java/com/google/gerrit/gpg/PublicKeyStore.java - gerrit.git - Git at Google

 // Copyright (C) 2015 The Android Open Source Project
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 // http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 package com.google.gerrit.gpg;

 import static com.google.common.base.Preconditions.checkState;
 import static com.google.gerrit.server.update.context.RefUpdateContext.RefUpdateType.GPG_KEYS_MODIFICATION;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.eclipse.jgit.lib.Constants.EMPTY_TREE_ID;
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;

 import com.google.common.base.Preconditions;
 import com.google.common.io.ByteStreams;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.git.LockFailureException;
 import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.server.update.context.RefUpdateContext;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import org.bouncycastle.bcpg.ArmoredInputStream;
 import org.bouncycastle.bcpg.ArmoredOutputStream;
 import org.bouncycastle.openpgp.PGPException;
 import org.bouncycastle.openpgp.PGPPublicKey;
 import org.bouncycastle.openpgp.PGPPublicKeyRing;
 import org.bouncycastle.openpgp.PGPPublicKeyRingCollection;
 import org.bouncycastle.openpgp.PGPSignature;
 import org.bouncycastle.openpgp.bc.BcPGPObjectFactory;
 import org.bouncycastle.openpgp.operator.bc.BcPGPContentVerifierBuilderProvider;
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.lib.CommitBuilder;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.notes.Note;
 import org.eclipse.jgit.notes.NoteMap;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.util.NB;

 /**
  * Store of GPG public keys in git notes.
  *
  * <p>Keys are stored in filenames based on their hex key ID, padded out to 40 characters to match
  * the length of a SHA-1. (This is to easily reuse existing fanout code in {@link NoteMap}, and may
  * be changed later after an appropriate transition.)
  *
  * <p>The contents of each file is an ASCII armored stream containing one or more public key rings
  * matching the ID. Multiple keys are supported because forging a key ID is possible, but such a key
  * cannot be used to verify signatures produced with the correct key.
  *
  * <p>Subkeys are mapped to the master GPG key in the same NoteMap.
  *
  * <p>No additional checks are performed on the key after reading; callers should only trust keys
  * after checking with a {@link PublicKeyChecker}.
  */
 public class PublicKeyStore implements AutoCloseable {
   /** Ref where GPG public keys are stored. */
   public static final String REFS_GPG_KEYS = "refs/meta/gpg-keys";

   /**
    * Choose the public key that produced a signature.
    *
    * <p>
    *
    * @param keyRings candidate keys.
    * @param sig signature object.
    * @param data signed payload.
    * @return the key chosen from {@code keyRings} that was able to verify the signature, or {@code
    *     null} if none was found.
    * @throws PGPException if an error occurred verifying the signature.
    */
   @Nullable
   public static PGPPublicKey getSigner(
       Iterable<PGPPublicKeyRing> keyRings, PGPSignature sig, byte[] data) throws PGPException {
     for (PGPPublicKeyRing kr : keyRings) {
       // Possibly return a signing subkey in case it differs from the master public key
       PGPPublicKey k = kr.getPublicKey(sig.getKeyID());
       if (k == null) {
         throw new IllegalStateException(
             "No public key found for ID: " + keyIdToString(sig.getKeyID()));
       }
       sig.init(new BcPGPContentVerifierBuilderProvider(), k);
       sig.update(data);
       if (sig.verify()) {
         // If the signature was made using a subkey, return the main public key.
         // This enables further validity checks, like user ID checks, that can only
         // be performed using the master public key.
         return kr.getPublicKey();
       }
     }
     return null;
   }

   /**
    * Choose the public key that produced a certification.
    *
    * <p>
    *
    * @param keyRings candidate keys.
    * @param sig signature object.
    * @param userId user ID being certified.
    * @param key key being certified.
    * @return the key chosen from {@code keyRings} that was able to verify the certification, or
    *     {@code null} if none was found.
    * @throws PGPException if an error occurred verifying the certification.
    */
   @Nullable
   public static PGPPublicKey getSigner(
       Iterable<PGPPublicKeyRing> keyRings, PGPSignature sig, String userId, PGPPublicKey key)
       throws PGPException {
     for (PGPPublicKeyRing kr : keyRings) {
       PGPPublicKey k = kr.getPublicKey();
       sig.init(new BcPGPContentVerifierBuilderProvider(), k);
       if (sig.verifyCertification(userId, key)) {
         return k;
       }
     }
     return null;
   }

   private final Repository repo;
   private ObjectReader reader;
   private RevCommit tip;
   private NoteMap notes;
   private Map<Fingerprint, PGPPublicKeyRing> toAdd;
   private Set<Fingerprint> toRemove;

