crypto/x509: don't fail to parse addition elements in GeneralSubtree.

The GeneralSubtree structure can have additional elements after the name
(minimum and maximum, which are unused). Previously these fields, if
present, would cause a parse error. This change allows trailing data in
the GeneralSubtrees structure.

Change-Id: I6bfb11ec355fa6812810a090c092a5ee0fdeddc3
Reviewed-on: https://go-review.googlesource.com/77333Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/crypto/x509/x509.go

@@ -1222,8 +1222,7 @@ func parseNameConstraintsExtension(out *Certificate, e pkix.Extension) (unhandle
 			var seq, value cryptobyte.String
 			var tag cryptobyte_asn1.Tag
 			if !subtrees.ReadASN1(&seq, cryptobyte_asn1.SEQUENCE) ||
-				!seq.ReadAnyASN1(&value, &tag) ||
-				!seq.Empty() {
+				!seq.ReadAnyASN1(&value, &tag) {
 				return nil, nil, nil, nil, fmt.Errorf("x509: invalid NameConstraints extension")
 			}
 

src/crypto/x509/x509_test.go

@@ -1685,3 +1685,54 @@ func TestBadIPMask(t *testing.T) {
 		t.Fatalf("expected %q in error but got: %s", expected, err)
 	}
 }
+
+const additionalGeneralSubtreePEM = `
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestAdditionFieldsInGeneralSubtree(t *testing.T) {
+	// Very rarely, certificates can include additional fields in the
+	// GeneralSubtree structure. This tests that such certificates can be
+	// parsed.
+	block, _ := pem.Decode([]byte(additionalGeneralSubtreePEM))
+	if _, err := ParseCertificate(block.Bytes); err != nil {
+		t.Fatalf("failed to parse certificate: %s", err)
+	}
+}