cert_req.c

/*
 *  Certificate request generation
 *
 *  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"

#include "mbedtls/platform.h"

#if !defined(MBEDTLS_X509_CSR_WRITE_C) || !defined(MBEDTLS_FS_IO) ||  \
    !defined(MBEDTLS_PK_PARSE_C) || !defined(MBEDTLS_SHA256_C) || \
    !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C) || \
    !defined(MBEDTLS_PEM_WRITE_C)
int main(void)
{
    mbedtls_printf("MBEDTLS_X509_CSR_WRITE_C and/or MBEDTLS_FS_IO and/or "
                   "MBEDTLS_PK_PARSE_C and/or MBEDTLS_SHA256_C and/or "
                   "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C "
                   "not defined.\n");
    mbedtls_exit(0);
}
#else

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

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

#define DFL_FILENAME            "keyfile.key"
#define DFL_PASSWORD            NULL
#define DFL_DEBUG_LEVEL         0
#define DFL_OUTPUT_FILENAME     "cert.req"
#define DFL_SUBJECT_NAME        "CN=Cert,O=mbed TLS,C=UK"
#define DFL_KEY_USAGE           0
#define DFL_FORCE_KEY_USAGE     0
#define DFL_NS_CERT_TYPE        0
#define DFL_FORCE_NS_CERT_TYPE  0
#define DFL_MD_ALG              MBEDTLS_MD_SHA256

#define USAGE \
    "\n usage: cert_req param=<>...\n"                  \
    "\n acceptable parameters:\n"                       \
    "    filename=%%s         default: keyfile.key\n"   \
    "    password=%%s         default: NULL\n"          \
    "    debug_level=%%d      default: 0 (disabled)\n"  \
    "    output_file=%%s      default: cert.req\n"      \
    "    subject_name=%%s     default: CN=Cert,O=mbed TLS,C=UK\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"              \
    "    force_key_usage=0/1  default: off\n"           \
    "                          Add KeyUsage even if it is empty\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"     \
    "    force_ns_cert_type=0/1 default: off\n"         \
    "                          Add NsCertType even if it is empty\n"    \
    "    md=%%s               default: SHA256\n"       \
    "                          possible values:\n"     \
    "                          MD5, RIPEMD160, SHA1,\n" \
    "                          SHA224, SHA256, SHA384, SHA512\n" \
    "\n"


/*
 * global options
 */
struct options {
    const char *filename;       /* filename of the key file             */
    const char *password;       /* password for the key file            */
    int debug_level;            /* level of debugging                   */
    const char *output_file;    /* where to store the constructed key file  */
    const char *subject_name;   /* subject name for certificate request */
    unsigned char key_usage;    /* key usage flags                      */
    int force_key_usage;        /* Force adding the KeyUsage extension  */
    unsigned char ns_cert_type; /* NS cert type                         */
    int force_ns_cert_type;     /* Force adding NsCertType extension    */
    mbedtls_md_type_t md_alg;   /* Hash algorithm used for signature.   */
} opt;

int write_certificate_request(mbedtls_x509write_csr *req, 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_csr_pem(req, 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_pk_context key;
    char buf[1024];
    int i;
    char *p, *q, *r;
    mbedtls_x509write_csr req;
    mbedtls_entropy_context entropy;
    mbedtls_ctr_drbg_context ctr_drbg;
    const char *pers = "csr example app";

    /*
     * Set to sane values
     */
    mbedtls_x509write_csr_init(&req);
    mbedtls_pk_init(&key);
    mbedtls_ctr_drbg_init(&ctr_drbg);
    memset(buf, 0, sizeof(buf));

