Add SSH certificate authentication support

lib/client.js

@@ -33,7 +33,7 @@ const {
 } = require('./protocol/constants.js');
 const { init: cryptoInit } = require('./protocol/crypto.js');
 const Protocol = require('./protocol/Protocol.js');
-const { parseKey } = require('./protocol/keyParser.js');
+const { isParsedKey, parseKey } = require('./protocol/keyParser.js');
 const { SFTP } = require('./protocol/SFTP.js');
 const {
   bufferCopy,
@@ -207,8 +207,16 @@ class Client extends EventEmitter {
                             : undefined);
     this.config.privateKey = (typeof cfg.privateKey === 'string'
                               || Buffer.isBuffer(cfg.privateKey)
+                              || isParsedKey(cfg.privateKey)
                               ? cfg.privateKey
                               : undefined);
+    // publicKey may be a certificate file (e.g. id_ed25519-cert.pub) to use
+    // for identification while privateKey is used for signing.
+    this.config.publicKey = (typeof cfg.publicKey === 'string'
+                             || Buffer.isBuffer(cfg.publicKey)
+                             || isParsedKey(cfg.publicKey)
+                             ? cfg.publicKey
+                             : undefined);
     this.config.localHostname = (typeof cfg.localHostname === 'string'
                                  ? cfg.localHostname
                                  : undefined);
@@ -254,6 +262,7 @@ class Client extends EventEmitter {
     this._agent = (this.config.agent ? this.config.agent : undefined);
     this._remoteVer = undefined;
     let privateKey;
+    let authKey; // Key object used for publickey auth (may be a certificate)
 
     if (this.config.privateKey) {
       privateKey = parseKey(this.config.privateKey, cfg.passphrase);
@@ -268,6 +277,18 @@ class Client extends EventEmitter {
           'privateKey value does not contain a (valid) private key'
         );
       }
+
+      if (this.config.publicKey) {
+        // A separate certificate was provided for identification. Use it as
+        // the key sent to the server while privateKey is used for signing.
+        authKey = parseKey(this.config.publicKey);
+        if (authKey instanceof Error)
+          throw new Error(`Cannot parse publicKey: ${authKey.message}`);
+        if (Array.isArray(authKey))
+          authKey = authKey[0];
+      } else {
+        authKey = privateKey;
+      }
     }
 
     let hostVerifier;
@@ -462,7 +483,10 @@ class Client extends EventEmitter {
             });
           } else if (curAuth.type === 'publickey') {
             proto.authPK(curAuth.username, curAuth.key, keyAlgo, (buf, cb) => {
-              const signature = curAuth.key.sign(buf, hashAlgo);
+              // Sign with privateKey (may differ from curAuth.key when a
+              // certificate is used for identification).
+              const signingKey = curAuth.privateKey || curAuth.key;
+              const signature = signingKey.sign(buf, hashAlgo);
               if (signature instanceof Error) {
                 signature.message =
                   `Error signing data with key: ${signature.message}`;
@@ -882,13 +906,14 @@ class Client extends EventEmitter {
             nextAuth = { type, username, password: this.config.password };
             break;
           case 'publickey':
-            nextAuth = { type, username, key: privateKey };
+            nextAuth = { type, username, key: authKey, privateKey };
             break;
           case 'hostbased':
             nextAuth = {
               type,
               username,
-              key: privateKey,
+              key: authKey,
+              privateKey,
               localHostname: this.config.localHostname,
               localUsername: this.config.localUsername,
             };

lib/protocol/Protocol.js

@@ -648,6 +648,15 @@ class Protocol {
 
     const userLen = Buffer.byteLength(username);
     const algoLen = Buffer.byteLength(keyAlgo);
+    // OpenSSH certificates: the request's algorithm field names the certificate
+    // ("ssh-ed25519-cert-v01@openssh.com"), but the signature blob must name
+    // the plain algorithm the key actually signs with ("ssh-ed25519"). For
+    // plain keys the two are identical and nothing below changes.
+    const certSuffix = '-cert-v01@openssh.com';
+    const sigAlgo = keyAlgo.endsWith(certSuffix)
+      ? keyAlgo.slice(0, -certSuffix.length)
+      : keyAlgo;
+    const sigAlgoLen = Buffer.byteLength(sigAlgo);
     const pubKeyLen = pubKey.length;
     const sessionID = this._kex.sessionID;
     const sesLen = sessionID.length;
@@ -697,15 +706,15 @@ class Protocol {
     }
 
