# Copyright (C) 2001,2002 Python Software Foundation # Author: barry@zope.com (Barry Warsaw) """A parser of RFC 2822 and MIME email messages. """ import re from cStringIO import StringIO from types import ListType from email import Errors from email import Message EMPTYSTRING = '' NL = '\n' try: True, False except NameError: True = 1 False = 0 NLCRE = re.compile('\r\n|\r|\n') class TextUtil: """ A utility class for wrapping a file object and providing a couple of additional useful functions. """ def __init__(self, fp): self.fp = fp self.unread = [] def readline(self): """ Return a line of data. If data has been pushed back with unreadline(), the most recently returned unreadline()d data will be returned. """ if self.unread: return self.unread.pop() else: return self.fp.readline() def unreadline(self, line): """Push a line back into the object. """ self.unread.append(line) def peekline(self): """Non-destructively look at the next line""" line = self.readline() self.unreadline(line) return line def read(self): """Return the remaining data """ r = self.fp.read() if self.unread: r = "\n".join(self.unread) + r self.unread = [] return r def readuntil(self, re, afterblank=0, includematch=0): """Read a line at a time until we get the specified RE. Returns the text up to (and including, if includematch is true) the matched text, and the RE match object. If afterblank is true, there must be a blank line before the matched text. Moves current filepointer to the line following the matched line. If we reach end-of-file, return what we've got so far, and return None as the RE match object. """ prematch = [] blankseen = 0 while 1: line = self.readline() if not line: # end of file return EMPTYSTRING.join(prematch), None if afterblank: if NLCRE.match(line): blankseen = 1 continue else: blankseen = 0 m = re.match(line) if (m and not afterblank) or (m and afterblank and blankseen): if includematch: prematch.append(line) return EMPTYSTRING.join(prematch), m prematch.append(line) class Parser: def __init__(self, _class=Message.Message, strict=False): """Parser of RFC 2822 and MIME email messages. Creates an in-memory object tree representing the email message, which can then be manipulated and turned over to a Generator to return the textual representation of the message. The string must be formatted as a block of RFC 2822 headers and header continuation lines, optionally preceeded by a `Unix-from' header. The header block is terminated either by the end of the string or by a blank line. _class is the class to instantiate for new message objects when they must be created. This class must have a constructor that can take zero arguments. Default is Message.Message. Optional strict tells the parser to be strictly RFC compliant or to be more forgiving in parsing of ill-formatted MIME documents. When non-strict mode is used, the parser will try to make up for missing or erroneous boundaries and other peculiarities seen in the wild. Default is non-strict parsing. """ self._class = _class self._strict = strict def parse(self, fp, headersonly=False): """Create a message structure from the data in a file. Reads all the data from the file and returns the root of the message structure. Optional headersonly is a flag specifying whether to stop parsing after reading the headers or not. The default is False, meaning it parses the entire contents of the file. """ root = self._class() fp = TextUtil(fp) self._parseheaders(root, fp) if not headersonly: obj = self._parsemessage(root, fp) trailer = fp.read() if obj and trailer: self._attach_trailer(obj, trailer) return root def parsestr(self, text, headersonly=False): """Create a message structure from a string. Returns the root of the message structure. Optional headersonly is a flag specifying whether to stop parsing after reading the headers or not. The default is False, meaning it parses the entire contents of the file. """ return self.parse(StringIO(text), headersonly=headersonly) def _parseheaders(self, container, fp): # Parse the headers, returning a list of header/value pairs. None as # the header means the Unix-From header. lastheader = '' lastvalue = [] lineno = 0 while True: # Don't strip the line before we test for the end condition, # because whitespace-only header lines are RFC compliant # continuation lines. line = fp.readline() if not line: break line = line.splitlines()[0] if not line: break # Ignore the trailing newline lineno += 1 # Check for initial Unix From_ line if line.startswith('From '): if lineno == 1: container.set_unixfrom(line) continue elif self._strict: raise Errors.HeaderParseError( 'Unix-from in headers after first rfc822 header') else: # ignore the wierdly placed From_ line # XXX: maybe set unixfrom anyway? or only if not already? continue # Header continuation line if line[0] in ' \t': if not