Affected: Google LLC AWS S3 Crypto SDK for GoLang

A padding oracle vulnerability exists in the AWS S3 Crypto SDK for GoLang versions prior to V2. The SDK allows users to encrypt files with AES-CBC without computing a Message Authentication Code (MAC), which then allows an attacker who has write access to the target's S3 bucket and can observe whether or not an endpoint with access to the key can decrypt a file, they can reconstruct the plaintext with (on average) 128*length (plaintext) queries to the endpoint, by exploiting CBC's ability to manipulate the bytes of the next block and PKCS5 padding errors. It is recommended to update your SDK to V2 or later, and re-encrypt your files.

Affected: Go: github.com/go-jose/go-jose/v4, Go: github.com/go-jose/go-jose/v3, Go: github.com/go-jose/go-jose

### Impact

Decrypting a JSON Web Encryption (JWE) object will panic if the `alg` field indicates a key wrapping algorithm ([one ending in `KW`](https://pkg.go.dev/github.com/go-jose/go-jose/v4#pkg-constants), with the exception of `A128GCMKW`, `A192GCMKW`, and `A256GCMKW`) and the `encrypted_key` field is empty. The panic happens when `cipher.KeyUnwrap()` in `key_wrap.go` attempts to allocate a slice with a zero or negative length based on the length of the `encrypted_key`.

This code path is reachable from `ParseEncrypted()` / `ParseEncryptedJSON()` / `ParseEncryptedCompact()` followed by `Decrypt()` on the resulting object. Note that the parse functions take a list of accepted key algorithms. If the accepted key algorithms do not include any key wrapping algorithms, parsing will fail and the application will be unaffected.

This panic is also reachable by calling `cipher.KeyUnwrap()` directly with any `ciphertext` parameter less than 16 bytes long, but calling this function directly is less common.

Panics can lead to denial of service.

### Fixed In

4.1.4 and v3.0.5

### Workarounds

If the list of `keyAlgorithms` passed to `ParseEncrypted()` / `ParseEncryptedJSON()` / `ParseEncryptedCompact()` does not include key wrapping algorithms (those ending in `KW`), your application is unaffected.

If your application uses key wrapping, you can prevalidate to the JWE objects to ensure the `encrypted_key` field is nonempty. If your application accepts JWE Compact Serialization,…