add support for detached signatures

src/encoding/armor.js

@@ -62,10 +62,7 @@ function getType(text) {
     return enums.armor.multipart_last;
 
   } else
-  // BEGIN PGP SIGNATURE
-  // Used for detached signatures, OpenPGP/MIME signatures, and
-  // cleartext signatures. Note that PGP 2.x uses BEGIN PGP MESSAGE
-  // for detached signatures.
+  // BEGIN PGP SIGNED MESSAGE
   if (/SIGNED MESSAGE/.test(header[1])) {
     return enums.armor.signed;
 
@@ -86,6 +83,14 @@ function getType(text) {
   // Used for armoring private keys.
   if (/PRIVATE KEY BLOCK/.test(header[1])) {
     return enums.armor.private_key;
+
+  } else
+  // BEGIN PGP SIGNATURE
+  // Used for detached signatures, OpenPGP/MIME signatures, and
+  // cleartext signatures. Note that PGP 2.x uses BEGIN PGP MESSAGE
+  // for detached signatures.
+  if (/SIGNATURE/.test(header[1])) {
+    return enums.armor.signature;
   }
 }
 
@@ -397,6 +402,13 @@ function armor(messagetype, body, partindex, parttotal) {
       result.push("\r\n=" + getCheckSum(body) + "\r\n");
       result.push("-----END PGP PRIVATE KEY BLOCK-----\r\n");
       break;
+    case enums.armor.signature:
+      result.push("-----BEGIN PGP SIGNATURE-----\r\n");
+      result.push(addheader());
+      result.push(base64.encode(body));
+      result.push("\r\n=" + getCheckSum(body) + "\r\n");
+      result.push("-----END PGP SIGNATURE-----\r\n");
+      break;
   }
 
   return result.join('');

src/enums.js

@@ -297,7 +297,8 @@ export default {
     signed: 2,
     message: 3,
     public_key: 4,
-    private_key: 5
+    private_key: 5,
+    signature: 6
   },
 
   /** Asserts validity and converts from string/integer to integer. */

src/message.js

@@ -32,6 +32,7 @@ import enums from './enums.js';
 import armor from './encoding/armor.js';
 import config from './config';
 import crypto from './crypto';
+import signature from './signature.js';
 import * as keyModule from './key.js';
 
 /**
@@ -344,19 +345,81 @@ Message.prototype.sign = function(privateKeys) {
   return new Message(packetlist);
 };
 
