600 lines
20 KiB
Python
600 lines
20 KiB
Python
#!/usr/bin/env python
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import sys
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import re
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import struct
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try:
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import hashlib as md5
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except ImportError:
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import md5
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from psparser import PSEOF
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from psparser import literal_name
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from psparser import LIT, KWD, STRICT
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from pdftypes import PDFException, PDFTypeError, PDFNotImplementedError
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from pdftypes import PDFObjectNotFound, PDFStream
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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 str_value, list_value, dict_value, stream_value
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from pdfparser import PDFSyntaxError
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from pdfparser import PDFStreamParser
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from arcfour import Arcfour
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from utils import choplist, nunpack
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from utils import decode_text
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## Exceptions
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##
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class PDFNoValidXRef(PDFSyntaxError):
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pass
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class PDFNoOutlines(PDFException):
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pass
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class PDFDestinationNotFound(PDFException):
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pass
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class PDFEncryptionError(PDFException):
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pass
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class PDFPasswordIncorrect(PDFEncryptionError):
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pass
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class PDFTextExtractionNotAllowed(PDFEncryptionError):
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pass
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# some predefined literals and keywords.
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LITERAL_OBJSTM = LIT('ObjStm')
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LITERAL_XREF = LIT('XRef')
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LITERAL_CATALOG = LIT('Catalog')
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## XRefs
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##
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class PDFBaseXRef(object):
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def get_trailer(self):
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raise NotImplementedError
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def get_objids(self):
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return []
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# Must return
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# (strmid, index, genno)
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# or (None, pos, genno)
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def get_pos(self, objid):
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raise KeyError(objid)
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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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self.offsets = {}
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self.trailer = {}
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return
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def __repr__(self):
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return '<PDFXRef: offsets=%r>' % (self.offsets.keys())
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def load(self, parser, debug=0):
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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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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':
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continue
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self.offsets[objid] = (None, long(pos), int(genno))
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if 1 <= debug:
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print >>sys.stderr, 'xref objects:', self.offsets
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self.load_trailer(parser)
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return
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KEYWORD_TRAILER = KWD('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 get_trailer(self):
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return self.trailer
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def get_objids(self):
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return self.offsets.iterkeys()
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def get_pos(self, objid):
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try:
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return self.offsets[objid]
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except KeyError:
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raise
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## PDFXRefFallback
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##
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class PDFXRefFallback(PDFXRef):
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def __repr__(self):
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return '<PDFXRefFallback: offsets=%r>' % (self.offsets.keys())
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PDFOBJ_CUE = re.compile(r'^(\d+)\s+(\d+)\s+obj\b')
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def load(self, parser, debug=0):
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parser.seek(0)
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while 1:
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try:
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(pos, line) = parser.nextline()
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except PSEOF:
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break
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if line.startswith('trailer'):
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parser.seek(pos)
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self.load_trailer(parser)
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if 1 <= debug:
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print >>sys.stderr, 'trailer: %r' % self.get_trailer()
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break
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m = self.PDFOBJ_CUE.match(line)
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if not m:
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continue
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(objid, genno) = m.groups()
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objid = int(objid)
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genno = int(genno)
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self.offsets[objid] = (None, pos, genno)
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# expand ObjStm.
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parser.seek(pos)
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(_, obj) = parser.nextobject()
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if isinstance(obj, PDFStream) and obj.get('Type') is LITERAL_OBJSTM:
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stream = stream_value(obj)
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try:
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n = stream['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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parser1 = PDFStreamParser(stream.get_data())
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objs = []
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try:
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while 1:
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(_, obj) = parser1.nextobject()
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objs.append(obj)
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except PSEOF:
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pass
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n = min(n, len(objs)//2)
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for index in xrange(n):
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objid1 = objs[index*2]
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self.offsets[objid1] = (objid, index, 0)
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return
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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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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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self.ranges = []
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return
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def __repr__(self):
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return '<PDFXRefStream: ranges=%r>' % (self.ranges)
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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['Type'] is not LITERAL_XREF:
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raise PDFNoValidXRef('Invalid PDF stream spec.')
