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274 lines
12 KiB
Python
274 lines
12 KiB
Python
# Copyright (C) 2001,2002 Python Software Foundation
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# Author: barry@zope.com (Barry Warsaw)
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"""A parser of RFC 2822 and MIME email messages.
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"""
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import re
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from cStringIO import StringIO
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from types import ListType
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from email import Errors
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from email import Message
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EMPTYSTRING = ''
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NL = '\n'
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try:
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True, False
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except NameError:
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True = 1
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False = 0
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class Parser:
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def __init__(self, _class=Message.Message, strict=False):
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"""Parser of RFC 2822 and MIME email messages.
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Creates an in-memory object tree representing the email message, which
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can then be manipulated and turned over to a Generator to return the
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textual representation of the message.
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The string must be formatted as a block of RFC 2822 headers and header
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continuation lines, optionally preceeded by a `Unix-from' header. The
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header block is terminated either by the end of the string or by a
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blank line.
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_class is the class to instantiate for new message objects when they
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must be created. This class must have a constructor that can take
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zero arguments. Default is Message.Message.
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Optional strict tells the parser to be strictly RFC compliant or to be
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more forgiving in parsing of ill-formatted MIME documents. When
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non-strict mode is used, the parser will try to make up for missing or
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erroneous boundaries and other peculiarities seen in the wild.
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Default is non-strict parsing.
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"""
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self._class = _class
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self._strict = strict
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def parse(self, fp, headersonly=False):
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"""Create a message structure from the data in a file.
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Reads all the data from the file and returns the root of the message
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structure. Optional headersonly is a flag specifying whether to stop
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parsing after reading the headers or not. The default is False,
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meaning it parses the entire contents of the file.
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"""
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root = self._class()
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self._parseheaders(root, fp)
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if not headersonly:
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self._parsebody(root, fp)
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return root
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def parsestr(self, text, headersonly=False):
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"""Create a message structure from a string.
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Returns the root of the message structure. Optional headersonly is a
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flag specifying whether to stop parsing after reading the headers or
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not. The default is False, meaning it parses the entire contents of
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the file.
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"""
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return self.parse(StringIO(text), headersonly=headersonly)
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def _parseheaders(self, container, fp):
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# Parse the headers, returning a list of header/value pairs. None as
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# the header means the Unix-From header.
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lastheader = ''
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lastvalue = []
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lineno = 0
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while True:
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# Don't strip the line before we test for the end condition,
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# because whitespace-only header lines are RFC compliant
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# continuation lines.
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line = fp.readline()
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if not line:
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break
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line = line.splitlines()[0]
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if not line:
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break
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# Ignore the trailing newline
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lineno += 1
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# Check for initial Unix From_ line
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if line.startswith('From '):
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if lineno == 1:
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container.set_unixfrom(line)
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continue
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elif self._strict:
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raise Errors.HeaderParseError(
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'Unix-from in headers after first rfc822 header')
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else:
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# ignore the wierdly placed From_ line
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# XXX: maybe set unixfrom anyway? or only if not already?
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continue
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# Header continuation line
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if line[0] in ' \t':
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if not lastheader:
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raise Errors.HeaderParseError(
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'Continuation line seen before first header')
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lastvalue.append(line)
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continue
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# Normal, non-continuation header. BAW: this should check to make
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# sure it's a legal header, e.g. doesn't contain spaces. Also, we
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# should expose the header matching algorithm in the API, and
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# allow for a non-strict parsing mode (that ignores the line
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# instead of raising the exception).
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i = line.find(':')
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if i < 0:
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if self._strict:
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raise Errors.HeaderParseError(
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"Not a header, not a continuation: ``%s''"%line)
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elif lineno == 1 and line.startswith('--'):
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# allow through duplicate boundary tags.
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continue
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else:
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raise Errors.HeaderParseError(
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"Not a header, not a continuation: ``%s''"%line)
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if lastheader:
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container[lastheader] = NL.join(lastvalue)
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lastheader = line[:i]
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lastvalue = [line[i+1:].lstrip()]
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# Make sure we retain the last header
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if lastheader:
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container[lastheader] = NL.join(lastvalue)
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def _parsebody(self, container, fp):
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# Parse the body, but first split the payload on the content-type
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# boundary if present.
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boundary = container.get_boundary()
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isdigest = (container.get_type() == 'multipart/digest')
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# If there's a boundary, split the payload text into its constituent
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# parts and parse each separately. Otherwise, just parse the rest of
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# the body as a single message. Note: any exceptions raised in the
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# recursive parse need to have their line numbers coerced.
