From: Zooko O'Whielacronx Date: Tue, 24 Jul 2007 20:46:06 +0000 (-0700) Subject: switch from rfc 3548 base-32 to z-base-32 except for tubids/nodeids X-Git-Url: https://git.rkrishnan.org/%5B/%5D%20/file/URI:LIT:krugkidfnzsc4/%3C?a=commitdiff_plain;h=32c90c6468983f39798bba117d0e289965176c73;p=tahoe-lafs%2Ftahoe-lafs.git switch from rfc 3548 base-32 to z-base-32 except for tubids/nodeids --- diff --git a/src/allmydata/introducer.py b/src/allmydata/introducer.py index 8db66b2d..d5c4a306 100644 --- a/src/allmydata/introducer.py +++ b/src/allmydata/introducer.py @@ -1,4 +1,6 @@ +from base64 import b32encode, b32decode + import re from zope.interface import implements from twisted.application import service @@ -92,9 +94,9 @@ class IntroducerClient(service.Service, Referenceable): # them, which may or may not be what we want. m = re.match(r'pb://(\w+)@', furl) assert m - nodeid = idlib.a2b(m.group(1)) + nodeid = b32decode(m.group(1).upper()) def _got_peer(rref): - self.log(" connected to(%s)" % idlib.b2a(nodeid)) + self.log(" connected to(%s)" % b32encode(nodeid).lower()) self.connection_observers.notify(nodeid, rref) self.connections[nodeid] = rref def _lost(): diff --git a/src/allmydata/node.py b/src/allmydata/node.py index 941b4d29..41ef9c69 100644 --- a/src/allmydata/node.py +++ b/src/allmydata/node.py @@ -1,3 +1,5 @@ +from base64 import b32encode, b32decode + import os.path, re import twisted @@ -5,7 +7,7 @@ from twisted.python import log from twisted.application import service from twisted.internet import defer, reactor from foolscap import Tub, eventual -from allmydata.util import idlib, iputil, observer +from allmydata.util import iputil, observer from allmydata.util.assertutil import precondition @@ -34,9 +36,9 @@ class Node(service.MultiService): self.tub = Tub(certFile=certfile) self.tub.setOption("logLocalFailures", True) self.tub.setOption("logRemoteFailures", True) - self.nodeid = idlib.a2b(self.tub.tubID) + self.nodeid = b32encode(self.tub.tubID).lower() f = open(os.path.join(self.basedir, self.NODEIDFILE), "w") - f.write(idlib.b2a(self.nodeid) + "\n") + f.write(b32encode(self.nodeid).lower() + "\n") f.close() self.short_nodeid = self.tub.tubID[:4] # ready for printing assert self.PORTNUMFILE, "Your node.Node subclass must provide PORTNUMFILE" diff --git a/src/allmydata/test/test_introducer.py b/src/allmydata/test/test_introducer.py index 5154f4e7..bbdc47d7 100644 --- a/src/allmydata/test/test_introducer.py +++ b/src/allmydata/test/test_introducer.py @@ -1,3 +1,4 @@ +from base64 import b32encode, b32decode from twisted.trial import unittest from twisted.internet import defer, reactor @@ -7,7 +8,7 @@ from foolscap import Tub, Referenceable from foolscap.eventual import flushEventualQueue from twisted.application import service from allmydata.introducer import IntroducerClient, Introducer -from allmydata.util import idlib, testutil +from allmydata.util import testutil class MyNode(Referenceable): pass @@ -56,7 +57,7 @@ class TestIntroducer(unittest.TestCase, testutil.PollMixin): self.waiting_for_connections = NUMCLIENTS*NUMCLIENTS d = self._done_counting = defer.Deferred() def _count(nodeid, rref): - log.msg("NEW CONNECTION! %s %s" % (idlib.b2a(nodeid), rref)) + log.msg("NEW CONNECTION! %s %s" % (b32encode(nodeid).lower(), rref)) self.waiting_for_connections -= 1 if self.waiting_for_connections == 0: self._done_counting.callback("done!") @@ -92,7 +93,7 @@ class TestIntroducer(unittest.TestCase, testutil.PollMixin): origin_c = clients[0] # find a target that is not themselves for nodeid,rref in origin_c.connections.items(): - if idlib.b2a(nodeid) != tubs[origin_c].tubID: + if b32encode(nodeid).lower() != tubs[origin_c].tubID: victim = rref break log.msg(" disconnecting %s->%s" % (tubs[origin_c].tubID, victim)) @@ -111,7 +112,7 @@ class TestIntroducer(unittest.TestCase, testutil.PollMixin): origin_c = clients[0] # find a target that *is* themselves for nodeid,rref in origin_c.connections.items(): - if idlib.b2a(nodeid) == tubs[origin_c].tubID: + if b32encode(nodeid).lower() == tubs[origin_c].tubID: victim = rref break