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size = stream['Size']
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index_array = stream.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.ranges.extend(choplist(2, index_array))
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(self.fl1, self.fl2, self.fl3) = stream['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.attrs
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if 1 <= debug:
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print >>sys.stderr, ('xref stream: objid=%s, fields=%d,%d,%d' %
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(', '.join(map(repr, self.ranges)),
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self.fl1, self.fl2, self.fl3))
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return
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def get_trailer(self):
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return self.trailer
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def get_objids(self):
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for (start, nobjs) in self.ranges:
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for i in xrange(nobjs):
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offset = self.entlen * i
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ent = self.data[offset:offset+self.entlen]
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f1 = nunpack(ent[:self.fl1], 1)
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if f1 == 1 or f1 == 2:
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yield start+i
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return
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def get_pos(self, objid):
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index = 0
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for (start, nobjs) in self.ranges:
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if start <= objid and objid < start+nobjs:
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index += objid - start
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break
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else:
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index += nobjs
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else:
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raise KeyError(objid)
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offset = self.entlen * index
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ent = self.data[offset:offset+self.entlen]
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f1 = nunpack(ent[:self.fl1], 1)
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f2 = nunpack(ent[self.fl1:self.fl1+self.fl2])
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f3 = nunpack(ent[self.fl1+self.fl2:])
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if f1 == 1:
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return (None, f2, f3)
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elif f1 == 2:
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return (f2, f3, 0)
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else:
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# this is a free object
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raise KeyError(objid)
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## PDFDocument
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##
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class PDFDocument(object):
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"""PDFDocument object represents a PDF document.
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Since a PDF file can be very big, normally it is not loaded at
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once. So PDF document has to cooperate with a PDF parser in order to
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dynamically import the data as processing goes.
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Typical usage:
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doc = PDFDocument(parser, password)
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obj = doc.getobj(objid)
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"""
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debug = 0
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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 __init__(self, parser, password='', caching=True, fallback=True):
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"Set the document to use a given PDFParser object."
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self.caching = caching
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self.xrefs = []
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self.info = []
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self.catalog = None
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self.encryption = None
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self.decipher = None
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self._parser = None
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self._cached_objs = {}
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self._parsed_objs = {}
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self._parser = parser
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self._parser.set_document(self)
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self.is_printable = self.is_modifiable = self.is_extractable = 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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try:
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pos = self.find_xref(parser)
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self.read_xref_from(parser, pos, self.xrefs)
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except PDFNoValidXRef:
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fallback = True
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if fallback:
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parser.fallback = True
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xref = PDFXRefFallback()
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xref.load(parser)
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self.xrefs.append(xref)
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for xref in self.xrefs:
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trailer = xref.get_trailer()
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if not trailer:
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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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self._initialize_password(password)
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if 'Info' in trailer:
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self.info.append(dict_value(trailer['Info']))
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if 'Root' in trailer:
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# Every PDF file must have exactly one /Root dictionary.
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self.catalog = 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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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(password='')
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# Perform the initialization with a given password.
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def _initialize_password(self, password=''):
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(docid, param) = self.encryption
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if literal_name(param.get('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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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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def _getobj_objstm(self, stream, index, objid):
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if stream.objid in self._parsed_objs:
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(objs, n) = self._parsed_objs[stream.objid]
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else:
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(objs, n) = self._get_objects(stream)
