apply most of linkxt review comments

chatmaild/src/chatmaild/dictproxy.py

@@ -31,7 +31,9 @@ def encrypt_password(password: str):
 
 def create_user(db, user, password):
     if os.path.exists(NOCREATE_FILE):
-        logging.warning(f"Didn't create account: {NOCREATE_FILE} exists. Delete the file to enable account creation.")
+        logging.warning(
+            f"Didn't create account: {NOCREATE_FILE} exists. Delete the file to enable account creation."
+        )
         return
     with db.write_transaction() as conn:
         conn.create_user(user, password)

chatmaild/src/chatmaild/filtermail.py

@@ -3,6 +3,7 @@ import asyncio
 import logging
 from email.parser import BytesParser
 from email import policy
+from email.utils import parseaddr
 
 from aiosmtpd.lmtp import LMTP
 from aiosmtpd.controller import UnixSocketController
@@ -42,13 +43,33 @@ class ExampleHandler:
         return "250 OK"
 
     async def handle_DATA(self, server, session, envelope):
-        logging.info("Processing DATA message from %s", envelope.mail_from)
+        valid_recipients, res = lmtp_handle_DATA(envelope)
+        # Reinject the mail back into Postfix.
+        if valid_recipients:
+            logging.info("Reinjecting the mail")
+            client = SMTPClient("localhost", "10026")
+            client.sendmail(envelope.mail_from, valid_recipients, envelope.content)
+        else:
+            logging.info("no valid recipients, ignoring mail")
 
-        valid_recipients = []
+        return "\r\n".join(res)
+
+
+async def asyncmain(loop):
+    controller = ExampleController(
+        ExampleHandler(), unix_socket="/var/spool/postfix/private/filtermail"
+    )
+    controller.start()
+
+
+def lmtp_handle_DATA(envelope):
+    """the central filtering function for e-mails."""
+    logging.info(f"Processing DATA message from {envelope.mail_from}")
 
     message = BytesParser(policy=policy.default).parsebytes(envelope.content)
     mail_encrypted = check_encrypted(message)
 
+    valid_recipients = []
     res = []
     for recipient in envelope.rcpt_tos:
         my_local_domain = envelope.mail_from.split("@")
@@ -56,6 +77,12 @@ class ExampleHandler:
             res += [f"500 Invalid from address <{envelope.mail_from}>"]
             continue
 
+        _, from_addr = parseaddr(message.get("from").strip())
+        logging.info(f"mime-from: {from_addr} envelope-from: {envelope.mail_from}")
+        if envelope.mail_from.lower() != from_addr.lower():
+            res += [f"500 Invalid FROM <{from_addr}> for <{envelope.mail_from}>"]
+            continue
+
         if envelope.mail_from == recipient:
             # Always allow sending emails to self.
             valid_recipients += [recipient]
@@ -81,20 +108,9 @@ class ExampleHandler:
         valid_recipients += [recipient]
         res += ["250 OK"]
 
-        # Reinject the mail back into Postfix.
-        if valid_recipients:
-            logging.info("Reinjecting the mail")
-            client = SMTPClient("localhost", "10026")
-            client.sendmail(envelope.mail_from, valid_recipients, envelope.content)
-
-        return "\r\n".join(res)
-
-
-async def asyncmain(loop):
-    controller = ExampleController(
-        ExampleHandler(), unix_socket="/var/spool/postfix/private/filtermail"
-    )
-    controller.start()
+    assert len(envelope.rcpt_tos) == len(res)
+    assert len(valid_recipients) <= len(res)
+    return valid_recipients, res
 
 
 def main():

chatmaild/src/chatmaild/test_filtermail.py

@@ -1,8 +1,46 @@
-from .filtermail import check_encrypted
+from .filtermail import check_encrypted, lmtp_handle_DATA
 from email.parser import BytesParser
 from email import policy
 
