mirror of
https://github.com/pgpainless/pgpainless.git
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396 lines
16 KiB
Java
396 lines
16 KiB
Java
// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
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//
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// SPDX-License-Identifier: Apache-2.0
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package org.pgpainless.wot;
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import java.io.IOException;
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import java.util.ArrayList;
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import java.util.Date;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.util.NoSuchElementException;
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import org.bouncycastle.bcpg.sig.RevocationReason;
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import org.bouncycastle.openpgp.PGPPublicKey;
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import org.bouncycastle.openpgp.PGPPublicKeyRing;
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import org.bouncycastle.openpgp.PGPSignature;
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import org.pgpainless.PGPainless;
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import org.pgpainless.algorithm.KeyFlag;
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import org.pgpainless.algorithm.RevocationState;
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import org.pgpainless.exception.SignatureValidationException;
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import org.pgpainless.key.OpenPgpFingerprint;
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import org.pgpainless.key.info.KeyRingInfo;
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import org.pgpainless.key.util.KeyRingUtils;
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import org.pgpainless.key.util.RevocationAttributes;
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import org.pgpainless.policy.Policy;
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import org.pgpainless.signature.SignatureUtils;
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import org.pgpainless.signature.consumer.SignatureVerifier;
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import org.pgpainless.signature.subpackets.SignatureSubpacketsUtil;
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import org.pgpainless.wot.dijkstra.sq.CertSynopsis;
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import org.pgpainless.wot.dijkstra.sq.Certification;
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import org.pgpainless.wot.dijkstra.sq.CertificationSet;
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import org.pgpainless.wot.dijkstra.sq.Network;
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import org.pgpainless.wot.dijkstra.sq.ReferenceTime;
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import org.pgpainless.wot.sugar.IterableIterator;
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import org.pgpainless.wot.sugar.PrefixedIterator;
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import org.pgpainless.wot.sugar.Supplier;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import pgp.cert_d.PGPCertificateDirectory;
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import pgp.certificate_store.certificate.Certificate;
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import pgp.certificate_store.exception.BadDataException;
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/**
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* Build a Web of Trust from a set of certificates.
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* <p>
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* The process of building a WoT is as follows:
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* <ul>
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* <li>Consume and synopsize all certificates as network nodes</li>
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* <li>Iterate over cross-certificate signatures and perform signature verification</li>
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* <li>Identify signatures as edges between nodes</li>
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* </ul>
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*
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* @see <a href="https://sequoia-pgp.gitlab.io/sequoia-wot/">OpenPGP Web of Trust</a>
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*/
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public class WebOfTrust implements CertificateAuthority {
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private static final Logger LOGGER = LoggerFactory.getLogger(WebOfTrust.class);
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private final PGPCertificateDirectory certificateStore;
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private Network network;
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public WebOfTrust(PGPCertificateDirectory certificateStore) {
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this.certificateStore = certificateStore;
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}
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/**
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* Do the heavy lifting of calculating the web of trust.
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*/
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public void initialize() throws BadDataException, IOException {
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Certificate trustRoot = null;
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try {
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trustRoot = certificateStore.getTrustRootCertificate();
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} catch (NoSuchElementException e) {
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// ignore
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}
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Iterator<Certificate> certificates = certificateStore.items();
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Iterator<Certificate> withTrustRoot = new PrefixedIterator<>(trustRoot, certificates);
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IterableIterator<Certificate> iterable = new IterableIterator<>(withTrustRoot);
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network = fromCertificates(iterable, PGPainless.getPolicy(), ReferenceTime.now());
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}
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/**
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* Create a {@link Network} from a set of certificates.
