library/x509write_csr.c

/*
 *  X.509 Certificate Signing Request writing
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
/*
 * References:
 * - CSRs: PKCS#10 v1.7 aka RFC 2986
 * - attributes: PKCS#9 v2.0 aka RFC 2985
 */

#include "common.h"

#if defined(MBEDTLS_X509_CSR_WRITE_C)

#    include "mbedtls/x509_csr.h"
#    include "mbedtls/asn1write.h"
#    include "mbedtls/error.h"
#    include "mbedtls/oid.h"
#    include "mbedtls/platform_util.h"

#    if defined(MBEDTLS_USE_PSA_CRYPTO)
#        include "psa/crypto.h"
#        include "mbedtls/psa_util.h"
#    endif

#    include <string.h>
#    include <stdlib.h>

#    if defined(MBEDTLS_PEM_WRITE_C)
#        include "mbedtls/pem.h"
#    endif

#    if defined(MBEDTLS_PLATFORM_C)
#        include "mbedtls/platform.h"
#    else
#        include <stdlib.h>
#        define mbedtls_calloc calloc
#        define mbedtls_free   free
#    endif

void mbedtls_x509write_csr_init(mbedtls_x509write_csr *ctx)
{
    memset(ctx, 0, sizeof(mbedtls_x509write_csr));
}

void mbedtls_x509write_csr_free(mbedtls_x509write_csr *ctx)
{
    mbedtls_asn1_free_named_data_list(&ctx->subject);
    mbedtls_asn1_free_named_data_list(&ctx->extensions);

    mbedtls_platform_zeroize(ctx, sizeof(mbedtls_x509write_csr));
}

void mbedtls_x509write_csr_set_md_alg(mbedtls_x509write_csr *ctx,
                                      mbedtls_md_type_t md_alg)
{
    ctx->md_alg = md_alg;
}

void mbedtls_x509write_csr_set_key(mbedtls_x509write_csr *ctx,
                                   mbedtls_pk_context *key)
{
    ctx->key = key;
}

int mbedtls_x509write_csr_set_subject_name(mbedtls_x509write_csr *ctx,
                                           const char *subject_name)
{
    return mbedtls_x509_string_to_names(&ctx->subject, subject_name);
}

int mbedtls_x509write_csr_set_extension(mbedtls_x509write_csr *ctx,
                                        const char *oid,
                                        size_t oid_len,
                                        int critical,
                                        const unsigned char *val,
                                        size_t val_len)
{
    return mbedtls_x509_set_extension(&ctx->extensions, oid, oid_len, critical,
                                      val, val_len);
}

int mbedtls_x509write_csr_set_key_usage(mbedtls_x509write_csr *ctx,
                                        unsigned char key_usage)
{
    unsigned char buf[4] = { 0 };
    unsigned char *c;
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    c = buf + 4;

    ret = mbedtls_asn1_write_named_bitstring(&c, buf, &key_usage, 8);
    if (ret < 3 || ret > 4)
        return ret;

    ret = mbedtls_x509write_csr_set_extension(
        ctx, MBEDTLS_OID_KEY_USAGE, MBEDTLS_OID_SIZE(MBEDTLS_OID_KEY_USAGE), 0,
        c, (size_t)ret);
    if (ret != 0)
        return ret;

    return 0;
}

int mbedtls_x509write_csr_set_ns_cert_type(mbedtls_x509write_csr *ctx,
                                           unsigned char ns_cert_type)
{
    unsigned char buf[4] = { 0 };
    unsigned char *c;
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    c = buf + 4;

    ret = mbedtls_asn1_write_named_bitstring(&c, buf, &ns_cert_type, 8);
    if (ret < 3 || ret > 4)
        return ret;

    ret = mbedtls_x509write_csr_set_extension(
        ctx, MBEDTLS_OID_NS_CERT_TYPE,
        MBEDTLS_OID_SIZE(MBEDTLS_OID_NS_CERT_TYPE), 0, c, (size_t)ret);
    if (ret != 0)
        return ret;

    return 0;
}

static int
x509write_csr_der_internal(mbedtls_x509write_csr *ctx,
                           unsigned char *buf,
                           size_t size,
                           unsigned char *sig,
                           size_t sig_size,
                           int (*f_rng)(void *, unsigned char *, size_t),
                           void *p_rng)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    const char *sig_oid;
    size_t sig_oid_len = 0;
    unsigned char *c, *c2;
    unsigned char hash[64];
    size_t pub_len = 0, sig_and_oid_len = 0, sig_len;
    size_t len = 0;
    mbedtls_pk_type_t pk_alg;
#    if defined(MBEDTLS_USE_PSA_CRYPTO)
    psa_hash_operation_t hash_operation = PSA_HASH_OPERATION_INIT;
    size_t hash_len;
    psa_algorithm_t hash_alg = mbedtls_psa_translate_md(ctx->md_alg);
#    endif /* MBEDTLS_USE_PSA_CRYPTO */

    /* Write the CSR backwards starting from the end of buf */
    c = buf + size;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_extensions(&c, buf,
                                                            ctx->extensions));

    if (len) {
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len,
                             mbedtls_asn1_write_tag(&c, buf,
                                                    MBEDTLS_ASN1_CONSTRUCTED |
                                                        MBEDTLS_ASN1_SEQUENCE));

        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(
            len, mbedtls_asn1_write_tag(
                     &c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET));

