Fix math.random polyfill and unseeded random seed generation

src/prometheus.lua

@@ -20,7 +20,7 @@ if not pcall(function()
 end) then
     local oldMathRandom = math.random;
     math.random = function(a, b)
-        if not a and b then
+        if not a then
             return oldMathRandom();
         end
         if not b then

src/prometheus/pipeline.lua

@@ -166,19 +166,37 @@ function Pipeline:apply(code, filename)
 	else
 		--> use secure random number generator
 		local success, seed = pcall(function()
-			local seedStr =  io.popen("openssl rand -hex 12"):read("*a"):gsub("\n", "")..""
+			if not io or not io.popen then
+				error("io.popen is unavailable")
+			end
+			local handle = io.popen("openssl rand -hex 12")
+			if not handle then
+				error("Failed to execute openssl")
+			end
+			local seedStr = handle:read("*a")
+			local ok = handle:close()
+			if ok == false or ok == nil then
+				error("openssl command failed")
+			end
+			if not seedStr then
+				error("Failed to read from openssl")
+			end
+			seedStr = seedStr:gsub("%s+", "")
+			if #seedStr ~= 24 or not seedStr:match("^%x+$") then
+				error("Invalid openssl output")
+			end
+
 			local seedNum = 0;
 
-			--> NOTE: tonumber caps at 1.844674407371e+19. So we use this instead.
+			--> NOTE: accumulate modulo 2147483647 so it fits in signed 32-bit integer without double overflow
 			for i = 1, #seedStr do
 				local char = seedStr:sub(i, i):lower()
 				local digit = char:match("%d") and (char:byte() - 48) or (char:byte() - 87)
-				seedNum = seedNum * 16 + digit
+				seedNum = (seedNum * 16 + digit) % 2147483647
 			end
 
-			--> Random Number Generator in Lua 5.1 is limited to 9.007199254741e+15.
-			if _VERSION == "Lua 5.1" and not jit then
-				seedNum = seedNum % 9.007199254741e+15
+			if seedNum == 0 then
+				seedNum = 1
 			end
 
 			return seedNum
@@ -188,7 +206,13 @@ function Pipeline:apply(code, filename)
 			math.randomseed(seed)
 		else
 			logger:warn("OpenSSL is unavailable. Falling back to unix time.");
-			math.randomseed(os.time())
+			local now = (os and os.time) and os.time() or 1
+			local clock = (os and os.clock) and math.floor(os.clock() * 1000000) or 0
+			local fallback = (now + clock) % 2147483647
+			if fallback == 0 then
+				fallback = 1
+			end
+			math.randomseed(fallback)
 		end
 	end
 

tests/harness/random-seed.lua

@@ -0,0 +1,85 @@
+-- @runtime lua51 luajit
+require("src.prometheus")
+local Prometheus = require("src.prometheus")
+Prometheus.Logger.logLevel = Prometheus.Logger.LogLevel.Error
+
+local loadstring = loadstring or load
+
+-- 1. Verify math.random() polyfill behavior
+for i = 1, 20 do
+	local val = math.random()
+	assert(type(val) == "number", "math.random() must return a number")
+	assert(val >= 0 and val < 1, "math.random() must be in [0, 1), got " .. tostring(val))
+end
+
+local intVal = math.random(10)
+assert(intVal >= 1 and intVal <= 10 and intVal == math.floor(intVal), "math.random(10) out of range")
+
+local rangeVal = math.random(5, 15)
+assert(rangeVal >= 5 and rangeVal <= 15 and rangeVal == math.floor(rangeVal), "math.random(5, 15) out of range")
+
+local largeVal = math.random(1, 2^40)
+assert(largeVal >= 1 and largeVal <= 2^40, "math.random(1, 2^40) out of range")
+
+-- 2. Verify deterministic pipeline with explicit seed
+local code = 'local a = 10; local b = 20; return a + b'
+local configDeterministic = {
+	LuaVersion = "Lua51",
+	Seed = 12345,
+	NameGenerator = "Mangled",
+	Steps = {
+		{ Name = "Vmify" },
+		{ Name = "EncryptStrings" },
+		{ Name = "ConstantArray" },
+	}
+}
+
+local pipe1 = Prometheus.Pipeline:fromConfig(configDeterministic)
+local out1 = pipe1:apply(code, "test.lua")
+local pipe2 = Prometheus.Pipeline:fromConfig(configDeterministic)
+local out2 = pipe2:apply(code, "test.lua")
+
+assert(out1 == out2, "Configured seed must produce deterministic identical output")
+local res1 = assert(loadstring(out1))()
+assert(res1 == 30, "Obfuscated code with fixed seed must execute correctly, got " .. tostring(res1))
+
+-- 3. Verify non-deterministic pipeline without configured seed (Seed = 0)
+local configRandom = {
+	LuaVersion = "Lua51",
+	Seed = 0,
+	Steps = {
+		{ Name = "Vmify" },
+		{ Name = "EncryptStrings" },
+		{ Name = "ConstantArray" },
+	}
+}
+
+local randomOutputs = {}
+for i = 1, 5 do
+	local p = Prometheus.Pipeline:fromConfig(configRandom)
+	local o = p:apply(code, "test.lua")
+	local res = assert(loadstring(o))()
+	assert(res == 30, "Obfuscated code with random seed must execute correctly")
+	randomOutputs[i] = o
+end
+
+local hasDifference = false
+for i = 2, 5 do
+	if randomOutputs[i] ~= randomOutputs[1] then
+		hasDifference = true
+		break
+	end
+end
+assert(hasDifference, "Repeated runs without configured seed must produce different outputs")
+
+-- 4. Verify fallback path when OpenSSL / io.popen is unavailable
+local savedPopen = io.popen
+io.popen = nil
+local pFallback = Prometheus.Pipeline:fromConfig(configRandom)
+local oFallback = pFallback:apply(code, "fallback.lua")
+io.popen = savedPopen
+
+local resFallback = assert(loadstring(oFallback))()
+assert(resFallback == 30, "Fallback obfuscation must execute correctly")
+
+print("Random seed and math.random regression checks passed")