Source Code for Module dkim.asyncsupport

  1  # This software is provided 'as-is', without any express or implied 
  2  # warranty.  In no event will the author be held liable for any damages 
  3  # arising from the use of this software. 
  4  # 
  5  # Permission is granted to anyone to use this software for any purpose, 
  6  # including commercial applications, and to alter it and redistribute it 
  7  # freely, subject to the following restrictions: 
  8  # 
  9  # 1. The origin of this software must not be misrepresented; you must not 
 10  #    claim that you wrote the original software. If you use this software 
 11  #    in a product, an acknowledgment in the product documentation would be 
 12  #    appreciated but is not required. 
 13  # 2. Altered source versions must be plainly marked as such, and must not be 
 14  #    misrepresented as being the original software. 
 15  # 3. This notice may not be removed or altered from any source distribution. 
 16  # 
 17  # Copyright (c) 2008 Greg Hewgill http://hewgill.com 
 18  # 
 19  # This has been modified from the original software. 
 20  # Copyright (c) 2011 William Grant <me@williamgrant.id.au> 
 21  # 
 22  # This has been modified from the original software. 
 23  # Copyright (c) 2016 Google, Inc. 
 24  # Contact: Brandon Long <blong@google.com> 
 25  # 
 26  # This has been modified from the original software. 
 27  # Copyright (c) 2016, 2017, 2018, 2019 Scott Kitterman <scott@kitterman.com> 
 28  # 
 29  # This has been modified from the original software. 
 30  # Copyright (c) 2017 Valimail Inc 
 31  # Contact: Gene Shuman <gene@valimail.com> 
 32   
 33  import asyncio 
 34  import aiodns 
 35  import base64 
 36  import dkim 
 37  import re 
 38   
 39  __all__ = [ 
 40      'get_txt_async', 
 41      'load_pk_from_dns_async', 
 42      'verify_async' 
 43      ] 
 44   
 45   
 46 -async def get_txt_async(name, timeout=5): 
 47      """Return a TXT record associated with a DNS name in an asnyc loop. For 
 48      DKIM we can assume there is only one.""" 
 49   
 50      # Note: This will use the existing loop or create one if needed 
 51      loop = asyncio.get_event_loop() 
 52      resolver = aiodns.DNSResolver(loop=loop, timeout=timeout) 
 53   
 54      async def query(name, qtype): 
 55          return await resolver.query(name, qtype) 
 56   
 57      #q = query(name, 'TXT') 
 58      try: 
 59          result = await query(name, 'TXT') 
 60      except aiodns.error.DNSError: 
 61          result = None 
 62   
 63      if result: 
 64          return result[0].text 
 65      else: 
 66          return None 
 67   
 68   
 69 -async def load_pk_from_dns_async(name, dnsfunc, timeout=5): 
 70    s = await dnsfunc(name, timeout=timeout) 
 71    pk, keysize, ktag, seqtlsrpt = dkim.evaluate_pk(name, s) 
 72    return pk, keysize, ktag, seqtlsrpt 
 73   
 74 -class DKIM(dkim.DKIM): 
 75    #: Sign an RFC822 message and return the DKIM-Signature header line. 
 76    #: 
 77    #: Identical to dkim.DKIM, except uses aiodns and can be awaited in an 
 78    #: ascyncio context.  See dkim.DKIM for details. 
 79   
 80    # Abstract helper method to verify a signed header 
 81    #: @param sig: List of (key, value) tuples containing tag=values of the header 
 82    #: @param include_headers: headers to validate b= signature against 
 83    #: @param sig_header: (header_name, header_value) 
 84    #: @param dnsfunc: interface to dns 
 85 -  async def verify_sig(self, sig, include_headers, sig_header, dnsfunc): 
 86      name = sig[b's'] + b"._domainkey." + sig[b'd'] + b"." 
 87      try: 
 88        self.pk, self.keysize, self.ktag, self.seqtlsrpt = await load_pk_from_dns_async(name, 
 89                dnsfunc, timeout=self.timeout) 
 90      except dkim.KeyFormatError as e: 
 91        self.logger.error("%s" % e) 
 92        return False 
 93      return self.verify_sig_process(sig, include_headers, sig_header, dnsfunc) 
 94   
 95   
 96 -  async def verify(self,idx=0,dnsfunc=get_txt_async): 
 97      sig, include_headers, sigheaders = self.verify_headerprep(idx=0) 
 98      return await self.verify_sig(sig, include_headers, sigheaders[idx], dnsfunc) 
 99   
100   
101 -async def verify_async(message, logger=None, dnsfunc=None, minkey=1024, 
102          timeout=5, tlsrpt=False): 
103      """Verify the first (topmost) DKIM signature on an RFC822 formatted message in an asyncio contxt. 
104      @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings) 
105      @param logger: a logger to which debug info will be written (default None) 
106      @param timeout: number of seconds for DNS lookup timeout (default = 5) 
107      @param tlsrpt: message is an RFC 8460 TLS report (default False) 
108      False: Not a tlsrpt, True: Is a tlsrpt, 'strict': tlsrpt, invalid if 
109      service type is missing. For signing, if True, length is never used. 
110      @return: True if signature verifies or False otherwise 
111      """ 
112      # type: (bytes, any, function, int) -> bool 
113      # Note: This will use the existing loop or create one if needed 
114      loop = asyncio.get_event_loop() 
115      if not dnsfunc: 
116          dnsfunc=get_txt_async 
117      d = DKIM(message,logger=logger,minkey=minkey,timeout=timeout,tlsrpt=tlsrpt) 
118      try: 
119          return await d.verify(dnsfunc=dnsfunc) 
120      except dkim.DKIMException as x: 
121          if logger is not None: 
122              logger.error("%s" % x) 
123          return False 
124