Class: OpenID::DiffieHelmanAssociator

Inherits:
Object
  • Object
show all
Includes:
OpenID
Defined in:
lib/openid/association.rb

Overview

A class for establishing associations with OpenID servers.

Constant Summary

Constants included from OpenID

DEFAULT_DH_GEN, DEFAULT_DH_MODULUS, SECRET_SIZES

Instance Method Summary collapse

Methods included from OpenID

#append_args, #error_page, #from_btwoc, #normalize_url, #parse_kv, #parse_link_attrs, #quote_minimal, #redirect, #response_page, #sign_reply, #url_encode

Constructor Details

#initialize(http_client) ⇒ DiffieHelmanAssociator

Returns a new instance of DiffieHelmanAssociator.



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# File 'lib/openid/association.rb', line 146

def initialize(http_client)
	@http_client = http_client
end

Instance Method Details

#associate(server_url) ⇒ Object

Establishes an association with an OpenID server, indicated by server_url. Returns a ConsumerAssociation.



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# File 'lib/openid/association.rb', line 158

def associate(server_url)
	p, g = get_mod_gen()
	private_key = (1 + rand(p-2))
	dh_public = g.mod_exp(private_key, p)
	args = {
		'openid.mode' => 'associate',
		'openid.assoc_type' => 'HMAC-SHA1',
		'openid.session_type' => 'DH-SHA1',
		'openid.dh_modulus' => Base64.encode64(p.to_btwoc).delete("\n"),
		'openid.dh_gen' => Base64.encode64(g.to_btwoc).delete("\n"),
		'openid.dh_consumer_public' => Base64.encode64(dh_public.to_btwoc).delete("\n")
	}
	body = url_encode(args)
	url, data = @http_client.post(server_url, body)
	now = Time.now.utc
	# results are temporarily stored in an instance variable.
	# I'd like to restructure to avoid this.
	@results = parse_kv(data)
	
	assoc_type = get_result('assoc_type')
	if assoc_type != 'HMAC-SHA1'
		raise RuntimeError, "Unknown association type: #{assoc_type}", caller
	end
	
	assoc_handle = get_result('assoc_handle')
	issued = DateTime.strptime(get_result('issued')).to_time
	expiry = DateTime.strptime(get_result('expiry')).to_time
	
	delta = now - issued
	expiry = expiry + delta
	
	replace_after_s = @results['replace_after']
	if replace_after_s
		replace_after = DateTime.strptime(replace_after_s).to_time + delta
	else
		replace_after = nil
	end
	
	session_type = @results['session_type']
	if session_type
		if session_type != 'DH-SHA1'
			raise RuntimeError, "Unknown Session Type: #{session_type}", caller
		end
		dh_server_pub = from_btwoc(Base64.decode64(get_result('dh_server_public')))
		enc_mac_key = get_result('enc_mac_key')
		dh_shared = dh_server_pub.mod_exp(private_key, p)

		secret = Base64.decode64(enc_mac_key) ^ Digest::SHA1.digest(dh_shared.to_btwoc)
	else
		secret = get_result('mac_key')
	end
	@results = nil
	return ConsumerAssociation.new(server_url, assoc_handle, secret, expiry, replace_after)
end

#get_mod_gen ⇒ Object

Returns modulus and generator for Diffie-Helman. Override this for non-default values.



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# File 'lib/openid/association.rb', line 152

def get_mod_gen()
	return DEFAULT_DH_MODULUS, DEFAULT_DH_GEN
end