Class: ROTP::OTP

Inherits:
Object
  • Object
show all
Defined in:
lib/rotp/otp.rb

Direct Known Subclasses

HOTP, TOTP

Constant Summary collapse

DEFAULT_DIGITS = 
6

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(s, options = {}) ⇒ OTP

Returns a new instance of OTP.

Parameters:

  • secret (String) —

    in the form of base32

  • options (Hash) (defaults to: {}) —

    a customizable set of options

Options Hash (options):

  • digits (Integer) — default: 6 —

    Number of integers in the OTP Google Authenticate only supports 6 currently

  • digest (String) — default: sha1 —

    Digest used in the HMAC Google Authenticate only supports ‘sha1’ currently



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# File 'lib/rotp/otp.rb', line 14

def initialize(s, options = {})
  @digits = options[:digits] || DEFAULT_DIGITS
  @digest = options[:digest] || "sha1"
  @secret = s
end

Instance Attribute Details

#digest ⇒ Object (readonly)

Returns the value of attribute digest.



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# File 'lib/rotp/otp.rb', line 3

def digest
  @digest
end

#digits ⇒ Object (readonly)

Returns the value of attribute digits.



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# File 'lib/rotp/otp.rb', line 3

def digits
  @digits
end

#secret ⇒ Object (readonly)

Returns the value of attribute secret.



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# File 'lib/rotp/otp.rb', line 3

def secret
  @secret
end

Instance Method Details

#generate_otp(input, padded = true) ⇒ Object

Usually either the counter, or the computed integer based on the Unix timestamp

Parameters:

  • input (Integer) —

    the number used seed the HMAC

  • padded (Hash) (defaults to: true) —

    a customizable set of options

Options Hash (padded):

  • (false) (Boolean) —

    Output the otp as a 0 padded string



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# File 'lib/rotp/otp.rb', line 24

def generate_otp(input, padded=true)
  hmac = OpenSSL::HMAC.digest(
    OpenSSL::Digest.new(digest),
    byte_secret,
    int_to_bytestring(input)
  )

  offset = hmac[-1].ord & 0xf
  code = (hmac[offset].ord & 0x7f) << 24 |
    (hmac[offset + 1].ord & 0xff) << 16 |
    (hmac[offset + 2].ord & 0xff) << 8 |
    (hmac[offset + 3].ord & 0xff)
  if padded
    (code % 10 ** digits).to_s.rjust(digits, '0')
  else
    code % 10 ** digits
  end
end