[vnet] feat: add SSH configuration diagnostic

api/profile/profile.go

@@ -317,19 +317,26 @@ func FullProfilePath(dir string) string {
 
 // defaultProfilePath retrieves the default path of the TSH profile.
 func defaultProfilePath() string {
-	// start with UserHomeDir, which is the fastest option as it
-	// relies only on environment variables and does not perform
-	// a user lookup (which can be very slow on large AD environments)
-	home, err := os.UserHomeDir()
-	if err == nil && home != "" {
-		return filepath.Join(home, profileDir)
+	home, ok := UserHomeDir()
+	if !ok {
+		home = os.TempDir()
 	}
+	return filepath.Join(home, profileDir)
+}
 
-	home = os.TempDir()
+// UserHomeDir returns the current user's home directory if it can be found.
+func UserHomeDir() (string, bool) {
+	// Start with os.UserHomeDir, which is the fastest option as it relies only
+	// on environment variables and does not perform a user lookup (which can be
+	// very slow on large AD environments).
+	if home, err := os.UserHomeDir(); err == nil && home != "" {
+		return home, true
+	}
+	// Fall back to the user lookup.
 	if u, err := user.Current(); err == nil && u.HomeDir != "" {
-		home = u.HomeDir
+		return u.HomeDir, true
 	}
-	return filepath.Join(home, profileDir)
+	return "", false
 }
 
 // FromDir reads the user profile from a given directory. If dir is empty,

api/utils/keypaths/keypaths.go

@@ -82,9 +82,9 @@ const (
 	// vnetKnownHosts is the file name of the known_hosts file trusted by
 	// third-party SSH clients connecting to VNet SSH.
 	vnetKnownHosts = "vnet_known_hosts"
-	// vnetSSHConfig is the file name of the generated OpenSSH-compatible config
+	// VNetSSHConfig is the file name of the generated OpenSSH-compatible config
 	// file to be used by third-party SSH clients connecting to VNet SSH.
-	vnetSSHConfig = "vnet_ssh_config"
+	VNetSSHConfig = "vnet_ssh_config"
 )
 
 // Here's the file layout of all these keypaths.
@@ -463,7 +463,7 @@ func VNetKnownHostsPath(baseDir string) string {
 // VNetSSHConfigPath returns the path to VNet's generated OpenSSH-compatible
 // config file.
 func VNetSSHConfigPath(baseDir string) string {
-	return filepath.Join(baseDir, vnetSSHConfig)
+	return filepath.Join(baseDir, VNetSSHConfig)
 }
 
 // TrimKeyPathSuffix returns the given path with any key suffix/extension trimmed off.