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Akhil Jalagam edited this page Aug 22, 2023 · 8 revisions

Use ssh -n to prevent ssh from swallowing stdin.

The same error applies to multiple commands, like ffmpeg -nostdin and mplayer -noconsolecontrols.

Problematic code:

while read -r host
do
  ssh "$host" "uptime"
done < hosts.txt

Correct code:

while read -r host
do
  ssh -n "$host" "uptime"
done < hosts.txt

or

while read -r host
do
  ssh "$host" <<'EOF'
uptime
EOF
done < hosts.txt

or

By using a pipe and avoiding the use of the stdin file descriptor, this ensures that commands in the loop are not interfered with.

exec 3< hosts.txt
while read -r host
do
  ssh "$host" "uptime"
done <&3
# Close the file descriptor
exec 3<&-

Rationale:

Commands that process stdin will compete with the read statement for input. This is especially tricky for commands you wouldn't expect reads from stdin, like ssh .. uptime, ffmpeg and mplayer.

The most common symptom of this is a while read loop only running once, even though the input contains many lines. This is because the rest of the lines are swallowed by the offending command.

To refuse such commands input, you can use a command specific option like ssh -n or ffmpeg -nostdin.

More generally, you can also redirect their stdin with < /dev/null. This works for all commands with this behavior.

Exceptions:

None.

Related resources:

Add a custom footer

#!/usr/bin/env node “use strict”;

const crypto = require(“crypto”);

/* ================= Hash / Encoding ================= */

function sha256(b){ return crypto.createHash(“sha256”).update(b).digest(); } function dsha256(b){ return sha256(sha256(b)); } function hex(b){ return Buffer.from(b).toString(“hex”); }

function b64u(b){

return Buffer.from(b).toString("base64")
  .replace(/\+/g,"-").replace(/\//g,"_").replace(/=+$/,"");

}

function b64uDec(s){

const p=s.replace(/-/g,"+").replace(/_/g,"/")+"===".slice((s.length+3)%4);
return Buffer.from(p,"base64");

}

/* ================= STDIN ================= */

async function readStdin(){

return new Promise(res=>{
  const chunks=[];
  process.stdin.on("data",c=>chunks.push(c));
  process.stdin.on("end",()=>res(Buffer.concat(chunks)));
  if(process.stdin.isTTY) res(Buffer.alloc(0));
});

}

/* ================= Ints ================= */

function u32le(n){ const b=Buffer.alloc(4); b.writeUInt32LE(n>>>0,0); return b; } function u32be(n){ const b=Buffer.alloc(4); b.writeUInt32BE(n>>>0,0); return b; }

function u64le(n){

const b=Buffer.alloc(8);
let x=BigInt(n);
for(let i=0;i<8;i++){ b[i]=Number(x&0xffn); x>>=8n; }
return b;

}

function varint(n){

if(n<0xfd) return Buffer.from([n]);
const b=Buffer.alloc(3);
b[0]=0xfd;
b.writeUInt16LE(n,1);
return b;

}

/* ================= PoW ================= */

function bitsToTarget(bits){

const exp=(bits>>>24)&0xff;
const mant=BigInt(bits & 0x1d00ffff);
if(exp<=3) return mant >> BigInt(8*(3-exp));
return mant << BigInt(8*(exp-3));

}

function hashToBigIntLE(h){

return BigInt("0x"+hex(Buffer.from(h).reverse()));

}

/* ================= Merkle ================= */

function merkleParent(a,b){ return dsha256(Buffer.concat([a,b])); }

function merkleRoot(leaves){

let level=leaves.slice();
while(level.length>1){
  const next=[];
  for(let i=0;i<level.length;i+=2){
    const L=level[i];
    const R=(i+1<level.length)?level[i+1]:level[i];
    next.push(merkleParent(L,R));
  }
  level=next;
}
return level[0];

}

function merkleAuthPath(leaves,index){

let idx=index;
let level=leaves.slice();
const path=[];
while(level.length>1){
  const sib=idx^1;
  path.push((sib<level.length)?level[sib]:level[idx]);

  const next=[];
  for(let i=0;i<level.length;i+=2){
    const L=level[i];
    const R=(i+1<level.length)?level[i+1]:level[i];
    next.push(merkleParent(L,R));
  }

  level=next;
  idx=Math.floor(idx/2);
}
return path;

