programs/x509/cert_write.c

/*
 *  Certificate generation and signing
 *
 *  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.
 */

#include "mbedtls/build_info.h"

#if defined(MBEDTLS_PLATFORM_C)
#    include "mbedtls/platform.h"
#else
#    include <stdio.h>
#    include <stdlib.h>
#    define mbedtls_printf       printf
#    define mbedtls_exit         exit
#    define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
#    define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
#endif /* MBEDTLS_PLATFORM_C */

#if !defined(MBEDTLS_X509_CRT_WRITE_C) ||                            \
    !defined(MBEDTLS_X509_CRT_PARSE_C) || !defined(MBEDTLS_FS_IO) || \
    !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C) ||   \
    !defined(MBEDTLS_ERROR_C) || !defined(MBEDTLS_SHA256_C) ||       \
    !defined(MBEDTLS_PEM_WRITE_C)
int main(void)
{
    mbedtls_printf(
        "MBEDTLS_X509_CRT_WRITE_C and/or MBEDTLS_X509_CRT_PARSE_C and/or "
        "MBEDTLS_FS_IO and/or MBEDTLS_SHA256_C and/or "
        "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C and/or "
        "MBEDTLS_ERROR_C not defined.\n");
    mbedtls_exit(0);
}
#else

#    include "mbedtls/x509_crt.h"
#    include "mbedtls/x509_csr.h"
#    include "mbedtls/entropy.h"
#    include "mbedtls/ctr_drbg.h"
#    include "mbedtls/md.h"
#    include "mbedtls/error.h"

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

#    if defined(MBEDTLS_X509_CSR_PARSE_C)
#        define USAGE_CSR                                                              \
            "    request_file=%%s         default: (empty)\n"                          \
            "                            If request_file is specified, subject_key,\n" \
            "                            subject_pwd and subject_name are ignored!\n"
#    else
#        define USAGE_CSR ""
#    endif /* MBEDTLS_X509_CSR_PARSE_C */

#    define DFL_ISSUER_CRT      ""
#    define DFL_REQUEST_FILE    ""
#    define DFL_SUBJECT_KEY     "subject.key"
#    define DFL_ISSUER_KEY      "ca.key"
#    define DFL_SUBJECT_PWD     ""
#    define DFL_ISSUER_PWD      ""
#    define DFL_OUTPUT_FILENAME "cert.crt"
#    define DFL_SUBJECT_NAME    "CN=Cert,O=mbed TLS,C=UK"
#    define DFL_ISSUER_NAME     "CN=CA,O=mbed TLS,C=UK"
#    define DFL_NOT_BEFORE      "20010101000000"
#    define DFL_NOT_AFTER       "20301231235959"
#    define DFL_SERIAL          "1"
#    define DFL_SELFSIGN        0
#    define DFL_IS_CA           0
#    define DFL_MAX_PATHLEN     -1
#    define DFL_KEY_USAGE       0
#    define DFL_NS_CERT_TYPE    0
#    define DFL_VERSION         3
#    define DFL_AUTH_IDENT      1
#    define DFL_SUBJ_IDENT      1
#    define DFL_CONSTRAINTS     1
#    define DFL_DIGEST          MBEDTLS_MD_SHA256

