1 files changed, 249 insertions, 0 deletions
diff --git a/src/openvpnserv/validate.c b/src/openvpnserv/validate.c
new file mode 100644
index 0000000..7458d75
--- /dev/null
+++ b/src/openvpnserv/validate.c
@@ -0,0 +1,249 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2016 Selva Nair <selva.nair@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "validate.h"
+
+#include <lmaccess.h>
+#include <shlwapi.h>
+#include <lm.h>
+
+static const WCHAR *white_list[] =
+    {
+       L"auth-retry",
+       L"config",
+       L"log",
+       L"log-append",
+       L"management",
+       L"management-forget-disconnect",
+       L"management-hold",
+       L"management-query-passwords",
+       L"management-query-proxy",
+       L"management-signal",
+       L"management-up-down",
+       L"mute",
+       L"setenv",
+       L"service",
+       L"verb",
+
+       NULL                             /* last value */
+    };
+
+/*
+ * Check workdir\fname is inside config_dir
+ * The logic here is simple: we may reject some valid paths if ..\ is in any of the strings
+ */
+static BOOL
+CheckConfigPath (const WCHAR *workdir, const WCHAR *fname, const settings_t *s)
+{
+    WCHAR tmp[MAX_PATH];
+    const WCHAR *config_file = NULL;
+    const WCHAR *config_dir = NULL;
+
+    /* convert fname to full path */
+    if (PathIsRelativeW (fname) )
+    {
+        snwprintf (tmp, _countof(tmp), L"%s\\%s", workdir, fname);
+        tmp[_countof(tmp)-1] = L'\0';
+        config_file = tmp;
+    }
+    else
+    {
+        config_file = fname;
+    }
+
+#ifdef UNICODE
+    config_dir = s->config_dir;
+#else
+    if (MultiByteToWideChar (CP_UTF8, 0, s->config_dir, -1, widepath, MAX_PATH) == 0)
+    {
+        MsgToEventLog (M_SYSERR, TEXT("Failed to convert config_dir name to WideChar"));
+        return FALSE;
+    }
+    config_dir = widepath;
+#endif
+
+    if (wcsncmp (config_dir, config_file, wcslen(config_dir)) == 0 &&
+        wcsstr (config_file + wcslen(config_dir), L"..") == NULL )
+        return TRUE;
+
+    return FALSE;
+}
+
+
+/*
+ * A simple linear search meant for a small wchar_t *array.
+ * Returns index to the item if found, -1 otherwise.
+ */
+static int
+OptionLookup (const WCHAR *name, const WCHAR *white_list[])
+{
+    int i;
+
+    for (i = 0 ; white_list[i]; i++)
+    {
+        if ( wcscmp(white_list[i], name) == 0 )
+            return i;
+    }
+
+    return -1;
+}
+
+/*
+ * The Administrators group may be localized or renamed by admins.
+ * Get the local name of the group using the SID.