log.msg(" disconnecting %s->%s" % (tubs[origin_c].tubID, victim)) diff --git a/src/allmydata/test/test_util.py b/src/allmydata/test/test_util.py index 0b7138cd..118dd6a7 100644 --- a/src/allmydata/test/test_util.py +++ b/src/allmydata/test/test_util.py @@ -10,18 +10,13 @@ from allmydata.util import assertutil, fileutil class IDLib(unittest.TestCase): def test_b2a(self): - self.failUnlessEqual(idlib.b2a("\x12\x34"), "ci2a====") + self.failUnlessEqual(idlib.b2a("\x12\x34"), "ne4y") def test_b2a_or_none(self): self.failUnlessEqual(idlib.b2a_or_none(None), None) - self.failUnlessEqual(idlib.b2a_or_none("\x12\x34"), "ci2a====") + self.failUnlessEqual(idlib.b2a_or_none("\x12\x34"), "ne4y") def test_a2b(self): - self.failUnlessEqual(idlib.a2b("ci2a===="), "\x12\x34") - self.failUnlessRaises(TypeError, idlib.a2b, "bogus") - def test_peerid(self): - # these are 160-bit numbers - peerid = "\x80" + "\x00" * 19 - short = idlib.peerid_to_short_string(peerid) - self.failUnlessEqual(short, "qaaa") + self.failUnlessEqual(idlib.a2b("ne4y"), "\x12\x34") + self.failUnlessRaises(AssertionError, idlib.a2b, "b0gus") class NoArgumentException(Exception): def __init__(self): diff --git a/src/allmydata/util/idlib.py b/src/allmydata/util/idlib.py index 185b3a3b..0f89a33c 100644 --- a/src/allmydata/util/idlib.py +++ b/src/allmydata/util/idlib.py @@ -1,22 +1,251 @@ -from base64 import b32encode, b32decode +# from the Python Standard Library +import string -def b2a(i): - assert isinstance(i, str), "tried to idlib.b2a non-string '%s'" % (i,) - return b32encode(i).lower() +from assertutil import _assert, precondition -def b2a_or_none(i): - if i is None: - return None - return b2a(i) +z_base_32_alphabet = "ybndrfg8ejkmcpqxot1uwisza345h769" # Zooko's choice, rationale in "DESIGN" doc +rfc3548_alphabet = "abcdefghijklmnopqrstuvwxyz234567" # RFC3548 standard used by Gnutella, Content-Addressable Web, THEX, Bitzi, Web-Calculus... +chars = z_base_32_alphabet -def a2b(i): - assert isinstance(i, str), "tried to idlib.a2b non-string '%s'" % (i,) - try: - return b32decode(i.upper()) - except TypeError: - print "b32decode failed on a %s byte string '%s'" % (len(i), i) - raise +vals = ''.join(map(chr, range(32))) +c2vtranstable = string.maketrans(chars, vals) +v2ctranstable = string.maketrans(vals, chars) +identitytranstable = string.maketrans(chars, chars) +def _get_trailing_chars_without_lsbs(N, d): + """ + @return: a list of chars that can legitimately appear in the last place when the least significant N bits are ignored. + """ + s = [] + if N < 4: + s.extend(_get_trailing_chars_without_lsbs(N+1, d=d)) + i = 0 + while i < len(chars): + if not d.has_key(i): + d[i] = None + s.append(chars[i]) + i = i + 2**N + return s + +def get_trailing_chars_without_lsbs(N): + precondition((N >= 0) and (N < 5), "N is required to be > 0 and < len(chars).", N=N) + if N == 0: + return chars + d = {} + return ''.join(_get_trailing_chars_without_lsbs(N, d=d)) + +def b2a(os): + """ + @param os the data to be encoded (a string) + + @return the contents of os in base-32 encoded form + """ + return b2a_l(os, len(os)*8) + +def b2a_or_none(os): + if os is not None: + return b2a(os) + +def b2a_l(os, lengthinbits): + """ + @param os the data to be encoded (a string) + @param lengthinbits the number of bits of data in os to be encoded + + b2a_l() will generate a base-32 encoded string big enough to encode lengthinbits bits. So for + example if os is 2 bytes long and lengthinbits is 15, then b2a_l() will generate a 3-character- + long base-32 encoded string (since 3 quintets is sufficient to encode 15 bits). If os is + 2 bytes long and lengthinbits is 16 (or None), then b2a_l() will generate a 4-character string. + Note that b2a_l() does not mask off unused least-significant bits, so for example if os is + 2 bytes long and lengthinbits is 15, then you must ensure that the unused least-significant bit + of os is a zero bit or you will get the wrong result. This precondition is tested by assertions + if assertions are enabled. + + Warning: if you generate a base-32 encoded string with b2a_l(), and then