Support ecdsa-sha2-nistp256 SSH keys

Summary:
See discussion in <https://github.com/facebook/phabricator/issues/430>.

(If we end up with more than like 5 of these we should probably make this a warning or something instead, the only goal is to prevent user error.)

Test Plan:
{F79196}

{F79197}

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran, enko

Differential Revision: https://secure.phabricator.com/D7522

Author: epriestley

src/applications/settings/panel/PhabricatorSettingsPanelSSHKeys.php

@@ -81,9 +81,17 @@ public function processRequest(AphrontRequest $request) {
 
         if (!$errors) {
           list($type, $body, $comment) = $parts;
-          if (!preg_match('/^ssh-dsa|ssh-rsa$/', $type)) {
+
+          $recognized_keys = array(
+            'ssh-dsa',
+            'ssh-rsa',
+            'ecdsa-sha2-nistp256',
+          );
+
+          if (!in_array($type, $recognized_keys)) {
             $e_key = pht('Invalid');
-            $errors[] = pht('Public key should be "ssh-dsa" or "ssh-rsa".');
+            $type_list = implode(', ', $recognized_keys);
+            $errors[] = pht('Public key should be one of: %s', $type_list);
           } else {
             $key->setKeyType($type);
             $key->setKeyBody($body);