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Timing Attack
Rubens Stulzer
January 19, 2017
Technology
0
55
Timing Attack
Lightning Talk about how to securely compare two strings, using Rails.
Rubens Stulzer
January 19, 2017
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Transcript
Timing Attack
~/awesome/project master= ∴
~/awesome/project master= ∴ git show f19c712702c9fced2461eabd2443c1009baffebb
~/awesome/project master= ∴ git show f19c712702c9fced2461eabd2443c1009baffebb commit f19c712702c9fced2461eabd2443c1009baffebb Author: Rubens
Stulzer <rubens.junior@vivareal.com> Date: Wed Apr 13 17:27:40 2016 -0300 Improves security when comparing password diff --git a/app/models/session.rb b/app/models/session.rb index 7041c8a..685c247 100644 --- a/app/models/session.rb +++ b/app/models/session.rb @@ -89,7 +89,7 @@ private def password_match? - salted_user_password == salted_db_password + ActiveSupport::SecurityUtils.secure_compare(salted_user_password, salted_db_password) end
String comparison using ==
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D
P A S S W O R D P A
S S W O R D true
Time taken - μ20 true P A S S W
O R D P A S S W O R D
P I D S I N G T P A
S S W O R D
P I D S I N G T P A
S S W O R D
P I D S I N G T P A
S S W O R D
P I D S I N G T P A
S S W O R D
P I D S I N G T P A
S S W O R D
P I D S I N G T P A
S S W O R D
P I D S I N G T P A
S S W O R D false
P I D S I N G T P A
S S W O R D Time taken - μ1 false
This is OK
None
We
We
We Ruby
String comparison is supposed to work like that
The problem is the time taken μ1 - For the
wrong one μ20 - For the right one
P A S S W O R D P A
S S I N G T
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S W O R D P A
S S I N G T
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D false
P A S S I N G T P A
S S W O R D Time taken - μ14 false
We have a pattern here
Longer it takes, more close to discover the password you
are
Avoiding this issue with .secure_compare
P A S S W O R D P A
S S I N G T
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S W O R D P A
S S I N G T
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D
P A S S I N G T P A
S S W O R D false
P A S S I N G T P A
S S W O R D Time taken - μ20 false
None
We
We
We Rails
Thank You