From 3dedcd16408cd93ca4fc3456163d40fa67367278 Mon Sep 17 00:00:00 2001 From: Brad Fitzpatrick Date: Fri, 17 Dec 2021 12:40:24 -0800 Subject: [PATCH] logpolicy, ipn/ipnserver: connect to logtail via tailscaled when needed This is for use by the Windows GUI client to log via when an exit node is in use, so the logs don't go out via the exit node and instead go directly, like tailscaled's. The dialer tried to do that in the unprivileged GUI by binding to a specific interface, but the "Internet Kill Switch" installed by tailscaled for exit nodes precludes that from working and instead the GUI fails to dial out. So, go through tailscaled (with a CONNECT request) instead. Fixes tailscale/corp#3169 Change-Id: I17a8efdc1d4b8fed53a29d1c19995592b651b215 Signed-off-by: Brad Fitzpatrick --- cmd/tailscaled/depaware.txt | 2 +- ipn/ipnserver/proxyconnect.go | 74 +++++++++++++++++++++++++++++++++++ ipn/ipnserver/server.go | 16 ++++++++ logpolicy/logpolicy.go | 30 ++++++++++++++ version/prop.go | 10 +++++ 5 files changed, 131 insertions(+), 1 deletion(-) create mode 100644 ipn/ipnserver/proxyconnect.go diff --git a/cmd/tailscaled/depaware.txt b/cmd/tailscaled/depaware.txt index d30960342..c5d4ed01f 100644 --- a/cmd/tailscaled/depaware.txt +++ b/cmd/tailscaled/depaware.txt @@ -183,7 +183,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de tailscale.com/kube from tailscale.com/ipn tailscale.com/log/filelogger from tailscale.com/logpolicy tailscale.com/log/logheap from tailscale.com/control/controlclient - tailscale.com/logpolicy from tailscale.com/cmd/tailscaled + tailscale.com/logpolicy from tailscale.com/cmd/tailscaled+ tailscale.com/logtail from tailscale.com/logpolicy+ tailscale.com/logtail/backoff from tailscale.com/cmd/tailscaled+ tailscale.com/logtail/filch from tailscale.com/logpolicy diff --git a/ipn/ipnserver/proxyconnect.go b/ipn/ipnserver/proxyconnect.go new file mode 100644 index 000000000..ead1eb794 --- /dev/null +++ b/ipn/ipnserver/proxyconnect.go @@ -0,0 +1,74 @@ +// Copyright (c) 2021 Tailscale Inc & 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 ipnserver + +import ( + "bufio" + "context" + "io" + "net" + "net/http" + "time" + + "tailscale.com/logpolicy" + "tailscale.com/types/logger" +) + +// handleProxyConnectConn handles a CONNECT request to +// log.tailscale.io (or whatever the configured log server is). This +// is intended for use by the Windows GUI client to log via when an +// exit node is in use, so the logs don't go out via the exit node and +// instead go directly, like tailscaled's. The dialer tried to do that +// in the unprivileged GUI by binding to a specific interface, but the +// "Internet Kill Switch" installed by tailscaled for exit nodes +// precludes that from working and instead the GUI fails to dial out. +// So, go through tailscaled (with a CONNECT request) instead. +func (s *Server) handleProxyConnectConn(ctx context.Context, br *bufio.Reader, c net.Conn, logf logger.Logf) { + defer c.Close() + + c.SetReadDeadline(time.Now().Add(5 * time.Second)) // should be long enough to send the HTTP headers + req, err := http.ReadRequest(br) + if err != nil { + logf("ReadRequest: %v", err) + return + } + c.SetReadDeadline(time.Time{}) + + if req.Method != "CONNECT" { + logf("ReadRequest: unexpected method %q, not CONNECT", req.Method) + return + } + + hostPort := req.RequestURI + logHost := logpolicy.LogHost() + allowed := net.JoinHostPort(logHost, "443") + if hostPort != allowed { + logf("invalid CONNECT target %q; want %q", hostPort, allowed) + io.WriteString(c, "HTTP/1.1 403 Forbidden\r\n\r\nBad CONNECT target.