From 66c3ed01eb012cae84193b4864c7c48eb77c2a8c Mon Sep 17 00:00:00 2001
From: Azul <azul@riseup.net>
Date: Thu, 4 Oct 2012 10:47:19 +0200
Subject: more cleanup - no more duplicate password and username in Client

A client has a set of pwd and login and tries to auth with this.
---
 lib/srp/client.rb   | 22 ++++++++++++----------
 test/auth_test.rb   |  8 +++++---
 test/client_test.rb | 10 ++++------
 3 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/lib/srp/client.rb b/lib/srp/client.rb
index 22ed9f7..de17fb3 100644
--- a/lib/srp/client.rb
+++ b/lib/srp/client.rb
@@ -10,31 +10,33 @@ module SRP
     def initialize(username, password, salt = nil)
       @username = username
       @password = password
-      @salt = (salt || bigrand(4)).hex
+      @salt = salt || bigrand(4).hex
       @multiplier = multiplier # let's cache it
       calculate_verifier
     end
 
-    def authenticate(server, username, password)
-      x = calculate_x(username, password)
+    def authenticate(server)
       a = bigrand(32).hex
       aa = modpow(GENERATOR, a) # A = g^a (mod N)
-      bb = server.handshake(username, aa)
+      bb = server.handshake(@username, aa)
       u = calculate_u(aa, bb)
-      client_s = calculate_client_s(x, a, bb, u)
+      client_s = calculate_client_s(private_key, a, bb, u)
       server.validate(calculate_m(aa, bb, client_s))
     end
 
     protected
+
     def calculate_verifier
-      x = calculate_x
-      @verifier = modpow(GENERATOR, x)
-      @verifier
+      @verifier ||= modpow(GENERATOR, private_key)
+    end
+
+    def private_key
+      @private_key ||= calculate_private_key
     end
 
-    def calculate_x(username = @username, password = @password)
+    def calculate_private_key
       shex = '%x' % [@salt]
-      inner = sha256_str([username, password].join(':'))
+      inner = sha256_str([@username, @password].join(':'))
       sha256_hex(shex, inner).hex
     end
 
diff --git a/test/auth_test.rb b/test/auth_test.rb
index 559403a..c1bffd0 100644
--- a/test/auth_test.rb
+++ b/test/auth_test.rb
@@ -32,15 +32,17 @@ class AuthTest < Test::Unit::TestCase
   end
 
   def test_successful_auth
-    assert @client.authenticate(@server, @username, @password)
+    assert @client.authenticate(@server)
   end
 
   def test_a_wrong_password
-    assert !@client.authenticate(@server, @username, "wrong password")
+    client = SRP::Client.new(@username, "wrong password", @client.salt)
+    assert !client.authenticate(@server)
   end
 
   def test_wrong_username
-    assert !@client.authenticate(@server, "wrong username", @password)
+    client = SRP::Client.new("wrong username", @password, @client.salt)
+    assert !client.authenticate(@server)
   end
 end
 
diff --git a/test/client_test.rb b/test/client_test.rb
index 8ef53aa..3a191a8 100644
--- a/test/client_test.rb
+++ b/test/client_test.rb
@@ -5,22 +5,20 @@ class ClientTest < Test::Unit::TestCase
   def setup
     @login = "testuser"
     @password = "password"
-    @salt = "7686acb8"
-    @client = SRP::Client.new("testuser", "password", "7686acb8")
   end
 
-  def test_calculation_of_x
+  def test_calculation_of_private_key
+    @client = SRP::Client.new(@login, @password, "7686acb8".hex)
     assert_equal "84d6bb567ddf584b1d8c8728289644d45dbfbb02deedd05c0f64db96740f0398",
-      "%x" % @client.send(:calculate_x)
+      "%x" % @client.send(:private_key)
   end
 
   # using python srp:
   # s,V = pysrp.create_salted_verification_key("testuser", "password", pysrp.SHA256, pysrp.NG_1024)
 
   def test_verifier
-    s = '4c78c3f8'
+    @client = SRP::Client.new(@login, @password, '4c78c3f8'.hex)
     v = '474c26aa42d11f20544a00f7bf9711c4b5cf7aab95ed448df82b95521b96668e7480b16efce81c861870302560ddf6604c67df54f1d04b99d5bb9d0f02c6051ada5dc9d594f0d4314e12f876cfca3dcd99fc9c98c2e6a5e04298b11061fb8549a22cde0564e91514080df79bca1c38c682214d65d590f66b3719f954b078b83c'
-    @client = SRP::Client.new(@login, @password, s)
     assert_equal v, "%x" % @client.verifier
   end
 end
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