[Openvpn-devel,v3] Swap the order of checks for validating interactive service user

Message ID 1581309200-27870-1-git-send-email-selva.nair@gmail.com
State Accepted
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Series
  • [Openvpn-devel,v3] Swap the order of checks for validating interactive service user
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Commit Message

Selva Nair Feb. 10, 2020, 4:33 a.m.
From: Selva Nair <selva.nair@gmail.com>

Check the config file location and command line options first
and membership in OpenVPNAdministrators group after that as
the latter could be a slow process for active directory users.

When connection to domain controllers is poor or unavailable, checking
the group membership is slow and causes timeouts in the GUI (Trac
1051). However, in cases where the config is in the global directory,
no group membership check should be required. The re-ordering here
avoids the redundant check in such cases.

In addition to this, its also proposed to improve the timeout handling
in the GUI, but this change is still useful as it should completely
eliminate the timeout issue for many users.

v3: Do not send error message to the client pipe from ValidateOptions().
Instead save the error and send it on only if user authorization also
fails. The error buffer size is increased to 512 wide chars as these
messages could get long in some cases and may get truncated otherwise.

Also see: https://github.com/OpenVPN/openvpn-gui/issues/332

Signed-off-by: Selva Nair <selva.nair@gmail.com>
---
v2: Add missing closing parenthesis and improve the comment
above the edited chunk.

 src/openvpnserv/interactive.c | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

Comments

Lev Stipakov Feb. 10, 2020, 8:49 a.m. | #1
Built with MSVC and tested, works as described - membership
check is performed only if options validation fails. Also error message
is sent only when user is not authorized (this got broken in v2).

Acked-by: Lev Stipakov <lstipakov@gmail.com>
<div dir="ltr"><div>Built with MSVC and tested, works as described - membership</div><div>check is performed only if options validation fails. Also error message</div><div>is sent only when user is not authorized (this got broken in v2).</div><div><br></div><div>Acked-by: Lev Stipakov &lt;<a href="mailto:lstipakov@gmail.com">lstipakov@gmail.com</a>&gt;</div></div>
Gert Doering Feb. 10, 2020, 10:16 a.m. | #2
Your patch has been applied to the master branch.

I have not tested this in any way, but since Lev has reviewed & tested 
v2 (and found a bug) and reviewed & tested v3, I do not think I would
add much value anyway.

commit c6cc66a13568dd1078bfbeb763998c1b9e2a2999
Author: Selva Nair
Date:   Sun Feb 9 23:33:20 2020 -0500

     Swap the order of checks for validating interactive service user

     Signed-off-by: Selva Nair <selva.nair@gmail.com>
     Acked-by: Lev Stipakov <lstipakov@gmail.com>
     Message-Id: <1581309200-27870-1-git-send-email-selva.nair@gmail.com>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19388.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering

Patch

diff --git a/src/openvpnserv/interactive.c b/src/openvpnserv/interactive.c
index 6e72a14..710f9c7 100644
--- a/src/openvpnserv/interactive.c
+++ b/src/openvpnserv/interactive.c
@@ -389,14 +389,13 @@  ReturnOpenvpnOutput(HANDLE pipe, HANDLE ovpn_output, DWORD count, LPHANDLE event
 /*
  * Validate options against a white list. Also check the config_file is
  * inside the config_dir. The white list is defined in validate.c
- * Returns true on success
+ * Returns true on success, false on error with reason set in errmsg.
  */
 static BOOL
-ValidateOptions(HANDLE pipe, const WCHAR *workdir, const WCHAR *options)
+ValidateOptions(HANDLE pipe, const WCHAR *workdir, const WCHAR *options, WCHAR *errmsg, DWORD capacity)
 {
     WCHAR **argv;
     int argc;
-    WCHAR buf[256];
     BOOL ret = FALSE;
     int i;
     const WCHAR *msg1 = L"You have specified a config file location (%s relative to %s)"
@@ -411,8 +410,9 @@  ValidateOptions(HANDLE pipe, const WCHAR *workdir, const WCHAR *options)
 
     if (!argv)
     {
-        ReturnLastError(pipe, L"CommandLineToArgvW");
-        ReturnError(pipe, ERROR_STARTUP_DATA, L"Cannot validate options", 1, &exit_event);
+        openvpn_swprintf(errmsg, capacity,
+	                 L"Cannot validate options: CommandLineToArgvW failed with error = 0x%08x",
+	                 GetLastError());
         goto out;
     }
 
@@ -432,9 +432,8 @@  ValidateOptions(HANDLE pipe, const WCHAR *workdir, const WCHAR *options)
 
         if (!CheckOption(workdir, 2, argv_tmp, &settings))
         {
-            openvpn_swprintf(buf, _countof(buf), msg1, argv[0], workdir,
+            openvpn_swprintf(errmsg, capacity, msg1, argv[0], workdir,
                              settings.ovpn_admin_group);
-            ReturnError(pipe, ERROR_STARTUP_DATA, buf, 1, &exit_event);
         }
         goto out;
     }
@@ -450,15 +449,13 @@  ValidateOptions(HANDLE pipe, const WCHAR *workdir, const WCHAR *options)
         {
             if (wcscmp(L"--config", argv[i]) == 0 && argc-i > 1)
             {
-                openvpn_swprintf(buf, _countof(buf), msg1, argv[i+1], workdir,
+                openvpn_swprintf(errmsg, capacity, msg1, argv[i+1], workdir,
                                  settings.ovpn_admin_group);
-                ReturnError(pipe, ERROR_STARTUP_DATA, buf, 1, &exit_event);
             }
             else
             {
-                openvpn_swprintf(buf, _countof(buf), msg2, argv[i],
+                openvpn_swprintf(errmsg, capacity, msg2, argv[i],
                                  settings.ovpn_admin_group);
-                ReturnError(pipe, ERROR_STARTUP_DATA, buf, 1, &exit_event);
             }
             goto out;
         }
@@ -1487,6 +1484,7 @@  RunOpenvpn(LPVOID p)
     size_t cmdline_size;
     undo_lists_t undo_lists;
     ring_buffer_handles_t ring_buffer_handles;
+    WCHAR errmsg[512] = L"";
 
     SECURITY_ATTRIBUTES inheritable = {
         .nLength = sizeof(inheritable),
@@ -1580,10 +1578,17 @@  RunOpenvpn(LPVOID p)
         goto out;
     }
 
-    /* Check user is authorized or options are white-listed */
-    if (!IsAuthorizedUser(ovpn_user->User.Sid, imp_token, settings.ovpn_admin_group)
-        && !ValidateOptions(pipe, sud.directory, sud.options))
+    /*
+     * Only authorized users are allowed to use any command line options or
+     * have the config file in locations other than the global config directory.
+     *
+     * Check options are white-listed and config is in the global directory
+     * OR user is authorized to run any config.
+     */
+    if (!ValidateOptions(pipe, sud.directory, sud.options, errmsg, _countof(errmsg))
+        && !IsAuthorizedUser(ovpn_user->User.Sid, imp_token, settings.ovpn_admin_group))
     {
+        ReturnError(pipe, ERROR_STARTUP_DATA, errmsg, 1, &exit_event);
         goto out;
     }