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-- Session handling routines - written for acf
-- Copyright (C) 2007 N. Angelacos - GPL2 License
--[[ Note that in this library, we use empty (0 byte) files
-- everwhere we can, as they only take up dir entries, not inodes
-- as the tmpfs blocksize is 4K, and under denial of service
-- attacks hundreds or thousands of events can come in each
-- second, we could end up in a disk full condition if we did
-- not take this precaution.
-- ]]--
module (..., package.seeall)
require "posix"
minutes_expired_events=30
minutes_count_events=30
limit_count_events=10
cached_content=nil
local b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-"
-- Return a sessionid of at least size bits length
random_hash = function (size)
local file = io.open("/dev/urandom")
local str = ""
if file == nil then return nil end
while (size > 0 ) do
local offset = (string.byte(file:read(1)) % 64) + 1
str = str .. string.sub (b64, offset, offset)
size = size - 6
end
return str
end
-- FIXME: only hashes ipv4
hash_ip_addr = function (string)
local str = ""
for i in string.gmatch(string, "%d+") do
str = str .. string.format("%02x", i )
end
return str
end
ip_addr_from_hash = function (string)
local str = ""
for i in string.gmatch(string, "..") do
str = str .. string.format("%d", "0x" .. i) .. "."
end
return string.sub(str, 1, string.len(str)-1)
end
--[[
These functions serialize a table, including nested tables.
The code based on code in PiL 2nd edition p113
]]--
local function basicSerialize (o)
if type(o) == "number" then
return tostring(o)
else
return string.format("%q", o)
end
end
function serialize (name, value, saved, output )
local need_to_concat = (output == nil)
output = output or {}
saved = saved or {}
local str = name .. " = "
if type(value) == "number" or type(value) == "string" then
table.insert(output, str .. basicSerialize (value))
elseif type(value) == "table" then
if saved[value] then
table.insert(output, str .. saved[value])
else
saved[value] = name
table.insert(output, str .. "{}")
for k,v in pairs(value) do
local fieldname = string.format("%s[%s]", name, basicSerialize(k))
serialize (fieldname, v, saved, output)
end
end
elseif type(value) == "boolean" then
table.insert(output, str .. tostring(value))
else
table.insert(output, str .. "nil") -- cannot save other types, so skip them
end
if need_to_concat then
table.sort(output)
return table.concat(output, "\n")
end
return
end
-- Save the session (unless all it contains is the id)
-- return true or false for success
save_session = function( sessionpath, sessiontable)
if nil == sessiontable or nil == sessiontable.id then return false end
-- clear the id key, don't need to store that
local id = sessiontable.id
sessiontable.id = nil
-- If the table only has an "id" field, then don't save it
if #sessiontable then
local output = {}
output[#output+1] = "-- This is an ACF session table."
output[#output+1] = "local " .. serialize("s", sessiontable)
output[#output+1] = "return s"
local content = table.concat(output, "\n") .. "\n"
-- want to avoid writing unless changed, becuase opening for write
-- prevents simultaneous opening for read
if content ~= cached_content then
local file = io.open(sessionpath .. "/session." .. id , "w")
if file == nil then
sessiontable.id=id
return false
end
file:write(content)
file:close()
end
end
sessiontable.id=id
return true
end
-- Loads a session
-- Returns a timestamp (when the session data was saved) and the session table.
-- Insert the session into the "id" field
load_session = function ( sessionpath, session )
if type(session) ~= "string" then return nil, {} end
local s = {}
-- session can only have b64 characters in it
session = string.gsub ( session or "", "[^" .. b64 .. "]", "")
if #session == 0 then
return nil, {}
end
local spath = sessionpath .. "/session." .. session
local ts = posix.stat(spath, "ctime")
if (ts) then
-- this loop is here because can't read file here if another process is writing it above
-- and if this fails, it effectively logs the user off (writes back blank session data)
local s
for i=1,20 do
local file = io.open(spath)
if file then
cached_content = file:read("*a")
file:close()
s = loadstring(cached_content)()
break
end
sleep(10*i)
end
s = s or {}
s.id = session
return ts, s
else
return nil, {}
end
end
-- Unlinks a session (deletes the session file)
-- return nil for failure, ?? for success
unlink_session = function (sessionpath, session)
if type(session) ~= "string" then return nil end
local s = string.gsub (session, "[^" .. b64 .. "]", "")
if s ~= session then
return nil
end
session = sessionpath .. "/session." .. s
local statos = os.remove (session)
return statos
end
-- Record an invalid login event
-- ID would typically be an ip address or username
-- the format is lockevent.id.datetime.processid
record_event = function( sessionpath, id_u, id_ip )
local x = io.open (string.format ("%s/lockevent.%s.%s.%s.%s",
sessionpath or "/", id_u or "", id_ip or "", os.time(),
(posix.getpid("pid")) or "" ), "w")
io.close(x)
end
-- Check how many invalid login events
-- have happened for this id in the last n minutes
-- this will only effect the lockevent files
count_events = function (sessionpath, id_user, ipaddr)
--we need to have the counts added up? deny off any and or all
local now = os.time()
local minutes_ago = now - (minutes_count_events * 60)
local t = {}
--give me all lockevents then we will sort through them
local searchfor = sessionpath .. "/lockevent.*"
local t = posix.glob(searchfor)
if t == nil or id_user == nil or ipaddr == nil then
return false
else
local count = 0
for a,b in pairs(t) do
if posix.stat(b,"mtime") > minutes_ago then
if string.match(b,id_user) or string.match(b,ipaddr) then
count = count + 1
end
end
end
if count>limit_count_events then
return true
else
return false
end
end
end
-- Clear events that are older than n minutes
expired_events = function (sessionpath)
--current os time in seconds
local now = os.time()
--take minutes and convert to seconds
local minutes_ago = now - (minutes_expired_events * 60)
local searchfor = sessionpath .. "/lockevent.*"
--first do the lockevent files
local temp = posix.glob(searchfor)
if temp ~= nil then
for a,b in pairs(temp) do
if posix.stat(b,"mtime") < minutes_ago then
os.remove(b)
end
end
end
--now do the session files
searchfor = sessionpath .. "/session.*"
local temp = posix.glob(searchfor)
if temp ~= nil then
for a,b in pairs(temp) do
if posix.stat(b,"mtime") < minutes_ago then
os.remove(b)
end
end
end
return 0
end
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