Add support for libassuan file sockets (WinGnuPG support) (jstarks#6)

This commit squishes the changeset presented on jstarks#6. That commit is then rebased
onto albertony/npiperelay:fork

npiperelay.go

@@ -2,13 +2,15 @@
 package main
 
 import (
+	"bufio"
 	"errors"
 	"flag"
 	"fmt"
 	"io"
 	"log"
 	"os"
 	"runtime"
+	"strconv"
 	"sync"
 	"time"
 
@@ -20,6 +22,7 @@ const (
 	cSECURITY_SQOS_PRESENT = 0x100000               //nolint:revive,stylecheck // Don't include revive and stylecheck when running golangci-lint to stop complain about use of underscores in Go names
 	cSECURITY_ANONYMOUS    = 0                      //nolint:revive,stylecheck // Don't include revive and stylecheck when running golangci-lint to stop complain about use of underscores in Go names
 	cPOLL_TIMEOUT          = 200 * time.Millisecond //nolint:revive,stylecheck // Don't include revive and stylecheck when running golangci-lint to stop complain about use of underscores in Go names
+        pollTimeout = 200 * time.Millisecond
 )
 
 var (
@@ -28,6 +31,7 @@ var (
 	closeOnEOF      = flag.Bool("ep", false, "terminate on EOF reading from the pipe, even if there is more data to write")
 	closeOnStdinEOF = flag.Bool("ei", false, "terminate on EOF reading from stdin, even if there is more data to write")
 	runInBackground = flag.Bool("bg", false, "hide console window and run in background")
+	assuan          = flag.Bool("a", false, "treat the target as a libassuan file socket (Used by GnuPG)")
 	verbose         = flag.Bool("v", false, "verbose output on stderr")
 
 	version = "0.0.0-dev" // Replaced with value from ldflag in build by GoReleaser: Current Git tag with the v prefix stripped
@@ -80,6 +84,107 @@ func dialPipe(p string, poll bool) (*overlappedFile, error) {
 	}
 }
 
+func dialPort(p int, poll bool) (*overlappedFile, error) {
+	if p < 0 || p > 65535 {
+		return nil, errors.New("Invalid port value")
+	}
+
+	h, err := windows.Socket(windows.AF_INET, windows.SOCK_STREAM, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create a SockaddrInet4 for connecting to
+	sa := &windows.SockaddrInet4{Addr: [4]byte{0x7F, 0x00, 0x00, 0x01}, Port: p}
+
+	// Bind to a randomly assigned local port
+	err = windows.Bind(h, &windows.SockaddrInet4{})
+	if err != nil {
+		return nil, err
+	}
+
+	// Wrap our socket up to be properly handled
+	conn := newOverlappedFile(h)
+
+	// Connect to the LibAssuan socket using overlapped ConnectEx operation
+	_, err = conn.asyncIo(func(h windows.Handle, n *uint32, o *windows.Overlapped) error {
+		return windows.ConnectEx(h, sa, nil, 0, nil, o)
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return conn, nil
+}
+
+// LibAssaun file socket: Attempt to read contents of the target file and connect to a TCP port
+func dialAssuan(p string, poll bool) (*overlappedFile, error) {
+	pipeConn, err := dialPipe(p, poll)
+	if err != nil {
+		return nil, err
+	}
+
+	var port int
+	var nonce [16]byte
+
+	reader := bufio.NewReader(pipeConn)
+
+	// Read the target port number from the first line
+	tmp, _, err := reader.ReadLine()
+	if err == nil {
+		port, err = strconv.Atoi(string(tmp))
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	// Read the rest of the nonce from the file
+	n, err := reader.Read(nonce[:])
+	if err != nil {
+		return nil, err
+	}
+
+	if n != 16 {
+		err = fmt.Errorf("Read incorrect number of bytes for nonce. Expected 16, got %d (0x%X)", n, nonce)
+		return nil, err
+	}
+
+	if *verbose {
+		log.Printf("Port: %d, Nonce: %X", port, nonce)
+	}
+
+	pipeConn.Close()
+
+	for {
+		// Try to connect to the libassaun TCP socket hosted on localhost
+		conn, err := dialPort(port, poll)
+
+		if poll && (err == windows.WSAETIMEDOUT || err == windows.WSAECONNREFUSED || err == windows.WSAENETUNREACH || err == windows.ERROR_CONNECTION_REFUSED) {
+			time.Sleep(pollTimeout)
+			continue
+		}
+
+		if err != nil {
+			err = os.NewSyscallError("ConnectEx", err)
+			return nil, err
+		}
+
+		_, err = conn.Write(nonce[:])
+		if err != nil {
+			return nil, err
+		}
+
+		return conn, nil
+	}
+}
+
+func underlyingError(err error) error {
+	if serr, ok := err.(*os.SyscallError); ok {
+		return serr.Err
+	}
+	return err
+}
+
 func main() {
 	flag.Usage = func() {
 		// Custom usage message (default documented here: https://pkg.go.dev/flag#pkg-variables)
@@ -108,7 +213,14 @@ func main() {
 		log.Println("connecting to", args[0])
 	}
 
-	conn, err := dialPipe(args[0], *poll)
+	var conn *overlappedFile
+	var err error
+
+	if !*assuan {
+		conn, err = dialPipe(args[0], *poll)
+	} else {
+		conn, err = dialAssuan(args[0], *poll)
+	}
 	if err != nil {
 		log.Fatalln(err)
 	}
@@ -145,7 +257,7 @@ func main() {
 	}()
 
 	_, err = io.Copy(os.Stdout, conn)
-	if errors.Is(err, windows.ERROR_BROKEN_PIPE) || errors.Is(err, windows.ERROR_PIPE_NOT_CONNECTED) {
+	if underlyingError(err) == windows.ERROR_BROKEN_PIPE || underlyingError(err) == windows.ERROR_PIPE_NOT_CONNECTED {
 		// The named pipe is closed and there is no more data to read. Since
 		// named pipes are not bidirectional, there is no way for the other side
 		// of the pipe to get more data, so do not wait for the stdin copy to

scripts/gpg-relay

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec socat UNIX-LISTEN:/home/<your-username>/.gnupg/S.gpg-agent,fork, EXEC:'npiperelay.exe -ei -ep -s -a "C:/Users/<your-user-folder>/AppData/Roaming/gnupg/S.gpg-agent"',nofork