   /** @param repo repository to read keys from. */
   public PublicKeyStore(Repository repo) {
     this.repo = repo;
     toAdd = new HashMap<>();
     toRemove = new HashSet<>();
   }

   @Override
   public void close() {
     reset();
   }

   private void reset() {
     if (reader != null) {
       reader.close();
       reader = null;
       notes = null;
     }
   }

   private void load() throws IOException {
     reset();
     reader = repo.newObjectReader();

     Ref ref = repo.getRefDatabase().exactRef(REFS_GPG_KEYS);
     if (ref == null) {
       return;
     }
     try (RevWalk rw = new RevWalk(reader)) {
       tip = rw.parseCommit(ref.getObjectId());
       notes = NoteMap.read(reader, tip);
     }
   }

   /**
    * Read public keys with the given key ID.
    *
    * <p>Keys should not be trusted unless checked with {@link PublicKeyChecker}.
    *
    * <p>Multiple calls to this method use the same state of the key ref; to reread the ref, call
    * {@link #close()} first.
    *
    * @param keyId key ID.
    * @return any keys found that could be successfully parsed.
    * @throws PGPException if an error occurred parsing the key data.
    * @throws IOException if an error occurred reading the repository data.
    */
   public PGPPublicKeyRingCollection get(long keyId) throws PGPException, IOException {
     return new PGPPublicKeyRingCollection(get(keyId, null));
   }

   /**
    * Read public key with the given fingerprint.
    *
    * <p>Keys should not be trusted unless checked with {@link PublicKeyChecker}.
    *
    * <p>Multiple calls to this method use the same state of the key ref; to reread the ref, call
    * {@link #close()} first.
    *
    * @param fingerprint key fingerprint.
    * @return the key if found, or {@code null}.
    * @throws PGPException if an error occurred parsing the key data.
    * @throws IOException if an error occurred reading the repository data.
    */
   @Nullable
   public PGPPublicKeyRing get(byte[] fingerprint) throws PGPException, IOException {
     List<PGPPublicKeyRing> keyRings = get(Fingerprint.getId(fingerprint), fingerprint);
     return !keyRings.isEmpty() ? keyRings.get(0) : null;
   }

   private List<PGPPublicKeyRing> get(long keyId, byte[] fp) throws IOException {
     if (reader == null) {
       load();
     }
     if (notes == null) {
       return Collections.emptyList();
     }

     return get(keyObjectId(keyId), fp);
   }

   private List<PGPPublicKeyRing> get(ObjectId keyObjectId, byte[] fp) throws IOException {
     Note note = notes.getNote(keyObjectId);
     if (note == null) {
       return Collections.emptyList();
     }

     return readKeysFromNote(note, fp);
   }

   private List<PGPPublicKeyRing> readKeysFromNote(Note note, byte[] fp)
       throws IOException, MissingObjectException, IncorrectObjectTypeException {
     boolean foundAtLeastOneKey = false;
     List<PGPPublicKeyRing> keys = new ArrayList<>();
     ObjectId data = note.getData();
     try (InputStream stream = reader.open(data, OBJ_BLOB).openStream()) {
       byte[] bytes = ByteStreams.toByteArray(stream);
       InputStream in = new ByteArrayInputStream(bytes);
       while (true) {
         @SuppressWarnings("unchecked")
         Iterator<Object> it = new BcPGPObjectFactory(new ArmoredInputStream(in)).iterator();
         if (!it.hasNext()) {
           break;
         }
         foundAtLeastOneKey = true;
         Object obj = it.next();
         if (obj instanceof PGPPublicKeyRing) {
           PGPPublicKeyRing kr = (PGPPublicKeyRing) obj;
           if (fp == null || Arrays.equals(fp, kr.getPublicKey().getFingerprint())) {
             keys.add(kr);
           }
         }
         checkState(!it.hasNext(), "expected one PGP object per ArmoredInputStream");
       }

       if (foundAtLeastOneKey) {
         return keys;
       }

       // Subkey handling
       String id = new String(bytes, UTF_8);
       Preconditions.checkArgument(ObjectId.isId(id), "Not valid SHA1: " + id);
       return get(ObjectId.fromString(id), fp);
     }
   }

   public void rebuildSubkeyMasterKeyMap()
       throws MissingObjectException, IncorrectObjectTypeException, IOException {
     if (reader == null) {
       load();
     }
     if (notes != null) {
       try (ObjectInserter ins = repo.newObjectInserter()) {
         for (Note note : notes) {
           for (PGPPublicKeyRing keyRing :
               new PGPPublicKeyRingCollection(readKeysFromNote(note, null))) {
             long masterKeyId = keyRing.getPublicKey().getKeyID();
             ObjectId masterKeyObjectId = keyObjectId(masterKeyId);
             saveSubkeyMapping(ins, keyRing, masterKeyId, masterKeyObjectId);
           }
         }
       }
     }
   }

