mime/multipart: parse LF-delimited messages, not just CRLF

Against the spec, but appear in the wild.

Fixes #1966

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/4662059

src/pkg/mime/multipart/multipart.go

@@ -24,6 +24,11 @@ import (
 	"regexp"
 )
 
+// TODO(bradfitz): inline these once the compiler can inline them in
+// read-only situation (such as bytes.HasSuffix)
+var lf = []byte("\n")
+var crlf = []byte("\r\n")
+
 var headerRegexp *regexp.Regexp = regexp.MustCompile("^([a-zA-Z0-9\\-]+): *([^\r\n]+)")
 
 var emptyParams = make(map[string]string)
@@ -81,6 +86,7 @@ func NewReader(reader io.Reader, boundary string) *Reader {
 	return &Reader{
 		bufReader: bufio.NewReader(reader),
 
+		nl:               b[:2],
 		nlDashBoundary:   b[:len(b)-2],
 		dashBoundaryDash: b[2:],
 		dashBoundary:     b[2 : len(b)-2],
@@ -180,7 +186,7 @@ type Reader struct {
 	currentPart *Part
 	partsRead   int
 
-	nlDashBoundary, dashBoundaryDash, dashBoundary []byte
+	nl, nlDashBoundary, dashBoundaryDash, dashBoundary []byte
 }
 
 // NextPart returns the next part in the multipart or an error.
@@ -221,11 +227,11 @@ func (mr *Reader) NextPart() (*Part, os.Error) {
 			continue
 		}
 
-		if bytes.Equal(line, []byte("\r\n")) {
-			// Consume the "\r\n" separator between the
-			// body of the previous part and the boundary
-			// line we now expect will follow. (either a
-			// new part or the end boundary)
+		// Consume the "\n" or "\r\n" separator between the
+		// body of the previous part and the boundary line we
+		// now expect will follow. (either a new part or the
+		// end boundary)
+		if bytes.Equal(line, mr.nl) {
 			expectNewPart = true
 			continue
 		}
@@ -245,13 +251,17 @@ func (mr *Reader) isBoundaryDelimiterLine(line []byte) bool {
 	if !bytes.HasPrefix(line, mr.dashBoundary) {
 		return false
 	}
-	if bytes.HasSuffix(line, []byte("\r\n")) {
-		return onlyHorizontalWhitespace(line[len(mr.dashBoundary) : len(line)-2])
+	if bytes.HasSuffix(line, mr.nl) {
+		return onlyHorizontalWhitespace(line[len(mr.dashBoundary) : len(line)-len(mr.nl)])
 	}
 	// Violate the spec and also support newlines without the
 	// carriage return...
-	if bytes.HasSuffix(line, []byte("\n")) {
-		return onlyHorizontalWhitespace(line[len(mr.dashBoundary) : len(line)-1])
+	if mr.partsRead == 0 && bytes.HasSuffix(line, lf) {
+		if onlyHorizontalWhitespace(line[len(mr.dashBoundary) : len(line)-1]) {
+			mr.nl = mr.nl[1:]
+			mr.nlDashBoundary = mr.nlDashBoundary[1:]
+			return true
+		}
 	}
 	return false
 }
@@ -268,5 +278,5 @@ func onlyHorizontalWhitespace(s []byte) bool {
 func hasPrefixThenNewline(s, prefix []byte) bool {
 	return bytes.HasPrefix(s, prefix) &&
 		(len(s) == len(prefix)+1 && s[len(s)-1] == '\n' ||
-			len(s) == len(prefix)+2 && bytes.HasSuffix(s, []byte("\r\n")))
+			len(s) == len(prefix)+2 && bytes.HasSuffix(s, crlf))
 }

src/pkg/mime/multipart/multipart_test.go

@@ -81,7 +81,7 @@ func TestNameAccessors(t *testing.T) {
 
 var longLine = strings.Repeat("\n\n\r\r\r\n\r\000", (1<<20)/8)
 
-func testMultipartBody() string {
+func testMultipartBody(sep string) string {
 	testBody := `
 This is a multi-part message.  This line is ignored.
 --MyBoundary
@@ -112,21 +112,26 @@ never read data
 
 useless trailer
 `
-	testBody = strings.Replace(testBody, "\n", "\r\n", -1)
+	testBody = strings.Replace(testBody, "\n", sep, -1)
 	return strings.Replace(testBody, "[longline]", longLine, 1)
 }
 
 func TestMultipart(t *testing.T) {
-	bodyReader := strings.NewReader(testMultipartBody())
-	testMultipart(t, bodyReader)
+	bodyReader := strings.NewReader(testMultipartBody("\r\n"))
+	testMultipart(t, bodyReader, false)
+}
+
+func TestMultipartOnlyNewlines(t *testing.T) {
+	bodyReader := strings.NewReader(testMultipartBody("\n"))
+	testMultipart(t, bodyReader, true)
 }
 
 func TestMultipartSlowInput(t *testing.T) {
-	bodyReader := strings.NewReader(testMultipartBody())
-	testMultipart(t, &slowReader{bodyReader})
+	bodyReader := strings.NewReader(testMultipartBody("\r\n"))
+	testMultipart(t, &slowReader{bodyReader}, false)
 }
 
-func testMultipart(t *testing.T, r io.Reader) {
+func testMultipart(t *testing.T, r io.Reader, onlyNewlines bool) {
 	reader := NewReader(r, "MyBoundary")
 	buf := new(bytes.Buffer)
 
@@ -149,8 +154,15 @@ func testMultipart(t *testing.T, r io.Reader) {
 	if _, err := io.Copy(buf, part); err != nil {
 		t.Errorf("part 1 copy: %v", err)
 	}
-	expectEq(t, "My value\r\nThe end.",
-		buf.String(), "Value of first part")
+
+	adjustNewlines := func(s string) string {
+		if onlyNewlines {
+			return strings.Replace(s, "\r\n", "\n", -1)
+		}
+		return s
+	}
+
+	expectEq(t, adjustNewlines("My value\r\nThe end."), buf.String(), "Value of first part")
 
 	// Part2
 	part, err = reader.NextPart()
@@ -187,7 +199,7 @@ func testMultipart(t *testing.T, r io.Reader) {
 	if _, err := io.Copy(buf, part); err != nil {
 		t.Errorf("part 3 copy: %v", err)
 	}
-	expectEq(t, "Line 1\r\nLine 2\r\nLine 3 ends in a newline, but just one.\r\n",
+	expectEq(t, adjustNewlines("Line 1\r\nLine 2\r\nLine 3 ends in a newline, but just one.\r\n"),
 		buf.String(), "body of part 3")
 
 	// Part4