edge badge
Methods
F
S
Class Public methods
fixed_length_secure_compare(a, b)

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.

# File activesupport/lib/active_support/security_utils.rb, line 10
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
secure_compare(a, b)

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.

# File activesupport/lib/active_support/security_utils.rb, line 25
def secure_compare(a, b)
  fixed_length_secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b)) && a == b
end