   /**
    * Add a public key to the store.
    *
    * <p>Multiple calls may be made to buffer keys in memory, and they are not saved until {@link
    * #save(CommitBuilder)} is called.
    *
    * @param keyRing a key ring containing exactly one public master key.
    */
   public void add(PGPPublicKeyRing keyRing) {
     int numMaster = 0;
     for (PGPPublicKey key : keyRing) {
       if (key.isMasterKey()) {
         numMaster++;
       }
     }
     // We could have an additional sanity check to ensure all subkeys belong to
     // this master key, but that requires doing actual signature verification
     // here. The alternative is insane but harmless.
     if (numMaster != 1) {
       throw new IllegalArgumentException("Exactly 1 master key is required, found " + numMaster);
     }
     Fingerprint fp = new Fingerprint(keyRing.getPublicKey().getFingerprint());
     toAdd.put(fp, keyRing);
     toRemove.remove(fp);
   }

   /**
    * Remove a public key from the store.
    *
    * <p>Multiple calls may be made to buffer deletes in memory, and they are not saved until {@link
    * #save(CommitBuilder)} is called.
    *
    * @param fingerprint the fingerprint of the key to remove.
    */
   public void remove(byte[] fingerprint) {
     Fingerprint fp = new Fingerprint(fingerprint);
     toAdd.remove(fp);
     toRemove.add(fp);
   }

   /**
    * Save pending keys to the store.
    *
    * <p>One commit is created and the ref updated. The pending list is cleared if and only if the
    * ref update succeeds, which allows for easy retries in case of lock failure.
    *
    * @param cb commit builder with at least author and identity populated; tree and parent are
    *     ignored.
    * @return result of the ref update.
    */
   public RefUpdate.Result save(CommitBuilder cb) throws PGPException, IOException {
     if (toAdd.isEmpty() && toRemove.isEmpty()) {
       return RefUpdate.Result.NO_CHANGE;
     }
     if (reader == null) {
       load();
     }
     if (notes == null) {
       notes = NoteMap.newEmptyMap();
     }
     ObjectId newTip;
     try (ObjectInserter ins = repo.newObjectInserter()) {
       for (PGPPublicKeyRing keyRing : toAdd.values()) {
         saveToNotes(ins, keyRing);
       }
       for (Fingerprint fp : toRemove) {
         deleteFromNotes(ins, fp);
       }
       cb.setTreeId(notes.writeTree(ins));
       if (cb.getTreeId().equals(tip != null ? tip.getTree() : EMPTY_TREE_ID)) {
         return RefUpdate.Result.NO_CHANGE;
       }

       if (tip != null) {
         cb.setParentId(tip);
       }
       if (cb.getMessage() == null) {
         int n = toAdd.size() + toRemove.size();
         cb.setMessage(String.format("Update %d public key%s", n, n != 1 ? "s" : ""));
       }
       newTip = ins.insert(cb);
       ins.flush();
     }
     try (RefUpdateContext ctx = RefUpdateContext.open(GPG_KEYS_MODIFICATION)) {
       RefUpdate ru = repo.updateRef(PublicKeyStore.REFS_GPG_KEYS);
       ru.setExpectedOldObjectId(tip);
       ru.setNewObjectId(newTip);
       ru.setRefLogIdent(cb.getCommitter());
       ru.setRefLogMessage("Store public keys", true);
       RefUpdate.Result result = ru.update();
       reset();
       switch (result) {
         case FAST_FORWARD:
         case NEW:
         case NO_CHANGE:
           toAdd.clear();
           toRemove.clear();
           break;
         case LOCK_FAILURE:
           throw new LockFailureException("Failed to store public keys", ru);
         case FORCED:
         case IO_FAILURE:
         case NOT_ATTEMPTED:
         case REJECTED:
         case REJECTED_CURRENT_BRANCH:
         case RENAMED:
         case REJECTED_MISSING_OBJECT:
         case REJECTED_OTHER_REASON:
         default:
           break;
       }
       return result;
     }
   }

   private void saveToNotes(ObjectInserter ins, PGPPublicKeyRing keyRing)
       throws PGPException, IOException {
     long masterKeyId = keyRing.getPublicKey().getKeyID();
     PGPPublicKeyRingCollection existing = get(masterKeyId);
     List<PGPPublicKeyRing> toWrite = new ArrayList<>(existing.size() + 1);
     boolean replaced = false;
     for (PGPPublicKeyRing kr : existing) {
       if (sameKey(keyRing, kr)) {
         toWrite.add(keyRing);
         replaced = true;
       } else {
         toWrite.add(kr);
       }
     }
     if (!replaced) {
       toWrite.add(keyRing);
     }

