Stop 'git push' over HTTP early

Before this change we always let users push Git data over HTTP before
deciding whether to accept to push. This was different from pushing
over SSH where we terminate a 'git push' early if we already know the
user is not allowed to push.

This change let Git over HTTP follow the same behavior as Git over
SSH. We also distinguish between HTTP 404 and 403 responses when
denying Git requests, depending on whether the user is allowed to know
the project exists.

app/controllers/projects/git_http_controller.rb

@@ -20,9 +20,9 @@ class Projects::GitHttpController < Projects::ApplicationController
     elsif receive_pack? && receive_pack_allowed?
       render_ok
     elsif http_blocked?
-      render_not_allowed
+      render_http_not_allowed
     else
-      render_not_found
+      render_denied
     end
   end
 
@@ -31,7 +31,7 @@ class Projects::GitHttpController < Projects::ApplicationController
     if upload_pack? && upload_pack_allowed?
       render_ok
     else
-      render_not_found
+      render_denied
     end
   end
 
@@ -40,7 +40,7 @@ class Projects::GitHttpController < Projects::ApplicationController
     if receive_pack? && receive_pack_allowed?
       render_ok
     else
-      render_not_found
+      render_denied
     end
   end
 
@@ -156,8 +156,17 @@ class Projects::GitHttpController < Projects::ApplicationController
     render plain: 'Not Found', status: :not_found
   end
 
-  def render_not_allowed
-    render plain: download_access.message, status: :forbidden
+  def render_http_not_allowed
+    render plain: access_check.message, status: :forbidden
+  end
+
+  def render_denied
+    if user && user.can?(:read_project, project)
+      render plain: 'Access denied', status: :forbidden
+    else
+      # Do not leak information about project existence
+      render_not_found
+    end
   end
 
   def ci?
@@ -168,22 +177,20 @@ class Projects::GitHttpController < Projects::ApplicationController
     return false unless Gitlab.config.gitlab_shell.upload_pack
 
     if user
-      download_access.allowed?
+      access_check.allowed?
     else
       ci? || project.public?
     end
   end
 
   def access
-    return @access if defined?(@access)
-
-    @access = Gitlab::GitAccess.new(user, project, 'http')
+    @access ||= Gitlab::GitAccess.new(user, project, 'http')
   end
 
-  def download_access
-    return @download_access if defined?(@download_access)
-
-    @download_access = access.check('git-upload-pack')
+  def access_check
+    # Use the magic string '_any' to indicate we do not know what the
+    # changes are. This is also what gitlab-shell does.
+    @access_check ||= access.check(git_command, '_any')
   end
 
   def http_blocked?
@@ -193,8 +200,6 @@ class Projects::GitHttpController < Projects::ApplicationController
   def receive_pack_allowed?
     return false unless Gitlab.config.gitlab_shell.receive_pack
 
-    # Skip user authorization on upload request.
-    # It will be done by the pre-receive hook in the repository.
-    user.present?
+    access_check.allowed?
   end
 end

lib/gitlab/git_access.rb

@@ -14,7 +14,7 @@ module Gitlab
       @user_access = UserAccess.new(user, project: project)
     end
 
-    def check(cmd, changes = nil)
+    def check(cmd, changes)
       return build_status_object(false, "Git access over #{protocol.upcase} is not allowed") unless protocol_allowed?
 
       unless actor

spec/requests/git_http_spec.rb

@@ -75,9 +75,9 @@ describe 'Git HTTP requests', lib: true do
       context "with correct credentials" do
         let(:env) { { user: user.username, password: user.password } }
 
-        it "uploads get status 200 (because Git hooks do the real check)" do
+        it "uploads get status 403" do
           upload(path, env) do |response|
-            expect(response).to have_http_status(200)
+            expect(response).to have_http_status(403)
           end
         end
 
@@ -86,7 +86,7 @@ describe 'Git HTTP requests', lib: true do
             allow(Gitlab.config.gitlab_shell).to receive(:receive_pack).and_return(false)
 
             upload(path, env) do |response|
-              expect(response).to have_http_status(404)
+              expect(response).to have_http_status(403)
             end
           end
         end
@@ -236,9 +236,9 @@ describe 'Git HTTP requests', lib: true do
               end
             end
 
-            it "uploads get status 200 (because Git hooks do the real check)" do
+            it "uploads get status 404" do
               upload(path, user: user.username, password: user.password) do |response|
-                expect(response).to have_http_status(200)
+                expect(response).to have_http_status(404)
               end
             end
           end