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DECNET/decnet/templates/pop3/server.py
anti 2979997442 feat(templates): IMAP/POP3 servers read EML spool from emailgen 
When IMAP_EMAIL_SEED / POP3_EMAIL_SEED points at a directory of .eml
files (the orchestrator emailgen worker's drop path,
/var/spool/decnet-emails/ by convention), the bait mailbox is replaced
with those LLM-generated, persona-driven, threaded messages.  Empty /
missing dir keeps the hardcoded fallback so a fresh deployment is never
silent.  Cached with mtime invalidation + a short TTL so a hot mailbox
doesn't pay the parse cost on every IMAP/POP3 command.

Replaces the DEBT-026 stub on both templates that named the env var but
never wired it through.
2026-04-26 22:21:01 -04:00

489 lines
19 KiB
Python
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#!/usr/bin/env python3
"""
POP3 server (port 110).
Full POP3 state machine with bait mailbox.
States: AUTHORIZATION → TRANSACTION
Credentials via IMAP_USERS env var (shared with IMAP service).
10 bait emails containing AWS keys, DB passwords, tokens etc.
"""
import asyncio
import os
import time
from pathlib import Path
from syslog_bridge import (
SEVERITY_WARNING,
encode_secret,
forward_syslog,
syslog_line,
write_syslog_file,
)
NODE_NAME = os.environ.get("NODE_NAME", "mailserver")
SERVICE_NAME = "pop3"
LOG_TARGET = os.environ.get("LOG_TARGET", "")
PORT = int(os.environ.get("PORT", "110"))
POP3_BANNER = os.environ.get("POP3_BANNER", f"+OK {NODE_NAME} Dovecot POP3 ready.")
_RAW_USERS = os.environ.get("IMAP_USERS", "admin:admin123,root:toor,mail:mail,user:user")
VALID_USERS: dict[str, str] = {
u: p for part in _RAW_USERS.split(",") if ":" in part for u, p in [part.split(":", 1)]
}
# Path to a directory of ``*.eml`` files dropped by the orchestrator
# emailgen worker (``/var/spool/decnet-emails/`` by convention). When
# set and populated, those EMLs replace the hardcoded fallback list
# below — same semantics as the IMAP template. Empty / missing falls
# back so a fresh deployment is never silent.
_EMAIL_SEED_PATH = os.environ.get("POP3_EMAIL_SEED", "")
_SEED_RESCAN_INTERVAL = float(os.environ.get("POP3_EMAIL_SEED_RESCAN", "5"))
# ── Bait emails ───────────────────────────────────────────────────────────────
_BAIT_EMAILS: list[str] = [
(
"Date: Mon, 06 Nov 2023 09:12:33 +0000\r\n"
"From: DevOps Team <devops@company.internal>\r\n"
"To: admin@company.internal\r\n"
"Subject: AWS credentials rotation\r\n"
"Message-ID: <1@company.internal>\r\n"
"\r\n"
"Team,\r\n\r\n"
"New AWS credentials have been issued. Old keys deactivated.\r\n\r\n"
"Access Key ID: AKIAIOSFODNN7EXAMPLE\r\n"
"Secret Access Key: wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY\r\n\r\n"
"Update ~/.aws/credentials immediately.\r\n\r\n-- DevOps\r\n"
),
(
"Date: Tue, 07 Nov 2023 14:05:11 +0000\r\n"
"From: Monitoring <monitoring@company.internal>\r\n"
"To: admin@company.internal\r\n"
"Subject: DB password changed\r\n"
"Message-ID: <2@company.internal>\r\n"
"\r\n"
"Production database password was rotated.\r\n\r\n"
"Connection string: mysql://admin:Sup3rS3cr3t!@10.0.1.5:3306/production\r\n\r\n"
"Update all app configs.\r\n"
),
(
"Date: Wed, 08 Nov 2023 08:30:00 +0000\r\n"
"From: GitHub <noreply@github.com>\r\n"
"To: admin@company.internal\r\n"
"Subject: Your personal access token\r\n"
"Message-ID: <3@company.internal>\r\n"
"\r\n"
"Hi admin,\r\n\r\n"
"A new personal access token was created for your account.\r\n\r\n"
"Token: ghp_16C7e42F292c6912E7710c838347Ae178B4a\r\n\r\n"
"If this wasn't you, revoke it immediately at github.com/settings/tokens.\r\n"
),
(
"Date: Thu, 09 Nov 2023 11:22:47 +0000\r\n"
"From: IT Admin <admin@company.internal>\r\n"
"To: team@company.internal\r\n"
