1 files changed, 337 insertions, 0 deletions
diff --git a/src/net/http/httputil/dump.go b/src/net/http/httputil/dump.go
new file mode 100644
index 0000000..2edb9bc
--- /dev/null
+++ b/src/net/http/httputil/dump.go
@@ -0,0 +1,337 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package httputil
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// drainBody reads all of b to memory and then returns two equivalent
+// ReadClosers yielding the same bytes.
+//
+// It returns an error if the initial slurp of all bytes fails. It does not attempt
+// to make the returned ReadClosers have identical error-matching behavior.
+func drainBody(b io.ReadCloser) (r1, r2 io.ReadCloser, err error) {
+	if b == nil || b == http.NoBody {
+		// No copying needed. Preserve the magic sentinel meaning of NoBody.
+		return http.NoBody, http.NoBody, nil
+	}
+	var buf bytes.Buffer
+	if _, err = buf.ReadFrom(b); err != nil {
+		return nil, b, err
+	}
+	if err = b.Close(); err != nil {
+		return nil, b, err
+	}
+	return io.NopCloser(&buf), io.NopCloser(bytes.NewReader(buf.Bytes())), nil
+}
+
+// dumpConn is a net.Conn which writes to Writer and reads from Reader
+type dumpConn struct {
+	io.Writer
+	io.Reader
+}
+
+func (c *dumpConn) Close() error                       { return nil }
+func (c *dumpConn) LocalAddr() net.Addr                { return nil }
+func (c *dumpConn) RemoteAddr() net.Addr               { return nil }
+func (c *dumpConn) SetDeadline(t time.Time) error      { return nil }
+func (c *dumpConn) SetReadDeadline(t time.Time) error  { return nil }
+func (c *dumpConn) SetWriteDeadline(t time.Time) error { return nil }
+
+type neverEnding byte
+
+func (b neverEnding) Read(p []byte) (n int, err error) {
+	for i := range p {
+		p[i] = byte(b)
+	}
+	return len(p), nil
+}
+
+// outgoingLength is a copy of the unexported
+// (*http.Request).outgoingLength method.
+func outgoingLength(req *http.Request) int64 {
+	if req.Body == nil || req.Body == http.NoBody {
+		return 0
+	}
+	if req.ContentLength != 0 {
+		return req.ContentLength
+	}
+	return -1
+}
+
+// DumpRequestOut is like [DumpRequest] but for outgoing client requests. It
+// includes any headers that the standard [http.Transport] adds, such as
+// User-Agent.
+func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
+	save := req.Body
+	dummyBody := false
+	if !body {
+		contentLength := outgoingLength(req)
+		if contentLength != 0 {
+			req.Body = io.NopCloser(io.LimitReader(neverEnding('x'), contentLength))
+			dummyBody = true
+		}
+	} else {
+		var err error
+		save, req.Body, err = drainBody(req.Body)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Since we're using the actual Transport code to write the request,
+	// switch to http so the Transport doesn't try to do an SSL
+	// negotiation with our dumpConn and its bytes.Buffer & pipe.
+	// The wire format for https and http are the same, anyway.
+	reqSend := req
+	if req.URL.Scheme == "https" {
+		reqSend = new(http.Request)
+		*reqSend = *req
+		reqSend.URL = new(url.URL)
+		*reqSend.URL = *req.URL
+		reqSend.URL.Scheme = "http"
+	}
+
+	// Use the actual Transport code to record what we would send
+	// on the wire, but not using TCP.  Use a Transport with a
+	// custom dialer that returns a fake net.Conn that waits
+	// for the full input (and recording it), and then responds
+	// with a dummy response.
+	var buf bytes.Buffer // records the output
+	pr, pw := io.Pipe()
+	defer pr.Close()
+	defer pw.Close()
+	dr := &delegateReader{c: make(chan io.Reader)}
+
+	t := &http.Transport{
+		Dial: func(net, addr string) (net.Conn, error) {
+			return &dumpConn{io.MultiWriter(&buf, pw), dr}, nil
+		},
+	}
+	defer t.CloseIdleConnections()
+
+	// We need this channel to ensure that the reader
+	// goroutine exits if t.RoundTrip returns an error.
+	// See golang.org/issue/32571.
+	quitReadCh := make(chan struct{})
+	// Wait for the request before replying with a dummy response:
+	go func() {
+		req, err := http.ReadRequest(bufio.NewReader(pr))
+		if err == nil {
+			// Ensure all the body is read; otherwise
+			// we'll get a partial dump.
+			io.Copy(io.Discard, req.Body)
+			req.Body.Close()
+		}
+		select {
+		case dr.c <- strings.NewReader("HTTP/1.1 204 No Content\r\nConnection: close\r\n\r\n"):
+		case <-quitReadCh:
+			// Ensure delegateReader.Read doesn't block forever if we get an error.
+			close(dr.c)
+		}
+	}()
+
+	_, err := t.RoundTrip(reqSend)
+
+	req.Body = save
+	if err != nil {
+		pw.Close()
+		dr.err = err
+		close(quitReadCh)
+		return nil, err
+	}
+	dump := buf.Bytes()
+
+	// If we used a dummy body above, remove it now.
+	// TODO: if the req.ContentLength is large, we allocate memory
+	// unnecessarily just to slice it off here. But this is just
+	// a debug function, so this is acceptable for now. We could
+	// discard the body earlier if this matters.
+	if dummyBody {
+		if i := bytes.Index(dump, []byte("\r\n\r\n")); i >= 0 {
+			dump = dump[:i+4]
+		}
+	}
+	return dump, nil
+}
+
+// delegateReader is a reader that delegates to another reader,
+// once it arrives on a channel.
