Viewing file:  TLSRecordLayer.py (42.99 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
"""Helper class for TLSConnection."""
from __future__ import generators
from utils.compat import *
from utils.cryptomath import *
from utils.cipherfactory import createAES, createRC4, createTripleDES
from utils.codec import *
from errors import *
from messages import *
from mathtls import *
from constants import *
from utils.cryptomath import getRandomBytes
from utils import hmac
from FileObject import FileObject
import sha
import md5
import socket
import errno
import traceback
class _ConnectionState:
def __init__(self):
self.macContext = None
self.encContext = None
self.seqnum = 0
def getSeqNumStr(self):
w = Writer(8)
w.add(self.seqnum, 8)
seqnumStr = bytesToString(w.bytes)
self.seqnum += 1
return seqnumStr
class TLSRecordLayer:
"""
This class handles data transmission for a TLS connection.
Its only subclass is L{tlslite.TLSConnection.TLSConnection}. We've
separated the code in this class from TLSConnection to make things
more readable.
@type sock: socket.socket
@ivar sock: The underlying socket object.
@type session: L{tlslite.Session.Session}
@ivar session: The session corresponding to this connection.
Due to TLS session resumption, multiple connections can correspond
to the same underlying session.
@type version: tuple
@ivar version: The TLS version being used for this connection.
(3,0) means SSL 3.0, and (3,1) means TLS 1.0.
@type closed: bool
@ivar closed: If this connection is closed.
@type resumed: bool
@ivar resumed: If this connection is based on a resumed session.
@type allegedSharedKeyUsername: str or None
@ivar allegedSharedKeyUsername: This is set to the shared-key
username asserted by the client, whether the handshake succeeded or
not. If the handshake fails, this can be inspected to
determine if a guessing attack is in progress against a particular
user account.
@type allegedSrpUsername: str or None
@ivar allegedSrpUsername: This is set to the SRP username
asserted by the client, whether the handshake succeeded or not.
If the handshake fails, this can be inspected to determine
if a guessing attack is in progress against a particular user
account.
@type closeSocket: bool
@ivar closeSocket: If the socket should be closed when the
connection is closed (writable).
If you set this to True, TLS Lite will assume the responsibility of
closing the socket when the TLS Connection is shutdown (either
through an error or through the user calling close()). The default
is False.
@type ignoreAbruptClose: bool
@ivar ignoreAbruptClose: If an abrupt close of the socket should
raise an error (writable).
If you set this to True, TLS Lite will not raise a
L{tlslite.errors.TLSAbruptCloseError} exception if the underlying
socket is unexpectedly closed. Such an unexpected closure could be
caused by an attacker. However, it also occurs with some incorrect
TLS implementations.
You should set this to True only if you're not worried about an
attacker truncating the connection, and only if necessary to avoid
spurious errors. The default is False.
@sort: __init__, read, readAsync, write, writeAsync, close, closeAsync,
getCipherImplementation, getCipherName
"""
def __init__(self, sock):
self.sock = sock
#My session object (Session instance; read-only)
self.session = None
#Am I a client or server?
self._client = None
#Buffers for processing messages
self._handshakeBuffer = []
self._readBuffer = ""
#Handshake digests
self._handshake_md5 = md5.md5()
self._handshake_sha = sha.sha()
#TLS Protocol Version
self.version = (0,0) #read-only
self._versionCheck = False #Once we choose a version, this is True
#Current and Pending connection states
self._writeState = _ConnectionState()
self._readState = _ConnectionState()
self._pendingWriteState = _ConnectionState()
self._pendingReadState = _ConnectionState()
#Is the connection open?
self.closed = True #read-only
self._refCount = 0 #Used to trigger closure
#Is this a resumed (or shared-key) session?
self.resumed = False #read-only
#What username did the client claim in his handshake?
self.allegedSharedKeyUsername = None
self.allegedSrpUsername = None
#On a call to close(), do we close the socket? (writeable)
self.closeSocket = False
#If the socket is abruptly closed, do we ignore it
#and pretend the connection was shut down properly? (writeable)
self.ignoreAbruptClose = False
#Fault we will induce, for testing purposes
self.fault = None
#*********************************************************
# Public Functions START
#*********************************************************
def read(self, max=None, min=1):
"""Read some data from the TLS connection.