"Subject: VPN config attached\r\n"
"Message-ID: <4@company.internal>\r\n"
"\r\n"
"VPN access details for new starters:\r\n\r\n"
" Host: vpn.company.internal:1194\r\n"
" Protocol: UDP\r\n"
" Username: vpnadmin\r\n"
" Password: VpnP@ss2024\r\n\r\n"
"Config file sent separately via secure channel.\r\n"
),
(
"Date: Fri, 10 Nov 2023 16:45:00 +0000\r\n"
"From: SysAdmin <sysadmin@company.internal>\r\n"
"To: admin@company.internal\r\n"
"Subject: Root password\r\n"
"Message-ID: <5@company.internal>\r\n"
"\r\n"
"New root password for prod servers:\r\n\r\n"
" r00tM3T00!\r\n\r\n"
"Change after first login. Do NOT forward this email.\r\n"
),
(
"Date: Sat, 11 Nov 2023 03:12:04 +0000\r\n"
"From: Backup System <backup@company.internal>\r\n"
"To: admin@company.internal\r\n"
"Subject: Backup job failed\r\n"
"Message-ID: <6@company.internal>\r\n"
"\r\n"
"Nightly backup to 192.168.1.50:/mnt/nas FAILED at 03:11 UTC.\r\n\r\n"
"Error: Authentication failed. Credentials in /etc/backup.conf may be stale.\r\n\r\n"
"Last successful backup: 2023-11-10 03:11 UTC\r\n"
),
(
"Date: Sun, 12 Nov 2023 07:04:31 +0000\r\n"
"From: Security Alerts <alerts@company.internal>\r\n"
"To: admin@company.internal\r\n"
"Subject: SSH brute-force alert\r\n"
"Message-ID: <7@company.internal>\r\n"
"\r\n"
"47 failed SSH login attempts detected against prod-web-01.\r\n\r\n"
"Source IPs: 185.220.101.34, 185.220.101.47, 185.220.101.52\r\n"
"Target user: root\r\n"
"Period: 2023-11-12 06:58 - 07:04 UTC\r\n\r\n"
"All attempts blocked by fail2ban. No successful logins.\r\n"
),
(
"Date: Mon, 13 Nov 2023 10:11:55 +0000\r\n"
"From: External Vendor <vendor@external.com>\r\n"
"To: admin@company.internal\r\n"
"Subject: RE: API integration\r\n"
"Message-ID: <8@company.internal>\r\n"
"\r\n"
"Hi,\r\n\r\n"
"Here is the live API key for the integration:\r\n\r\n"
" sk_live_9mK3xF2aP7qR1bN8cT4dW6vE0yU5hJ\r\n\r\n"
"Keep this confidential. Let me know if you need the webhook secret.\r\n\r\n"
"Best regards,\r\nVendor Support\r\n"
),
(
"Date: Tue, 14 Nov 2023 13:48:22 +0000\r\n"
"From: Help Desk <helpdesk@company.internal>\r\n"
"To: admin@company.internal\r\n"
"Subject: Password reset request\r\n"
"Message-ID: <9@company.internal>\r\n"
"\r\n"
"Hi,\r\n\r\n"
"Could you reset my MFA? Current password is Winter2024! so you can verify it's me.\r\n\r\n"
"Thanks\r\n"
),
(
"Date: Wed, 15 Nov 2023 00:01:00 +0000\r\n"
"From: AWS Billing <noreply@aws.amazon.com>\r\n"
"To: admin@company.internal\r\n"
"Subject: Your AWS bill is ready\r\n"
"Message-ID: <10@company.internal>\r\n"
"\r\n"
"Your AWS bill for October 2023 is $847.23.\r\n\r\n"
"Top services:\r\n"
" EC2 (us-east-1): $412.10\r\n"
" RDS (us-east-1): $198.50\r\n"
" S3: $87.43\r\n"
" EC2 (eu-west-2): $149.20\r\n\r\n"
"Account ID: 123456789012\r\n"
),
]
# ── Spool-backed email loader ─────────────────────────────────────────────────
# POP3 stores each message as a single str (full RFC 822 text); when the
# emailgen spool is configured, we read every *.eml in it and serve the
# raw bytes as the corpus. Same caching strategy as the IMAP template.
_seed_cache: list[str] | None = None
_seed_cache_dir_mtime: float = 0.0
_seed_cache_loaded_at: float = 0.0
def _scan_seed_dir(path: Path) -> list[str]:
"""Walk *path* recursively and return each .eml's raw text content,
sorted by mtime so older threads get lower indices."""
eml_paths: list[Path] = []
try:
for p in path.rglob("*.eml"):
if p.is_file():
eml_paths.append(p)
except OSError:
return []
eml_paths.sort(key=lambda p: p.stat().st_mtime)
out: list[str] = []
for p in eml_paths:
try:
out.append(p.read_text(encoding="utf-8", errors="replace"))
except OSError:
continue
return out
def _get_emails() -> list[str]:
"""Return the active corpus. Same fallback rules as IMAP template."""
