Improve error message if data dir and config unavailable due to permissions

lib/config/fileconf.go

@@ -20,8 +20,10 @@ import (
 	"bytes"
 	"crypto/tls"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net"
 	"net/url"
@@ -91,7 +93,10 @@ type FileConfig struct {
 func ReadFromFile(filePath string) (*FileConfig, error) {
 	f, err := os.Open(filePath)
 	if err != nil {
-		return nil, trace.Wrap(err, fmt.Sprintf("failed to open file: %v", filePath))
+		if errors.Is(err, fs.ErrPermission) {
+			return nil, trace.Wrap(err, "failed to open file for Teleport configuration: %v. Ensure that you are running as a user with appropriate permissions.", filePath)
+		}
+		return nil, trace.Wrap(err, "failed to open file for Teleport configuration at %v", filePath)
 	}
 	defer f.Close()
 	return ReadConfig(f)

lib/service/service.go

@@ -24,8 +24,10 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net"
 	"net/http"
@@ -623,6 +625,9 @@ func NewTeleport(cfg *Config) (*TeleportProcess, error) {
 	if os.IsNotExist(err) {
 		err := os.MkdirAll(cfg.DataDir, os.ModeDir|0700)
 		if err != nil {
+			if errors.Is(err, fs.ErrPermission) {
+				cfg.Log.Errorf("Teleport does not have permission to write to: %v. Ensure that you are running as a user with appropriate permissions.", cfg.DataDir)
+			}
 			return nil, trace.ConvertSystemError(err)
 		}
 	}
@@ -659,6 +664,9 @@ func NewTeleport(cfg *Config) (*TeleportProcess, error) {
 			cfg.Log.Infof("Generating new host UUID: %v.", cfg.HostUUID)
 		}
 		if err := utils.WriteHostUUID(cfg.DataDir, cfg.HostUUID); err != nil {
+			if errors.Is(err, fs.ErrPermission) {
+				cfg.Log.Errorf("Teleport does not have permission to write to: %v. Ensure that you are running as a user with appropriate permissions.", cfg.DataDir)
+			}
 			return nil, trace.Wrap(err)
 		}
 	}

lib/utils/utils.go

@@ -18,8 +18,10 @@ package utils
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net"
 	"net/url"
@@ -437,8 +439,12 @@ func ReadHostUUID(dataDir string) (string, error) {
 
 // WriteHostUUID writes host UUID into a file
 func WriteHostUUID(dataDir string, id string) error {
-	err := ioutil.WriteFile(filepath.Join(dataDir, HostUUIDFile), []byte(id), os.ModeExclusive|0400)
+	err := os.WriteFile(filepath.Join(dataDir, HostUUIDFile), []byte(id), os.ModeExclusive|0400)
 	if err != nil {
+		if errors.Is(err, fs.ErrPermission) {
+			//do not convert to system error as this loses the ability to compare that it is a permission error
+			return err
+		}
 		return trace.ConvertSystemError(err)
 	}
 	return nil