 
+def test_reject_forged_from():
+    def makemail(from_addr):
+        return BytesParser(policy=policy.default).parsebytes(
+            "\r\n".join(
+                [
+                    f"From: <{from_addr}",
+                    "To: <barbaz@c3.testrun.org>",
+                    "Date: Sun, 15 Oct 2023 16:41:44 +0000",
+                    "Message-ID: <Mr.3gckbNy5bch.uK3Hd2Ws6-w@c2.testrun.org>",
+                    "References: <Mr.3gckbNy5bch.uK3Hd2Ws6-w@c2.testrun.org>",
+                    "Chat-Version: 1.0",
+                    "MIME-Version: 1.0",
+                    "Content-Type: text/plain; charset=utf-8; format=flowed; delsp=no",
+                    "",
+                    "Hi!",
+                    "",
+                    "",
+                ]
+            ).encode()
+        )
+
+    class envelope:
+        mail_from = "bob@c3.testrun.org"
+        rcpt_tos = ["somebody@c3.testrun.org"]
+
+    # test that the filter lets good mail through
+    envelope.content = makemail(envelope.mail_from).as_bytes()
+    valid_recipients, res = lmtp_handle_DATA(envelope=envelope)
+    assert valid_recipients == envelope.rcpt_tos
+    assert len(res) == 1 and "250" in res[0]
+
+    # test that the filter rejects forged mail
+    envelope.content = makemail("forged@c3.testrun.org").as_bytes()
+    valid_recipients, res = lmtp_handle_DATA(envelope=envelope)
+    assert not valid_recipients
+    assert len(res) == 1 and "500" in res[0]
+
+
 def test_filtermail():
     def check_encrypted_bstr(content):
         message = BytesParser(policy=policy.default).parsebytes(content)

online-tests/conftest.py

@@ -75,6 +75,24 @@ class ImapConn:
         print(f"imap-login {user!r} {password!r}")
         self.conn.login(user, password)
 
+    def fetch_all(self):
+        print("imap-fetch all")
+        status, res = self.conn.select()
+        if int(res[0]) == 0:
+            raise ValueError("no messages in imap folder")
+        status, results = self.conn.fetch("1:*", "(RFC822)")
+        assert status == "OK"
+        return results
+
+    def fetch_all_messages(self):
+        print("imap-fetch all messages")
+        results = self.fetch_all()
+        messages = []
+        for item in results:
+            if len(item) == 2:
+                messages.append(item[1].decode())
+        return messages
+
 
 @pytest.fixture
 def smtp(maildomain):
@@ -97,6 +115,11 @@ class SmtpConn:
         print(f"smtp-login {user!r} {password!r}")
         self.conn.login(user, password)
 
+    def sendmail(self, from_addr, to_addrs, msg):
+        print(f"smtp-sendmail from={from_addr!r} to_addrs={to_addrs!r}")
+        print(f"smtp-sendmail message size: {len(msg)}")
+        return self.conn.sendmail(from_addr=from_addr, to_addrs=to_addrs, msg=msg)
+
 
 @pytest.fixture(params=["imap", "smtp"])
 def imap_or_smtp(request):
@@ -198,4 +221,66 @@ class Remote:
         )
         while 1:
             line = self.popen.stdout.readline()
-            yield line.decode().strip().lower()
+            res = line.decode().strip().lower()
+            if res:
+                yield res
+            else:
+                break
+
+
+@pytest.fixture
+def mailgen(request):
+    class Mailgen:
+        def get_encrypted(self, from_addr, to_addr):
+            data = request.fspath.dirpath("mailgen/encrypted.eml").read()
+            return data.format(from_addr=from_addr, to_addr=to_addr)
+
+    return Mailgen()
+
+
+@pytest.fixture
+def cmsetup(maildomain, gencreds):
+    return CMSetup(maildomain, gencreds)
+
+
+class CMSetup:
+    def __init__(self, maildomain, gencreds):
+        self.maildomain = maildomain
+        self.gencreds = gencreds
+
+    def gen_users(self, num):
+        print(f"Creating {num} online users")
+        users = []
+        for i in range(num):
+            addr, password = self.gencreds()
+            user = CMUser(self.maildomain, addr, password)
+            assert user.smtp
+            users.append(user)
+        return users
+
+
+class CMUser:
+    def __init__(self, maildomain, addr, password):
+        self.maildomain = maildomain
+        self.addr = addr
+        self.password = password
+        self._smtp = None
+        self._imap = None
+
+    @property
+    def smtp(self):
+        if not self._smtp:
+            handle = SmtpConn(self.maildomain)
+            handle.connect()
+            handle.login(self.addr, self.password)
+            self._smtp = handle
+        return self._smtp
+
+    @property
+    def imap(self):
+        if not self._imap:
+            imap = ImapConn(self.maildomain)
+            imap.connect()
+            imap.login(self.addr, self.password)
+            self._imap = imap
+        return self._imap