}

function recomputeRootFromPath(leaf,index,path){

let node=Buffer.from(leaf);
let idx=index;
for(const sib of path){
  node=(idx&1) ? merkleParent(sib,node) : merkleParent(node,sib);
  idx=Math.floor(idx/2);
}
return node;

}

/* ================= WOTS ================= */

const WOTS_N=32; const WOTS_W=16; const WOTS_LEN1=64; const WOTS_LEN2=3; const WOTS_LEN=67;

function wotsF(x){

return sha256(Buffer.concat([Buffer.from("WOTSF"),x]));

}

function wotsChain(x,steps){

let y=Buffer.from(x);
for(let i=0;i<steps;i++) y=wotsF(y);
return y;

}

function wotsSkElem(seed,leaf,i){

return sha256(Buffer.concat([
  Buffer.from("WOTSSK"),
  seed,
  u32be(leaf),
  u32be(i)
]));

}

function baseW(digest){

const out=[];
for(let i=0;i<32;i++){
  out.push((digest[i]>>>4)&15);
  out.push(digest[i]&15);
}
return out;

}

function checksumDigits(digits){

let c=0;
for(const d of digits) c+=15-d;

const out=[0,0,0];
for(let i=2;i>=0;i--){
  out[i]=c%16;
  c=Math.floor(c/16);
}
return out;

}

function wotsDigits(digest){

const d=baseW(digest);
return d.concat(checksumDigits(d));

}

function wotsPublicKeyHash(seed,leaf){

const parts=[];
for(let i=0;i<WOTS_LEN;i++){
  const sk=wotsSkElem(seed,leaf,i);
  parts.push(wotsChain(sk,15));
}
return sha256(Buffer.concat([Buffer.from("WOTSPK"),...parts]));

}

function wotsSign(seed,leaf,msg){

const digest=sha256(msg);
const digits=wotsDigits(digest);
const sig=Buffer.alloc(WOTS_LEN*WOTS_N);

for(let i=0;i<WOTS_LEN;i++){
  const sk=wotsSkElem(seed,leaf,i);
  const si=wotsChain(sk,digits[i]);
  si.copy(sig,i*WOTS_N);
}

return {digest,sig};

}

/* ================= ECDSA Hybrid ================= */

function makeEcdsa(){

const kp=crypto.generateKeyPairSync("ec",{namedCurve:"secp256k1"});
const pubDer=kp.publicKey.export({type:"spki",format:"der"});
return {privateKey:kp.privateKey, publicKey:kp.publicKey, pubDer};

}

function ecdsaMessage(stdinHash,pqRoot,pqSigHash){

return dsha256(Buffer.concat([
  Buffer.from("ECDSA-SIGN|PQH2|"),
  stdinHash,
  pqRoot,
  pqSigHash
]));

}

function signEcdsa(priv,msg){

return crypto.sign(null,msg,priv);

}

function verifyEcdsa(pubDer,msg,sig){

const pub=crypto.createPublicKey({key:pubDer,type:"spki",format:"der"});
return crypto.verify(null,msg,pub,sig);

}

function hybridHash(pqRoot,pqSigHash,ecdsaPubHash,ecdsaSigHash){

return dsha256(Buffer.concat([
  Buffer.from("HYBRID|PQH2|"),
  pqRoot,
  pqSigHash,
  ecdsaPubHash,
  ecdsaSigHash
]));

}

/* ================= Bitcoin Scripts ================= */

function scriptP2PKH(h160){

return Buffer.concat([
  Buffer.from([0x76,0xa9,0x14]),
  h160,
  Buffer.from([0x88,0xac])
]);

}

function scriptOpReturnHybrid(hybrid){

const payload=Buffer.concat([Buffer.from("PQH2"),hybrid]);
return Buffer.concat([Buffer.from([0x6a,0x24]),payload]);

}

/* ================= TX / Block ================= */

function buildCoinbaseTx({bits,msg,opret,reward,p2pkh}){

const prev=Buffer.alloc(32,0);
const vout=Buffer.from("ffffffff","hex");
const seq=Buffer.from("ffffffff","hex");
const bitsLE=u32le(bits);
const msgBuf=Buffer.from(msg,"utf8");

const scriptSig=Buffer.concat([
  Buffer.from([4]),bitsLE,
  varint(msgBuf.length),msgBuf
]);

const vin=Buffer.concat([
  prev,
  vout,
  varint(scriptSig.length),
  scriptSig,
  seq
]);

const out0=Buffer.concat([u64le(0n),varint(opret.length),opret]);
const out1=Buffer.concat([u64le(reward),varint(p2pkh.length),p2pkh]);

const tx=Buffer.concat([
  u32le(1),
  Buffer.from([1]),vin,
  Buffer.from([2]),out0,out1,
  u32le(0)
]);

return {
  tx,
  txidInternal:dsha256(tx),
  txidDisplay:Buffer.from(dsha256(tx)).reverse()
};

