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Timing Attack

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~/awesome/project master= ∴

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~/awesome/project master= ∴ git show f19c712702c9fced2461eabd2443c1009baffebb

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~/awesome/project master= ∴ git show f19c712702c9fced2461eabd2443c1009baffebb commit f19c712702c9fced2461eabd2443c1009baffebb Author: Rubens Stulzer 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

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String comparison using ==

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P A S S W O R D P A S S W O R D

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P A S S W O R D P A S S W O R D

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P A S S W O R D P A S S W O R D

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P A S S W O R D P A S S W O R D true

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Time taken - μ20 true P A S S W O R D P A S S W O R D

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P I D S I N G T P A S S W O R D

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P I D S I N G T P A S S W O R D false

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P I D S I N G T P A S S W O R D Time taken - μ1 false

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This is OK

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No content

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We

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We

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We Ruby

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String comparison is supposed to work like that

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The problem is the time taken μ1 - For the wrong one μ20 - For the right one

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P A S S W O R D P A S S I N G T

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P A S S I N G T P A S S W O R D

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P A S S W O R D P A S S I N G T

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P A S S I N G T P A S S W O R D

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P A S S I N G T P A S S W O R D false

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P A S S I N G T P A S S W O R D Time taken - μ14 false

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We have a pattern here

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Longer it takes, more close to discover the password you are

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Avoiding this issue with .secure_compare

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P A S S W O R D P A S S I N G T

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P A S S I N G T P A S S W O R D false

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P A S S I N G T P A S S W O R D Time taken - μ20 false

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No content

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We

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We

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We Rails

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Thank You