Implement a Git LFS server which supports no operations

Summary:
Ref T7789. This builds on top of `git-lfs-authenticate` to detect LFS requests, read LFS tokens, and route them to a handler which can do useful things.

This handler promptly drops them on the floor with an error message.

Test Plan:
Here's a transcript showing the parts working together so far:

  - `git-lfs` connects to the server with SSH, and gets told how to connect with HTTP to do uploads.
  - `git-lfs` uses HTTP, and authenticates with the tokens properly.
  - But the server tells it to go away, and that it doesn't support anything, so the operation ultimately fails.

```
$ GIT_TRACE=1 git lfs push origin master
12:45:56.153913 git.c:558               trace: exec: 'git-lfs' 'push' 'origin' 'master'
12:45:56.154376 run-command.c:335       trace: run_command: 'git-lfs' 'push' 'origin' 'master'
trace git-lfs: Upload refs origin to remote [master]
trace git-lfs: run_command: git rev-list --objects master --not --remotes=origin
trace git-lfs: run_command: git cat-file --batch-check
trace git-lfs: run_command: git cat-file --batch
trace git-lfs: run_command: 'git' config -l
trace git-lfs: tq: starting 3 transfer workers
trace git-lfs: tq: running as batched queue, batch size of 100
trace git-lfs: prepare upload: b7e0aeb82a03d627c6aa5fc1bbfd454b6789d9d9affc8607d40168fa18cf6c69 lfs/dog1.jpg 1/1
trace git-lfs: tq: sending batch of size 1
trace git-lfs: ssh: local@localvault.phacility.com git-lfs-authenticate diffusion/18/poems.git upload
trace git-lfs: api: batch 1 files
trace git-lfs: HTTP: POST http://local.phacility.com/diffusion/POEMS/poems.git/info/lfs/objects/batch
trace git-lfs: HTTP: 404
trace git-lfs: HTTP: {"message":"Git LFS operation \"objects\/batch\" is not supported by this server."}
trace git-lfs: HTTP:
trace git-lfs: api: batch not implemented: 404
trace git-lfs: run_command: 'git' config lfs.batch false
trace git-lfs: tq: batch api not implemented, falling back to individual
trace git-lfs: ssh: local@localvault.phacility.com git-lfs-authenticate diffusion/18/poems.git upload b7e0aeb82a03d627c6aa5fc1bbfd454b6789d9d9affc8607d40168fa18cf6c69
trace git-lfs: api: uploading (b7e0aeb82a03d627c6aa5fc1bbfd454b6789d9d9affc8607d40168fa18cf6c69)
trace git-lfs: HTTP: POST http://local.phacility.com/diffusion/POEMS/poems.git/info/lfs/objects
trace git-lfs: HTTP: 404
trace git-lfs: HTTP: {"message":"Git LFS operation \"objects\" is not supported by this server."}
trace git-lfs: HTTP:
trace git-lfs: tq: retrying 1 failed transfers
trace git-lfs: ssh: local@localvault.phacility.com git-lfs-authenticate diffusion/18/poems.git upload b7e0aeb82a03d627c6aa5fc1bbfd454b6789d9d9affc8607d40168fa18cf6c69
trace git-lfs: api: uploading (b7e0aeb82a03d627c6aa5fc1bbfd454b6789d9d9affc8607d40168fa18cf6c69)
trace git-lfs: HTTP: POST http://local.phacility.com/diffusion/POEMS/poems.git/info/lfs/objects
trace git-lfs: HTTP: 404
trace git-lfs: HTTP: {"message":"Git LFS operation \"objects\" is not supported by this server."}
trace git-lfs: HTTP:
Git LFS: (0 of 1 files) 0 B / 87.12 KB
Git LFS operation "objects" is not supported by this server.
Git LFS operation "objects" is not supported by this server.
```

