721 lines
25 KiB
Python
721 lines
25 KiB
Python
#!/usr/bin/env python
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import sys
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import re
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import md5
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import struct
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from sys import stderr
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from utils import choplist
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from utils import nunpack
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from utils import decode_text
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from arcfour import Arcfour
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from psparser import PSStackParser
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from psparser import PSSyntaxError
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from psparser import PSEOF
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from psparser import PSLiteralTable
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from psparser import PSKeywordTable
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from psparser import literal_name
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from psparser import keyword_name
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from psparser import STRICT
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from pdftypes import PDFException
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from pdftypes import PDFTypeError
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from pdftypes import PDFNotImplementedError
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from pdftypes import PDFStream
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from pdftypes import PDFObjRef
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from pdftypes import resolve1
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from pdftypes import decipher_all
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from pdftypes import int_value
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from pdftypes import float_value
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from pdftypes import num_value
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from pdftypes import str_value
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from pdftypes import list_value
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from pdftypes import dict_value
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from pdftypes import stream_value
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## Exceptions
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##
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class PDFSyntaxError(PDFException): pass
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class PDFNoValidXRef(PDFSyntaxError): pass
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class PDFEncryptionError(PDFException): pass
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class PDFPasswordIncorrect(PDFEncryptionError): pass
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# some predefined literals and keywords.
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LITERAL_OBJSTM = PSLiteralTable.intern('ObjStm')
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LITERAL_XREF = PSLiteralTable.intern('XRef')
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LITERAL_PAGE = PSLiteralTable.intern('Page')
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LITERAL_PAGES = PSLiteralTable.intern('Pages')
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LITERAL_CATALOG = PSLiteralTable.intern('Catalog')
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## XRefs
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##
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class XRefObjRange(object):
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def __init__(self, start, nobjs):
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self.start = start
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self.nobjs = nobjs
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return
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def __repr__(self):
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return '<XRefObjRange: %d-%d>' % (self.get_start_id(), self.get_end_id())
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def get_start_id(self):
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return self.start
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def get_end_id(self):
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return self.start + self.nobjs - 1
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def get_nobjs(self):
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return self.nobjs
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class PDFBaseXRef(object):
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def __init__(self):
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self.objid_ranges = None
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return
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def objids(self):
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if self.objid_ranges:
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for objid_range in self.objid_ranges:
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for objid in xrange(objid_range.get_start_id(), objid_range.get_end_id() + 1):
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yield objid
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return
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## PDFXRef
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##
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class PDFXRef(PDFBaseXRef):
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def __init__(self):
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PDFBaseXRef.__init__(self)
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self.offsets = None
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self.trailer = {}
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return
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def __repr__(self):
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return '<PDFXRef: objs=%d>' % len(self.offsets)
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def load(self, parser, debug=0):
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self.offsets = {}
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self.objid_ranges = []
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while 1:
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try:
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(pos, line) = parser.nextline()
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if not line.strip():
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continue
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except PSEOF:
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raise PDFNoValidXRef('Unexpected EOF - file corrupted?')
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if not line:
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raise PDFNoValidXRef('Premature eof: %r' % parser)
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if line.startswith('trailer'):
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parser.seek(pos)
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break
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f = line.strip().split(' ')
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if len(f) != 2:
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raise PDFNoValidXRef('Trailer not found: %r: line=%r' % (parser, line))
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try:
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(start, nobjs) = map(long, f)
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except ValueError:
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raise PDFNoValidXRef('Invalid line: %r: line=%r' % (parser, line))
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self.newoffsets = {}
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self.objid_ranges.append(XRefObjRange(start, nobjs))
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for objid in xrange(start, start+nobjs):
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try:
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(_, line) = parser.nextline()
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except PSEOF:
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raise PDFNoValidXRef('Unexpected EOF - file corrupted?')