     ObjectId masterKeyObjectId = keyObjectId(masterKeyId);
     notes.set(masterKeyObjectId, ins.insert(OBJ_BLOB, keysToArmored(toWrite)));

     saveSubkeyMapping(ins, keyRing, masterKeyId, masterKeyObjectId);
   }

   private void saveSubkeyMapping(
       ObjectInserter ins, PGPPublicKeyRing keyRing, long masterKeyId, ObjectId masterKeyObjectId)
       throws IOException {
     // Subkey handling
     byte[] masterKeyBytes = masterKeyObjectId.name().getBytes(UTF_8);
     ObjectId masterKeyObject = null;
     for (PGPPublicKey key : keyRing) {
       long subKeyId = key.getKeyID();
       // Skip master public key
       if (masterKeyId == subKeyId) {
         continue;
       }

       // Insert master key object only once for all subkeys
       if (masterKeyObject == null) {
         masterKeyObject = ins.insert(OBJ_BLOB, masterKeyBytes);
       }

       ObjectId subkeyObjectId = keyObjectId(subKeyId);
       Preconditions.checkArgument(
           notes.get(subkeyObjectId) == null || notes.get(subkeyObjectId).equals(masterKeyObject),
           "Master key differs for subkey: " + subkeyObjectId.name());
       notes.set(subkeyObjectId, masterKeyObject);
     }
   }

   private void deleteFromNotes(ObjectInserter ins, Fingerprint fp)
       throws PGPException, IOException {
     long keyId = fp.getId();
     PGPPublicKeyRingCollection existing = get(keyId);
     List<PGPPublicKeyRing> toWrite = new ArrayList<>(existing.size());
     for (PGPPublicKeyRing kr : existing) {
       if (!fp.equalsBytes(kr.getPublicKey().getFingerprint())) {
         toWrite.add(kr);
       }
     }
     if (toWrite.size() == existing.size()) {
       return;
     }

     ObjectId keyObjectId = keyObjectId(keyId);
     if (!toWrite.isEmpty()) {
       notes.set(keyObjectId, ins.insert(OBJ_BLOB, keysToArmored(toWrite)));
     } else {
       PGPPublicKeyRing keyRing = get(fp.get());

       for (PGPPublicKey key : keyRing) {
         long subKeyId = key.getKeyID();
         // Skip master public key
         if (keyId == subKeyId) {
           continue;
         }
         notes.remove(keyObjectId(subKeyId));
       }

       notes.remove(keyObjectId);
     }
   }

   private static boolean sameKey(PGPPublicKeyRing kr1, PGPPublicKeyRing kr2) {
     return Arrays.equals(kr1.getPublicKey().getFingerprint(), kr2.getPublicKey().getFingerprint());
   }

   private static byte[] keysToArmored(List<PGPPublicKeyRing> keys) throws IOException {
     ByteArrayOutputStream out = new ByteArrayOutputStream(4096 * keys.size());
     for (PGPPublicKeyRing kr : keys) {
       try (ArmoredOutputStream aout = new ArmoredOutputStream(out)) {
         kr.encode(aout);
       }
     }
     return out.toByteArray();
   }

   public static String keyToString(PGPPublicKey key) {
     Iterator<String> it = key.getUserIDs();
     return String.format(
         "%s %s(%s)",
         keyIdToString(key.getKeyID()),
         it.hasNext() ? it.next() + " " : "",
         Fingerprint.toString(key.getFingerprint()));
   }

   public static String keyIdToString(long keyId) {
     // Match key ID format from gpg --list-keys.
     return String.format("%08X", (int) keyId);
   }

   static ObjectId keyObjectId(long keyId) {
     byte[] buf = new byte[ObjectIds.LEN];
     NB.encodeInt64(buf, 0, keyId);
     return ObjectId.fromRaw(buf);
   }
 }
	// Copyright (C) 2015 The Android Open Source Project
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	package com.google.gerrit.gpg;

	import static com.google.common.base.Preconditions.checkState;
	import static com.google.gerrit.server.update.context.RefUpdateContext.RefUpdateType.GPG_KEYS_MODIFICATION;
	import static java.nio.charset.StandardCharsets.UTF_8;
	import static org.eclipse.jgit.lib.Constants.EMPTY_TREE_ID;
	import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;

