[lldb-dev] Trying to use socketpair for lldb-server fails

[Demi Obenour via lldb-dev]

To avoid a local privilage escalation, I am trying to patch LLDB not to
use a TCP socket for local communication.

The attached patch failed.  Would anyone be able to provide suggestions
for how to debug the problem?

Sincerely,

Demi
-------------- next part --------------
Index: source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
===================================================================
--- source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp	(revision 308480)
+++ source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp	(working copy)
@@ -3289,7 +3289,8 @@
   }
   return error;
 }
-#if defined(__APPLE__)
+#ifndef _WIN32
+//#ifdef __APPLE__
 #define USE_SOCKETPAIR_FOR_LOCAL_CONNECTION 1
 #endif
 
Index: tools/lldb-server/lldb-gdbserver.cpp
===================================================================
--- tools/lldb-server/lldb-gdbserver.cpp	(revision 308480)
+++ tools/lldb-server/lldb-gdbserver.cpp	(working copy)
@@ -97,6 +97,7 @@
     {"attach", required_argument, NULL, 'a'},
     {"named-pipe", required_argument, NULL, 'N'},
     {"pipe", required_argument, NULL, 'U'},
+    {"fd", required_argument, NULL, 'F'},
     {"native-regs", no_argument, NULL,
      'r'}, // Specify to use the native registers instead of the gdb defaults
            // for the architecture.  NOTE: this is a do-nothing arg as it's
@@ -232,7 +233,8 @@
                      GDBRemoteCommunicationServerLLGS &gdb_server,
                      bool reverse_connect, const char *const host_and_port,
                      const char *const progname, const char *const subcommand,
-                     const char *const named_pipe_path, int unnamed_pipe_fd) {
+                     const char *const named_pipe_path, int unnamed_pipe_fd,
+                     int connection_fd) {
   Status error;
 
   if (host_and_port && host_and_port[0]) {
@@ -257,7 +259,24 @@
 
     std::unique_ptr<Connection> connection_up;
 
-    if (reverse_connect) {
+    if (connection_fd != -1) {
+      abort();
+      char connection_url[512];
+      snprintf(connection_url, sizeof(connection_url), "fd://%d", connection_fd);
+      connection_up.reset(new ConnectionFileDescriptor);
+      auto connection_result = connection_up->Connect(connection_url, &error);
+      if (connection_result != eConnectionStatusSuccess) {
+        fprintf(stderr, "error: failed to connect to client at '%s' "
+                        "(connection status: %d)",
+                connection_url, static_cast<int>(connection_result));
+        exit(-1);
+      }
+      if (error.Fail()) {
+        fprintf(stderr, "error: failed to connect to client at '%s': %s",
+                connection_url, error.AsCString());
+        exit(-1);
+      }
+    } else if (reverse_connect) {
       // llgs will connect to the gdb-remote client.
 
       // Ensure we have a port number for the connection.
@@ -364,6 +383,7 @@
       log_channels; // e.g. "lldb process threads:gdb-remote default:linux all"
   int unnamed_pipe_fd = -1;
   bool reverse_connect = false;
+  int connection_fd = -1;
 
   // ProcessLaunchInfo launch_info;
   ProcessAttachInfo attach_info;
@@ -413,6 +433,11 @@
       reverse_connect = true;
       break;
 
+    case 'F':
+      if (optarg && optarg[0])
+        connection_fd = StringConvert::ToUInt32(optarg, -1);
+      break;
+
 #ifndef _WIN32
     case 'S':
       // Put llgs into a new session. Terminals group processes
@@ -501,7 +526,7 @@
 
   ConnectToRemote(mainloop, gdb_server, reverse_connect, host_and_port,
                   progname, subcommand, named_pipe_path.c_str(),
-                  unnamed_pipe_fd);
+                  unnamed_pipe_fd, connection_fd);
 
   if (!gdb_server.IsConnected()) {
     fprintf(stderr, "no connection information provided, unable to run\n");