diff --git a/ChangeLog b/ChangeLog index 31c00be..dcbed39 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,7 @@ Version 1.0.0 - Add support for RFC 8460 tlsrpt DKIM signature processing (LP: #1847020) + - Add async support with aiodns for DKIM verification (ARC not supported) + (LP: #1847002) - Add new timeout parameter to enable DNS lookup timeouts to be adjusted - Add new DKIM.present function to allow applications to test if a DKIM signature is present without doing validation (LP: #1851141) diff --git a/README b/README index 0d3a0bd..f472afb 100644 --- a/README +++ b/README @@ -19,6 +19,8 @@ Dependencies will be automatically included for normal DKIM usage. The extras_requires feature 'ed25519' will add the dependencies needed for signing and verifying using the new DCRUP ed25519-sha256 algorithm. The extras_requires feature 'ARC' will add the extra dependencies needed for ARC. +Similarly, extras_requires feature 'asyncio' will add the extra dependencies +needed for asyncio. - Python 2.x >= 2.7, or Python 3.x >= 3.5. Recent versions have not been tested on python < 2.7 or python3 < 3.5, but may still work on python2.6 @@ -28,6 +30,7 @@ extras_requires feature 'ARC' will add the extra dependencies needed for ARC. - argparse. Standard library in python2.7 and later. - authres. Needed for ARC. - PyNaCl. Needed for use of ed25519 capability. + - aiodns. Needed for asycnio (Required python3.5 or later) INSTALLATION diff --git a/dkim/__init__.py b/dkim/__init__.py index 9846598..171e668 100644 --- a/dkim/__init__.py +++ b/dkim/__init__.py @@ -36,6 +36,7 @@ import base64 import hashlib import logging import re +import sys import time import binascii @@ -71,8 +72,13 @@ from dkim.crypto import ( try: from dkim.dnsplug import get_txt except ImportError: - def get_txt(s,timeout=5): - raise RuntimeError("DKIM.verify requires DNS or dnspython module") + try: + import aiodns + from dkim.asyncsupport import get_txt_async as get_txt + except: + # Only true if not using async + def get_txt(s,timeout=5): + raise RuntimeError("DKIM.verify requires DNS or dnspython module") from dkim.util import ( get_default_logger, InvalidTagValueList, @@ -420,8 +426,7 @@ def fold(header, namelen=0, linesep=b'\r\n'): return pre + header -def load_pk_from_dns(name, dnsfunc=get_txt, timeout=5): - s = dnsfunc(name, timeout=timeout) +def evaluate_pk(name, s): if not s: raise KeyFormatError("missing public key: %s"%name) try: @@ -470,6 +475,12 @@ def load_pk_from_dns(name, dnsfunc=get_txt, timeout=5): return pk, keysize, ktag, seqtlsrpt +def load_pk_from_dns(name, dnsfunc=get_txt, timeout=5): + s = dnsfunc(name, timeout=timeout) + pk, keysize, ktag, seqtlsrpt = evaluate_pk(name, s) + return pk, keysize, ktag, seqtlsrpt + + #: Abstract base class for holding messages and options during DKIM/ARC signing and verification. class DomainSigner(object): # NOTE - the first 2 indentation levels are 2 instead of 4 @@ -676,27 +687,12 @@ class DomainSigner(object): return header_value - # Abstract helper method to verify a signed header - #: @param sig: List of (key, value) tuples containing tag=values of the header - #: @param include_headers: headers to validate b= signature against - #: @param sig_header: (header_name, header_value) - #: @param dnsfunc: interface to dns - def verify_sig(self, sig, include_headers, sig_header, dnsfunc): - name = sig[b's'] + b"._domainkey." + sig[b'd'] + b"." - try: - pk, self.keysize, ktag, self.seqtlsrpt = load_pk_from_dns(name, dnsfunc, - timeout=self.timeout) - except KeyFormatError as e: - self.logger.error("%s" % e) - return False - except binascii.Error as e: - self.logger.error('KeyFormatError: {0}'.format(e)) - return False - + def verify_sig_process(self, sig, include_headers, sig_header, dnsfunc): + """Non-async sensitive verify_sig elements. Separated to avoid async code + duplication.""" # RFC 8460 MAY ignore signatures without tlsrpt Service Type if self.tlsrpt == 'strict' and not self.seqtlsrpt: raise ValidationError("Message is tlsrpt and Service Type is not tlsrpt") - # Inferred requirement from both RFC 8460 and RFC 6376 if not self.tlsrpt and self.seqtlsrpt: raise ValidationError("Message is not tlsrpt and Service Type is tlsrpt") @@ -744,24 +740,43 @@ class DomainSigner(object): if self.debug_content: self.logger.debug("signed for %s: %r" % (sig_header[0], h.hashed())) signature = base64.b64decode(re.sub(br"\s+", b"", sig[b'b'])) - if ktag == b'rsa': + if self.ktag == b'rsa': try: - res = RSASSA_PKCS1_v1_5_verify(h, signature, pk) + res = RSASSA_PKCS1_v1_5_verify(h, signature, self.pk) self.logger.debug("%s valid: %s" % (sig_header[0], res)) if res and self.keysize < self.minkey: raise KeyFormatError("public key too small: %d" % self.keysize) return res except (TypeError,DigestTooLargeError) as e: raise KeyFormatError("digest too large for modulus: %s"%e) - elif ktag == b'ed25519': + elif self.ktag == b'ed25519': try: - pk.verify(h.digest(), signature) + self.pk.verify(h.digest(), signature) self.logger.debug("%s valid" % (sig_header[0])) return True except (nacl.exceptions.BadSignatureError) as e: return False else: - raise UnknownKeyTypeError(ktag) + raise UnknownKeyTypeError(self.ktag) + + + # Abstract helper method to verify a signed header + #: @param sig: List of (key, value) tuples containing tag=values of the header + #: @param include_headers: headers to validate b= signature against + #: @param sig_header: (header_name, header_value) + #: @param dnsfunc: interface to dns + def verify_sig(self, sig, include_headers, sig_header, dnsfunc): + name = sig[b's'] + b"._domainkey." + sig[b'd'] + b"." + try: + self.pk, self.keysize, self.ktag, self.seqtlsrpt = load_pk_from_dns(name, + dnsfunc, timeout=self.timeout) + except KeyFormatError as e: + self.logger.error("%s" % e) + return False + except binascii.Error as e: + self.logger.error('KeyFormatError: {0}'.format(e)) + return False + return self.verify_sig_process(sig, include_headers, sig_header, dnsfunc) #: Hold messages and options during DKIM signing and verification. @@ -881,15 +896,9 @@ class DKIM(DomainSigner): def present(self): return (len([(x,y) for x,y in self.headers if x.lower() == b"dkim-signature"]) > 0) - #: Verify a DKIM signature. - #: @type idx: int - #: @param idx: which signature to verify. The first (topmost) signature is 0. - #: @type dnsfunc: callable - #: @param dnsfunc: an option function to lookup TXT resource records - #: for a DNS domain. The default uses dnspython or pydns. - #: @return: True if signature verifies or False otherwise - #: @raise DKIMException: when the message, signature, or key are badly formed - def verify(self,idx=0,dnsfunc=get_txt): + def verify_headerprep(self, idx=0): + """Non-DNS verify parts to minimize asyncio code duplication.""" + sigheaders = [(x,y) for x,y in self.headers if x.lower() == b"dkim-signature"] if len(sigheaders) <= idx: return False @@ -909,7 +918,18 @@ class DKIM(DomainSigner): include_headers = [x.lower() for x in re.split(br"\s*:\s*", sig[b'h'])] self.include_headers = tuple(include_headers) + return sig, include_headers, sigheaders + #: Verify a DKIM signature. + #: @type idx: int + #: @param idx: which signature to verify. The first (topmost) signature is 0. + #: @type dnsfunc: callable + #: @param dnsfunc: an option function to lookup TXT resource records + #: for a DNS domain. The default uses dnspython or pydns. + #: @return: True if signature verifies or False otherwise + #: @raise DKIMException: when the message, signature, or key are badly formed + def verify(self,idx=0,dnsfunc=get_txt): + sig, include_headers, sigheaders = self.verify_headerprep(idx=0) return self.verify_sig(sig, include_headers, sigheaders[idx], dnsfunc) @@ -1307,7 +1327,8 @@ def sign(message, selector, domain, privkey, identity=None, return d.sign(selector, domain, privkey, identity=identity, canonicalize=canonicalize, include_headers=include_headers, length=length) -def verify(message, logger=None, dnsfunc=get_txt, minkey=1024, timeout=5, tlsrpt=False): +def verify(message, logger=None, dnsfunc=get_txt, minkey=1024, + timeout=5, tlsrpt=False): """Verify the first (topmost) DKIM signature on an RFC822 formatted message. @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings) @param logger: a logger to which debug info will be written (default None) @@ -1326,6 +1347,18 @@ def verify(message, logger=None, dnsfunc=get_txt, minkey=1024, timeout=5, tlsrpt logger.error("%s" % x) return False + +# aiodns requires Python 3.5+, so no async before that +if sys.version_info >= (3, 5): + try: + import aiodns + from dkim.asyncsupport import verify_async + dkim_verify_async = verify_async + except ImportError: + # If aiodns is not installed, then async verification is not available + pass + + # For consistency with ARC dkim_sign = sign dkim_verify = verify diff --git a/dkim/asyncsupport.py b/dkim/asyncsupport.py new file mode 100644 index 0000000..226cc42 --- /dev/null +++ b/dkim/asyncsupport.py @@ -0,0 +1,123 @@ +# This software is provided 'as-is', without any express or implied +# warranty. In no event will the author be held liable for any damages +# arising from the use of this software. +# +# Permission is granted to anyone to use this software for any purpose, +# including commercial applications, and to alter it and redistribute it +# freely, subject to the following restrictions: +# +# 1. The origin of this software must not be misrepresented; you must not +# claim that you wrote the original software. If you use this software +# in a product, an acknowledgment in the product documentation would be +# appreciated but is not required. +# 2. Altered source versions must be plainly marked as such, and must not be +# misrepresented as being the original software. +# 3. This notice may not be removed or altered from any source distribution. +# +# Copyright (c) 2008 Greg Hewgill http://hewgill.com +# +# This has been modified from the original software. +# Copyright (c) 2011 William Grant +# +# This has been modified from the original software. +# Copyright (c) 2016 Google, Inc. +# Contact: Brandon Long +# +# This has been modified from the original software. +# Copyright (c) 2016, 2017, 2018, 2019 Scott Kitterman +# +# This has been modified from the original software. +# Copyright (c) 2017 Valimail Inc +# Contact: Gene Shuman + +import asyncio +import aiodns +import base64 +import dkim +import re + +__all__ = [ + 'get_txt_async', + 'load_pk_from_dns_async', + 'verify_async' + ] + + +async def get_txt_async(name, timeout=5): + """Return a TXT record associated with a DNS name in an asnyc loop. For + DKIM we can assume there is only one.""" + + # Note: This will use the existing loop or create one if needed + loop = asyncio.get_event_loop() + resolver = aiodns.DNSResolver(loop=loop, timeout=timeout) + + async def query(name, qtype): + return await resolver.query(name, qtype) + + #q = query(name, 'TXT') + try: + result = await query(name, 'TXT') + except aiodns.error.DNSError: + result = None + + if result: + return result[0].text + else: + return None + + +async def load_pk_from_dns_async(name, dnsfunc, timeout=5): + s = await dnsfunc(name, timeout=timeout) + pk, keysize, ktag, seqtlsrpt = dkim.evaluate_pk(name, s) + return pk, keysize, ktag, seqtlsrpt + +class DKIM(dkim.DKIM): + #: Sign an RFC822 message and return the DKIM-Signature header line. + #: + #: Identical to dkim.DKIM, except uses aiodns and can be awaited in an + #: ascyncio context. See dkim.DKIM for details. + + # Abstract helper method to verify