From dd754283bb36ba2f5731bebc5305703dae9c7811 Mon Sep 17 00:00:00 2001
From: andrewbelcher <andrewbelcher@655282.no-reply.drupal.org>
Date: Tue, 21 Jun 2016 08:56:57 +0100
Subject: [PATCH] Fix zero salt length RSA signatures.

---
 phpseclib/Crypt/RSA.php           |  4 ++--
 tests/Unit/Crypt/RSA/ModeTest.php | 31 +++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/phpseclib/Crypt/RSA.php b/phpseclib/Crypt/RSA.php
index 16d21dcb..ade9b33d 100644
--- a/phpseclib/Crypt/RSA.php
+++ b/phpseclib/Crypt/RSA.php
@@ -2646,7 +2646,7 @@ class Crypt_RSA
         // be output.
 
         $emLen = ($emBits + 1) >> 3; // ie. ceil($emBits / 8)
-        $sLen = $this->sLen ? $this->sLen : $this->hLen;
+        $sLen = $this->sLen !== null ? $this->sLen : $this->hLen;
 
         $mHash = $this->hash->hash($m);
         if ($emLen < $this->hLen + $sLen + 2) {
@@ -2684,7 +2684,7 @@ class Crypt_RSA
         // be output.
 
         $emLen = ($emBits + 1) >> 3; // ie. ceil($emBits / 8);
-        $sLen = $this->sLen ? $this->sLen : $this->hLen;
+        $sLen = $this->sLen !== null ? $this->sLen : $this->hLen;
 
         $mHash = $this->hash->hash($m);
         if ($emLen < $this->hLen + $sLen + 2) {
diff --git a/tests/Unit/Crypt/RSA/ModeTest.php b/tests/Unit/Crypt/RSA/ModeTest.php
index 065a2045..852aa130 100644
--- a/tests/Unit/Crypt/RSA/ModeTest.php
+++ b/tests/Unit/Crypt/RSA/ModeTest.php
@@ -63,4 +63,35 @@ p0GbMJDyR4e9T04ZZwIDAQAB
 
         $this->assertTrue($rsa->verify('zzzz', $sig));
     }
+
+    public function testZeroLengthSalt()
+    {
+        $plaintext = 'a';
+
+        $rsa = new RSA();
+
+        $privatekey = '-----BEGIN RSA PRIVATE KEY-----
+MIICXAIBAAKBgQCqGKukO1De7zhZj6+H0qtjTkVxwTCpvKe4eCZ0FPqri0cb2JZfXJ/DgYSF6vUp
+wmJG8wVQZKjeGcjDOL5UlsuusFncCzWBQ7RKNUSesmQRMSGkVb1/3j+skZ6UtW+5u09lHNsj6tQ5
+1s1SPrCBkedbNf0Tp0GbMJDyR4e9T04ZZwIDAQABAoGAFijko56+qGyN8M0RVyaRAXz++xTqHBLh
+3tx4VgMtrQ+WEgCjhoTwo23KMBAuJGSYnRmoBZM3lMfTKevIkAidPExvYCdm5dYq3XToLkkLv5L2
+pIIVOFMDG+KESnAFV7l2c+cnzRMW0+b6f8mR1CJzZuxVLL6Q02fvLi55/mbSYxECQQDeAw6fiIQX
+GukBI4eMZZt4nscy2o12KyYner3VpoeE+Np2q+Z3pvAMd/aNzQ/W9WaI+NRfcxUJrmfPwIGm63il
+AkEAxCL5HQb2bQr4ByorcMWm/hEP2MZzROV73yF41hPsRC9m66KrheO9HPTJuo3/9s5p+sqGxOlF
+L0NDt4SkosjgGwJAFklyR1uZ/wPJjj611cdBcztlPdqoxssQGnh85BzCj/u3WqBpE2vjvyyvyI5k
+X6zk7S0ljKtt2jny2+00VsBerQJBAJGC1Mg5Oydo5NwD6BiROrPxGo2bpTbu/fhrT8ebHkTz2epl
+U9VQQSQzY1oZMVX8i1m5WUTLPz2yLJIBQVdXqhMCQBGoiuSoSjafUhV7i1cEGpb88h5NBYZzWXGZ
+37sJ5QsW+sJyoNde3xH8vdXhzU7eT82D6X/scw9RZz+/6rCJ4p0=
+-----END RSA PRIVATE KEY-----';
+        $rsa->loadKey($privatekey);
+        $rsa->setSaltLength(0);
+
+        // Check we generate the correct signature.
+        $sig = pack('H*', '0ddfc93548e21d015c0a289a640b3b79aecfdfae045f583c5925b91cc5c399bba181616ad6ae20d9662d966f0eb2fddb550f4733268e34d640f4c9dadcaf25b3c82c42130a5081c6ebad7883331c65b25b6a37ffa7c4233a468dae56180787e2718ed87c48d8d50b72f5850e4a40963b4f36710be250ecef6fe0bb91249261a3');
+        $this->assertEquals($sig, $rsa->sign($plaintext));
+
+        // Check we can verify the signature correctly.
+        $rsa->loadKey($rsa->getPublicKey());
+        $this->assertTrue($rsa->verify($plaintext, $sig));
+    }
 }