     cbSign(packet, (signature) => {
-      signature = convertSignature(signature, keyType);
+      signature = convertSignature(signature, sigAlgo);
       if (signature === false)
         throw new Error('Error while converting handshake signature');
 
       const sigLen = signature.length;
       p = this._packetRW.write.allocStart;
       packet = this._packetRW.write.alloc(
         1 + 4 + userLen + 4 + 14 + 4 + 9 + 1 + 4 + algoLen + 4 + pubKeyLen + 4
-          + 4 + algoLen + 4 + sigLen
+          + 4 + sigAlgoLen + 4 + sigLen
       );
 
       // TODO: simply copy from original "packet" to new `packet` to avoid
@@ -729,12 +738,12 @@ class Protocol {
       writeUInt32BE(packet, pubKeyLen, p += algoLen);
       packet.set(pubKey, p += 4);
 
-      writeUInt32BE(packet, 4 + algoLen + 4 + sigLen, p += pubKeyLen);
+      writeUInt32BE(packet, 4 + sigAlgoLen + 4 + sigLen, p += pubKeyLen);
 
-      writeUInt32BE(packet, algoLen, p += 4);
-      packet.utf8Write(keyAlgo, p += 4, algoLen);
+      writeUInt32BE(packet, sigAlgoLen, p += 4);
+      packet.utf8Write(sigAlgo, p += 4, sigAlgoLen);
 
-      writeUInt32BE(packet, sigLen, p += algoLen);
+      writeUInt32BE(packet, sigLen, p += sigAlgoLen);
       packet.set(signature, p += 4);
 
       // Servers shouldn't send packet type 60 in response to signed publickey

lib/protocol/keyParser.js

@@ -1186,6 +1186,21 @@ function OpenSSH_Public(type, comment, pubPEM, pubSSH, algo) {
   this[SYM_DECRYPTED] = false;
 }
 OpenSSH_Public.prototype = BaseKey;
+
+// Represents an SSH certificate (e.g. ssh-ed25519-cert-v01@openssh.com).
+// The full certificate blob is stored as-is and returned from getPublicSSH()
+// so it can be used directly in publickey auth requests.
+function Cert_Public(type, comment, certBlob) {
+  this.type = type;
+  this.comment = comment;
+  this[SYM_PRIV_PEM] = null;
+  this[SYM_PUB_PEM] = null;
+  this[SYM_PUB_SSH] = certBlob;
+  this[SYM_HASH_ALGO] = null;
+  this[SYM_DECRYPTED] = false;
+}
+Cert_Public.prototype = BaseKey;
+
 {
   let regexp;
   if (eddsaSupported)
@@ -1198,7 +1213,7 @@ OpenSSH_Public.prototype = BaseKey;
       return null;
     // m[1] = full type
     // m[2] = base type
-    // m[3] = base64-encoded public key
+    // m[3] = base64-encoded public key / certificate blob
     // m[4] = comment
 
     const fullType = m[1];
@@ -1210,6 +1225,15 @@ OpenSSH_Public.prototype = BaseKey;
     if (type === undefined || type.indexOf(baseType) !== 0)
       return new Error('Malformed OpenSSH public key');
 
