ssh: explicitly set ~ for home directory unless using cmd.exe

coder · spikecurtis · Mar 17, 2025 · Feb 19, 2025 · Feb 24, 2025 · Mar 7, 2025
commit c8b9b65c1f5d04bc28def22ff0fc8c86a47abba2
diff --git a/pkg/agent/dial.go b/pkg/agent/dial.go
@@ -50,20 +50,30 @@ func connect(logger *logging.Logger, transport Transport, mode, prompter string,
 	// environment or cmd.exe), we can leave the "exe" suffix off the target
 	// name. Fortunately this allows us to also avoid having to try the
 	// combination of forward slashes + ".exe" for Windows POSIX environments.
+	//
+	// HACK: When invoking on cmd.exe, we leave off the ~ prefix, since cmd.exe
+	// doesn't recognize it. In most cases the initial working directory for SSH
+	// commands is the home directory, but when possible we try to be explicit,
+	// to work around systems that use a different directory, such as Coder
+	// workspaces, which allow different initial working directories to be
+	// configured.
 	pathSeparator := "/"
+	pathComponents := []string{filesystem.HomeDirectorySpecial}
 	if cmdExe {
 		pathSeparator = "\\"
+		pathComponents = nil
 	}
 	dataDirectoryName := filesystem.MutagenDataDirectoryName
 	if mutagen.DevelopmentModeEnabled {
 		dataDirectoryName = filesystem.MutagenDataDirectoryDevelopmentName
 	}
-	agentInvocationPath := strings.Join([]string{
+	pathComponents = append(pathComponents,
 		dataDirectoryName,
 		filesystem.MutagenAgentsDirectoryName,
 		mutagen.Version,
 		BaseName,
-	}, pathSeparator)
+	)
+	agentInvocationPath := strings.Join(pathComponents, pathSeparator)
 
 	// Compute the command to invoke.
 	command := fmt.Sprintf("%s %s --%s=%s", agentInvocationPath, mode, FlagLogLevel, logger.Level())
@@ -204,7 +214,7 @@ func Dial(logger *logging.Logger, transport Transport, mode, prompter string) (i
 	}
 
 	// Attempt to install.
-	if err := install(logger, transport, prompter); err != nil {
+	if err := install(logger, transport, prompter, cmdExe); err != nil {
 		return nil, fmt.Errorf("unable to install agent: %w", err)
 	}
 

diff --git a/pkg/agent/install.go b/pkg/agent/install.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"runtime"
+	"strings"
 
 	"github.com/google/uuid"
 
@@ -38,7 +39,7 @@ func Install() error {
 
 // install attempts to probe an endpoint and install the appropriate agent
 // binary over the specified transport.
-func install(logger *logging.Logger, transport Transport, prompter string) error {
+func install(logger *logging.Logger, transport Transport, prompter string, cmdExe bool) error {
 	// Detect the target platform.
 	goos, goarch, posix, err := probe(transport, prompter)
 	if err != nil {
@@ -68,14 +69,25 @@ func install(logger *logging.Logger, transport Transport, prompter string) error
 	if err != nil {
 		return fmt.Errorf("unable to generate UUID for agent copying: %w", err)
 	}
-	destination := BaseName + randomUUID.String()
+	remoteFileName := BaseName + randomUUID.String()
 	if goos == "windows" {
-		destination += ".exe"
+		remoteFileName += ".exe"
 	}
 	if posix {
-		destination = "." + destination
+		remoteFileName = "." + remoteFileName
 	}
-	if err = transport.Copy(agentExecutable, destination); err != nil {
+	// HACK: On cmd.exe systems, the ~ special character is not understood to mean the home directory, so we leave it
+	// off, and hope that the default copy directory is the home directory.
+	pathSeparator := "/"
+	pathComponents := []string{filesystem.HomeDirectorySpecial}
+	if cmdExe {
+		pathSeparator = "\\"
+		pathComponents = nil
+	}
+	pathComponents = append(pathComponents, remoteFileName)
+	fullRemotePath := strings.Join(pathComponents, pathSeparator)
+
+	if err = transport.Copy(agentExecutable, fullRemotePath); err != nil {
 		return fmt.Errorf("unable to copy agent binary: %w", err)
 	}
 