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if boundary:
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preamble = epilogue = None
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# Split into subparts. The first boundary we're looking for won't
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# always have a leading newline since we're at the start of the
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# body text, and there's not always a preamble before the first
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# boundary.
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separator = '--' + boundary
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payload = fp.read()
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# We use an RE here because boundaries can have trailing
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# whitespace.
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mo = re.search(
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r'(?P<sep>' + re.escape(separator) + r')(?P<ws>[ \t]*)',
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payload)
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if not mo:
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if self._strict:
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raise Errors.BoundaryError(
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"Couldn't find starting boundary: %s" % boundary)
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container.set_payload(payload)
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return
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start = mo.start()
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if start > 0:
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# there's some pre-MIME boundary preamble
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preamble = payload[0:start]
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# Find out what kind of line endings we're using
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start += len(mo.group('sep')) + len(mo.group('ws'))
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cre = re.compile('\r\n|\r|\n')
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mo = cre.search(payload, start)
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if mo:
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start += len(mo.group(0))
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# We create a compiled regexp first because we need to be able to
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# specify the start position, and the module function doesn't
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# support this signature. :(
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cre = re.compile('(?P<sep>\r\n|\r|\n)' +
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re.escape(separator) + '--')
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mo = cre.search(payload, start)
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if mo:
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terminator = mo.start()
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linesep = mo.group('sep')
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if mo.end() < len(payload):
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# There's some post-MIME boundary epilogue
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epilogue = payload[mo.end():]
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elif self._strict:
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raise Errors.BoundaryError(
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"Couldn't find terminating boundary: %s" % boundary)
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else:
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# Handle the case of no trailing boundary. Check that it ends
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# in a blank line. Some cases (spamspamspam) don't even have
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# that!
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mo = re.search('(?P<sep>\r\n|\r|\n){2}$', payload)
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if not mo:
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mo = re.search('(?P<sep>\r\n|\r|\n)$', payload)
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if not mo:
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raise Errors.BoundaryError(
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'No terminating boundary and no trailing empty line')
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linesep = mo.group('sep')
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terminator = len(payload)
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# We split the textual payload on the boundary separator, which
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# includes the trailing newline. If the container is a
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# multipart/digest then the subparts are by default message/rfc822
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# instead of text/plain. In that case, they'll have a optional
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# block of MIME headers, then an empty line followed by the
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# message headers.
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parts = re.split(
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linesep + re.escape(separator) + r'[ \t]*' + linesep,
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payload[start:terminator])
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for part in parts:
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if isdigest:
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if part[0] == linesep:
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# There's no header block so create an empty message
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# object as the container, and lop off the newline so
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# we can parse the sub-subobject
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msgobj = self._class()
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part = part[1:]
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else:
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parthdrs, part = part.split(linesep+linesep, 1)
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# msgobj in this case is the "message/rfc822" container
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msgobj = self.parsestr(parthdrs, headersonly=1)
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# while submsgobj is the message itself
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submsgobj = self.parsestr(part)
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msgobj.attach(submsgobj)
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msgobj.set_default_type('message/rfc822')
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else:
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msgobj = self.parsestr(part)
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container.preamble = preamble
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container.epilogue = epilogue
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container.attach(msgobj)
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elif container.get_main_type() == 'multipart':
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# Very bad. A message is a multipart with no boundary!
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raise Errors.BoundaryError(
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'multipart message with no defined boundary')
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elif container.get_type() == 'message/delivery-status':
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# This special kind of type contains blocks of headers separated
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# by a blank line. We'll represent each header block as a
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# separate Message object
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blocks = []
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while True:
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blockmsg = self._class()
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self._parseheaders(blockmsg, fp)
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if not len(blockmsg):
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# No more header blocks left
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break
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blocks.append(blockmsg)
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container.set_payload(blocks)
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elif container.get_main_type() == 'message':
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# Create a container for the payload, but watch out for there not
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# being any headers left
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try:
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msg = self.parse(fp)
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except Errors.HeaderParseError:
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msg = self._class()
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self._parsebody(msg, fp)
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container.attach(msg)
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else:
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container.set_payload(fp.read())
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class HeaderParser(Parser):
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"""A subclass of Parser, this one only meaningfully parses message headers.
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This class can be used if all you're interested in is the headers of a
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message. While it consumes the message body, it does not parse it, but
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simply makes it available as a string payload.
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Parsing with this subclass can be considerably faster if all you're
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interested in is the message headers.
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"""
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def _parsebody(self, container, fp):
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# Consume but do not parse, the body
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container.set_payload(fp.read())
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