39 lines
1.3 KiB
Ruby
39 lines
1.3 KiB
Ruby
# frozen_string_literal: true
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module ActiveSupport
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module SecurityUtils
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# Constant time string comparison, for fixed length strings.
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#
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# The values compared should be of fixed length, such as strings
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# that have already been processed by HMAC. Raises in case of length mismatch.
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if defined?(OpenSSL.fixed_length_secure_compare)
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def fixed_length_secure_compare(a, b)
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OpenSSL.fixed_length_secure_compare(a, b)
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end
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else
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def fixed_length_secure_compare(a, b)
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raise ArgumentError, "string length mismatch." unless a.bytesize == b.bytesize
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l = a.unpack "C#{a.bytesize}"
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res = 0
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b.each_byte { |byte| res |= byte ^ l.shift }
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res == 0
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end
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end
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module_function :fixed_length_secure_compare
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# Secure string comparison for strings of variable length.
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#
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# While a timing attack would not be able to discern the content of
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# a secret compared via secure_compare, it is possible to determine
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# the secret length. This should be considered when using secure_compare
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# to compare weak, short secrets to user input.
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def secure_compare(a, b)
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a.bytesize == b.bytesize && fixed_length_secure_compare(a, b)
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end
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module_function :secure_compare
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end
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end
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