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module ActiveSupport::SecurityUtils

Public Class Methods

fixed_length_secure_compare(a, b) Show source

# File activesupport/lib/active_support/security_utils.rb, line 11
def fixed_length_secure_compare(a, b)
  raise ArgumentError, "string length mismatch." unless a.bytesize == b.bytesize

  l = a.unpack "C#{a.bytesize}"

  res = 0
  b.each_byte { |byte| res |= byte ^ l.shift }
  res == 0
end

Constant time string comparison, for fixed length strings.

The values compared should be of fixed length, such as strings that have already been processed by HMAC. Raises in case of length mismatch.

secure_compare(a, b) Show source

# File activesupport/lib/active_support/security_utils.rb, line 26
def secure_compare(a, b)
  fixed_length_secure_compare(::Digest::SHA256.digest(a), ::Digest::SHA256.digest(b)) && a == b
end

Constant time string comparison, for variable length strings.

The values are first processed by SHA256, so that we don't leak length info via timing attacks.