\n") + return + } + + tr := logpolicy.NewLogtailTransport(logHost) + back, err := tr.DialContext(ctx, "tcp", hostPort) + if err != nil { + logf("error CONNECT dialing %v: %v", hostPort, err) + io.WriteString(c, "HTTP/1.1 502 Fail\r\n\r\nConnect failure.\n") + return + } + defer back.Close() + + io.WriteString(c, "HTTP/1.1 200 OK\r\n\r\n") + + errc := make(chan error, 2) + go func() { + _, err := io.Copy(c, back) + errc <- err + }() + go func() { + _, err := io.Copy(back, br) + errc <- err + }() + <-errc +} diff --git a/ipn/ipnserver/server.go b/ipn/ipnserver/server.go index 802a0a0fd..652911bd5 100644 --- a/ipn/ipnserver/server.go +++ b/ipn/ipnserver/server.go @@ -238,12 +238,28 @@ func bufferHasHTTPRequest(br *bufio.Reader) bool { mem.Contains(mem.B(peek), mem.S(" HTTP/")) } +// bufferIsConnect reports whether br looks like it's likely an HTTP +// CONNECT request. +// +// Invariant: br has already had at least 4 bytes Peek'ed. +func bufferIsConnect(br *bufio.Reader) bool { + peek, _ := br.Peek(br.Buffered()) + return mem.HasPrefix(mem.B(peek), mem.S("CONN")) +} + func (s *Server) serveConn(ctx context.Context, c net.Conn, logf logger.Logf) { // First see if it's an HTTP request. br := bufio.NewReader(c) c.SetReadDeadline(time.Now().Add(time.Second)) br.Peek(4) c.SetReadDeadline(time.Time{}) + + // Handle logtail CONNECT requests early. (See docs on handleProxyConnectConn) + if bufferIsConnect(br) { + s.handleProxyConnectConn(ctx, br, c, logf) + return + } + isHTTPReq := bufferHasHTTPRequest(br) ci, err := s.addConn(c, isHTTPReq) diff --git a/logpolicy/logpolicy.go b/logpolicy/logpolicy.go index c67557697..8bc0675f5 100644 --- a/logpolicy/logpolicy.go +++ b/logpolicy/logpolicy.go @@ -8,10 +8,12 @@ package logpolicy import ( + "bufio" "bytes" "context" "crypto/tls" "encoding/json" + "errors" "fmt" "io" "io/ioutil" @@ -40,6 +42,7 @@ import ( "tailscale.com/net/tlsdial" "tailscale.com/net/tshttpproxy" "tailscale.com/paths" + "tailscale.com/safesocket" "tailscale.com/smallzstd" "tailscale.com/types/logger" "tailscale.com/util/clientmetric" @@ -67,6 +70,15 @@ func getLogTarget() string { return getLogTargetOnce.v } +// LogHost returns the hostname only (without port) of the configured +// logtail server, or the default. +func LogHost() string { + if v := getLogTarget(); v != "" { + return v + } + return logtail.DefaultHost +} + // Config represents an instance of logs in a collection. type Config struct { Collection string @@ -616,6 +628,24 @@ func NewLogtailTransport(host string) *http.Transport { return c, nil } + if version.IsWindowsGUI() && strings.HasPrefix(netw, "tcp") { + if c, err := safesocket.Connect(safesocket.DefaultConnectionStrategy("")); err == nil { + fmt.Fprintf(c, "CONNECT %s HTTP/1.0\r\n\r\n", addr) + br := bufio.NewReader(c) + res, err := http.ReadResponse(br, nil) + if err == nil && res.StatusCode != 200 { + err = errors.New(res.Status) + } + if err != nil { + log.Printf("logtail: CONNECT response from tailscaled: %v", err) + c.Close() + } else { + log.Printf("logtail: connected via tailscaled") + return c, nil + } + } + } + // If we failed to dial, try again with bootstrap DNS. log.Printf("logtail: dial %q failed: %v (in %v), trying bootstrap...", addr, err, d) dnsCache := &dnscache.Resolver{ diff --git a/version/prop.go b/version/prop.go index 1d39ab589..fcb095062 100644 --- a/version/prop.go +++ b/version/prop.go @@ -62,3 +62,13 @@ func IsMacSysExt() bool { isMacSysExt.Store(v) return v } + +// IsWindowsGUI reports whether the current process is the Windows GUI. +func IsWindowsGUI() bool { + if runtime.GOOS != "windows" { + return false + } + exe, _ := os.Executable() + exe = filepath.Base(exe) + return strings.EqualFold(exe, "tailscale-ipn.exe") || strings.EqualFold(exe, "tailscale-ipn") +}