working otp code generation

.github/workflows/test.yml

@@ -0,0 +1,20 @@
+name: test
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    strategy:
+      matrix:
+        ENGINE_VERSION: [5.3.0, 5.4.0, 5.5.0, 5.6.1, latest]
+
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+        submodules: recursive
+    - name: test
+      run: docker-compose up --exit-code-from test

docker-compose.yml

@@ -0,0 +1,15 @@
+version: "3.6"
+
+services:
+ test:
+  build: ./test
+  user: root
+  volumes:
+    - "./:/root/.minetest/worlds/world/worldmods/otp/"
+    - "./test/minetest.conf:/minetest.conf"
+    - "world:/root/.minetest/worlds/world"
+  ports:
+    - "30000:30000/udp"
+
+volumes:
+  world: {}

functions.lua

@@ -1,6 +1,6 @@
 
 -- https://stackoverflow.com/a/25594410
-function otp.bitXOR(a,b)--Bitwise xor
+local function bitxor(a,b)
     local p,c=1,0
     while a>0 and b>0 do
         local ra,rb=a%2,b%2
@@ -16,6 +16,16 @@ function otp.bitXOR(a,b)--Bitwise xor
     return c
 end
 
+local function bitor(a,b)
+    local p,c=1,0
+    while a+b>0 do
+        local ra,rb=a%2,b%2
+        if ra+rb>0 then c=c+p end
+        a,b,p=(a-ra)/2,(b-rb)/2,p*2
+    end
+    return c
+end
+
 -- https://stackoverflow.com/a/32387452
 local function bitand(a, b)
 	local result = 0
@@ -36,15 +46,20 @@ local function rshift(x, by)
 	return math.floor(x / 2 ^ by)
 end
 
-function otp.write_uint64(v)
-	local b1 = bitand(v, 0xFF)
-	local b2 = bitand( rshift(v, 8), 0xFF )
-	local b3 = bitand( rshift(v, 16), 0xFF )
-	local b4 = bitand( rshift(v, 24), 0xFF )
-	local b5 = bitand( rshift(v, 32), 0xFF )
-	local b6 = bitand( rshift(v, 40), 0xFF )
-	local b7 = bitand( rshift(v, 48), 0xFF )
-	local b8 = bitand( rshift(v, 56), 0xFF )
+local function lshift(x, by)
+    return x * 2 ^ by
+end
+
+-- big-endian uint64 of a number
+function otp.write_uint64_be(v)
+	local b1 = bitand( rshift(v, 56), 0xFF )
+	local b2 = bitand( rshift(v, 48), 0xFF )
+	local b3 = bitand( rshift(v, 40), 0xFF )
+	local b4 = bitand( rshift(v, 32), 0xFF )
+	local b5 = bitand( rshift(v, 24), 0xFF )
+	local b6 = bitand( rshift(v, 16), 0xFF )
+	local b7 = bitand( rshift(v, 8), 0xFF )
+	local b8 = bitand( rshift(v, 0), 0xFF )
 	return string.char(b1, b2, b3, b4, b5, b6, b7, b8)
 end
 
@@ -61,29 +76,49 @@ end
 function otp.hmac(key, message)
     local i_key_pad = ""
     for i=1,64 do
-        i_key_pad = i_key_pad .. string.char(otp.bitXOR(string.byte(key, i) or 0x00, string.byte(i_pad, i)))
+        i_key_pad = i_key_pad .. string.char(bitxor(string.byte(key, i) or 0x00, string.byte(i_pad, i)))
     end
+    assert(#i_key_pad == 64)
 
     local o_key_pad = ""
     for i=1,64 do
-        o_key_pad = o_key_pad .. string.char(otp.bitXOR(string.byte(key, i) or 0x00, string.byte(o_pad, i)))
+        o_key_pad = o_key_pad .. string.char(bitxor(string.byte(key, i) or 0x00, string.byte(o_pad, i)))
     end
+    assert(#o_key_pad == 64)
 
     -- concat message
     local first_msg = i_key_pad
     for i=1,#message do
-        first_msg = first_msg .. string.byte(message, i)
+        first_msg = first_msg .. string.char(string.byte(message, i))
     end
+    assert(#first_msg == 64+8)
 
     -- hash first message
     local hash_sum_1 = minetest.sha1(first_msg, true)
+    assert(#hash_sum_1 == 20)
 
     -- concat first message to secons
     local second_msg = o_key_pad
     for i=1,#hash_sum_1 do
-        second_msg = second_msg .. string.byte(hash_sum_1, i)
+        second_msg = second_msg .. string.char(string.byte(hash_sum_1, i))
     end
+    assert(#second_msg == 64+20)
 
