/* ==================================================================== * Copyright (c) 2012 The OpenSSL Project. All rights reserved. * * 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 above 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 acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" * * 4. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR * ITS 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. * ==================================================================== * * This product includes cryptographic software written by Eric Young * (eay@cryptsoft.com). This product includes software written by Tim * Hudson (tjh@cryptsoft.com). */ #include <assert.h> #include <string.h> #include <openssl_grpc/digest.h> #include <openssl_grpc/nid.h> #include <openssl_grpc/sha.h> #include "../internal.h" #include "internal.h" #include "../fipsmodule/cipher/internal.h" int EVP_tls_cbc_remove_padding(crypto_word_t *out_padding_ok, size_t *out_len, const uint8_t *in, size_t in_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. if (overhead > in_len) { return 0; } 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. if (to_check > in_len) { to_check = in_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. 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. 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. padding_length = good & (padding_length + 1); *out_len = in_len - padding_length; *out_padding_ok = good; return 1; } void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in, size_t in_len, size_t orig_len) { uint8_t rotated_mac1[EVP_MAX_MD_SIZE], rotated_mac2[EVP_MAX_MD_SIZE]; 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. size_t mac_end = in_len; size_t mac_start = mac_end - md_size; assert(orig_len >= in_len); assert(in_len >= md_size); assert(md_size <= EVP_MAX_MD_SIZE); assert(md_size > 0); // 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. if (orig_len > md_size + 255 + 1) { scan_start = orig_len - (md_size + 255 + 1); } size_t rotate_offset = 0; uint8_t mac_started = 0; OPENSSL_memset(rotated_mac, 0, md_size); for (size_t i = scan_start, j = 0; i < orig_len; i++, j++) { if (j >= md_size) { j -= md_size; } crypto_word_t is_mac_start = constant_time_eq_w(i, mac_start); 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. rotate_offset |= j & is_mac_start; } // 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|. 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) { j -= md_size; } rotated_mac_tmp[i] = 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. uint8_t *tmp = rotated_mac; rotated_mac = rotated_mac_tmp; rotated_mac_tmp = tmp; } OPENSSL_memcpy(out, rotated_mac, md_size); } int EVP_sha1_final_with_secret_suffix(SHA_CTX *ctx, uint8_t out[SHA_DIGEST_LENGTH], const uint8_t *in, size_t len, size_t max_len) { // Bound the input length so |total_bits| below fits in four bytes. This is // redundant with TLS record size limits. This also ensures |input_idx| below // does not overflow. size_t max_len_bits = max_len << 3; if (ctx->Nh != 0 || (max_len_bits >> 3) != max_len || // Overflow ctx->Nl + max_len_bits < max_len_bits || ctx->Nl + max_len_bits > UINT32_MAX) { return 0; } // We need to hash the following into |ctx|: // // - ctx->data[:ctx->num] // - in[:len] // - A 0x80 byte // - However many zero bytes are needed to pad up to a block. // - Eight bytes of length. size_t num_blocks = (ctx->num + len + 1 + 8 + SHA_CBLOCK - 1) >> 6; size_t last_block = num_blocks - 1; size_t max_blocks = (ctx->num + max_len + 1 + 8 + SHA_CBLOCK - 1) >> 6; // The bounds above imply |total_bits| fits in four bytes. size_t total_bits = ctx->Nl + (len << 3); uint8_t length_bytes[4]; length_bytes[0] = (uint8_t)(total_bits >> 24); length_bytes[1] = (uint8_t)(total_bits >> 16); length_bytes[2] = (uint8_t)(total_bits >> 8); length_bytes[3] = (uint8_t)total_bits; // We now construct and process each