http: fix scheme-relative URL parsing; add ParseRequestURL

Also adds some tests for Issue 900 which was the reason
the current URL parsing is broken.  (the previous fix
was wrong)

R=rsc, adg, dangabrad, bradfitzwork
CC=golang-dev
https://golang.org/cl/3910042

src/pkg/http/readrequest_test.go

@@ -69,6 +69,41 @@ var reqTests = []reqTest{
 
 		"abcdef\n",
 	},
+
+	// Tests that we don't parse a path that looks like a
+	// scheme-relative URI as a scheme-relative URI.
+	{
+		"GET //user@host/is/actually/a/path/ HTTP/1.1\r\n" +
+			"Host: test\r\n\r\n",
+
+		Request{
+			Method: "GET",
+			RawURL: "//user@host/is/actually/a/path/",
+			URL: &URL{
+				Raw:          "//user@host/is/actually/a/path/",
+				Scheme:       "",
+				RawPath:      "//user@host/is/actually/a/path/",
+				RawAuthority: "",
+				RawUserinfo:  "",
+				Host:         "",
+				Path:         "//user@host/is/actually/a/path/",
+				RawQuery:     "",
+				Fragment:     "",
+			},
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        map[string]string{},
+			Close:         false,
+			ContentLength: -1,
+			Host:          "test",
+			Referer:       "",
+			UserAgent:     "",
+			Form:          map[string][]string{},
+		},
+
+		"",
+	},
 }
 
 func TestReadRequest(t *testing.T) {

src/pkg/http/request.go

@@ -504,7 +504,7 @@ func ReadRequest(b *bufio.Reader) (req *Request, err os.Error) {
 		return nil, &badStringError{"malformed HTTP version", req.Proto}
 	}
 
-	if req.URL, err = ParseURL(req.RawURL); err != nil {
+	if req.URL, err = ParseRequestURL(req.RawURL); err != nil {
 		return nil, err
 	}
 

src/pkg/http/serve_test.go

@@ -7,7 +7,9 @@
 package http
 
 import (
+	"bufio"
 	"bytes"
+	"io"
 	"os"
 	"net"
 	"testing"
@@ -133,3 +135,86 @@ func TestConsumingBodyOnNextConn(t *testing.T) {
 		t.Errorf("Serve returned %q; expected EOF", serveerr)
 	}
 }
+
+type responseWriterMethodCall struct {
+	method                 string
+	headerKey, headerValue string // if method == "SetHeader"
+	bytesWritten           []byte // if method == "Write"
+	responseCode           int    // if method == "WriteHeader"
+}
+
+type recordingResponseWriter struct {
+	log []*responseWriterMethodCall
+}
+
+func (rw *recordingResponseWriter) RemoteAddr() string {
+	return "1.2.3.4"
+}
+
+func (rw *recordingResponseWriter) UsingTLS() bool {
+	return false
+}
+
+func (rw *recordingResponseWriter) SetHeader(k, v string) {
+	rw.log = append(rw.log, &responseWriterMethodCall{method: "SetHeader", headerKey: k, headerValue: v})
+}
+
+func (rw *recordingResponseWriter) Write(buf []byte) (int, os.Error) {
+	rw.log = append(rw.log, &responseWriterMethodCall{method: "Write", bytesWritten: buf})
+	return len(buf), nil
+}
+
+func (rw *recordingResponseWriter) WriteHeader(code int) {
+	rw.log = append(rw.log, &responseWriterMethodCall{method: "WriteHeader", responseCode: code})
+}
+
+func (rw *recordingResponseWriter) Flush() {
+	rw.log = append(rw.log, &responseWriterMethodCall{method: "Flush"})
+}
+
+func (rw *recordingResponseWriter) Hijack() (io.ReadWriteCloser, *bufio.ReadWriter, os.Error) {
+	panic("Not supported")
+}
+
+// Tests for http://code.google.com/p/go/issues/detail?id=900
+func TestMuxRedirectLeadingSlashes(t *testing.T) {
+	paths := []string{"//foo.txt", "///foo.txt", "/../../foo.txt"}
+	for _, path := range paths {
+		req, err := ReadRequest(bufio.NewReader(bytes.NewBufferString("GET " + path + " HTTP/1.1\r\nHost: test\r\n\r\n")))
+		if err != nil {
+			t.Errorf("%s", err)
+		}
+		mux := NewServeMux()
+		resp := new(recordingResponseWriter)
+		resp.log = make([]*responseWriterMethodCall, 0)
+
+		mux.ServeHTTP(resp, req)
+
+		dumpLog := func() {
+			t.Logf("For path %q:", path)
+			for _, call := range resp.log {
+				t.Logf("Got call: %s, header=%s, value=%s, buf=%q, code=%d", call.method,
+					call.headerKey, call.headerValue, call.bytesWritten, call.responseCode)
+			}
+		}
+
+		if len(resp.log) != 2 {
+			dumpLog()
+			t.Errorf("expected 2 calls to response writer; got %d", len(resp.log))
+			return
+		}
+
+		if resp.log[0].method != "SetHeader" ||
+			resp.log[0].headerKey != "Location" || resp.log[0].headerValue != "/foo.txt" {
+			dumpLog()
+			t.Errorf("Expected SetHeader of Location to /foo.txt")
+			return
+		}
+
+		if resp.log[1].method != "WriteHeader" || resp.log[1].responseCode != StatusMovedPermanently {
+			dumpLog()
+			t.Errorf("Expected WriteHeader of StatusMovedPermanently")
+			return
+		}
+	}
+}