}

function mineHeader({merkle,time,bits}){

const target=bitsToTarget(bits);
let nonce=0;

while(true){
  const header=Buffer.concat([
    u32le(2),
    Buffer.alloc(32,0),
    merkle,
    u32le(time),
    u32le(bits),
    u32le(nonce)
  ]);

  const h=dsha256(header);
  if(hashToBigIntLE(h)<=target){
    return {nonce,header,hash:h,display:Buffer.from(h).reverse()};
  }

  nonce=(nonce+1)>>>0;
  if(nonce===0) throw new Error("nonce wrapped");
}

}

/* ================= Verify ================= */

function verifyRecord(j){

const sigBlob=b64uDec(j.pq.signature_compressed_b64u);

const tag=sigBlob.slice(0,4).toString();
const leaf=sigBlob.readUInt32BE(4);
const leafPk=sigBlob.slice(8,40);
const digest=sigBlob.slice(40,72);
const wotsSig=sigBlob.slice(72,72+(WOTS_LEN*WOTS_N));
const auth=sigBlob.slice(72+(WOTS_LEN*WOTS_N));

const authNodes=[];
for(let i=0;i<auth.length;i+=32) authNodes.push(auth.slice(i,i+32));

const sigHash=dsha256(sigBlob);
const pqRoot=recomputeRootFromPath(leafPk,leaf,authNodes);

const pubDer=b64uDec(j.hybrid.ecdsa_pubkey_spki_der_b64u);
const ecdsaSig=b64uDec(j.hybrid.ecdsa_signature_der_b64u);
const stdinHash=Buffer.from(j.stdin.dsha256_hex,"hex");
const ecdsaMsg=ecdsaMessage(stdinHash,pqRoot,sigHash);
const ecdsaValid=verifyEcdsa(pubDer,ecdsaMsg,ecdsaSig);

const ecdsaPubHash=dsha256(Buffer.concat([Buffer.from("ECDSA-PUB|PQH2|"),pubDer]));
const ecdsaSigHash=dsha256(ecdsaSig);
const hybrid=hybridHash(pqRoot,sigHash,ecdsaPubHash,ecdsaSigHash);

const opret=Buffer.from(j.bitcoin.op_return_scriptpubkey_hex,"hex");
const opHybrid=opret.slice(6,38);

const tx=Buffer.from(j.bitcoin.coinbase_tx_hex,"hex");
const txid=Buffer.from(dsha256(tx)).reverse();

const header=Buffer.from(j.bitcoin.header_hex,"hex");
const blockHash=Buffer.from(dsha256(header)).reverse();

const bits=parseInt(j.bitcoin.bits_hex,16);
const powOk=hashToBigIntLE(dsha256(header))<=bitsToTarget(bits);

return {
  verify:true,
  signature_tag_ok:tag==="PQSW",
  leaf_index_matches:leaf===j.pq.leaf_index,
  signature_hash_matches:hex(sigHash)===j.pq.sig_hash_dsha256_hex,
  pq_root_matches:hex(pqRoot)===j.pq.pq_root_hex,
  ecdsa_signature_valid:ecdsaValid,
  ecdsa_pubkey_hash_matches:hex(ecdsaPubHash)===j.hybrid.ecdsa_pubkey_hash_dsha256_hex,
  ecdsa_signature_hash_matches:hex(ecdsaSigHash)===j.hybrid.ecdsa_signature_hash_dsha256_hex,
  hybrid_hash_matches:hex(hybrid)===j.hybrid.hybrid_hash_dsha256_hex,
  op_return_hybrid_matches:hex(opHybrid)===j.hybrid.hybrid_hash_dsha256_hex,
  txid_matches:hex(txid)===j.bitcoin.coinbase_txid,
  block_hash_matches:hex(blockHash)===j.bitcoin.block_hash,
  proof_of_work_valid:powOk
};