expected block in constant-time. uint8_t block[SHA_CBLOCK] = {0}; uint32_t result[5] = {0}; // input_idx is the index into |in| corresponding to the current block. // However, we allow this index to overflow beyond |max_len|, to simplify the // 0x80 byte. size_t input_idx = 0; for (size_t i = 0; i < max_blocks; i++) { // Fill |block| with data from the partial block in |ctx| and |in|. We copy // as if we were hashing up to |max_len| and then zero the excess later. size_t block_start = 0; if (i == 0) { OPENSSL_memcpy(block, ctx->data, ctx->num); block_start = ctx->num; } if (input_idx < max_len) { size_t to_copy = SHA_CBLOCK - block_start; if (to_copy > max_len - input_idx) { to_copy = max_len - input_idx; } OPENSSL_memcpy(block + block_start, in + input_idx, to_copy); } // Zero any bytes beyond |len| and add the 0x80 byte. for (size_t j = block_start; j < SHA_CBLOCK; j++) { // input[idx] corresponds to block[j]. size_t idx = input_idx + j - block_start; // The barriers on |len| are not strictly necessary. However, without // them, GCC compiles this code by incorporating |len| into the loop // counter and subtracting it out later. This is still constant-time, but // it frustrates attempts to validate this. uint8_t is_in_bounds = constant_time_lt_8(idx, value_barrier_w(len)); uint8_t is_padding_byte = constant_time_eq_8(idx, value_barrier_w(len)); block[j] &= is_in_bounds; block[j] |= 0x80 & is_padding_byte; } input_idx += SHA_CBLOCK - block_start; // Fill in the length if this is the last block. crypto_word_t is_last_block = constant_time_eq_w(i, last_block); for (size_t j = 0; j < 4; j++) { block[SHA_CBLOCK - 4 + j] |= is_last_block & length_bytes[j]; } // Process the block and save the hash state if it is the final value. SHA1_Transform(ctx, block); for (size_t j = 0; j < 5; j++) { result[j] |= is_last_block & ctx->h[j]; } } // Write the output. for (size_t i = 0; i < 5; i++) { CRYPTO_store_u32_be(out + 4 * i, result[i]); } return 1; } int EVP_tls_cbc_record_digest_supported(const EVP_MD *md) { return EVP_MD_type(md) == NID_sha1; } int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out, size_t *md_out_size, const uint8_t header[13], const uint8_t *data, size_t data_size, size_t data_plus_mac_plus_padding_size, const uint8_t *mac_secret, unsigned mac_secret_length) { if (EVP_MD_type(md) != NID_sha1) { // 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; } if (mac_secret_length > SHA_CBLOCK) { // HMAC pads small keys with zeros and hashes large keys down. This function // should never reach the large key case. assert(0); return 0; } // Compute the initial HMAC block. uint8_t hmac_pad[SHA_CBLOCK]; OPENSSL_memset(hmac_pad, 0, sizeof(hmac_pad)); OPENSSL_memcpy(hmac_pad, mac_secret, mac_secret_length); for (size_t i = 0; i < SHA_CBLOCK; i++) { hmac_pad[i] ^= 0x36; } SHA_CTX ctx; SHA1_Init(&ctx); SHA1_Update(&ctx, hmac_pad, SHA_CBLOCK); SHA1_Update(&ctx, header, 13); // There are at most 256 bytes of padding, so we can compute the public // minimum length for |data_size|. size_t min_data_size = 0; if (data_plus_mac_plus_padding_size > SHA_DIGEST_LENGTH + 256) { min_data_size = data_plus_mac_plus_padding_size - SHA_DIGEST_LENGTH - 256; } // Hash the public minimum length directly. This reduces the number of blocks // that must be computed in constant-time. SHA1_Update(&ctx, data, min_data_size); // Hash the remaining data without leaking |data_size|. uint8_t mac_out[SHA_DIGEST_LENGTH]; if (!EVP_sha1_final_with_secret_suffix( &ctx, mac_out, data + min_data_size, data_size - min_data_size, data_plus_mac_plus_padding_size - min_data_size)) { return 0; } // Complete the HMAC in the standard manner. SHA1_Init(&ctx); for (size_t i = 0; i < SHA_CBLOCK; i++) { hmac_pad[i] ^= 0x6a; } SHA1_Update(&ctx, hmac_pad, SHA_CBLOCK); SHA1_Update(&ctx, mac_out, SHA_DIGEST_LENGTH); SHA1_Final(md_out, &ctx); *md_out_size = SHA_DIGEST_LENGTH; return 1; }