	import com.google.common.base.Preconditions;
	import com.google.common.io.ByteStreams;
	import com.google.gerrit.common.Nullable;
	import com.google.gerrit.git.LockFailureException;
	import com.google.gerrit.git.ObjectIds;
	import com.google.gerrit.server.update.context.RefUpdateContext;
	import java.io.ByteArrayInputStream;
	import java.io.ByteArrayOutputStream;
	import java.io.IOException;
	import java.io.InputStream;
	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.Collections;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Map;
	import java.util.Set;
	import org.bouncycastle.bcpg.ArmoredInputStream;
	import org.bouncycastle.bcpg.ArmoredOutputStream;
	import org.bouncycastle.openpgp.PGPException;
	import org.bouncycastle.openpgp.PGPPublicKey;
	import org.bouncycastle.openpgp.PGPPublicKeyRing;
	import org.bouncycastle.openpgp.PGPPublicKeyRingCollection;
	import org.bouncycastle.openpgp.PGPSignature;
	import org.bouncycastle.openpgp.bc.BcPGPObjectFactory;
	import org.bouncycastle.openpgp.operator.bc.BcPGPContentVerifierBuilderProvider;
	import org.eclipse.jgit.errors.IncorrectObjectTypeException;
	import org.eclipse.jgit.errors.MissingObjectException;
	import org.eclipse.jgit.lib.CommitBuilder;
	import org.eclipse.jgit.lib.ObjectId;
	import org.eclipse.jgit.lib.ObjectInserter;
	import org.eclipse.jgit.lib.ObjectReader;
	import org.eclipse.jgit.lib.Ref;
	import org.eclipse.jgit.lib.RefUpdate;
	import org.eclipse.jgit.lib.Repository;
	import org.eclipse.jgit.notes.Note;
	import org.eclipse.jgit.notes.NoteMap;
	import org.eclipse.jgit.revwalk.RevCommit;
	import org.eclipse.jgit.revwalk.RevWalk;
	import org.eclipse.jgit.util.NB;

	/**
	* Store of GPG public keys in git notes.
	*
	* <p>Keys are stored in filenames based on their hex key ID, padded out to 40 characters to match
	* the length of a SHA-1. (This is to easily reuse existing fanout code in {@link NoteMap}, and may
	* be changed later after an appropriate transition.)
	*
	* <p>The contents of each file is an ASCII armored stream containing one or more public key rings
	* matching the ID. Multiple keys are supported because forging a key ID is possible, but such a key
	* cannot be used to verify signatures produced with the correct key.
	*
	* <p>Subkeys are mapped to the master GPG key in the same NoteMap.
	*
	* <p>No additional checks are performed on the key after reading; callers should only trust keys
	* after checking with a {@link PublicKeyChecker}.
	*/
	public class PublicKeyStore implements AutoCloseable {
	/** Ref where GPG public keys are stored. */
	public static final String REFS_GPG_KEYS = "refs/meta/gpg-keys";

	/**
	* Choose the public key that produced a signature.
	*
	* <p>
	*
	* @param keyRings candidate keys.
	* @param sig signature object.
	* @param data signed payload.
	* @return the key chosen from {@code keyRings} that was able to verify the signature, or {@code
	* null} if none was found.
	* @throws PGPException if an error occurred verifying the signature.
	*/
	@Nullable
	public static PGPPublicKey getSigner(
	Iterable<PGPPublicKeyRing> keyRings, PGPSignature sig, byte[] data) throws PGPException {
	for (PGPPublicKeyRing kr : keyRings) {
	// Possibly return a signing subkey in case it differs from the master public key
	PGPPublicKey k = kr.getPublicKey(sig.getKeyID());
	if (k == null) {
	throw new IllegalStateException(
	"No public key found for ID: " + keyIdToString(sig.getKeyID()));
	}
	sig.init(new BcPGPContentVerifierBuilderProvider(), k);
	sig.update(data);
	if (sig.verify()) {
	// If the signature was made using a subkey, return the main public key.
	// This enables further validity checks, like user ID checks, that can only
	// be performed using the master public key.
	return kr.getPublicKey();
	}
	}
	return null;
	}

	/**
	* Choose the public key that produced a certification.
	*
	* <p>
	*
	* @param keyRings candidate keys.
	* @param sig signature object.
	* @param userId user ID being certified.
	* @param key key being certified.
	* @return the key chosen from {@code keyRings} that was able to verify the certification, or
	* {@code null} if none was found.
	* @throws PGPException if an error occurred verifying the certification.
	*/
	@Nullable
	public static PGPPublicKey getSigner(
	Iterable<PGPPublicKeyRing> keyRings, PGPSignature sig, String userId, PGPPublicKey key)
	throws PGPException {
	for (PGPPublicKeyRing kr : keyRings) {
	PGPPublicKey k = kr.getPublicKey();
	sig.init(new BcPGPContentVerifierBuilderProvider(), k);
	if (sig.verifyCertification(userId, key)) {
	return k;
	}
	}
	return null;
	}

	private final Repository repo;
	private ObjectReader reader;
	private RevCommit tip;
	private NoteMap notes;
	private Map<Fingerprint, PGPPublicKeyRing> toAdd;
	private Set<Fingerprint> toRemove;

