lib/crypto/sm2.cpp

/*-
 * Copyright (c) 2017 Ribose Inc.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR 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.
 */

#include <string.h>
#include <botan/ffi.h>
#include "sm2.h"
#include "hash.h"
#include "utils.h"
#include "bn.h"

static bool
sm2_load_public_key(botan_pubkey_t *pubkey, const pgp_ec_key_t *keydata)
{
    const ec_curve_desc_t *curve = NULL;
    botan_mp_t             px = NULL;
    botan_mp_t             py = NULL;
    size_t                 sz;
    bool                   res = false;

    if (!(curve = get_curve_desc(keydata->curve))) {
        return false;
    }

    const size_t sign_half_len = BITS_TO_BYTES(curve->bitlen);
    sz = mpi_bytes(&keydata->p);
    if (!sz || (sz != (2 * sign_half_len + 1)) || (keydata->p.mpi[0] != 0x04)) {
        goto end;
    }

    if (botan_mp_init(&px) || botan_mp_init(&py) ||
        botan_mp_from_bin(px, &keydata->p.mpi[1], sign_half_len) ||
        botan_mp_from_bin(py, &keydata->p.mpi[1 + sign_half_len], sign_half_len)) {
        goto end;
    }
    res = !botan_pubkey_load_sm2(pubkey, px, py, curve->botan_name);
end:
    botan_mp_destroy(px);
    botan_mp_destroy(py);
    return res;
}

static bool
sm2_load_secret_key(botan_privkey_t *seckey, const pgp_ec_key_t *keydata)
{
    const ec_curve_desc_t *curve = NULL;
    bignum_t *             x = NULL;
    bool                   res = false;

    if (!(curve = get_curve_desc(keydata->curve))) {
        return false;
    }
    if (!(x = mpi2bn(&keydata->x))) {
        return false;
    }
    res = !botan_privkey_load_sm2(seckey, BN_HANDLE_PTR(x), curve->botan_name);
    bn_free(x);
    return res;
}

rnp_result_t
sm2_compute_za(const pgp_ec_key_t &key, rnp::Hash &hash, const char *ident_field)
{
    rnp_result_t   result = RNP_ERROR_GENERIC;
    botan_pubkey_t sm2_key = NULL;
    int            rc;

    const char *hash_algo = rnp::Hash::name_backend(hash.alg());
    size_t      digest_len = hash.size();

    uint8_t *digest_buf = (uint8_t *) malloc(digest_len);
    if (!digest_buf) {
        return RNP_ERROR_OUT_OF_MEMORY;
    }

    if (!sm2_load_public_key(&sm2_key, &key)) {
        RNP_LOG("Failed to load SM2 key");
        goto done;
    }

    if (ident_field == NULL)
        ident_field = "1234567812345678";

    rc = botan_pubkey_sm2_compute_za(digest_buf, &digest_len, ident_field, hash_algo, sm2_key);

    if (rc != 0) {
        RNP_LOG("compute_za failed %d", rc);
        goto done;
    }

    try {
        hash.add(digest_buf, digest_len);
    } catch (const std::exception &e) {
        RNP_LOG("Failed to update hash: %s", e.what());
        goto done;
    }

    result = RNP_SUCCESS;
done:
    free(digest_buf);
    botan_pubkey_destroy(sm2_key);
    return result;
}

rnp_result_t
sm2_validate_key(rnp::RNG *rng, const pgp_ec_key_t *key, bool secret)
{
    botan_pubkey_t  bpkey = NULL;
    botan_privkey_t bskey = NULL;
    rnp_result_t    ret = RNP_ERROR_BAD_PARAMETERS;

    if (!sm2_load_public_key(&bpkey, key) || botan_pubkey_check_key(bpkey, rng->handle(), 0)) {
        goto done;
    }

    if (!secret) {
        ret = RNP_SUCCESS;
        goto done;
    }

    if (!sm2_load_secret_key(&bskey, key) ||
        botan_privkey_check_key(bskey, rng->handle(), 0)) {
        goto done;
    }
    ret = RNP_SUCCESS;
done:
    botan_privkey_destroy(bskey);
    botan_pubkey_destroy(bpkey);
    return ret;
}

