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# -*- test-case-name: twisted.test.test_ident -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Ident protocol implementation.
"""
import struct
from twisted.internet import defer
from twisted.protocols import basic
from twisted.python import failure, log
_MIN_PORT = 1
_MAX_PORT = 2**16 - 1
class IdentError(Exception):
"""
Can't determine connection owner; reason unknown.
"""
identDescription = "UNKNOWN-ERROR"
def __str__(self) -> str:
return self.identDescription
class NoUser(IdentError):
"""
The connection specified by the port pair is not currently in use or
currently not owned by an identifiable entity.
"""
identDescription = "NO-USER"
class InvalidPort(IdentError):
"""
Either the local or foreign port was improperly specified. This should
be returned if either or both of the port ids were out of range (TCP
port numbers are from 1-65535), negative integers, reals or in any
fashion not recognized as a non-negative integer.
"""
identDescription = "INVALID-PORT"
class HiddenUser(IdentError):
"""
The server was able to identify the user of this port, but the
information was not returned at the request of the user.
"""
identDescription = "HIDDEN-USER"
class IdentServer(basic.LineOnlyReceiver):
"""
The Identification Protocol (a.k.a., "ident", a.k.a., "the Ident
Protocol") provides a means to determine the identity of a user of a
particular TCP connection. Given a TCP port number pair, it returns a
character string which identifies the owner of that connection on the
server's system.
Server authors should subclass this class and override the lookup method.
The default implementation returns an UNKNOWN-ERROR response for every
query.
"""
def lineReceived(self, line):
parts = line.split(",")
if len(parts) != 2:
self.invalidQuery()
else:
try:
portOnServer, portOnClient = map(int, parts)
except ValueError:
self.invalidQuery()
else:
if (
_MIN_PORT <= portOnServer <= _MAX_PORT
and _MIN_PORT <= portOnClient <= _MAX_PORT
):
self.validQuery(portOnServer, portOnClient)
else:
self._ebLookup(
failure.Failure(InvalidPort()), portOnServer, portOnClient
)
def invalidQuery(self):
self.transport.loseConnection()
def validQuery(self, portOnServer, portOnClient):
"""
Called when a valid query is received to look up and deliver the
response.
@param portOnServer: The server port from the query.
@param portOnClient: The client port from the query.
"""
serverAddr = self.transport.getHost().host, portOnServer
clientAddr = self.transport.getPeer().host, portOnClient
defer.maybeDeferred(self.lookup, serverAddr, clientAddr).addCallback(
self._cbLookup, portOnServer, portOnClient
).addErrback(self._ebLookup, portOnServer, portOnClient)
def _cbLookup(self, result, sport, cport):
(sysName, userId) = result
self.sendLine("%d, %d : USERID : %s : %s" % (sport, cport, sysName, userId))
def _ebLookup(self, failure, sport, cport):
if failure.check(IdentError):
self.sendLine("%d, %d : ERROR : %s" % (sport, cport, failure.value))
else:
log.err(failure)
self.sendLine(
"%d, %d : ERROR : %s" % (sport, cport, IdentError(failure.value))
)
def lookup(self, serverAddress, clientAddress):
"""
Lookup user information about the specified address pair.
Return value should be a two-tuple of system name and username.
Acceptable values for the system name may be found online at::
U{http://www.iana.org/assignments/operating-system-names}
This method may also raise any IdentError subclass (or IdentError
itself) to indicate user information will not be provided for the
given query.
A Deferred may also be returned.
@param serverAddress: A two-tuple representing the server endpoint
of the address being queried. The first element is a string holding
a dotted-quad IP address. The second element is an integer
representing the port.
@param clientAddress: Like I{serverAddress}, but represents the
client endpoint of the address being queried.
"""
raise IdentError()
class ProcServerMixin:
"""Implements lookup() to grab entries for responses from /proc/net/tcp"""
SYSTEM_NAME = "LINUX"
try:
from pwd import getpwuid # type:ignore[misc]
def getUsername(self, uid, getpwuid=getpwuid):
return getpwuid(uid)[0]
del getpwuid
except ImportError:
def getUsername(self, uid, getpwuid=None):
raise IdentError()
def entries(self):
with open("/proc/net/tcp") as f:
f.readline()
for L in f:
yield L.strip()
def dottedQuadFromHexString(self, hexstr):
return ".".join(
map(str, struct.unpack("4B", struct.pack("=L", int(hexstr, 16))))
)
def unpackAddress(self, packed):
addr, port = packed.split(":")
addr = self.dottedQuadFromHexString(addr)
port = int(port, 16)
return addr, port
def parseLine(self, line):
parts = line.strip().split()
localAddr, localPort = self.unpackAddress(parts[1])
remoteAddr, remotePort = self.unpackAddress(parts[2])
uid = int(parts[7])
return (localAddr, localPort), (remoteAddr, remotePort), uid
def lookup(self, serverAddress, clientAddress):
for ent in self.entries():
localAddr, remoteAddr, uid = self.parseLine(ent)
if remoteAddr == clientAddress and localAddr[1] == serverAddress[1]:
return (self.SYSTEM_NAME, self.getUsername(uid))
raise NoUser()
class IdentClient(basic.LineOnlyReceiver):
errorTypes = (IdentError, NoUser, InvalidPort, HiddenUser)
def __init__(self):
self.queries = []
def lookup(self, portOnServer, portOnClient):
"""
Lookup user information about the specified address pair.
"""
self.queries.append((defer.Deferred(), portOnServer, portOnClient))
if len(self.queries) > 1:
return self.queries[-1][0]
self.sendLine("%d, %d" % (portOnServer, portOnClient))
return self.queries[-1][0]
def lineReceived(self, line):
if not self.queries:
log.msg(f"Unexpected server response: {line!r}")
else:
d, _, _ = self.queries.pop(0)
self.parseResponse(d, line)
if self.queries:
self.sendLine("%d, %d" % (self.queries[0][1], self.queries[0][2]))
def connectionLost(self, reason):
for q in self.queries:
q[0].errback(IdentError(reason))
self.queries = []
def parseResponse(self, deferred, line):
parts = line.split(":", 2)
if len(parts) != 3:
deferred.errback(IdentError(line))
else:
ports, type, addInfo = map(str.strip, parts)
if type == "ERROR":
for et in self.errorTypes:
if et.identDescription == addInfo:
deferred.errback(et(line))
return
deferred.errback(IdentError(line))
else:
deferred.callback((type, addInfo))
__all__ = [
"IdentError",
"NoUser",
"InvalidPort",
"HiddenUser",
"IdentServer",
"IdentClient",
"ProcServerMixin",
]