124 lines
3.2 KiB
Lua
124 lines
3.2 KiB
Lua
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-- https://stackoverflow.com/a/25594410
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local function bitxor(a,b)
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local p,c=1,0
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while a>0 and b>0 do
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local ra,rb=a%2,b%2
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if ra~=rb then c=c+p end
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a,b,p=(a-ra)/2,(b-rb)/2,p*2
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end
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if a<b then a=b end
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while a>0 do
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local ra=a%2
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if ra>0 then c=c+p end
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a,p=(a-ra)/2,p*2
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end
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return c
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end
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local function bitor(a,b)
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local p,c=1,0
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while a+b>0 do
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local ra,rb=a%2,b%2
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if ra+rb>0 then c=c+p end
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a,b,p=(a-ra)/2,(b-rb)/2,p*2
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end
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return c
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end
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-- https://stackoverflow.com/a/32387452
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local function bitand(a, b)
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local result = 0
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local bitval = 1
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while a > 0 and b > 0 do
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if a % 2 == 1 and b % 2 == 1 then -- test the rightmost bits
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result = result + bitval -- set the current bit
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end
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bitval = bitval * 2 -- shift left
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a = math.floor(a/2) -- shift right
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b = math.floor(b/2)
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end
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return result
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end
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-- https://gist.github.com/mebens/938502
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local function rshift(x, by)
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return math.floor(x / 2 ^ by)
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end
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local function lshift(x, by)
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return x * 2 ^ by
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end
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-- big-endian uint64 of a number
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function otp.write_uint64_be(v)
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local b1 = bitand( rshift(v, 56), 0xFF )
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local b2 = bitand( rshift(v, 48), 0xFF )
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local b3 = bitand( rshift(v, 40), 0xFF )
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local b4 = bitand( rshift(v, 32), 0xFF )
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local b5 = bitand( rshift(v, 24), 0xFF )
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local b6 = bitand( rshift(v, 16), 0xFF )
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local b7 = bitand( rshift(v, 8), 0xFF )
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local b8 = bitand( rshift(v, 0), 0xFF )
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return string.char(b1, b2, b3, b4, b5, b6, b7, b8)
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end
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-- prepare paddings
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-- https://en.wikipedia.org/wiki/HMAC
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local i_pad = ""
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local o_pad = ""
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for _=1,64 do
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i_pad = i_pad .. string.char(0x36)
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o_pad = o_pad .. string.char(0x5c)
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end
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-- hmac generation
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function otp.hmac(key, message)
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local i_key_pad = ""
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for i=1,64 do
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i_key_pad = i_key_pad .. string.char(bitxor(string.byte(key, i) or 0x00, string.byte(i_pad, i)))
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end
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assert(#i_key_pad == 64)
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local o_key_pad = ""
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for i=1,64 do
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o_key_pad = o_key_pad .. string.char(bitxor(string.byte(key, i) or 0x00, string.byte(o_pad, i)))
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end
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assert(#o_key_pad == 64)
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-- concat message
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local first_msg = i_key_pad
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for i=1,#message do
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first_msg = first_msg .. string.char(string.byte(message, i))
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end
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assert(#first_msg == 64+8)
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-- hash first message
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local hash_sum_1 = minetest.sha1(first_msg, true)
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assert(#hash_sum_1 == 20)
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-- concat first message to second
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local second_msg = o_key_pad
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for i=1,#hash_sum_1 do
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second_msg = second_msg .. string.char(string.byte(hash_sum_1, i))
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end
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assert(#second_msg == 64+20)
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local hmac = minetest.sha1(second_msg, true)
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assert(#hmac == 20)
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return hmac
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end
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function otp.generate_code(key, message)
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local hmac = otp.hmac(key, message)
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-- https://www.rfc-editor.org/rfc/rfc4226#section-5.4
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local offset = bitand(string.byte(hmac, #hmac), 0xF)
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local value = 0
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value = bitor(value, string.byte(hmac, offset+4))
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value = bitor(value, lshift(string.byte(hmac, offset+3), 8))
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value = bitor(value, lshift(string.byte(hmac, offset+2), 16))
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value = bitor(value, lshift(bitand(string.byte(hmac, offset+1), 0x7F), 24))
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return value % 10^6
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end |