This function will block until at least 'min' bytes are
available (or the connection is closed).
If an exception is raised, the connection will have been
automatically closed.
@type max: int
@param max: The maximum number of bytes to return.
@type min: int
@param min: The minimum number of bytes to return
@rtype: str
@return: A string of no more than 'max' bytes, and no fewer
than 'min' (unless the connection has been closed, in which
case fewer than 'min' bytes may be returned).
@raise socket.error: If a socket error occurs.
@raise tlslite.errors.TLSAbruptCloseError: If the socket is closed
without a preceding alert.
@raise tlslite.errors.TLSAlert: If a TLS alert is signalled.
"""
for result in self.readAsync(max, min):
pass
return result
def readAsync(self, max=None, min=1):
"""Start a read operation on the TLS connection.
This function returns a generator which behaves similarly to
read(). Successive invocations of the generator will return 0
if it is waiting to read from the socket, 1 if it is waiting
to write to the socket, or a string if the read operation has
completed.
@rtype: iterable
@return: A generator; see above for details.
"""
try:
while len(self._readBuffer)<min and not self.closed:
try:
for result in self._getMsg(ContentType.application_data):
if result in (0,1):
yield result
applicationData = result
self._readBuffer += bytesToString(applicationData.write())
except TLSRemoteAlert, alert:
if alert.description != AlertDescription.close_notify:
raise
except TLSAbruptCloseError:
if not self.ignoreAbruptClose:
raise
else:
self._shutdown(True)
if max == None:
max = len(self._readBuffer)
returnStr = self._readBuffer[:max]
self._readBuffer = self._readBuffer[max:]
yield returnStr
except:
self._shutdown(False)
raise
def write(self, s):
"""Write some data to the TLS connection.
This function will block until all the data has been sent.
If an exception is raised, the connection will have been
automatically closed.
@type s: str
@param s: The data to transmit to the other party.
@raise socket.error: If a socket error occurs.
"""
for result in self.writeAsync(s):
pass
def writeAsync(self, s):
"""Start a write operation on the TLS connection.
This function returns a generator which behaves similarly to
write(). Successive invocations of the generator will return
1 if it is waiting to write to the socket, or will raise
StopIteration if the write operation has completed.
@rtype: iterable
@return: A generator; see above for details.
"""
try:
if self.closed:
raise ValueError()
index = 0
blockSize = 16384
skipEmptyFrag = False
while 1:
startIndex = index * blockSize
endIndex = startIndex + blockSize
if startIndex >= len(s):
break
if endIndex > len(s):
endIndex = len(s)
block = stringToBytes(s[startIndex : endIndex])
applicationData = ApplicationData().create(block)
for result in self._sendMsg(applicationData, skipEmptyFrag):
yield result
skipEmptyFrag = True #only send an empy fragment on 1st message
index += 1
except:
self._shutdown(False)
raise
def close(self):
"""Close the TLS connection.
This function will block until it has exchanged close_notify
alerts with the other party. After doing so, it will shut down the
TLS connection. Further attempts to read through this connection
will return "". Further attempts to write through this connection
will raise ValueError.
If makefile() has been called on this connection, the connection
will be not be closed until the connection object and all file
objects have been closed.
Even if an exception is raised, the connection will have been
closed.
@raise socket.error: If a socket error occurs.
@raise tlslite.errors.TLSAbruptCloseError: If the socket is closed
without a preceding alert.
@raise tlslite.errors.TLSAlert: If a TLS alert is signalled.
"""
if not self.closed:
for result in self._decrefAsync():
pass
def closeAsync(self):
"""Start a close operation on the TLS connection.
This function returns a generator which behaves similarly to
close(). Successive invocations of the generator will return 0
if it is waiting to read from the socket, 1 if it is waiting
to write to the socket, or will raise StopIteration if the
close operation has completed.
@rtype: iterable
@return: A generator; see above for details.
