Validate token before returning the timestamp

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes to this project will be documented in this file, in reverse chronological order by release.
 
+
+## [2.2.2](https://github.com/tuupola/branca/compare/2.2.1...2.x) - unreleased
+### Fixed
+- Token is now validated before using the `timestamp()` helper ([#19](https://github.com/tuupola/branca-php/pull/19)).
+
+
 ## [2.2.1](https://github.com/tuupola/branca/compare/2.2.0...2.2.1) - 2020-10-29
 ### Fixed
 - Add `SODIUM_CRYPTO_AEAD_XCHACHA20POLY1305_IETF_KEYBYTES` define which is missing from some PHP 7.2 installations ([#12](https://github.com/tuupola/branca-php/pull/12)).

src/Branca.php

@@ -47,6 +47,11 @@ class Branca
      */
     private $key;
 
+    /**
+     * @var int
+     */
+    private $timestamp = null;
+
     /**
      * Nonce used for unit testing only.
      * @var string
@@ -145,6 +150,9 @@ public function decode(string $token, int $ttl = null): string
             throw new \RuntimeException("Invalid token");
         }
 
+        /* Store timestamp value for the helper. */
+        $this->timestamp = $parts["time"];
+
         /* Check for expired token if TTL is set. */
         if (is_integer($ttl)) {
             $future = $parts["time"] + $ttl;
@@ -158,14 +166,10 @@ public function decode(string $token, int $ttl = null): string
 
     public function timestamp(string $token): int
     {
-        $token = (new Base62)->decode($token);
-        $parts = unpack("Cversion/Ntime", $token);
-
-        /* Unpack failed, should not ever happen. */
-        if (false === $parts) {
-            throw new \RuntimeException("Cannot extract token header");
+        if (null === $this->timestamp) {
+            $this->decode($token);
         }
 
-        return $parts["time"];
+        return $this->timestamp;
     }
 }

tests/BrancaTest.php

@@ -224,7 +224,7 @@ public function testShouldThrowWithModifiedNonce()
      * Token was created with time: hex2bin("0757fb00") ie. 123206400
      * 875GH23U0Dr6nHFA63DhOyd9LkYudBkX8RsCTOMz5xoYAMw9sMd5QwcEqLDRnTDHPenOX7nP2trlT
      *
-     * Before base62 encoding the time was modified to: hex2bin("0057fb00")
+     * Before base62 encoding the time was modified to: hex2bin("0057fb00") ie. 5765888
      * 870g1RCk4lW1YInhaU3TP8u2hGtfol16ettLcTOSoA0JIpjCaQRW7tQeP6dQmTvFIB2s6wL5deMXr
      */
     public function testShouldThrowWithModifiedTimestamp()
@@ -482,6 +482,24 @@ public function testShouldThrowWithInvalidNonce()
         $encoded = $branca->encode($payload);
     }
 
+    /**
+     * Timestamp helper should throw is token has been tampered.
+     *
+     * Token was created with time: hex2bin("0757fb00") ie. 123206400
+     * 875GH23U0Dr6nHFA63DhOyd9LkYudBkX8RsCTOMz5xoYAMw9sMd5QwcEqLDRnTDHPenOX7nP2trlT
+     *
+     * Before base62 encoding the time was modified to: hex2bin("0057fb00") ie. 5765888
+     * 870g1RCk4lW1YInhaU3TP8u2hGtfol16ettLcTOSoA0JIpjCaQRW7tQeP6dQmTvFIB2s6wL5deMXr
+     */
+    public function testShouldThrowWithModifiedTimestampWhenReadingTimestamp()
+    {
+        $this->expectException(RuntimeException::class);
+
+        $token = "870g1RCk4lW1YInhaU3TP8u2hGtfol16ettLcTOSoA0JIpjCaQRW7tQeP6dQmTvFIB2s6wL5deMXr";
+        $branca = new Branca("supersecretkeyyoushouldnotcommit");
+        $timestamp = $branca->timestamp($token);
+    }
+
     // public function testShouldThrowWhenTimestampOverflows()
     // {
     //     $this->expectException(RuntimeException::class);