#    define USAGE                                                                  \
        "\n usage: cert_write param=<>...\n"                                       \
        "\n acceptable parameters:\n" USAGE_CSR                                    \
        "    subject_key=%%s          default: subject.key\n"                      \
        "    subject_pwd=%%s          default: (empty)\n"                          \
        "    subject_name=%%s         default: CN=Cert,O=mbed TLS,C=UK\n"          \
        "\n"                                                                       \
        "    issuer_crt=%%s           default: (empty)\n"                          \
        "                            If issuer_crt is specified, issuer_name is\n" \
        "                            ignored!\n"                                   \
        "    issuer_name=%%s          default: CN=CA,O=mbed TLS,C=UK\n"            \
        "\n"                                                                       \
        "    selfsign=%%d             default: 0 (false)\n"                        \
        "                            If selfsign is enabled, issuer_name and\n"    \
        "                            issuer_key are required (issuer_crt and\n"    \
        "                            subject_* are ignored\n"                      \
        "    issuer_key=%%s           default: ca.key\n"                           \
        "    issuer_pwd=%%s           default: (empty)\n"                          \
        "    output_file=%%s          default: cert.crt\n"                         \
        "    serial=%%s               default: 1\n"                                \
        "    not_before=%%s           default: 20010101000000\n"                   \
        "    not_after=%%s            default: 20301231235959\n"                   \
        "    is_ca=%%d                default: 0 (disabled)\n"                     \
        "    max_pathlen=%%d          default: -1 (none)\n"                        \
        "    md=%%s                   default: SHA256\n"                           \
        "                            Supported values (if enabled):\n"             \
        "                            MD5, RIPEMD160, SHA1,\n"                      \
        "                            SHA224, SHA256, SHA384, SHA512\n"             \
        "    version=%%d              default: 3\n"                                \
        "                            Possible values: 1, 2, 3\n"                   \
        "    subject_identifier=%%s   default: 1\n"                                \
        "                            Possible values: 0, 1\n"                      \
        "                            (Considered for v3 only)\n"                   \
        "    authority_identifier=%%s default: 1\n"                                \
        "                            Possible values: 0, 1\n"                      \
        "                            (Considered for v3 only)\n"                   \
        "    basic_constraints=%%d    default: 1\n"                                \
        "                            Possible values: 0, 1\n"                      \
        "                            (Considered for v3 only)\n"                   \
        "    key_usage=%%s            default: (empty)\n"                          \
        "                            Comma-separated-list of values:\n"            \
        "                            digital_signature\n"                          \
        "                            non_repudiation\n"                            \
        "                            key_encipherment\n"                           \
        "                            data_encipherment\n"                          \
        "                            key_agreement\n"                              \
        "                            key_cert_sign\n"                              \
        "                            crl_sign\n"                                   \
        "                            (Considered for v3 only)\n"                   \
        "    ns_cert_type=%%s         default: (empty)\n"                          \
        "                            Comma-separated-list of values:\n"            \
        "                            ssl_client\n"                                 \
        "                            ssl_server\n"                                 \
        "                            email\n"                                      \
        "                            object_signing\n"                             \
        "                            ssl_ca\n"                                     \
        "                            email_ca\n"                                   \
        "                            object_signing_ca\n"                          \
        "\n"

/*
 * global options
 */
struct options {
    const char *issuer_crt; /* filename of the issuer certificate   */
    const char *request_file; /* filename of the certificate request  */
    const char *subject_key; /* filename of the subject key file     */
    const char *issuer_key; /* filename of the issuer key file      */
    const char *subject_pwd; /* password for the subject key file    */
    const char *issuer_pwd; /* password for the issuer key file     */
    const char *output_file; /* where to store the constructed CRT   */
    const char *subject_name; /* subject name for certificate         */
    const char *issuer_name; /* issuer name for certificate          */
    const char *not_before; /* validity period not before           */
    const char *not_after; /* validity period not after            */
    const char *serial; /* serial number string                 */
    int selfsign; /* selfsign the certificate             */
    int is_ca; /* is a CA certificate                  */
    int max_pathlen; /* maximum CA path length               */
    int authority_identifier; /* add authority identifier to CRT      */
    int subject_identifier; /* add subject identifier to CRT        */
    int basic_constraints; /* add basic constraints ext to CRT     */
    int version; /* CRT version                          */
    mbedtls_md_type_t md; /* Hash used for signing                */
    unsigned char key_usage; /* key usage flags                      */
    unsigned char ns_cert_type; /* NS cert type                         */
} opt;

int write_certificate(mbedtls_x509write_cert *crt,
                      const char *output_file,
                      int (*f_rng)(void *, unsigned char *, size_t),
                      void *p_rng)
{
    int ret;
    FILE *f;
    unsigned char output_buf[4096];
    size_t len = 0;

    memset(output_buf, 0, 4096);
    if ((ret = mbedtls_x509write_crt_pem(crt, output_buf, 4096, f_rng, p_rng)) <
        0)
        return ret;

    len = strlen((char *)output_buf);

    if ((f = fopen(output_file, "w")) == NULL)
        return -1;

    if (fwrite(output_buf, 1, len, f) != len) {
        fclose(f);
        return -1;
    }

    fclose(f);

    return 0;
}

int main(int argc, char *argv[])
{
    int ret = 1;
    int exit_code = MBEDTLS_EXIT_FAILURE;
    mbedtls_x509_crt issuer_crt;
    mbedtls_pk_context loaded_issuer_key, loaded_subject_key;
    mbedtls_pk_context *issuer_key = &loaded_issuer_key,
                       *subject_key = &loaded_subject_key;
    char buf[1024];
    char issuer_name[256];
    int i;
    char *p, *q, *r;
#    if defined(MBEDTLS_X509_CSR_PARSE_C)
    char subject_name[256];
    mbedtls_x509_csr csr;
#    endif
    mbedtls_x509write_cert crt;
    mbedtls_mpi serial;
    mbedtls_entropy_context entropy;
    mbedtls_ctr_drbg_context ctr_drbg;
    const char *pers = "crt example app";