src/pkg/http/url.go

@@ -385,7 +385,25 @@ func split(s string, c byte, cutc bool) (string, string) {
 // ParseURL parses rawurl into a URL structure.
 // The string rawurl is assumed not to have a #fragment suffix.
 // (Web browsers strip #fragment before sending the URL to a web server.)
+// The rawurl may be relative or absolute.
 func ParseURL(rawurl string) (url *URL, err os.Error) {
+	return parseURL(rawurl, false)
+}
+
+// ParseRequestURL parses rawurl into a URL structure.  It assumes that
+// rawurl was received from an HTTP request, so the rawurl is interpreted
+// only as an absolute URI or an absolute path.
+// The string rawurl is assumed not to have a #fragment suffix.
+// (Web browsers strip #fragment before sending the URL to a web server.)
+func ParseRequestURL(rawurl string) (url *URL, err os.Error) {
+	return parseURL(rawurl, true)
+}
+
+// parseURL parses a URL from a string in one of two contexts.  If
+// viaRequest is true, the URL is assumed to have arrived via an HTTP request,
+// in which case only absolute URLs or path-absolute relative URLs are allowed.
+// If viaRequest is false, all forms of relative URLs are allowed.
+func parseURL(rawurl string, viaRequest bool) (url *URL, err os.Error) {
 	if rawurl == "" {
 		err = os.ErrorString("empty url")
 		goto Error
@@ -400,7 +418,9 @@ func ParseURL(rawurl string) (url *URL, err os.Error) {
 		goto Error
 	}
 
-	if url.Scheme != "" && (len(path) == 0 || path[0] != '/') {
+	leadingSlash := strings.HasPrefix(path, "/")
+
+	if url.Scheme != "" && !leadingSlash {
 		// RFC 2396:
 		// Absolute URI (has scheme) with non-rooted path
 		// is uninterpreted.  It doesn't even have a ?query.
@@ -412,6 +432,11 @@ func ParseURL(rawurl string) (url *URL, err os.Error) {
 		}
 		url.OpaquePath = true
 	} else {
+		if viaRequest && !leadingSlash {
+			err = os.ErrorString("invalid URI for request")
+			goto Error
+		}
+
 		// Split off query before parsing path further.
 		url.RawPath = path
 		path, query := split(path, '?', false)
@@ -420,7 +445,8 @@ func ParseURL(rawurl string) (url *URL, err os.Error) {
 		}
 
