add a configurable list of recipients/cert dict

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

.vscode/launch.json

@@ -0,0 +1,17 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Python Debugger: Current File test",
+            "type": "debugpy",
+            "request": "launch",
+            "program": "${file}",
+            "console": "integratedTerminal",
+            "cwd": "${workspaceFolder}",
+            "env": {"PYTHONPATH": "${workspaceRoot}:${env:PYTHONPATH}"},
+        }
+    ]
+}

.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "python.testing.pytestArgs": [
+        "tests"
+    ],
+    "python.testing.unittestEnabled": false,
+    "python.testing.pytestEnabled": true
+}

config.example

@@ -8,10 +8,16 @@ port = 465
 username = foo@example.com
 password = s3cr3t
 sender = foo@example.com
-recipients = monitoring.foo@example.com, John Foobar <foo@baz.org>
 # set_reply_to = false
 # use_tls = true
 # start_tls = false
 # smime_cert = /path/to/cert
 # smime_cert_private = /path/to/cert.key
-# smime_to_cert = /path/to/recipient_cert
+# smime_to_cert = /path/to/recipient_cert
+
+[emails]
+# If you want to encrypt outgoing email, add the recipient certificate to the email
+# if not, add an empty string
+# uses email = Path to certificate
+# monitoring.foo@example.com = /path/to/recipient_cert
+# unencrypted@example.com = ""

smtprd_ng/smtprd.py

@@ -70,7 +70,6 @@ class ClientConfig:
     hostname: str
     port: int
     sender: str
-    recipients: List[str]
     username: Optional[str]
     password: Optional[str]
     set_reply_to: bool
@@ -78,7 +77,13 @@ class ClientConfig:
     start_tls: bool
     smime_cert: str
     smime_cert_private: str
-    smime_to_cert: str
+
+
+@dataclass(frozen=True)
+class EmailConfig:
+    """email to cert matching"""
+
+    email_certs: dict
 
 
 @dataclass(frozen=True)
@@ -92,9 +97,19 @@ class Config:
 
     server: ServerConfig
     client: ClientConfig
+    emails: EmailConfig
+
+    @classmethod
+    def _get_emails_and_certs(cls, emailcertlist: list[tuple[str, str]]) -> dict:
+        """Take the List from the INI file and convert to dict"""
+        email_certs = {}
+        for email, cert in emailcertlist:
+            email_certs[email] = cert
+        return email_certs
 
     @classmethod
     def _from_config(cls, config: configparser.RawConfigParser) -> "Config":
+        email_certs = cls._get_emails_and_certs(config.items("emails"))
         return cls(
             server=ServerConfig(
                 hostname=config.get("server", "hostname", fallback="localhost"),
@@ -104,9 +119,6 @@ class Config:
                 hostname=config.get("client", "hostname"),
                 port=config.getint("client", "port"),
                 sender=config.get("client", "sender"),
-                recipients=[
-                    _.strip() for _ in config.get("client", "recipients").split(",")
-                ],
                 username=config.get("client", "username"),
                 password=config.get("client", "password"),
                 set_reply_to=config.getboolean(
@@ -118,8 +130,8 @@ class Config:
                 smime_cert_private=config.get(
                     "client", "smime_cert_private", fallback=""
                 ),
-                smime_to_cert=config.get("client", "smime_to_cert", fallback=""),
             ),
+            emails=EmailConfig(email_certs=email_certs),
         )
 
     @classmethod
@@ -151,8 +163,9 @@ class SMTPClient(SMTP):
 
     """
 
-    def __init__(self, config: ClientConfig) -> None:
+    def __init__(self, config: ClientConfig, emails: EmailConfig) -> None:
         self._config: ClientConfig = config
+        self._emails: EmailConfig = emails
         self._lock: asyncio.Lock = asyncio.Lock()
         super().__init__(
             hostname=self._config.hostname,
@@ -163,11 +176,13 @@ class SMTPClient(SMTP):
             start_tls=self._config.start_tls,
         )
 
-    def _encrypt(self, message: bytes, subject: str) -> bytes:
+    def _encrypt(self, message: bytes, subject: str, recipient: str) -> bytes:
         """Encrypt the message
 
         Args:
             message (bytes): message in bytes format (can/should be signed)
+            subject (str): Subject of the message
+            recipient: Recipient of the message
 
         Returns:
             bytes: Encrypted message
@@ -176,7 +191,7 @@ class SMTPClient(SMTP):
         s = SMIME.SMIME()
 
         # Load target cert to encrypt to.
-        x509 = X509.load_cert(self._config.smime_to_cert)
+        x509 = X509.load_cert(self._emails.email_certs[recipient])
         sk = X509.X509_Stack()
         sk.push(x509)
         s.set_x509_stack(sk)
@@ -191,7 +206,7 @@ class SMTPClient(SMTP):
 
         # Add header
         out.write("From: " + self._config.sender + "\r\n")
-        out.write("To: " + ", ".join(self._config.recipients) + "\r\n")
+        out.write("To: " + recipient + "\r\n")
         out.write("Subject: " + subject + "\r\n")
         s.write(out, p7)
 
@@ -222,7 +237,7 @@ class SMTPClient(SMTP):
         )
         return output
 
-    def _encrypt_and_sign(self, message: Message) -> bytes:
+    def _encrypt_and_sign(self, message: Message, recipient: str) -> bytes:
         """Sign and encrypt the message
 
