From 2d0fc2e70e988263460105b5271588eaf992476f Mon Sep 17 00:00:00 2001
From: holger krekel <holger@merlinux.eu>
Date: Mon, 24 Aug 2026 23:18:43 +0200
Subject: [PATCH] feat: move doveauth from dictproxy to lua/http

1. existing logins are now verified by lua only

2. non-existing logins are delegated to the new Python doveauth http /create endpoint

Using Lua and http this way makes doveauth more compatible to dovecot 2.4
---
 chatmaild/src/chatmaild/config.py             |   1 +
 chatmaild/src/chatmaild/doveauth.py           | 206 ++++++------
 .../tests/test_delete_inactive_users.py       |   6 +-
 .../src/chatmaild/tests/test_doveauth.py      | 308 ++++++++++--------
 .../src/chatmaild/tests/test_lastlogin.py     |   6 +-
 .../src/chatmaild/tests/test_migrate_db.py    |   2 +-
 chatmaild/src/chatmaild/tests/test_user.py    |  17 +-
 chatmaild/src/chatmaild/user.py               |  15 +-
 cmdeploy/pyproject.toml                       |   1 +
 cmdeploy/src/cmdeploy/dovecot/auth.conf       |  12 -
 cmdeploy/src/cmdeploy/dovecot/auth.lua.j2     |  64 ++++
 cmdeploy/src/cmdeploy/dovecot/deployer.py     |   5 +-
 cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2 |   8 +-
 cmdeploy/src/cmdeploy/pins.py                 |   2 +
 .../src/cmdeploy/service/doveauth.service.f   |   7 +-
 cmdeploy/src/cmdeploy/tests/test_authlua.py   | 206 ++++++++++++
 .../cmdeploy/tests/test_dovecot_deployer.py   |  10 +-
 doc/source/overview.rst                       |  13 +-
 18 files changed, 593 insertions(+), 296 deletions(-)
 delete mode 100644 cmdeploy/src/cmdeploy/dovecot/auth.conf
 create mode 100644 cmdeploy/src/cmdeploy/dovecot/auth.lua.j2
 create mode 100644 cmdeploy/src/cmdeploy/tests/test_authlua.py

diff --git a/chatmaild/src/chatmaild/config.py b/chatmaild/src/chatmaild/config.py
index 21f817e7..09085742 100644
--- a/chatmaild/src/chatmaild/config.py
+++ b/chatmaild/src/chatmaild/config.py
@@ -55,6 +55,7 @@ class Config:
         self.postfix_reinject_port_incoming = int(
             params.pop("postfix_reinject_port_incoming", "10026")
         )
+        self.doveauth_http_port = int(params.pop("doveauth_http_port", "10084"))
         self.mtail_address = params.pop("mtail_address", None)
         self.disable_ipv6 = params.pop("disable_ipv6", "false").lower() == "true"
         self.acme_email = params.pop("acme_email", "")
diff --git a/chatmaild/src/chatmaild/doveauth.py b/chatmaild/src/chatmaild/doveauth.py
index eb0ea918..315a30f4 100644
--- a/chatmaild/src/chatmaild/doveauth.py
+++ b/chatmaild/src/chatmaild/doveauth.py
@@ -1,10 +1,17 @@
-import json
+"""Create chatmail addresses on first login.
+
+Dovecot only asks us about addresses it does not already find in the mailbox:
+the auth.lua we deploy with dovecot (cmdeploy/src/cmdeploy/dovecot/auth.lua.j2)
+verifies existing users itself against a mailbox password file,
+and HTTP-POSTs everything else to the /create endpoint implemented in this module.
+"""
+
 import logging
 import os
 import re
 import sys
-
-import filelock
+import threading
+from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
 
 try:
     import crypt_r
@@ -12,7 +19,6 @@ except ImportError:
     import crypt as crypt_r
 
 from .config import Config, read_config
-from .dictproxy import DictProxy
 from .migrate_db import migrate_from_db_to_maildir
 from .syslimits import has_sufficient_resources
 
@@ -64,109 +70,117 @@ def is_allowed_to_create(config: Config, user, cleartext_password) -> bool:
     return True
 
 
-def split_and_unescape(s):
-    """Split strings using double quote as a separator and backslash as escape character
-    into parts."""
-
-    out = ""
-    i = 0
-    while i < len(s):
-        c = s[i]
-        if c == "\\":
-            # Skip escape character.
-            i += 1
-
-            # This will raise IndexError if there is no character
-            # after escape character. This is expected
-            # as this is an invalid input.
-            out += s[i]
-        elif c == '"':
-            # Separator
-            yield out
-            out = ""
-        else:
-            out += c
-        i += 1
-    yield out
+def verify_password(stored, cleartext_password) -> bool:
+    if stored.startswith("{"):
+        stored = stored.split("}", 1)[1]
+    return crypt_r.crypt(cleartext_password, stored) == stored
 
 
-class AuthDictProxy(DictProxy):
+class DoveAuth:
     def __init__(self, config):
-        super().__init__()
         self.config = config
+        self.creation_lock = threading.Lock()
 