"""
if not self.closed:
for result in self._decrefAsync():
yield result
def _decrefAsync(self):
self._refCount -= 1
if self._refCount == 0 and not self.closed:
try:
for result in self._sendMsg(Alert().create(\
AlertDescription.close_notify, AlertLevel.warning)):
yield result
alert = None
while not alert:
for result in self._getMsg((ContentType.alert, \
ContentType.application_data)):
if result in (0,1):
yield result
if result.contentType == ContentType.alert:
alert = result
if alert.description == AlertDescription.close_notify:
self._shutdown(True)
else:
raise TLSRemoteAlert(alert)
except (socket.error, TLSAbruptCloseError):
#If the other side closes the socket, that's okay
self._shutdown(True)
except:
self._shutdown(False)
raise
def getCipherName(self):
"""Get the name of the cipher used with this connection.
@rtype: str
@return: The name of the cipher used with this connection.
Either 'aes128', 'aes256', 'rc4', or '3des'.
"""
if not self._writeState.encContext:
return None
return self._writeState.encContext.name
def getCipherImplementation(self):
"""Get the name of the cipher implementation used with
this connection.
@rtype: str
@return: The name of the cipher implementation used with
this connection. Either 'python', 'cryptlib', 'openssl',
or 'pycrypto'.
"""
if not self._writeState.encContext:
return None
return self._writeState.encContext.implementation
#Emulate a socket, somewhat -
def send(self, s):
"""Send data to the TLS connection (socket emulation).
@raise socket.error: If a socket error occurs.
"""
self.write(s)
return len(s)
def sendall(self, s):
"""Send data to the TLS connection (socket emulation).
@raise socket.error: If a socket error occurs.
"""
self.write(s)
def recv(self, bufsize):
"""Get some data from the TLS connection (socket emulation).
@raise socket.error: If a socket error occurs.
@raise tlslite.errors.TLSAbruptCloseError: If the socket is closed
without a preceding alert.
@raise tlslite.errors.TLSAlert: If a TLS alert is signalled.
"""
return self.read(bufsize)
def makefile(self, mode='r', bufsize=-1):
"""Create a file object for the TLS connection (socket emulation).
@rtype: L{tlslite.FileObject.FileObject}
"""
self._refCount += 1
return FileObject(self, mode, bufsize)
def getsockname(self):
"""Return the socket's own address (socket emulation)."""
return self.sock.getsockname()
def getpeername(self):
"""Return the remote address to which the socket is connected
(socket emulation)."""
return self.sock.getpeername()
def settimeout(self, value):
"""Set a timeout on blocking socket operations (socket emulation)."""
return self.sock.settimeout(value)
def gettimeout(self):
"""Return the timeout associated with socket operations (socket
emulation)."""
return self.sock.gettimeout()
def setsockopt(self, level, optname, value):
"""Set the value of the given socket option (socket emulation)."""
return self.sock.setsockopt(level, optname, value)
#*********************************************************
# Public Functions END
#*********************************************************
def _shutdown(self, resumable):
self._writeState = _ConnectionState()
self._readState = _ConnectionState()
#Don't do this: self._readBuffer = ""
self.version = (0,0)
self._versionCheck = False
self.closed = True
if self.closeSocket:
self.sock.close()
#Even if resumable is False, we'll never toggle this on
if not resumable and self.session:
self.session.resumable = False
def _sendError(self, alertDescription, errorStr=None):
alert = Alert().create(alertDescription, AlertLevel.fatal)
for result in self._sendMsg(alert):
yield result
self._shutdown(False)
raise TLSLocalAlert(alert, errorStr)
def _sendMsgs(self, msgs):
skipEmptyFrag = False
for msg in msgs:
for result in self._sendMsg(msg, skipEmptyFrag):
yield result
skipEmptyFrag = True
def _sendMsg(self, msg, skipEmptyFrag=False):
bytes = msg.write()
contentType = msg.contentType
#Whenever we're connected and asked to send a message,
#we first send an empty Application Data message. This prevents
#an attacker from launching a chosen-plaintext attack based on
#knowing the next IV.