        MBEDTLS_ASN1_CHK_ADD(
            len, mbedtls_asn1_write_oid(
                     &c, buf, MBEDTLS_OID_PKCS9_CSR_EXT_REQ,
                     MBEDTLS_OID_SIZE(MBEDTLS_OID_PKCS9_CSR_EXT_REQ)));

        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len,
                             mbedtls_asn1_write_tag(&c, buf,
                                                    MBEDTLS_ASN1_CONSTRUCTED |
                                                        MBEDTLS_ASN1_SEQUENCE));
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(
        len, mbedtls_asn1_write_tag(&c, buf,
                                    MBEDTLS_ASN1_CONSTRUCTED |
                                        MBEDTLS_ASN1_CONTEXT_SPECIFIC));

    MBEDTLS_ASN1_CHK_ADD(pub_len,
                         mbedtls_pk_write_pubkey_der(ctx->key, buf, c - buf));
    c -= pub_len;
    len += pub_len;

    /*
     *  Subject  ::=  Name
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf, ctx->subject));

    /*
     *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(&c, buf, 0));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(
        len, mbedtls_asn1_write_tag(
                 &c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    /*
     * Sign the written CSR data into the sig buffer
     * Note: hash errors can happen only after an internal error
     */
#    if defined(MBEDTLS_USE_PSA_CRYPTO)
    if (psa_hash_setup(&hash_operation, hash_alg) != PSA_SUCCESS)
        return MBEDTLS_ERR_X509_FATAL_ERROR;

    if (psa_hash_update(&hash_operation, c, len) != PSA_SUCCESS)
        return MBEDTLS_ERR_X509_FATAL_ERROR;

    if (psa_hash_finish(&hash_operation, hash, sizeof(hash), &hash_len) !=
        PSA_SUCCESS) {
        return MBEDTLS_ERR_X509_FATAL_ERROR;
    }
#    else /* MBEDTLS_USE_PSA_CRYPTO */
    ret = mbedtls_md(mbedtls_md_info_from_type(ctx->md_alg), c, len, hash);
    if (ret != 0)
        return ret;
#    endif
    if ((ret = mbedtls_pk_sign(ctx->key, ctx->md_alg, hash, 0, sig, sig_size,
                               &sig_len, f_rng, p_rng)) != 0) {
        return ret;
    }

    if (mbedtls_pk_can_do(ctx->key, MBEDTLS_PK_RSA))
        pk_alg = MBEDTLS_PK_RSA;
    else if (mbedtls_pk_can_do(ctx->key, MBEDTLS_PK_ECDSA))
        pk_alg = MBEDTLS_PK_ECDSA;
    else
        return MBEDTLS_ERR_X509_INVALID_ALG;

    if ((ret = mbedtls_oid_get_oid_by_sig_alg(pk_alg, ctx->md_alg, &sig_oid,
                                              &sig_oid_len)) != 0) {
        return ret;
    }

    /*
     * Move the written CSR data to the start of buf to create space for
     * writing the signature into buf.
     */
    memmove(buf, c, len);

    /*
     * Write sig and its OID into buf backwards from the end of buf.
     * Note: mbedtls_x509_write_sig will check for c2 - ( buf + len ) < sig_len
     * and return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if needed.
     */
    c2 = buf + size;
    MBEDTLS_ASN1_CHK_ADD(sig_and_oid_len,
                         mbedtls_x509_write_sig(&c2, buf + len, sig_oid,
                                                sig_oid_len, sig, sig_len));

    /*
     * Compact the space between the CSR data and signature by moving the
     * CSR data to the start of the signature.
     */
    c2 -= len;
    memmove(c2, buf, len);

    /* ASN encode the total size and tag the CSR data with it. */
    len += sig_and_oid_len;
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c2, buf, len));
    MBEDTLS_ASN1_CHK_ADD(
        len, mbedtls_asn1_write_tag(
                 &c2, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    /* Zero the unused bytes at the start of buf */
    memset(buf, 0, c2 - buf);

    return (int)len;
}

int mbedtls_x509write_csr_der(mbedtls_x509write_csr *ctx,
                              unsigned char *buf,
                              size_t size,
                              int (*f_rng)(void *, unsigned char *, size_t),
                              void *p_rng)
{
    int ret;
    unsigned char *sig;

    if ((sig = mbedtls_calloc(1, MBEDTLS_PK_SIGNATURE_MAX_SIZE)) == NULL) {
        return MBEDTLS_ERR_X509_ALLOC_FAILED;
    }

    ret = x509write_csr_der_internal(
        ctx, buf, size, sig, MBEDTLS_PK_SIGNATURE_MAX_SIZE, f_rng, p_rng);

    mbedtls_free(sig);

    return ret;
}

#    define PEM_BEGIN_CSR "-----BEGIN CERTIFICATE REQUEST-----\n"
#    define PEM_END_CSR   "-----END CERTIFICATE REQUEST-----\n"

#    if defined(MBEDTLS_PEM_WRITE_C)
int mbedtls_x509write_csr_pem(mbedtls_x509write_csr *ctx,
                              unsigned char *buf,
                              size_t size,
                              int (*f_rng)(void *, unsigned char *, size_t),
                              void *p_rng)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t olen = 0;

    if ((ret = mbedtls_x509write_csr_der(ctx, buf, size, f_rng, p_rng)) < 0) {
        return ret;
    }

    if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_CSR, PEM_END_CSR,
                                        buf + size - ret, ret, buf, size,
                                        &olen)) != 0) {
        return ret;
    }

    return 0;
}
#    endif /* MBEDTLS_PEM_WRITE_C */

#endif /* MBEDTLS_X509_CSR_WRITE_C */