Reviewers: chad

Reviewed By: chad

Subscribers: eadler

Maniphest Tasks: T7789

Differential Revision: https://secure.phabricator.com/D15485

src/__phutil_library_map__.php

@@ -634,6 +634,7 @@ phutil_register_library_map(array(
     'DiffusionGitBranchTestCase' => 'applications/diffusion/data/__tests__/DiffusionGitBranchTestCase.php',
     'DiffusionGitFileContentQuery' => 'applications/diffusion/query/filecontent/DiffusionGitFileContentQuery.php',
     'DiffusionGitLFSAuthenticateWorkflow' => 'applications/diffusion/gitlfs/DiffusionGitLFSAuthenticateWorkflow.php',
+    'DiffusionGitLFSResponse' => 'applications/diffusion/response/DiffusionGitLFSResponse.php',
     'DiffusionGitLFSTemporaryTokenType' => 'applications/diffusion/gitlfs/DiffusionGitLFSTemporaryTokenType.php',
     'DiffusionGitRawDiffQuery' => 'applications/diffusion/query/rawdiff/DiffusionGitRawDiffQuery.php',
     'DiffusionGitReceivePackSSHWorkflow' => 'applications/diffusion/ssh/DiffusionGitReceivePackSSHWorkflow.php',
@@ -4763,6 +4764,7 @@ phutil_register_library_map(array(
     'DiffusionGitBranchTestCase' => 'PhabricatorTestCase',
     'DiffusionGitFileContentQuery' => 'DiffusionFileContentQuery',
     'DiffusionGitLFSAuthenticateWorkflow' => 'DiffusionGitSSHWorkflow',
+    'DiffusionGitLFSResponse' => 'AphrontResponse',
     'DiffusionGitLFSTemporaryTokenType' => 'PhabricatorAuthTemporaryTokenType',
     'DiffusionGitRawDiffQuery' => 'DiffusionRawDiffQuery',
     'DiffusionGitReceivePackSSHWorkflow' => 'DiffusionGitSSHWorkflow',

src/applications/diffusion/controller/DiffusionServeController.php

@@ -5,6 +5,9 @@ final class DiffusionServeController extends DiffusionController {
   private $serviceViewer;
   private $serviceRepository;
 
+  private $isGitLFSRequest;
+  private $gitLFSToken;
+
   public function setServiceViewer(PhabricatorUser $viewer) {
     $this->serviceViewer = $viewer;
     return $this;
@@ -23,6 +26,14 @@ final class DiffusionServeController extends DiffusionController {
     return $this->serviceRepository;
   }
 
+  public function getIsGitLFSRequest() {
+    return $this->isGitLFSRequest;
+  }
+
+  public function getGitLFSToken() {
+    return $this->gitLFSToken;
+  }
+
   public function isVCSRequest(AphrontRequest $request) {
     $identifier = $this->getRepositoryIdentifierFromRequest($request);
     if ($identifier === null) {
@@ -32,6 +43,9 @@ final class DiffusionServeController extends DiffusionController {
     $content_type = $request->getHTTPHeader('Content-Type');
     $user_agent = idx($_SERVER, 'HTTP_USER_AGENT');
 
+    // This may have a "charset" suffix, so only match the prefix.
+    $lfs_pattern = '(^application/vnd\\.git-lfs\\+json(;|\z))';
+
     $vcs = null;
     if ($request->getExists('service')) {
       $service = $request->getStr('service');
@@ -46,6 +60,10 @@ final class DiffusionServeController extends DiffusionController {
     } else if ($content_type == 'application/x-git-receive-pack-request') {
       // We get this for `git-receive-pack`.
       $vcs = PhabricatorRepositoryType::REPOSITORY_TYPE_GIT;
+    } else if (preg_match($lfs_pattern, $content_type)) {
+      // This is a Git LFS HTTP API request.
+      $vcs = PhabricatorRepositoryType::REPOSITORY_TYPE_GIT;
+      $this->isGitLFSRequest = true;
     } else if ($request->getExists('cmd')) {
       // Mercurial also sends an Accept header like
       // "application/mercurial-0.1", and a User-Agent like
@@ -142,7 +160,17 @@ final class DiffusionServeController extends DiffusionController {
       $username = $_SERVER['PHP_AUTH_USER'];
       $password = new PhutilOpaqueEnvelope($_SERVER['PHP_AUTH_PW']);
 
