001// SPDX-FileCopyrightText: 2018 Paul Schaub <vanitasvitae@fsfe.org>
002//
003// SPDX-License-Identifier: Apache-2.0
004
005package org.pgpainless.decryption_verification;
006
007import javax.annotation.Nonnull;
008import javax.annotation.Nullable;
009
010import org.bouncycastle.openpgp.PGPPublicKeyRing;
011
012public interface MissingPublicKeyCallback {
013
014    /**
015     * This method gets called if we encounter a signature made by a key which was not provided for signature verification.
016     * If you cannot provide the requested key, it is safe to return null here.
017     * PGPainless will then continue verification with the next signature.
018     *
019     * Note: The key-id might belong to a subkey, so be aware that when looking up the {@link PGPPublicKeyRing},
020     * you may not only search for the key-id on the key rings primary key!
021     *
022     * It would be super cool to provide the OpenPgp fingerprint here, but unfortunately one-pass-signatures
023     * only contain the key id (see https://datatracker.ietf.org/doc/html/rfc4880#section-5.4)
024     *
025     * @param keyId ID of the missing signing (sub)key
026     *
027     * @return keyring containing the key or null
028     */
029    @Nullable PGPPublicKeyRing onMissingPublicKeyEncountered(@Nonnull Long keyId);
030
031}