Initial commit

tg_server/taskguard.cfg

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+local config = {
+    name = "tg_server",
+    modem_side = "top",
+    clearance_expiry = 600, -- Minutes until clearance will expire
+    key_file = "verified_keys.txt", -- Name of the key file, relative to tg_server.lua
+}
+return config

tg_server/tg_server.lua

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+local fullPath = shell.getRunningProgram()
+local dir = fullPath:match("^(.*/)") or ""
+
+local config = dofile(dir..'taskguard.cfg')
+
+local clearances = { { computer_id = 1, clearance_level = 1, time_granted = os.clock() } }
+
+local function split(str, divider)
+    local t = {}
+    for part in string.gmatch(str, "([^" .. divider .. "]+)") do
+        table.insert(t, part)
+    end
+    return t
+end
+
+local function hash(str)
+    local hash = 0
+    for i = 1, #str do
+        hash = (hash * 31 + string.byte(str, i)) % 65536
+    end
+    return string.format("%04X", hash)
+end
+
+
+local function check_for_outdated_sessions()
+    local expired = 0
+    for i = #clearances, 1, -1 do
+        if (os.clock() - clearances[i].time_granted) > config.clearance_expiry then
+            table.remove(clearances, i)
+            expired = expired + 1
+        end
+    end
+    print("Removed " .. expired .. " expired clearance(s). " ..
+          #clearances .. " active session(s) remain.")
+end
+
+
+
+rednet.open(config.modem_side)
+rednet.host('tg', config.name)
+print("Server started, waiting for requests...")
+
+while true do
+    local id, msg, proto = rednet.receive('tg')
+    check_for_outdated_sessions()
+    msg_parts = split(msg, ',')
+    if msg_parts[1] == 'validate_clearance' then
+        print("Beginning transaction for clearance query with "..id)
+        local target_id = tonumber(msg_parts[2])
+        local requested_clearance = tonumber(msg_parts[3])
+        local has_clearance = false
+
+        for i, entry in ipairs(clearances) do
+            if entry.computer_id == target_id and entry.clearance_level >= requested_clearance then
+                -- Auth granted
+                rednet.send(id, 'granted', 'tg')
+                print('Finished transaction, granted')
+                has_clearance = true
+            end
+        end
+
+        if has_clearance == false then
+            -- Auth not granted
+            rednet.send(id, 'failed', 'tg')
+            print('Finished transaction, failed')
+        end
+        print("EOP")
+    elseif  msg_parts[1] == 'authenticate' then
+        print("Beginning transaction for authentication with "..id)
+        local card_holder = msg_parts[2]
+        local card_clearance = msg_parts[3]
+        local card_hash = hash(card_holder..','..card_clearance..','..msg_parts[4])
+        local key_file = fs.open(dir..config.key_file, 'r')
+        local card_authentic = false
+
+        while true do
+            local trusted_hash = key_file.readLine()
+            if trusted_hash == card_hash then
+                table.insert(clearances, { computer_id = tonumber(id), clearance_level = tonumber(card_clearance), time_granted = os.clock() })
+                rednet.send(id, "authentication successful", "tg")
+                print("Granted card "..card_hash.." clearance level "..card_clearance)
+
+                card_authentic = true
+            end
+            if not line then break end -- Stop when EOF reached
+        end
+
+        key_file.close()
+        
+        if card_authentic == false then
+            print("Unknown card "..card_hash)
+            rednet.send(id, "authentication failed", "tg")
+        end
+        print("Transaction finished")
+    end
+end

tg_server/verified_keys.txt

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+DE1A