +// u32toBE serialises an unsigned, 32-bit number (n) as four bytes at (p) in +// big-endian order. The value of p is advanced by four. #define u32toBE(n, p) \ do { \ *((p)++) = (uint8_t)((n) >> 24); \ @@ -192,8 +192,8 @@ void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in, *((p)++) = (uint8_t)((n)); \ } while (0) -/* u64toBE serialises an unsigned, 64-bit number (n) as eight bytes at (p) in - * big-endian order. The value of p is advanced by eight. */ +// u64toBE serialises an unsigned, 64-bit number (n) as eight bytes at (p) in +// big-endian order. The value of p is advanced by eight. #define u64toBE(n, p) \ do { \ *((p)++) = (uint8_t)((n) >> 56); \ @@ -224,9 +224,9 @@ static void tls1_sha512_transform(HASH_CTX *ctx, const uint8_t *block) { SHA512_Transform(&ctx->sha512, block); } -/* 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. */ +// 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_sha1_final_raw(HASH_CTX *ctx, uint8_t *md_out) { SHA_CTX *sha1 = &ctx->sha1; u32toBE(sha1->h[0], md_out); @@ -272,13 +272,13 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, void (*md_final_raw)(HASH_CTX *ctx, uint8_t *md_out); void (*md_transform)(HASH_CTX *ctx, const uint8_t *block); unsigned md_size, md_block_size = 64; - /* md_length_size is the number of bytes in the length field that terminates - * the hash. */ + // md_length_size is the number of bytes in the length field that terminates + // the hash. unsigned md_length_size = 8; - /* Bound the acceptable input so we can forget about many possible overflows - * later in this function. This is redundant with the record size limits in - * TLS. */ + // Bound the acceptable input so we can forget about many possible overflows + // later in this function. This is redundant with the record size limits in + // TLS. if (data_plus_mac_plus_padding_size >= 1024 * 1024) { assert(0); return 0; @@ -309,8 +309,8 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, break; default: - /* EVP_tls_cbc_record_digest_supported should have been called first to - * check that the hash function is supported. */ + // EVP_tls_cbc_record_digest_supported should have been called first to + // check that the hash function is supported. assert(0); *md_out_size = 0; return 0; @@ -322,45 +322,45 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, static const size_t kHeaderLength = 13; - /* kVarianceBlocks 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. - * - * 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 six blocks - * can vary based on the padding. */ + // kVarianceBlocks 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. + // + // 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 six blocks + // can vary based on the padding. static const size_t kVarianceBlocks = 6; - /* From now on we're dealing with the MAC, which conceptually has 13 - * bytes of `header' before the start of the data. */ + // From now on we're dealing with the MAC, which conceptually has 13 + // bytes of `header' before the start of the data. size_t len = data_plus_mac_plus_padding_size + kHeaderLength; - /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including - * |header|, assuming that there's no padding. */ + // max_mac_bytes contains the maximum bytes of bytes in the MAC, including + // |header|, assuming that there's no padding. size_t max_mac_bytes = len - md_size - 1; - /* num_blocks is the maximum number of hash blocks. */ + // num_blocks is the maximum number of hash blocks. size_t 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 |kVarianceBlocks| 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. */ + // 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 |kVarianceBlocks| 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. size_t num_starting_blocks = 0; - /* k is the starting byte offset into the conceptual header||data where - * we start processing. */ + // k is the starting byte offset into the conceptual header||data where + // we start processing. size_t k = 0; - /* mac_end_offset is the index just past the end of the data to be - * MACed. */ + // mac_end_offset is the index just past the end of the data to be + // MACed. size_t mac_end_offset = data_plus_mac_size + kHeaderLength - md_size; - /* c is the index of the 0x80 byte in the final hash block that - * contains application data. */ + // c is the index of the 0x80 byte in the final hash block that + // contains application data. size_t c = mac_end_offset % md_block_size; - /* index_a is the hash block number that contains the 0x80 terminating - * value. */ + // index_a is the hash block number that contains the 0x80 terminating + // value. size_t 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 is the hash block number that contains the 64-bit hash + // length, in bits. size_t index_b = (mac_end_offset + md_length_size) / md_block_size; if (num_blocks > kVarianceBlocks) { @@ -368,13 +368,13 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, k = md_block_size * num_starting_blocks; } - /* bits is the hash-length in bits. It includes the additional hash - * block for the masked HMAC key. */ - size_t bits = 8 * mac_end_offset; /* at most 18 bits to represent */ + // bits is the hash-length in bits. It includes the additional hash + // block for the masked HMAC key. + size_t bits = 8 * mac_end_offset; // at most 18 bits to represent - /* Compute the initial HMAC block. */ + // Compute the initial HMAC block. bits += 8 * md_block_size; - /* hmac_pad is the masked HMAC key. */ + // hmac_pad is the masked HMAC key. uint8_t hmac_pad[MAX_HASH_BLOCK_SIZE]; OPENSSL_memset(hmac_pad, 0, md_block_size); assert(mac_secret_length <= sizeof(hmac_pad)); @@ -385,7 +385,7 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, md_transform(&md_state, hmac_pad); - /* The length check means |bits| fits in four bytes. */ + // The length check means |bits| fits in four bytes. uint8_t length_bytes[MAX_HASH_BIT_COUNT_BYTES]; OPENSSL_memset(length_bytes, 0, md_length_size - 4); length_bytes[md_length_size - 4] = (uint8_t)(bits >> 24); @@ -394,7 +394,7 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, length_bytes[md_length_size - 1] = (uint8_t)bits; if (k > 0) { - /* k is a multiple of md_block_size. */ + // k is a multiple of md_block_size. uint8_t first_block[MAX_HASH_BLOCK_SIZE]; OPENSSL_memcpy(first_block, header, 13); OPENSSL_memcpy(first_block + 13, data, md_block_size - 13); @@ -407,10 +407,10 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, uint8_t mac_out[EVP_MAX_MD_SIZE]; OPENSSL_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|. */ + // 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 (size_t i = num_starting_blocks; i <= num_starting_blocks + kVarianceBlocks; i++) { uint8_t block[MAX_HASH_BLOCK_SIZE]; @@ -427,24 +427,24 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, uint8_t is_past_c = is_block_a & constant_time_ge_8(j, c); uint8_t is_past_cp1 = is_block_a & constant_time_ge_8(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. */ + // 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 the the block containing the end of the - * application data and we're past the 0x80 value then - * just write zero. */ + // If this the the block containing 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. */ + // 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. */ + // 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. */ + // 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); } @@ -453,7 +453,7 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, md_transform(&md_state, block); md_final_raw(&md_state, block); - /* If this is index_b, copy the hash value to |mac_out|. */ + // If this is index_b, copy the hash value to |mac_out|. for (size_t j = 0; j < md_size; j++) { mac_out[j] |= block[j] & is_block_b; } @@ -466,7 +466,7 @@ int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, return 0; } - /* Complete the HMAC in the standard manner. */ + // Complete the HMAC in the standard manner. for (size_t i = 0; i < md_block_size; i++) { hmac_pad[i] ^= 0x6a; } |