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f = line.strip().split(' ')
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if len(f) != 3:
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raise PDFNoValidXRef('Invalid XRef format: %r, line=%r' % (parser, line))
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(pos, genno, use) = f
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if use != 'n': continue
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self.offsets[objid] = (int(genno), long(pos))
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if debug:
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print >>stderr, 'xref objects:', self.offsets
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self.load_trailer(parser)
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return
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KEYWORD_TRAILER = PSKeywordTable.intern('trailer')
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def load_trailer(self, parser):
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try:
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(_,kwd) = parser.nexttoken()
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assert kwd is self.KEYWORD_TRAILER
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(_,dic) = parser.nextobject()
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except PSEOF:
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x = parser.pop(1)
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if not x:
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raise PDFNoValidXRef('Unexpected EOF - file corrupted')
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(_,dic) = x[0]
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self.trailer.update( dict_value(dic))
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return
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def getpos(self, objid):
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try:
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(genno, pos) = self.offsets[objid]
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except KeyError:
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raise
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return (None, pos)
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## PDFXRefStream
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##
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class PDFXRefStream(PDFBaseXRef):
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def __init__(self):
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PDFBaseXRef.__init__(self)
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self.data = None
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self.entlen = None
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self.fl1 = self.fl2 = self.fl3 = None
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return
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def __repr__(self):
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return '<PDFXRefStream: fields=%d,%d,%d>' % (self.fl1, self.fl2, self.fl3)
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def load(self, parser, debug=0):
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(_,objid) = parser.nexttoken() # ignored
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(_,genno) = parser.nexttoken() # ignored
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(_,kwd) = parser.nexttoken()
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(_,stream) = parser.nextobject()
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if not isinstance(stream, PDFStream) or stream.dic['Type'] is not LITERAL_XREF:
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raise PDFNoValidXRef('Invalid PDF stream spec.')
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size = stream.dic['Size']
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index_array = stream.dic.get('Index', (0,size))
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if len(index_array) % 2 != 0:
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raise PDFSyntaxError('Invalid index number')
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self.objid_ranges = [ XRefObjRange(start,nobjs) for (start,nobjs) in choplist(2, index_array) ]
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(self.fl1, self.fl2, self.fl3) = stream.dic['W']
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self.data = stream.get_data()
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self.entlen = self.fl1+self.fl2+self.fl3
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self.trailer = stream.dic
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if debug:
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print >>stderr, ('xref stream: objid=%s, fields=%d,%d,%d' %
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(', '.join(map(repr, self.objid_ranges), self.fl1, self.fl2, self.fl3)))
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return
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def getpos(self, objid):
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offset = 0
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found = False
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for objid_range in self.objid_ranges:
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if objid >= objid_range.get_start_id() and objid <= objid_range.get_end_id():
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offset += objid - objid_range.get_start_id()
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found = True
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break
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else:
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offset += objid_range.get_nobjs()
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if not found: raise KeyError(objid)
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i = self.entlen * offset
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ent = self.data[i:i+self.entlen]
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f1 = nunpack(ent[:self.fl1], 1)
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if f1 == 1:
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pos = nunpack(ent[self.fl1:self.fl1+self.fl2])
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genno = nunpack(ent[self.fl1+self.fl2:])
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return (None, pos)
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elif f1 == 2:
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objid = nunpack(ent[self.fl1:self.fl1+self.fl2])
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index = nunpack(ent[self.fl1+self.fl2:])
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return (objid, index)
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# this is a free object
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raise KeyError(objid)
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## PDFPage
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##
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## A PDFPage object is nothing more than a bunch of keys and values
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## that describe the properties of the page and point to its contents,
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## and has nothing to do with a real graphical entity. For a real graphical
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## object, look at layout.LTPage.
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##
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class PDFPage(object):
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def __init__(self, doc, pageid, attrs):
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self.doc = doc
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self.pageid = pageid
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self.attrs = dict_value(attrs)
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self.lastmod = resolve1(self.attrs.get('LastModified'))
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self.resources = resolve1(self.attrs['Resources'])
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self.mediabox = resolve1(self.attrs['MediaBox'])
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if 'CropBox' in self.attrs:
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self.cropbox = resolve1(self.attrs['CropBox'])
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else:
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self.cropbox = self.mediabox
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self.rotate = self.attrs.get('Rotate', 0)
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self.annots = self.attrs.get('Annots')
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self.beads = self.attrs.get('B')
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if 'Contents' in self.attrs:
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contents = resolve1(self.attrs['Contents'])
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else:
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contents = []
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if not isinstance(contents, list):
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contents = [ contents ]
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self.contents = contents
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return
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def __repr__(self):
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return '<PDFPage: Resources=%r, MediaBox=%r>' % (self.resources, self.mediabox)
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## PDFDocument
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##
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## A PDFDocument object represents a PDF document.
