Allow Passphrase to store empty secrets

Summary: Fixes T6001. We currently don't allow empty secrets, but accounts with no password are occasionally used in the wild.

Test Plan:
  - Created a credential with an empty secret.
  - Revealed secret, saw empty message.
  - Edited it (no form changes), saw secret unchanged.
  - Changed it to a nonempty secret.
  - Revealed nonempty secret.
  - Edited it (no form changes), saw secret unchanged.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6001

Differential Revision: https://secure.phabricator.com/D10414

src/applications/passphrase/controller/PassphraseCredentialEditController.php

@@ -155,8 +155,13 @@ final class PassphraseCredentialEditController extends PassphraseController {
             ->setTransactionType($type_username)
             ->setNewValue($v_username);
 
-          $min_secret = str_replace($bullet, '', trim($v_decrypt));
-          if (strlen($min_secret)) {
+          // If some value other than a sequence of bullets was provided for
+          // the credential, update it. In particular, note that we are
+          // explicitly allowing empty secrets: one use case is HTTP auth where
+          // the username is a secret token which covers both identity and
+          // authentication.
+
+          if (!preg_match('/^('.$bullet.')+$/', trim($v_decrypt))) {
             // If the credential was previously destroyed, restore it when it is
             // edited if a secret is provided.
             $xactions[] = id(new PassphraseCredentialTransaction())

src/applications/passphrase/controller/PassphraseCredentialRevealController.php

@@ -46,16 +46,19 @@ final class PassphraseCredentialRevealController
     }
 
     if ($request->isFormPost()) {
-      if ($credential->getSecret()) {
+      $secret = $credential->getSecret();
+      if (!$secret) {
+        $body = pht('This credential has no associated secret.');
+      } else if (!strlen($secret->openEnvelope())) {
+        $body = pht('This credential has an empty secret.');
+      } else {
         $body = id(new PHUIFormLayoutView())
           ->appendChild(
             id(new AphrontFormTextAreaControl())
               ->setLabel(pht('Plaintext'))
               ->setReadOnly(true)
               ->setHeight(AphrontFormTextAreaControl::HEIGHT_VERY_TALL)
-              ->setValue($credential->getSecret()->openEnvelope()));
-      } else {
-        $body = pht('This credential has no associated secret.');
+              ->setValue($secret->openEnvelope()));
       }
 
       // NOTE: Disable workflow on the cancel button to reload the page so