a signed header + #: @param sig: List of (key, value) tuples containing tag=values of the header + #: @param include_headers: headers to validate b= signature against + #: @param sig_header: (header_name, header_value) + #: @param dnsfunc: interface to dns + async def verify_sig(self, sig, include_headers, sig_header, dnsfunc): + name = sig[b's'] + b"._domainkey." + sig[b'd'] + b"." + try: + self.pk, self.keysize, self.ktag, self.seqtlsrpt = await load_pk_from_dns_async(name, + dnsfunc, timeout=self.timeout) + except dkim.KeyFormatError as e: + self.logger.error("%s" % e) + return False + return self.verify_sig_process(sig, include_headers, sig_header, dnsfunc) + + + async def verify(self,idx=0,dnsfunc=get_txt_async): + sig, include_headers, sigheaders = self.verify_headerprep(idx=0) + return await self.verify_sig(sig, include_headers, sigheaders[idx], dnsfunc) + + +async def verify_async(message, logger=None, dnsfunc=None, minkey=1024, + timeout=5, tlsrpt=False): + """Verify the first (topmost) DKIM signature on an RFC822 formatted message in an asyncio contxt. + @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings) + @param logger: a logger to which debug info will be written (default None) + @param timeout: number of seconds for DNS lookup timeout (default = 5) + @param tlsrpt: message is an RFC 8460 TLS report (default False) + False: Not a tlsrpt, True: Is a tlsrpt, 'strict': tlsrpt, invalid if + service type is missing. For signing, if True, length is never used. + @return: True if signature verifies or False otherwise + """ + # type: (bytes, any, function, int) -> bool + # Note: This will use the existing loop or create one if needed + loop = asyncio.get_event_loop() + if not dnsfunc: + dnsfunc=get_txt_async + d = DKIM(message,logger=logger,minkey=minkey,timeout=timeout,tlsrpt=tlsrpt) + try: + return await d.verify(dnsfunc=dnsfunc) + except dkim.DKIMException as x: + if logger is not None: + logger.error("%s" % x) + return False diff --git a/dkimverify_async.py b/dkimverify_async.py new file mode 100644 index 0000000..a502700 --- /dev/null +++ b/dkimverify_async.py @@ -0,0 +1,48 @@ +#!/usr/bin/env python + +# This software is provided 'as-is', without any express or implied +# warranty. In no event will the author be held liable for any damages +# arising from the use of this software. +# +# Permission is granted to anyone to use this software for any purpose, +# including commercial applications, and to alter it and redistribute it +# freely, subject to the following restrictions: +# +# 1. The origin of this software must not be misrepresented; you must not +# claim that you wrote the original software. If you use this software +# in a product, an acknowledgment in the product documentation would be +# appreciated but is not required. +# 2. Altered source versions must be plainly marked as such, and must not be +# misrepresented as being the original software. +# 3. This notice may not be removed or altered from any source distribution. +# +# Copyright (c) 2008 Greg Hewgill http://hewgill.com +# +# This has been modified from the original software. +# Copyright (c) 2011 William Grant + +from __future__ import print_function + +import sys +import asyncio +import dkim + + +if sys.version_info[0] >= 3: + # Make sys.stdin a binary stream. + sys.stdin = sys.stdin.detach() + +message = sys.stdin.read() + +async def main(): + res = await dkim.verify_async(message) + return res + + +if __name__ == "__main__": + res = asyncio.run(main()) + if not res: + print("signature verification failed") + sys.exit(1) + print("signature ok") + diff --git a/setup.py b/setup.py index 752e168..29595f2 100644 --- a/setup.py +++ b/setup.py @@ -86,7 +86,8 @@ verification.""", 'pynacl', ], 'ed25519': ['pynacl'], - 'ARC': ['authres'] + 'ARC': ['authres'], + 'asyncio': ['aiodns'] }, **kw )