/*

 * 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;

}