    /*
     * Set to sane values
     */
    mbedtls_x509write_crt_init(&crt);
    mbedtls_pk_init(&loaded_issuer_key);
    mbedtls_pk_init(&loaded_subject_key);
    mbedtls_mpi_init(&serial);
    mbedtls_ctr_drbg_init(&ctr_drbg);
    mbedtls_entropy_init(&entropy);
#    if defined(MBEDTLS_X509_CSR_PARSE_C)
    mbedtls_x509_csr_init(&csr);
#    endif
    mbedtls_x509_crt_init(&issuer_crt);
    memset(buf, 0, 1024);

    if (argc == 0) {
usage:
        mbedtls_printf(USAGE);
        goto exit;
    }

    opt.issuer_crt = DFL_ISSUER_CRT;
    opt.request_file = DFL_REQUEST_FILE;
    opt.subject_key = DFL_SUBJECT_KEY;
    opt.issuer_key = DFL_ISSUER_KEY;
    opt.subject_pwd = DFL_SUBJECT_PWD;
    opt.issuer_pwd = DFL_ISSUER_PWD;
    opt.output_file = DFL_OUTPUT_FILENAME;
    opt.subject_name = DFL_SUBJECT_NAME;
    opt.issuer_name = DFL_ISSUER_NAME;
    opt.not_before = DFL_NOT_BEFORE;
    opt.not_after = DFL_NOT_AFTER;
    opt.serial = DFL_SERIAL;
    opt.selfsign = DFL_SELFSIGN;
    opt.is_ca = DFL_IS_CA;
    opt.max_pathlen = DFL_MAX_PATHLEN;
    opt.key_usage = DFL_KEY_USAGE;
    opt.ns_cert_type = DFL_NS_CERT_TYPE;
    opt.version = DFL_VERSION - 1;
    opt.md = DFL_DIGEST;
    opt.subject_identifier = DFL_SUBJ_IDENT;
    opt.authority_identifier = DFL_AUTH_IDENT;
    opt.basic_constraints = DFL_CONSTRAINTS;

    for (i = 1; i < argc; i++) {
        p = argv[i];
        if ((q = strchr(p, '=')) == NULL)
            goto usage;
        *q++ = '\0';

        if (strcmp(p, "request_file") == 0)
            opt.request_file = q;
        else if (strcmp(p, "subject_key") == 0)
            opt.subject_key = q;
        else if (strcmp(p, "issuer_key") == 0)
            opt.issuer_key = q;
        else if (strcmp(p, "subject_pwd") == 0)
            opt.subject_pwd = q;
        else if (strcmp(p, "issuer_pwd") == 0)
            opt.issuer_pwd = q;
        else if (strcmp(p, "issuer_crt") == 0)
            opt.issuer_crt = q;
        else if (strcmp(p, "output_file") == 0)
            opt.output_file = q;
        else if (strcmp(p, "subject_name") == 0) {
            opt.subject_name = q;
        } else if (strcmp(p, "issuer_name") == 0) {
            opt.issuer_name = q;
        } else if (strcmp(p, "not_before") == 0) {
            opt.not_before = q;
        } else if (strcmp(p, "not_after") == 0) {
            opt.not_after = q;
        } else if (strcmp(p, "serial") == 0) {
            opt.serial = q;
        } else if (strcmp(p, "authority_identifier") == 0) {
            opt.authority_identifier = atoi(q);
            if (opt.authority_identifier != 0 &&
                opt.authority_identifier != 1) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
        } else if (strcmp(p, "subject_identifier") == 0) {
            opt.subject_identifier = atoi(q);
            if (opt.subject_identifier != 0 && opt.subject_identifier != 1) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
        } else if (strcmp(p, "basic_constraints") == 0) {
            opt.basic_constraints = atoi(q);
            if (opt.basic_constraints != 0 && opt.basic_constraints != 1) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
        } else if (strcmp(p, "md") == 0) {
            const mbedtls_md_info_t *md_info = mbedtls_md_info_from_string(q);
            if (md_info == NULL) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
            opt.md = mbedtls_md_get_type(md_info);
        } else if (strcmp(p, "version") == 0) {
            opt.version = atoi(q);
            if (opt.version < 1 || opt.version > 3) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
            opt.version--;
        } else if (strcmp(p, "selfsign") == 0) {
            opt.selfsign = atoi(q);
            if (opt.selfsign < 0 || opt.selfsign > 1) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
        } else if (strcmp(p, "is_ca") == 0) {
            opt.is_ca = atoi(q);
            if (opt.is_ca < 0 || opt.is_ca > 1) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
        } else if (strcmp(p, "max_pathlen") == 0) {
            opt.max_pathlen = atoi(q);
            if (opt.max_pathlen < -1 || opt.max_pathlen > 127) {
                mbedtls_printf("Invalid argument for option %s\n", p);
                goto usage;
            }
        } else if (strcmp(p, "key_usage") == 0) {
            while (q != NULL) {
                if ((r = strchr(q, ',')) != NULL)
                    *r++ = '\0';

