asn1: allow '*' in PrintableString.

Although technically incorrect, we want this in order to parse X.509
certificates where a wildcard hostname ("*.example.com") has been put
into a PrintableString.

Fixes #850.

R=rsc
CC=golang-dev
https://golang.org/cl/1615043

src/pkg/asn1/asn1.go

@@ -324,7 +324,11 @@ func isPrintable(b byte) bool {
 		b == ' ' ||
 		b == ':' ||
 		b == '=' ||
-		b == '?'
+		b == '?' ||
+		// This is techincally not allowed in a PrintableString.
+		// However, x509 certificates with wildcard strings don't
+		// always use the correct string type so we permit it.
+		b == '*'
 }
 
 // IA5String

src/pkg/asn1/marshal_test.go

@@ -75,6 +75,7 @@ var marshalTests = []marshalTest{
 	marshalTest{"test", "130474657374"},
 	marshalTest{ia5StringTest{"test"}, "3006160474657374"},
 	marshalTest{printableStringTest{"test"}, "3006130474657374"},
+	marshalTest{printableStringTest{"test*"}, "30071305746573742a"},
 	marshalTest{rawContentsStruct{nil, 64}, "3003020140"},
 	marshalTest{rawContentsStruct{[]byte{0x30, 3, 1, 2, 3}, 64}, "3003010203"},
 	marshalTest{RawValue{Tag: 1, Class: 2, IsCompound: false, Bytes: []byte{1, 2, 3}}, "8103010203"},