	/** @param repo repository to read keys from. */
	public PublicKeyStore(Repository repo) {
	this.repo = repo;
	toAdd = new HashMap<>();
	toRemove = new HashSet<>();
	}

	@Override
	public void close() {
	reset();
	}

	private void reset() {
	if (reader != null) {
	reader.close();
	reader = null;
	notes = null;
	}
	}

	private void load() throws IOException {
	reset();
	reader = repo.newObjectReader();

	Ref ref = repo.getRefDatabase().exactRef(REFS_GPG_KEYS);
	if (ref == null) {
	return;
	}
	try (RevWalk rw = new RevWalk(reader)) {
	tip = rw.parseCommit(ref.getObjectId());
	notes = NoteMap.read(reader, tip);
	}
	}

	/**
	* Read public keys with the given key ID.
	*
	* <p>Keys should not be trusted unless checked with {@link PublicKeyChecker}.
	*
	* <p>Multiple calls to this method use the same state of the key ref; to reread the ref, call
	* {@link #close()} first.
	*
	* @param keyId key ID.
	* @return any keys found that could be successfully parsed.
	* @throws PGPException if an error occurred parsing the key data.
	* @throws IOException if an error occurred reading the repository data.
	*/
	public PGPPublicKeyRingCollection get(long keyId) throws PGPException, IOException {
	return new PGPPublicKeyRingCollection(get(keyId, null));
	}

	/**
	* Read public key with the given fingerprint.
	*
	* <p>Keys should not be trusted unless checked with {@link PublicKeyChecker}.
	*
	* <p>Multiple calls to this method use the same state of the key ref; to reread the ref, call
	* {@link #close()} first.
	*
	* @param fingerprint key fingerprint.
	* @return the key if found, or {@code null}.
	* @throws PGPException if an error occurred parsing the key data.
	* @throws IOException if an error occurred reading the repository data.
	*/
	@Nullable
	public PGPPublicKeyRing get(byte[] fingerprint) throws PGPException, IOException {
	List<PGPPublicKeyRing> keyRings = get(Fingerprint.getId(fingerprint), fingerprint);
	return !keyRings.isEmpty() ? keyRings.get(0) : null;
	}

	private List<PGPPublicKeyRing> get(long keyId, byte[] fp) throws IOException {
	if (reader == null) {
	load();
	}
	if (notes == null) {
	return Collections.emptyList();
	}

	return get(keyObjectId(keyId), fp);
	}

	private List<PGPPublicKeyRing> get(ObjectId keyObjectId, byte[] fp) throws IOException {
	Note note = notes.getNote(keyObjectId);
	if (note == null) {
	return Collections.emptyList();
	}

	return readKeysFromNote(note, fp);
	}

	private List<PGPPublicKeyRing> readKeysFromNote(Note note, byte[] fp)
	throws IOException, MissingObjectException, IncorrectObjectTypeException {
	boolean foundAtLeastOneKey = false;
	List<PGPPublicKeyRing> keys = new ArrayList<>();
	ObjectId data = note.getData();
	try (InputStream stream = reader.open(data, OBJ_BLOB).openStream()) {
	byte[] bytes = ByteStreams.toByteArray(stream);
	InputStream in = new ByteArrayInputStream(bytes);
	while (true) {
	@SuppressWarnings("unchecked")
	Iterator<Object> it = new BcPGPObjectFactory(new ArmoredInputStream(in)).iterator();
	if (!it.hasNext()) {
	break;
	}
	foundAtLeastOneKey = true;
	Object obj = it.next();
	if (obj instanceof PGPPublicKeyRing) {
	PGPPublicKeyRing kr = (PGPPublicKeyRing) obj;
	if (fp == null \|\| Arrays.equals(fp, kr.getPublicKey().getFingerprint())) {
	keys.add(kr);
	}
	}
	checkState(!it.hasNext(), "expected one PGP object per ArmoredInputStream");
	}

	if (foundAtLeastOneKey) {
	return keys;
	}

	// Subkey handling
	String id = new String(bytes, UTF_8);
	Preconditions.checkArgument(ObjectId.isId(id), "Not valid SHA1: " + id);
	return get(ObjectId.fromString(id), fp);
	}
	}

