Fix (again) security issue in DBMail driver of password plugin [CVE-2015-2181] (#1490643)

Unify the C program code with the one used by other drivers.

CHANGELOG

@@ -16,6 +16,7 @@ CHANGELOG Roundcube Webmail
 - Fix PHP7 warning "session_start(): Session callback expects true/false return value" (#1490624)
 - Fix XSS issue in SVG images handling (#1490625)
 - Fix missing language name in "Add to Dictionary" request in HTML mode (#1490634)
+- Fix (again) security issue in DBMail driver of password plugin [CVE-2015-2181] (#1490643)
 
 RELEASE 1.2-beta
 ----------------

plugins/password/drivers/dbmail.php

@@ -40,20 +40,9 @@ class rcube_dbmail_password
         $args     = rcmail::get_instance()->config->get('password_dbmail_args', '');
         $command  = "$curdir/chgdbmailusers -c $username -w $password $args";
 
-        if (strlen($command) > 1024) {
-            rcube::raise_error(array(
-                'code' => 600,
-                'type' => 'php',
-                'file' => __FILE__, 'line' => __LINE__,
-                'message' => "Password plugin: The command is too long."
-                ), true, false);
-
-            return PASSWORD_ERROR;
-        }
-
-        exec($command, $output, $returnvalue);
+        exec($command, $output, $return_value);
 
-        if ($returnvalue == 0) {
+        if ($return_value == 0) {
             return PASSWORD_SUCCESS;
         }
         else {

plugins/password/helpers/chgdbmailusers.c

@@ -1,5 +1,4 @@
 #include <stdio.h>
-#include <string.h>
 #include <unistd.h>
 
 // set the UID this script will run as (root user)
@@ -15,27 +14,10 @@
 
 main(int argc, char *argv[])
 {
-  int cnt,rc,cc;
-  char cmnd[1024];
-
-  strcpy(cmnd, CMD);
-
-  if (argc > 1)
-  {
-    for (cnt = 1; cnt < argc; cnt++)
-    {
-      strcat(cmnd, " ");
-      strcat(cmnd, argv[cnt]);
-    }
-  }
-  else
-  {
-    fprintf(stderr, "__ %s:  failed %d  %d\n", argv[0], rc, cc);
-    return 255;
-  }
+  int rc, cc;
 
   cc = setuid(UID);
-  rc = system(cmnd);
+  rc = execvp(CMD, argv);
 
   if ((rc != 0) || (cc != 0))
   {