Implement PBKDF2 password hashing with salt for enhanced security

sys/modules/opus/security.lua

@@ -1,10 +1,38 @@
 local Config = require('opus.config')
+local SHA    = require('opus.crypto.sha2')
+local Util   = require('opus.util')
+
+local PBKDF2_ITERATIONS = 100
 
 local Security = { }
 
+local function generateSalt()
+	local salt = { }
+	for _ = 1, 16 do
+		salt[#salt + 1] = math.random(0, 0xFF)
+	end
+	return setmetatable(salt, Util.byteArrayMT):toHex()
+end
+
 function Security.verifyPassword(password)
-	local current = Security.getPassword()
-	return current and password == current
+	local stored = Security.getPassword()
+	if not stored then
+		return false
+	end
+
+	-- New format: { hash = hex, salt = hex, iter = N }
+	if type(stored) == 'table' and stored.hash and stored.salt then
+		local iter = stored.iter or PBKDF2_ITERATIONS
+		local derived = SHA.pbkdf2(password, Util.hexToByteArray(stored.salt), iter)
+		return derived:toHex() == stored.hash
+	end
+
+	-- Legacy format: plain SHA-256 hex string
+	if type(stored) == 'string' then
+		return SHA.compute(password) == stored
+	end
+
+	return false
 end
 
 function Security.hasPassword()
@@ -28,8 +56,15 @@ function Security.getIdentifier()
 end
 
 function Security.updatePassword(password)
+	local salt = generateSalt()
+	local derived = SHA.pbkdf2(password, Util.hexToByteArray(salt), PBKDF2_ITERATIONS)
+
 	local config = Config.load('os')
-	config.password = password
+	config.password = {
+		hash = derived:toHex(),
+		salt = salt,
+		iter = PBKDF2_ITERATIONS,
+	}
 	Config.update('os', config)
 end