+      // Try Git LFS auth first since we can usually reject it without doing
+      // any queries, since the username won't match the one we expect or the
+      // request won't be LFS.
+      $viewer = $this->authenticateGitLFSUser($username, $password);
+
+      // If that failed, try normal auth. Note that we can use normal auth on
+      // LFS requests, so this isn't strictly an alternative to LFS auth.
+      if (!$viewer) {
         $viewer = $this->authenticateHTTPRepositoryUser($username, $password);
+      }
+
       if (!$viewer) {
         return new PhabricatorVCSResponse(
           403,
@@ -202,6 +230,11 @@ final class DiffusionServeController extends DiffusionController {
       }
     }
 
+    $response = $this->validateGitLFSRequest($repository, $viewer);
+    if ($response) {
+      return $response;
+    }
+
     $this->setServiceRepository($repository);
 
     if (!$repository->isTracked()) {
@@ -212,6 +245,12 @@ final class DiffusionServeController extends DiffusionController {
 
     $is_push = !$this->isReadOnlyRequest($repository);
 
+    if ($this->getIsGitLFSRequest() && $this->getGitLFSToken()) {
+      // We allow git LFS requests over HTTP even if the repository does not
+      // otherwise support HTTP reads or writes, as long as the user is using a
+      // token from SSH. If they're using HTTP username + password auth, they
+      // have to obey the normal HTTP rules.
+    } else {
       switch ($repository->getServeOverHTTP()) {
         case PhabricatorRepository::SERVE_READONLY:
           if ($is_push) {
@@ -221,6 +260,16 @@ final class DiffusionServeController extends DiffusionController {
           }
           break;
         case PhabricatorRepository::SERVE_READWRITE:
+          // We'll check for push capability below.
+          break;
+        case PhabricatorRepository::SERVE_OFF:
+        default:
+          return new PhabricatorVCSResponse(
+            403,
+            pht('This repository is not available over HTTP.'));
+      }
+    }
+
     if ($is_push) {
       $can_push = PhabricatorPolicyFilter::hasCapability(
         $viewer,
@@ -230,7 +279,9 @@ final class DiffusionServeController extends DiffusionController {
         if ($viewer->isLoggedIn()) {
           return new PhabricatorVCSResponse(
             403,
-                pht('You do not have permission to push to this repository.'));
+            pht(
+              'You do not have permission to push to this '.
+              'repository.'));
         } else {
           if ($allow_auth) {
             return new PhabricatorVCSResponse(
@@ -246,13 +297,6 @@ final class DiffusionServeController extends DiffusionController {
         }
       }
     }
-        break;
-      case PhabricatorRepository::SERVE_OFF:
-      default:
-        return new PhabricatorVCSResponse(
-          403,
-          pht('This repository is not available over HTTP.'));
-    }
 
     $vcs_type = $repository->getVersionControlSystem();
     $req_type = $this->isVCSRequest($request);
@@ -324,6 +368,14 @@ final class DiffusionServeController extends DiffusionController {
     PhabricatorRepository $repository,
     PhabricatorUser $viewer) {
 
+    // We can serve Git LFS requests first, since we don't need to proxy them.
+    // It's also important that LFS requests never fall through to standard
+    // service pathways, because that would let you use LFS tokens to read
+    // normal repository data.
+    if ($this->getIsGitLFSRequest()) {
+      return $this->serveGitLFSRequest($repository, $viewer);
+    }
+
     // If this repository is hosted on a service, we need to proxy the request
     // to a host which can serve it.
     $is_cluster_request = $this->getRequest()->isProxiedClusterRequest();
@@ -363,6 +415,8 @@ final class DiffusionServeController extends DiffusionController {
 
     // TODO: This implementation is safe by default, but very incomplete.
 
+    // TODO: This doesn't get the right result for Git LFS yet.
+
     switch ($repository->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         $service = $request->getStr('service');
@@ -514,6 +568,52 @@ final class DiffusionServeController extends DiffusionController {
     return $base_path;
   }
 