global _seed_cache, _seed_cache_dir_mtime, _seed_cache_loaded_at
if not _EMAIL_SEED_PATH:
return _BAIT_EMAILS
seed_dir = Path(_EMAIL_SEED_PATH)
try:
dir_stat = seed_dir.stat()
except OSError:
return _BAIT_EMAILS
now = time.monotonic()
fresh_enough = (
_seed_cache is not None
and (now - _seed_cache_loaded_at) < _SEED_RESCAN_INTERVAL
and dir_stat.st_mtime == _seed_cache_dir_mtime
)
if fresh_enough:
return _seed_cache or _BAIT_EMAILS
scanned = _scan_seed_dir(seed_dir)
if not scanned:
return _BAIT_EMAILS
_seed_cache = scanned
_seed_cache_dir_mtime = dir_stat.st_mtime
_seed_cache_loaded_at = now
return scanned
# ── Logging ───────────────────────────────────────────────────────────────────
def _log(event_type: str, severity: int = 6, **kwargs) -> None:
line = syslog_line(SERVICE_NAME, NODE_NAME, event_type, severity, **kwargs)
write_syslog_file(line)
forward_syslog(line, LOG_TARGET)
# ── Protocol ──────────────────────────────────────────────────────────────────
class POP3Protocol(asyncio.Protocol):
def __init__(self):
self._transport = None
self._peer = ("?", 0)
self._buf = b""
self._state = "AUTHORIZATION"
self._current_user: str | None = None
self._deleted: set[int] = set() # 0-based indices of DELE'd messages
def connection_made(self, transport):
self._transport = transport
self._peer = transport.get_extra_info("peername", ("?", 0))
_log("connect", src=self._peer[0], src_port=self._peer[1])
banner = POP3_BANNER if POP3_BANNER.endswith("\r\n") else POP3_BANNER + "\r\n"
if not banner.startswith("+OK"):
banner = "+OK " + banner
transport.write(banner.encode())
def data_received(self, data):
self._buf += data
while b"\n" in self._buf:
line, self._buf = self._buf.split(b"\n", 1)
self._handle_line(line.decode(errors="replace").strip())
def connection_lost(self, exc):
_log("disconnect", src=self._peer[0] if self._peer else "?")
# ── Command dispatch ──────────────────────────────────────────────────────
def _handle_line(self, line: str) -> None:
parts = line.split(None, 1)
if not parts:
return
cmd = parts[0].upper()
args = parts[1] if len(parts) > 1 else ""
_log("command", src=self._peer[0], cmd=cmd, state=self._state)
# Always available
if cmd == "CAPA":
self._transport.write(
b"+OK\r\nTOP\r\nUSER\r\nUIDL\r\nRESP-CODES\r\nAUTH-RESP-CODE\r\nSASL\r\n.\r\n"
)
elif cmd == "QUIT":
self._transport.write(b"+OK Logging out.\r\n")
self._transport.close()
# AUTHORIZATION state
elif cmd == "USER":
self._cmd_user(args)
elif cmd == "PASS":
self._cmd_pass(args)
# TRANSACTION state
elif cmd == "STAT":
self._cmd_stat()
elif cmd == "LIST":
self._cmd_list(args)
elif cmd == "RETR":
self._cmd_retr(args)
elif cmd == "TOP":
self._cmd_top(args)
elif cmd == "UIDL":
self._cmd_uidl(args)
elif cmd == "DELE":
self._cmd_dele(args)
elif cmd == "RSET":
self._cmd_rset()
elif cmd == "NOOP":
self._transport.write(b"+OK\r\n")
else:
self._transport.write(b"-ERR Command not recognized\r\n")
# ── Command implementations ───────────────────────────────────────────────
def _cmd_user(self, args: str) -> None:
if self._state != "AUTHORIZATION":
self._transport.write(b"-ERR Already authenticated\r\n")
return
self._current_user = args.strip()
self._transport.write(b"+OK User name accepted, password please\r\n")
def _cmd_pass(self, args: str) -> None:
if self._state != "AUTHORIZATION":
self._transport.write(b"-ERR Already authenticated\r\n")
return
if not self._current_user:
self._transport.write(b"-ERR USER required first\r\n")
return
username = self._current_user
password = args.strip()
_enc = encode_secret(password)
if VALID_USERS.get(username) == password:
self._state = "TRANSACTION"
_log("auth", src=self._peer[0], username=username, principal=username,
outcome="success", **_enc)
self._transport.write(b"+OK Logged in.\r\n")
else:
_log("auth", src=self._peer[0], username=username, principal=username,
outcome="failure", severity=SEVERITY_WARNING, **_enc)
self._current_user = None
self._transport.write(b"-ERR Authentication failed.\r\n")
def _require_transaction(self) -> bool:
if self._state != "TRANSACTION":
self._transport.write(b"-ERR Not authenticated\r\n")
return False
return True
def _active_messages(self) -> list[tuple[int, str]]:
"""Return [(1-based-num, body), ...] excluding DELE'd messages."""