	public void rebuildSubkeyMasterKeyMap()
	throws MissingObjectException, IncorrectObjectTypeException, IOException {
	if (reader == null) {
	load();
	}
	if (notes != null) {
	try (ObjectInserter ins = repo.newObjectInserter()) {
	for (Note note : notes) {
	for (PGPPublicKeyRing keyRing :
	new PGPPublicKeyRingCollection(readKeysFromNote(note, null))) {
	long masterKeyId = keyRing.getPublicKey().getKeyID();
	ObjectId masterKeyObjectId = keyObjectId(masterKeyId);
	saveSubkeyMapping(ins, keyRing, masterKeyId, masterKeyObjectId);
	}
	}
	}
	}
	}

	/**
	* Add a public key to the store.
	*
	* <p>Multiple calls may be made to buffer keys in memory, and they are not saved until {@link
	* #save(CommitBuilder)} is called.
	*
	* @param keyRing a key ring containing exactly one public master key.
	*/
	public void add(PGPPublicKeyRing keyRing) {
	int numMaster = 0;
	for (PGPPublicKey key : keyRing) {
	if (key.isMasterKey()) {
	numMaster++;
	}
	}
	// We could have an additional sanity check to ensure all subkeys belong to
	// this master key, but that requires doing actual signature verification
	// here. The alternative is insane but harmless.
	if (numMaster != 1) {
	throw new IllegalArgumentException("Exactly 1 master key is required, found " + numMaster);
	}
	Fingerprint fp = new Fingerprint(keyRing.getPublicKey().getFingerprint());
	toAdd.put(fp, keyRing);
	toRemove.remove(fp);
	}

	/**
	* Remove a public key from the store.
	*
	* <p>Multiple calls may be made to buffer deletes in memory, and they are not saved until {@link
	* #save(CommitBuilder)} is called.
	*
	* @param fingerprint the fingerprint of the key to remove.
	*/
	public void remove(byte[] fingerprint) {
	Fingerprint fp = new Fingerprint(fingerprint);
	toAdd.remove(fp);
	toRemove.add(fp);
	}

	/**
	* Save pending keys to the store.
	*
	* <p>One commit is created and the ref updated. The pending list is cleared if and only if the
	* ref update succeeds, which allows for easy retries in case of lock failure.
	*
	* @param cb commit builder with at least author and identity populated; tree and parent are
	* ignored.
	* @return result of the ref update.
	*/
	public RefUpdate.Result save(CommitBuilder cb) throws PGPException, IOException {
	if (toAdd.isEmpty() && toRemove.isEmpty()) {
	return RefUpdate.Result.NO_CHANGE;
	}
	if (reader == null) {
	load();
	}
	if (notes == null) {
	notes = NoteMap.newEmptyMap();
	}
	ObjectId newTip;
	try (ObjectInserter ins = repo.newObjectInserter()) {
	for (PGPPublicKeyRing keyRing : toAdd.values()) {
	saveToNotes(ins, keyRing);
	}
	for (Fingerprint fp : toRemove) {
	deleteFromNotes(ins, fp);
	}
	cb.setTreeId(notes.writeTree(ins));
	if (cb.getTreeId().equals(tip != null ? tip.getTree() : EMPTY_TREE_ID)) {
	return RefUpdate.Result.NO_CHANGE;
	}

	if (tip != null) {
	cb.setParentId(tip);
	}
	if (cb.getMessage() == null) {
	int n = toAdd.size() + toRemove.size();
	cb.setMessage(String.format("Update %d public key%s", n, n != 1 ? "s" : ""));
	}
	newTip = ins.insert(cb);
	ins.flush();
	}
	try (RefUpdateContext ctx = RefUpdateContext.open(GPG_KEYS_MODIFICATION)) {
	RefUpdate ru = repo.updateRef(PublicKeyStore.REFS_GPG_KEYS);
	ru.setExpectedOldObjectId(tip);
	ru.setNewObjectId(newTip);
	ru.setRefLogIdent(cb.getCommitter());
	ru.setRefLogMessage("Store public keys", true);
	RefUpdate.Result result = ru.update();
	reset();
	switch (result) {
	case FAST_FORWARD:
	case NEW:
	case NO_CHANGE:
	toAdd.clear();
	toRemove.clear();
	break;
	case LOCK_FAILURE:
	throw new LockFailureException("Failed to store public keys", ru);
	case FORCED:
	case IO_FAILURE:
	case NOT_ATTEMPTED:
	case REJECTED:
	case REJECTED_CURRENT_BRANCH:
	case RENAMED:
	case REJECTED_MISSING_OBJECT:
	case REJECTED_OTHER_REASON:
	default:
	break;
	}
	return result;
	}
	}

