xk6-webcrypto

This is a work in progress project implementation of the WebCrypto API specification for k6.

Current state

The current state of the project is that it is an experimental module of the WebCrypto API specification. While we consider it ready for production use, it is still missing some features and is not yet fully compliant with the specification.

Supported APIs and algorithms

Crypto

API	Supported	Notes
crypto.getRandomValues()	✅	complete
crypto.randomUUID()	✅	complete

SubtleCrypto

Encryption/Decryption

API	AES-CBC	AES-GCM	AES-CTR	RSA-OAEP
crypto.subtle.encrypt()	✅	✅	✅	❌
crypto.subtle.decrypt()	✅	✅	✅	❌

Signature

API	HMAC	ECDSA	RSASSA-PKCS1-v1_5	RSA-PSS
crypto.subtle.sign()	✅	✅	❌	❌
crypto.subtle.verify()	✅	✅	❌	❌

Key generation, import and export

API	AES-CBC	AES-GCM	AES-CTR	AES-KW	HMAC	ECDSA	ECDH	RSASSA-PKCS1-v1_5	RSA-PSS	RSA-OAEP
crypto.subtle.generateKey()	✅	✅	✅	❌	✅	✅	✅	❌	❌	❌
crypto.subtle.importKey()	✅	✅	✅	❌	✅	✅	✅	❌	❌	❌
crypto.subtle.exportKey()	✅	✅	✅	❌	✅	✅	✅	❌	❌	❌

Warning

Currently, only the raw and jwk (JSON Web Key) formats are supported for import/export operations for the AES-* and HMAC algorithms. ECDH and ECDSA have support for pkcs8, spki, raw and jwk formats.

Key derivation

API	ECDH	HKDF	PBKDF2
crypto.subtle.deriveKey()	❌	❌	❌
crypto.subtle.deriveBits()	✅	❌	❌

Note: deriveBits currently doesn't support length parameter non-multiple of 8.

Key wrapping

API	AES-CBC	AES-GCM	AES-CTR	AES-KW	RSA-OAEP
crypto.subtle.unwrapKey()	❌	❌	❌	❌	❌

APIs and algorithms with limited support

• AES-KW: in the current state of things, this module does not support the AES-KW (JSON Key Wrap) algorithm. The reason for it is that the Go standard library does not support it. We are looking into alternatives, but for now, this is a limitation of the module.
• AES-GCM: although the algorithm is supported, and can already be used, it is not fully compliant with the specification. The reason for this is that the Go standard library only supports a 12-byte nonce/iv, while the specification allows for a wider range of sizes. We do not expect to address this limitation unless the Go standard library adds support for it.

Contributing

Contributions are welcome! If the module is missing a feature you need, or if you find a bug, please open an issue or a pull request. If you are not sure about something, feel free to open an issue and ask.

Practices

The WebCrypto API specification is quite large, and it is not always easy to understand what is going on. To help with that, we have adopted a few practices that we hope will make it easier for contributors to understand the codebase.

Algorithm steps numbered comments

Contributors will likely notice that the codebase is annotated with comments of the form // {some number}.. Those comments are used to track the progress of the implementation of the specification and to ensure the correctness of the implementation of the algorithms. The numbers are the section numbers of the specification. For example, the comment // 8. in the SubtleCrypto.GenerateKey function refers to step 8 of the generateKey algorithm from the specification.

Following this convention allows us to document why certain operations are made in a certain way, and to track the progress of the implementation. We do not always add them, but we try to do so when it makes sense, and encourage contributors to do the same.