return [
(i + 1, body)
for i, body in enumerate(_get_emails())
if i not in self._deleted
]
def _cmd_stat(self) -> None:
if not self._require_transaction():
return
msgs = self._active_messages()
total = sum(len(b.encode()) for _, b in msgs)
self._transport.write(f"+OK {len(msgs)} {total}\r\n".encode())
def _cmd_list(self, args: str) -> None:
if not self._require_transaction():
return
emails = _get_emails()
if args:
try:
n = int(args)
idx = n - 1
if idx in self._deleted or not (0 <= idx < len(emails)):
self._transport.write(b"-ERR No such message\r\n")
else:
size = len(emails[idx].encode())
self._transport.write(f"+OK {n} {size}\r\n".encode())
except ValueError:
self._transport.write(b"-ERR Invalid argument\r\n")
else:
msgs = self._active_messages()
total = sum(len(b.encode()) for _, b in msgs)
self._transport.write(f"+OK {len(msgs)} messages ({total} octets)\r\n".encode())
for n, body in msgs:
self._transport.write(f"{n} {len(body.encode())}\r\n".encode())
self._transport.write(b".\r\n")
def _cmd_retr(self, args: str) -> None:
if not self._require_transaction():
return
try:
n = int(args)
idx = n - 1
emails = _get_emails()
if idx in self._deleted or not (0 <= idx < len(emails)):
self._transport.write(b"-ERR No such message\r\n")
return
body = emails[idx]
raw = body.encode()
_log("retr", src=self._peer[0], message_num=n)
self._transport.write(f"+OK {len(raw)} octets\r\n".encode())
self._transport.write(raw)
if not raw.endswith(b"\r\n"):
self._transport.write(b"\r\n")
self._transport.write(b".\r\n")
except ValueError:
self._transport.write(b"-ERR Invalid argument\r\n")
def _cmd_top(self, args: str) -> None:
if not self._require_transaction():
return
try:
parts = args.split(None, 1)
n = int(parts[0])
line_count = int(parts[1]) if len(parts) > 1 else 0
idx = n - 1
emails = _get_emails()
if idx in self._deleted or not (0 <= idx < len(emails)):
self._transport.write(b"-ERR No such message\r\n")
return
body = emails[idx]
sep = "\r\n\r\n"
if sep in body:
headers, rest = body.split(sep, 1)
headers += sep
else:
headers, rest = body, ""
body_lines = rest.split("\r\n")[:line_count]
result = headers + "\r\n".join(body_lines)
self._transport.write(b"+OK\r\n")
self._transport.write(result.encode())
if not result.endswith("\r\n"):
self._transport.write(b"\r\n")
self._transport.write(b".\r\n")
except (ValueError, IndexError):
self._transport.write(b"-ERR Invalid arguments\r\n")
def _cmd_uidl(self, args: str) -> None:
if not self._require_transaction():
return
if args:
try:
n = int(args)
idx = n - 1
if idx in self._deleted or not (0 <= idx < len(_get_emails())):
self._transport.write(b"-ERR No such message\r\n")
else:
self._transport.write(f"+OK {n} msg-{n}\r\n".encode())
except ValueError:
self._transport.write(b"-ERR Invalid argument\r\n")
else:
self._transport.write(b"+OK\r\n")
for n, _ in self._active_messages():
self._transport.write(f"{n} msg-{n}\r\n".encode())
self._transport.write(b".\r\n")
def _cmd_dele(self, args: str) -> None:
if not self._require_transaction():
return
try:
n = int(args)
idx = n - 1
if idx in self._deleted or not (0 <= idx < len(_get_emails())):
self._transport.write(b"-ERR No such message\r\n")
else:
self._deleted.add(idx)
_log("delete", src=self._peer[0], message_num=n)
self._transport.write(f"+OK Message {n} deleted\r\n".encode())
except ValueError:
self._transport.write(b"-ERR Invalid argument\r\n")
def _cmd_rset(self) -> None:
if not self._require_transaction():
return
self._deleted.clear()
self._transport.write(b"+OK\r\n")
async def main():
_log("startup", msg=f"POP3 server starting as {NODE_NAME}")
loop = asyncio.get_running_loop()
server = await loop.create_server(POP3Protocol, "0.0.0.0", PORT) # nosec B104
async with server:
await server.serve_forever()
if __name__ == "__main__":
asyncio.run(main())
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