C GPGMe ignore user keyring

I recently finished a program that downloads public keys into memory, then creates an encrypted message with all of them. However, I have been having some difficulty creating a list of only the keys I download. When they are first downloaded, they are stored in gpgme_data_t. I was unable to find a function that converted this directly to a gpgme_key_t. Because of this, I just imported them into a new context. However, when I went to export the keys again in order to build a list for gpgme_op_encrypt, I end up with other keys from my local keyring. I tried setting disable-gpgconf, but that didn’t change anything. I also tried setting GNUPGHOME to a tmp directory, but that caused a segmentation fault when I called encrypt. Is there a way not to import the user’s keyring or to convert a gpgme_data_t or char* to a gpgme_key_t?

Solution

Is there a way not to import the user's keyring

To prevent loading the users keyring, you will need set the GnuPG homedir of the context to someplace else.

Below is an example without any error checking

#include <gpgme.h>
#include <locale.h>

int main() {
    gpgme_ctx_t ctx;  // the context
    gpgme_error_t err; // errors
    gpgme_key_t key; // the key
    gpgme_keylist_result_t result; // the keylist results

    setlocale (LC_ALL, ""); // set the locale
    gpgme_set_locale (NULL, LC_CTYPE, setlocale (LC_CTYPE, NULL)); // set gpgme locale
    gpgme_check_version(NULL); // initialize gpgme

    gpgme_new (&ctx); // initialize the context

    gpgme_ctx_set_engine_info (ctx, GPGME_PROTOCOL_OpenPGP, NULL, "/tmp/xyz"); // set the context GNUPGHOME to "/tmp/xyz"

    gpgme_op_keylist_start (ctx, NULL, 0); // start the keylist

    while (!(err = gpgme_op_keylist_next (ctx, &key))) { // loop through the keys in the keyring
        fprintf(stdout, "Key ID: %s\n", key->subkeys->keyid); // print out the keyid
        gpgme_key_unref (key); // release the key reference
    }

    gpgme_release(ctx); // release the context, all done

    return 0;
}