-    def handle_lookup(self, parts):
-        # Dovecot <2.3.17 has only one part,
-        # do not attempt to read any other parts for compatibility.
-        keyname = parts[0]
-
-        namespace, type, args = keyname.split("/", 2)
-        args = list(split_and_unescape(args))
-
+    def create_user(self, addr, cleartext_password) -> bool:
+        """Create the address, or verify the password if it exists already."""
         config = self.config
-        reply_command = "F"
-        res = ""
-        if namespace == "shared":
-            if type == "userdb":
-                user = args[0]
-                if user.endswith(f"@{config.mail_domain}"):
-                    res = self.lookup_userdb(user)
-                if res:
-                    reply_command = "O"
-                else:
-                    reply_command = "N"
-            elif type == "passdb":
-                user = args[1]
-                if user.endswith(f"@{config.mail_domain}"):
-                    res = self.lookup_passdb(user, cleartext_password=args[0])
-                if res:
-                    reply_command = "O"
-                else:
-                    reply_command = "N"
-        json_res = json.dumps(res) if res else ""
-        return f"{reply_command}{json_res}\n"
-
-    def handle_iterate(self, parts):
-        # example: I0\t0\tshared/userdb/
-        if parts[2] == "shared/userdb/":
-            result = "".join(
-                f"Oshared/userdb/{user}\t\n" for user in self.iter_userdb()
-            )
-            return f"{result}\n"
-
-    def iter_userdb(self) -> list:
-        """Get a list of all user addresses."""
-        return [x for x in os.listdir(self.config.mailboxes_dir) if "@" in x]
-
-    def lookup_userdb(self, addr):
-        return self.config.get_user(addr).get_userdb_dict()
-
-    def lookup_passdb(self, addr, cleartext_password):
-        user = self.config.get_user(addr)
-        userdata = user.get_userdb_dict()
-        if userdata:
-            return userdata
-        if not is_allowed_to_create(self.config, addr, cleartext_password):
-            return
-        if not has_sufficient_resources(self.config):
-            return
-
-        lock = filelock.FileLock(str(user.password_path) + ".lock", timeout=5)
-        with lock:
-            userdata = user.get_userdb_dict()
-            if userdata:
-                return userdata
+        if not addr.endswith(f"@{config.mail_domain}"):
+            logging.warning("address not in mail domain: %r", addr)
+            return False
+        try:
+            user = config.get_user(addr)
+        except ValueError:
+            logging.warning("invalid address: %r", addr)
+            return False
+        with self.creation_lock:
+            passhash = user.get_password_hash()
+            if passhash is not None:
+                # a concurrent first login may have just created the address
+                return verify_password(passhash, cleartext_password)
+            if not is_allowed_to_create(config, addr, cleartext_password):
+                return False
+            if not has_sufficient_resources(config):
+                return False
             user.set_password(encrypt_password(cleartext_password))
-            print(f"Created address: {addr}", file=sys.stderr)
-        return user.get_userdb_dict()
+        # mtail counts created_accounts off this exact line
+        print(f"Created address: {addr}", file=sys.stderr)
+        return True
+
+
+class CreateHandler(BaseHTTPRequestHandler):
+    """Answer POST /create requests from dovecot's auth.lua, body `addr\\tpassword`.
+
+    The body must be UTF-8 and only the first tab separates the fields,
+    so a password may itself contain tabs.
+    Any non-UTF8 or \\0 bytes in the body fail the request.
+
+    Addresses are ASCII: dovecot refuses any login name outside its
+    auth_username_chars before auth.lua ever sees it.
+
+    Dovecot hands auth.lua the exact password bytes the client sent;
+    decoding and re-encoding UTF-8 is byte-identical,
+    so dovecot's password_verify later recomputes the same hash crypt() stores here.
+    """
+
+    protocol_version = "HTTP/1.1"  # dovecot's HTTP client reuses connections
+
+    max_body_len = 512  # an address and a password
+
+    def do_POST(self):
+        if self.path != "/create":
+            self.reply(404)
+            return
+        length = self.body_length()
+        if length is None:
+            self.reply(400)
+            return
+        body = self.rfile.read(length)
+        try:
+            addr, _, password = body.decode("utf-8").partition("\t")
+        except UnicodeDecodeError:
+            self.reply(400)
+            return
+        if "\0" in addr or "\0" in password:
+            self.reply(400)
+            return
+        self.reply(200 if self.server.doveauth.create_user(addr, password) else 403)
+
+    def body_length(self):
+        try:
+            length = int(self.headers["Content-Length"])
+        except (TypeError, ValueError):
+            return None
+        return length if 0 <= length <= self.max_body_len else None
+
+    def reply(self, status):
+        self.send_response(status)
+        self.send_header("Content-Length", "0")
+        if status != 200:
+            # Just close on any failure, as body might not be fully read.
+            # It's anyway cheap to re-establish http localhost without TLS.
+            self.send_header("Connection", "close")
+        self.end_headers()
+
+    def log_message(self, format, *args):
+        # the per-request access log would only duplicate our own stderr lines
+        pass
+
+
+class DoveAuthServer(ThreadingHTTPServer):
+    # a burst of first-time logins (e.g. from CI) must not overflow
+    # the accept queue, see https://github.com/chatmail/relay/issues/436
+    request_queue_size = 1000
+
+    def __init__(self, config, port):
+        super().__init__(("127.0.0.1", port), CreateHandler)
+        self.doveauth = DoveAuth(config)
 
 
 def main():
-    socket, cfgpath = sys.argv[1:]
+    (cfgpath,) = sys.argv[1:]
     config = read_config(cfgpath)
 
     migrate_from_db_to_maildir(config)
 
-    dictproxy = AuthDictProxy(config=config)
-
-    dictproxy.serve_forever_from_socket(socket)
+    server = DoveAuthServer(config, config.doveauth_http_port)
+    server.serve_forever()
diff --git a/chatmaild/src/chatmaild/tests/test_delete_inactive_users.py b/chatmaild/src/chatmaild/tests/test_delete_inactive_users.py
index 6a60362a..ecc3325a 100644
--- a/chatmaild/src/chatmaild/tests/test_delete_inactive_users.py
+++ b/chatmaild/src/chatmaild/tests/test_delete_inactive_users.py
@@ -1,6 +1,6 @@
 import time
 
-from chatmaild.doveauth import AuthDictProxy
+from chatmaild.doveauth import DoveAuth
 from chatmaild.expire import daily_expire_main as main_expire
 
 
@@ -18,10 +18,10 @@ def test_login_timestamps(example_config):
 def test_delete_inactive_users(example_config):
     new = time.time()
     old = new - (example_config.delete_inactive_users_after * 86400) - 1
-    dictproxy = AuthDictProxy(example_config)
+    doveauth = DoveAuth(example_config)
 
     def create_user(addr, last_login):
-        dictproxy.lookup_passdb(addr, "q9mr3faue")
+        doveauth.create_user(addr, "q9mr3faue")
         user = example_config.get_user(addr)
         user.maildir.joinpath("cur").mkdir()
         user.maildir.joinpath("cur", "something").mkdir()
diff --git a/chatmaild/src/chatmaild/tests/test_doveauth.py b/chatmaild/src/chatmaild/tests/test_doveauth.py
index c2057196..94e99d6f 100644
--- a/chatmaild/src/chatmaild/tests/test_doveauth.py
+++ b/chatmaild/src/chatmaild/tests/test_doveauth.py
@@ -1,42 +1,37 @@
-import io
-import json
-import queue
+import http.client
 import threading
-import traceback
+from concurrent.futures import ThreadPoolExecutor
 
 import pytest
 
 import chatmaild.doveauth
 from chatmaild.doveauth import (
-    AuthDictProxy,
+    CreateHandler,
+    DoveAuth,
+    DoveAuthServer,
     is_allowed_to_create,
 )
 from chatmaild.newemail import create_newemail_dict
 
 
 @pytest.fixture
-def dictproxy(example_config):
-    return AuthDictProxy(config=example_config)
+def doveauth(example_config):
+    return DoveAuth(example_config)
 
