crypto/tls: allow certificates and key to be in either order.

X509KeyPair wasn't really supposed to allow the certificate and
key to be in the same file, but it did work if you put the key
first. Since some HTTPS servers support loading keys and certs
like this, this change makes it work in either order.

Fixes #3986.

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/6499103

src/pkg/crypto/tls/tls.go

@@ -146,11 +146,17 @@ func X509KeyPair(certPEMBlock, keyPEMBlock []byte) (cert Certificate, err error)
 		return
 	}
 
-	keyDERBlock, _ := pem.Decode(keyPEMBlock)
+	var keyDERBlock *pem.Block
+	for {
+		keyDERBlock, keyPEMBlock = pem.Decode(keyPEMBlock)
 		if keyDERBlock == nil {
 			err = errors.New("crypto/tls: failed to parse key PEM data")
 			return
 		}
+		if keyDERBlock.Type != "CERTIFICATE" {
+			break
+		}
+	}
 
 	// OpenSSL 0.9.8 generates PKCS#1 private keys by default, while
 	// OpenSSL 1.0.0 generates PKCS#8 keys. We try both.

src/pkg/crypto/tls/tls_test.go

@@ -0,0 +1,47 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tls
+
+import (
+	"testing"
+)
+
+var certPEM = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`
+
+var keyPEM = `-----BEGIN RSA PRIVATE KEY-----
+MIIBOwIBAAJBANLJhPHhITqQbPklG3ibCVxwGMRfp/v4XqhfdQHdcVfHap6NQ5Wo
+k/4xIA+ui35/MmNartNuC+BdZ1tMuVCPFZcCAwEAAQJAEJ2N+zsR0Xn8/Q6twa4G
+6OB1M1WO+k+ztnX/1SvNeWu8D6GImtupLTYgjZcHufykj09jiHmjHx8u8ZZB/o1N
+MQIhAPW+eyZo7ay3lMz1V01WVjNKK9QSn1MJlb06h/LuYv9FAiEA25WPedKgVyCW
+SmUwbPw8fnTcpqDWE3yTO3vKcebqMSsCIBF3UmVue8YU3jybC3NxuXq3wNm34R8T
+xVLHwDXh/6NJAiEAl2oHGGLz64BuAfjKrqwz7qMYr9HCLIe/YsoWq/olzScCIQDi
+D2lWusoe2/nEqfDVVWGWlyJ7yOmqaVm/iNUN9B2N2g==
+-----END RSA PRIVATE KEY-----
+`
+
+func TestX509KeyPair(t *testing.T) {
+	_, err := X509KeyPair([]byte(keyPEM+certPEM), []byte(keyPEM+certPEM))
+	if err != nil {
+		t.Errorf("Failed to load key followed by cert: %s", err)
+	}
+
+	_, err = X509KeyPair([]byte(certPEM+keyPEM), []byte(certPEM+keyPEM))
+	if err != nil {
+		t.Errorf("Failed to load cert followed by key: %s", err)
+		println(err.Error())
+	}
+}