Windows ssh-agent workaround

lib/sshcryptagent/agent.go

@@ -2,17 +2,48 @@ package sshcryptagent
 
 import (
 	"fmt"
+	"io"
 	"net"
 	"os"
+	"strings"
 
 	"golang.org/x/crypto/ssh"
 	"golang.org/x/crypto/ssh/agent"
 )
 
+type ReadWriter struct {
+	io.Reader
+	io.Writer
+}
+
+func NewReadWriter(r io.Reader, w io.Writer) io.ReadWriter {
+	return &ReadWriter{r, w}
+}
+
 func GetSigners() ([]ssh.Signer, error) {
-	conn, err := net.Dial("unix", os.Getenv("SSH_AUTH_SOCK"))
-	if err != nil {
-		return nil, fmt.Errorf("Could not connect to the SSH Agent socket. %s", err)
+	sockAddr := os.Getenv("SSH_AUTH_SOCK")
+
+	// ex: "socat.exe - UNIX-CONNECT:%a"
+	socatFormat := os.Getenv("SSH_AUTH_SOCAT")
+	var conn io.ReadWriter
+	var err error
+	if len(socatFormat) > 0 {
+		socatCommand := fmtCommand(socatFormat, sockAddr)
+		cmd := MkCommand(socatCommand)
+		cmd.Stderr = os.Stderr
+		pipeRd, err := cmd.StdoutPipe()
+		pipeWr, err := cmd.StdinPipe()
+
+		err = cmd.Start()
+		if err != nil {
+			return nil, fmt.Errorf("Could not start \"%s\": %s", socatCommand, err)
+		}
+		conn = NewReadWriter(pipeRd, pipeWr)
+	} else {
+		conn, err = net.Dial("unix", sockAddr)
+		if err != nil {
+			return nil, fmt.Errorf("Could not connect to the SSH Agent socket. %s", err)
+		}
 	}
 
 	sshAgent := agent.NewClient(conn)
@@ -27,3 +58,31 @@ func GetSigners() ([]ssh.Signer, error) {
 
 	return signers, nil
 }
+
+func fmtCommand(format string, address string) string {
+	var out strings.Builder
+	inPercent := false
+	for _, c := range format {
+		if inPercent {
+			inPercent = false
+			if (c == '%') {
+				out.WriteRune('%');
+			} else if (c == 'a') {
+				out.WriteString(address);
+			} else {
+				out.WriteRune('%')
+				out.WriteRune(c);
+			}
+		} else {
+			if c == '%' {
+				inPercent = true
+			} else {
+				out.WriteRune(c);
+			}
+		}
+	}
+	if inPercent {
+		out.WriteRune('%')
+	}
+	return out.String()
+}

lib/sshcryptagent/cmdline_generic.go

@@ -0,0 +1,15 @@
+// +build !windows,!plan9
+
+package sshcryptagent
+
+
+import (
+	"os/exec"
+)
+
+
+//
+
+func MkCommand(cmdline string) *exec.Cmd {
+	return exec.Command("sh", "-c", cmdline);
+}

lib/sshcryptagent/cmdline_windows.go

@@ -0,0 +1,15 @@
+// +build windows
+
+package sshcryptagent
+
+
+import (
+	"os/exec"
+)
+
+
+//
+
+func MkCommand(cmdline string) *exec.Cmd {
+	return exec.Command("cmd.exe", "/c", cmdline);
+}