SubtleCrypto: unwrapKey() method

unwrapKey(format, wrappedKey, unwrappingKey, unwrapAlgo, unwrappedKeyAlgo, extractable, keyUsages)

/*
Salt that is to be used in derivation of the key-wrapping key,
alongside the password the user supplies.
This must match the salt value that was originally used to derive
the key.
*/
const saltBytes = [
  89, 113, 135, 234, 168, 204, 21, 36, 55, 93, 1, 132, 242, 242, 192, 156,
];

/*
The wrapped key itself.
*/
const wrappedKeyBytes = [
  171, 223, 14, 36, 201, 233, 233, 120, 164, 68, 217, 192, 226, 80, 224, 39,
  199, 235, 239, 60, 212, 169, 100, 23, 61, 54, 244, 197, 160, 80, 109, 230,
  207, 225, 57, 197, 175, 71, 80, 209,
];

/*
Convert an array of byte values to an ArrayBuffer.
*/
function bytesToArrayBuffer(bytes) {
  const bytesAsArrayBuffer = new ArrayBuffer(bytes.length);
  const bytesUint8 = new Uint8Array(bytesAsArrayBuffer);
  bytesUint8.set(bytes);
  return bytesAsArrayBuffer;
}

/*
Get some key material to use as input to the deriveKey method.
The key material is a password supplied by the user.
*/
function getKeyMaterial() {
  let password = window.prompt("Enter your password");
  let enc = new TextEncoder();
  return window.crypto.subtle.importKey(
    "raw",
    enc.encode(password),
    { name: "PBKDF2" },
    false,
    ["deriveBits", "deriveKey"],
  );
}

/*
Derive an AES-KW key using PBKDF2.
*/
async function getUnwrappingKey() {
  // 1. get the key material (user-supplied password)
  const keyMaterial = await getKeyMaterial();
  // 2 initialize the salt parameter.
  // The salt must match the salt originally used to derive the key.
  // In this example it's supplied as a constant "saltBytes".
  const saltBuffer = bytesToArrayBuffer(saltBytes);
  // 3 derive the key from key material and salt
  return window.crypto.subtle.deriveKey(
    {
      name: "PBKDF2",
      salt: saltBuffer,
      iterations: 100000,
      hash: "SHA-256",
    },
    keyMaterial,
    { name: "AES-KW", length: 256 },
    true,
    ["wrapKey", "unwrapKey"],
  );
}

/*
Unwrap an AES secret key from an ArrayBuffer containing the raw bytes.
Takes an array containing the bytes, and returns a Promise
that will resolve to a CryptoKey representing the secret key.
*/
async function unwrapSecretKey(wrappedKey) {
  // 1. get the unwrapping key
  const unwrappingKey = await getUnwrappingKey();
  // 2. initialize the wrapped key
  const wrappedKeyBuffer = bytesToArrayBuffer(wrappedKey);
  // 3. unwrap the key
  return window.crypto.subtle.unwrapKey(
    "raw", // import format
    wrappedKeyBuffer, // ArrayBuffer representing key to unwrap
    unwrappingKey, // CryptoKey representing key encryption key
    "AES-KW", // algorithm identifier for key encryption key
    "AES-GCM", // algorithm identifier for key to unwrap
    true, // extractability of key to unwrap
    ["encrypt", "decrypt"], // key usages for key to unwrap
  );
}

/*
Salt that is to be used in derivation of the key-wrapping key,
alongside the password the user supplies.
This must match the salt value that was originally used to derive
the key.
*/
const saltBytes = [
  180, 253, 62, 216, 47, 35, 90, 55, 218, 233, 103, 10, 172, 143, 161, 177,
];

/*
IV that is to be used in decrypting the key to unwrap.
This must the same IV that was originally used to encrypt
the key.
*/
const ivBytes = [212, 187, 26, 247, 172, 51, 37, 151, 27, 177, 249, 142];