if not self.closed and not skipEmptyFrag and self.version == (3,1):
if self._writeState.encContext:
if self._writeState.encContext.isBlockCipher:
for result in self._sendMsg(ApplicationData(),
skipEmptyFrag=True):
yield result
#Update handshake hashes
if contentType == ContentType.handshake:
bytesStr = bytesToString(bytes)
self._handshake_md5.update(bytesStr)
self._handshake_sha.update(bytesStr)
#Calculate MAC
if self._writeState.macContext:
seqnumStr = self._writeState.getSeqNumStr()
bytesStr = bytesToString(bytes)
mac = self._writeState.macContext.copy()
mac.update(seqnumStr)
mac.update(chr(contentType))
if self.version == (3,0):
mac.update( chr( int(len(bytes)/256) ) )
mac.update( chr( int(len(bytes)%256) ) )
elif self.version in ((3,1), (3,2)):
mac.update(chr(self.version[0]))
mac.update(chr(self.version[1]))
mac.update( chr( int(len(bytes)/256) ) )
mac.update( chr( int(len(bytes)%256) ) )
else:
raise AssertionError()
mac.update(bytesStr)
macString = mac.digest()
macBytes = stringToBytes(macString)
if self.fault == Fault.badMAC:
macBytes[0] = (macBytes[0]+1) % 256
#Encrypt for Block or Stream Cipher
if self._writeState.encContext:
#Add padding and encrypt (for Block Cipher):
if self._writeState.encContext.isBlockCipher:
#Add TLS 1.1 fixed block
if self.version == (3,2):
bytes = self.fixedIVBlock + bytes
#Add padding: bytes = bytes + (macBytes + paddingBytes)
currentLength = len(bytes) + len(macBytes) + 1
blockLength = self._writeState.encContext.block_size
paddingLength = blockLength-(currentLength % blockLength)
paddingBytes = createByteArraySequence([paddingLength] * \
(paddingLength+1))
if self.fault == Fault.badPadding:
paddingBytes[0] = (paddingBytes[0]+1) % 256
endBytes = concatArrays(macBytes, paddingBytes)
bytes = concatArrays(bytes, endBytes)
#Encrypt
plaintext = stringToBytes(bytes)
ciphertext = self._writeState.encContext.encrypt(plaintext)
bytes = stringToBytes(ciphertext)
#Encrypt (for Stream Cipher)
else:
bytes = concatArrays(bytes, macBytes)
plaintext = bytesToString(bytes)
ciphertext = self._writeState.encContext.encrypt(plaintext)
bytes = stringToBytes(ciphertext)
#Add record header and send
r = RecordHeader3().create(self.version, contentType, len(bytes))
s = bytesToString(concatArrays(r.write(), bytes))
while 1:
try:
bytesSent = self.sock.send(s) #Might raise socket.error
except socket.error, why:
if why[0] == errno.EWOULDBLOCK:
yield 1
continue
else:
raise
if bytesSent == len(s):
return
s = s[bytesSent:]
yield 1
def _getMsg(self, expectedType, secondaryType=None, constructorType=None):
try:
if not isinstance(expectedType, tuple):
expectedType = (expectedType,)
#Spin in a loop, until we've got a non-empty record of a type we
#expect. The loop will be repeated if:
# - we receive a renegotiation attempt; we send no_renegotiation,
# then try again
# - we receive an empty application-data fragment; we try again
while 1:
for result in self._getNextRecord():
if result in (0,1):
yield result
recordHeader, p = result
#If this is an empty application-data fragment, try again
if recordHeader.type == ContentType.application_data:
if p.index == len(p.bytes):
continue
#If we received an unexpected record type...
if recordHeader.type not in expectedType:
#If we received an alert...
if recordHeader.type == ContentType.alert:
alert = Alert().parse(p)
#We either received a fatal error, a warning, or a
#close_notify. In any case, we're going to close the
#connection. In the latter two cases we respond with
#a close_notify, but ignore any socket errors, since
#the other side might have already closed the socket.