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if self.caching:
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self._parsed_objs[stream.objid] = (objs, n)
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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('index too big: %r' % index)
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return obj
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def _get_objects(self, stream):
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if stream.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['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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parser = PDFStreamParser(stream.get_data())
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parser.set_document(self)
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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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return (objs, n)
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KEYWORD_OBJ = KWD('obj')
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def _getobj_parse(self, pos, objid):
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self._parser.seek(pos)
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(_, objid1) = self._parser.nexttoken() # objid
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if objid1 != objid:
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raise PDFSyntaxError('objid mismatch: %r=%r' % (objid1, objid))
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(_, genno) = self._parser.nexttoken() # genno
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(_, kwd) = self._parser.nexttoken()
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if kwd is not self.KEYWORD_OBJ:
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raise PDFSyntaxError('Invalid object spec: offset=%r' % pos)
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(_, obj) = self._parser.nextobject()
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return obj
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# can raise PDFObjectNotFound
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def getobj(self, objid):
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assert objid != 0
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if not self.xrefs:
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raise PDFException('PDFDocument is not initialized')
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if 2 <= self.debug:
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print >>sys.stderr, 'getobj: objid=%r' % (objid)
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if objid in self._cached_objs:
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(obj, genno) = self._cached_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, genno) = xref.get_pos(objid)
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except KeyError:
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continue
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try:
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if strmid is not None:
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stream = stream_value(self.getobj(strmid))
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obj = self._getobj_objstm(stream, index, objid)
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else:
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obj = self._getobj_parse(index, objid)
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if isinstance(obj, PDFStream):
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obj.set_objid(objid, genno)
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break
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except (PSEOF, PDFSyntaxError):
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continue
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else:
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raise PDFObjectNotFound(objid)
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if 2 <= self.debug:
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print >>sys.stderr, 'register: objid=%r: %r' % (objid, obj)
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if self.caching:
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self._cached_objs[objid] = (obj, genno)
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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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def get_outlines(self):
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if 'Outlines' not in self.catalog:
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raise PDFNoOutlines
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def search(entry, level):
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entry = dict_value(entry)
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if 'Title' in entry:
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if 'A' in entry or 'Dest' in entry:
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title = decode_text(str_value(entry['Title']))
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dest = entry.get('Dest')
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action = entry.get('A')
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se = entry.get('SE')
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yield (level, title, dest, action, se)
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if 'First' in entry and 'Last' in entry:
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for x in search(entry['First'], level+1):
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yield x
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if 'Next' in entry:
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for x in search(entry['Next'], level):
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yield x
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return
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return search(self.catalog['Outlines'], 0)
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def lookup_name(self, cat, key):
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try:
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names = dict_value(self.catalog['Names'])
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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)
|
|
|
|
def get_dest(self, name):
|
|
try:
|
|
# PDF-1.2 or later
|
|
obj = self.lookup_name('Dests', name)
|
|
except KeyError:
|
|
# PDF-1.1 or prior
|
|
if 'Dests' not in self.catalog:
|
|
raise PDFDestinationNotFound(name)
|
|
d0 = dict_value(self.catalog['Dests'])
|
|
if name not in d0:
|
|
raise PDFDestinationNotFound(name)
|
|
obj = d0[name]
|
|
return obj
|
|
|
|
# find_xref
|
|
def find_xref(self, parser):
|
|
"""Internal function used to locate the first XRef."""
|
|
# search the last xref table by scanning the file backwards.
|
|
prev = None
|
|
for line in parser.revreadlines():
|
|
line = line.strip()
|
|
if 2 <= self.debug:
|
|
print >>sys.stderr, 'find_xref: %r' % line
|
|
if line == 'startxref':
|
|
break
|
|
if line:
|
|
prev = line
|
|
else:
|
|
raise PDFNoValidXRef('Unexpected EOF')
|
|
if 1 <= self.debug:
|
|
print >>sys.stderr, 'xref found: pos=%r' % prev
|
|
return long(prev)
|
|
|
|
# read xref table
|
|
def read_xref_from(self, parser, start, xrefs):
|
|
"""Reads XRefs from the given location."""
|
|
parser.seek(start)
|
|
parser.reset()
|
|
try:
|
|
(pos, token) = parser.nexttoken()
|
|
except PSEOF:
|
|
raise PDFNoValidXRef('Unexpected EOF')
|
|
if 2 <= self.debug:
|
|
print >>sys.stderr, 'read_xref_from: start=%d, token=%r' % (start, token)
|
|
if isinstance(token, int):
|
|
# XRefStream: PDF-1.5
|
|
parser.seek(pos)
|
|
parser.reset()
|
|
xref = PDFXRefStream()
|
|
xref.load(parser, debug=self.debug)
|
|
else:
|
|
if token is parser.KEYWORD_XREF:
|
|
parser.nextline()
|
|
xref = PDFXRef()
|
|
xref.load(parser, debug=self.debug)
|
|
xrefs.append(xref)
|
|
trailer = xref.get_trailer()
|
|
if 1 <= self.debug:
|
|
print >>sys.stderr, 'trailer: %r' % trailer
|
|
if 'XRefStm' in trailer:
|
|
pos = int_value(trailer['XRefStm'])
|
|
self.read_xref_from(parser, pos, xrefs)
|
|
if 'Prev' in trailer:
|
|
# find previous xref
|
|
pos = int_value(trailer['Prev'])
|
|
self.read_xref_from(parser, pos, xrefs)
|
|
return
|