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@mattlong
Created April 6, 2020 17:40
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Rails CSRF token analyzer
def real_csrf_token(token)
Base64.strict_decode64(token)
end
def xor_byte_strings(s1, s2)
s2_bytes = s2.bytes
s1.each_byte.with_index { |c1, i| s2_bytes[i] ^= c1 }
s2_bytes.pack("C*")
end
def unmask_token(masked_token)
one_time_pad = masked_token[0...AUTHENTICITY_TOKEN_LENGTH]
encrypted_csrf_token = masked_token[AUTHENTICITY_TOKEN_LENGTH..-1]
xor_byte_strings(one_time_pad, encrypted_csrf_token)
end
def compare_with_real_token(token, real_token)
ActiveSupport::SecurityUtils.secure_compare(token, real_csrf_token(real_token))
end
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