 
-def test_basic(dictproxy, example_gencreds):
+def stored_hash(config, addr):
+    return config.get_user(addr).get_password_hash()
+
+
+def test_basic(doveauth, example_config, example_gencreds):
     addr, password = example_gencreds()
-    dictproxy.lookup_passdb(addr, password)
-    data = dictproxy.lookup_userdb(addr)
-    assert data
-    data2 = dictproxy.lookup_passdb(addr, password)
-    assert data == data2
+    assert doveauth.create_user(addr, password)
+    passhash = stored_hash(example_config, addr)
+    assert passhash.startswith("{SHA512-CRYPT}")
 
-
-def test_iterate_addresses(dictproxy):
-    addresses = []
-
-    for i in range(10):
-        addresses.append(f"asdf1234{i}@chat.example.org")
-        dictproxy.lookup_passdb(addresses[-1], "q9mr3faue")
-
-    res = dictproxy.iter_userdb()
-    assert set(res) == set(addresses)
+    # a second login verifies against the stored hash and rewrites nothing
+    assert doveauth.create_user(addr, password)
+    assert stored_hash(example_config, addr) == passhash
 
 
 def test_invalid_username_length(example_config):
@@ -53,75 +48,32 @@ def test_invalid_username_length(example_config):
     )
 
 
-def test_dont_overwrite_password_on_wrong_login(dictproxy):
-    """Test that logging in with a different password doesn't create a new user"""
-    res = dictproxy.lookup_passdb(
-        "newuser12@chat.example.org", "kajdlkajsldk12l3kj1983"
-    )
-    assert res["password"]
-    res2 = dictproxy.lookup_passdb("newuser12@chat.example.org", "kajdslqwe")
-    # this function always returns a password hash, which is actually compared by dovecot.
-    assert res["password"] == res2["password"]
+def test_dont_overwrite_password_on_wrong_login(doveauth, example_config):
+    addr = "newuser12@chat.example.org"
+    assert doveauth.create_user(addr, "kajdlkajsldk12l3kj1983")
+    passhash = stored_hash(example_config, addr)
+
+    assert not doveauth.create_user(addr, "kajdslqwe")
+    assert stored_hash(example_config, addr) == passhash
+
+    assert doveauth.create_user(addr, "kajdlkajsldk12l3kj1983")
+    assert stored_hash(example_config, addr) == passhash
 
 
-def test_nocreate_file(monkeypatch, tmpdir, dictproxy):
+def test_foreign_domain_is_refused(doveauth):
+    assert not doveauth.create_user("newuser12@evil.example.org", "qlwkejqlwe12")
+
+
+def test_nocreate_file(monkeypatch, tmpdir, doveauth, example_config):
     p = tmpdir.join("nocreate")
     p.write("")
     monkeypatch.setattr(chatmaild.doveauth, "NOCREATE_FILE", str(p))
-    dictproxy.lookup_passdb("newuser12@chat.example.org", "zequ0Aimuchoodaechik")
-    assert not dictproxy.lookup_userdb("newuser12@chat.example.org")
-
-
-def test_handle_dovecot_request(dictproxy):
-    transactions = {}
-    # Test that password can contain ", ', \ and /
-    msg = (
-        'Lshared/passdb/laksjdlaksjdlak\\\\sjdlk\\"12j\\\'3l1/k2j3123"'
-        "some42123@chat.example.org\tsome42123@chat.example.org"
-    )
-    res = dictproxy.handle_dovecot_request(msg, transactions)
-    assert res
-    assert res[0] == "O" and res.endswith("\n")
-    userdata = json.loads(res[1:].strip())
-    assert userdata["home"].endswith("chat.example.org/some42123@chat.example.org")
-    assert userdata["uid"] == userdata["gid"] == "vmail"
-    assert userdata["password"].startswith("{SHA512-CRYPT}")
-
-
-def test_handle_dovecot_protocol_hello_is_skipped(example_config, caplog):
-    dictproxy = AuthDictProxy(config=example_config)
-    rfile = io.BytesIO(b"H3\t2\t0\t\tauth\n")
-    wfile = io.BytesIO()
-    dictproxy.loop_forever(rfile, wfile)
-    assert wfile.getvalue() == b""
-    assert not caplog.messages
-
-
-def test_handle_dovecot_protocol_user_not_exists(example_config):
-    dictproxy = AuthDictProxy(config=example_config)
-    rfile = io.BytesIO(
-        b"H3\t2\t0\t\tauth\nLshared/userdb/foobar@chat.example.org\tfoobar@chat.example.org\n"
-    )
-    wfile = io.BytesIO()
-    dictproxy.loop_forever(rfile, wfile)
-    assert wfile.getvalue() == b"N\n"
-
-
-def test_handle_dovecot_protocol_iterate(example_config):
-    dictproxy = AuthDictProxy(config=example_config)
-    dictproxy.lookup_passdb("asdf00000@chat.example.org", "q9mr3faue")
-    dictproxy.lookup_passdb("asdf11111@chat.example.org", "q9mr3faue")
-    rfile = io.BytesIO(b"H3\t2\t0\t\tauth\nI0\t0\tshared/userdb/")
-    wfile = io.BytesIO()
-    dictproxy.loop_forever(rfile, wfile)
-    lines = wfile.getvalue().decode("ascii").split("\n")
-    assert "Oshared/userdb/asdf00000@chat.example.org\t" in lines
-    assert "Oshared/userdb/asdf11111@chat.example.org\t" in lines
-    assert not lines[2]
+    addr = "newuser12@chat.example.org"
+    assert not doveauth.create_user(addr, "zequ0Aimuchoodaechik")
+    assert stored_hash(example_config, addr) is None
 
 
 def test_invalid_localpart_characters(make_config):
-    """Test that is_allowed_to_create rejects localparts with invalid characters."""
     config = make_config("chat.example.org", {"username_min_length": "3"})
     password = "zequ0Aimuchoodaechik"
     domain = config.mail_domain
@@ -141,78 +93,150 @@ def test_invalid_localpart_characters(make_config):
     assert not is_allowed_to_create(config, f"ab@cdef@{domain}", password)
     assert not is_allowed_to_create(config, f"abc/def@{domain}", password)
     assert not is_allowed_to_create(config, f"abc\\def@{domain}", password)
+    assert not is_allowed_to_create(config, f"üser123@{domain}", password)
 
