# -*- 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 log, failure

_MIN_PORT = 1
_MAX_PORT = 2 ** 16 - 1

class IdentError(Exception):
"""
Can't determine connection owner; reason unknown.
"""

identDescription = 'UNKNOWN-ERROR'

def __str__(self):
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, (sysName, userId), sport, cport):
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 L{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
def getUsername(self, uid, getpwuid=getpwuid):
return getpwuid(uid)[0]
del getpwuid
except ImportError:
def getUsername(self, uid):
raise IdentError()

def entries(self):
f = file('/proc/net/tcp')
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("Unexpected server response: %r" % (line,))
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']