[prosody.git] / util / sasl / scram.lua

-- sasl.lua v0.4
-- Copyright (C) 2008-2010 Tobias Markmann
--
--        All rights reserved.
--
--        Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
--
--                * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
--                * 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.
--                * 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.
--
--        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.

local s_match = string.match;
local type = type
local string = string
local base64 = require "util.encodings".base64;
local hmac_sha1 = require "util.hmac".sha1;
local sha1 = require "util.hashes".sha1;
local generate_uuid = require "util.uuid".generate;
local saslprep = require "util.encodings".stringprep.saslprep;
local log = require "util.logger".init("sasl");
local t_concat = table.concat;
local char = string.char;
local byte = string.byte;

module "scram"

--=========================
--SASL SCRAM-SHA-1 according to draft-ietf-sasl-scram-10

--[[
Supported Authentication Backends

scram_{MECH}:
        -- MECH being a standard hash name (like those at IANA's hash registry) with '-' replaced with '_'
        function(username, realm)
                return salted_password, iteration_count, salt, state;
        end
]]

local default_i = 4096

local function bp( b )
        local result = ""
        for i=1, b:len() do
                result = result.."\\"..b:byte(i)
        end
        return result
end

local xor_map = {0;1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;1;0;3;2;5;4;7;6;9;8;11;10;13;12;15;14;2;3;0;1;6;7;4;5;10;11;8;9;14;15;12;13;3;2;1;0;7;6;5;4;11;10;9;8;15;14;13;12;4;5;6;7;0;1;2;3;12;13;14;15;8;9;10;11;5;4;7;6;1;0;3;2;13;12;15;14;9;8;11;10;6;7;4;5;2;3;0;1;14;15;12;13;10;11;8;9;7;6;5;4;3;2;1;0;15;14;13;12;11;10;9;8;8;9;10;11;12;13;14;15;0;1;2;3;4;5;6;7;9;8;11;10;13;12;15;14;1;0;3;2;5;4;7;6;10;11;8;9;14;15;12;13;2;3;0;1;6;7;4;5;11;10;9;8;15;14;13;12;3;2;1;0;7;6;5;4;12;13;14;15;8;9;10;11;4;5;6;7;0;1;2;3;13;12;15;14;9;8;11;10;5;4;7;6;1;0;3;2;14;15;12;13;10;11;8;9;6;7;4;5;2;3;0;1;15;14;13;12;11;10;9;8;7;6;5;4;3;2;1;0;};

local result = {};
local function binaryXOR( a, b )
        for i=1, #a do
                local x, y = byte(a, i), byte(b, i);
                local lowx, lowy = x % 16, y % 16;
                local hix, hiy = (x - lowx) / 16, (y - lowy) / 16;
                local lowr, hir = xor_map[lowx * 16 + lowy + 1], xor_map[hix * 16 + hiy + 1];
                local r = hir * 16 + lowr;
                result[i] = char(r)
        end
        return t_concat(result);
end

-- hash algorithm independent Hi(PBKDF2) implementation
local function Hi(hmac, str, salt, i)
        local Ust = hmac(str, salt.."\0\0\0\1");
        local res = Ust;        
        for n=1,i-1 do
                local Und = hmac(str, Ust)
                res = binaryXOR(res, Und)
                Ust = Und
        end
        return res
end

local function validate_username(username)
        -- check for forbidden char sequences
        for eq in username:gmatch("=(.?.?)") do
                if eq ~= "2D" and eq ~= "3D" then
                        return false 
                end 
        end
        
        -- replace =2D with , and =3D with =
        username = username:gsub("=2D", ",");
        username = username:gsub("=3D", "=");
        
        -- apply SASLprep
        username = saslprep(username);
        return username;
end

local function hashprep( hashname ) 
        local hash = hashname:lower()
        hash = hash:gsub("-", "_")
        return hash
end

function saltedPasswordSHA1(password, salt, iteration_count)
        local salted_password
        if type(password) ~= "string" or type(salt) ~= "string" or type(iteration_count) ~= "number" then
                return false, "inappropriate argument types"
        end
        if iteration_count < 4096 then
                log("warning", "Iteration count < 4096 which is the suggested minimum according to RFC 5802.")
        end

        return true, Hi(hmac_sha1, password, salt, iteration_count);
end

local function scram_gen(hash_name, H_f, HMAC_f)
        local function scram_hash(self, message)
                if not self.state then self["state"] = {} end
        
                if type(message) ~= "string" or #message == 0 then return "failure", "malformed-request" end
                if not self.state.name then
                        -- we are processing client_first_message
                        local client_first_message = message;
                        
