tailscale/net/tshttpproxy/tshttpproxy.go

106 lines
2.8 KiB
Go

// Copyright (c) 2020 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 tshttpproxy contains Tailscale additions to httpproxy not available
// in golang.org/x/net/http/httpproxy. Notably, it aims to support Windows better.
package tshttpproxy
import (
"net/http"
"net/url"
"os"
"sync"
"time"
)
// InvalidateCache invalidates the package-level cache for ProxyFromEnvironment.
//
// It's intended to be called on network link/routing table changes.
func InvalidateCache() {
mu.Lock()
defer mu.Unlock()
noProxyUntil = time.Time{}
}
var (
mu sync.Mutex
noProxyUntil time.Time // if non-zero, time at which ProxyFromEnvironment should check again
)
// setNoProxyUntil stops calls to sysProxyEnv (if any) for the provided duration.
func setNoProxyUntil(d time.Duration) {
mu.Lock()
defer mu.Unlock()
noProxyUntil = time.Now().Add(d)
}
var _ = setNoProxyUntil // quiet staticcheck; Windows uses the above, more might later
// sysProxyFromEnv, if non-nil, specifies a platform-specific ProxyFromEnvironment
// func to use if http.ProxyFromEnvironment doesn't return a proxy.
// For example, WPAD PAC files on Windows.
var sysProxyFromEnv func(*http.Request) (*url.URL, error)
// ProxyFromEnvironment is like the standard library's http.ProxyFromEnvironment
// but additionally does OS-specific proxy lookups if the environment variables
// alone don't specify a proxy.
func ProxyFromEnvironment(req *http.Request) (*url.URL, error) {
u, err := http.ProxyFromEnvironment(req)
if u != nil && err == nil {
return u, nil
}
mu.Lock()
noProxyTime := noProxyUntil
mu.Unlock()
if time.Now().Before(noProxyTime) {
return nil, nil
}
if sysProxyFromEnv != nil {
u, err := sysProxyFromEnv(req)
if u != nil && err == nil {
return u, nil
}
}
return nil, err
}
var sysAuthHeader func(*url.URL) (string, error)
// GetAuthHeader returns the Authorization header value to send to proxy u.
func GetAuthHeader(u *url.URL) (string, error) {
if fake := os.Getenv("TS_DEBUG_FAKE_PROXY_AUTH"); fake != "" {
return fake, nil
}
if user := u.User.Username(); user != "" {
pass, ok := u.User.Password()
if !ok {
return "", nil
}
req := &http.Request{Header: make(http.Header)}
req.SetBasicAuth(user, pass)
return req.Header.Get("Authorization"), nil
}
if sysAuthHeader != nil {
return sysAuthHeader(u)
}
return "", nil
}
var condSetTransportGetProxyConnectHeader func(*http.Transport)
// SetTransportGetProxyConnectHeader sets the provided Transport's
// GetProxyConnectHeader field, if the current build of Go supports
// it.
//
// See https://github.com/golang/go/issues/41048.
func SetTransportGetProxyConnectHeader(tr *http.Transport) {
if f := condSetTransportGetProxyConnectHeader; f != nil {
f(tr)
}
}