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## Since a PDF file is usually pretty big, normally it is not loaded
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## at once. Rather it is parsed dynamically as processing goes.
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## A PDF parser is associated with the document.
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##
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class PDFDocument(object):
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debug = 0
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def __init__(self):
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self.xrefs = []
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self.objs = {}
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self.parsed_objs = {}
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self.root = None
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self.catalog = None
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self.parser = None
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self.encryption = None
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self.decipher = None
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self.ready = False
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return
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# set_parser(parser)
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# Associates the document with an (already initialized) parser object.
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def set_parser(self, parser):
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if self.parser: return
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self.parser = parser
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# The document is set to be temporarily ready during collecting
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# all the basic information about the document, e.g.
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# the header, the encryption information, and the access rights
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# for the document.
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self.ready = True
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# Retrieve the information of each header that was appended
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# (maybe multiple times) at the end of the document.
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self.xrefs = parser.read_xref()
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for xref in self.xrefs:
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trailer = xref.trailer
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if not trailer: continue
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# If there's an encryption info, remember it.
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if 'Encrypt' in trailer:
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#assert not self.encryption
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self.encryption = (list_value(trailer['ID']),
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dict_value(trailer['Encrypt']))
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if 'Root' in trailer:
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self.set_root(dict_value(trailer['Root']))
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break
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else:
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raise PDFSyntaxError('No /Root object! - Is this really a PDF?')
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# The document is set to be non-ready again, until all the
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# proper initialization (asking the password key and
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# verifying the access permission, so on) is finished.
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self.ready = False
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return
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# set_root(root)
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# Set the Root dictionary of the document.
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# Each PDF file must have exactly one /Root dictionary.
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def set_root(self, root):
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self.root = root
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self.catalog = dict_value(self.root)
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if self.catalog.get('Type') is not LITERAL_CATALOG:
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if STRICT:
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raise PDFSyntaxError('Catalog not found!')
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return
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# initialize(password='')
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# Perform the initialization with a given password.
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# This step is mandatory even if there's no password associated
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# with the document.
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PASSWORD_PADDING = '(\xbfN^Nu\x8aAd\x00NV\xff\xfa\x01\x08..\x00\xb6\xd0h>\x80/\x0c\xa9\xfedSiz'
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def initialize(self, password=''):
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if not self.encryption:
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self.is_printable = self.is_modifiable = self.is_extractable = True
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self.ready = True
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return
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(docid, param) = self.encryption
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if literal_name(param['Filter']) != 'Standard':
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raise PDFEncryptionError('Unknown filter: param=%r' % param)
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V = int_value(param.get('V', 0))
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if not (V == 1 or V == 2):
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raise PDFEncryptionError('Unknown algorithm: param=%r' % param)
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length = int_value(param.get('Length', 40)) # Key length (bits)
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O = str_value(param['O'])
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R = int_value(param['R']) # Revision
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if 5 <= R:
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raise PDFEncryptionError('Unknown revision: %r' % R)
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U = str_value(param['U'])
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P = int_value(param['P'])
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self.is_printable = bool(P & 4)
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self.is_modifiable = bool(P & 8)
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self.is_extractable = bool(P & 16)
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# Algorithm 3.2
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password = (password+self.PASSWORD_PADDING)[:32] # 1
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hash = md5.md5(password) # 2
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hash.update(O) # 3
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hash.update(struct.pack('<l', P)) # 4
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hash.update(docid[0]) # 5
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if 4 <= R:
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# 6
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raise PDFNotImplementedError('Revision 4 encryption is currently unsupported')
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if 3 <= R:
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# 8
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for _ in xrange(50):
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hash = md5.md5(hash.digest()[:length/8])
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key = hash.digest()[:length/8]
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if R == 2:
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# Algorithm 3.4
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u1 = Arcfour(key).process(self.PASSWORD_PADDING)
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elif R == 3:
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# Algorithm 3.5
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hash = md5.md5(self.PASSWORD_PADDING) # 2
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hash.update(docid[0]) # 3
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x = Arcfour(key).process(hash.digest()[:16]) # 4
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for i in xrange(1,19+1):
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k = ''.join( chr(ord(c) ^ i) for c in key )
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x = Arcfour(k).process(x)