@@ -89,7 +101,7 @@ func install(logger *logging.Logger, transport Transport, prompter string) error
 		if err := prompting.Message(prompter, "Setting agent executability..."); err != nil {
 			return fmt.Errorf("unable to message prompter: %w", err)
 		}
-		executabilityCommand := fmt.Sprintf("chmod +x %s", destination)
+		executabilityCommand := fmt.Sprintf("chmod +x %s", fullRemotePath)
 		if err := run(transport, executabilityCommand); err != nil {
 			return fmt.Errorf("unable to set agent executability: %w", err)
 		}
@@ -100,10 +112,11 @@ func install(logger *logging.Logger, transport Transport, prompter string) error
 		return fmt.Errorf("unable to message prompter: %w", err)
 	}
 	var installCommand string
-	if posix {
-		installCommand = fmt.Sprintf("./%s %s", destination, CommandInstall)
+	if posix && cmdExe {
+		// TODO: is this path even possible?
+		installCommand = fmt.Sprintf("./%s %s", fullRemotePath, CommandInstall)
 	} else {
-		installCommand = fmt.Sprintf("%s %s", destination, CommandInstall)
+		installCommand = fmt.Sprintf("%s %s", fullRemotePath, CommandInstall)
 	}
 	if err := run(transport, installCommand); err != nil {
 		return fmt.Errorf("unable to invoke agent installation: %w", err)

diff --git a/pkg/agent/transport/ssh/transport.go b/pkg/agent/transport/ssh/transport.go
@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strconv"
+	"strings"
 
 	"github.com/mutagen-io/mutagen/pkg/agent"
 	"github.com/mutagen-io/mutagen/pkg/agent/transport"
@@ -192,6 +193,12 @@ func (t *sshTransport) Command(command string) (*exec.Cmd, error) {
 
 // ClassifyError implements the ClassifyError method of agent.Transport.
 func (t *sshTransport) ClassifyError(processState *os.ProcessState, errorOutput string) (bool, bool, error) {
+	// Windows Powershell introduces line breaks in the errorOutput, which get
+	// escaped before arriving at this function into a literal `\r` followed by
+	// a newline. Strip these out so that line breaks don't screw with our
+	// matching.
+	errorOutput = strings.ReplaceAll(errorOutput, "\\r\n", "")
+
 	// SSH faithfully returns exit codes and error output, so we can use direct
 	// methods for testing and classification. Note that we may get POSIX-like
 	// error codes back even from Windows remotes, but that indicates a POSIX
@@ -228,6 +235,10 @@ func (t *sshTransport) ClassifyError(processState *os.ProcessState, errorOutput
 		return false, true, nil
 	} else if process.OutputIsWindowsCommandNotFound(errorOutput) {
 		return true, true, nil
+	} else if process.OutputIsWindowsPowershellCommandNotFound(errorOutput) {
+		// It's Windows Powershell, not cmd.exe, so try (re)installing, but set cmdExe
+		// to false.
+		return true, false, nil
 	}
 
 	// Just bail if we weren't able to determine the nature of the error.

diff --git a/pkg/filesystem/mutagen.go b/pkg/filesystem/mutagen.go
@@ -66,6 +66,8 @@ const (
 	// MutagenLicensingDirectoryName is the name of the licensing data directory
 	// within the Mutagen data directory.
 	MutagenLicensingDirectoryName = "licensing"
+
+	HomeDirectorySpecial = "~"
 )
 
 // Mutagen computes (and optionally creates) subdirectories inside the Mutagen

diff --git a/pkg/process/errors.go b/pkg/process/errors.go
@@ -20,6 +20,10 @@ const (
 	// windowsCommandNotFoundFragment is a fragment of the error output returned
 	// on Windows systems when a command cannot be found.
 	windowsCommandNotFoundFragment = "The system cannot find the path specified"
+	// windowsPowershellCommandNotFoundFragment is a fragment of the error output
+	// returned on Windows systems running Powershell when a command cannot be
+	// found.
+	windowsPowershellCommandNotFoundFragment = "is not recognized as the name of a cmdlet, function, script file, or operable program."
 )
 
 // OutputIsPOSIXCommandNotFound returns whether or not a process' error output
@@ -38,6 +42,13 @@ func OutputIsWindowsInvalidCommand(output string) bool {
 // represents a command not found error on Windows.
 func OutputIsWindowsCommandNotFound(output string) bool {
 	return strings.Contains(output, windowsCommandNotFoundFragment)
+
+}
+
+// OutputIsWindowsPowershellCommandNotFound returns whether or not a process' error
+// output represents a command not found error from Windows running Powershell.
+func OutputIsWindowsPowershellCommandNotFound(output string) bool {
+	return strings.Contains(output, windowsPowershellCommandNotFoundFragment)
 }
 
 // ExtractExitErrorMessage is a utility function that will attempt to extract

diff --git a/pkg/synchronization/controller.go b/pkg/synchronization/controller.go
@@ -166,7 +166,7 @@ func newSession(
 		)
 		if err != nil {
 			logger.Info("Beta connection failure:", err)
-			return nil, fmt.Errorf("unable to connect to beta: %w", err)
+			return nil, fmt.Errorf("unable to connect to beta_: %w", err)
 		}
 	}