+    // Certificate: preserve the full blob so getPublicSSH() returns it intact
+    // for use in SSH_MSG_USERAUTH_REQUEST publickey auth. The type sniff above
+    // left the parser's `_pos` cursor on `data`; it must not escape with the
+    // blob, where it would make two identical certificates compare unequal.
+    if (fullType !== baseType) {
+      delete data._pos;
+      return new Cert_Public(fullType, comment, data);
+    }
+
     return parseDER(data, baseType, comment, fullType);
   };
 }
@@ -1458,13 +1482,18 @@ function parseKey(data, passphrase) {
     binaryKeyParser.init(origBuffer, 0);
     const type = binaryKeyParser.readString(true);
     if (type !== undefined) {
-      data = binaryKeyParser.readRaw();
-      if (data !== undefined) {
-        ret = parseDER(data, type, '', type);
-        // Ignore potentially useless errors in case the data was not actually
-        // in the binary format
-        if (ret instanceof Error)
-          ret = null;
+      // Certificate blob: preserve it whole rather than parsing its internals
+      if (type.indexOf('-cert-v0') !== -1) {
+        ret = new Cert_Public(type, '', origBuffer);
+      } else {
+        data = binaryKeyParser.readRaw();
+        if (data !== undefined) {
+          ret = parseDER(data, type, '', type);
+          // Ignore potentially useless errors in case the data was not actually
+          // in the binary format
+          if (ret instanceof Error)
+            ret = null;
+        }
       }
     }
     binaryKeyParser.clear();
@@ -1478,6 +1507,7 @@ function parseKey(data, passphrase) {
 
 module.exports = {
   isParsedKey,
+  Cert_Public,
   isSupportedKeyType,
   parseDERKey: (data, type) => parseDER(data, type, '', type),
   parseKey,

test/fixtures/id_ecdsa_cert_key

@@ -0,0 +1,9 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAaAAAABNlY2RzYS
+1zaGEyLW5pc3RwMjU2AAAACG5pc3RwMjU2AAAAQQRmVDua5cBz9KzJqMt7Iur/wiJcvxGE
+OPSz26h0HA/QrZL58SnuNIPwNuNkRe3gD6OvVNIgY+0ugEoOtA2td1wZAAAAsEcVnTVHFZ
+01AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBGZUO5rlwHP0rMmo
+y3si6v/CIly/EYQ49LPbqHQcD9CtkvnxKe40g/A242RF7eAPo69U0iBj7S6ASg60Da13XB
+kAAAAgVNtyZE0ka1Uca8Doi9MK+zmnWLgrfVFWi0YMuHW8pSUAAAAWc3NoMiBjZXJ0IHRl
+c3QgKGVjZHNhKQEC
+-----END OPENSSH PRIVATE KEY-----

test/fixtures/id_ecdsa_cert_key-cert.pub

@@ -0,0 +1 @@
+ecdsa-sha2-nistp256-cert-v01@openssh.com AAAAKGVjZHNhLXNoYTItbmlzdHAyNTYtY2VydC12MDFAb3BlbnNzaC5jb20AAAAgTak0HL5RJH9zw9YlAF1gSZcxg1n4REuqJdW6pkkmVg0AAAAIbmlzdHAyNTYAAABBBGZUO5rlwHP0rMmoy3si6v/CIly/EYQ49LPbqHQcD9CtkvnxKe40g/A242RF7eAPo69U0iBj7S6ASg60Da13XBkAAAAAAAAAAAAAAAEAAAAPc3NoMi10ZXN0LWVjZHNhAAAADQAAAAlDZXJ0IFVzZXIAAAAAXgu20AAAAAGwne7QAAAAAAAAAIIAAAAVcGVybWl0LVgxMS1mb3J3YXJkaW5nAAAAAAAAABdwZXJtaXQtYWdlbnQtZm9yd2FyZGluZwAAAAAAAAAWcGVybWl0LXBvcnQtZm9yd2FyZGluZwAAAAAAAAAKcGVybWl0LXB0eQAAAAAAAAAOcGVybWl0LXVzZXItcmMAAAAAAAAAAAAAADMAAAALc3NoLWVkMjU1MTkAAAAg8pFFhI+jq1LhsqtKalxN4zigUFvWZFVIO5rW6WF+q80AAABTAAAAC3NzaC1lZDI1NTE5AAAAQPays/Qg1YOopt5YdWxA6vbkdxsjqzcGI+I0o421mvteSo2KiBmBCqFFMGaIoJz84AbsqSXEA4ceIw9RqB4+TwQ= ssh2 cert test (ecdsa)

test/fixtures/id_ecdsa_cert_key.pub

@@ -0,0 +1 @@
+ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBGZUO5rlwHP0rMmoy3si6v/CIly/EYQ49LPbqHQcD9CtkvnxKe40g/A242RF7eAPo69U0iBj7S6ASg60Da13XBk= ssh2 cert test (ecdsa)