someone else tries to + decode it by calling a2b() instead of a2b_l(), then they will (probably) get a different + string than the one you encoded! So only use b2a_l() when you are sure that the encoding and + decoding sides know exactly which lengthinbits to use. If you do not have a way for the + encoder and the decoder to agree upon the lengthinbits, then it is best to use b2a() and + a2b(). The only drawback to using b2a() over b2a_l() is that when you have a number of + bits to encode that is not a multiple of 8, b2a() can sometimes generate a base-32 encoded + string that is one or two characters longer than necessary. + + @return the contents of os in base-32 encoded form + """ + precondition(isinstance(lengthinbits, (int, long,)), "lengthinbits is required to be an integer.", lengthinbits=lengthinbits) + precondition((lengthinbits+7)/8 == len(os), "lengthinbits is required to specify a number of bits storable in exactly len(os) octets.", lengthinbits=lengthinbits, lenos=len(os)) + + os = map(ord, os) + + numquintets = (lengthinbits+4)/5 + numoctetsofdata = (lengthinbits+7)/8 + # print "numoctetsofdata: %s, len(os): %s, lengthinbits: %s, numquintets: %s" % (numoctetsofdata, len(os), lengthinbits, numquintets,) + # strip trailing octets that won't be used + del os[numoctetsofdata:] + # zero out any unused bits in the final octet + if lengthinbits % 8 != 0: + os[-1] = os[-1] >> (8-(lengthinbits % 8)) + os[-1] = os[-1] << (8-(lengthinbits % 8)) + # append zero octets for padding if needed + numoctetsneeded = (numquintets*5+7)/8 + 1 + os.extend([0]*(numoctetsneeded-len(os))) + + quintets = [] + cutoff = 256 + num = os[0] + i = 0 + while len(quintets) < numquintets: + i = i + 1 + assert len(os) > i, "len(os): %s, i: %s, len(quintets): %s, numquintets: %s, lengthinbits: %s, numoctetsofdata: %s, numoctetsneeded: %s, os: %s" % (len(os), i, len(quintets), numquintets, lengthinbits, numoctetsofdata, numoctetsneeded, os,) + num = num * 256 + num = num + os[i] + if cutoff == 1: + cutoff = 256 + continue + cutoff = cutoff * 8 + quintet = num / cutoff + quintets.append(quintet) + num = num - (quintet * cutoff) + + cutoff = cutoff / 32 + quintet = num / cutoff + quintets.append(quintet) + num = num - (quintet * cutoff) + + if len(quintets) > numquintets: + assert len(quintets) == (numquintets+1), "len(quintets): %s, numquintets: %s, quintets: %s" % (len(quintets), numquintets, quintets,) + quintets = quintets[:numquintets] + res = string.translate(string.join(map(chr, quintets), ''), v2ctranstable) + assert could_be_base32_encoded_l(res, lengthinbits), "lengthinbits: %s, res: %s" % (lengthinbits, res,) + return res + +# b2a() uses the minimal number of quintets sufficient to encode the binary +# input. It just so happens that the relation is like this (everything is +# modulo 40 bits). +# num_qs = NUM_OS_TO_NUM_QS[num_os] +NUM_OS_TO_NUM_QS=(0, 2, 4, 5, 7,) + +# num_os = NUM_QS_TO_NUM_OS[num_qs], but if not NUM_QS_LEGIT[num_qs] then +# there is *no* number of octets which would have resulted in this number of +# quintets, so either the encoded string has been mangled (truncated) or else +# you were supposed to decode it with a2b_l() (which means you were supposed +# to know the actual length of the encoded data). + +NUM_QS_TO_NUM_OS=(0, 1, 1, 2, 2, 3, 3, 4) +NUM_QS_LEGIT=(1, 0, 1, 0, 1, 1, 0, 1,) +NUM_QS_TO_NUM_BITS=tuple(map(lambda x: x*8, NUM_QS_TO_NUM_OS)) + +# A fast way to determine whether a given string *could* be base-32 encoded data, assuming that the +# original data had 8K bits for a positive integer K. +# The boolean value of s8[len(s)%8][ord(s[-1])], where s is the possibly base-32 encoded string +# tells whether the final character is reasonable. +def add_check_array(cs, sfmap): + checka=[0] * 256 + for c in cs: + checka[ord(c)] = 1 + sfmap.append(tuple(checka)) + +def init_s8(): + s8 = [] + add_check_array(chars, s8) + for lenmod8 in (1, 2, 3, 4, 5, 6, 7,): + if NUM_QS_LEGIT[lenmod8]: + add_check_array(get_trailing_chars_without_lsbs(4-(NUM_QS_TO_NUM_BITS[lenmod8]%5)), s8) + else: + add_check_array('', s8) + return tuple(s8) +s8 = init_s8() + +# A somewhat fast way to determine whether a given string *could* be base-32 encoded data, given a +# lengthinbits. +# The boolean value of s5[lengthinbits%5][ord(s[-1])], where s is the possibly base-32 encoded +# string tells whether the final character is reasonable. +def init_s5(): + s5 = [] + add_check_array(chars, s5) + for lenmod5 in (1, 2, 3, 4,): + add_check_array(get_trailing_chars_without_lsbs(4-lenmod5), s5) + return tuple(s5) +s5 = init_s5() + +def could_be_base32_encoded(s, s8=s8, tr=string.translate, identitytranstable=identitytranstable, chars=chars): + if s == '': + return True + return s8[len(s)%8][ord(s[-1])] and not tr(s, identitytranstable, chars) + +def could_be_base32_encoded_l(s, lengthinbits, s5=s5, tr=string.translate, identitytranstable=identitytranstable, chars=chars): + if s == '': + return True + assert lengthinbits%5 < len(s5), lengthinbits + assert ord(s[-1]) < s5[lengthinbits%5] + return (((lengthinbits+4)/5) == len(s)) and s5[lengthinbits%5][ord(s[-1])] and not string.translate(s, identitytranstable, chars) + +def num_octets_that_encode_to_this_many_quintets(numqs): + # Here is a computation that conveniently expresses this: + return (numqs*5+3)/8 + +def a2b(cs): + """ + @param cs the base-32 encoded data (a string) + """ + precondition(could_be_base32_encoded(cs), "cs is required to be possibly base32 encoded data.", cs=cs) + + return a2b_l(cs, num_octets_that_encode_to_this_many_quintets(len(cs))*8) + +def a2b_l(cs, lengthinbits): + """ + @param lengthinbits the number of bits of data in encoded into cs + + a2b_l() will return a result big enough to hold lengthinbits bits. So for example if cs is + 4 characters long (encoding at least 15 and up to 20 bits) and lengthinbits is 16, then a2b_l() + will return a string of length 2 (since 2 bytes is sufficient to store 16 bits). If cs is 4 + characters long and lengthinbits is 20, then a2b_l() will return a string of length 3 (since + 3 bytes is sufficient to store 20 bits). Note that b2a_l() does not mask off unused least- + significant bits, so for example if cs is 4 characters long and lengthinbits is 17, then you + must ensure that all three of the unused least-significant bits of cs are zero bits or you will + get the wrong result. This precondition is tested by assertions if assertions are enabled. + (Generally you just require the encoder to ensure this consistency property between the least + significant zero bits and value of lengthinbits, and reject strings that have a length-in-bits + which isn't a multiple of 8 and yet don't have trailing zero bits, as improperly encoded.) + + Please see the warning in the docstring of b2a_l() regarding the use of b2a() versus b2a_l(). + + @return the data encoded in cs + """ + precondition(could_be_base32_encoded_l(cs, lengthinbits), "cs is required to be possibly base32 encoded data.", cs=cs, lengthinbits=lengthinbits) + if cs == '': + return '' + + qs = map(ord, string.translate(cs, c2vtranstable)) + + numoctets = (lengthinbits+7)/8 + numquintetsofdata = (lengthinbits+4)/5 + # strip trailing quintets that won't be used + del qs[numquintetsofdata:] + # zero out any unused bits in the final quintet + if lengthinbits % 5 != 0: + qs[-1] = qs[-1] >> (5-(lengthinbits % 5)) + qs[-1] = qs[-1] << (5-(lengthinbits % 5)) + # append zero quintets for padding if needed + numquintetsneeded = (numoctets*8+4)/5 + qs.extend([0]*(numquintetsneeded-len(qs))) + + octets = [] + pos = 2048 + num = qs[0] * pos + readybits = 5 + i = 1 + while len(octets) < numoctets: + while pos > 256: + pos = pos / 32 + num = num + (qs[i] * pos) + i = i + 1 + octet = num / 256 + octets.append(octet) + num = num - (octet * 256) + num = num * 256 + pos = pos * 256 + assert len(octets) == numoctets, "len(octets): %s, numoctets: %s, octets: %s" % (len(octets), numoctets, octets,) + res = ''.join(map(chr, octets)) + precondition(b2a_l(res, lengthinbits) == cs, "cs is required to be the canonical base-32 encoding of some data.", b2a(res), res=res, cs=cs) + return res -def peerid_to_short_string(peerid): - return b2a(peerid)[:4]