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

    opt.filename            = DFL_FILENAME;
    opt.password            = DFL_PASSWORD;
    opt.debug_level         = DFL_DEBUG_LEVEL;
    opt.output_file         = DFL_OUTPUT_FILENAME;
    opt.subject_name        = DFL_SUBJECT_NAME;
    opt.key_usage           = DFL_KEY_USAGE;
    opt.force_key_usage     = DFL_FORCE_KEY_USAGE;
    opt.ns_cert_type        = DFL_NS_CERT_TYPE;
    opt.force_ns_cert_type  = DFL_FORCE_NS_CERT_TYPE;
    opt.md_alg              = DFL_MD_ALG;

    for (i = 1; i < argc; i++) {

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

        if (strcmp(p, "filename") == 0) {
            opt.filename = q;
        } else if (strcmp(p, "password") == 0) {
            opt.password = q;
        } else if (strcmp(p, "output_file") == 0) {
            opt.output_file = q;
        } else if (strcmp(p, "debug_level") == 0) {
            opt.debug_level = atoi(q);
            if (opt.debug_level < 0 || opt.debug_level > 65535) {
                goto usage;
            }
        } else if (strcmp(p, "subject_name") == 0) {
            opt.subject_name = q;
        } 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_alg = mbedtls_md_get_type(md_info);
        } 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 {
                    goto usage;
                }

                q = r;
            }
        } else if (strcmp(p, "force_key_usage") == 0) {
            switch (atoi(q)) {
                case 0: opt.force_key_usage = 0; break;
                case 1: opt.force_key_usage = 1; break;
                default: goto usage;
            }
        } 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 {
                    goto usage;
                }

                q = r;
            }
        } else if (strcmp(p, "force_ns_cert_type") == 0) {
            switch (atoi(q)) {
                case 0: opt.force_ns_cert_type = 0; break;
                case 1: opt.force_ns_cert_type = 1; break;
                default: goto usage;
            }
        } else {
            goto usage;
        }
    }

    mbedtls_x509write_csr_set_md_alg(&req, opt.md_alg);

    if (opt.key_usage || opt.force_key_usage == 1) {
        mbedtls_x509write_csr_set_key_usage(&req, opt.key_usage);
    }

    if (opt.ns_cert_type || opt.force_ns_cert_type == 1) {
        mbedtls_x509write_csr_set_ns_cert_type(&req, opt.ns_cert_type);
    }

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

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

    mbedtls_printf(" ok\n");

    /*
     * 1.0. Check the subject name for validity
     */
    mbedtls_printf("  . Checking subject name...");
    fflush(stdout);

    if ((ret = mbedtls_x509write_csr_set_subject_name(&req, opt.subject_name)) != 0) {
        mbedtls_printf(" failed\n  !  mbedtls_x509write_csr_set_subject_name returned %d", ret);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    /*
     * 1.1. Load the key
     */
    mbedtls_printf("  . Loading the private key ...");
    fflush(stdout);

    ret = mbedtls_pk_parse_keyfile(&key, opt.filename, opt.password,
                                   mbedtls_ctr_drbg_random, &ctr_drbg);

    if (ret != 0) {
        mbedtls_printf(" failed\n  !  mbedtls_pk_parse_keyfile returned %d", ret);
        goto exit;
    }

    mbedtls_x509write_csr_set_key(&req, &key);

    mbedtls_printf(" ok\n");

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

    if ((ret = write_certificate_request(&req, opt.output_file,
                                         mbedtls_ctr_drbg_random, &ctr_drbg)) != 0) {
        mbedtls_printf(" failed\n  !  write_certificate_request %d", ret);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    exit_code = MBEDTLS_EXIT_SUCCESS;

exit:

    if (exit_code != MBEDTLS_EXIT_SUCCESS) {
#ifdef MBEDTLS_ERROR_C
        mbedtls_strerror(ret, buf, sizeof(buf));
        mbedtls_printf(" - %s\n", buf);
#else
        mbedtls_printf("\n");
#endif
    }

    mbedtls_x509write_csr_free(&req);
    mbedtls_pk_free(&key);
    mbedtls_ctr_drbg_free(&ctr_drbg);
    mbedtls_entropy_free(&entropy);

    mbedtls_exit(exit_code);
}
#endif /* MBEDTLS_X509_CSR_WRITE_C && MBEDTLS_PK_PARSE_C && MBEDTLS_FS_IO &&
          MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C && MBEDTLS_PEM_WRITE_C */