CMS Decrypt

test_dec.cpp

// original: openssl/demos/cms/cms_dec.c
// g++ test_dec.cpp -lcrypto -o test_dec

#include <iostream>
#include <string>

#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/ssl.h>
#include <openssl/pkcs7.h>
#include <openssl/safestack.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>     /* X509_PURPOSE_ANY */
#include <openssl/x509_vfy.h>
#include <openssl/cms.h>
#include <openssl/pem.h>

std::string get_bio_str(BIO* bio) {
    char* data;
    BIO_get_mem_data(bio, &data);

    return data;
}

void print_openssl_errors() {
    ERR_print_errors_fp(stderr);
}

void exit_openssl_error() {
    print_openssl_errors();
    exit(1);
}

int main(int argc, char* argv[]) {
    if (argc < 3) {
        std::cerr << argv[0] << " cert-file target-file" << std::endl;
        return 1;
    }

    const char *cert_file_path = argv[1];
    const char *target_file_path = argv[2];

    OpenSSL_add_all_algorithms();
    ERR_load_crypto_strings();

    BIO *cert_io = BIO_new_file(cert_file_path, "r");
    if (!cert_io)
        exit_openssl_error();

    X509 *rcert = PEM_read_bio_X509(cert_io, NULL, 0, NULL);
    if (!rcert)
        exit_openssl_error();

    BIO_reset(cert_io);

    EVP_PKEY *rkey = PEM_read_bio_PrivateKey(cert_io, NULL, 0, NULL);
    if (!rkey)
        exit_openssl_error();

    BIO *in = BIO_new_file(target_file_path, "r");
    if (!in)
        exit_openssl_error();

    CMS_ContentInfo *cms = SMIME_read_CMS(in, NULL);
    if (!cms)
        exit_openssl_error();

    BIO *out = BIO_new(BIO_s_mem());
    if (!out)
        exit_openssl_error();

    if (!CMS_decrypt(cms, rkey, rcert, NULL, out, 0))
        exit_openssl_error();

    std::cout << get_bio_str(out) << std::endl;

    CMS_ContentInfo_free(cms);
    X509_free(rcert);

    BIO_free(cert_io);
    BIO_free(in);
    BIO_free(out);

    return 0;
}