if alert.level == AlertLevel.warning or \
alert.description == AlertDescription.close_notify:
#If the sendMsg() call fails because the socket has
#already been closed, we will be forgiving and not
#report the error nor invalidate the "resumability"
#of the session.
try:
alertMsg = Alert()
alertMsg.create(AlertDescription.close_notify,
AlertLevel.warning)
for result in self._sendMsg(alertMsg):
yield result
except socket.error:
pass
if alert.description == \
AlertDescription.close_notify:
self._shutdown(True)
elif alert.level == AlertLevel.warning:
self._shutdown(False)
else: #Fatal alert:
self._shutdown(False)
#Raise the alert as an exception
raise TLSRemoteAlert(alert)
#If we received a renegotiation attempt...
if recordHeader.type == ContentType.handshake:
subType = p.get(1)
reneg = False
if self._client:
if subType == HandshakeType.hello_request:
reneg = True
else:
if subType == HandshakeType.client_hello:
reneg = True
#Send no_renegotiation, then try again
if reneg:
alertMsg = Alert()
alertMsg.create(AlertDescription.no_renegotiation,
AlertLevel.warning)
for result in self._sendMsg(alertMsg):
yield result
continue
#Otherwise: this is an unexpected record, but neither an
#alert nor renegotiation
for result in self._sendError(\
AlertDescription.unexpected_message,
"received type=%d" % recordHeader.type):
yield result
break
#Parse based on content_type
if recordHeader.type == ContentType.change_cipher_spec:
yield ChangeCipherSpec().parse(p)
elif recordHeader.type == ContentType.alert:
yield Alert().parse(p)
elif recordHeader.type == ContentType.application_data:
yield ApplicationData().parse(p)
elif recordHeader.type == ContentType.handshake:
#Convert secondaryType to tuple, if it isn't already
if not isinstance(secondaryType, tuple):
secondaryType = (secondaryType,)
#If it's a handshake message, check handshake header
if recordHeader.ssl2:
subType = p.get(1)
if subType != HandshakeType.client_hello:
for result in self._sendError(\
AlertDescription.unexpected_message,
"Can only handle SSLv2 ClientHello messages"):
yield result
if HandshakeType.client_hello not in secondaryType:
for result in self._sendError(\
AlertDescription.unexpected_message):
yield result
subType = HandshakeType.client_hello
else:
subType = p.get(1)
if subType not in secondaryType:
for result in self._sendError(\
AlertDescription.unexpected_message,
"Expecting %s, got %s" % (str(secondaryType), subType)):
yield result
#Update handshake hashes
sToHash = bytesToString(p.bytes)
self._handshake_md5.update(sToHash)
self._handshake_sha.update(sToHash)
#Parse based on handshake type
if subType == HandshakeType.client_hello:
yield ClientHello(recordHeader.ssl2).parse(p)
elif subType == HandshakeType.server_hello:
yield ServerHello().parse(p)
elif subType == HandshakeType.certificate:
yield Certificate(constructorType).parse(p)
elif subType == HandshakeType.certificate_request:
yield CertificateRequest().parse(p)
elif subType == HandshakeType.certificate_verify:
yield CertificateVerify().parse(p)
elif subType == HandshakeType.server_key_exchange:
yield ServerKeyExchange(constructorType).parse(p)
elif subType == HandshakeType.server_hello_done:
yield ServerHelloDone().parse(p)
elif subType == HandshakeType.client_key_exchange:
yield ClientKeyExchange(constructorType, \
self.version).parse(p)
elif subType == HandshakeType.finished:
yield Finished(self.version).parse(p)
else:
raise AssertionError()
#If an exception was raised by a Parser or Message instance:
except SyntaxError, e:
for result in self._sendError(AlertDescription.decode_error,
formatExceptionTrace(e)):
yield result
#Returns next record or next handshake message
def _getNextRecord(self):
#If there's a handshake message waiting, return it
if self._handshakeBuffer:
recordHeader, bytes = self._handshakeBuffer[0]
self._handshakeBuffer = self._handshakeBuffer[1:]
yield (recordHeader, Parser(bytes))
return
#Otherwise...
