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zapret-obfs: synhide xorseq

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bol-van
2026-01-30 18:53:22 +03:00
parent 9128601820
commit b99b59bbdb
1 changed files with 41 additions and 13 deletions
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54
lua/zapret-obfs.lua
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@@ -284,6 +284,7 @@ end
-- arg : x2=bit - th_x2 bit used for magic=x2 - 1,2,4,8
-- arg : kind - kind of tcp option for magic=opt
-- arg : opt=hex - tcp option value
-- arg : xorseq=hex - 4 hex bytes to xor seq
function synhide(ctx, desync)
if not desync.dis.tcp then
instance_cutoff_shim(ctx, desync)
@@ -341,6 +342,16 @@ function synhide(ctx, desync)
opt=""
end
local xorseq
if desync.arg.xorseq then
xorseq = parse_hex(desync.arg.xorseq)
if not xorseq or #xorseq~=4 then
error("synhide: invalid xorseq value")
end
xorseq = u32(xorseq)
end
local function make_magic(client)
local m
-- use client seq0
@@ -352,6 +363,28 @@ function synhide(ctx, desync)
end
return m
end
local function xorhdr()
if xorseq then
desync.dis.tcp.th_ack = bitxor(desync.dis.tcp.th_ack, xorseq)
desync.dis.tcp.th_seq = bitxor(desync.dis.tcp.th_seq, xorseq)
end
end
local function ver_magic(client)
local r = false
xorhdr()
if magic=="tsecr" then
r = make_magic(client)==u16(string.sub(desync.dis.tcp.options[tsidx].data,7))
elseif magic=="x2" then
r = bitand(desync.dis.tcp.th_x2, x2)~=0
elseif magic=="urp" then
r = desync.dis.tcp.th_urp == make_magic(client)
elseif magic=="opt" then
local idx = find_tcp_option(desync.dis.tcp.options, kind)
r = idx and desync.dis.tcp.options[idx].data == opt
end
xorhdr()
return r
end
local function set_magic(client)
if magic=="tsecr" then
desync.dis.tcp.options[tsidx].data = string.sub(desync.dis.tcp.options[tsidx].data,1,6) .. bu16(make_magic(client))
@@ -362,20 +395,10 @@ function synhide(ctx, desync)
elseif magic=="opt" then
table.insert(desync.dis.tcp.options, {kind=kind, data=opt})
end
end
local function ver_magic(client)
if magic=="tsecr" then
return make_magic(client)==u16(string.sub(desync.dis.tcp.options[tsidx].data,7))
elseif magic=="x2" then
return bitand(desync.dis.tcp.th_x2, x2)~=0
elseif magic=="urp" then
return desync.dis.tcp.th_urp == make_magic(client)
elseif magic=="opt" then
local idx = find_tcp_option(desync.dis.tcp.options, kind)
return idx and desync.dis.tcp.options[idx].data == opt
end
xorhdr()
end
local function clear_magic()
xorhdr()
if magic=="tsecr" then
desync.dis.tcp.options[tsidx].data = string.sub(desync.dis.tcp.options[tsidx].data,1,6) .. "\x00\x00"
elseif magic=="x2" then
@@ -424,17 +447,22 @@ function synhide(ctx, desync)
return VERDICT_MODIFY
else
DLOG("synhide: server sends SYN+ACK. do not remove SYN because 'synack' arg is not set.")
instance_cutoff_shim(ctx, desync)
return -- do nothing
end
elseif fl==TH_ACK and ver_magic(true) then
DLOG("synhide: server received magic. restore SYN")
desync.dis.tcp.th_flags = bitor(bitand(desync.dis.tcp.th_flags, bitnot(TH_ACK)), TH_SYN)
clear_magic()
if not desync.arg.synack then
DLOG("synhide: mission complete")
instance_cutoff_shim(ctx, desync)
end
return VERDICT_MODIFY
elseif fl==(TH_ACK+TH_RST) and ver_magic(false) then
-- client received
DLOG("synhide: client received magic. restore SYN, remove RST")
desync.dis.tcp.th_flags = bitor(bitand(desync.dis.tcp.th_flags, bitnot(TH_RST)), TH_SYN)
clear_magic()
DLOG("synhide: mission complete")
instance_cutoff_shim(ctx, desync)
return VERDICT_MODIFY