demos/cms/cms_denc.c

/*
 * Copyright 2008-2025 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * S/MIME detached data encrypt example: rarely done but should the need
 * arise this is an example....
 */
#include <openssl/pem.h>
#include <openssl/cms.h>
#include <openssl/err.h>

int main(int argc, char **argv)
{
    BIO *in = NULL, *out = NULL, *tbio = NULL, *dout = NULL;
    X509 *rcert = NULL;
    STACK_OF(X509) *recips = NULL;
    CMS_ContentInfo *cms = NULL;
    int ret = EXIT_FAILURE;

    int flags = CMS_STREAM | CMS_DETACHED;

    OpenSSL_add_all_algorithms();
    ERR_load_crypto_strings();

    /* Read in recipient certificate */
    tbio = BIO_new_file("signer.pem", "r");

    if (!tbio)
        goto err;

    rcert = PEM_read_bio_X509(tbio, NULL, 0, NULL);

    if (!rcert)
        goto err;

    /* Create recipient STACK and add recipient cert to it */
    recips = sk_X509_new_null();

    if (!recips || !sk_X509_push(recips, rcert))
        goto err;

    /*
     * OSSL_STACK_OF_X509_free() free up recipient STACK and its contents
     * so set rcert to NULL so it isn't freed up twice.
     */
    rcert = NULL;

    /* Open content being encrypted */

    in = BIO_new_file("encr.txt", "r");

    dout = BIO_new_file("smencr.out", "wb");

    if (in == NULL || dout == NULL)
        goto err;

    /* encrypt content */
    cms = CMS_encrypt(recips, in, EVP_des_ede3_cbc(), flags);

    if (!cms)
        goto err;

    out = BIO_new_file("smencr.pem", "w");
    if (!out)
        goto err;

    if (!CMS_final(cms, in, dout, flags))
        goto err;

    /* Write out CMS structure without content */
    if (!PEM_write_bio_CMS(out, cms))
        goto err;

    ret = EXIT_SUCCESS;
err:
    if (ret != EXIT_SUCCESS) {
        fprintf(stderr, "Error Encrypting Data\n");
        ERR_print_errors_fp(stderr);
    }

    CMS_ContentInfo_free(cms);
    X509_free(rcert);
    OSSL_STACK_OF_X509_free(recips);
    BIO_free(in);
    BIO_free(out);
    BIO_free(dout);
    BIO_free(tbio);
    return ret;
}