Check gzip strings for NUL elements, since they are NUL-terminated

on the wire.

R=rsc
CC=golang-dev
https://golang.org/cl/194146

src/pkg/compress/gzip/gunzip.go

@@ -104,7 +104,7 @@ func (z *Inflater) readString() (string, os.Error) {
 			return "", err
 		}
 		if z.buf[i] == 0 {
-			// GZIP (RFC 1952) specifies that strings are null-terminated ISO 8859-1 (Latin-1).
+			// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
 			// TODO(nigeltao): Convert from ISO 8859-1 (Latin-1) to UTF-8.
 			return string(z.buf[0:i]), nil
 		}

src/pkg/compress/gzip/gzip.go

@@ -85,11 +85,11 @@ func (z *Deflater) writeBytes(b []byte) os.Error {
 
 // writeString writes a string (in ISO 8859-1 (Latin-1) format) to z.w.
 func (z *Deflater) writeString(s string) os.Error {
-	// GZIP (RFC 1952) specifies that strings are null-terminated ISO 8859-1 (Latin-1).
+	// GZIP (RFC 1952) specifies that strings are NUL-terminated ISO 8859-1 (Latin-1).
 	// TODO(nigeltao): Convert from UTF-8 to ISO 8859-1 (Latin-1).
 	for _, v := range s {
-		if v > 0x7f {
-			return os.NewError("gzip.Write: Comment/Name character code was outside the 0x00-0x7f range")
+		if v == 0 || v > 0x7f {
+			return os.NewError("gzip.Write: non-ASCII header string")
 		}
 	}
 	_, err := io.WriteString(z.w, s)