+/**
+ * Create a detached signature for the message (the literal data packet of the message)
+ * @param  {Array<module:key~Key>} privateKey private keys with decrypted secret key data for signing
+ * @return {module:signature~Signature}      new detached signature of message content
+ */
+Message.prototype.signDetached = function(privateKeys) {
+
+  var packetlist = new packet.List();
+
+  var literalDataPacket = this.packets.findPacket(enums.packet.literal);
+  if (!literalDataPacket) {
+    throw new Error('No literal data packet to sign.');
+  }
+
+  var literalFormat = enums.write(enums.literal, literalDataPacket.format);
+  var signatureType = literalFormat === enums.literal.binary ?
+                      enums.signature.binary : enums.signature.text;
+
+  for (var i = 0; i < privateKeys.length; i++) {
+    var signingKeyPacket = privateKeys[i].getSigningKeyPacket();
+    var signaturePacket = new packet.Signature();
+    signaturePacket.signatureType = signatureType;
+    signaturePacket.hashAlgorithm = config.prefer_hash_algorithm;
+    signaturePacket.publicKeyAlgorithm = signingKeyPacket.algorithm;
+    if (!signingKeyPacket.isDecrypted) {
+      throw new Error('Private key is not decrypted.');
+    }
+    signaturePacket.sign(signingKeyPacket, literalDataPacket);
+    packetlist.push(signaturePacket);
+  }
+
+  return new signature.Signature(packetlist);
+};
+
+
 /**
  * Verify message signatures
  * @param {Array<module:key~Key>} keys array of keys to verify signatures
  * @return {Array<({keyid: module:type/keyid, valid: Boolean})>} list of signer's keyid and validity of signature
  */
 Message.prototype.verify = function(keys) {
-  var result = [];
   var msg = this.unwrapCompressed();
   var literalDataList = msg.packets.filterByTag(enums.packet.literal);
   if (literalDataList.length !== 1) {
     throw new Error('Can only verify message with one literal data packet.');
   }
   var signatureList = msg.packets.filterByTag(enums.packet.signature);
+  return createVerificationObjects(signatureList, literalDataList, keys);
+};
+
+/**
+ * Verify detached message signature
+ * @param {Array<module:key~Key>} keys array of keys to verify signatures
+ * @param {Signature}
+ * @return {Array<({keyid: module:type/keyid, valid: Boolean})>} list of signer's keyid and validity of signature
+ */
+Message.prototype.verifyDetached = function(signature, keys) {
+  var msg = this.unwrapCompressed();
+  var literalDataList = msg.packets.filterByTag(enums.packet.literal);
+  if (literalDataList.length !== 1) {
+    throw new Error('Can only verify message with one literal data packet.');
+  }
+  var signatureList = signature.packets;
+  return createVerificationObjects(signatureList, literalDataList, keys);
+};
+
+/**
+ * Create list of objects containing signer's keyid and validity of signature
+ * @param {Array<module:packet/signature>} signatureList array of signature packets
+ * @param {Array<module:packet/literal>} literalDataList array of literal data packets
+ * @param {Array<module:key~Key>} keys array of keys to verify signatures
+ * @return {Array<({keyid: module:type/keyid, valid: Boolean})>} list of signer's keyid and validity of signature
+ */
+function createVerificationObjects(signatureList, literalDataList, keys) {
+  var result = [];
   for (var i = 0; i < signatureList.length; i++) {
     var keyPacket = null;
     for (var j = 0; j < keys.length; j++) {
@@ -377,7 +440,7 @@ Message.prototype.verify = function(keys) {
     result.push(verifiedSig);
   }
   return result;
-};
+}
 
 /**
  * Unwrap compressed message

src/signature.js

@@ -0,0 +1,78 @@
+// GPG4Browsers - An OpenPGP implementation in javascript
+// Copyright (C) 2011 Recurity Labs GmbH
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 3.0 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+/**
+ * @requires config
+ * @requires crypto
+ * @requires encoding/armor
+ * @requires enums
+ * @requires packet
+ * @module signature
+ */
+
+'use strict';
+
+import packet from './packet';
+import enums from './enums.js';
+import armor from './encoding/armor.js';
+
+/**
+ * @class
+ * @classdesc Class that represents an OpenPGP message.
+ * Can be an encrypted message, signed message, compressed message or literal message
+ * @param  {module:packet/packetlist} packetlist The packets that form this message
+ * See {@link http://tools.ietf.org/html/rfc4880#section-11.3}
+ */
+
+export function Signature(packetlist) {
+  if (!(this instanceof Signature)) {
+    return new Signature(packetlist);
+  }
+  this.packets = packetlist || new packet.List();
+}
+
+
+/**
+ * Returns ASCII armored text of signature
+ * @return {String} ASCII armor
+ */
+Signature.prototype.armor = function() {
+  return armor.encode(enums.armor.signature, this.packets.write());
+};
+
+/**
+ * reads an OpenPGP armored signature and returns a signature object
+ * @param {String} armoredText text to be parsed
+ * @return {module:signature~Signature} new signature object
+ * @static
+ */
+export function readArmored(armoredText) {
+  var input = armor.decode(armoredText).data;
+  return read(input);
+}
+
+/**
+ * reads an OpenPGP signature as byte array and returns a signature object
+ * @param {Uint8Array} input   binary signature
+ * @return {Signature}         new signature object
+ * @static
+ */
+export function read(input) {
+  var packetlist = new packet.List();
+  packetlist.read(input);
+  return new Signature(packetlist);
+}