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*
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* @param certificates set of certificates
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* @param policy evaluation policy
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* @param optReferenceTime reference time for evaluation
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* @return network
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*/
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public static Network fromCertificates(
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Iterable<Certificate> certificates,
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Policy policy,
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ReferenceTime optReferenceTime) {
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ReferenceTime referenceTime = optReferenceTime == null ? ReferenceTime.now() : optReferenceTime;
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List<KeyRingInfo> validCerts = parseValidCertificates(certificates, policy, referenceTime.getTimestamp());
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LOGGER.debug("Successfully parsed " + validCerts.size() + " certificates.");
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return fromValidCertificates(
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validCerts,
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policy,
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referenceTime
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);
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}
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private static List<KeyRingInfo> parseValidCertificates(Iterable<Certificate> certificates, Policy policy, Date referenceTime) {
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// Parse all certificates
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List<KeyRingInfo> validCerts = new ArrayList<>();
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for (Certificate cert : certificates) {
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try {
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PGPPublicKeyRing publicKey = PGPainless.readKeyRing().publicKeyRing(cert.getInputStream());
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// No Certificate data
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if (publicKey == null) {
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throw new IOException("Certificate " + cert.getFingerprint() + " was null. No certificate data?");
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}
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KeyRingInfo info = new KeyRingInfo(publicKey, policy, referenceTime);
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if (info.getValidUserIds().isEmpty()) {
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LOGGER.warn("Certificate " + cert.getFingerprint() + " has no valid user-ids. Ignore.");
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// Ignore invalid cert
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// TODO: Allow user-id-less certificates?
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} else {
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validCerts.add(info);
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}
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} catch (IOException e) {
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LOGGER.warn("Could not parse certificate " + cert.getFingerprint(), e);
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}
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}
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return validCerts;
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}
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/**
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* Create a {@link Network} from a set of validated certificates.
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*
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* @param validatedCertificates set of validated certificates
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* @param referenceTime reference time
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* @return network
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*/
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public static Network fromValidCertificates(
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List<KeyRingInfo> validatedCertificates,
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Policy policy,
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ReferenceTime referenceTime) {
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// TODO: Move heavy lifting from NetworkBuilder constructor to buildNetwork()?
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NetworkBuilder nb = new NetworkBuilder(validatedCertificates, policy, referenceTime);
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return nb.buildNetwork();
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}
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/**
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* Class for building the {@link Network Flow network} from the given set of OpenPGP keys.
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*
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*/
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private static final class NetworkBuilder {
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// certificates keyed by fingerprint
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private final Map<OpenPgpFingerprint, KeyRingInfo> byFingerprint = new HashMap<>();
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// certificates keyed by (sub-) key-id
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private final Map<Long, List<KeyRingInfo>> byKeyId = new HashMap<>();
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// certificate synopses keyed by fingerprint
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private final Map<OpenPgpFingerprint, CertSynopsis> certSynopsisMap = new HashMap<>();
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// Issuer -> Targets, edges keyed by issuer
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private final Map<OpenPgpFingerprint, List<CertificationSet>> edges = new HashMap<>();
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// Target -> Issuers, edges keyed by target
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private final Map<OpenPgpFingerprint, List<CertificationSet>> reverseEdges = new HashMap<>();
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private final Policy policy;
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private final ReferenceTime referenceTime;
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private NetworkBuilder(List<KeyRingInfo> validatedCertificates,
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Policy policy,
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ReferenceTime referenceTime) {
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this.policy = policy;
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this.referenceTime = referenceTime;
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synopsizeCertificates(validatedCertificates);
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findEdges(validatedCertificates);
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}
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private void synopsizeCertificates(List<KeyRingInfo> validatedCertificates) {
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for (KeyRingInfo cert : validatedCertificates) {
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synopsize(cert);
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}
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}
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private void synopsize(KeyRingInfo cert) {
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// index by fingerprint
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if (!byFingerprint.containsKey(cert.getFingerprint())) {
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byFingerprint.put(cert.getFingerprint(), cert);
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}
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// index by key-ID
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List<KeyRingInfo> certsWithKey = byKeyId.get(cert.getKeyId());
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// noinspection Java8MapApi
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if (certsWithKey == null) {
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certsWithKey = new ArrayList<>();
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// TODO: Something is fishy here...
