feat: add AES KW

lib/jwa/aes_cbc_hmac_sha2.js

@@ -4,8 +4,8 @@ const { strict: assert } = require('assert')
 
 const { TODO } = require('../errors')
 
+// TODO: DRY
 const MAX_INT32 = Math.pow(2, 32)
-
 const uint64be = (value, buf = Buffer.alloc(8)) => {
   const high = Math.floor(value / MAX_INT32)
   const low = value % MAX_INT32

lib/jwa/aes_kw.js

@@ -0,0 +1,104 @@
+const { createCipheriv, createDecipheriv } = require('crypto')
+const { strict: assert } = require('assert')
+
+const { TODO } = require('../errors')
+
+// TODO: DRY
+const MAX_INT32 = Math.pow(2, 32)
+const uint64be = (value, buf = Buffer.alloc(8)) => {
+  const high = Math.floor(value / MAX_INT32)
+  const low = value % MAX_INT32
+
+  buf.writeUInt32BE(high, 0)
+  buf.writeUInt32BE(low, 4)
+  return buf
+}
+
+const A0 = Buffer.alloc(8, 'a6', 'hex')
+
+function xor (a, b) {
+  const len = Math.max(a.length, b.length)
+  const result = Buffer.alloc(len)
+  for (let idx = 0; len > idx; idx++) {
+    result[idx] = (a[idx] || 0) ^ (b[idx] || 0)
+  }
+
+  return result
+}
+
+function split (input, size) {
+  const output = []
+  for (let idx = 0; input.length > idx; idx += size) {
+    output.push(input.slice(idx, idx + size))
+  }
+  return output
+}
+
+const wrapKey = (size, { keyObject }, payload) => {
+  // TODO: commonCheck
+
+  const iv = Buffer.alloc(16)
+  let R = split(payload, 8)
+  let A
+  let B
+  let count
+  A = A0
+  for (let jdx = 0; jdx < 6; jdx++) {
+    for (let idx = 0; R.length > idx; idx++) {
+      count = (R.length * jdx) + idx + 1
+      const cipher = createCipheriv(`AES${size}`, keyObject, iv)
+      B = Buffer.concat([A, R[idx]])
+      B = cipher.update(B)
+
+      A = xor(B.slice(0, 8), uint64be(count))
+      R[idx] = B.slice(8, 16)
+    }
+  }
+  R = [A].concat(R)
+
+  return Buffer.concat(R)
+}
+
+const unwrapKey = (size, { keyObject }, payload) => {
+  // TODO: commonCheck
+
+  const iv = Buffer.alloc(16)
+
+  let R = split(payload, 8)
+  let A
+  let B
+  let count
+  A = R[0]
+  R = R.slice(1)
+  for (let jdx = 5; jdx >= 0; --jdx) {
+    for (let idx = R.length - 1; idx >= 0; --idx) {
+      count = (R.length * jdx) + idx + 1
+      B = xor(A, uint64be(count))
+      B = Buffer.concat([B, R[idx], iv])
+      const cipher = createDecipheriv(`AES${size}`, keyObject, iv)
+      B = cipher.update(B)
+
+      A = B.slice(0, 8)
+      R[idx] = B.slice(8, 16)
+    }
+  }
+
+  // TODO timingSafeEqual
+  if (A.toString() !== A0.toString()) {
+    throw new TODO('decryption failed')
+  }
+
+  return Buffer.concat(R)
+}
+
+module.exports = (JWA) => {
+  ['A128KW', 'A192KW', 'A256KW'].forEach((jwaAlg) => {
+    const size = parseInt(jwaAlg.substr(1, 3), 10)
+
+    assert(!JWA.wrapKey.has(jwaAlg), `wrapKey alg ${jwaAlg} already registered`)
+    assert(!JWA.unwrapKey.has(jwaAlg), `unwrapKey alg ${jwaAlg} already registered`)
+
+    JWA.wrapKey.set(jwaAlg, wrapKey.bind(undefined, size))
+    JWA.unwrapKey.set(jwaAlg, unwrapKey.bind(undefined, size))
+  })
+}

lib/jwa/index.js

@@ -15,13 +15,14 @@ require('./ecdsa')(JWA)
 require('./rsassa_pss')(JWA)
 require('./rsassa_pkcs1')(JWA)
 
-// wrapKey, unwrapKey
-require('./rsaes')(JWA)
-
 // encrypt, decrypt
 require('./aes_cbc_hmac_sha2')(JWA)
 require('./aes_gcm')(JWA)
+
+// wrapKey, unwrapKey
+require('./rsaes')(JWA)
 require('./aes_gcm_kw')(JWA)
+require('./aes_kw')(JWA)
 
 module.exports = {
   sign: (alg, key, payload) => {