In GUI PuTTY, log standard error from local proxy commands.

On both Unix and Windows, we now redirect the local proxy command's
standard error into a third pipe; data received from that pipe is
broken up at newlines and logged in the Event Log. So if the proxy
command emits any error messages in the course of failing to connect
to something, you now have a fighting chance of finding out what went
wrong.

This feature is disabled in command-line tools like PSFTP and Plink,
on the basis that in that situation it seems more likely that the user
would expect standard-error output to go to the ordinary standard
error in the ordinary way. Only GUI PuTTY catches it and logs it like
this, because it either doesn't have a standard error at all (on
Windows) or is likely to be pointing it at some completely unhelpful
session log file (under X).

windows/winhsock.c

@@ -18,8 +18,8 @@ struct Socket_handle_tag {
     const struct socket_function_table *fn;
     /* the above variable absolutely *must* be the first in this structure */
 
-    HANDLE send_H, recv_H;
-    struct handle *send_h, *recv_h;
+    HANDLE send_H, recv_H, stderr_H;
+    struct handle *send_h, *recv_h, *stderr_h;
 
     /*
      * Freezing one of these sockets is a slightly fiddly business,
@@ -39,6 +39,9 @@ struct Socket_handle_tag {
     /* We buffer data here if we receive it from winhandl while frozen. */
     bufchain inputdata;
 
+    /* Data received from stderr_H, if we have one. */
+    bufchain stderrdata;
+
     char *error;
 
     Plug plug;
@@ -75,6 +78,16 @@ static int handle_gotdata(struct handle *h, void *data, int len)
     }
 }
 
+static int handle_stderr(struct handle *h, void *data, int len)
+{
+    Handle_Socket ps = (Handle_Socket) handle_get_privdata(h);
+
+    if (len > 0)
+        log_proxy_stderr(ps->plug, &ps->stderrdata, data, len);
+
+    return 0;
+}
+
 static void handle_sentdata(struct handle *h, int new_backlog)
 {
     Handle_Socket ps = (Handle_Socket) handle_get_privdata(h);
@@ -101,6 +114,7 @@ static void sk_handle_close(Socket s)
     if (ps->recv_H != ps->send_H)
         CloseHandle(ps->recv_H);
     bufchain_clear(&ps->inputdata);
+    bufchain_clear(&ps->stderrdata);
 
     sfree(ps);
 }
@@ -259,8 +273,8 @@ static char *sk_handle_peer_info(Socket s)
     return NULL;
 }
 
-Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, Plug plug,
-                          int overlapped)
+Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, HANDLE stderr_H,
+                          Plug plug, int overlapped)
 {
     static const struct socket_function_table socket_fn_table = {
 	sk_handle_plug,
@@ -283,11 +297,16 @@ Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, Plug plug,
     ret->error = NULL;
     ret->frozen = UNFROZEN;
     bufchain_init(&ret->inputdata);
+    bufchain_init(&ret->stderrdata);
 
     ret->recv_H = recv_H;
     ret->recv_h = handle_input_new(ret->recv_H, handle_gotdata, ret, flags);
     ret->send_H = send_H;
     ret->send_h = handle_output_new(ret->send_H, handle_sentdata, ret, flags);
+    ret->stderr_H = stderr_H;
+    if (ret->stderr_H)
+        ret->stderr_h = handle_input_new(ret->stderr_H, handle_stderr,
+                                         ret, flags);
 
     return (Socket) ret;
 }

windows/winnpc.c

@@ -16,8 +16,8 @@
 
 #include "winsecur.h"
 
-Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, Plug plug,
-                          int overlapped);
+Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, HANDLE stderr_H,
+                          Plug plug, int overlapped);
 
 Socket new_named_pipe_client(const char *pipename, Plug plug)
 {
@@ -96,7 +96,7 @@ Socket new_named_pipe_client(const char *pipename, Plug plug)
     LocalFree(psd);
     sfree(usersid);
 