                if (strcmp(q, "digital_signature") == 0)
                    opt.key_usage |= MBEDTLS_X509_KU_DIGITAL_SIGNATURE;
                else if (strcmp(q, "non_repudiation") == 0)
                    opt.key_usage |= MBEDTLS_X509_KU_NON_REPUDIATION;
                else if (strcmp(q, "key_encipherment") == 0)
                    opt.key_usage |= MBEDTLS_X509_KU_KEY_ENCIPHERMENT;
                else if (strcmp(q, "data_encipherment") == 0)
                    opt.key_usage |= MBEDTLS_X509_KU_DATA_ENCIPHERMENT;
                else if (strcmp(q, "key_agreement") == 0)
                    opt.key_usage |= MBEDTLS_X509_KU_KEY_AGREEMENT;
                else if (strcmp(q, "key_cert_sign") == 0)
                    opt.key_usage |= MBEDTLS_X509_KU_KEY_CERT_SIGN;
                else if (strcmp(q, "crl_sign") == 0)
                    opt.key_usage |= MBEDTLS_X509_KU_CRL_SIGN;
                else {
                    mbedtls_printf("Invalid argument for option %s\n", p);
                    goto usage;
                }

                q = r;
            }
        } else if (strcmp(p, "ns_cert_type") == 0) {
            while (q != NULL) {
                if ((r = strchr(q, ',')) != NULL)
                    *r++ = '\0';

                if (strcmp(q, "ssl_client") == 0)
                    opt.ns_cert_type |= MBEDTLS_X509_NS_CERT_TYPE_SSL_CLIENT;
                else if (strcmp(q, "ssl_server") == 0)
                    opt.ns_cert_type |= MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER;
                else if (strcmp(q, "email") == 0)
                    opt.ns_cert_type |= MBEDTLS_X509_NS_CERT_TYPE_EMAIL;
                else if (strcmp(q, "object_signing") == 0)
                    opt.ns_cert_type |=
                        MBEDTLS_X509_NS_CERT_TYPE_OBJECT_SIGNING;
                else if (strcmp(q, "ssl_ca") == 0)
                    opt.ns_cert_type |= MBEDTLS_X509_NS_CERT_TYPE_SSL_CA;
                else if (strcmp(q, "email_ca") == 0)
                    opt.ns_cert_type |= MBEDTLS_X509_NS_CERT_TYPE_EMAIL_CA;
                else if (strcmp(q, "object_signing_ca") == 0)
                    opt.ns_cert_type |=
                        MBEDTLS_X509_NS_CERT_TYPE_OBJECT_SIGNING_CA;
                else {
                    mbedtls_printf("Invalid argument for option %s\n", p);
                    goto usage;
                }

                q = r;
            }
        } else
            goto usage;
    }

    mbedtls_printf("\n");

    /*
     * 0. Seed the PRNG
     */
    mbedtls_printf("  . Seeding the random number generator...");
    fflush(stdout);

    if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
                                     (const unsigned char *)pers,
                                     strlen(pers))) != 0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  mbedtls_ctr_drbg_seed returned %d - %s\n",
                       ret, buf);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    // Parse serial to MPI
    //
    mbedtls_printf("  . Reading serial number...");
    fflush(stdout);

    if ((ret = mbedtls_mpi_read_string(&serial, 10, opt.serial)) != 0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  mbedtls_mpi_read_string "
                       "returned -0x%04x - %s\n\n",
                       (unsigned int)-ret, buf);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    // Parse issuer certificate if present
    //
    if (!opt.selfsign && strlen(opt.issuer_crt)) {
        /*
         * 1.0.a. Load the certificates
         */
        mbedtls_printf("  . Loading the issuer certificate ...");
        fflush(stdout);

