added rsa-sha-xxx key sig support

Author: Eugeny

lib/client.js

@@ -402,7 +402,17 @@ class Client extends EventEmitter {
             });
           } else if (curAuth.type === 'publickey') {
             proto.authPK(curAuth.username, curAuth.key, (buf, cb) => {
-              const signature = curAuth.key.sign(buf);
+              let signatureAlgo;
+              if (curAuth.key.type === 'ssh-rsa') {
+                if (this._protocol._remoteHostKeyAlgorithms
+                    .includes('rsa-sha2-512')) {
+                  signatureAlgo = 'sha512';
+                } else if (this._protocol._remoteHostKeyAlgorithms
+                    .includes('rsa-sha2-256')) {
+                  signatureAlgo = 'sha256';
+                }
+              }
+              const signature = curAuth.key.sign(buf, signatureAlgo);
               if (signature instanceof Error) {
                 signature.message =
                   `Error signing data with key: ${signature.message}`;

lib/protocol/Protocol.js

@@ -616,7 +616,16 @@ class Protocol {
     if (pubKey instanceof Error)
       throw new Error('Invalid key');
 
-    const keyType = pubKey.type;
+    let keyType = pubKey.type;
+    if (keyType === 'ssh-rsa') {
+      for (const algo of ['rsa-sha2-512', 'rsa-sha2-256']) {
+        if (this._remoteHostKeyAlgorithms.includes(algo)) {
+         keyType = algo;
+         break;
+        }
+      }
+    }
+
     pubKey = pubKey.getPublicSSH();
 
     const userLen = Buffer.byteLength(username);

lib/protocol/kex.js

@@ -197,6 +197,8 @@ function handleKexInit(self, payload) {
   const local = self._offer;
   const remote = init;
 
+  self._remoteHostKeyAlgorithms = remote.serverHostKey;
+
   let localKex = local.lists.kex.array;
   if (self._compatFlags & COMPAT.BAD_DHGEX) {
     let found = false;