/*
The wrapped key itself.
*/
const wrappedKeyBytes = [
  6, 155, 182, 208, 7, 141, 44, 18, 3, 151, 58, 126, 68, 100, 252, 225, 241, 11,
  25, 201, 153, 171, 102, 174, 150, 29, 62, 195, 110, 138, 106, 109, 14, 6, 108,
  148, 104, 221, 22, 93, 102, 221, 146, 25, 65, 112, 4, 140, 79, 194, 164, 163,
  156, 250, 108, 11, 14, 220, 78, 194, 161, 17, 14, 57, 121, 70, 13, 28, 220,
  210, 78, 32, 46, 217, 36, 165, 220, 170, 244, 152, 214, 150, 83, 2, 138, 128,
  11, 251, 227, 213, 72, 100, 158, 10, 162, 40, 195, 60, 248, 77, 37, 156, 34,
  10, 213, 171, 67, 147, 73, 231, 31, 63, 80, 176, 103, 206, 187, 164, 214, 250,
  49, 223, 185, 5, 48, 241, 17, 1, 253, 59, 185, 181, 209, 255, 42, 223, 175,
  90, 159, 174, 169, 205, 156, 120, 195, 1, 135, 165, 226, 46, 119, 27, 97, 183,
  23, 197, 227, 85, 138, 235, 79, 158, 167, 59, 62, 194, 34, 210, 214, 240, 215,
  101, 233, 63, 138, 53, 87, 253, 189, 27, 66, 150, 76, 242, 76, 102, 174, 179,
  163, 184, 205, 11, 161, 224, 19, 110, 34, 175, 192, 101, 117, 169, 86, 66, 56,
  241, 128, 13, 156, 165, 125, 139, 110, 138, 50, 108, 129, 251, 137, 26, 186,
  110, 117, 113, 207, 179, 59, 213, 18, 175, 14, 203, 192, 2, 97, 131, 125, 167,
  227, 182, 87, 72, 123, 54, 156, 60, 195, 88, 224, 96, 46, 126, 245, 251, 247,
  147, 110, 147, 173, 82, 106, 93, 210, 55, 71, 127, 133, 41, 37, 181, 17, 106,
  16, 158, 220, 136, 43, 75, 133, 96, 240, 151, 116, 40, 44, 254, 2, 32, 74,
  226, 193, 172, 48, 211, 71, 109, 163, 143, 30, 92, 28, 30, 183, 25, 16, 176,
  207, 77, 93, 139, 242, 114, 91, 218, 126, 123, 234, 18, 9, 245, 53, 46, 172,
  215, 62, 92, 249, 191, 17, 27, 0, 58, 151, 33, 23, 169, 93, 177, 253, 152,
  147, 198, 196, 226, 42, 202, 166, 99, 250, 127, 40, 221, 196, 121, 195, 198,
  235, 30, 159, 159, 95, 182, 107, 175, 137, 177, 49, 72, 63, 131, 162, 198,
  186, 22, 255, 230, 237, 195, 56, 147, 177, 101, 52, 227, 125, 32, 180, 242,
  47, 92, 212, 6, 148, 218, 107, 125, 137, 123, 15, 51, 107, 159, 228, 238, 212,
  60, 54, 184, 48, 110, 248, 252, 208, 46, 23, 149, 78, 169, 201, 68, 242, 193,
  251, 156, 227, 42, 90, 109, 102, 172, 61, 207, 124, 96, 98, 79, 37, 218, 16,
  212, 139, 162, 0, 183, 235, 171, 75, 18, 84, 160, 120, 173, 156, 187, 99, 24,
  58, 88, 213, 148, 24, 193, 111, 75, 169, 10, 158, 207, 148, 84, 249, 156, 248,
  19, 221, 2, 175, 1, 8, 74, 221, 212, 244, 123, 34, 223, 175, 54, 166, 101, 51,
  175, 141, 80, 87, 9, 146, 72, 223, 46, 251, 199, 192, 2, 22, 125, 16, 15, 99,
  26, 159, 165, 133, 172, 169, 26, 236, 44, 86, 182, 162, 81, 143, 249, 15, 207,
  12, 232, 15, 205, 199, 78, 133, 199, 19, 232, 183, 33, 183, 72, 117, 72, 27,
  43, 254, 13, 17, 252, 1, 143, 137, 154, 10, 4, 77, 85, 24, 85, 143, 200, 81,
  76, 171, 43, 124, 42, 191, 150, 70, 10, 90, 178, 198, 40, 233, 233, 225, 146,
  231, 209, 254, 2, 90, 216, 5, 97, 105, 204, 82, 88, 81, 99, 92, 159, 116, 192,
  223, 148, 252, 12, 24, 197, 211, 187, 212, 98, 252, 201, 154, 184, 65, 54, 47,
