Bug 1567186: More thorough checking for passwords in stacktraces

Rather than having an increasing list of specific parameters
that we know to have passwords, this patch censors the content
of any parameter with a name that contains the string "password"
or "pw".

behatnotneeded: Can't test with Behat

Change-Id: Ifaa2ec10cf749c173b1a8d0928c6cc052124a83f

htdocs/lib/errors.php

@@ -294,12 +294,10 @@ function log_build_backtrace($backtrace) {
     //array_shift($backtrace);
 
     foreach ($backtrace as $bt) {
-        // Change password in args for LiveUser object to 8 stars
-        if (!empty($bt['class']) && ($bt['class'] == 'LiveUser' || $bt['class'] == 'AuthLdap')) {
-            if (!empty($bt['args'][1])) {
-                $bt['args'][1] = str_repeat('*', 8);
-            }
-        }
+
+        // Blank out any passwords from the logs
+        censor_password_parameters($bt);
+
         $bt['file']  = (isset($bt['file'])) ? $bt['file'] : 'Unknown';
         $bt['line']  = (isset($bt['line'])) ? $bt['line'] : 0;
         $bt['class'] = (isset($bt['class'])) ? $bt['class'] : '';
@@ -366,6 +364,58 @@ function log_build_backtrace($backtrace) {
     return array($textmessage, $htmlmessage);
 }
 
+
+/**
+ * Detects whether a backtrace line contains a function call with password parameters in it.
+ * Replaces the value of any password params with "********" so that passwords won't be
+ * printed in the logs or error messages.
+ *
+ * This function assumes any parameter with a name that contains "password" or "pw"
+ * is a password.
+ *
+ * @param array &$backtraceline An entry in the array returned by debug_backtrace()
+ * @return void
+ */
+function censor_password_parameters(&$backtraceline) {
+    if (isset($backtraceline['function'])) {
+        try {
+            if (isset($backtraceline['class'])) {
+                $refClass = new ReflectionClass($backtraceline['class']);
+                $refFunc = $refClass->getMethod($backtraceline['function']);
+            }
+            else {
+                // Function-like "language constructs" such as "require" and "echo"
+                // are listed as a function by debug_backtrace(), but can't be
+                // reflected.
+                if (!function_exists($backtraceline['function'])) {
+                    return;
+                }
+                $refFunc = new ReflectionFunction($backtraceline['function']);
+            }
+
+            foreach ($refFunc->getParameters() as $param) {
+                $name = strtolower($param->getName());
+                if (
+                    strpos($name, 'password') !== false
+                    || strpos($name, 'pw') !== false
+                ) {
+                    $i = $param->getPosition();
+                    if (isset($backtraceline['args'][$i])) {
+                        $backtraceline['args'][$i] = '********';
+                    }
+                }
+            }
+            return;
+        }
+        catch (ReflectionException $re) {
+            // Don't want a failure here to totally prevent logging.
+            return;
+        }
+    }
+
+    return;
+}
+
 /**
  * Ends the script with an informational message
  *