1 files changed, 70 insertions, 0 deletions
diff --git a/util/hmac.lua b/util/hmac.lua
new file mode 100644
index 00000000..5f4467cf
--- /dev/null
+++ b/util/hmac.lua
@@ -0,0 +1,70 @@
+local hashes = require "util.hashes"
+local xor = require "bit".bxor
+
+local t_insert, t_concat = table.insert, table.concat;
+local s_char = string.char;
+
+module "hmac"
+
+local function arraystr(array)
+    local t = {}
+    for i = 1,#array do
+        t_insert(t, s_char(array[i]))
+    end
+
+    return t_concat(t)
+end
+
+--[[
+key
+    the key to use in the hash
+message
+    the message to hash
+hash
+    the hash function
+blocksize
+    the blocksize for the hash function in bytes
+hex
+  return raw hash or hexadecimal string
+--]]
+function hmac(key, message, hash, blocksize, hex)
+    local opad = {}
+    local ipad = {}
+    
+    for i = 1,blocksize do
+        opad[i] = 0x5c
+        ipad[i] = 0x36
+    end
+
+    if #key > blocksize then
+        key = hash(key)
+    end
+
+    for i = 1,#key do
+        ipad[i] = xor(ipad[i],key:sub(i,i):byte())
+        opad[i] = xor(opad[i],key:sub(i,i):byte())
+    end
+
+    opad = arraystr(opad)
+    ipad = arraystr(ipad)
+
+    if hex then
+        return hash(opad..hash(ipad..message), true)
+    else
+        return hash(opad..hash(ipad..message))
+    end
+end
+
+function md5(key, message, hex)
+    return hmac(key, message, hashes.md5, 64, hex)
+end
+
+function sha1(key, message, hex)
+    return hmac(key, message, hashes.sha1, 64, hex)
+end
+
+function sha256(key, message, hex)
+    return hmac(key, message, hashes.sha256, 64, hex)
+end
+
+return _M