  13, 106, 151, 168, 208, 112, 212, 74, 204, 36, 233, 98, 104, 58, 103, 1, 194,
  13, 26, 109, 101, 60, 42, 3, 215, 20, 25, 99, 176, 63, 28, 112, 102, 121, 190,
  96, 198, 228, 196, 78, 38, 82, 37, 248, 42, 150, 115, 6, 10, 22, 101, 42, 237,
  175, 69, 232, 212, 231, 40, 193, 70, 211, 245, 106, 231, 175, 150, 88, 105,
  170, 139, 238, 196, 64, 218, 250, 47, 165, 22, 36, 196, 161, 30, 79, 175, 14,
  133, 88, 129, 182, 56, 140, 147, 168, 134, 91, 68, 172, 110, 195, 134, 156,
  68, 78, 249, 215, 68, 250, 11, 23, 70, 59, 156, 99, 75, 249, 159, 84, 16, 206,
  93, 16, 130, 34, 66, 210, 82, 252, 53, 251, 84, 59, 226, 212, 154, 15, 20,
  163, 58, 228, 109, 53, 214, 151, 237, 10, 169, 107, 180, 123, 174, 159, 182,
  8, 240, 115, 115, 220, 131, 128, 79, 80, 61, 133, 58, 24, 98, 193, 225, 56,
  36, 159, 254, 199, 49, 44, 160, 28, 81, 140, 163, 24, 143, 114, 31, 237, 235,
  250, 83, 72, 215, 44, 232, 182, 45, 39, 182, 193, 248, 65, 174, 186, 52, 219,
  30, 198, 48, 1, 134, 151, 81, 114, 38, 124, 7, 213, 205, 138, 28, 22, 216, 76,
  46, 224, 241, 88, 156, 7, 62, 23, 104, 34, 54, 25, 156, 93, 212, 133, 182, 61,
  93, 255, 195, 68, 244, 234, 53, 132, 151, 140, 72, 146, 127, 113, 227, 34,
  243, 218, 222, 47, 218, 113, 18, 173, 203, 158, 133, 90, 156, 214, 77, 20,
  113, 1, 231, 164, 52, 55, 69, 132, 24, 68, 131, 212, 7, 153, 34, 179, 113,
  156, 81, 127, 83, 57, 29, 195, 90, 64, 211, 115, 202, 188, 5, 42, 188, 142,
  203, 109, 231, 53, 206, 72, 220, 90, 23, 12, 1, 178, 122, 60, 221, 68, 6, 14,
  154, 108, 203, 171, 142, 159, 249, 13, 55, 52, 110, 214, 33, 147, 164, 181,
  50, 79, 164, 200, 83, 251, 40, 105, 223, 50, 0, 115, 240, 146, 23, 122, 80,
  204, 169, 38, 198, 154, 31, 29, 23, 236, 39, 35, 131, 147, 242, 163, 138, 158,
  236, 117, 7, 108, 33, 132, 98, 50, 111, 46, 146, 251, 82, 34, 85, 5, 130, 237,
  67, 40, 170, 235, 124, 92, 66, 71, 239, 12, 97, 136, 251, 1, 206, 13, 51, 232,
  92, 46, 35, 95, 5, 123, 24, 183, 99, 243, 124, 75, 155, 89, 66, 54, 72, 17,
  255, 99, 137, 199, 232, 204, 9, 248, 78, 35, 218, 136, 117, 239, 102, 240,
  187, 40, 89, 244, 140, 109, 229, 120, 116, 54, 207, 171, 11, 248, 190, 199,
  81, 53, 109, 8, 188, 51, 93, 165, 34, 255, 165, 191, 198, 130, 220, 41, 192,
  166, 194, 69, 104, 124, 158, 122, 236, 176, 24, 60, 87, 240, 42, 158, 143, 37,
  143, 208, 155, 249, 230, 21, 4, 230, 56, 194, 62, 235, 132, 14, 50, 180, 216,
  134, 28, 25, 159, 64, 199, 161, 236, 60, 233, 160, 172, 68, 169, 2, 5, 252,
  190, 20, 54, 115, 248, 63, 93, 107, 156, 8, 96, 85, 32, 189, 118, 66, 114,
  126, 64, 203, 97, 235, 13, 18, 102, 192, 51, 59, 5, 122, 171, 96, 129, 40, 32,
  154, 4, 191, 234, 75, 184, 112, 201, 244, 110, 50, 216, 44, 88, 139, 175, 58,
  112, 7, 52, 25, 64, 112, 40, 148, 187, 39, 234, 96, 151, 16, 158, 114, 113,
  109, 164, 47, 108, 94, 148, 35, 232, 221, 33, 110, 126, 170, 25, 234, 45, 165,
  180, 210, 193, 120, 247, 155, 127,
];