+type delegateReader struct {
+	c   chan io.Reader
+	err error     // only used if r is nil and c is closed.
+	r   io.Reader // nil until received from c
+}
+
+func (r *delegateReader) Read(p []byte) (int, error) {
+	if r.r == nil {
+		var ok bool
+		if r.r, ok = <-r.c; !ok {
+			return 0, r.err
+		}
+	}
+	return r.r.Read(p)
+}
+
+// Return value if nonempty, def otherwise.
+func valueOrDefault(value, def string) string {
+	if value != "" {
+		return value
+	}
+	return def
+}
+
+var reqWriteExcludeHeaderDump = map[string]bool{
+	"Host":              true, // not in Header map anyway
+	"Transfer-Encoding": true,
+	"Trailer":           true,
+}
+
+// DumpRequest returns the given request in its HTTP/1.x wire
+// representation. It should only be used by servers to debug client
+// requests. The returned representation is an approximation only;
+// some details of the initial request are lost while parsing it into
+// an [http.Request]. In particular, the order and case of header field
+// names are lost. The order of values in multi-valued headers is kept
+// intact. HTTP/2 requests are dumped in HTTP/1.x form, not in their
+// original binary representations.
+//
+// If body is true, DumpRequest also returns the body. To do so, it
+// consumes req.Body and then replaces it with a new [io.ReadCloser]
+// that yields the same bytes. If DumpRequest returns an error,
+// the state of req is undefined.
+//
+// The documentation for [http.Request.Write] details which fields
+// of req are included in the dump.
+func DumpRequest(req *http.Request, body bool) ([]byte, error) {
+	var err error
+	save := req.Body
+	if !body || req.Body == nil {
+		req.Body = nil
+	} else {
+		save, req.Body, err = drainBody(req.Body)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	var b bytes.Buffer
+
+	// By default, print out the unmodified req.RequestURI, which
+	// is always set for incoming server requests. But because we
+	// previously used req.URL.RequestURI and the docs weren't
+	// always so clear about when to use DumpRequest vs
+	// DumpRequestOut, fall back to the old way if the caller
+	// provides a non-server Request.
+	reqURI := req.RequestURI
+	if reqURI == "" {
+		reqURI = req.URL.RequestURI()
+	}
+
+	fmt.Fprintf(&b, "%s %s HTTP/%d.%d\r\n", valueOrDefault(req.Method, "GET"),
+		reqURI, req.ProtoMajor, req.ProtoMinor)
+
+	absRequestURI := strings.HasPrefix(req.RequestURI, "http://") || strings.HasPrefix(req.RequestURI, "https://")
+	if !absRequestURI {
+		host := req.Host
+		if host == "" && req.URL != nil {
+			host = req.URL.Host
+		}
+		if host != "" {
+			fmt.Fprintf(&b, "Host: %s\r\n", host)
+		}
+	}
+
+	chunked := len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked"
+	if len(req.TransferEncoding) > 0 {
+		fmt.Fprintf(&b, "Transfer-Encoding: %s\r\n", strings.Join(req.TransferEncoding, ","))
+	}
+
+	err = req.Header.WriteSubset(&b, reqWriteExcludeHeaderDump)
+	if err != nil {
+		return nil, err
+	}
+
+	io.WriteString(&b, "\r\n")
+
+	if req.Body != nil {
+		var dest io.Writer = &b
+		if chunked {
+			dest = NewChunkedWriter(dest)
+		}
+		_, err = io.Copy(dest, req.Body)
+		if chunked {
+			dest.(io.Closer).Close()
+			io.WriteString(&b, "\r\n")
+		}
+	}
+
+	req.Body = save
+	if err != nil {
+		return nil, err
+	}
+	return b.Bytes(), nil
+}
+
+// errNoBody is a sentinel error value used by failureToReadBody so we
+// can detect that the lack of body was intentional.
+var errNoBody = errors.New("sentinel error value")
+
+// failureToReadBody is an io.ReadCloser that just returns errNoBody on
+// Read. It's swapped in when we don't actually want to consume
+// the body, but need a non-nil one, and want to distinguish the
+// error from reading the dummy body.
+type failureToReadBody struct{}
+
+func (failureToReadBody) Read([]byte) (int, error) { return 0, errNoBody }
+func (failureToReadBody) Close() error             { return nil }
+
+// emptyBody is an instance of empty reader.
+var emptyBody = io.NopCloser(strings.NewReader(""))
+
+// DumpResponse is like DumpRequest but dumps a response.
+func DumpResponse(resp *http.Response, body bool) ([]byte, error) {
+	var b bytes.Buffer
+	var err error
+	save := resp.Body
+	savecl := resp.ContentLength
+
+	if !body {
+		// For content length of zero. Make sure the body is an empty
+		// reader, instead of returning error through failureToReadBody{}.
+		if resp.ContentLength == 0 {
+			resp.Body = emptyBody
+		} else {
+			resp.Body = failureToReadBody{}
+		}
+	} else if resp.Body == nil {
+		resp.Body = emptyBody
+	} else {
+		save, resp.Body, err = drainBody(resp.Body)
+		if err != nil {
+			return nil, err
+		}
+	}
+	err = resp.Write(&b)
+	if err == errNoBody {
+		err = nil
+	}
+	resp.Body = save
+	resp.ContentLength = savecl
+	if err != nil {
+		return nil, err
+	}
+	return b.Bytes(), nil
+}