Changeset 29382

Timestamp:

08/06/2014 05:25:03 AM (10 years ago)

Author:

nacin

Message:

Constant time for wp_verify_nonce().

Location:

trunk/src/wp-includes

Files:

• compat.php (modified) (1 diff)
• pluggable.php (modified) (2 diffs)

trunk/src/wp-includes/compat.php

@@ -95 +95 @@
     }
 }
+
+if ( ! function_exists( 'hash_equals' ) ) :
+/**
+ * Compare two strings in constant time.
+ *
+ * This function was added in PHP 5.6.
+ * It can leak the length of a string.
+ *
+ * @since 3.9.2
+ *
+ * @param string $a Expected string.
+ * @param string $b Actual string.
+ * @return bool Whether strings are equal.
+ */
+function hash_equals( $a, $b ) {
+    $a_length = strlen( $a );
+    if ( $a_length !== strlen( $b ) ) {
+        return false;
+    }
+    $result = 0;
+
+    // Do not attempt to "optimize" this.
+    for ( $i = 0; $i < $a_length; $i++ ) {
+        $result |= ord( $a[ $i ] ) ^ ord( $b[ $i ] );
+    }
+
+    return $result === 0;
+}
+endif;

trunk/src/wp-includes/pluggable.php

@@ -672 +672 @@
     $hash = hash_hmac( 'sha256', $username . '|' . $expiration . '|' . $token, $key );
 
-    if ( hash_hmac( 'sha256', $hmac, $key ) !== hash_hmac( 'sha256', $hash, $key ) ) {
+    if ( ! hash_equals( $hash, $hmac ) ) {
         /**
          * Fires if a bad authentication cookie hash is encountered.
@@ -1712 +1712 @@
 
     // Nonce generated 0-12 hours ago
-    if ( $nonce === substr( wp_hash( $i . '|' . $action . '|' . $uid . '|' . $token, 'nonce'), -12, 10 ) ) {
+    $expected = substr( wp_hash( $i . '|' . $action . '|' . $uid . '|' . $token, 'nonce'), -12, 10 );
+    if ( hash_equals( $expected, $nonce ) ) {
         return 1;
     }
 
     // Nonce generated 12-24 hours ago
-    if ( $nonce === substr( wp_hash( ( $i - 1 ) . '|' . $action . '|' . $uid . '|' . $token, 'nonce' ), -12, 10 ) ) {
+    $expected = substr( wp_hash( ( $i - 1 ) . '|' . $action . '|' . $uid . '|' . $token, 'nonce' ), -12, 10 );
+    if ( hash_equals( $expected, $nonce ) ) {
         return 2;
     }