Class: SRP::Verifier

Inherits:
Object
  • Object
show all
Defined in:
lib/srp-rb.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(group = 1024, hash = 'sha-1') ⇒ Verifier

Returns a new instance of Verifier.



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# File 'lib/srp-rb.rb', line 339

def initialize(group = 1024, hash = 'sha-1')
  # select modulus (N) and generator (g)
  @N, @g = SRP.Ng(group)
  @hash = hash
  @k = SRP.calc_k(@N, @g, @hash)
end

Instance Attribute Details

#A ⇒ Object (readonly)

Returns the value of attribute A.



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# File 'lib/srp-rb.rb', line 337

def A
  @A
end

#b ⇒ Object (readonly)

Returns the value of attribute b.



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# File 'lib/srp-rb.rb', line 337

def b
  @b
end

#B ⇒ Object (readonly)

Returns the value of attribute B.



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# File 'lib/srp-rb.rb', line 337

def B
  @B
end

#g ⇒ Object (readonly)

Returns the value of attribute g.



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# File 'lib/srp-rb.rb', line 337

def g
  @g
end

#H_AMK ⇒ Object (readonly)

Returns the value of attribute H_AMK.



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# File 'lib/srp-rb.rb', line 337

def H_AMK
  @H_AMK
end

#k ⇒ Object (readonly)

Returns the value of attribute k.



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# File 'lib/srp-rb.rb', line 337

def k
  @k
end

#K ⇒ Object (readonly)

Returns the value of attribute K.



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# File 'lib/srp-rb.rb', line 337

def K
  @K
end

#M ⇒ Object (readonly)

Returns the value of attribute M.



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# File 'lib/srp-rb.rb', line 337

def M
  @M
end

#N ⇒ Object (readonly)

Returns the value of attribute N.



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# File 'lib/srp-rb.rb', line 337

def N
  @N
end

#S ⇒ Object (readonly)

Returns the value of attribute S.



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# File 'lib/srp-rb.rb', line 337

def S
  @S
end

Instance Method Details

#generate_B(xverifier) ⇒ Object

generates challenge input verifier in hex



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# File 'lib/srp-rb.rb', line 416

def generate_B xverifier
  v = xverifier.to_i(16)
  @b ||= random_bignum
  @B = "%x" % SRP.calc_B(@b, k, v, @N, @g)
end

#generate_userauth(username, password) ⇒ Object

Initial user creation for the persistance layer. Not part of the authentication process. Returns { <username>, <password verifier>, <salt> }



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# File 'lib/srp-rb.rb', line 349

def generate_userauth username, password
  @salt ||= random_salt
  # warn "salt: #{@salt}"
  x = SRP.calc_x(username, password, @salt, @hash)
  v = SRP.calc_v(x, @N, @g)
  return {:username => username, :verifier => "%x" % v, :salt => @salt}
end

#get_challenge_and_proof(username, xverifier, xsalt, xaa) ⇒ Object

Authentication phase 1 - create challenge. Returns Hash with challenge for client and proof to be stored on server. Parameters should be given in hex.



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# File 'lib/srp-rb.rb', line 360

def get_challenge_and_proof username, xverifier, xsalt, xaa
  # SRP-6a safety check
  return false if (xaa.to_i(16) % @N) == 0
  generate_B(xverifier)
  # warn "A: #{xaa}"
  return {
    :challenge    => {:B => @B, :salt => xsalt},
    :proof        => {:A => xaa, :B => @B, :b => "%x" % @b,
                      :I => username, :s => xsalt, :v => xverifier}
  }
end

#random_bignum ⇒ Object 



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# File 'lib/srp-rb.rb', line 410

def random_bignum
  SRP.bigrand(32).hex
end

#random_salt ⇒ Object 



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# File 'lib/srp-rb.rb', line 406

def random_salt
  "%x" % SRP.bigrand(16).hex
end

#verify_session(proof, client_M) ⇒ Object

returns H_AMK on success, None on failure User -> Host: M = H(H(N) xor H(g), H(I), s, A, B, K) Host -> User: H(A, M, K)



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# File 'lib/srp-rb.rb', line 375

def verify_session proof, client_M
  @A = proof[:A]
  @B = proof[:B]
  @b = proof[:b].to_i(16)
  # warn "b: #{@b}"
  
  username = proof[:I]
  xsalt = proof[:s]
  v = proof[:v].to_i(16)

  u = SRP.calc_u(@A, @B, @N, @hash)
  # SRP-6a safety check
  return false if u == 0

  # calculate session key
  @S = "%x" % SRP.calc_server_S(@A.to_i(16), @b, v, u, @N)

  @K = SRP.sha1_hex(@S, @hash)
  # warn "K: #{@K}"

  # calculate match
  @M = "%x" % SRP.calc_M1(@A, @B, @K, @N, @hash)
  
  if @M == client_M
    # authentication succeeded
    @H_AMK = "%x" % SRP.calc_M2(@A, @M, @K, @N, @hash)
    return @H_AMK
  end
  return false
end