 
-def test_concurrent_creation_same_account(dictproxy):
-    """Test that concurrent creation of the same account doesn't corrupt password."""
+def test_concurrent_creation_same_account(doveauth, example_config, capsys):
     addr = "racetest1@chat.example.org"
     password = "zequ0Aimuchoodaechik"
-    num_threads = 10
-    results = queue.Queue()
 
-    def create():
-        try:
-            res = dictproxy.lookup_passdb(addr, password)
-            results.put(("ok", res))
-        except Exception:
-            results.put(("err", traceback.format_exc()))
-
-    threads = [threading.Thread(target=create, daemon=True) for _ in range(num_threads)]
-    for t in threads:
-        t.start()
-    for t in threads:
-        t.join(timeout=10)
-
-    passwords_seen = set()
-    for _ in range(num_threads):
-        status, res = results.get()
-        if status == "err":
-            pytest.fail(f"concurrent creation failed\n{res}")
-        passwords_seen.add(res["password"])
+    def create(_):
+        ok = doveauth.create_user(addr, password)
+        return ok, stored_hash(example_config, addr)
 
+    with ThreadPoolExecutor(10) as pool:
+        results = list(pool.map(create, range(10)))
+    assert all(ok for ok, _ in results)
     # all threads must see the same password hash
-    assert len(passwords_seen) == 1
-
-
-def test_50_concurrent_lookups_different_accounts(example_gencreds, dictproxy):
-    num_threads = 50
-    req_per_thread = 5
-    results = queue.Queue()
-
-    def lookup():
-        for i in range(req_per_thread):
-            addr, password = example_gencreds()
-            try:
-                dictproxy.lookup_passdb(addr, password)
-            except Exception:
-                results.put(traceback.format_exc())
-            else:
-                results.put(None)
-
-    threads = []
-    for i in range(num_threads):
-        thread = threading.Thread(target=lookup, daemon=True)
-        threads.append(thread)
-
-    print(f"created {num_threads} threads, starting them and waiting for results")
-    for thread in threads:
-        thread.start()
-
-    for i in range(num_threads * req_per_thread):
-        res = results.get()
-        if res is not None:
-            pytest.fail(f"concurrent lookup failed\n{res}")
+    assert len({passhash for _, passhash in results}) == 1
+    assert capsys.readouterr().err.count("Created address:") == 1
 
 
 def test_insufficient_resources_block_creation_not_existing_logins(
-    dictproxy, example_gencreds, monkeypatch
+    doveauth, example_gencreds, monkeypatch
 ):
     addr, password = example_gencreds()
-    assert dictproxy.lookup_passdb(addr, password)
+    assert doveauth.create_user(addr, password)
 
     monkeypatch.setattr(
         chatmaild.doveauth, "has_sufficient_resources", lambda config: False
     )
     newaddr, newpassword = example_gencreds()
-    assert not dictproxy.lookup_passdb(newaddr, newpassword)
-    assert dictproxy.lookup_passdb(addr, password)
+    assert not doveauth.create_user(newaddr, newpassword)
+    assert doveauth.create_user(addr, password)
+
+
+class TestHttpPost:
+    @pytest.fixture
+    def doveauth_server(self, example_config):
+        server = DoveAuthServer(example_config, port=0)
+        threading.Thread(target=server.serve_forever, daemon=True).start()
+        yield f"127.0.0.1:{server.server_address[1]}"
+        server.shutdown()
+        server.server_close()
+
+    @pytest.fixture
+    def post(self, doveauth_server):
+        def post(path, data):
+            conn = http.client.HTTPConnection(doveauth_server, timeout=10)
+            try:
+                return self.post_on(conn, path, data).status
+            finally:
+                conn.close()
+
+        return post
+
+    @pytest.fixture
+    def connection(self, doveauth_server):
+        """One kept-alive connection, which is all dovecot's HTTP client opens."""
+        conn = http.client.HTTPConnection(doveauth_server, timeout=10)
+        yield conn
+        conn.close()
+
+    @staticmethod
+    def post_on(conn, path, data):
+        conn.request("POST", path, body=data)
+        resp = conn.getresponse()
+        resp.read()
+        return resp
+
+    def test_create_and_verify(self, post, example_config, example_gencreds):
+        addr, password = example_gencreds()
+        assert post("/create", f"{addr}\t{password}".encode()) == 200
+        assert stored_hash(example_config, addr).startswith("{SHA512-CRYPT}")
+
+        # second login with the same password verifies, a wrong one is refused
+        assert post("/create", f"{addr}\t{password}".encode()) == 200
+        assert post("/create", f"{addr}\twrong{password}".encode()) == 403
+
+    def test_password_special_chars_survive_transport(self, post, example_gencreds):
+        addr, _ = example_gencreds()
+        password = "laksjdlaksjdlak\\sjdlk\"12j'3l1/k2\tj3123"
+        body = f"{addr}\t{password}".encode()
+        assert post("/create", body) == 200
+        assert post("/create", body) == 200
+        assert post("/create", f"{addr}\totherpassword1".encode()) == 403
+
+    def test_password_must_be_utf8(self, post, example_gencreds):
+        addr, _ = example_gencreds()
+        assert post("/create", f"{addr}\tpässwort12".encode()) == 200
+        assert post("/create", addr.encode() + b"\tp\xe4sswort12") == 400
+
+    def test_nul_is_refused_before_crypt_sees_it(self, post, example_gencreds):
+        addr, _ = example_gencreds()
+        assert post("/create", f"{addr}\tpass\0word12".encode()) == 400
+        assert (
+            post("/create", "us\0er12345@chat.example.org\tlongenough1".encode()) == 400
+        )
+
+    def test_refused_creation(self, post, example_gencreds):
+        addr, _ = example_gencreds()
+        assert post("/create", f"{addr}\tshort".encode()) == 403
+        assert post("/create", b"not-an-address\tlongenoughpassword") == 403
+        body = "bürger123@chat.example.org\tlongenoughpw".encode()
+        assert post("/create", body) == 403
+        assert post("/create", b"") == 403
+
+    def test_body_length_limit(self, post, example_gencreds):
+        addr, _ = example_gencreds()
+        fill = CreateHandler.max_body_len - len(addr) - len("\t")
+        body = f"{addr}\t{'x' * fill}".encode()
+        assert len(body) == CreateHandler.max_body_len
+        assert post("/create", body) == 200
+
+        body = f"{addr}\t{'x' * (fill + 1)}".encode()
+        assert len(body) == CreateHandler.max_body_len + 1
+        assert post("/create", body) == 400
+
+    def test_connection_is_reused_across_200_replies(
+        self, connection, example_gencreds
+    ):
+        addr, password = example_gencreds()
+        body = f"{addr}\t{password}".encode()
+        # create, then verify the same password, on one connection
+        for _ in range(2):
+            resp = self.post_on(connection, "/create", body)
+            assert (resp.status, resp.will_close) == (200, False)
+
+    @pytest.mark.parametrize(
+        "path,data,status",
+        [
+            ("/other", b"not read", 404),
+            ("/create", b"x" * (CreateHandler.max_body_len + 1), 400),
+            ("/create", b"not-an-address\tlongenoughpassword", 403),
+        ],
+    )
+    def test_error_replies_close_the_connection(self, connection, path, data, status):
+        resp = self.post_on(connection, path, data)
+        assert (resp.status, resp.will_close) == (status, True)
+
+    @pytest.mark.parametrize("content_length", [None, "-1", "notanumber", "999999"])
+    def test_bad_content_length(self, connection, content_length):
+        # the fixture timeout turns a server that waits for the body into a failure
+        connection.putrequest("POST", "/create", skip_accept_encoding=True)
+        if content_length is not None:
+            connection.putheader("Content-Length", content_length)
+        connection.endheaders()
+        resp = connection.getresponse()
+        assert resp.status == 400
+        assert resp.will_close
diff --git a/chatmaild/src/chatmaild/tests/test_lastlogin.py b/chatmaild/src/chatmaild/tests/test_lastlogin.py
index a7e9e348..e4e8e81b 100644
--- a/chatmaild/src/chatmaild/tests/test_lastlogin.py
+++ b/chatmaild/src/chatmaild/tests/test_lastlogin.py
@@ -1,6 +1,6 @@
 import time
 
-from chatmaild.doveauth import AuthDictProxy
+from chatmaild.doveauth import DoveAuth
 from chatmaild.lastlogin import (
     LastLoginDictProxy,
 )
@@ -9,8 +9,8 @@ from chatmaild.lastlogin import (
 def test_handle_dovecot_request_last_login(testaddr, example_config):
     dictproxy = LastLoginDictProxy(config=example_config)
 
-    authproxy = AuthDictProxy(config=example_config)
-    authproxy.lookup_passdb(testaddr, "1l2k3j1l2k3jl123")
+    doveauth = DoveAuth(example_config)
+    doveauth.create_user(testaddr, "1l2k3j1l2k3jl123")
 
     dictproxy_transactions = {}
 
diff --git a/chatmaild/src/chatmaild/tests/test_migrate_db.py b/chatmaild/src/chatmaild/tests/test_migrate_db.py
index 7313939a..1763a559 100644
--- a/chatmaild/src/chatmaild/tests/test_migrate_db.py
+++ b/chatmaild/src/chatmaild/tests/test_migrate_db.py
@@ -63,7 +63,7 @@ def test_migration(tmp_path, example_config, caplog):
         user = example_config.get_user(path.name)
         if last_login:
             assert user.get_last_login_timestamp() == last_login
-        assert password == user.get_userdb_dict()["password"]
+        assert password == user.get_password_hash()
 
     assert not all
     assert not example_config.passdb_path.exists()
diff --git a/chatmaild/src/chatmaild/tests/test_user.py b/chatmaild/src/chatmaild/tests/test_user.py
index 3e7b5063..aca1a057 100644
--- a/chatmaild/src/chatmaild/tests/test_user.py
+++ b/chatmaild/src/chatmaild/tests/test_user.py
@@ -8,28 +8,23 @@ def test_login_timestamp(testaddr, example_config):
     assert user.get_last_login_timestamp() == 86400 * 2
 
 
-def test_get_user_dict_not_set(testaddr, example_config, caplog):
+def test_get_password_hash_not_set(testaddr, example_config, caplog):
     user = example_config.get_user(testaddr)
     assert not caplog.records
-    assert user.get_userdb_dict() == {}
+    assert user.get_password_hash() is None
     assert len(caplog.records) == 0
 
     user.set_password("")
-    assert user.get_userdb_dict() == {}
+    assert user.get_password_hash() is None
     assert len(caplog.records) == 1
 
 
-def test_get_user_dict(make_config, tmp_path):
+def test_get_password_hash(make_config, tmp_path):
     config = make_config("something.testrun.org")
-    addr = "user1@something.org"
-    user = config.get_user(addr)
+    user = config.get_user("user1@something.org")
     enc_password = "l1k2j31lk2j3l1k23j123"
     user.set_password(enc_password)
-    data = user.get_userdb_dict()
-    assert addr in str(data["home"])
-    assert data["uid"] == "vmail"
-    assert data["gid"] == "vmail"
-    assert data["password"] == enc_password
+    assert user.get_password_hash() == enc_password
 
 
 def test_no_mailboxes_dir(testaddr, example_config, tmp_path):
diff --git a/chatmaild/src/chatmaild/user.py b/chatmaild/src/chatmaild/user.py
index 3a86958e..27c0fe83 100644
--- a/chatmaild/src/chatmaild/user.py
+++ b/chatmaild/src/chatmaild/user.py
@@ -21,20 +21,17 @@ class User:
     def can_track(self):
         return "@" in self.addr
 
-    def get_userdb_dict(self):
-        """Return a non-empty dovecot 'userdb' style dict
-        if the user has an existing non-empty password"""
+    def get_password_hash(self):
         try:
-            pw = self.password_path.read_text()
+            passhash = self.password_path.read_text()
         except FileNotFoundError:
-            return {}
+            return None
 
-        if not pw:
+        if not passhash:
             logging.error(f"password is empty for: {self.addr}")
-            return {}
+            return None
 
-        home = str(self.maildir)
-        return dict(addr=self.addr, home=home, uid=self.uid, gid=self.gid, password=pw)
+        return passhash
 
     def is_incoming_cleartext_ok(self):
         return not self.enforce_E2EE_path.exists()
diff --git a/cmdeploy/pyproject.toml b/cmdeploy/pyproject.toml
index 272cb45a..a372ccaf 100644
--- a/cmdeploy/pyproject.toml
+++ b/cmdeploy/pyproject.toml
@@ -19,6 +19,7 @@ dependencies = [
   "pytest-xdist", 
   "execnet",
   "imap_tools",
+  "jinja2",
   "lupa",
   "deltachat-rpc-client",
   "deltachat-rpc-server",
diff --git a/cmdeploy/src/cmdeploy/dovecot/auth.conf b/cmdeploy/src/cmdeploy/dovecot/auth.conf
deleted file mode 100644
index fe40a9b0..00000000
--- a/cmdeploy/src/cmdeploy/dovecot/auth.conf
+++ /dev/null
@@ -1,12 +0,0 @@
-uri = proxy:/run/doveauth/doveauth.socket:auth
-iterate_disable = no
-iterate_prefix = userdb/
-
-default_pass_scheme = plain
-# %E escapes characters " (double quote), ' (single quote) and \ (backslash) with \ (backslash).
-# See <https://doc.dovecot.org/2.3/configuration_manual/config_file/config_variables/#modifiers>
-# for documentation.
-#
-# We escape user-provided input and use double quote as a separator.
-password_key = passdb/%Ew"%Eu
-user_key = userdb/%Eu
diff --git a/cmdeploy/src/cmdeploy/dovecot/auth.lua.j2 b/cmdeploy/src/cmdeploy/dovecot/auth.lua.j2
new file mode 100644
index 00000000..753c63cb
--- /dev/null
+++ b/cmdeploy/src/cmdeploy/dovecot/auth.lua.j2
@@ -0,0 +1,64 @@
+-- Existing addresses are served from the maildir directly.
+-- Unknown ones are offered to doveauth, which owns the creation policy.
+local mailboxes_dir = "{{ config.mailboxes_dir }}"
+local domain_suffix = "@{{ config.mail_domain }}"
+local create_url = "http://127.0.0.1:{{ config.doveauth_http_port }}/create"
+
+local http_client
+
+local function is_ours(user)
+  return user:sub(-#domain_suffix) == domain_suffix
+     and not user:find("/", 1, true)
+end
+
+local function password_hash(user)
+  local fh = io.open(mailboxes_dir .. "/" .. user .. "/password", "r")
+  if not fh then
+    return nil
+  end
+  local hash, rest = fh:read("l", "a")
+  fh:close()
+  if hash == nil or hash == "" or rest ~= "" then
+    return nil
+  end
+  return hash
+end
+
+local function userdb_fields(user)
+  return {home = mailboxes_dir .. "/" .. user, uid = "vmail", gid = "vmail"}
+end
+
+local function create(user, password)
+  local request = http_client:request({url = create_url, method = "POST"})
+  request:set_payload(user .. "\t" .. password)
+  return request:submit():status() == 200
+end
+
+-- Entry points called by dovecot
+
+function script_init()
+  http_client = dovecot.http.client({request_timeout_msecs = 5000, max_attempts = 1})
+  return 0
+end
+
+function auth_userdb_lookup(req)
+  if not is_ours(req.user) or password_hash(req.user) == nil then
+    return dovecot.auth.USERDB_RESULT_USER_UNKNOWN, {}
+  end
+  return dovecot.auth.USERDB_RESULT_OK, userdb_fields(req.user)
+end
+
+function auth_password_verify(req, password)
+  if not is_ours(req.user) then
+    return dovecot.auth.PASSDB_RESULT_USER_UNKNOWN, {}
+  end
+  local hash = password_hash(req.user)
+  if hash == nil then
+    if not create(req.user, password) then
+      return dovecot.auth.PASSDB_RESULT_USER_UNKNOWN, {}
+    end
+  elseif req:password_verify(hash, password) ~= 1 then
+    return dovecot.auth.PASSDB_RESULT_PASSWORD_MISMATCH, {}
+  end
+  return dovecot.auth.PASSDB_RESULT_OK, userdb_fields(req.user)
+end
diff --git a/cmdeploy/src/cmdeploy/dovecot/deployer.py b/cmdeploy/src/cmdeploy/dovecot/deployer.py
index 98588439..a4e0d5a7 100644
--- a/cmdeploy/src/cmdeploy/dovecot/deployer.py
+++ b/cmdeploy/src/cmdeploy/dovecot/deployer.py
@@ -31,7 +31,7 @@ class DovecotDeployer(Deployer):
         arch = host.get_fact(Arch)
         with blocked_service_startup():
             debs = []
-            for pkg in ("core", "imapd", "lmtpd"):
+            for pkg in ("core", "imapd", "lmtpd", "auth-lua"):
                 deb, changed = _download_dovecot_package(pkg, arch)
                 self.need_restart |= changed
                 if deb:
@@ -134,7 +134,8 @@ def _configure_dovecot(deployer, config: Config, debug: bool = False):
         debug=debug,
         disable_ipv6=config.disable_ipv6,
     )
-    deployer.put_file("dovecot/auth.conf", "/etc/dovecot/auth.conf")
+    deployer.put_template("dovecot/auth.lua.j2", "/etc/dovecot/auth.lua", config=config)
+    deployer.remove_file("/etc/dovecot/auth.conf")
     deployer.put_file(
         "dovecot/push_notification.lua", "/etc/dovecot/push_notification.lua"
     )
diff --git a/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2 b/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2
index c9977683..19b08a64 100644
--- a/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2
+++ b/cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2
@@ -61,12 +61,12 @@ imap_capability = +XDELTAPUSH XCHATMAIL
 
 # Authentication for system users.
 passdb {
-  driver = dict
-  args = /etc/dovecot/auth.conf
+  driver = lua
+  args = file=/etc/dovecot/auth.lua blocking=yes
 }
 userdb {
-  driver = dict
-  args = /etc/dovecot/auth.conf
+  driver = lua
+  args = file=/etc/dovecot/auth.lua blocking=yes
 }
 ##
 ## Mailbox locations and namespaces
diff --git a/cmdeploy/src/cmdeploy/pins.py b/cmdeploy/src/cmdeploy/pins.py
index a555ae38..20ae826e 100644
--- a/cmdeploy/src/cmdeploy/pins.py
+++ b/cmdeploy/src/cmdeploy/pins.py
@@ -36,6 +36,8 @@ DOVECOT_SHA256 = {
     ("imapd", "arm64"): "178fa877ddd5df9930e8308b518f4b07df10e759050725f8217a0c1fb3fd707f",
     ("lmtpd", "amd64"): "2f69ba5e35363de50962d42cccbfe4ed8495265044e244007d7ccddad77513ab",
     ("lmtpd", "arm64"): "89f52fb36524f5877a177dff4a713ba771fd3f91f22ed0af7238d495e143b38f",
+    ("auth-lua", "amd64"): "d724f37712faba52e177153114af1831e54da555c57c6474c05f96f176176ce4",
+    ("auth-lua", "arm64"): "7272768e20de148c35891d99cd60205acbe7e732b056caf0a83e8194d49136e6",
 }
 TURN_VERSION = "v0.4"
 TURN_ARTIFACTS = {
diff --git a/cmdeploy/src/cmdeploy/service/doveauth.service.f b/cmdeploy/src/cmdeploy/service/doveauth.service.f
index 9d858960..68574167 100644
--- a/cmdeploy/src/cmdeploy/service/doveauth.service.f
+++ b/cmdeploy/src/cmdeploy/service/doveauth.service.f
@@ -1,12 +1,11 @@
 [Unit]
-Description=Chatmail dict authentication proxy for dovecot
+Description=Chatmail HTTP authentication service for dovecot
 
 [Service]
-ExecStart={execpath} /run/doveauth/doveauth.socket {config_path}
+ExecStart={execpath} {config_path}
 Restart=always
-RestartSec=30
+RestartSec=5
 User=vmail
-RuntimeDirectory=doveauth
 UMask=0077
 
 [Install]
diff --git a/cmdeploy/src/cmdeploy/tests/test_authlua.py b/cmdeploy/src/cmdeploy/tests/test_authlua.py
new file mode 100644
index 00000000..e79972e6
--- /dev/null
+++ b/cmdeploy/src/cmdeploy/tests/test_authlua.py
@@ -0,0 +1,206 @@
+"""Test auth.lua script against mocked dovecot auth API."""
+
+import jinja2
+import pytest
+from chatmaild.doveauth import encrypt_password, verify_password
+
+from cmdeploy.basedeploy import get_resource
+
+USER1 = "user12345@chat.example.org"
+USER2 = "newuser12@chat.example.org"
+OK, UNKNOWN, MISMATCH = 1, -2, -3
+
+DOVECOT_MOCKS = """
+create_status = 200
+
+dovecot = {
+  auth = {
+    PASSDB_RESULT_OK = OK,
+    PASSDB_RESULT_USER_UNKNOWN = UNKNOWN,
+    PASSDB_RESULT_PASSWORD_MISMATCH = MISMATCH,
+    USERDB_RESULT_OK = OK,
+    USERDB_RESULT_USER_UNKNOWN = UNKNOWN,
+  },
+  http = {
+    client = function(options)
+      client_options = options
+      return {request = function(_, options)
+        create_request = options
+        return {
+          set_payload = function(_, payload) create_payload = payload end,
+          submit = function()
+            return {status = function() return create_status end}
+          end,
+        }
+      end}
+    end,
+  },
+}
+"""
+
+
+def load_authlua(lua, config):
+    lua.g.OK, lua.g.UNKNOWN, lua.g.MISMATCH = OK, UNKNOWN, MISMATCH
+    lua.rt.execute(DOVECOT_MOCKS)
+    template = jinja2.Template(get_resource("dovecot/auth.lua.j2").read_text())
+    lua.rt.execute(template.render(config=config))
+    assert lua.g.script_init() == 0
+    return lua
+
+
+@pytest.fixture
+def authlua(lua, example_config):
+    return load_authlua(lua, example_config)
+
+
+@pytest.fixture
+def request_for(lua):
+    def request_for(addr):
+        def password_verify(_self, hashed, plain):
+            return 1 if verify_password(hashed, plain) else 0
+
+        return lua.table(user=addr, password_verify=password_verify)
+
+    return request_for
+
+
+@pytest.fixture
+def create_user(example_config):
+    def create_user(addr, password):
+        example_config.get_user(addr).set_password(encrypt_password(password))
+
+    return create_user
+
+
+@pytest.fixture
+def write_password_file(example_config):
+    def write_password_file(addr, content):
+        maildir = example_config.mailboxes_dir / addr
+        maildir.mkdir(parents=True, exist_ok=True)
+        maildir.joinpath("password").write_text(content)
+
+    return write_password_file
+
+
+def test_http_client_uses_dovecot_setting_names(authlua):
+    """dovecot's lua http binding silently ignores keys it does not know."""
+    assert dict(authlua.g.client_options) == {
+        "request_timeout_msecs": 5000,
+        "max_attempts": 1,
+    }
+
+
+def test_existing_address_correct_password(authlua, request_for, create_user):
+    create_user(USER1, "correctgoose")
+    res, fields = authlua.g.auth_password_verify(request_for(USER1), "correctgoose")
+    assert res == OK
+    assert fields["uid"] == fields["gid"] == "vmail"
+    assert fields["home"].endswith(USER1)
+    assert authlua.g.create_payload is None
+
+
+def test_existing_address_wrong_password(authlua, request_for, create_user):
+    create_user(USER1, "correctgoose")
+    res, _ = authlua.g.auth_password_verify(request_for(USER1), "wronghorse")
+    assert res == MISMATCH
+
+
+def test_foreign_domain_is_refused_without_calling_out(
+    authlua, request_for, create_user
+):
+    create_user("user12345@evil.example.org", "correctgoose")
+    request = request_for("user12345@evil.example.org")
+    res, _ = authlua.g.auth_password_verify(request, "correctgoose")
+    assert res == UNKNOWN
+    assert authlua.g.auth_userdb_lookup(request)[0] == UNKNOWN
+    assert authlua.g.create_payload is None
+
+
+def test_name_shorter_than_the_domain_is_refused(authlua, request_for):
+    for name in ("x", "", "chat.example.org"):
+        res, _ = authlua.g.auth_password_verify(request_for(name), "correctgoose")
+        assert res == UNKNOWN
+        assert authlua.g.auth_userdb_lookup(request_for(name))[0] == UNKNOWN
+    assert authlua.g.create_payload is None
+
+
+def test_slash_in_username_is_refused(authlua, request_for):
+    request = request_for("../../etc/shadow@chat.example.org")
+    res, _ = authlua.g.auth_password_verify(request, "somepassword")
+    assert res == UNKNOWN
+    assert authlua.g.auth_userdb_lookup(request)[0] == UNKNOWN
+    assert authlua.g.create_payload is None
+
+
+def test_localpart_policy_is_left_to_doveauth(authlua, request_for):
+    authlua.g.create_status = 403
+    res, _ = authlua.g.auth_password_verify(request_for("@chat.example.org"), "somepw")
+    assert res == UNKNOWN
+    assert authlua.g.create_payload == "@chat.example.org\tsomepw"
+
+
+def test_unknown_address_is_created_via_endpoint(authlua, request_for):
+    res, fields = authlua.g.auth_password_verify(request_for(USER2), "brandnewpass")
+    assert res == OK
+    assert fields["home"].endswith(USER2)
+    assert authlua.g.create_payload == f"{USER2}\tbrandnewpass"
+    assert authlua.g.create_request["url"] == "http://127.0.0.1:10084/create"
+
+
+# a policy refusal and a doveauth that is down are both fail-closed
+@pytest.mark.parametrize("status", [403, 0])
+def test_creation_that_is_not_answered_with_200_is_user_unknown(
+    authlua, request_for, status
+):
+    authlua.g.create_status = status
+    res, _ = authlua.g.auth_password_verify(request_for(USER2), "brandnewpass")
+    assert res == UNKNOWN
+
+
+def test_userdb_unknown_before_creation_ok_after(authlua, request_for, create_user):
+    request = request_for(USER1)
+    res, _ = authlua.g.auth_userdb_lookup(request)
+    assert res == UNKNOWN
+    # a userdb lookup must never create anything
+    assert authlua.g.create_payload is None
+
+    create_user(USER1, "correctgoose")
+    res, fields = authlua.g.auth_userdb_lookup(request)
+    assert res == OK
+    assert fields["home"].endswith(USER1)
+    assert fields["uid"] == fields["gid"] == "vmail"
+
+
+def test_empty_password_file_is_unknown(authlua, request_for, write_password_file):
+    write_password_file(USER1, "")
+    assert authlua.g.auth_userdb_lookup(request_for(USER1))[0] == UNKNOWN
+
+    write_password_file(USER1, "\n")
+    assert authlua.g.auth_userdb_lookup(request_for(USER1))[0] == UNKNOWN
+
+
+def test_password_file_format_checks(authlua, request_for, write_password_file):
+    write_password_file(USER1, encrypt_password("correctgoose") + "\n")
+    res, _ = authlua.g.auth_password_verify(request_for(USER1), "correctgoose")
+    assert res == OK
+    assert authlua.g.auth_userdb_lookup(request_for(USER1))[0] == OK
+
+    passhash = encrypt_password("correctgoose")
+    write_password_file(USER1, passhash + "\ntrailing junk")
+    authlua.g.create_status = 403
+    res, _ = authlua.g.auth_password_verify(request_for(USER1), "correctgoose")
+    assert res == UNKNOWN
+    assert authlua.g.auth_userdb_lookup(request_for(USER1))[0] == UNKNOWN
+
+
+def test_ipv4_relay_uses_bracketed_domain(lua, ipv4_config, request_for):
+    # mail_domain is "[1.3.3.7]" here, and is_ours must not read it as a pattern
+    authlua = load_authlua(lua, ipv4_config)
+    addr = f"user12345@{ipv4_config.mail_domain}"
+    ipv4_config.get_user(addr).set_password(encrypt_password("correctgoose"))
+
+    res, fields = authlua.g.auth_password_verify(request_for(addr), "correctgoose")
+    assert res == OK
+    assert fields["home"].endswith(addr)
+    assert authlua.g.auth_userdb_lookup(request_for(addr))[0] == OK
+    assert authlua.g.auth_userdb_lookup(request_for(USER1))[0] == UNKNOWN
diff --git a/cmdeploy/src/cmdeploy/tests/test_dovecot_deployer.py b/cmdeploy/src/cmdeploy/tests/test_dovecot_deployer.py
index 0eabbd5d..4d064c0d 100644
--- a/cmdeploy/src/cmdeploy/tests/test_dovecot_deployer.py
+++ b/cmdeploy/src/cmdeploy/tests/test_dovecot_deployer.py
@@ -136,6 +136,7 @@ def test_install_skips_dpkg_path_when_epoch_matched_packages_present(
                     "dovecot-core": [dovecot_deployer.DOVECOT_PACKAGE_VERSION],
                     "dovecot-imapd": [dovecot_deployer.DOVECOT_PACKAGE_VERSION],
                     "dovecot-lmtpd": [dovecot_deployer.DOVECOT_PACKAGE_VERSION],
+                    "dovecot-auth-lua": [dovecot_deployer.DOVECOT_PACKAGE_VERSION],
                 },
             ),
             (dovecot_deployer.Arch, "x86_64"),
@@ -180,9 +181,12 @@ def test_install_unsupported_arch_falls_back_to_apt(
     deployer.install()
 