lastheader: raise Errors.HeaderParseError( 'Continuation line seen before first header') lastvalue.append(line) continue # Normal, non-continuation header. BAW: this should check to make # sure it's a legal header, e.g. doesn't contain spaces. Also, we # should expose the header matching algorithm in the API, and # allow for a non-strict parsing mode (that ignores the line # instead of raising the exception). i = line.find(':') if i < 0: if self._strict: raise Errors.HeaderParseError( "Not a header, not a continuation: ``%s''" % line) elif lineno == 1 and line.startswith('--'): # allow through duplicate boundary tags. continue else: # There was no separating blank line as mandated by RFC # 2822, but we're in non-strict mode. So just offer up # this current line as the first body line. fp.unreadline(line) break if lastheader: container[lastheader] = NL.join(lastvalue) lastheader = line[:i] lastvalue = [line[i+1:].lstrip()] # Make sure we retain the last header if lastheader: container[lastheader] = NL.join(lastvalue) return def _parsemessage(self, container, fp): # Parse the body. We walk through the body from top to bottom, # keeping track of the current multipart nesting as we go. # We return the object that gets the data at the end of this # block. boundary = container.get_boundary() isdigest = (container.get_content_type() == 'multipart/digest') if boundary: separator = '--' + boundary boundaryRE = re.compile( r'(?P' + re.escape(separator) + r')(?P--)?(?P[ \t]*)(?P\r\n|\r|\n)$') preamble, matchobj = fp.readuntil(boundaryRE) if not matchobj: # Broken - we hit the end of file. Just set the body # to the text. container.set_payload(preamble) return container if preamble: container.preamble = preamble else: # The module docs specify an empty preamble is None, not '' container.preamble = None while 1: subobj = self._class() if isdigest: subobj.set_default_type('message/rfc822') firstline = fp.peekline() if firstline.strip(): # we have MIME headers. all good. self._parseheaders(subobj, fp) else: # no MIME headers. this is allowed for multipart/digest # Consume the extra blank line fp.readline() pass else: self._parseheaders(subobj, fp) container.attach(subobj) maintype = subobj.get_content_maintype() hassubparts = (subobj.get_content_maintype() in ( "message", "multipart" )) if hassubparts: subobj = self._parsemessage(subobj, fp) trailer, matchobj = fp.readuntil(boundaryRE) if matchobj is None or trailer: mo = re.search('(?P\r\n|\r|\n){2}$', trailer) if not mo: mo = re.search('(?P\r\n|\r|\n)$', trailer) if not mo: raise Errors.BoundaryError( 'No terminating boundary and no trailing empty line') linesep = mo.group('sep') trailer = trailer[:-len(linesep)] if trailer: self._attach_trailer(subobj, trailer) if matchobj is None or matchobj.group('end'): # That was the last piece of data. Let our caller attach # the epilogue to us. But before we do that, push the # line ending of the match group back into the readline # buffer, as it's part of the epilogue. if matchobj: fp.unreadline(matchobj.group('linesep')) return container elif container.get_content_maintype() == "multipart": # Very bad. A message is a multipart with no boundary! raise Errors.BoundaryError( 'multipart message with no defined boundary') elif container.get_content_maintype() == "message": ct = container.get_content_type() if ct == "message/rfc822": submessage = self._class() self._parseheaders(submessage, fp) self._parsemessage(submessage, fp) container.attach(submessage) return submessage elif ct == "message/delivery-status": # This special kind of type contains blocks of headers # separated by a blank line. We'll represent each header # block as a separate Message object while 1: nextblock = self._class() self._parseheaders(nextblock, fp) container.attach(nextblock) # next peek ahead to see whether we've hit the end or not nextline = fp.peekline() if nextline[:2] == "--": break return container else: # Other sort of message object (e.g. external-body) msg = self._class() self._parsemessage(msg, fp) container.attach(msg) return msg else: # single body section. We let our caller set the payload. return container def _attach_trailer(self, obj, trailer): if obj.get_content_maintype() in ("message", "multipart"): obj.epilogue = trailer else: obj.set_payload(trailer) class HeaderParser(Parser): """A subclass of Parser, this one only meaningfully parses message headers. This class can be used if all you're interested in is the headers of a message. While it consumes the message body, it does not parse it, but simply makes it available as a string payload. Parsing with this subclass can be considerably faster if all you're interested in is the message headers. """ def _parsemessage(self, container, fp): # Consume but do not parse, the body text = fp.read() container.set_payload(text) return None