-    -- hash final message
-    return minetest.sha1(second_msg, true)
+    local hmac = minetest.sha1(second_msg, true)
+    assert(#hmac == 20)
+
+    return hmac
+end
+
+function otp.generate_code(key, message)
+    local hmac = otp.hmac(key, message)
+
+    -- https://www.rfc-editor.org/rfc/rfc4226#section-5.4
+    local offset = bitand(string.byte(hmac, #hmac), 0xF)
+    local value = 0
+    value = bitor(value, string.byte(hmac, offset+4))
+    value = bitor(value, lshift(string.byte(hmac, offset+3), 8))
+    value = bitor(value, lshift(string.byte(hmac, offset+2), 16))
+    value = bitor(value, lshift(bitand(string.byte(hmac, offset+1), 0x7F), 24))
+    return value % 10^6
 end

functions.spec.lua

@@ -0,0 +1,43 @@
+
+
+mtt.register("otp.hmac", function(callback)
+    local secret_b32 = "N6JGKMEKU2E6HQMLLNMJKBRRGVQ2ZKV7"
+    local secret = otp.basexx.from_base32(secret_b32)
+    local unix_time = 1640995200
+
+    local expected_hmac = otp.basexx.from_base64("m04YheEb7i+ThPMUJEfVXVybZFo=")
+    assert(#expected_hmac == 20)
+
+    local tx = 30
+    local ct = math.floor(unix_time / tx)
+    local counter = otp.write_uint64_be(ct)
+
+    assert( #secret == 20 )
+    assert( otp.basexx.to_base64(secret) == "b5JlMIqmiePBi1tYlQYxNWGsqr8=" )
+    assert( #counter == 8 )
+    assert( otp.basexx.to_base64(counter) == "AAAAAANCp0A=" )
+
+    local hmac = otp.hmac(secret, counter)
+    assert(#hmac == 20)
+
+    for i=1,20 do
+        assert( string.byte(expected_hmac,i) == string.byte(hmac, i) )
+    end
+
+    callback()
+end)
+
+mtt.register("otp.generate_code", function(callback)
+    local expected_code = 699847
+    local secret_b32 = "N6JGKMEKU2E6HQMLLNMJKBRRGVQ2ZKV7"
+    local secret = otp.basexx.from_base32(secret_b32)
+    local unix_time = 1640995200
+
+    local tx = 30
+    local ct = math.floor(unix_time / tx)
+    local counter = otp.write_uint64_be(ct)
+
+    local code = otp.generate_code(secret, counter)
+    assert(code == expected_code)
+    callback()
+end)

init.lua

@@ -9,4 +9,7 @@ otp = {
 }
 
 dofile(MP.."/functions.lua")
-dofile(MP.."/test.lua")
+
+if minetest.get_modpath("mtt") and mtt.enabled then
+    dofile(MP.."/functions.spec.lua")
+end

mod.conf

@@ -1 +1,2 @@
 name = otp
+optional_depends = mtt

test.lua

@@ -1,24 +0,0 @@
-local secret_b32 = "N6JGKMEKU2E6HQMLLNMJKBRRGVQ2ZKV7"
-local expected_code = 699847
-
-minetest.register_chatcommand("otp_test", {
-    description = "",
-    params = "[]",
-	func = function(name, param)
-        local secret = otp.basexx.from_base32(secret_b32)
-        local unix_time = 1640995200
-        local tx = 30
-        local ct = math.floor(unix_time / tx)
-
-        local hmac = otp.hmac(secret, otp.write_uint64(ct))
-
-
-
-        print(dump({
-            expected_code = expected_code,
-            unix_time = unix_time,
-            ct = ct,
-            hmac = otp.basexx.to_base64(hmac)
-        }))
-	end
-})

test/Dockerfile

@@ -0,0 +1,11 @@
+ARG ENGINE_VERSION=5.6.1
+FROM registry.gitlab.com/minetest/minetest/server:${ENGINE_VERSION}
+
+USER root
+
+RUN apk add git &&\
+    mkdir -p /root/.minetest/worlds/world/worldmods/ &&\
+    cd /root/.minetest/worlds/world/worldmods/ &&\
+    git clone https://github.com/BuckarooBanzay/mtt
+
+ENTRYPOINT minetestserver --config /minetest.conf

test/minetest.conf

@@ -0,0 +1,3 @@
+default_game = minetest_game
+mg_name = v7
+mtt_enable = true