Internal Error when using Web Crypto

Developers Workers
1

Here’s my code:

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

/**
 * Fetch and log a given request object
 * @param {Request} request
 */
async function handleRequest(request) {
    var createdCryptoKey = await crypto.subtle.generateKey(
    {
        name: "AES-GCM",
        length: 256, //can be  128, 192, or 256
    },
    false, //whether the key is extractable (i.e. can be used in exportKey)
    ["encrypt", "decrypt"] //can "encrypt", "decrypt", "wrapKey", or "unwrapKey"
)
console.log(createdCryptoKey);
  var encryptedData = await crypto.subtle.encrypt(
    {
        name: "AES-GCM",
        iv: crypto.getRandomValues(new Uint8Array(12)),
        tagLength: 128,
    },
    createdCryptoKey, //from generateKey or importKey above
    new ArrayBuffer("test") //ArrayBuffer of data you want to encrypt
  );
  console.log("encrypted:", encryptedData);
  return new Response("test")
}

The error returned is:

Uncaught (in promise) DOMException {}
Uncaught (in response) Error: internal error

This isn’t really that useful, so I don’t know what I’m doing wrong.

Does anyone have any idea what the issue is? AES-GCM appears to be supported for encryption, so I’m not sure what I’m doing wrong.

Thanks in advance.

3

Make sure to await the createCryptoKey and also crypto.getRandomValues or you’ll retrieve empty values.

4

That shouldnt be the issue here however. The OP does use await in the generateKey() context and getRandomValues() is not an asynchronous function.

5

You’re right about generateKey() I saw it wrong, it’s in the same function. I might be wrong about getRandomValues(), the docs doesn’t specify if returns a promise so I assumed that it would work like all the other subtle encryptions and return a promise.

Edit: crypto.getRandomValues() instanceof Promise says noo, so not a promise.

6

I figured it out.

The string that’s being encrypted has to be encoded using TextEncoder.

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

/**
 * Fetch and log a given request object
 * @param {Request} request
 */
async function handleRequest(request) {
    let enc = new TextEncoder();
    var createdCryptoKey = await crypto.subtle.generateKey(
    {
        name: "AES-GCM",
        length: 256, //can be  128, 192, or 256
    },
    false, //whether the key is extractable (i.e. can be used in exportKey)
    ["encrypt", "decrypt"] //can "encrypt", "decrypt", "wrapKey", or "unwrapKey"
)
console.log(createdCryptoKey);
  var encryptedData = await crypto.subtle.encrypt(
    {
        name: "AES-GCM",
        iv: crypto.getRandomValues(new Uint8Array(12)),
        tagLength: 128,
    },
    createdCryptoKey, //from generateKey or importKey above
    enc.encode("test")
  );
  console.log("encrypted:", encryptedData);
  return new Response("test")
}
1 Like
7

Indeed, new ArrayBuffer("test") coerces "test" to NaN, creating a zero-length buffer. So it seems like our implementation of SubtleCrypto.encrypt() doesn’t properly handle zero-length plaintext buffers. I don’t think this should throw anything at all, much less the cryptic OperationError/internal error that you’ve encountered, and have filed an internal bug report.

Thank you for reporting this!
Harris

1 Like
8

Excellent catch!