openssl/demos/cms/cms_denc.c

/* 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 = 1;

	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;

	/* sk_X509_pop_free will 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)
		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 = 0;

	err:

	if (ret)
		{
		fprintf(stderr, "Error Encrypting Data\n");
		ERR_print_errors_fp(stderr);
		}

	if (cms)
		CMS_ContentInfo_free(cms);
	if (rcert)
		X509_free(rcert);
	if (recips)
		sk_X509_pop_free(recips, X509_free);

	if (in)
		BIO_free(in);
	if (out)
		BIO_free(out);
	if (dout)
		BIO_free(dout);
	if (tbio)
		BIO_free(tbio);

	return ret;

	}