sftpd auto host keys: try to auto-create parent dir if missing

sftpd/server.go

@@ -482,6 +482,8 @@ func (c *Configuration) checkHostKeyAutoGeneration(configDir string) error {
 					logger.InfoToConsole("try to create non-existent host key %#v", k)
 					err = utils.GenerateRSAKeys(k)
 					if err != nil {
+						logger.Warn(logSender, "", "error creating host key %#v: %v", k, err)
+						logger.WarnToConsole("error creating host key %#v: %v", k, err)
 						return err
 					}
 				case defaultPrivateECDSAKeyName:
@@ -489,6 +491,8 @@ func (c *Configuration) checkHostKeyAutoGeneration(configDir string) error {
 					logger.InfoToConsole("try to create non-existent host key %#v", k)
 					err = utils.GenerateECDSAKeys(k)
 					if err != nil {
+						logger.Warn(logSender, "", "error creating host key %#v: %v", k, err)
+						logger.WarnToConsole("error creating host key %#v: %v", k, err)
 						return err
 					}
 				default:
@@ -511,6 +515,8 @@ func (c *Configuration) checkHostKeyAutoGeneration(configDir string) error {
 					err = utils.GenerateECDSAKeys(autoFile)
 				}
 				if err != nil {
+					logger.Warn(logSender, "", "error creating host key %#v: %v", autoFile, err)
+					logger.WarnToConsole("error creating host key %#v: %v", autoFile, err)
 					return err
 				}
 			}

utils/utils.go

@@ -188,6 +188,9 @@ func DecryptData(data string) (string, error) {
 // private key to specified file and the public key to the specified
 // file adding the .pub suffix
 func GenerateRSAKeys(file string) error {
+	if err := createDirPathIfMissing(file, 0700); err != nil {
+		return err
+	}
 	key, err := rsa.GenerateKey(rand.Reader, 4096)
 	if err != nil {
 		return err
@@ -219,6 +222,9 @@ func GenerateRSAKeys(file string) error {
 // private key to specified file and the public key to the specified
 // file adding the .pub suffix
 func GenerateECDSAKeys(file string) error {
+	if err := createDirPathIfMissing(file, 0700); err != nil {
+		return err
+	}
 	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
 	if err != nil {
 		return err
@@ -312,3 +318,14 @@ func CleanDirInput(dirInput string) string {
 	}
 	return filepath.Clean(dirInput)
 }
+
+func createDirPathIfMissing(file string, perm os.FileMode) error {
+	dirPath := filepath.Dir(file)
+	if _, err := os.Stat(dirPath); os.IsNotExist(err) {
+		err = os.MkdirAll(dirPath, perm)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}