+  private function authenticateGitLFSUser(
+    $username,
+    PhutilOpaqueEnvelope $password) {
+
+    // Never accept these credentials for requests which aren't LFS requests.
+    if (!$this->getIsGitLFSRequest()) {
+      return null;
+    }
+
+    // If we have the wrong username, don't bother checking if the token
+    // is right.
+    if ($username !== DiffusionGitLFSTemporaryTokenType::HTTP_USERNAME) {
+      return null;
+    }
+
+    $lfs_pass = $password->openEnvelope();
+    $lfs_hash = PhabricatorHash::digest($lfs_pass);
+
+    $token = id(new PhabricatorAuthTemporaryTokenQuery())
+      ->setViewer(PhabricatorUser::getOmnipotentUser())
+      ->withTokenTypes(array(DiffusionGitLFSTemporaryTokenType::TOKENTYPE))
+      ->withTokenCodes(array($lfs_hash))
+      ->withExpired(false)
+      ->executeOne();
+    if (!$token) {
+      return null;
+    }
+
+    $user = id(new PhabricatorPeopleQuery())
+      ->setViewer(PhabricatorUser::getOmnipotentUser())
+      ->withPHIDs(array($token->getUserPHID()))
+      ->executeOne();
+
+    if (!$user) {
+      return null;
+    }
+
+    if (!$user->isUserActivated()) {
+      return null;
+    }
+
+    $this->gitLFSToken = $token;
+
+    return $user;
+  }
+
   private function authenticateHTTPRepositoryUser(
     $username,
     PhutilOpaqueEnvelope $password) {
@@ -739,4 +839,68 @@ final class DiffusionServeController extends DiffusionController {
     );
   }
 
+  private function validateGitLFSRequest(
+    PhabricatorRepository $repository,
+    PhabricatorUser $viewer) {
+    if (!$this->getIsGitLFSRequest()) {
+      return null;
+    }
+
+    if (!$repository->canUseGitLFS()) {
+      return new PhabricatorVCSResponse(
+        403,
+        pht(
+          'The requested repository ("%s") does not support Git LFS.',
+          $repository->getDisplayName()));
+    }
+
+    // If this is using an LFS token, sanity check that we're using it on the
+    // correct repository. This shouldn't really matter since the user could
+    // just request a proper token anyway, but it suspicious and should not
+    // be permitted.
+
+    $token = $this->getGitLFSToken();
+    if ($token) {
+      $resource = $token->getTokenResource();
+      if ($resource !== $repository->getPHID()) {
+        return new PhabricatorVCSResponse(
+          403,
+          pht(
+            'The authentication token provided in the request is bound to '.
+            'a different repository than the requested repository ("%s").',
+            $repository->getDisplayName()));
+      }
+    }
+
+    return null;
+  }
+
+  private function serveGitLFSRequest(
+    PhabricatorRepository $repository,
+    PhabricatorUser $viewer) {
+
+    if (!$this->getIsGitLFSRequest()) {
+      throw new Exception(pht('This is not a Git LFS request!'));
+    }
+
+    $path = $this->getGitLFSRequestPath($repository);
+
+    return DiffusionGitLFSResponse::newErrorResponse(
+      404,
+      pht(
+        'Git LFS operation "%s" is not supported by this server.',
+        $path));
+  }
+
+  private function getGitLFSRequestPath(PhabricatorRepository $repository) {
+    $request_path = $this->getRequestDirectoryPath($repository);
+
+    $matches = null;
+    if (preg_match('(^/info/lfs(?:\z|/)(.*))', $request_path, $matches)) {
+      return $matches[1];
+    }
+
+    return null;
+  }
+
 }

src/applications/diffusion/response/DiffusionGitLFSResponse.php

@@ -0,0 +1,37 @@
+<?php
+
+final class DiffusionGitLFSResponse extends AphrontResponse {
+
+  private $content;
+
+  public static function newErrorResponse($code, $message) {
+
+    // We can optionally include "request_id" and "documentation_url" in
+    // this response.
+
+    return id(new self())
+      ->setHTTPResponseCode($code)
+      ->setContent(
+        array(
+          'message' => $message,
+        ));
+  }
+
+  public function setContent(array $content) {
+    $this->content = phutil_json_encode($content);
+    return $this;
+  }
+
+  public function buildResponseString() {
+    return $this->content;
+  }
+
+  public function getHeaders() {
+    $headers = array(
+      array('Content-Type', 'application/vnd.git-lfs+json'),
+    );
+
+    return array_merge(parent::getHeaders(), $headers);
+  }
+
+}