0x20 hack

 DNS vulnerabilities are teh shitz
 The Dan Kaminskys find a way to
do dns cache poisoning… on
the Internet
 Everyone freaks out
 He gives some solutions like
DNSSEC
 Everyone goes… yeah right. See
you in 2013
 People freak out again

 Inject a fake DNS result into a caching DNS
server
 Clients requesting that hostname will be given
the malicious response
 Works for as long as TTL is set
 Example:
› Vulnerability in BIND exploited
› Injects a cached response for www.google.com
› Grandma goes to www.google.com, and is
redirected

 DNSSEC (we’re getting there)
 Patch your DNS server (yes of course, but not an actual
solution)
 Disable caching (not realistic in most cases)
 Randomize Name Servers (helps limit the affect of a
poison)
 Prepending a nonce to queries (balls930282-
fwq.www.rochester2600.com - effective but “omg what’s
a nonce”)
 Removing duplicate queries (mitigate birthday attack)
 0x20 Hack

 Refers to the simplest hack to modify the case of a
DNS requests
 0x20 bit manipulation is lower CPU cost compared to
for example Python to change the case of a string
 Turns out every DNS server ever can handle this hack
 Requests need to generate a random bitmask
 Only works if the DNS server does not pay attention
to case
 No entropy for TLR or number domains but helps most
hostnames

www.rochester2600.com
WWW.ROCHESTER2600.COM
wWw.rOChesTer2600.CoM
wWW.ROCheSTeR2600.com
WWW.roCHEsTeR2600.COM
000 0000000000000 000
111 1111111111111 111
010 0110001000000 101
011 1110011010011 000
111 0011101010000 111

 Attackers must brute force all possible
combinations of upper and lower to
successfully poison your cache

 I didn’t know about this and love it’s
simplicity
 Hipster Tor

 A and a are 0x20 apart
 The 0x20 hack
 No one uses this anymore…history lesson
 Nothing. You’re not even looking at the
screen right now.

0x20 hack

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0x20 hack