#Read the next record header
bytes = createByteArraySequence([])
recordHeaderLength = 1
ssl2 = False
while 1:
try:
s = self.sock.recv(recordHeaderLength-len(bytes))
except socket.error, why:
if why[0] == errno.EWOULDBLOCK:
yield 0
continue
else:
raise
#If the connection was abruptly closed, raise an error
if len(s)==0:
raise TLSAbruptCloseError()
bytes += stringToBytes(s)
if len(bytes)==1:
if bytes[0] in ContentType.all:
ssl2 = False
recordHeaderLength = 5
elif bytes[0] == 128:
ssl2 = True
recordHeaderLength = 2
else:
raise SyntaxError()
if len(bytes) == recordHeaderLength:
break
#Parse the record header
if ssl2:
r = RecordHeader2().parse(Parser(bytes))
else:
r = RecordHeader3().parse(Parser(bytes))
#Check the record header fields
if r.length > 18432:
for result in self._sendError(AlertDescription.record_overflow):
yield result
#Read the record contents
bytes = createByteArraySequence([])
while 1:
try:
s = self.sock.recv(r.length - len(bytes))
except socket.error, why:
if why[0] == errno.EWOULDBLOCK:
yield 0
continue
else:
raise
#If the connection is closed, raise a socket error
if len(s)==0:
raise TLSAbruptCloseError()
bytes += stringToBytes(s)
if len(bytes) == r.length:
break
#Check the record header fields (2)
#We do this after reading the contents from the socket, so that
#if there's an error, we at least don't leave extra bytes in the
#socket..
#
# THIS CHECK HAS NO SECURITY RELEVANCE (?), BUT COULD HURT INTEROP.
# SO WE LEAVE IT OUT FOR NOW.
#
#if self._versionCheck and r.version != self.version:
# for result in self._sendError(AlertDescription.protocol_version,
# "Version in header field: %s, should be %s" % (str(r.version),
# str(self.version))):
# yield result
#Decrypt the record
for result in self._decryptRecord(r.type, bytes):
if result in (0,1):
yield result
else:
break
bytes = result
p = Parser(bytes)
#If it doesn't contain handshake messages, we can just return it
if r.type != ContentType.handshake:
yield (r, p)
#If it's an SSLv2 ClientHello, we can return it as well
elif r.ssl2:
yield (r, p)
else:
#Otherwise, we loop through and add the handshake messages to the
#handshake buffer
while 1:
if p.index == len(bytes): #If we're at the end
if not self._handshakeBuffer:
for result in self._sendError(\
AlertDescription.decode_error, \
"Received empty handshake record"):
yield result
break
#There needs to be at least 4 bytes to get a header
if p.index+4 > len(bytes):
for result in self._sendError(\
AlertDescription.decode_error,
"A record has a partial handshake message (1)"):
yield result
p.get(1) # skip handshake type
msgLength = p.get(3)
if p.index+msgLength > len(bytes):
for result in self._sendError(\
AlertDescription.decode_error,
"A record has a partial handshake message (2)"):
yield result
handshakePair = (r, bytes[p.index-4 : p.index+msgLength])
self._handshakeBuffer.append(handshakePair)
p.index += msgLength
#We've moved at least one handshake message into the
#handshakeBuffer, return the first one
recordHeader, bytes = self._handshakeBuffer[0]
self._handshakeBuffer = self._handshakeBuffer[1:]
yield (recordHeader, Parser(bytes))
def _decryptRecord(self, recordType, bytes):
if self._readState.encContext:
#Decrypt if it's a block cipher
if self._readState.encContext.isBlockCipher:
blockLength = self._readState.encContext.block_size
if len(bytes) % blockLength != 0:
for result in self._sendError(\
AlertDescription.decryption_failed,
"Encrypted data not a multiple of blocksize"):
yield result
ciphertext = bytesToString(bytes)
plaintext = self._readState.encContext.decrypt(ciphertext)
if self.version == (3,2): #For TLS 1.1, remove explicit IV
