add reading password from file

Signed-off-by: Florian Brandes <florian.brandes@posteo.de>

config.example

@@ -6,7 +6,8 @@
 hostname = smtp.mail.example.com
 port = 465
 username = foo@example.com
-password = s3cr3t
+# If password_file is supplied, a valid path must be supplied
+# password_file = Path/to/file
 sender = foo@example.com
 # set_reply_to = false
 # use_tls = true

smtprd_ng/smtprd.py

@@ -107,6 +107,22 @@ class Config:
             email_certs[email] = cert
         return email_certs
 
+    @classmethod
+    def _read_from_file(cls, file: Union[Path, str]) -> str:
+        """Read string from file"""
+        if len(file) == 0:
+            # empty string (which is our fallback), so return empty string
+            return ""
+        # file is non-empty and should provide a path
+        file = Path(file)
+        if not file.exists():
+            raise OSError("File wasn't found: " + str(file))
+        with open(file, "r", encoding="utf8") as fp:
+            line = fp.readline().strip("\n")
+        if len(line) == 0:
+            raise OSError("Empty file supplied: " + str(file))
+        return line
+
     @classmethod
     def _from_config(cls, config: configparser.RawConfigParser) -> "Config":
         email_certs = cls._get_emails_and_certs(config.items("emails"))
@@ -120,7 +136,9 @@ class Config:
                 port=config.getint("client", "port"),
                 sender=config.get("client", "sender"),
                 username=config.get("client", "username"),
-                password=config.get("client", "password"),
+                password=cls._read_from_file(
+                    (config.get("client", "password_file", fallback=""))
+                ),
                 set_reply_to=config.getboolean(
                     "client", "set_reply_to", fallback=False
                 ),

tests/test_smtprd_ng.py

@@ -19,7 +19,6 @@
 Tests for smtprd_ng
 """
 # pylint: disable=protected-access
-# pylint: disable=unused-argument
 
 import configparser
 import email
@@ -68,6 +67,7 @@ def test_config_from_config():
     assert cfg.client.port == 465
     assert cfg.client.smime_cert == ""
     assert cfg.client.use_tls is True
+    assert cfg.client.password == ""
 
 
 def test_config_from_ini():
@@ -80,6 +80,24 @@ def test_config_from_ini():
     assert cfg.client.use_tls is True
 
 
+def test_read_from_file():
+    """Test read_from_file function and the fallback"""
+    existing_file = "config.example"
+    non_existing_file = "abcde"
+    empty_file = "tests/__init__.py"
+    empty_string = ""
+    assert smtprd.Config._read_from_file(existing_file) == "# [server]"
+    with pytest.raises(Exception) as e_info:
+        smtprd.Config._read_from_file(non_existing_file)
+    assert e_info.typename == "OSError"
+    assert str(e_info.value) == "File wasn't found: abcde"
+    assert smtprd.Config._read_from_file(empty_string) == ""
+    with pytest.raises(Exception) as e_info:
+        smtprd.Config._read_from_file(empty_file)
+    assert e_info.typename == "OSError"
+    assert str(e_info.value) == "Empty file supplied: tests/__init__.py"
+
+
 def test_config_emailcerts():
     """test retrieval of email/cert pair"""
     email_list = [("email1", "cert1"), ("email2", "cert2")]
@@ -153,7 +171,7 @@ def test_client_sign():
     assert "Test to sign" in v.decode()
 
 
-def test_cli_no_config_file(capsys):
+def test_cli_no_config_file():
     """Test whether config file parameter is supplied"""
     test_args = ["--config", ""]
     with pytest.raises(Exception) as e_info:
@@ -162,7 +180,7 @@ def test_cli_no_config_file(capsys):
     assert str(e_info.value) == "No config file supplied"
 
 
-def test_cli_config_file_not_found(capsys):
+def test_cli_config_file_not_found():
     """Test whether config file is found"""
     test_args = ["--config", "doesnotexist.conf"]
     with pytest.raises(Exception) as e_info: