rename doveauth-dictproxy to doveauth

chatmaild/src/chatmaild/doveauth.py

@@ -0,0 +1,150 @@
+import logging
+import os
+import time
+import sys
+import json
+import crypt
+from socketserver import (
+    UnixStreamServer,
+    StreamRequestHandler,
+    ThreadingMixIn,
+)
+import pwd
+
+from .database import Database
+
+NOCREATE_FILE = "/etc/chatmail-nocreate"
+
+
+def encrypt_password(password: str):
+    # https://doc.dovecot.org/configuration_manual/authentication/password_schemes/
+    passhash = crypt.crypt(password, crypt.METHOD_SHA512)
+    return "{SHA512-CRYPT}" + passhash
+
+
+def is_allowed_to_create(user, cleartext_password) -> bool:
+    """Return True if user and password are admissable."""
+    if os.path.exists(NOCREATE_FILE):
+        logging.warning(f"blocked account creation because {NOCREATE_FILE!r} exists.")
+        return False
+
+    if len(cleartext_password) < 10:
+        logging.warning("Password needs to be at least 10 characters long")
+        return False
+
+    parts = user.split("@")
+    if len(parts) != 2:
+        logging.warning(f"user {user!r} is not a proper e-mail address")
+        return False
+    localpart, domain = parts
+
+    if domain == "nine.testrun.org":
+        # nine.testrun.org policy, username has to be exactly nine chars
+        if len(localpart) != 9:
+            logging.warning(f"localpart {localpart!r} has not exactly nine chars")
+            return False
+
+    return True
+
+
+def get_user_data(db, user):
+    with db.read_connection() as conn:
+        result = conn.get_user(user)
+    if result:
+        result["uid"] = "vmail"
+        result["gid"] = "vmail"
+    return result
+
+
+def lookup_userdb(db, user):
+    return get_user_data(db, user)
+
+
+def lookup_passdb(db, user, cleartext_password):
+    with db.write_transaction() as conn:
+        userdata = conn.get_user(user)
+        if userdata:
+            # Update last login time.
+            conn.execute(
+                "UPDATE users SET last_login=? WHERE addr=?", (int(time.time()), user)
+            )
+
+            userdata["uid"] = "vmail"
+            userdata["gid"] = "vmail"
+            return userdata
+        if not is_allowed_to_create(user, cleartext_password):
+            return
+
+        encrypted_password = encrypt_password(cleartext_password)
+        q = """INSERT INTO users (addr, password, last_login)
+               VALUES (?, ?, ?)"""
+        conn.execute(q, (user, encrypted_password, int(time.time())))
+        return dict(
+            home=f"/home/vmail/{user}",
+            uid="vmail",
+            gid="vmail",
+            password=encrypted_password,
+        )
+
+
+def handle_dovecot_request(msg, db, mail_domain):
+    short_command = msg[0]
+    if short_command == "L":  # LOOKUP
+        parts = msg[1:].split("\t")
+        keyname, user = parts[:2]
+        namespace, type, *args = keyname.split("/")
+        reply_command = "F"
+        res = ""
+        if namespace == "shared":
+            if type == "userdb":
+                if user.endswith(f"@{mail_domain}"):
+                    res = lookup_userdb(db, user)
+                if res:
+                    reply_command = "O"
+                else:
+                    reply_command = "N"
+            elif type == "passdb":
+                if user.endswith(f"@{mail_domain}"):
+                    res = lookup_passdb(db, 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"
+    return None
+
+
+class ThreadedUnixStreamServer(ThreadingMixIn, UnixStreamServer):
+    pass
+
+
+def main():
+    socket = sys.argv[1]
+    passwd_entry = pwd.getpwnam(sys.argv[2])
+    db = Database(sys.argv[3])
+    with open("/etc/mailname", "r") as fp:
+        mail_domain = fp.read().strip()
+
+    class Handler(StreamRequestHandler):
+        def handle(self):
+            while True:
+                msg = self.rfile.readline().strip().decode()
+                if not msg:
+                    break
+                res = handle_dovecot_request(msg, db, mail_domain)
+                if res:
+                    self.wfile.write(res.encode("ascii"))
+                    self.wfile.flush()
+
+    try:
+        os.unlink(socket)
+    except FileNotFoundError:
+        pass
+
+    with ThreadedUnixStreamServer(socket, Handler) as server:
+        os.chown(socket, uid=passwd_entry.pw_uid, gid=passwd_entry.pw_gid)
+        try:
+            server.serve_forever()
+        except KeyboardInterrupt:
+            pass