/*
The unwrapped signing key.
*/
let signingKey;

const signButton = document.querySelector(".pkcs8 .sign-button");

/*
Convert an array of byte values to an ArrayBuffer.
*/
function bytesToArrayBuffer(bytes) {
  const bytesAsArrayBuffer = new ArrayBuffer(bytes.length);
  const bytesUint8 = new Uint8Array(bytesAsArrayBuffer);
  bytesUint8.set(bytes);
  return bytesAsArrayBuffer;
}

/*
Get some key material to use as input to the deriveKey method.
The key material is a password supplied by the user.
*/
function getKeyMaterial() {
  let password = window.prompt("Enter your password");
  let enc = new TextEncoder();
  return window.crypto.subtle.importKey(
    "raw",
    enc.encode(password),
    { name: "PBKDF2" },
    false,
    ["deriveBits", "deriveKey"],
  );
}

/*
Derive an AES-GCM key using PBKDF2.
*/
async function getUnwrappingKey() {
  // 1. get the key material (user-supplied password)
  const keyMaterial = await getKeyMaterial();
  // 2 initialize the salt parameter.
  // The salt must match the salt originally used to derive the key.
  // In this example it's supplied as a constant "saltBytes".
  const saltBuffer = bytesToArrayBuffer(saltBytes);
  // 3 derive the key from key material and salt
  return window.crypto.subtle.deriveKey(
    {
      name: "PBKDF2",
      salt: saltBuffer,
      iterations: 100000,
      hash: "SHA-256",
    },
    keyMaterial,
    { name: "AES-GCM", length: 256 },
    true,
    ["wrapKey", "unwrapKey"],
  );
}

/*
Unwrap an RSA-PSS private signing key from an ArrayBuffer containing
the raw bytes.
Takes an array containing the bytes, and returns a Promise
that will resolve to a CryptoKey representing the private key.
*/
async function unwrapPrivateKey(wrappedKey) {
  // 1. get the unwrapping key
  const unwrappingKey = await getUnwrappingKey();
  // 2. initialize the wrapped key
  const wrappedKeyBuffer = bytesToArrayBuffer(wrappedKey);
  // 3. initialize the iv
  const ivBuffer = bytesToArrayBuffer(ivBytes);
  // 4. unwrap the key
  return window.crypto.subtle.unwrapKey(
    "pkcs8", // import format
    wrappedKeyBuffer, // ArrayBuffer representing key to unwrap
    unwrappingKey, // CryptoKey representing key encryption key
    {
      // algorithm params for key encryption key
      name: "AES-GCM",
      iv: ivBuffer,
    },
    {
      // algorithm params for key to unwrap
      name: "RSA-PSS",
      hash: "SHA-256",
    },
    true, // extractability of key to unwrap
    ["sign"], // key usages for key to unwrap
  );
}