From c8e1946f33ee2cf482922ba2398086189faf53f6 Mon Sep 17 00:00:00 2001
From: Adam Langley <agl@golang.org>
Date: Thu, 3 May 2012 16:39:57 -0400
Subject: [PATCH] crypto/x509: fix panic when using unavailable hash function.

crypto.Hash.New() changed to panicking when the hash function isn't
linked in, but crypto/x509 still expects it to return nil.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6175047
---
 src/pkg/crypto/x509/x509.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/pkg/crypto/x509/x509.go b/src/pkg/crypto/x509/x509.go
index 8dae7e7fcf9..c4d85e67f0c 100644
--- a/src/pkg/crypto/x509/x509.go
+++ b/src/pkg/crypto/x509/x509.go
@@ -388,10 +388,10 @@ func (c *Certificate) CheckSignature(algo SignatureAlgorithm, signed, signature
 		return ErrUnsupportedAlgorithm
 	}
 
-	h := hashType.New()
-	if h == nil {
+	if !hashType.Available() {
 		return ErrUnsupportedAlgorithm
 	}
+	h := hashType.New()
 
 	h.Write(signed)
 	digest := h.Sum(nil)