diff --git a/changes/bug11513 b/changes/bug11513 new file mode 100644 index 000000000..820c02605 --- /dev/null +++ b/changes/bug11513 @@ -0,0 +1,12 @@ + o Major bugfixes: + - Generate the server's preference list for ciphersuites + automatically based on uniform criteria, and considering all + OpenSSL ciphersuites with acceptable strength and forward + secrecy. (The sort order is: prefer AES to 3DES; break ties by + preferring ECDHE to DHE; break ties by preferring GCM to CBC; + break ties by preferring SHA384 to SHA256 to SHA1; and finally, + break ties by preferring AES256 to AES128.) This resolves bugs + #11513, #11492, #11498, #11499. Bugs reported by 'cypherpunks'. + Bugfix on 0.2.4.8-alpha. + + diff --git a/src/common/gen_server_ciphers.py b/src/common/gen_server_ciphers.py new file mode 100755 index 000000000..97ed9d046 --- /dev/null +++ b/src/common/gen_server_ciphers.py @@ -0,0 +1,115 @@ +#!/usr/bin/python +# Copyright 2014, The Tor Project, Inc +# See LICENSE for licensing information + +# This script parses openssl headers to find ciphersuite names, determines +# which ones we should be willing to use as a server, and sorts them according +# to preference rules. +# +# Run it on all the files in your openssl include directory. + +import re +import sys + +EPHEMERAL_INDICATORS = [ "_EDH_", "_DHE_", "_ECDHE_" ] +BAD_STUFF = [ "_DES_40_", "MD5", "_RC4_", "_DES_64_", + "_SEED_", "_CAMELLIA_", "_NULL" ] + +# these never get #ifdeffed. +MANDATORY = [ + "TLS1_TXT_DHE_RSA_WITH_AES_256_SHA", + "TLS1_TXT_DHE_RSA_WITH_AES_128_SHA", + "SSL3_TXT_EDH_RSA_DES_192_CBC3_SHA", +] + +def find_ciphers(filename): + with open(filename) as f: + for line in f: + m = re.search(r'(?:SSL3|TLS1)_TXT_\w+', line) + if m: + yield m.group(0) + +def usable_cipher(ciph): + ephemeral = False + for e in EPHEMERAL_INDICATORS: + if e in ciph: + ephemeral = True + if not ephemeral: + return False + + if "_RSA_" not in ciph: + return False + + for b in BAD_STUFF: + if b in ciph: + return False + return True + +# All fields we sort on, in order of priority. +FIELDS = [ 'cipher', 'fwsec', 'mode', 'digest', 'bitlength' ] +# Map from sorted fields to recognized value in descending order of goodness +FIELD_VALS = { 'cipher' : [ 'AES', 'DES'], + 'fwsec' : [ 'ECDHE', 'DHE' ], + 'mode' : [ 'GCM', 'CBC' ], + 'digest' : [ 'SHA384', 'SHA256', 'SHA' ], + 'bitlength' : [ '256', '128', '192' ], +} + +class Ciphersuite(object): + def __init__(self, name, fwsec, cipher, bitlength, mode, digest): + self.name = name + self.fwsec = fwsec + self.cipher = cipher + self.bitlength = bitlength + self.mode = mode + self.digest = digest + + for f in FIELDS: + assert(getattr(self, f) in FIELD_VALS[f]) + + def sort_key(self): + return tuple(FIELD_VALS[f].index(getattr(self,f)) for f in FIELDS) + + +def parse_cipher(ciph): + m = re.match('(?:TLS1|SSL3)_TXT_(EDH|DHE|ECDHE)_RSA(?:_WITH)?