plaintext = plaintext[self._readState.encContext.block_size : ]
bytes = stringToBytes(plaintext)
#Check padding
paddingGood = True
paddingLength = bytes[-1]
if (paddingLength+1) > len(bytes):
paddingGood=False
totalPaddingLength = 0
else:
if self.version == (3,0):
totalPaddingLength = paddingLength+1
elif self.version in ((3,1), (3,2)):
totalPaddingLength = paddingLength+1
paddingBytes = bytes[-totalPaddingLength:-1]
for byte in paddingBytes:
if byte != paddingLength:
paddingGood = False
totalPaddingLength = 0
else:
raise AssertionError()
#Decrypt if it's a stream cipher
else:
paddingGood = True
ciphertext = bytesToString(bytes)
plaintext = self._readState.encContext.decrypt(ciphertext)
bytes = stringToBytes(plaintext)
totalPaddingLength = 0
#Check MAC
macGood = True
macLength = self._readState.macContext.digest_size
endLength = macLength + totalPaddingLength
if endLength > len(bytes):
macGood = False
else:
#Read MAC
startIndex = len(bytes) - endLength
endIndex = startIndex + macLength
checkBytes = bytes[startIndex : endIndex]
#Calculate MAC
seqnumStr = self._readState.getSeqNumStr()
bytes = bytes[:-endLength]
bytesStr = bytesToString(bytes)
mac = self._readState.macContext.copy()
mac.update(seqnumStr)
mac.update(chr(recordType))
if self.version == (3,0):
mac.update( chr( int(len(bytes)/256) ) )
mac.update( chr( int(len(bytes)%256) ) )
elif self.version in ((3,1), (3,2)):
mac.update(chr(self.version[0]))
mac.update(chr(self.version[1]))
mac.update( chr( int(len(bytes)/256) ) )
mac.update( chr( int(len(bytes)%256) ) )
else:
raise AssertionError()
mac.update(bytesStr)
macString = mac.digest()
macBytes = stringToBytes(macString)
#Compare MACs
if macBytes != checkBytes:
macGood = False
if not (paddingGood and macGood):
for result in self._sendError(AlertDescription.bad_record_mac,
"MAC failure (or padding failure)"):
yield result
yield bytes
def _handshakeStart(self, client):
self._client = client
self._handshake_md5 = md5.md5()
self._handshake_sha = sha.sha()
self._handshakeBuffer = []
self.allegedSharedKeyUsername = None
self.allegedSrpUsername = None
self._refCount = 1
def _handshakeDone(self, resumed):
self.resumed = resumed
self.closed = False
def _calcPendingStates(self, clientRandom, serverRandom, implementations):
if self.session.cipherSuite in CipherSuite.aes128Suites:
macLength = 20
keyLength = 16
ivLength = 16
createCipherFunc = createAES
elif self.session.cipherSuite in CipherSuite.aes256Suites:
macLength = 20
keyLength = 32
ivLength = 16
createCipherFunc = createAES
elif self.session.cipherSuite in CipherSuite.rc4Suites:
macLength = 20
keyLength = 16
ivLength = 0
createCipherFunc = createRC4
elif self.session.cipherSuite in CipherSuite.tripleDESSuites:
macLength = 20
keyLength = 24
ivLength = 8
createCipherFunc = createTripleDES
else:
raise AssertionError()
if self.version == (3,0):
createMACFunc = MAC_SSL
elif self.version in ((3,1), (3,2)):
createMACFunc = hmac.HMAC
outputLength = (macLength*2) + (keyLength*2) + (ivLength*2)
#Calculate Keying Material from Master Secret
if self.version == (3,0):
keyBlock = PRF_SSL(self.session.masterSecret,
concatArrays(serverRandom, clientRandom),
outputLength)
elif self.version in ((3,1), (3,2)):
keyBlock = PRF(self.session.masterSecret,
"key expansion",
concatArrays(serverRandom,clientRandom),
outputLength)
else:
raise AssertionError()
#Slice up Keying Material
clientPendingState = _ConnectionState()
serverPendingState = _ConnectionState()
p = Parser(keyBlock)
clientMACBlock = bytesToString(p.getFixBytes(macLength))
serverMACBlock = bytesToString(p.getFixBytes(macLength))
clientKeyBlock = bytesToString(p.getFixBytes(keyLength))
