fediauth/functions.lua
BuckarooBanzay 02f90efcaa qr code gen
2023-01-28 19:37:27 +01:00

166 lines
4.3 KiB
Lua

-- https://stackoverflow.com/a/25594410
local function bitxor(a,b)
local p,c=1,0
while a>0 and b>0 do
local ra,rb=a%2,b%2
if ra~=rb then c=c+p end
a,b,p=(a-ra)/2,(b-rb)/2,p*2
end
if a<b then a=b end
while a>0 do
local ra=a%2
if ra>0 then c=c+p end
a,p=(a-ra)/2,p*2
end
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
local bitval = 1
while a > 0 and b > 0 do
if a % 2 == 1 and b % 2 == 1 then -- test the rightmost bits
result = result + bitval -- set the current bit
end
bitval = bitval * 2 -- shift left
a = math.floor(a/2) -- shift right
b = math.floor(b/2)
end
return result
end
-- https://gist.github.com/mebens/938502
local function rshift(x, by)
return math.floor(x / 2 ^ by)
end
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
-- prepare paddings
-- https://en.wikipedia.org/wiki/HMAC
local i_pad = ""
local o_pad = ""
for _=1,64 do
i_pad = i_pad .. string.char(0x36)
o_pad = o_pad .. string.char(0x5c)
end
-- hmac generation
function otp.hmac(key, message)
local i_key_pad = ""
for i=1,64 do
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(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.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 second
local second_msg = o_key_pad
for i=1,#hash_sum_1 do
second_msg = second_msg .. string.char(string.byte(hash_sum_1, i))
end
assert(#second_msg == 64+20)
local hmac = minetest.sha1(second_msg, true)
assert(#hmac == 20)
return hmac
end
local function left_pad(str, s, len)
while #str < len do
str = s .. str
end
return str
end
function otp.generate_totp(key, unix_time)
unix_time = unix_time or os.time()
local tx = 30
local ct = math.floor(unix_time / tx)
local counter = otp.write_uint64_be(ct)
local valid_seconds = ((ct * tx) + tx) - unix_time
local hmac = otp.hmac(key, counter)
-- 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))
local code = value % 10^6
local padded_code = left_pad("" .. code, "0", 6)
return padded_code, valid_seconds
end
function otp.create_qr_png(data)
local pixel_size = 3
local height = pixel_size * #data
local width = height
local png_data = {}
for _, row in ipairs(data) do
assert(#row == #data)
for _=1,pixel_size do
for _, v in ipairs(row) do
for _=1,pixel_size do
if v > 0 then
table.insert(png_data, 0xFF000000)
else
table.insert(png_data, 0xFFFFFFFF)
end
end
end
end
end
assert(#png_data == width*height)
return minetest.encode_png(width, height, png_data, 2)
end