     actual_pkgs = [c["packages"] for c in apt_calls]
-    assert actual_pkgs == [["dovecot-core"], ["dovecot-imapd"], ["dovecot-lmtpd"]], (
-        f"expected apt install of core/imapd/lmtpd, got {actual_pkgs}"
-    )
+    assert actual_pkgs == [
+        ["dovecot-core"],
+        ["dovecot-imapd"],
+        ["dovecot-lmtpd"],
+        ["dovecot-auth-lua"],
+    ], f"expected apt install of core/imapd/lmtpd/auth-lua, got {actual_pkgs}"
     assert track_shell == [], "should not run dpkg for unsupported arch"
     assert deployer.need_restart is True, (
         "need_restart should be True when apt installed a package"
diff --git a/doc/source/overview.rst b/doc/source/overview.rst
index 6363a27a..264eb805 100644
--- a/doc/source/overview.rst
+++ b/doc/source/overview.rst
@@ -84,11 +84,12 @@ and only relaying OpenPGP end-to-end messages encrypted messages. A
 short overview of ``chatmaild`` services:
 
 -  :repofile:`doveauth <chatmaild/src/chatmaild/doveauth.py>`
-   implements create-on-login address semantics and is used by Dovecot
-   during IMAP login and by Postfix during SMTP/SUBMISSION login which
-   in turn uses `Dovecot SASL
-   <https://doc.dovecot.org/2.3/configuration_manual/authentication/dict/#complete-example-for-authenticating-via-a-unix-socket>`_
-   to authenticate logins.
+   implements create-on-login address semantics.
+   Dovecot authenticates IMAP logins, and Postfix SMTP/SUBMISSION logins through `Dovecot SASL
+   <https://doc.dovecot.org/2.3/configuration_manual/authentication/authentication_mechanisms/>`_,
+   from an :repofile:`auth.lua <cmdeploy/src/cmdeploy/dovecot/auth.lua.j2>` script
+   that reads the maildir directly. Only addresses which do not exist yet
+   are passed on to doveauth, which owns the creation policy.
 
 -  :repofile:`chatmail-metadata <chatmaild/src/chatmaild/metadata.py>`
    is contacted by a
@@ -155,7 +156,7 @@ Chatmail relay dependency diagram
         filtermail-outgoing --- |10025 reinject|postfix;
         filtermail-incoming --- |10026 reinject|postfix;
         postfix --- |milter opendkim.sock|OpenDKIM
-        dovecot --- |doveauth.socket|doveauth;
+        dovecot --- |10084 create|doveauth;
         dovecot --- |message delivery|maildir["maildir
         /home/vmail/.../user"];
         dovecot --- |lastlogin.socket|lastlogin;