        if ((ret = mbedtls_x509_crt_parse_file(&issuer_crt, opt.issuer_crt)) !=
            0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_x509_crt_parse_file "
                           "returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        ret = mbedtls_x509_dn_gets(issuer_name, sizeof(issuer_name),
                                   &issuer_crt.MBEDTLS_PRIVATE(subject));
        if (ret < 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_x509_dn_gets "
                           "returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        opt.issuer_name = issuer_name;

        mbedtls_printf(" ok\n");
    }

#    if defined(MBEDTLS_X509_CSR_PARSE_C)
    // Parse certificate request if present
    //
    if (!opt.selfsign && strlen(opt.request_file)) {
        /*
         * 1.0.b. Load the CSR
         */
        mbedtls_printf("  . Loading the certificate request ...");
        fflush(stdout);

        if ((ret = mbedtls_x509_csr_parse_file(&csr, opt.request_file)) != 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_x509_csr_parse_file "
                           "returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        ret = mbedtls_x509_dn_gets(subject_name, sizeof(subject_name),
                                   &csr.MBEDTLS_PRIVATE(subject));
        if (ret < 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_x509_dn_gets "
                           "returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        opt.subject_name = subject_name;
        subject_key = &csr.MBEDTLS_PRIVATE(pk);

        mbedtls_printf(" ok\n");
    }
#    endif /* MBEDTLS_X509_CSR_PARSE_C */

    /*
     * 1.1. Load the keys
     */
    if (!opt.selfsign && !strlen(opt.request_file)) {
        mbedtls_printf("  . Loading the subject key ...");
        fflush(stdout);

        ret = mbedtls_pk_parse_keyfile(&loaded_subject_key, opt.subject_key,
                                       opt.subject_pwd, mbedtls_ctr_drbg_random,
                                       &ctr_drbg);
        if (ret != 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_pk_parse_keyfile "
                           "returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        mbedtls_printf(" ok\n");
    }

    mbedtls_printf("  . Loading the issuer key ...");
    fflush(stdout);

    ret = mbedtls_pk_parse_keyfile(&loaded_issuer_key, opt.issuer_key,
                                   opt.issuer_pwd, mbedtls_ctr_drbg_random,
                                   &ctr_drbg);
    if (ret != 0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  mbedtls_pk_parse_keyfile "
                       "returned -x%02x - %s\n\n",
                       (unsigned int)-ret, buf);
        goto exit;
    }

    // Check if key and issuer certificate match
    //
    if (strlen(opt.issuer_crt)) {
        if (mbedtls_pk_check_pair(&issuer_crt.MBEDTLS_PRIVATE(pk), issuer_key,
                                  mbedtls_ctr_drbg_random, &ctr_drbg) != 0) {
            mbedtls_printf(" failed\n  !  issuer_key does not match "
                           "issuer certificate\n\n");
            goto exit;
        }
    }

    mbedtls_printf(" ok\n");

    if (opt.selfsign) {
        opt.subject_name = opt.issuer_name;
        subject_key = issuer_key;
    }

    mbedtls_x509write_crt_set_subject_key(&crt, subject_key);
    mbedtls_x509write_crt_set_issuer_key(&crt, issuer_key);

    /*
     * 1.0. Check the names for validity
     */
    if ((ret = mbedtls_x509write_crt_set_subject_name(&crt,
                                                      opt.subject_name)) != 0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  mbedtls_x509write_crt_set_subject_name "
                       "returned -0x%04x - %s\n\n",
                       (unsigned int)-ret, buf);
        goto exit;
    }

    if ((ret = mbedtls_x509write_crt_set_issuer_name(&crt, opt.issuer_name)) !=
        0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  mbedtls_x509write_crt_set_issuer_name "
                       "returned -0x%04x - %s\n\n",
                       (unsigned int)-ret, buf);
        goto exit;
    }

    mbedtls_printf("  . Setting certificate values ...");
    fflush(stdout);

    mbedtls_x509write_crt_set_version(&crt, opt.version);
    mbedtls_x509write_crt_set_md_alg(&crt, opt.md);

    ret = mbedtls_x509write_crt_set_serial(&crt, &serial);
    if (ret != 0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  mbedtls_x509write_crt_set_serial "
                       "returned -0x%04x - %s\n\n",
                       (unsigned int)-ret, buf);
        goto exit;
    }

    ret =
        mbedtls_x509write_crt_set_validity(&crt, opt.not_before, opt.not_after);
    if (ret != 0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  mbedtls_x509write_crt_set_validity "
                       "returned -0x%04x - %s\n\n",
                       (unsigned int)-ret, buf);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    if (opt.version == MBEDTLS_X509_CRT_VERSION_3 &&
        opt.basic_constraints != 0) {
        mbedtls_printf("  . Adding the Basic Constraints extension ...");
        fflush(stdout);

        ret = mbedtls_x509write_crt_set_basic_constraints(&crt, opt.is_ca,
                                                          opt.max_pathlen);
        if (ret != 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  x509write_crt_set_basic_contraints "
                           "returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        mbedtls_printf(" ok\n");
    }

