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@@ -0,0 +1,142 @@
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+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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+// Use of this source code is governed by a BSD-style
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+// license that can be found in the LICENSE file.
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+
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+package tshttpproxy
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+
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+import (
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+ "log"
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+ "net/http"
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+ "net/url"
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+ "strings"
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+ "syscall"
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+ "unsafe"
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+
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+ "golang.org/x/sys/windows"
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+)
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+
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+var (
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+ winHTTP = windows.NewLazySystemDLL("winhttp.dll")
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+ httpOpenProc = winHTTP.NewProc("WinHttpOpen")
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+ closeHandleProc = winHTTP.NewProc("WinHttpCloseHandle")
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+ getProxyForUrlProc = winHTTP.NewProc("WinHttpGetProxyForUrl")
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+)
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+
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+func init() {
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+ sysProxyFromEnv = proxyFromWinHTTP
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+}
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+
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+func proxyFromWinHTTP(req *http.Request) (*url.URL, error) {
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+ if req.URL == nil {
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+ return nil, nil
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+ }
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+ urlStr := req.URL.String()
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+
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+ whi, err := winHTTPOpen()
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+ if err != nil {
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+ // Log but otherwise ignore the error.
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+ log.Printf("winhttp: Open: %v", err)
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+ return nil, nil
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+ }
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+ defer whi.Close()
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+
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+ v, err := whi.GetProxyForURL(urlStr)
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+ if err != nil {
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+ // See https://docs.microsoft.com/en-us/windows/win32/winhttp/error-messages
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+ const ERROR_WINHTTP_AUTODETECTION_FAILED = 12180
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+ if err == syscall.Errno(ERROR_WINHTTP_AUTODETECTION_FAILED) {
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+ return nil, nil
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+ }
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+ log.Printf("winhttp: GetProxyForURL(%q): %v (%T, %#v)", urlStr, err, err, err)
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+ return nil, nil
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+ }
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+ if v != "" {
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+ if !strings.HasPrefix(v, "https://") {
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+ v = "http://" + v
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+ }
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+ if u, err := url.Parse(v); err == nil {
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+ return u, nil
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+ }
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+ }
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+
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+ return nil, nil
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+}
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+
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+var userAgent = windows.StringToUTF16Ptr("Tailscale")
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+
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+const (
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+ winHTTP_ACCESS_TYPE_AUTOMATIC_PROXY = 4
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+ winHTTP_AUTOPROXY_ALLOW_AUTOCONFIG = 0x00000100
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+ winHTTP_AUTOPROXY_AUTO_DETECT = 1
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+ winHTTP_AUTO_DETECT_TYPE_DHCP = 0x00000001
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+ winHTTP_AUTO_DETECT_TYPE_DNS_A = 0x00000002
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+)
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+
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+func winHTTPOpen() (winHTTPInternet, error) {
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+ if err := httpOpenProc.Find(); err != nil {
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+ return 0, err
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+ }
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+ r, _, err := httpOpenProc.Call(
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+ uintptr(unsafe.Pointer(userAgent)),
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+ winHTTP_ACCESS_TYPE_AUTOMATIC_PROXY,
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+ 0, /* WINHTTP_NO_PROXY_NAME */
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+ 0, /* WINHTTP_NO_PROXY_BYPASS */
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+ 0)
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+ if r == 0 {
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+ return 0, err
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+ }
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+ return winHTTPInternet(r), nil
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+}
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+
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+type winHTTPInternet windows.Handle
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+
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+func (hi winHTTPInternet) Close() error {
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+ if err := closeHandleProc.Find(); err != nil {
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+ return err
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+ }
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+ r, _, err := closeHandleProc.Call(uintptr(hi))
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+ if r == 1 {
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+ return nil
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+ }
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+ return err
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+}
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+
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+// WINHTTP_AUTOPROXY_OPTIONS
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+// https://docs.microsoft.com/en-us/windows/win32/api/winhttp/ns-winhttp-winhttp_autoproxy_options
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+type autoProxyOptions struct {
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+ DwFlags uint32
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+ DwAutoDetectFlags uint32
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+ AutoConfigUrl *uint16
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+ _ uintptr
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+ _ uint32
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+ FAutoLogonIfChallenged bool
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+}
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+
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+// WINHTTP_PROXY_INFO
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+// https://docs.microsoft.com/en-us/windows/win32/api/winhttp/ns-winhttp-winhttp_proxy_info
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+type winHTTPProxyInfo struct {
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+ AccessType uint16
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+ Proxy *uint16
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+ ProxyBypass *uint16
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+}
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+
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+var proxyForURLOpts = &autoProxyOptions{
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+ DwFlags: winHTTP_AUTOPROXY_ALLOW_AUTOCONFIG | winHTTP_AUTOPROXY_AUTO_DETECT,
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+ DwAutoDetectFlags: winHTTP_AUTO_DETECT_TYPE_DHCP, // | winHTTP_AUTO_DETECT_TYPE_DNS_A,
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+}
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+
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+func (hi winHTTPInternet) GetProxyForURL(urlStr string) (string, error) {
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+ if err := getProxyForUrlProc.Find(); err != nil {
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+ return "", err
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+ }
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+ var out winHTTPProxyInfo
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+ r, _, err := getProxyForUrlProc.Call(
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+ uintptr(hi),
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+ uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(urlStr))),
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+ uintptr(unsafe.Pointer(proxyForURLOpts)),
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+ uintptr(unsafe.Pointer(&out)))
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+ if r == 1 {
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+ return windows.UTF16PtrToString(out.Proxy), nil
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+ }
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+ return "", err
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+}
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Brad Fitzpatrick