serverKeyBlock = bytesToString(p.getFixBytes(keyLength))
clientIVBlock = bytesToString(p.getFixBytes(ivLength))
serverIVBlock = bytesToString(p.getFixBytes(ivLength))
clientPendingState.macContext = createMACFunc(clientMACBlock,
digestmod=sha)
serverPendingState.macContext = createMACFunc(serverMACBlock,
digestmod=sha)
clientPendingState.encContext = createCipherFunc(clientKeyBlock,
clientIVBlock,
implementations)
serverPendingState.encContext = createCipherFunc(serverKeyBlock,
serverIVBlock,
implementations)
#Assign new connection states to pending states
if self._client:
self._pendingWriteState = clientPendingState
self._pendingReadState = serverPendingState
else:
self._pendingWriteState = serverPendingState
self._pendingReadState = clientPendingState
if self.version == (3,2) and ivLength:
#Choose fixedIVBlock for TLS 1.1 (this is encrypted with the CBC
#residue to create the IV for each sent block)
self.fixedIVBlock = getRandomBytes(ivLength)
def _changeWriteState(self):
self._writeState = self._pendingWriteState
self._pendingWriteState = _ConnectionState()
def _changeReadState(self):
self._readState = self._pendingReadState
self._pendingReadState = _ConnectionState()
def _sendFinished(self):
#Send ChangeCipherSpec
for result in self._sendMsg(ChangeCipherSpec()):
yield result
#Switch to pending write state
self._changeWriteState()
#Calculate verification data
verifyData = self._calcFinished(True)
if self.fault == Fault.badFinished:
verifyData[0] = (verifyData[0]+1)%256
#Send Finished message under new state
finished = Finished(self.version).create(verifyData)
for result in self._sendMsg(finished):
yield result
def _getFinished(self):
#Get and check ChangeCipherSpec
for result in self._getMsg(ContentType.change_cipher_spec):
if result in (0,1):
yield result
changeCipherSpec = result
if changeCipherSpec.type != 1:
for result in self._sendError(AlertDescription.illegal_parameter,
"ChangeCipherSpec type incorrect"):
yield result
#Switch to pending read state
self._changeReadState()
#Calculate verification data
verifyData = self._calcFinished(False)
#Get and check Finished message under new state
for result in self._getMsg(ContentType.handshake,
HandshakeType.finished):
if result in (0,1):
yield result
finished = result
if finished.verify_data != verifyData:
for result in self._sendError(AlertDescription.decrypt_error,
"Finished message is incorrect"):
yield result
def _calcFinished(self, send=True):
if self.version == (3,0):
if (self._client and send) or (not self._client and not send):
senderStr = "\x43\x4C\x4E\x54"
else:
senderStr = "\x53\x52\x56\x52"
verifyData = self._calcSSLHandshakeHash(self.session.masterSecret,
senderStr)
return verifyData
elif self.version in ((3,1), (3,2)):
if (self._client and send) or (not self._client and not send):
label = "client finished"
else:
label = "server finished"
handshakeHashes = stringToBytes(self._handshake_md5.digest() + \
self._handshake_sha.digest())
verifyData = PRF(self.session.masterSecret, label, handshakeHashes,
12)
return verifyData
else:
raise AssertionError()
#Used for Finished messages and CertificateVerify messages in SSL v3
def _calcSSLHandshakeHash(self, masterSecret, label):
masterSecretStr = bytesToString(masterSecret)
imac_md5 = self._handshake_md5.copy()
imac_sha = self._handshake_sha.copy()
imac_md5.update(label + masterSecretStr + '\x36'*48)
imac_sha.update(label + masterSecretStr + '\x36'*40)
md5Str = md5.md5(masterSecretStr + ('\x5c'*48) + \
imac_md5.digest()).digest()
shaStr = sha.sha(masterSecretStr + ('\x5c'*40) + \
imac_sha.digest()).digest()
return stringToBytes(md5Str + shaStr)
|