_(AES|DES)_(256|128|192)(|_CBC|_CBC3|_GCM)_(SHA|SHA256|SHA384)$', ciph) + + if not m: + print "/* Couldn't parse %s ! */"%ciph + return None + + fwsec, cipher, bits, mode, digest = m.groups() + if fwsec == 'EDH': + fwsec = 'DHE' + + if mode in [ '_CBC3', '_CBC', '' ]: + mode = 'CBC' + elif mode == '_GCM': + mode = 'GCM' + + return Ciphersuite(ciph, fwsec, cipher, bits, mode, digest) + +ALL_CIPHERS = [] + +for fname in sys.argv[1:]: + ALL_CIPHERS += (parse_cipher(c) + for c in find_ciphers(fname) + if usable_cipher(c) ) + +ALL_CIPHERS.sort(key=Ciphersuite.sort_key) + +for c in ALL_CIPHERS: + if c is ALL_CIPHERS[-1]: + colon = ';' + else: + colon = ' ":"' + + if c.name in MANDATORY: + print " /* Required */" + print ' %s%s'%(c.name,colon) + else: + print "#ifdef %s"%c.name + print ' %s%s'%(c.name,colon) + print "#endif" + + diff --git a/src/common/tortls.c b/src/common/tortls.c index 886ee0dda..bbbf6a5ef 100644 --- a/src/common/tortls.c +++ b/src/common/tortls.c @@ -714,31 +714,47 @@ tor_tls_create_certificate(crypto_pk_t *rsa, /** List of ciphers that servers should select from when we actually have * our choice of what cipher to use. */ const char UNRESTRICTED_SERVER_CIPHER_LIST[] = -#ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_256_CHC_SHA - TLS1_TXT_ECDHE_RSA_WITH_AES_256_CBC_SHA ":" -#endif + /* This list is autogenerated with the gen_server_ciphers.py script; + * don't hand-edit it. */ #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_256_GCM_SHA384 TLS1_TXT_ECDHE_RSA_WITH_AES_256_GCM_SHA384 ":" #endif +#ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_128_GCM_SHA256 + TLS1_TXT_ECDHE_RSA_WITH_AES_128_GCM_SHA256 ":" +#endif +#ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_256_SHA384 + TLS1_TXT_ECDHE_RSA_WITH_AES_256_SHA384 ":" +#endif #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_128_SHA256 TLS1_TXT_ECDHE_RSA_WITH_AES_128_SHA256 ":" #endif +#ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_256_CBC_SHA + TLS1_TXT_ECDHE_RSA_WITH_AES_256_CBC_SHA ":" +#endif #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_128_CBC_SHA TLS1_TXT_ECDHE_RSA_WITH_AES_128_CBC_SHA ":" #endif -#ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - TLS1_TXT_ECDHE_RSA_WITH_AES_128_GCM_SHA256 +#ifdef TLS1_TXT_DHE_RSA_WITH_AES_256_GCM_SHA384 + TLS1_TXT_DHE_RSA_WITH_AES_256_GCM_SHA384 ":" #endif -//#if TLS1_TXT_ECDHE_RSA_WITH_RC4_128_SHA -// TLS1_TXT_ECDHE_RSA_WITH_RC4_128_SHA ":" -//#endif - /* These next two are mandatory. */ - TLS1_TXT_DHE_RSA_WITH_AES_256_SHA ":" - TLS1_TXT_DHE_RSA_WITH_AES_128_SHA ":" +#ifdef TLS1_TXT_DHE_RSA_WITH_AES_128_GCM_SHA256 + TLS1_TXT_DHE_RSA_WITH_AES_128_GCM_SHA256 ":" +#endif +#ifdef TLS1_TXT_DHE_RSA_WITH_AES_256_SHA256 + TLS1_TXT_DHE_RSA_WITH_AES_256_SHA256 ":" +#endif +#ifdef TLS1_TXT_DHE_RSA_WITH_AES_128_SHA256 + TLS1_TXT_DHE_RSA_WITH_AES_128_SHA256 ":" +#endif + /* Required */ + TLS1_TXT_DHE_RSA_WITH_AES_256_SHA ":" + /* Required */ + TLS1_TXT_DHE_RSA_WITH_AES_128_SHA ":" #ifdef TLS1_TXT_ECDHE_RSA_WITH_DES_192_CBC3_SHA TLS1_TXT_ECDHE_RSA_WITH_DES_192_CBC3_SHA ":" #endif - SSL3_TXT_EDH_RSA_DES_192_CBC3_SHA; + /* Required */ + SSL3_TXT_EDH_RSA_DES_192_CBC3_SHA; /* Note: to set up your own private testing network with link crypto * disabled, set your Tors' cipher list to