1import { randomBytes, createPrivateKey, createPublicKey, createHash } from 'crypto'
2import fs from 'fs'
3import { pathDownJoin } from '../../../serverF/pathF.mts'
4import { secretsDir } from '../../../serverF/secretsDirF.mts'
5import { assertExists } from '../../../serverF/assertsF/assertExistsF.mts'
6
7const pkcs8Ed25519Prefix = Buffer.from('302e020100300506032b657004220420', 'hex')
8const secKeyTag = Buffer.concat([Buffer.from('== ed25519v1-secret: type0 =='), Buffer.alloc(3)])
9const b32Charset = 'abcdefghijklmnopqrstuvwxyz234567'
10
11export const deriveEd25519Pubkey = (seed: Buffer): Buffer => {
12  const pkcs8 = Buffer.concat([pkcs8Ed25519Prefix, seed])
13  const priv = createPrivateKey({key: pkcs8, format: 'der', type: 'pkcs8'})
14  const spki = createPublicKey(priv).export({type: 'spki', format: 'der'}) as Buffer
15  return spki.subarray(12)
16}
17
18export const base32LowerNoPad = (buf: Buffer): string => {
19  let bits = 0, val = 0, out = ''
20  for (const b of buf) {
21    val = (val << 8) | b
22    bits += 8
23    while (bits >= 5) {
24      out += b32Charset[(val >> (bits - 5)) & 31]
25      bits -= 5
26    }
27  }
28  if (bits > 0) out += b32Charset[(val << (5 - bits)) & 31]
29  return out
30}
31
32export const deriveOnionAddr = (pubkey: Buffer): string => {
33  const version = 3
34  const checksum = createHash('sha3-256')
35    .update(Buffer.concat([Buffer.from('.onion checksum'), pubkey, Buffer.from([version])]))
36    .digest().subarray(0, 2)
37  return base32LowerNoPad(Buffer.concat([pubkey, checksum, Buffer.from([version])])) + '.onion'
38}
39
40export const buildTorSecKeyFile = (seed: Buffer): Buffer => {
41  const h = Buffer.from(createHash('sha512').update(seed).digest())
42  h[0] &= 248
43  h[31] &= 127
44  h[31] |= 64
45  return Buffer.concat([secKeyTag, h])
46}
47
48export const genTorOnionKeyIfMissing = ({secretName}: {secretName: string}) => {
49  const secPath = pathDownJoin(secretsDir, `${secretName}.json`)
50  if (fs.existsSync(secPath)) {
51    const {seed} = JSON.parse(fs.readFileSync(secPath, 'utf-8'))
52    const seedBuf = Buffer.from(seed, 'hex')
53    const pubkey = deriveEd25519Pubkey(seedBuf)
54    return {seed: seedBuf, onionAddr: deriveOnionAddr(pubkey), secKeyFileBytes: buildTorSecKeyFile(seedBuf)}
55  }
56  assertExists(secretsDir, {secretName})
57  const seedBuf = randomBytes(32)
58  const pubkey = deriveEd25519Pubkey(seedBuf)
59  const onionAddr = deriveOnionAddr(pubkey)
60  fs.writeFileSync(secPath, JSON.stringify({seed: seedBuf.toString('hex'), onionAddr}))
61  return {seed: seedBuf, onionAddr, secKeyFileBytes: buildTorSecKeyFile(seedBuf)}
62}
63