         Args:
@@ -232,7 +247,7 @@ class SMTPClient(SMTP):
             bytes: The signed and encrypted message including the From and To Header
         """
         signed = self._sign(message)
-        encrypt = self._encrypt(signed, message.get("Subject", ""))
+        encrypt = self._encrypt(signed, message.get("Subject", ""), recipient)
         return encrypt
 
     async def _send_message(
@@ -276,30 +291,28 @@ class SMTPClient(SMTP):
         del message["Reply-To"]
         message["Original-Sender"] = sender if sender is not None else ""
         message["Original-Recipient"] = ", ".join(recipients)
-
-        print(
-            f"{self._config.sender} ({message['Original-Sender']}) -> "
-            f"{', '.join(self._config.recipients)} ({message['Original-Recipient']}): "
-            f"'{message.get('Subject', '')}'"
-        )
-        if self._config.smime_cert:
-            message = self._encrypt_and_sign(message)
-        async with (
-            self._lock
-        ):  # TODO: consumer task from spool queue, reusing connections
-            try:
-                await self.connect()
-                await self._send_message(
-                    message, self._config.sender, self._config.recipients
-                )
-            except SMTPRecipientsRefused as e:
-                raise RuntimeError(
-                    f"Recipients refused: {', '.join(_.recipient for _ in e.recipients)}"
-                ) from e
-            except (SMTPException, OSError) as e:
-                raise RuntimeError(str(e)) from e
-            finally:
-                self.close()
+        for recipient in self._emails.email_certs:
+            print(
+                f"{self._config.sender} ({message['Original-Sender']}) -> "
+                f"{recipient} ({message['Original-Recipient']}): "
+                f"'{message.get('Subject', '')}'"
+            )
+            if self._config.smime_cert and self._emails.email_certs[recipient] != "":
+                message = self._encrypt_and_sign(message, recipient)
+            async with (
+                self._lock
+            ):  # TODO: consumer task from spool queue, reusing connections
+                try:
+                    await self.connect()
+                    await self._send_message(message, self._config.sender, recipient)
+                except SMTPRecipientsRefused as e:
+                    raise RuntimeError(
+                        f"Recipients refused: {', '.join(_.recipient for _ in e.recipients)}"
+                    ) from e
+                except (SMTPException, OSError) as e:
+                    raise RuntimeError(str(e)) from e
+                finally:
+                    self.close()
 
 
 # pylint: disable=too-few-public-methods
@@ -443,7 +456,7 @@ def main(args=None) -> int:
         print(str(e), file=sys.stderr)
         return 1
     controller = SMTPServer(
-        config=config.server, handler=Handler(SMTPClient(config.client))
+        config=config.server, handler=Handler(SMTPClient(config.client, config.emails))
     )
     return 0 if controller.run() else 1
 

tests/test_smtprd_ng.py

@@ -42,15 +42,22 @@ def config() -> smtprd.ClientConfig:
         use_tls=False,
         start_tls=False,
         sender="sender",
-        recipients=["recipient"],
         set_reply_to="",
-        smime_to_cert=Path("tests", "signer.pem"),
         smime_cert=Path("tests", "signer.pem"),
         smime_cert_private=Path("tests", "privkey.pem"),
     )
     return cfg
 
 
+def emails() -> smtprd.EmailConfig:
+    """Return the email dict"""
+
+    cfg = smtprd.EmailConfig(
+        email_certs={"recipient": Path("tests", "signer.pem")},
+    )
+    return cfg
+
+
 def test_config_from_config():
     """Test opening and reading the config file"""
     config_parser: configparser.ConfigParser = configparser.ConfigParser()
@@ -73,17 +80,24 @@ def test_config_from_ini():
     assert cfg.client.use_tls is True
 
 
+def test_config_emailcerts():
+    """test retrieval of email/cert pair"""
+    email_list = [("email1", "cert1"), ("email2", "cert2")]
+    cfg = smtprd.Config._get_emails_and_certs(email_list)
+    assert cfg["email2"] == "cert2"
+
+
 def test_client_encrypt():
     """Test encryption. Keys were generated with
     openssl req -newkey rsa:1024 -nodes -x509 -days 365 -out signer.pem
     """
 
-    client = smtprd.SMTPClient(config())
-    encrypted = client._encrypt(b"abc", "subject")
+    client = smtprd.SMTPClient(config(), emails())
+    encrypted = client._encrypt(b"abc", "subject", "recipient")
     lines = encrypted.decode().splitlines()
     # Test format of header
     assert lines[0] == "From: " + str(config().sender)
-    assert lines[1] == "To: " + str(config().recipients[0])
+    assert lines[1] == "To: recipient"
     assert lines[2] == "Subject: " + "subject"
     assert lines[3] == "MIME-Version: 1.0"
     assert lines[4] == 'Content-Disposition: attachment; filename="smime.p7m"'
@@ -98,8 +112,9 @@ def test_client_encrypt():
         lines[8] == "MIIBdgYJKoZIhvcNAQcDoIIBZzCCAWMCAQAxggEeMIIBGgIBADCBgjBqMQswCQYD"
     )
 
+    # test decryption
     s = SMIME.SMIME()
-    s.load_key(config().smime_cert_private, config().smime_cert)
+    s.load_key(config().smime_cert_private, emails().email_certs["recipient"])
     buf = BIO.MemoryBuffer(encrypted)
     p7, _ = SMIME.smime_load_pkcs7_bio(buf)
     out = s.decrypt(p7)
@@ -108,13 +123,13 @@ def test_client_encrypt():
 
 def test_client_sign():
     """Test signing"""
-    client = smtprd.SMTPClient(config())
+    client = smtprd.SMTPClient(config(), emails())
     message = email.message.EmailMessage()
     message.set_content("Test to sign")
     # header are needed, because email.message.Emailmessage will add a
     # newline between the boundary and the content if no header is found
     message.add_header("From", config().sender)
-    message.add_header("To", config().recipients[0])
+    message.add_header("To", "recipient")
     message.add_header("Subject", "Test")
     signed = client._sign(message)
     assert "This is an S/MIME signed message" in signed.decode()