Add server/bitcoin-address.js

Add shared Bitcoin address validation

server/bitcoin-address.js

@@ -0,0 +1,249 @@
+const crypto = require('crypto')
+
+const BECH32_CHARSET =
+  'qpzry9x8gf2tvdw0s3jn54khce6mua7l'
+
+function bech32Polymod(values) {
+  const generators = [
+    0x3b6a57b2,
+    0x26508e6d,
+    0x1ea119fa,
+    0x3d4233dd,
+    0x2a1462b2,
+  ]
+
+  let chk = 1
+
+  for (const value of values) {
+    const top = chk >>> 25
+    chk = ((chk & 0x1ffffff) << 5) ^ value
+
+    for (let i = 0; i < 5; i++) {
+      if ((top >>> i) & 1) {
+        chk ^= generators[i]
+      }
+    }
+  }
+
+  return chk >>> 0
+}
+
+function bech32HrpExpand(hrp) {
+  const values = []
+
+  for (const char of hrp) {
+    values.push(char.charCodeAt(0) >> 5)
+  }
+
+  values.push(0)
+
+  for (const char of hrp) {
+    values.push(char.charCodeAt(0) & 31)
+  }
+
+  return values
+}
+
+function bech32VerifyChecksum(hrp, data) {
+  const polymod = bech32Polymod([
+    ...bech32HrpExpand(hrp),
+    ...data,
+  ])
+
+  return polymod === 1 || polymod === 0x2bc830a3
+}
+
+function bech32Decode(address) {
+  if (typeof address !== 'string') {
+    throw new Error('Bitcoin address must be a string')
+  }
+
+  if (address.length < 8 || address.length > 90) {
+    throw new Error('Invalid Bitcoin address length')
+  }
+
+  const hasLower = address !== address.toUpperCase()
+  const hasUpper = address !== address.toLowerCase()
+
+  if (hasLower && hasUpper) {
+    throw new Error(
+      'Bitcoin address must not mix uppercase and lowercase',
+    )
+  }
+
+  const normalized = address.toLowerCase()
+  const separator = normalized.lastIndexOf('1')
+
+  if (separator < 1 || separator + 7 > normalized.length) {
+    throw new Error('Invalid Bech32 separator')
+  }
+
+  const hrp = normalized.slice(0, separator)
+  const dataPart = normalized.slice(separator + 1)
+  const data = []
+
+  for (const char of dataPart) {
+    const value = BECH32_CHARSET.indexOf(char)
+
+    if (value === -1) {
+      throw new Error('Invalid Bech32 character')
+    }
+
+    data.push(value)
+  }
+
+  if (!bech32VerifyChecksum(hrp, data)) {
+    throw new Error('Invalid Bitcoin address checksum')
+  }
+
+  return {
+    hrp,
+    data: data.slice(0, -6),
+    spec:
+      bech32Polymod([
+        ...bech32HrpExpand(hrp),
+        ...data,
+      ]) === 1
+        ? 'bech32'
+        : 'bech32m',
+  }
+}
+
+function convertBits(data, fromBits, toBits, pad) {
+  let accumulator = 0
+  let bits = 0
+  const result = []
+  const maxValue = (1 << toBits) - 1
+
+  for (const value of data) {
+    if (value < 0 || value >> fromBits !== 0) {
+      throw new Error('Invalid bit conversion input')
+    }
+
+    accumulator =
+      (accumulator << fromBits) | value
+    bits += fromBits
+
+    while (bits >= toBits) {
+      bits -= toBits
+      result.push(
+        (accumulator >> bits) & maxValue,
+      )
+    }
+  }
+
+  if (pad) {
+    if (bits > 0) {
+      result.push(
+        (accumulator << (toBits - bits)) & maxValue,
+      )
+    }
+  } else {
+    if (bits >= fromBits) {
+      throw new Error('Invalid padding')
+    }
+
+    if (
+      ((accumulator << (toBits - bits)) &
+        maxValue) !==
+      0
+    ) {
+      throw new Error('Non-zero padding')
+    }
+  }
+
+  return result
+}
+
+function addressToScriptPubKey(address) {
+  const decoded = bech32Decode(address)
+
+  if (decoded.hrp !== 'bc') {
+    throw new Error(
+      'Only mainnet Bitcoin addresses are supported',
+    )
+  }
+
+  if (decoded.data.length < 1) {
+    throw new Error('Invalid SegWit address')
+  }
+
+  const witnessVersion = decoded.data[0]
+
+  if (witnessVersion > 16) {
+    throw new Error('Invalid SegWit witness version')
+  }
+
+  if (
+    witnessVersion === 0 &&
+    decoded.spec !== 'bech32'
+  ) {
+    throw new Error(
+      'Witness version 0 must use Bech32',
+    )
+  }
+
+  if (
+    witnessVersion !== 0 &&
+    decoded.spec !== 'bech32m'
+  ) {
+    throw new Error(
+      'Witness version 1+ must use Bech32m',
+    )
+  }
+
+  const program = convertBits(
+    decoded.data.slice(1),
+    5,
+    8,
+    false,
+  )
+
+  if (program.length < 2 || program.length > 40) {
+    throw new Error('Invalid witness program length')
+  }
+
+  if (
+    witnessVersion === 0 &&
+    program.length !== 20 &&
+    program.length !== 32
+  ) {
+    throw new Error(
+      'Invalid witness version 0 program length',
+    )
+  }
+
+  const versionOpcode =
+    witnessVersion === 0
+      ? 0x00
+      : 0x50 + witnessVersion
+
+  return Buffer.from([
+    versionOpcode,
+    program.length,
+    ...program,
+  ])
+}
+
+function scriptPubKeyToScripthash(scriptPubKey) {
+  const hash = crypto
+    .createHash('sha256')
+    .update(scriptPubKey)
+    .digest()
+
+  return Buffer.from(hash)
+    .reverse()
+    .toString('hex')
+}
+
+function addressToScripthash(address) {
+  return scriptPubKeyToScripthash(
+    addressToScriptPubKey(address),
+  )
+}
+
+module.exports = {
+  addressToScriptPubKey,
+  scriptPubKeyToScripthash,
+  addressToScripthash,
+}