util/sasl.lua

   1 -- sasl.lua v0.4
   2 -- Copyright (C) 2008-2010 Tobias Markmann
   3 --
   4 --    All rights reserved.
   5 --
   6 --    Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
   7 --
   8 --        * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
   9 --        * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  10 --        * Neither the name of Tobias Markmann nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
  11 --
  12 --    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  13
  14
  15 local pairs, ipairs = pairs, ipairs;
  16 local t_insert = table.insert;
  17 local type = type
  18 local setmetatable = setmetatable;
  19 local assert = assert;
  20 local require = require;
  21
  22 local _ENV = nil;
  23 -- luacheck: std none
  24
  25 --[[
  26 Authentication Backend Prototypes:
  27
  28 state = false : disabled
  29 state = true : enabled
  30 state = nil : non-existant
  31
  32 Channel Binding:
  33
  34 To enable support of channel binding in some mechanisms you need to provide appropriate callbacks in a table
  35 at profile.cb.
  36
  37 Example:
  38         profile.cb["tls-unique"] = function(self)
  39                 return self.user
  40         end
  41
  42 ]]
  43
  44 local method = {};
  45 method.__index = method;
  46 local registered_mechanisms = {};
  47 local backend_mechanism = {};
  48 local mechanism_channelbindings = {};
  49
  50 -- register a new SASL mechanims
  51 local function registerMechanism(name, backends, f, cb_backends)
  52         assert(type(name) == "string", "Parameter name MUST be a string.");
  53         assert(type(backends) == "string" or type(backends) == "table", "Parameter backends MUST be either a string or a table.");
  54         assert(type(f) == "function", "Parameter f MUST be a function.");
  55         if cb_backends then assert(type(cb_backends) == "table"); end
  56         registered_mechanisms[name] = f
  57         if cb_backends then
  58                 mechanism_channelbindings[name] = {};
  59                 for _, cb_name in ipairs(cb_backends) do
  60                         mechanism_channelbindings[name][cb_name] = true;
  61                 end
  62         end
  63         for _, backend_name in ipairs(backends) do
  64                 if backend_mechanism[backend_name] == nil then backend_mechanism[backend_name] = {}; end
  65                 t_insert(backend_mechanism[backend_name], name);
  66         end
  67 end
  68
  69 -- create a new SASL object which can be used to authenticate clients
  70 local function new(realm, profile)
  71         local mechanisms = profile.mechanisms;
  72         if not mechanisms then
  73                 mechanisms = {};
  74                 for backend in pairs(profile) do
  75                         if backend_mechanism[backend] then
  76                                 for _, mechanism in ipairs(backend_mechanism[backend]) do
  77                                         mechanisms[mechanism] = true;
  78                                 end
  79                         end
  80                 end
  81                 profile.mechanisms = mechanisms;
  82         end
  83         return setmetatable({ profile = profile, realm = realm, mechs = mechanisms }, method);
  84 end
  85
  86 -- add a channel binding handler
  87 function method:add_cb_handler(name, f)
  88         if type(self.profile.cb) ~= "table" then
  89                 self.profile.cb = {};
  90         end
  91         self.profile.cb[name] = f;
  92         return self;
  93 end
  94
  95 -- get a fresh clone with the same realm and profile
  96 function method:clean_clone()
  97         return new(self.realm, self.profile)
  98 end
  99
 100 -- get a list of possible SASL mechanims to use
 101 function method:mechanisms()
 102         local current_mechs = {};
 103         for mech, _ in pairs(self.mechs) do
 104                 if mechanism_channelbindings[mech] then
 105                         if self.profile.cb then
 106                                 local ok = false;
 107                                 for cb_name, _ in pairs(self.profile.cb) do
 108                                         if mechanism_channelbindings[mech][cb_name] then
 109                                                 ok = true;
 110                                         end
 111                                 end
 112                                 if ok == true then current_mechs[mech] = true; end
 113                         end
 114                 else
 115                         current_mechs[mech] = true;
 116                 end
 117         end
 118         return current_mechs;
 119 end
 120
 121 -- select a mechanism to use
 122 function method:select(mechanism)
 123         if not self.selected and self.mechs[mechanism] then
 124                 self.selected = mechanism;
 125                 return true;
 126         end
 127 end
 128
 129 -- feed new messages to process into the library
 130 function method:process(message)
 131         --if message == "" or message == nil then return "failure", "malformed-request" end
 132         return registered_mechanisms[self.selected](self, message);
 133 end
 134
 135 -- load the mechanisms
 136 require "util.sasl.plain"     .init(registerMechanism);
 137 require "util.sasl.digest-md5".init(registerMechanism);
 138 require "util.sasl.anonymous" .init(registerMechanism);
 139 require "util.sasl.scram"     .init(registerMechanism);
 140 require "util.sasl.external"  .init(registerMechanism);
 141
 142 return {
 143         registerMechanism = registerMechanism;
 144         new = new;
 145 };