online-tests/mailgen/encrypted.eml

@@ -0,0 +1,66 @@
+From: {from_addr}
+To: {to_addr}
+Subject: ...
+Date: Sun, 15 Oct 2023 16:43:21 +0000
+Message-ID: <Mr.UVyJWZmkCKM.hGzNc6glBE_@c2.testrun.org>
+In-Reply-To: <Mr.MvmCz-GQbi_.6FGRkhDf05c@c2.testrun.org>
+References: <Mr.3gckbNy5bch.uK3Hd2Ws6-w@c2.testrun.org>
+	<Mr.MvmCz-GQbi_.6FGRkhDf05c@c2.testrun.org>
+Chat-Version: 1.0
+Autocrypt: addr={from_addr}; prefer-encrypt=mutual;
+	keydata=xjMEZSwWjhYJKwYBBAHaRw8BAQdAQBEhqeJh0GueHB6kF/DUQqYCxARNBVokg/AzT+7LqH
+	rNFzxiYXJiYXpAYzIudGVzdHJ1bi5vcmc+wosEEBYIADMCGQEFAmUsFo4CGwMECwkIBwYVCAkKCwID
+	FgIBFiEEFTfUNvVnY3b9F7yHnmme1PfUhX8ACgkQnmme1PfUhX9A4AEAnHWHp49eBCMHK5t66gYPiW
+	XQuB1mwUjzGfYWB+0RXUoA/0xcQ3FbUNlGKW7Blp6eMFfViv6Mv2d3kNSXACB6nmcMzjgEZSwWjhIK
+	KwYBBAGXVQEFAQEHQBpY5L2M1XHo0uxf8SX1wNLBp/OVvidoWHQF2Jz+kJsUAwEIB8J4BBgWCAAgBQ
+	JlLBaOAhsMFiEEFTfUNvVnY3b9F7yHnmme1PfUhX8ACgkQnmme1PfUhX/INgEA37AJaNvruYsJVanP
+	IXnYw4CKd55UAwl8Zcy+M2diAbkA/0fHHcGV4r78hpbbL1Os52DPOdqYQRauIeJUeG+G6bQO
+MIME-Version: 1.0
+Content-Type: multipart/encrypted; protocol="application/pgp-encrypted";
+	boundary="YFrteb74qSXmggbOxZL9dRnhymywAi"
+
+
+--YFrteb74qSXmggbOxZL9dRnhymywAi
+Content-Description: PGP/MIME version identification
+Content-Type: application/pgp-encrypted
+
+Version: 1
+
+
+--YFrteb74qSXmggbOxZL9dRnhymywAi
+Content-Description: OpenPGP encrypted message
+Content-Disposition: inline; filename="encrypted.asc";
+Content-Type: application/octet-stream; name="encrypted.asc"
+
+-----BEGIN PGP MESSAGE-----
+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+=agR5
+-----END PGP MESSAGE-----
+
+
+--YFrteb74qSXmggbOxZL9dRnhymywAi--
+
+

online-tests/test_0_basic.py

@@ -1,3 +1,7 @@
+import smtplib
+import pytest
+
+
 def test_remote(remote, imap_or_smtp):
     lineproducer = remote.iter_output(imap_or_smtp.logcmd)
     imap_or_smtp.connect()
@@ -13,3 +17,36 @@ def test_use_two_chatmailservers(cmfactory, maildomain2):
     domain1 = ac1.get_config("addr").split("@")[1]
     domain2 = ac2.get_config("addr").split("@")[1]
     assert domain1 != domain2
+
+
+@pytest.mark.parametrize("forgeaddr", ["internal", "someone@example.org"])
+def test_reject_forged_from(cmsetup, mailgen, lp, remote, forgeaddr):
+    user1, user3 = cmsetup.gen_users(2)
+
+    lp.sec("send encrypted message with forged from")
+    print("envelope_from", user1.addr)
+    if forgeaddr == "internal":
+        addr_to_forge = cmsetup.gen_users(1)[0].addr
+    else:
+        addr_to_forge = "someone@example.org"
+
+    print("message to inject:")
+    msg = mailgen.get_encrypted(from_addr=addr_to_forge, to_addr=user3.addr)
+    for line in msg.split("\n")[:4]:
+        print(f"   {line}")
+
+    lp.sec("Send forged mail and check remote postfix lmtp processing result")
+    remote_log = remote.iter_output("journalctl -t postfix/lmtp")
+    user1.smtp.sendmail(from_addr=user1.addr, to_addrs=[user3.addr], msg=msg)
+    for line in remote_log:
+        # print(line)
+        if "500 invalid from" in line and user3.addr in line:
+            break
+    else:
+        pytest.fail("remote postfix/filtermail failed to reject message")
+
+    # check that the logged in user (who sent the forged msg) got a non-delivery notice
+    for message in user1.imap.fetch_all_messages():
+        if "Invalid FROM" in message and addr_to_forge in message:
+            return
+    pytest.fail(f"forged From={addr_to_forge} did not cause non-delivery notice")