feat: add GPG forwarding to coder ssh (#5482)

cli/ssh_windows.go

@@ -4,9 +4,16 @@
 package cli
 
 import (
+	"bufio"
 	"context"
+	"io"
+	"net"
 	"os"
+	"strconv"
 	"time"
+
+	gossh "golang.org/x/crypto/ssh"
+	"golang.org/x/xerrors"
 )
 
 func listenWindowSize(ctx context.Context) <-chan os.Signal {
@@ -25,3 +32,74 @@ func listenWindowSize(ctx context.Context) <-chan os.Signal {
 	}()
 	return windowSize
 }
+
+func forwardGPGAgent(ctx context.Context, stderr io.Writer, sshClient *gossh.Client) (io.Closer, error) {
+	// Read TCP port and cookie from extra socket file. A gpg-agent socket
+	// file looks like the following:
+	//
+	//     49955
+	//     abcdefghijklmnop
+	//
+	// The first line is the TCP port that gpg-agent is listening on, and
+	// the second line is a 16 byte cookie that MUST be sent as the first
+	// bytes of any connection to this port (otherwise the connection is
+	// closed by gpg-agent).
+	localSocket, err := localGPGExtraSocket(ctx)
+	if err != nil {
+		return nil, err
+	}
+	f, err := os.Open(localSocket)
+	if err != nil {
+		return nil, xerrors.Errorf("open gpg-agent-extra socket file %q: %w", localSocket, err)
+	}
+
+	// Scan lines from file to get port and cookie.
+	var (
+		port    uint16
+		cookie  []byte
+		scanner = bufio.NewScanner(f)
+	)
+	for i := 0; scanner.Scan(); i++ {
+		switch i {
+		case 0:
+			port64, err := strconv.ParseUint(scanner.Text(), 10, 16)
+			if err != nil {
+				return nil, xerrors.Errorf("parse gpg-agent-extra socket file %q: line 1: convert string to integer: %w", localSocket, err)
+			}
+			port = uint16(port64)
+
+		case 1:
+			cookie = scanner.Bytes()
+			if len(cookie) != 16 {
+				return nil, xerrors.Errorf("parse gpg-agent-extra socket file %q: line 2: expected 16 bytes, got %v bytes", localSocket, len(cookie))
+			}
+
+		default:
+			return nil, xerrors.Errorf("parse gpg-agent-extra socket file %q: file contains more than 2 lines", localSocket)
+		}
+	}
+
+	err = scanner.Err()
+	if err != nil {
+		return nil, xerrors.Errorf("parse gpg-agent-extra socket file: %q: %w", localSocket, err)
+	}
+
+	remoteSocket, err := remoteGPGAgentSocket(sshClient)
+	if err != nil {
+		return nil, err
+	}
+
+	localAddr := cookieAddr{
+		Addr: &net.TCPAddr{
+			IP:   net.IPv4(127, 0, 0, 1),
+			Port: int(port),
+		},
+		cookie: cookie,
+	}
+	remoteAddr := &net.UnixAddr{
+		Name: remoteSocket,
+		Net:  "unix",
+	}
+
+	return sshForwardRemote(ctx, stderr, sshClient, localAddr, remoteAddr)
+}