                        -- TODO: fail if authzid is provided, since we don't support them yet
                        self.state["client_first_message"] = client_first_message;
                        self.state["gs2_cbind_flag"], self.state["authzid"], self.state["name"], self.state["clientnonce"]
                                = client_first_message:match("^(%a),(.*),n=(.*),r=([^,]*).*");

                        -- we don't do any channel binding yet
                        if self.state.gs2_cbind_flag ~= "n" and self.state.gs2_cbind_flag ~= "y" then
                                return "failure", "malformed-request";
                        end

                        if not self.state.name or not self.state.clientnonce then
                                return "failure", "malformed-request", "Channel binding isn't support at this time.";
                        end
                
                        self.state.name = validate_username(self.state.name);
                        if not self.state.name then
                                log("debug", "Username violates either SASLprep or contains forbidden character sequences.")
                                return "failure", "malformed-request", "Invalid username.";
                        end
                
                        self.state["servernonce"] = generate_uuid();
                        
                        -- retreive credentials
                        if self.profile.plain then
                                local password, state = self.profile.plain(self.state.name, self.realm)
                                if state == nil then return "failure", "not-authorized"
                                elseif state == false then return "failure", "account-disabled" end
                                
                                password = saslprep(password);
                                if not password then
                                        log("debug", "Password violates SASLprep.");
                                        return "failure", "not-authorized", "Invalid password."
                                end

                                self.state.salt = generate_uuid();
                                self.state.iteration_count = default_i;

                                local succ = false;
                                succ, self.state.salted_password = saltedPasswordSHA1(password, self.state.salt, default_i, self.state.iteration_count);
                                if not succ then
                                        log("error", "Generating salted password failed. Reason: %s", self.state.salted_password);
                                        return "failure", "temporary-auth-failure";
                                end
                        elseif self.profile["scram_"..hashprep(hash_name)] then
                                local salted_password, iteration_count, salt, state = self.profile["scram-"..hash_name](self.state.name, self.realm);
                                if state == nil then return "failure", "not-authorized"
                                elseif state == false then return "failure", "account-disabled" end
                                
                                self.state.salted_password = salted_password;
                                self.state.iteration_count = iteration_count;
                                self.state.salt = salt
                        end
                
                        local server_first_message = "r="..self.state.clientnonce..self.state.servernonce..",s="..base64.encode(self.state.salt)..",i="..self.state.iteration_count;
                        self.state["server_first_message"] = server_first_message;
                        return "challenge", server_first_message
                else
                        -- we are processing client_final_message
                        local client_final_message = message;
                        
                        self.state["channelbinding"], self.state["nonce"], self.state["proof"] = client_final_message:match("^c=(.*),r=(.*),.*p=(.*)");
        
                        if not self.state.proof or not self.state.nonce or not self.state.channelbinding then
                                return "failure", "malformed-request", "Missing an attribute(p, r or c) in SASL message.";
                        end

                        if self.state.nonce ~= self.state.clientnonce..self.state.servernonce then
                                return "failure", "malformed-request", "Wrong nonce in client-final-message.";
                        end
                        
                        local SaltedPassword = self.state.salted_password;
                        local ClientKey = HMAC_f(SaltedPassword, "Client Key")
                        local ServerKey = HMAC_f(SaltedPassword, "Server Key")
                        local StoredKey = H_f(ClientKey)
                        local AuthMessage = "n=" .. s_match(self.state.client_first_message,"n=(.+)") .. "," .. self.state.server_first_message .. "," .. s_match(client_final_message, "(.+),p=.+")
                        local ClientSignature = HMAC_f(StoredKey, AuthMessage)
                        local ClientProof     = binaryXOR(ClientKey, ClientSignature)
                        local ServerSignature = HMAC_f(ServerKey, AuthMessage)

                        if base64.encode(ClientProof) == self.state.proof then
                                local server_final_message = "v="..base64.encode(ServerSignature);
                                self["username"] = self.state.name;
                                return "success", server_final_message;
                        else
                                return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated.";
                        end
                end
        end
        return scram_hash;
end

function init(registerMechanism)
        local function registerSCRAMMechanism(hash_name, hash, hmac_hash)
                registerMechanism("SCRAM-"..hash_name, {"plain", "scram_"..(hashprep(hash_name))}, scram_gen(hash_name:lower(), hash, hmac_hash));
        end

        registerSCRAMMechanism("SHA-1", sha1, hmac_sha1);
end

return _M;