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Should address #13: infinite padding decoding loop

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Emmanuel Blot 2019-09-06 18:45:12 +02:00
parent 9992ae524b
commit 3c9603ab5d
1 changed files with 5 additions and 0 deletions
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pybootd/pxed.py
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@ -287,11 +287,16 @@ class BootpServer:
def parse_options(self, tail): def parse_options(self, tail):
self.log.debug('Parsing DHCP options') self.log.debug('Parsing DHCP options')
dhcp_tags = {} dhcp_tags = {}
padding_count = 0
while tail: while tail:
tag = tail[0] tag = tail[0]
# padding # padding
if tag == 0: if tag == 0:
padding_count += 1
if padding_count > 255:
raise ValueError('Padding overflow')
continue continue
padding_count = 0
if tag == 0xff: if tag == 0xff:
return dhcp_tags return dhcp_tags
length = tail[1] length = tail[1]