rnp_result_t
sm2_sign(rnp::RNG *          rng,
         pgp_ec_signature_t *sig,
         pgp_hash_alg_t      hash_alg,
         const uint8_t *     hash,
         size_t              hash_len,
         const pgp_ec_key_t *key)
{
    const ec_curve_desc_t *curve = NULL;
    botan_pk_op_sign_t     signer = NULL;
    botan_privkey_t        b_key = NULL;
    uint8_t                out_buf[2 * MAX_CURVE_BYTELEN] = {0};
    size_t                 sign_half_len = 0;
    size_t                 sig_len = 0;
    rnp_result_t           ret = RNP_ERROR_SIGNING_FAILED;

    if (botan_ffi_supports_api(20180713) != 0) {
        RNP_LOG("SM2 signatures requires Botan 2.8 or higher");
        return RNP_ERROR_NOT_SUPPORTED;
    }

    if (hash_len != rnp::Hash::size(hash_alg)) {
        return RNP_ERROR_BAD_PARAMETERS;
    }

    if (!(curve = get_curve_desc(key->curve))) {
        return RNP_ERROR_BAD_PARAMETERS;
    }
    sign_half_len = BITS_TO_BYTES(curve->bitlen);
    sig_len = 2 * sign_half_len;

    if (!sm2_load_secret_key(&b_key, key)) {
        RNP_LOG("Can't load private key");
        ret = RNP_ERROR_BAD_PARAMETERS;
        goto end;
    }

    if (botan_pk_op_sign_create(&signer, b_key, ",Raw", 0)) {
        goto end;
    }

    if (botan_pk_op_sign_update(signer, hash, hash_len)) {
        goto end;
    }

    if (botan_pk_op_sign_finish(signer, rng->handle(), out_buf, &sig_len)) {
        RNP_LOG("Signing failed");
        goto end;
    }

    // Allocate memory and copy results
    if (mem2mpi(&sig->r, out_buf, sign_half_len) &&
        mem2mpi(&sig->s, out_buf + sign_half_len, sign_half_len)) {
        // All good now
        ret = RNP_SUCCESS;
    }
end:
    botan_privkey_destroy(b_key);
    botan_pk_op_sign_destroy(signer);
    return ret;
}

rnp_result_t
sm2_verify(const pgp_ec_signature_t *sig,
           pgp_hash_alg_t            hash_alg,
           const uint8_t *           hash,
           size_t                    hash_len,
           const pgp_ec_key_t *      key)
{
    const ec_curve_desc_t *curve = NULL;
    botan_pubkey_t         pub = NULL;
    botan_pk_op_verify_t   verifier = NULL;
    rnp_result_t           ret = RNP_ERROR_SIGNATURE_INVALID;
    uint8_t                sign_buf[2 * MAX_CURVE_BYTELEN] = {0};
    size_t                 r_blen, s_blen, sign_half_len;

    if (botan_ffi_supports_api(20180713) != 0) {
        RNP_LOG("SM2 signatures requires Botan 2.8 or higher");
        return RNP_ERROR_NOT_SUPPORTED;
    }

    if (hash_len != rnp::Hash::size(hash_alg)) {
        return RNP_ERROR_BAD_PARAMETERS;
    }

    curve = get_curve_desc(key->curve);
    if (curve == NULL) {
        return RNP_ERROR_BAD_PARAMETERS;
    }
    sign_half_len = BITS_TO_BYTES(curve->bitlen);

    if (!sm2_load_public_key(&pub, key)) {
        RNP_LOG("Failed to load public key");
        goto end;
    }

    if (botan_pk_op_verify_create(&verifier, pub, ",Raw", 0)) {
        goto end;
    }

    if (botan_pk_op_verify_update(verifier, hash, hash_len)) {
        goto end;
    }

    r_blen = sig->r.len;
    s_blen = sig->s.len;
    if (!r_blen || (r_blen > sign_half_len) || !s_blen || (s_blen > sign_half_len) ||
        (sign_half_len > MAX_CURVE_BYTELEN)) {
        goto end;
    }

