From f02be5bc9de55d26320cc73a89f4f4247e0b8ae8 Mon Sep 17 00:00:00 2001
From: Jack Mallers <jimmymowschess@gmail.com>
Date: Sun, 1 Oct 2017 15:28:58 -0500
Subject: [PATCH] feature(bech32): use bech32 to determine if ln pareq is valid

---
 app/reducers/payform.js |  12 +++-
 app/utils/bech32.js     | 148 ++++++++++++++++++++++++++++++++++++++++
 app/utils/index.js      |   4 +-
 3 files changed, 160 insertions(+), 4 deletions(-)
 create mode 100644 app/utils/bech32.js

diff --git a/app/reducers/payform.js b/app/reducers/payform.js
index 3ff64757..f1d1adad 100644
--- a/app/reducers/payform.js
+++ b/app/reducers/payform.js
@@ -1,7 +1,7 @@
 import { createSelector } from 'reselect'
 import bitcoin from 'bitcoinjs-lib'
 import { tickerSelectors } from './ticker'
-import { btc } from '../utils'
+import { btc, bech32 } from '../utils'
 
 // Initial State
 const initialState = {
@@ -94,11 +94,17 @@ payFormSelectors.isOnchain = createSelector(
   }
 )
 
-// TODO: Add more robust logic to detect a LN payment request
 payFormSelectors.isLn = createSelector(
   payInputSelector,
   input => {
-    return input.startsWith('ln')
+    if (!input.startWith('ln')) { return }
+
+    try {
+      bech32.decode(input)
+      return true
+    } catch (e) {
+      return false
+    }
   }
 )
 
diff --git a/app/utils/bech32.js b/app/utils/bech32.js
new file mode 100644
index 00000000..ff9f2de7
--- /dev/null
+++ b/app/utils/bech32.js
@@ -0,0 +1,148 @@
+// Using bech32 here just without the 90 char length: https://github.com/bitcoinjs/bech32/blob/master/index.js
+
+'use strict'
+let ALPHABET = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l'
+
+// pre-compute lookup table
+let ALPHABET_MAP = {}
+for (let z = 0; z < ALPHABET.length; z++) {
+  let x = ALPHABET.charAt(z)
+
+  if (ALPHABET_MAP[x] !== undefined) throw new TypeError(x + ' is ambiguous')
+  ALPHABET_MAP[x] = z
+}
+
+function polymodStep (pre) {
+  let b = pre >> 25
+  return ((pre & 0x1FFFFFF) << 5) ^
+    (-((b >> 0) & 1) & 0x3b6a57b2) ^
+    (-((b >> 1) & 1) & 0x26508e6d) ^
+    (-((b >> 2) & 1) & 0x1ea119fa) ^
+    (-((b >> 3) & 1) & 0x3d4233dd) ^
+    (-((b >> 4) & 1) & 0x2a1462b3)
+}
+
+function prefixChk (prefix) {
+  let chk = 1
+  for (let i = 0; i < prefix.length; ++i) {
+    let c = prefix.charCodeAt(i)
+    if (c < 33 || c > 126) throw new Error('Invalid prefix (' + prefix + ')')
+
+    chk = polymodStep(chk) ^ (c >> 5)
+  }
+  chk = polymodStep(chk)
+
+  for (let i = 0; i < prefix.length; ++i) {
+    let v = prefix.charCodeAt(i)
+    chk = polymodStep(chk) ^ (v & 0x1f)
+  }
+  return chk
+}
+
+function encode (prefix, words) {
+  // too long?
+  if ((prefix.length + 7 + words.length) > 90) throw new TypeError('Exceeds Bech32 maximum length')
+  prefix = prefix.toLowerCase()
+
+  // determine chk mod
+  let chk = prefixChk(prefix)
+  let result = prefix + '1'
+  for (let i = 0; i < words.length; ++i) {
+    let x = words[i]
+    if ((x >> 5) !== 0) throw new Error('Non 5-bit word')
+
+    chk = polymodStep(chk) ^ x
+    result += ALPHABET.charAt(x)
+  }
+
+  for (let i = 0; i < 6; ++i) {
+    chk = polymodStep(chk)
+  }
+  chk ^= 1
+
+  for (let i = 0; i < 6; ++i) {
+    let v = (chk >> ((5 - i) * 5)) & 0x1f
+    result += ALPHABET.charAt(v)
+  }
+
+  return result
+}
+
+function decode (str) {
+  if (str.length < 8) throw new TypeError(str + ' too short')
+  // LN payment requests can be longer than 90 chars
+  // if (str.length > 90) throw new TypeError(str + ' too long')
+
+  // don't allow mixed case
+  let lowered = str.toLowerCase()
+  let uppered = str.toUpperCase()
+  if (str !== lowered && str !== uppered) throw new Error('Mixed-case string ' + str)
+  str = lowered
+
+  let split = str.lastIndexOf('1')
+  if (split === 0) throw new Error('Missing prefix for ' + str)
+
+  let prefix = str.slice(0, split)
+  let wordChars = str.slice(split + 1)
+  if (wordChars.length < 6) throw new Error('Data too short')
+
+  let chk = prefixChk(prefix)
+  let words = []
+  for (let i = 0; i < wordChars.length; ++i) {
+    let c = wordChars.charAt(i)
+    let v = ALPHABET_MAP[c]
+    if (v === undefined) throw new Error('Unknown character ' + c)
+    chk = polymodStep(chk) ^ v
+
+    // not in the checksum?
+    if (i + 6 >= wordChars.length) continue
+    words.push(v)
+  }
+
+  if (chk !== 1) throw new Error('Invalid checksum for ' + str)
+  return { prefix, words }
+}
+
+function convert (data, inBits, outBits, pad) {
+  let value = 0
+  let bits = 0
+  let maxV = (1 << outBits) - 1
+
+  let result = []
+  for (let i = 0; i < data.length; ++i) {
+    value = (value << inBits) | data[i]
+    bits += inBits
+
+    while (bits >= outBits) {
+      bits -= outBits
+      result.push((value >> bits) & maxV)
+    }
+  }
+
+  if (pad) {
+    if (bits > 0) {
+      result.push((value << (outBits - bits)) & maxV)
+    }
+  } else {
+    if (bits >= inBits) throw new Error('Excess padding')
+    if ((value << (outBits - bits)) & maxV) throw new Error('Non-zero padding')
+  }
+
+  return result
+}
+
+function toWords (bytes) {
+  return convert(bytes, 8, 5, true)
+}
+
+function fromWords (words) {
+  return convert(words, 5, 8, false)
+}
+
+export default {
+  decode,
+  encode,
+  toWords,
+  fromWords
+}
+
diff --git a/app/utils/index.js b/app/utils/index.js
index 44213478..3d162c0f 100644
--- a/app/utils/index.js
+++ b/app/utils/index.js
@@ -1,7 +1,9 @@
 import btc from './btc'
 import usd from './usd'
+import bech32 from './bech32'
 
 export default {
   btc,
-  usd
+  usd,
+  bech32
 }