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u1 = x+x # 32bytes total
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if R == 2:
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is_authenticated = (u1 == U)
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else:
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is_authenticated = (u1[:16] == U[:16])
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if not is_authenticated:
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raise PDFPasswordIncorrect
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self.decrypt_key = key
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self.decipher = self.decrypt_rc4 # XXX may be AES
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self.ready = True
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return
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def decrypt_rc4(self, objid, genno, data):
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key = self.decrypt_key + struct.pack('<L',objid)[:3]+struct.pack('<L',genno)[:2]
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hash = md5.md5(key)
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key = hash.digest()[:min(len(key),16)]
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return Arcfour(key).process(data)
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KEYWORD_OBJ = PSKeywordTable.intern('obj')
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def getobj(self, objid):
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if not self.ready:
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raise PDFException('PDFDocument not initialized')
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#assert self.xrefs
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if 2 <= self.debug:
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print >>stderr, 'getobj: objid=%r' % (objid)
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if objid in self.objs:
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genno = 0
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obj = self.objs[objid]
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else:
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for xref in self.xrefs:
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try:
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(strmid, index) = xref.getpos(objid)
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break
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except KeyError:
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pass
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else:
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if STRICT:
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raise PDFSyntaxError('Cannot locate objid=%r' % objid)
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return None
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if strmid:
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stream = stream_value(self.getobj(strmid))
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if stream.dic.get('Type') is not LITERAL_OBJSTM:
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if STRICT:
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raise PDFSyntaxError('Not a stream object: %r' % stream)
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try:
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n = stream.dic['N']
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except KeyError:
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if STRICT:
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raise PDFSyntaxError('N is not defined: %r' % stream)
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n = 0
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if strmid in self.parsed_objs:
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objs = self.parsed_objs[strmid]
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else:
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parser = PDFObjStrmParser(self, stream.get_data())
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objs = []
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try:
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while 1:
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(_,obj) = parser.nextobject()
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objs.append(obj)
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except PSEOF:
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pass
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self.parsed_objs[strmid] = objs
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genno = 0
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i = n*2+index
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try:
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obj = objs[i]
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except IndexError:
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raise PDFSyntaxError('Invalid object number: objid=%r' % (objid))
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if isinstance(obj, PDFStream):
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obj.set_objid(objid, 0)
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else:
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self.parser.seek(index)
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(_,objid1) = self.parser.nexttoken() # objid
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(_,genno) = self.parser.nexttoken() # genno
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(_,kwd) = self.parser.nexttoken()
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# #### hack around malformed pdf files
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# assert objid1 == objid, (objid, objid1)
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if objid1 != objid:
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x = []
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while kwd is not self.KEYWORD_OBJ:
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(_,kwd) = self.parser.nexttoken()
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x.append(kwd)
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if x:
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objid1 = x[-2]
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genno = x[-1]
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# #### end hack around malformed pdf files
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if kwd is not self.KEYWORD_OBJ:
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raise PDFSyntaxError('Invalid object spec: offset=%r' % index)
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(_,obj) = self.parser.nextobject()
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if isinstance(obj, PDFStream):
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obj.set_objid(objid, genno)
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if 2 <= self.debug:
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print >>stderr, 'register: objid=%r: %r' % (objid, obj)
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self.objs[objid] = obj
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if self.decipher:
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obj = decipher_all(self.decipher, objid, genno, obj)
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return obj
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INHERITABLE_ATTRS = set(['Resources', 'MediaBox', 'CropBox', 'Rotate'])
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def get_pages(self):
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if not self.ready:
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raise PDFException('PDFDocument is not initialized')
|
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#assert self.xrefs
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def search(obj, parent):
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tree = dict_value(obj).copy()
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for (k,v) in parent.iteritems():
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if k in self.INHERITABLE_ATTRS and k not in tree:
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tree[k] = v
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if tree.get('Type') is LITERAL_PAGES and 'Kids' in tree:
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if 1 <= self.debug:
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print >>stderr, 'Pages: Kids=%r' % tree['Kids']
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for c in list_value(tree['Kids']):
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for x in search(c, tree):
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yield x
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elif tree.get('Type') is LITERAL_PAGE:
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if 1 <= self.debug:
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print >>stderr, 'Page: %r' % tree
|
|
yield (obj.objid, tree)
|
|
if 'Pages' not in self.catalog: return
|
|
for (pageid,tree) in search(self.catalog['Pages'], self.catalog):
|
|
yield PDFPage(self, pageid, tree)
|
|
return
|
|
|
|
def get_outlines(self):
|
|
if 'Outlines' not in self.catalog:
|
|
raise PDFException('No /Outlines defined!')
