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Fixed a bug where corrupt exif tags would make the analysis process stall.

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This commit is contained in:
Virgil Dupras 2011-06-14 15:05:33 -04:00
parent 2a6f524a5b
commit 4399fe9d17
1 changed files with 12 additions and 0 deletions
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12
core_pe/exif.py
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@ -154,6 +154,12 @@ GPS_TA0GS = {
INTEL_ENDIAN = ord('I') INTEL_ENDIAN = ord('I')
MOTOROLA_ENDIAN = ord('M') MOTOROLA_ENDIAN = ord('M')
# About MAX_COUNT: It's possible to have corrupted exif tags where the entry count is way too high
# and thus makes us loop, not endlessly, but for heck of a long time for nothing. Therefore, we put
# an arbitrary limit on the entry count we'll allow ourselves to read and any IFD reporting more
# entries than that will be considered corrupt.
MAX_COUNT = 0xffff
def s2n_motorola(bytes): def s2n_motorola(bytes):
x = 0 x = 0
for c in bytes: for c in bytes:
@ -214,6 +220,9 @@ class TIFF_file:
def dump_IFD(self, ifd): def dump_IFD(self, ifd):
entries = self.s2n(ifd, 2) entries = self.s2n(ifd, 2)
logging.debug("Entries for IFD %d: %d", ifd, entries) logging.debug("Entries for IFD %d: %d", ifd, entries)
if entries > MAX_COUNT:
logging.debug("Probably corrupt. Aborting.")
return []
a = [] a = []
for i in range(entries): for i in range(entries):
entry = ifd + 2 + 12*i entry = ifd + 2 + 12*i
@ -223,6 +232,9 @@ class TIFF_file:
continue # not handled continue # not handled
typelen = [ 1, 1, 2, 4, 8, 1, 1, 2, 4, 8 ] [type-1] typelen = [ 1, 1, 2, 4, 8, 1, 1, 2, 4, 8 ] [type-1]
count = self.s2n(entry+4, 4) count = self.s2n(entry+4, 4)
if count > MAX_COUNT:
logging.debug("Probably corrupt. Aborting.")
return []
offset = entry+8 offset = entry+8
if count*typelen > 4: if count*typelen > 4:
offset = self.s2n(offset, 4) offset = self.s2n(offset, 4)