#    if defined(MBEDTLS_SHA1_C)
    if (opt.version == MBEDTLS_X509_CRT_VERSION_3 &&
        opt.subject_identifier != 0) {
        mbedtls_printf("  . Adding the Subject Key Identifier ...");
        fflush(stdout);

        ret = mbedtls_x509write_crt_set_subject_key_identifier(&crt);
        if (ret != 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_x509write_crt_set_subject"
                           "_key_identifier returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        mbedtls_printf(" ok\n");
    }

    if (opt.version == MBEDTLS_X509_CRT_VERSION_3 &&
        opt.authority_identifier != 0) {
        mbedtls_printf("  . Adding the Authority Key Identifier ...");
        fflush(stdout);

        ret = mbedtls_x509write_crt_set_authority_key_identifier(&crt);
        if (ret != 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_x509write_crt_set_authority_"
                           "key_identifier returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        mbedtls_printf(" ok\n");
    }
#    endif /* MBEDTLS_SHA1_C */

    if (opt.version == MBEDTLS_X509_CRT_VERSION_3 && opt.key_usage != 0) {
        mbedtls_printf("  . Adding the Key Usage extension ...");
        fflush(stdout);

        ret = mbedtls_x509write_crt_set_key_usage(&crt, opt.key_usage);
        if (ret != 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(" failed\n  !  mbedtls_x509write_crt_set_key_usage "
                           "returned -0x%04x - %s\n\n",
                           (unsigned int)-ret, buf);
            goto exit;
        }

        mbedtls_printf(" ok\n");
    }

    if (opt.version == MBEDTLS_X509_CRT_VERSION_3 && opt.ns_cert_type != 0) {
        mbedtls_printf("  . Adding the NS Cert Type extension ...");
        fflush(stdout);

        ret = mbedtls_x509write_crt_set_ns_cert_type(&crt, opt.ns_cert_type);
        if (ret != 0) {
            mbedtls_strerror(ret, buf, 1024);
            mbedtls_printf(
                " failed\n  !  mbedtls_x509write_crt_set_ns_cert_type "
                "returned -0x%04x - %s\n\n",
                (unsigned int)-ret, buf);
            goto exit;
        }

        mbedtls_printf(" ok\n");
    }

    /*
     * 1.2. Writing the certificate
     */
    mbedtls_printf("  . Writing the certificate...");
    fflush(stdout);

    if ((ret = write_certificate(&crt, opt.output_file, mbedtls_ctr_drbg_random,
                                 &ctr_drbg)) != 0) {
        mbedtls_strerror(ret, buf, 1024);
        mbedtls_printf(" failed\n  !  write_certificate -0x%04x - %s\n\n",
                       (unsigned int)-ret, buf);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    exit_code = MBEDTLS_EXIT_SUCCESS;

exit:
#    if defined(MBEDTLS_X509_CSR_PARSE_C)
    mbedtls_x509_csr_free(&csr);
#    endif /* MBEDTLS_X509_CSR_PARSE_C */
    mbedtls_x509_crt_free(&issuer_crt);
    mbedtls_x509write_crt_free(&crt);
    mbedtls_pk_free(&loaded_subject_key);
    mbedtls_pk_free(&loaded_issuer_key);
    mbedtls_mpi_free(&serial);
    mbedtls_ctr_drbg_free(&ctr_drbg);
    mbedtls_entropy_free(&entropy);

#    if defined(_WIN32)
    mbedtls_printf("  + Press Enter to exit this program.\n");
    fflush(stdout);
    getchar();
#    endif

    mbedtls_exit(exit_code);
}
#endif /* MBEDTLS_X509_CRT_WRITE_C && MBEDTLS_X509_CRT_PARSE_C &&     \
          MBEDTLS_FS_IO && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C && \
          MBEDTLS_ERROR_C && MBEDTLS_PEM_WRITE_C */