|
|
def search(entry, level):
|
|
entry = dict_value(entry)
|
|
if 'Title' in entry:
|
|
if 'A' in entry or 'Dest' in entry:
|
|
title = decode_text(str_value(entry['Title']))
|
|
dest = entry.get('Dest')
|
|
action = entry.get('A')
|
|
se = entry.get('SE')
|
|
yield (level, title, dest, action, se)
|
|
if 'First' in entry and 'Last' in entry:
|
|
for x in search(entry['First'], level+1):
|
|
yield x
|
|
if 'Next' in entry:
|
|
for x in search(entry['Next'], level):
|
|
yield x
|
|
return
|
|
return search(self.catalog['Outlines'], 0)
|
|
|
|
def lookup_name(self, cat, key):
|
|
try:
|
|
names = dict_value(self.catalog['Names'])
|
|
except (PDFTypeError, KeyError):
|
|
raise KeyError((cat,key))
|
|
# may raise KeyError
|
|
d0 = dict_value(names[cat])
|
|
def lookup(d):
|
|
if 'Limits' in d:
|
|
(k1,k2) = list_value(d['Limits'])
|
|
if key < k1 or k2 < key: return None
|
|
if 'Names' in d:
|
|
objs = list_value(d['Names'])
|
|
names = dict(choplist(2, objs))
|
|
return names[key]
|
|
if 'Kids' in d:
|
|
for c in list_value(d['Kids']):
|
|
v = lookup(dict_value(c))
|
|
if v: return v
|
|
raise KeyError((cat,key))
|
|
return lookup(d0)
|
|
|
|
|
|
## PDFParser
|
|
##
|
|
class PDFParser(PSStackParser):
|
|
|
|
def __init__(self, doc, fp):
|
|
PSStackParser.__init__(self, fp)
|
|
self.doc = doc
|
|
self.doc.set_parser(self)
|
|
return
|
|
|
|
def __repr__(self):
|
|
return '<PDFParser>'
|
|
|
|
KEYWORD_R = PSKeywordTable.intern('R')
|
|
KEYWORD_ENDOBJ = PSKeywordTable.intern('endobj')
|
|
KEYWORD_STREAM = PSKeywordTable.intern('stream')
|
|
KEYWORD_XREF = PSKeywordTable.intern('xref')
|
|
KEYWORD_STARTXREF = PSKeywordTable.intern('startxref')
|
|
def do_keyword(self, pos, token):
|
|
if token in (self.KEYWORD_XREF, self.KEYWORD_STARTXREF):
|
|
self.add_results(*self.pop(1))
|
|
return
|
|
if token is self.KEYWORD_ENDOBJ:
|
|
self.add_results(*self.pop(4))
|
|
return
|
|
|
|
if token is self.KEYWORD_R:
|
|
# reference to indirect object
|
|
try:
|
|
((_,objid), (_,genno)) = self.pop(2)
|
|
(objid, genno) = (int(objid), int(genno))
|
|
obj = PDFObjRef(self.doc, objid, genno)
|
|
self.push((pos, obj))
|
|
except PSSyntaxError:
|
|
pass
|
|
return
|
|
|
|
if token is self.KEYWORD_STREAM:
|
|
# stream object
|
|
((_,dic),) = self.pop(1)
|
|
dic = dict_value(dic)
|
|
try:
|
|
objlen = int_value(dic['Length'])
|
|
except KeyError:
|
|
if STRICT:
|
|
raise PDFSyntaxError('/Length is undefined: %r' % dic)
|
|
objlen = 0
|
|
self.seek(pos)
|
|
try:
|
|
(_, line) = self.nextline() # 'stream'
|
|
except PSEOF:
|
|
if STRICT:
|
|
raise PDFSyntaxError('Unexpected EOF')
|
|
return
|
|
pos += len(line)
|
|
self.fp.seek(pos)
|
|
data = self.fp.read(objlen)
|
|
self.seek(pos+objlen)
|
|
while 1:
|
|
try:
|
|
(linepos, line) = self.nextline()
|
|
except PSEOF:
|
|
if STRICT:
|
|
raise PDFSyntaxError('Unexpected EOF')
|
|
break
|
|
if 'endstream' in line:
|
|
i = line.index('endstream')
|
|
objlen += i
|
|
data += line[:i]
|
|
break
|
|
objlen += len(line)
|
|
data += line
|
|
self.seek(pos+objlen)
|
|
if 1 <= self.debug:
|
|
print >>stderr, 'Stream: pos=%d, objlen=%d, dic=%r, data=%r...' % \
|
|
(pos, objlen, dic, data[:10])
|
|
obj = PDFStream(dic, data, self.doc.decipher)
|
|
self.push((pos, obj))
|
|
return
|
|
|
|
# others
|
|
self.push((pos, token))
|
|
return
|
|
|
|
def find_xref(self):
