path: root/ssl/s3_cbc.c

/*
 * Copyright 2012-2020 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (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
 */

/*
 * This file has no dependencies on the rest of libssl because it is shared
 * with the providers. It contains functions for low level MAC calculations.
 * Responsibility for this lies with the HMAC implementation in the
 * providers. However there are legacy code paths in libssl which also need to
 * do this. In time those legacy code paths can be removed and this file can be
 * moved out of libssl.
 */


/*
 * MD5 and SHA-1 low level APIs are deprecated for public use, but still ok for
 * internal use.
 */
#include "internal/deprecated.h"

#include "internal/constant_time.h"
#include "internal/cryptlib.h"

#include <openssl/evp.h>
#include <openssl/md5.h>
#include <openssl/sha.h>

char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx);
int ssl3_cbc_digest_record(const EVP_MD *md,
                           unsigned char *md_out,
                           size_t *md_out_size,
                           const unsigned char header[13],
                           const unsigned char *data,
                           size_t data_size,
                           size_t data_plus_mac_plus_padding_size,
                           const unsigned char *mac_secret,
                           size_t mac_secret_length, char is_sslv3);

# define l2n(l,c)        (*((c)++)=(unsigned char)(((l)>>24)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>16)&0xff), \
                         *((c)++)=(unsigned char)(((l)>> 8)&0xff), \
                         *((c)++)=(unsigned char)(((l)    )&0xff))

# define l2n6(l,c)       (*((c)++)=(unsigned char)(((l)>>40)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>32)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>24)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>16)&0xff), \
                         *((c)++)=(unsigned char)(((l)>> 8)&0xff), \
                         *((c)++)=(unsigned char)(((l)    )&0xff))

# define l2n8(l,c)       (*((c)++)=(unsigned char)(((l)>>56)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>48)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>40)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>32)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>24)&0xff), \
                         *((c)++)=(unsigned char)(((l)>>16)&0xff), \
                         *((c)++)=(unsigned char)(((l)>> 8)&0xff), \
                         *((c)++)=(unsigned char)(((l)    )&0xff))

/*
 * 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 serializes 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_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_size: the secret, reported length of the data once the MAC and padding
 *              has been removed.
 *   data_plus_mac_plus_padding_size: the public length of the whole
 *     record, including MAC and padding.
 *   is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
 *
 * On entry: we know that data is data_plus_mac_plus_padding_size in length
 * Returns 1 on success or 0 on error
 */
int ssl3_cbc_digest_record(const EVP_MD *md,
                           unsigned char *md_out,
                           size_t *md_out_size,
                           const unsigned char header[13],
                           const unsigned char *data,
                           size_t data_size,
                           size_t data_plus_mac_plus_padding_size,
                           const unsigned char *mac_secret,
                           size_t mac_secret_length, char is_sslv3)
{
    union {
        OSSL_UNION_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 = 0;

    /*
     * 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;

    if (EVP_MD_is_a(md, "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;
    } else if (EVP_MD_is_a(md, "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;
    } else if (EVP_MD_is_a(md, "SHA2-224")) {
        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;
     } else if (EVP_MD_is_a(md, "SHA2-256")) {
        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;
     } else if (EVP_MD_is_a(md, "SHA2-384")) {
        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