Fix ECDH fingerprint size of v6 keys (#1771)

Fingerprint should not be truncated, unlike for v5 keys.

src/crypto/public_key/elliptic/ecdh.js

@@ -53,7 +53,7 @@ function buildEcdhParam(public_algo, oid, kdfParams, fingerprint) {
     new Uint8Array([public_algo]),
     kdfParams.write(),
     util.stringToUint8Array('Anonymous Sender    '),
-    fingerprint.subarray(0, 20)
+    fingerprint
   ]);
 }
 
@@ -123,7 +123,7 @@ async function genPublicEphemeralKey(curve, Q) {
  * @param {module:type/kdf_params} kdfParams - KDF params including cipher and algorithm to use
  * @param {Uint8Array} data - Unpadded session key data
  * @param {Uint8Array} Q - Recipient public key
- * @param {Uint8Array} fingerprint - Recipient fingerprint
+ * @param {Uint8Array} fingerprint - Recipient fingerprint, already truncated depending on the key version
  * @returns {Promise<{publicKey: Uint8Array, wrappedKey: Uint8Array}>}
  * @async
  */
@@ -188,7 +188,7 @@ async function genPrivateEphemeralKey(curve, V, Q, d) {
  * @param {Uint8Array} C - Encrypted and wrapped value derived from session key
  * @param {Uint8Array} Q - Recipient public key
  * @param {Uint8Array} d - Recipient private key
- * @param {Uint8Array} fingerprint - Recipient fingerprint
+ * @param {Uint8Array} fingerprint - Recipient fingerprint, already truncated depending on the key version
  * @returns {Promise<Uint8Array>} Value derived from session key.
  * @async
  */

src/packet/public_key_encrypted_session_key.js

@@ -180,9 +180,10 @@ class PublicKeyEncryptedSessionKeyPacket {
     // No symmetric encryption algorithm identifier is passed to the public-key algorithm for a
     // v6 PKESK packet, as it is included in the v2 SEIPD packet.
     const sessionKeyAlgorithm = this.version === 3 ? this.sessionKeyAlgorithm : null;
+    const fingerprint = key.version === 5 ? key.getFingerprintBytes().subarray(0, 20) : key.getFingerprintBytes();
     const encoded = encodeSessionKey(this.version, algo, sessionKeyAlgorithm, this.sessionKey);
     this.encrypted = await crypto.publicKeyEncrypt(
-      algo, sessionKeyAlgorithm, key.publicParams, encoded, key.getFingerprintBytes());
+      algo, sessionKeyAlgorithm, key.publicParams, encoded, fingerprint);
   }
 
   /**
@@ -202,7 +203,8 @@ class PublicKeyEncryptedSessionKeyPacket {
     const randomPayload = randomSessionKey ?
       encodeSessionKey(this.version, this.publicKeyAlgorithm, randomSessionKey.sessionKeyAlgorithm, randomSessionKey.sessionKey) :
       null;
-    const decryptedData = await crypto.publicKeyDecrypt(this.publicKeyAlgorithm, key.publicParams, key.privateParams, this.encrypted, key.getFingerprintBytes(), randomPayload);
+    const fingerprint = key.version === 5 ? key.getFingerprintBytes().subarray(0, 20) : key.getFingerprintBytes();
+    const decryptedData = await crypto.publicKeyDecrypt(this.publicKeyAlgorithm, key.publicParams, key.privateParams, this.encrypted, fingerprint, randomPayload);
 
     const { sessionKey, sessionKeyAlgorithm } = decodeSessionKey(this.version, this.publicKeyAlgorithm, decryptedData, randomSessionKey);
 

test/general/ecc_nist.js

@@ -75,5 +75,44 @@ export default () => describe('Elliptic Curve Cryptography for NIST P-256,P-384,
     expect(await result.signatures[0].verified).to.be.true;
   });
 
+  it('should decrypt a message using the correct fingerprint size in the KDF (v6 key)', async function() {
+    // this test is to ensure the KDF function uses the correct fingerprint size (the fingerprint should not be truncated)
+    const key = await openpgp.readKey({
+      armoredKey: `-----BEGIN PGP PRIVATE KEY BLOCK-----
+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=
+-----END PGP PRIVATE KEY BLOCK-----`
+    });
+    const message = await openpgp.readMessage({
+      armoredMessage: `-----BEGIN PGP MESSAGE-----
+
+wX4DYKEfntV7jkcSAgMEXplJPwjsvhh7xNeBeZtgepG1f0hUaW4eoeFCDpYH
+IOr2RZFgRd6KbtmNsI1saqDwDg7EjFk+AWOe7av2xcFStTDfz+9mus03A6tk
+7mPFWGsDUrxP2b+tyO6ofr9I4gyj5tI2X7R94AfRWgQxy+O2PvLSNAFXcx4o
+SsrtSQmZUKpxuBROy+bZNheNgmN966vqnFBiM1vXikv5OVyprUV0EzzQ3Hnt
+69s=
+=0Agg
+-----END PGP MESSAGE-----`
+    });
+    const decrypted = await openpgp.decrypt({ message, decryptionKeys: key });
+    expect(decrypted.data).to.equal('abc');
+  });
+
+
   // TODO find test vectors
 });