pem2der.c

/*
 *  Convert PEM to DER
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 */

#include "mbedtls/build_info.h"

#include "mbedtls/platform.h"

#if defined(MBEDTLS_BASE64_C) && defined(MBEDTLS_FS_IO)
#include "mbedtls/error.h"
#include "mbedtls/base64.h"

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

#define DFL_FILENAME            "file.pem"
#define DFL_OUTPUT_FILENAME     "file.der"

#define USAGE \
    "\n usage: pem2der param=<>...\n"                   \
    "\n acceptable parameters:\n"                       \
    "    filename=%%s         default: file.pem\n"      \
    "    output_file=%%s      default: file.der\n"      \
    "\n"

#if !defined(MBEDTLS_BASE64_C) || !defined(MBEDTLS_FS_IO)
int main(void)
{
    mbedtls_printf("MBEDTLS_BASE64_C and/or MBEDTLS_FS_IO not defined.\n");
    mbedtls_exit(0);
}
#else


/*
 * global options
 */
struct options {
    const char *filename;       /* filename of the input file             */
    const char *output_file;    /* where to store the output              */
} opt;

static int convert_pem_to_der(const unsigned char *input, size_t ilen,
                              unsigned char *output, size_t *olen)
{
    int ret;
    const unsigned char *s1, *s2, *end = input + ilen;
    size_t len = 0;

    s1 = (unsigned char *) strstr((const char *) input, "-----BEGIN");
    if (s1 == NULL) {
        return -1;
    }

    s2 = (unsigned char *) strstr((const char *) input, "-----END");
    if (s2 == NULL) {
        return -1;
    }

    s1 += 10;
    while (s1 < end && *s1 != '-') {
        s1++;
    }
    while (s1 < end && *s1 == '-') {
        s1++;
    }
    if (*s1 == '\r') {
        s1++;
    }
    if (*s1 == '\n') {
        s1++;
    }

    if (s2 <= s1 || s2 > end) {
        return -1;
    }

    ret = mbedtls_base64_decode(NULL, 0, &len, (const unsigned char *) s1, s2 - s1);
    if (ret == MBEDTLS_ERR_BASE64_INVALID_CHARACTER) {
        return ret;
    }

    if (len > *olen) {
        return -1;
    }

    if ((ret = mbedtls_base64_decode(output, len, &len, (const unsigned char *) s1,
                                     s2 - s1)) != 0) {
        return ret;
    }

    *olen = len;

    return 0;
}

/*
 * Load all data from a file into a given buffer.
 */
static int load_file(const char *path, unsigned char **buf, size_t *n)
{
    FILE *f;
    long size;

    if ((f = fopen(path, "rb")) == NULL) {
        return -1;
    }

    fseek(f, 0, SEEK_END);
    if ((size = ftell(f)) == -1) {
        fclose(f);
        return -1;
    }
    fseek(f, 0, SEEK_SET);

    *n = (size_t) size;

    if (*n + 1 == 0 ||
        (*buf = mbedtls_calloc(1, *n + 1)) == NULL) {
        fclose(f);
        return -1;
    }

    if (fread(*buf, 1, *n, f) != *n) {
        fclose(f);
        free(*buf);
        *buf = NULL;
        return -1;
    }

    fclose(f);

    (*buf)[*n] = '\0';

    return 0;
}

/*
 * Write buffer to a file
 */
static int write_file(const char *path, unsigned char *buf, size_t n)
{
    FILE *f;

    if ((f = fopen(path, "wb")) == NULL) {
        return -1;
    }

    if (fwrite(buf, 1, n, f) != n) {
        fclose(f);
        return -1;
    }

    fclose(f);
    return 0;
}

int main(int argc, char *argv[])
{
    int ret = 1;
    int exit_code = MBEDTLS_EXIT_FAILURE;
    unsigned char *pem_buffer = NULL;
    unsigned char der_buffer[4096];
    char buf[1024];
    size_t pem_size, der_size = sizeof(der_buffer);
    int i;
    char *p, *q;

    /*
     * Set to sane values
     */
    memset(buf, 0, sizeof(buf));
    memset(der_buffer, 0, sizeof(der_buffer));

    if (argc < 2) {
usage:
        mbedtls_printf(USAGE);
        goto exit;
    }

    opt.filename            = DFL_FILENAME;
    opt.output_file         = DFL_OUTPUT_FILENAME;

    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, "output_file") == 0) {
            opt.output_file = q;
        } else {
            goto usage;
        }
    }

    /*
     * 1.1. Load the PEM file
     */
    mbedtls_printf("\n  . Loading the PEM file ...");
    fflush(stdout);

    ret = load_file(opt.filename, &pem_buffer, &pem_size);

    if (ret != 0) {
#ifdef MBEDTLS_ERROR_C
        mbedtls_strerror(ret, buf, 1024);
#endif
        mbedtls_printf(" failed\n  !  load_file returned %d - %s\n\n", ret, buf);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    /*
     * 1.2. Convert from PEM to DER
     */
    mbedtls_printf("  . Converting from PEM to DER ...");
    fflush(stdout);

    if ((ret = convert_pem_to_der(pem_buffer, pem_size, der_buffer, &der_size)) != 0) {
#ifdef MBEDTLS_ERROR_C
        mbedtls_strerror(ret, buf, 1024);
#endif
        mbedtls_printf(" failed\n  !  convert_pem_to_der %d - %s\n\n", ret, buf);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    /*
     * 1.3. Write the DER file
     */
    mbedtls_printf("  . Writing the DER file ...");
    fflush(stdout);

    ret = write_file(opt.output_file, der_buffer, der_size);

    if (ret != 0) {
#ifdef MBEDTLS_ERROR_C
        mbedtls_strerror(ret, buf, 1024);
#endif
        mbedtls_printf(" failed\n  !  write_file returned %d - %s\n\n", ret, buf);
        goto exit;
    }

    mbedtls_printf(" ok\n");

    exit_code = MBEDTLS_EXIT_SUCCESS;

exit:
    free(pem_buffer);

    mbedtls_exit(exit_code);
}
#endif /* MBEDTLS_BASE64_C && MBEDTLS_FS_IO */