+ */
+static BOOL
+GetBuiltinAdminGroupName (WCHAR *name, DWORD nlen)
+{
+    BOOL b = FALSE;
+    PSID admin_sid = NULL;
+    DWORD sid_size = SECURITY_MAX_SID_SIZE;
+    SID_NAME_USE snu;
+
+    WCHAR domain[MAX_NAME];
+    DWORD dlen = _countof(domain);
+
+    admin_sid = malloc(sid_size);
+    if (!admin_sid)
+        return FALSE;
+
+    b = CreateWellKnownSid(WinBuiltinAdministratorsSid, NULL, admin_sid,  &sid_size);
+    if(b)
+    {
+        b = LookupAccountSidW(NULL, admin_sid, name, &nlen, domain, &dlen, &snu);
+    }
+
+    free (admin_sid);
+
+    return b;
+}
+
+/*
+ * Check whether user is a member of Administrators group or
+ * the group specified in s->ovpn_admin_group
+ */
+BOOL
+IsAuthorizedUser (SID *sid, settings_t *s)
+{
+    LOCALGROUP_USERS_INFO_0 *groups = NULL;
+    DWORD nread;
+    DWORD nmax;
+    WCHAR *tmp = NULL;
+    const WCHAR *admin_group[2];
+    WCHAR username[MAX_NAME];
+    WCHAR domain[MAX_NAME];
+    WCHAR sysadmin_group[MAX_NAME];
+    DWORD err, len = MAX_NAME;
+    int i;
+    BOOL ret = FALSE;
+    SID_NAME_USE sid_type;
+
+    /* Get username */
+    if (!LookupAccountSidW (NULL, sid, username, &len, domain, &len, &sid_type))
+    {
+        MsgToEventLog (M_SYSERR, TEXT("LookupAccountSid"));
+        goto out;
+    }
+
+    /* Get an array of groups the user is member of */
+    err = NetUserGetLocalGroups (NULL, username, 0, LG_INCLUDE_INDIRECT, (LPBYTE *) &groups,
+                                 MAX_PREFERRED_LENGTH, &nread, &nmax);
+    if (err && err != ERROR_MORE_DATA)
+    {
+        SetLastError (err);
+        MsgToEventLog (M_SYSERR, TEXT("NetUserGetLocalGroups"));
+        goto out;
+    }
+
+    if (GetBuiltinAdminGroupName(sysadmin_group, _countof(sysadmin_group)))
+    {
+        admin_group[0] = sysadmin_group;
+    }
+    else
+    {
+        MsgToEventLog (M_SYSERR, TEXT("Failed to get the name of Administrators group. Using the default."));
+        /* use the default value */
+        admin_group[0] = SYSTEM_ADMIN_GROUP;
+    }
+
+#ifdef UNICODE
+    admin_group[1] = s->ovpn_admin_group;
+#else
+    tmp = NULL;
+    len = MultiByteToWideChar (CP_UTF8, 0, s->ovpn_admin_group, -1, NULL, 0);
+    if (len == 0 || (tmp = malloc (len*sizeof(WCHAR))) == NULL)
+    {
+        MsgToEventLog (M_SYSERR, TEXT("Failed to convert admin group name to WideChar"));
+        goto out;
+    }
+    MultiByteToWideChar (CP_UTF8, 0, s->ovpn_admin_group, -1, tmp, len);
+    admin_group[1] = tmp;
+#endif
+
+    /* Check if user's groups include any of the admin groups */
+    for (i = 0; i < nread; i++)
+    {
+        if ( wcscmp (groups[i].lgrui0_name, admin_group[0]) == 0 ||
+             wcscmp (groups[i].lgrui0_name, admin_group[1]) == 0
+           )
+        {
+            MsgToEventLog (M_INFO, TEXT("Authorizing user %s by virtue of membership in group %s"),
+                           username, groups[i].lgrui0_name);
+            ret = TRUE;
+            break;
+        }
+    }
+
+out:
+    if (groups)
+        NetApiBufferFree (groups);
+    free (tmp);
+
+    return ret;
+}
+
+/*
+ * Check whether option argv[0] is white-listed. If argv[0] == "--config",
+ * also check that argv[1], if present, passes CheckConfigPath().
+ * The caller should set argc to the number of valid elements in argv[] array.
+ */
+BOOL
+CheckOption (const WCHAR *workdir, int argc, WCHAR *argv[], const settings_t *s)
+{
+    /* Do not modify argv or *argv -- ideally it should be const WCHAR *const *, but alas...*/
+
+    if ( wcscmp (argv[0], L"--config") == 0            &&
+         argc > 1                                      &&
+         !CheckConfigPath (workdir, argv[1], s)
+       )
+    {
+        return FALSE;
+    }
+
+    /* option name starts at 2 characters from argv[i] */
+    if (OptionLookup (argv[0] + 2, white_list) == -1)  /* not found */
+        return FALSE;
+
+    return TRUE;
+}