-    return make_handle_socket(pipehandle, pipehandle, plug, TRUE);
+    return make_handle_socket(pipehandle, pipehandle, NULL, plug, TRUE);
 }
 
 #endif /* !defined NO_SECURITY */

windows/winnps.c

@@ -16,8 +16,8 @@
 
 #include "winsecur.h"
 
-Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, Plug plug,
-                          int overlapped);
+Socket make_handle_socket(HANDLE send_H, HANDLE recv_H, HANDLE stderr_H,
+                          Plug plug, int overlapped);
 
 typedef struct Socket_named_pipe_server_tag *Named_Pipe_Server_Socket;
 struct Socket_named_pipe_server_tag {
@@ -120,7 +120,7 @@ static Socket named_pipe_accept(accept_ctx_t ctx, Plug plug)
 {
     HANDLE conn = (HANDLE)ctx.p;
 
-    return make_handle_socket(conn, conn, plug, TRUE);
+    return make_handle_socket(conn, conn, NULL, plug, TRUE);
 }
 
 /*

windows/winproxy.c

@@ -22,7 +22,9 @@ Socket platform_new_connection(SockAddr addr, const char *hostname,
 			       Plug plug, Conf *conf)
 {
     char *cmd;
-    HANDLE us_to_cmd, us_from_cmd, cmd_to_us, cmd_from_us;
+    HANDLE us_to_cmd, cmd_from_us;
+    HANDLE us_from_cmd, cmd_to_us;
+    HANDLE us_from_cmd_err, cmd_err_to_us;
     SECURITY_ATTRIBUTES sa;
     STARTUPINFO si;
     PROCESS_INFORMATION pi;
@@ -64,8 +66,25 @@ Socket platform_new_connection(SockAddr addr, const char *hostname,
 	return ret;
     }
 
+    if (flags & FLAG_STDERR) {
+        /* If we have a sensible stderr, the proxy command can send
+         * its own standard error there, so we won't interfere. */
+        us_from_cmd_err = cmd_err_to_us = NULL;
+    } else {
+        /* If we don't have a sensible stderr, we should catch the
+         * proxy command's standard error to put in our event log. */
+        if (!CreatePipe(&us_from_cmd_err, &cmd_err_to_us, &sa, 0)) {
+            Socket ret = new_error_socket
+                ("Unable to create pipes for proxy command", plug);
+            sfree(cmd);
+            return ret;
+        }
+    }
+
     SetHandleInformation(us_to_cmd, HANDLE_FLAG_INHERIT, 0);
     SetHandleInformation(us_from_cmd, HANDLE_FLAG_INHERIT, 0);
+    if (us_from_cmd_err != NULL)
+        SetHandleInformation(us_from_cmd_err, HANDLE_FLAG_INHERIT, 0);
 
     si.cb = sizeof(si);
     si.lpReserved = NULL;
@@ -76,7 +95,7 @@ Socket platform_new_connection(SockAddr addr, const char *hostname,
     si.lpReserved2 = NULL;
     si.hStdInput = cmd_from_us;
     si.hStdOutput = cmd_to_us;
-    si.hStdError = NULL;
+    si.hStdError = cmd_err_to_us;
     CreateProcess(NULL, cmd, NULL, NULL, TRUE,
 		  CREATE_NO_WINDOW | NORMAL_PRIORITY_CLASS,
 		  NULL, NULL, &si, &pi);
@@ -88,5 +107,9 @@ Socket platform_new_connection(SockAddr addr, const char *hostname,
     CloseHandle(cmd_from_us);
     CloseHandle(cmd_to_us);
 
-    return make_handle_socket(us_to_cmd, us_from_cmd, plug, FALSE);
+    if (cmd_err_to_us != NULL)
+        CloseHandle(cmd_err_to_us);
+
+    return make_handle_socket(us_to_cmd, us_from_cmd, us_from_cmd_err,
+                              plug, FALSE);
 }