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for (PGPPublicKey key : cert.getValidSubkeys()) {
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byKeyId.put(key.getKeyID(), certsWithKey);
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}
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}
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certsWithKey.add(cert);
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Map<String, RevocationState> userIds = new HashMap<>();
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for (String userId : cert.getUserIds()) {
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RevocationState state = revocationStateFromSignature(cert.getUserIdRevocation(userId));
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userIds.put(userId, state);
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}
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// index synopses
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Date expirationDate;
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try {
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expirationDate = cert.getExpirationDateForUse(KeyFlag.CERTIFY_OTHER);
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} catch (NoSuchElementException e) {
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// Some keys are malformed and have no KeyFlags
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return;
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}
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certSynopsisMap.put(cert.getFingerprint(),
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new CertSynopsis(cert.getFingerprint(),
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expirationDate,
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revocationStateFromSignature(cert.getRevocationSelfSignature()),
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userIds));
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}
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private void findEdges(List<KeyRingInfo> validatedCertificates) {
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// Identify certifications and delegations
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// Target = cert carrying a signature
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for (KeyRingInfo validatedTarget : validatedCertificates) {
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findEdgesWithTarget(validatedTarget);
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}
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}
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private void findEdgesWithTarget(KeyRingInfo validatedTarget) {
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PGPPublicKeyRing validatedTargetKeyRing = KeyRingUtils.publicKeys(validatedTarget.getKeys());
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OpenPgpFingerprint targetFingerprint = OpenPgpFingerprint.of(validatedTargetKeyRing);
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PGPPublicKey targetPrimaryKey = validatedTargetKeyRing.getPublicKey();
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CertSynopsis target = certSynopsisMap.get(targetFingerprint);
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// Direct-Key Signatures (delegations) by X on Y
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List<PGPSignature> delegations = SignatureUtils.getDelegations(validatedTargetKeyRing);
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for (PGPSignature delegation : delegations) {
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processDelegation(targetPrimaryKey, target, delegation);
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}
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// Certification Signatures by X on Y over user-ID U
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Iterator<String> userIds = targetPrimaryKey.getUserIDs();
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while (userIds.hasNext()) {
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String userId = userIds.next();
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List<PGPSignature> userIdSigs = SignatureUtils.get3rdPartyCertificationsFor(userId, validatedTargetKeyRing);
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processCertification(targetPrimaryKey, target, userId, userIdSigs);
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}
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}
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private void processDelegation(PGPPublicKey targetPrimaryKey,
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CertSynopsis target,
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PGPSignature delegation) {
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List<KeyRingInfo> issuerCandidates = byKeyId.get(delegation.getKeyID());
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if (issuerCandidates == null) {
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return;
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}
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for (KeyRingInfo candidate : issuerCandidates) {
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PGPPublicKeyRing issuerKeyRing = KeyRingUtils.publicKeys(candidate.getKeys());
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OpenPgpFingerprint issuerFingerprint = OpenPgpFingerprint.of(issuerKeyRing);
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PGPPublicKey issuerSigningKey = issuerKeyRing.getPublicKey(delegation.getKeyID());
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CertSynopsis issuer = certSynopsisMap.get(issuerFingerprint);
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try {
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boolean valid = SignatureVerifier.verifyDirectKeySignature(delegation, issuerSigningKey,
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targetPrimaryKey, policy, referenceTime.getTimestamp());
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if (valid) {
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indexEdge(CertificationFactory.fromDelegation(issuer, target, delegation));
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}
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} catch (SignatureValidationException e) {
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LOGGER.warn("Cannot verify signature by " + issuerFingerprint + " on cert of " + OpenPgpFingerprint.of(targetPrimaryKey), e);
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}
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}
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}
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private void processCertification(PGPPublicKey targetPrimaryKey,
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CertSynopsis target,
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String userId, List<PGPSignature> userIdSigs) {
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for (PGPSignature certification : userIdSigs) {
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List<KeyRingInfo> issuerCandidates = byKeyId.get(certification.getKeyID());
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if (issuerCandidates == null) {
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continue;
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}
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for (KeyRingInfo candidate : issuerCandidates) {
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PGPPublicKeyRing issuerKeyRing = KeyRingUtils.publicKeys(candidate.getKeys());