|
|
# search the last xref table by scanning the file backwards.
|
|
prev = None
|
|
for line in self.revreadlines():
|
|
line = line.strip()
|
|
if 2 <= self.debug:
|
|
print >>stderr, 'find_xref: %r' % line
|
|
if line == 'startxref': break
|
|
if line:
|
|
prev = line
|
|
else:
|
|
raise PDFNoValidXRef('Unexpected EOF')
|
|
if 1 <= self.debug:
|
|
print >>stderr, 'xref found: pos=%r' % prev
|
|
return long(prev)
|
|
|
|
# read xref table
|
|
def read_xref_from(self, start, xrefs):
|
|
self.seek(start)
|
|
self.reset()
|
|
try:
|
|
(pos, token) = self.nexttoken()
|
|
except PSEOF:
|
|
raise PDFNoValidXRef('Unexpected EOF')
|
|
if 2 <= self.debug:
|
|
print >>stderr, 'read_xref_from: start=%d, token=%r' % (start, token)
|
|
if isinstance(token, int):
|
|
# XRefStream: PDF-1.5
|
|
self.seek(pos)
|
|
self.reset()
|
|
xref = PDFXRefStream()
|
|
xref.load(self, debug=self.debug)
|
|
else:
|
|
if token is self.KEYWORD_XREF:
|
|
self.nextline()
|
|
xref = PDFXRef()
|
|
xref.load(self, debug=self.debug)
|
|
xrefs.append(xref)
|
|
trailer = xref.trailer
|
|
if 1 <= self.debug:
|
|
print >>stderr, 'trailer: %r' % trailer
|
|
if 'XRefStm' in trailer:
|
|
pos = int_value(trailer['XRefStm'])
|
|
self.read_xref_from(pos, xrefs)
|
|
if 'Prev' in trailer:
|
|
# find previous xref
|
|
pos = int_value(trailer['Prev'])
|
|
self.read_xref_from(pos, xrefs)
|
|
return
|
|
|
|
# read xref tables and trailers
|
|
def read_xref(self):
|
|
xrefs = []
|
|
try:
|
|
pos = self.find_xref()
|
|
self.read_xref_from(pos, xrefs)
|
|
except PDFNoValidXRef:
|
|
# fallback
|
|
if 1 <= self.debug:
|
|
print >>stderr, 'no xref, fallback'
|
|
self.seek(0)
|
|
pat = re.compile(r'^(\d+)\s+(\d+)\s+obj\b')
|
|
offsets = {}
|
|
xref = PDFXRef()
|
|
while 1:
|
|
try:
|
|
(pos, line) = self.nextline()
|
|
except PSEOF:
|
|
break
|
|
if line.startswith('trailer'):
|
|
xref.offsets = offsets
|
|
self.seek(pos)
|
|
xref.load_trailer(self)
|
|
if 1 <= self.debug:
|
|
print >>stderr, 'trailer: %r' % xref.trailer
|
|
continue
|
|
m = pat.match(line)
|
|
if not m: continue
|
|
(objid, genno) = m.groups()
|
|
offsets[int(objid)] = (0, pos)
|
|
xrefs.append(xref)
|
|
return xrefs
|
|
|
|
|
|
## PDFObjStrmParser
|
|
##
|
|
class PDFObjStrmParser(PDFParser):
|
|
|
|
def __init__(self, doc, data):
|
|
try:
|
|
from cStringIO import StringIO
|
|
except ImportError:
|
|
from StringIO import StringIO
|
|
PDFParser.__init__(self, doc, StringIO(data))
|
|
return
|
|
|
|
def flush(self):
|
|
self.add_results(*self.popall())
|
|
return
|