	private void saveToNotes(ObjectInserter ins, PGPPublicKeyRing keyRing)
	throws PGPException, IOException {
	long masterKeyId = keyRing.getPublicKey().getKeyID();
	PGPPublicKeyRingCollection existing = get(masterKeyId);
	List<PGPPublicKeyRing> toWrite = new ArrayList<>(existing.size() + 1);
	boolean replaced = false;
	for (PGPPublicKeyRing kr : existing) {
	if (sameKey(keyRing, kr)) {
	toWrite.add(keyRing);
	replaced = true;
	} else {
	toWrite.add(kr);
	}
	}
	if (!replaced) {
	toWrite.add(keyRing);
	}

	ObjectId masterKeyObjectId = keyObjectId(masterKeyId);
	notes.set(masterKeyObjectId, ins.insert(OBJ_BLOB, keysToArmored(toWrite)));

	saveSubkeyMapping(ins, keyRing, masterKeyId, masterKeyObjectId);
	}

	private void saveSubkeyMapping(
	ObjectInserter ins, PGPPublicKeyRing keyRing, long masterKeyId, ObjectId masterKeyObjectId)
	throws IOException {
	// Subkey handling
	byte[] masterKeyBytes = masterKeyObjectId.name().getBytes(UTF_8);
	ObjectId masterKeyObject = null;
	for (PGPPublicKey key : keyRing) {
	long subKeyId = key.getKeyID();
	// Skip master public key
	if (masterKeyId == subKeyId) {
	continue;
	}

	// Insert master key object only once for all subkeys
	if (masterKeyObject == null) {
	masterKeyObject = ins.insert(OBJ_BLOB, masterKeyBytes);
	}

	ObjectId subkeyObjectId = keyObjectId(subKeyId);
	Preconditions.checkArgument(
	notes.get(subkeyObjectId) == null \|\| notes.get(subkeyObjectId).equals(masterKeyObject),
	"Master key differs for subkey: " + subkeyObjectId.name());
	notes.set(subkeyObjectId, masterKeyObject);
	}
	}

	private void deleteFromNotes(ObjectInserter ins, Fingerprint fp)
	throws PGPException, IOException {
	long keyId = fp.getId();
	PGPPublicKeyRingCollection existing = get(keyId);
	List<PGPPublicKeyRing> toWrite = new ArrayList<>(existing.size());
	for (PGPPublicKeyRing kr : existing) {
	if (!fp.equalsBytes(kr.getPublicKey().getFingerprint())) {
	toWrite.add(kr);
	}
	}
	if (toWrite.size() == existing.size()) {
	return;
	}

	ObjectId keyObjectId = keyObjectId(keyId);
	if (!toWrite.isEmpty()) {
	notes.set(keyObjectId, ins.insert(OBJ_BLOB, keysToArmored(toWrite)));
	} else {
	PGPPublicKeyRing keyRing = get(fp.get());

	for (PGPPublicKey key : keyRing) {
	long subKeyId = key.getKeyID();
	// Skip master public key
	if (keyId == subKeyId) {
	continue;
	}
	notes.remove(keyObjectId(subKeyId));
	}

	notes.remove(keyObjectId);
	}
	}

	private static boolean sameKey(PGPPublicKeyRing kr1, PGPPublicKeyRing kr2) {
	return Arrays.equals(kr1.getPublicKey().getFingerprint(), kr2.getPublicKey().getFingerprint());
	}

	private static byte[] keysToArmored(List<PGPPublicKeyRing> keys) throws IOException {
	ByteArrayOutputStream out = new ByteArrayOutputStream(4096 * keys.size());
	for (PGPPublicKeyRing kr : keys) {
	try (ArmoredOutputStream aout = new ArmoredOutputStream(out)) {
	kr.encode(aout);
	}
	}
	return out.toByteArray();
	}

	public static String keyToString(PGPPublicKey key) {
	Iterator<String> it = key.getUserIDs();
	return String.format(
	"%s %s(%s)",
	keyIdToString(key.getKeyID()),
	it.hasNext() ? it.next() + " " : "",
	Fingerprint.toString(key.getFingerprint()));
	}

	public static String keyIdToString(long keyId) {
	// Match key ID format from gpg --list-keys.
	return String.format("%08X", (int) keyId);
	}

	static ObjectId keyObjectId(long keyId) {
	byte[] buf = new byte[ObjectIds.LEN];
	NB.encodeInt64(buf, 0, keyId);
	return ObjectId.fromRaw(buf);
	}
	}