test/fixtures/id_ed25519_cert_key

@@ -0,0 +1,7 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+QyNTUxOQAAACDi3+ww7F3/p3bj95kkS5a3l0bLSvqLwBusCn4ZCs1jxgAAAKCREaswkRGr
+MAAAAAtzc2gtZWQyNTUxOQAAACDi3+ww7F3/p3bj95kkS5a3l0bLSvqLwBusCn4ZCs1jxg
+AAAEAbGT1n6QEvc47JS9PWzdz11zGRKyiB8cDVivKsr+bz7uLf7DDsXf+nduP3mSRLlreX
+RstK+ovAG6wKfhkKzWPGAAAAGHNzaDIgY2VydCB0ZXN0IChlZDI1NTE5KQECAwQF
+-----END OPENSSH PRIVATE KEY-----

test/fixtures/id_ed25519_cert_key-cert.pub

@@ -0,0 +1 @@
+ssh-ed25519-cert-v01@openssh.com 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 ssh2 cert test (ed25519)

test/fixtures/id_ed25519_cert_key.pub

@@ -0,0 +1 @@
+ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOLf7DDsXf+nduP3mSRLlreXRstK+ovAG6wKfhkKzWPG ssh2 cert test (ed25519)

test/fixtures/id_rsa_cert_key

@@ -0,0 +1,27 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAABFwAAAAdzc2gtcn
+NhAAAAAwEAAQAAAQEA2ee/j51zvZRGtIqTz4giqpdfc0mhOIuE3mvEYR4XOCxCBPUdN3Pn
+WNpkhlw26uLdqkOP96eRHn5Vv4roj33soHIT5fJ2sJ0s7NmiIpkRBhDe1cmafm4vFZidex
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+rTh5umYM9AVT6JqERsOQGadW/fHwaBauUJ2Lnos8r9/v81ZDOH8KJW4dLqWUTvE22AcAGf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+-----END OPENSSH PRIVATE KEY-----

test/fixtures/id_rsa_cert_key-cert.pub

@@ -0,0 +1 @@
+ssh-rsa-cert-v01@openssh.com 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 ssh2 cert test (rsa)

test/fixtures/id_rsa_cert_key.pub

@@ -0,0 +1 @@
+ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDZ57+PnXO9lEa0ipPPiCKql19zSaE4i4Tea8RhHhc4LEIE9R03c+dY2mSGXDbq4t2qQ4/3p5EeflW/iuiPfeygchPl8nawnSzs2aIimREGEN7VyZp+bi8VmJ17H/1ezJtrgkun4h7ILYYD/eoufkOgWckicODL6O9jqdsIbJoX1kVJpo1oX35Ms3WrI/nWy9+tOHm6Zgz0BVPomoRGw5AZp1b98fBoFq5QnYueizyv3+/zVkM4fwolbh0upZRO8TbYBwAZ8Dou4xQGYzTUXOi9hDTU3XnyeLMLNLUnIEfbi833yll79+3SeluZfDzqDQ4LL1lRObJth3u5HGYmtesZ ssh2 cert test (rsa)

test/fixtures/ssh_user_ca

@@ -0,0 +1,7 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+QyNTUxOQAAACDykUWEj6OrUuGyq0pqXE3jOKBQW9ZkVUg7mtbpYX6rzQAAAJCLILSGiyC0
+hgAAAAtzc2gtZWQyNTUxOQAAACDykUWEj6OrUuGyq0pqXE3jOKBQW9ZkVUg7mtbpYX6rzQ
+AAAECxVlsIUGiJCdmvEtE2z2+cPi/ChWjf8gSfOHcCm8JYU/KRRYSPo6tS4bKrSmpcTeM4
+oFBb1mRVSDua1ulhfqvNAAAADHNzaDIgdGVzdCBDQQE=
+-----END OPENSSH PRIVATE KEY-----

test/fixtures/ssh_user_ca.pub

@@ -0,0 +1 @@
+ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPKRRYSPo6tS4bKrSmpcTeM4oFBb1mRVSDua1ulhfqvN ssh2 test CA