Merge pull request #145 from mochi/ssl-transport-accept

mitigate SSL and emfile related conditions per #138

.travis.yml

@@ -2,11 +2,7 @@ language: erlang
 notifications:
   email: false
 otp_release:
+  - 17.1
   - 17.0
   - R16B03-1
-  - R16B03
-  - R16B02
-  - R16B01
-  - R16B
   - R15B03
-  - R15B02

CHANGES.md

@@ -1,3 +1,12 @@
+Version 2.11.0 released 2015-01-12
+
+* Perform SSL handshake after releasing acceptor back into the pool,
+  and slow accept rate when file descriptors are not available,
+  to mitigate a potential DoS attack. Adds new mochiweb_socket
+  functions transport_accept/1 and finish_accept/1 which should be
+  used in preference to the now deprecated accept/1 function.
+  https://github.com/mochi/mochiweb/issues/138
+
 Version 2.10.1 released 2015-01-11
 
 * Fixes issue with SSL and mochiweb_websocket. Note that

src/mochiweb.app.src

@@ -1,7 +1,7 @@
 %% This is generated from src/mochiweb.app.src
 {application, mochiweb,
  [{description, "MochiMedia Web Server"},
-  {vsn, "2.10.1"},
+  {vsn, "2.11.0"},
   {modules, []},
   {registered, []},
   {env, []},

src/mochiweb_acceptor.erl

@@ -10,25 +10,44 @@
 
 -export([start_link/3, start_link/4, init/4]).
 
+-define(EMFILE_SLEEP_MSEC, 100).
+
 start_link(Server, Listen, Loop) ->
     start_link(Server, Listen, Loop, []).
 
 start_link(Server, Listen, Loop, Opts) ->
     proc_lib:spawn_link(?MODULE, init, [Server, Listen, Loop, Opts]).
 
-init(Server, Listen, Loop, Opts) ->
+do_accept(Server, Listen) ->
     T1 = os:timestamp(),
-    case catch mochiweb_socket:accept(Listen) of
+    case mochiweb_socket:transport_accept(Listen) of
         {ok, Socket} ->
             gen_server:cast(Server, {accepted, self(), timer:now_diff(os:timestamp(), T1)}),
+            mochiweb_socket:finish_accept(Socket);
+        Other ->
+            Other
+    end.
+
+init(Server, Listen, Loop, Opts) ->
+    case catch do_accept(Server, Listen) of
+        {ok, Socket} ->
             call_loop(Loop, Socket, Opts);
-        {error, closed} ->
-            exit(normal);
-        {error, timeout} ->
-            init(Server, Listen, Loop, Opts);
-        {error, esslaccept} ->
+        {error, Err} when Err =:= closed orelse
+                          Err =:= esslaccept orelse
+                          Err =:= timeout ->
             exit(normal);
         Other ->
+            %% Mitigate out of file descriptor scenario by sleeping for a
+            %% short time to slow error rate
+            case Other of
+                {error, emfile} ->
+                    receive
+                    after ?EMFILE_SLEEP_MSEC ->
+                            ok
+                    end;
+                _ ->
+                    ok
+            end,
             error_logger:error_report(
               [{application, mochiweb},
                "Accept failed error",
@@ -44,10 +63,3 @@ call_loop({M, F, A}, Socket, Opts) ->
     erlang:apply(M, F, [Socket, Opts | A]);
 call_loop(Loop, Socket, Opts) ->
     Loop(Socket, Opts).
-
-%%
-%% Tests
-%%
--ifdef(TEST).
--include_lib("eunit/include/eunit.hrl").
--endif.

src/mochiweb_socket.erl

@@ -4,7 +4,9 @@
 
 -module(mochiweb_socket).
 
--export([listen/4, accept/1, recv/3, send/2, close/1, port/1, peername/1,
+-export([listen/4,
+         accept/1, transport_accept/1, finish_accept/1,
+         recv/3, send/2, close/1, port/1, peername/1,
          setopts/2, getopts/2, type/1]).
 
 -define(ACCEPT_TIMEOUT, 2000).
@@ -66,27 +68,35 @@ filter_unsafe_protcol_versions(Versions) ->
                  end,
                  Versions).
 
+%% Provided for backwards compatibility only
+accept(ListenSocket) ->
+    case transport_accept(ListenSocket) of
+        {ok, Socket} ->
+            finish_accept(Socket);
+        {error, _} = Err ->
+            Err
+    end.
 
-accept({ssl, ListenSocket}) ->
-    % There's a bug in ssl:transport_accept/2 at the moment, which is the
-    % reason for the try...catch block. Should be fixed in OTP R14.
-    try ssl:transport_accept(ListenSocket, ?SSL_TIMEOUT) of
+transport_accept({ssl, ListenSocket}) ->
+    case ssl:transport_accept(ListenSocket, ?SSL_TIMEOUT) of
         {ok, Socket} ->
-            case ssl:ssl_accept(Socket, ?SSL_HANDSHAKE_TIMEOUT) of
-                ok ->
-                    {ok, {ssl, Socket}};
-                {error, _} = Err ->
-                    Err
-            end;
+            {ok, {ssl, Socket}};
         {error, _} = Err ->
             Err
-    catch
-        error:{badmatch, {error, Reason}} ->
-            {error, Reason}
     end;
-accept(ListenSocket) ->
+transport_accept(ListenSocket) ->
     gen_tcp:accept(ListenSocket, ?ACCEPT_TIMEOUT).
 
+finish_accept({ssl, Socket}) ->
+    case ssl:ssl_accept(Socket, ?SSL_HANDSHAKE_TIMEOUT) of
+        ok ->
+            {ok, {ssl, Socket}};
+        {error, _} = Err ->
+            Err
+    end;
+finish_accept(Socket) ->
+    {ok, Socket}.
+
 recv({ssl, Socket}, Length, Timeout) ->
     ssl:recv(Socket, Length, Timeout);
 recv(Socket, Length, Timeout) ->