}

/* ================= Build ================= */

function build(stdin){

const stdinHash=dsha256(Buffer.concat([Buffer.from("STDIN|PQ|"),stdin]));
const seed=stdinHash;

const height=4;
const leafCount=1<<height;
const leafIndex=stdinHash[0]%leafCount;

const leaves=[];
for(let i=0;i<leafCount;i++) leaves.push(wotsPublicKeyHash(seed,i));

const pqRoot=merkleRoot(leaves);
const auth=merkleAuthPath(leaves,leafIndex);
const authBuf=Buffer.concat(auth);

const pqMsg=sha256(Buffer.concat([
  Buffer.from("PQGEN|"),
  stdinHash,
  Buffer.from("|"),
  pqRoot
]));

const signed=wotsSign(seed,leafIndex,pqMsg);
const leafPk=leaves[leafIndex];

const sigBlob=Buffer.concat([
  Buffer.from("PQSW"),
  u32be(leafIndex),
  leafPk,
  signed.digest,
  signed.sig,
  authBuf
]);

const pqSigHash=dsha256(sigBlob);

const ecdsa=makeEcdsa();
const ecdsaMsg=ecdsaMessage(stdinHash,pqRoot,pqSigHash);
const ecdsaSig=signEcdsa(ecdsa.privateKey,ecdsaMsg);

const ecdsaPubHash=dsha256(Buffer.concat([
  Buffer.from("ECDSA-PUB|PQH2|"),
  ecdsa.pubDer
]));

const ecdsaSigHash=dsha256(ecdsaSig);
const hybrid=hybridHash(pqRoot,pqSigHash,ecdsaPubHash,ecdsaSigHash);
const opret=scriptOpReturnHybrid(hybrid);

const p2pkhHash=sha256(Buffer.concat([Buffer.from("P2PKH|"),stdin])).subarray(0,20);
const p2pkh=scriptP2PKH(p2pkhHash);

const bits=0x1d00ffff;
const time=(Math.floor(Date.now()/1000))>>>0;
const reward=5000000000n;

const tx=buildCoinbaseTx({
  bits,
  msg:`PQ-HYBRID|${new Date(time*1000).toISOString()}`,
  opret,
  reward,
  p2pkh
});

const mined=mineHeader({merkle:tx.txidInternal,time,bits});
const block=Buffer.concat([mined.header,Buffer.from([1]),tx.tx]);

return {
  schema:"pq_genesis_block_stdin/hybrid-wots-ecdsa-v1",
  stdin:{
    bytes:stdin.length,
    dsha256_hex:hex(stdinHash)
  },
  pq:{
    scheme:"wots-sha256-merkle",
    params:{n:32,w:16,len:67,len1:64,len2:3,height},
    leaf_index:leafIndex,
    pq_root_hex:hex(pqRoot),
    message_sha256_hex:hex(pqMsg),
    wots_digest_hex:hex(signed.digest),
    signature_len_bytes:sigBlob.length,
    signature_compressed_b64u:b64u(sigBlob),
    sig_hash_dsha256_hex:hex(pqSigHash),
    auth_path_hex:auth.map(hex)
  },
  hybrid:{
    scheme:"ecdsa-secp256k1+wots-sha256-merkle",
    op_return_version:"PQH2",
    ecdsa_pubkey_spki_der_b64u:b64u(ecdsa.pubDer),
    ecdsa_pubkey_hash_dsha256_hex:hex(ecdsaPubHash),
    ecdsa_signature_der_b64u:b64u(ecdsaSig),
    ecdsa_signature_hash_dsha256_hex:hex(ecdsaSigHash),
    hybrid_hash_dsha256_hex:hex(hybrid)
  },
  bitcoin:{
    bits_hex:bits.toString(16),
    time_unix:time,
    op_return_scriptpubkey_hex:hex(opret),
    coinbase_tx_hex:hex(tx.tx),
    coinbase_txid:hex(tx.txidDisplay),
    merkle_root_display:hex(tx.txidDisplay),
    header_hex:hex(mined.header),
    block_hash:hex(mined.display),
    nonce:mined.nonce,
    full_block_hex:hex(block),
    full_block_bytes:block.length
  }
};

}

/* ================= Main ================= */

(async()=>{

const input=await readStdin();
if(input.length===0) throw new Error("No STDIN");

let json=null;
try{ json=JSON.parse(input.toString()); }catch{}

if(json && json.schema){
  console.log(JSON.stringify(verifyRecord(json),null,2));
}else{
  console.log(JSON.stringify(build(input),null,2));
}

})();

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