From 238058e46fd5111631e2097e111bb4fb7e0db157 Mon Sep 17 00:00:00 2001
From: Miguel Oliveira <miguel.oliveira4224@gmail.com>
Date: Sat, 5 Mar 2022 12:24:33 -0300
Subject: [PATCH] Add Poly1305 tag verification

---
 poly1305.lua | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/poly1305.lua b/poly1305.lua
index db788d3..c849afb 100644
--- a/poly1305.lua
+++ b/poly1305.lua
@@ -4,6 +4,7 @@
 --
 
 local expect = require "cc.expect".expect
+local random = require "ccryptolib.random"
 
 local band = bit32.band
 
@@ -134,4 +135,18 @@ function mod.mac(key, message)
     return ("<I2I3I3I2I3I3"):pack(t0, t1, t2, t3, t4, t5)
 end
 
+local mac = mod.mac
+
+--- Verifies a Poly1305 tag.
+--
+-- @tparam string key The key used to generate the tag.
+-- @tparam string message The message to authenticate.
+-- @tparam string tag The tag to check.
+-- @treturn boolean Whether the tag is valid or not.
+--
+function mod.verify(key, message, tag)
+    local kaux = random.random(32)
+    return mac(kaux, tag) == mac(kaux, mac(key, message))
+end
+
 return mod