 		// Maybe path is //authority/path
-		if url.Scheme != "" && len(path) > 2 && path[0:2] == "//" {
+		if (url.Scheme != "" || !viaRequest) &&
+			strings.HasPrefix(path, "//") && !strings.HasPrefix(path, "///") {
 			url.RawAuthority, path = split(path[2:], '/', false)
 			url.RawPath = url.RawPath[2+len(url.RawAuthority):]
 		}

src/pkg/http/url_test.go

@@ -188,14 +188,48 @@ var urltests = []URLTest{
 		},
 		"",
 	},
-	// leading // without scheme shouldn't create an authority
+	// leading // without scheme should create an authority
 	{
 		"//foo",
 		&URL{
+			RawAuthority: "foo",
 			Raw:          "//foo",
+			Host:         "foo",
 			Scheme:       "",
-			RawPath: "//foo",
+			RawPath:      "",
-			Path:    "//foo",
+			Path:         "",
+		},
+		"",
+	},
+	// leading // without scheme, with userinfo, path, and query
+	{
+		"//user@foo/path?a=b",
+		&URL{
+			Raw:          "//user@foo/path?a=b",
+			RawAuthority: "user@foo",
+			RawUserinfo:  "user",
+			Scheme:       "",
+			RawPath:      "/path?a=b",
+			Path:         "/path",
+			RawQuery:     "a=b",
+			Host:         "foo",
+		},
+		"",
+	},
+	// Three leading slashes isn't an authority, but doesn't return an error.
+	// (We can't return an error, as this code is also used via
+	// ServeHTTP -> ReadRequest -> ParseURL, which is arguably a
+	// different URL parsing context, but currently shares the
+	// same codepath)
+	{
+		"///threeslashes",
+		&URL{
+			RawAuthority: "",
+			Raw:          "///threeslashes",
+			Host:         "",
+			Scheme:       "",
+			RawPath:      "///threeslashes",
+			Path:         "///threeslashes",
 		},
 		"",
 	},
@@ -272,7 +306,7 @@ var urlfragtests = []URLTest{
 
 // more useful string for debugging than fmt's struct printer
 func ufmt(u *URL) string {
-	return fmt.Sprintf("%q, %q, %q, %q, %q, %q, %q, %q, %q",
+	return fmt.Sprintf("raw=%q, scheme=%q, rawpath=%q, auth=%q, userinfo=%q, host=%q, path=%q, rawq=%q, frag=%q",
 		u.Raw, u.Scheme, u.RawPath, u.RawAuthority, u.RawUserinfo,
 		u.Host, u.Path, u.RawQuery, u.Fragment)
 }
@@ -301,6 +335,40 @@ func TestParseURLReference(t *testing.T) {
 	DoTest(t, ParseURLReference, "ParseURLReference", urlfragtests)
 }
 
+const pathThatLooksSchemeRelative = "//not.a.user@not.a.host/just/a/path"
+
+var parseRequestUrlTests = []struct {
+	url           string
+	expectedValid bool
+}{
+	{"http://foo.com", true},
+	{"http://foo.com/", true},
+	{"http://foo.com/path", true},
+	{"/", true},
+	{pathThatLooksSchemeRelative, true},
+	{"//not.a.user@%66%6f%6f.com/just/a/path/also", true},
+	{"foo.html", false},
+	{"../dir/", false},
+}
+
+func TestParseRequestURL(t *testing.T) {
+	for _, test := range parseRequestUrlTests {
+		_, err := ParseRequestURL(test.url)
+		valid := err == nil
+		if valid != test.expectedValid {
+			t.Errorf("Expected valid=%v for %q; got %v", test.expectedValid, test.url, valid)
+		}
+	}
+
+	url, err := ParseRequestURL(pathThatLooksSchemeRelative)
+	if err != nil {
+		t.Fatalf("Unexpected error %v", err)
+	}
+	if url.Path != pathThatLooksSchemeRelative {
+		t.Errorf("Expected path %q; got %q", pathThatLooksSchemeRelative, url.Path)
+	}
+}
+
 func DoTestString(t *testing.T, parse func(string) (*URL, os.Error), name string, tests []URLTest) {
 	for _, tt := range tests {
 		u, err := parse(tt.in)