    mpi2mem(&sig->r, sign_buf + sign_half_len - r_blen);
    mpi2mem(&sig->s, sign_buf + 2 * sign_half_len - s_blen);

    if (!botan_pk_op_verify_finish(verifier, sign_buf, sign_half_len * 2)) {
        ret = RNP_SUCCESS;
    }
end:
    botan_pubkey_destroy(pub);
    botan_pk_op_verify_destroy(verifier);
    return ret;
}

rnp_result_t
sm2_encrypt(rnp::RNG *           rng,
            pgp_sm2_encrypted_t *out,
            const uint8_t *      in,
            size_t               in_len,
            pgp_hash_alg_t       hash_algo,
            const pgp_ec_key_t * key)
{
    rnp_result_t           ret = RNP_ERROR_GENERIC;
    const ec_curve_desc_t *curve = NULL;
    botan_pubkey_t         sm2_key = NULL;
    botan_pk_op_encrypt_t  enc_op = NULL;
    size_t                 point_len;
    size_t                 hash_alg_len;
    size_t                 ctext_len;

    curve = get_curve_desc(key->curve);
    if (curve == NULL) {
        return RNP_ERROR_GENERIC;
    }
    point_len = BITS_TO_BYTES(curve->bitlen);
    hash_alg_len = rnp::Hash::size(hash_algo);
    if (!hash_alg_len) {
        RNP_LOG("Unknown hash algorithm for SM2 encryption");
        goto done;
    }

    /*
     * Format of SM2 ciphertext is a point (2*point_len+1) plus
     * the masked ciphertext (out_len) plus a hash.
     */
    ctext_len = (2 * point_len + 1) + in_len + hash_alg_len;
    if (ctext_len > PGP_MPINT_SIZE) {
        RNP_LOG("too large output for SM2 encryption");
        goto done;
    }

    if (!sm2_load_public_key(&sm2_key, key)) {
        RNP_LOG("Failed to load public key");
        goto done;
    }

    /*
    SM2 encryption doesn't have any kind of format specifier because
    it's an all in one scheme, only the hash (used for the integrity
    check) is specified.
    */
    if (botan_pk_op_encrypt_create(&enc_op, sm2_key, rnp::Hash::name_backend(hash_algo), 0)) {
        goto done;
    }

    out->m.len = sizeof(out->m.mpi);
    if (botan_pk_op_encrypt(enc_op, rng->handle(), out->m.mpi, &out->m.len, in, in_len) == 0) {
        out->m.mpi[out->m.len++] = hash_algo;
        ret = RNP_SUCCESS;
    }
done:
    botan_pk_op_encrypt_destroy(enc_op);
    botan_pubkey_destroy(sm2_key);
    return ret;
}

rnp_result_t
sm2_decrypt(uint8_t *                  out,
            size_t *                   out_len,
            const pgp_sm2_encrypted_t *in,
            const pgp_ec_key_t *       key)
{
    const ec_curve_desc_t *curve;
    botan_pk_op_decrypt_t  decrypt_op = NULL;
    botan_privkey_t        b_key = NULL;
    size_t                 in_len;
    rnp_result_t           ret = RNP_ERROR_GENERIC;
    uint8_t                hash_id;
    const char *           hash_name = NULL;

    curve = get_curve_desc(key->curve);
    in_len = mpi_bytes(&in->m);
    if (curve == NULL || in_len < 64) {
        goto done;
    }

    if (!sm2_load_secret_key(&b_key, key)) {
        RNP_LOG("Can't load private key");
        goto done;
    }

    hash_id = in->m.mpi[in_len - 1];
    hash_name = rnp::Hash::name_backend((pgp_hash_alg_t) hash_id);
    if (!hash_name) {
        RNP_LOG("Unknown hash used in SM2 ciphertext");
        goto done;
    }

    if (botan_pk_op_decrypt_create(&decrypt_op, b_key, hash_name, 0) != 0) {
        goto done;
    }

    if (botan_pk_op_decrypt(decrypt_op, out, out_len, in->m.mpi, in_len - 1) == 0) {
        ret = RNP_SUCCESS;
    }
done:
    botan_privkey_destroy(b_key);
    botan_pk_op_decrypt_destroy(decrypt_op);
    return ret;
}