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OpenPgpFingerprint issuerFingerprint = OpenPgpFingerprint.of(issuerKeyRing);
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PGPPublicKey issuerSigningKey = issuerKeyRing.getPublicKey(certification.getKeyID());
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CertSynopsis issuer = certSynopsisMap.get(issuerFingerprint);
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try {
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boolean valid = SignatureVerifier.verifySignatureOverUserId(userId, certification,
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issuerSigningKey, targetPrimaryKey, policy, referenceTime.getTimestamp());
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if (valid) {
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indexEdge(CertificationFactory.fromCertification(issuer, userId, target, certification));
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}
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} catch (SignatureValidationException e) {
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LOGGER.warn("Cannot verify signature for '" + userId + "' by " + issuerFingerprint + " on cert of " + target.getFingerprint(), e);
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}
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}
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}
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}
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private void indexEdge(Certification certification) {
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OpenPgpFingerprint issuer = certification.getIssuer().getFingerprint();
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OpenPgpFingerprint target = certification.getTarget().getFingerprint();
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List<CertificationSet> outEdges = getOrDefault(edges, issuer, ArrayList::new);
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indexOutEdge(outEdges, certification);
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List<CertificationSet> inEdges = getOrDefault(reverseEdges, target, ArrayList::new);
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indexInEdge(inEdges, certification);
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}
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private void indexOutEdge(List<CertificationSet> outEdges, Certification certification) {
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OpenPgpFingerprint target = certification.getTarget().getFingerprint();
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for (CertificationSet outEdge : outEdges) {
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if (target.equals(outEdge.getTarget().getFingerprint())) {
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outEdge.add(certification);
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return;
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}
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}
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outEdges.add(CertificationSet.fromCertification(certification));
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}
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private void indexInEdge(List<CertificationSet> inEdges, Certification certification) {
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OpenPgpFingerprint issuer = certification.getIssuer().getFingerprint();
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for (CertificationSet inEdge : inEdges) {
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if (issuer.equals(inEdge.getIssuer().getFingerprint())) {
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inEdge.add(certification);
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return;
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}
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}
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inEdges.add(CertificationSet.fromCertification(certification));
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}
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/**
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* Return the constructed, initialized {@link Network}.
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*
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* @return finished network
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*/
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public Network buildNetwork() {
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return new Network(certSynopsisMap, edges, reverseEdges, referenceTime);
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}
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}
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Network getNetwork() {
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return network;
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}
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// Map signature to its revocation state
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private static RevocationState revocationStateFromSignature(PGPSignature revocation) {
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if (revocation == null) {
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return RevocationState.notRevoked();
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}
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RevocationReason revocationReason = SignatureSubpacketsUtil.getRevocationReason(revocation);
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if (revocationReason == null) {
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return RevocationState.hardRevoked();
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}
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return RevocationAttributes.Reason.isHardRevocation(revocationReason.getRevocationReason()) ?
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RevocationState.hardRevoked() : RevocationState.softRevoked(revocation.getCreationTime());
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}
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// Java 8 is not supported on old Android
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private static <K, V> V getOrDefault(Map<K, V> map, K key, Supplier<V> defaultValue) {
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V value = map.get(key);
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if (value == null) {
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value = defaultValue.get();
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map.put(key, value);
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}
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return value;
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}
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@Override
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public boolean isAuthorized(PGPPublicKeyRing certificate, String userId) {
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// TODO: Heiko! Implement!
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return false;
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}
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@Override
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public String toString() {
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return network.toString();
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}
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}
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