go-cose

A golang library for the COSE specification

Project Status

Current Release: go-cose rc 1

The project was initially forked from the upstream mozilla-services/go-cose project, however the Veraison and Mozilla maintainers have agreed to retire the mozilla-services/go-cose project and focus on veraison/go-cose as the active project.

We thank the Mozilla maintainers and contributors for their great work that formed the base of the veraison/go-cose project.

Installation

go-cose is compatible with modern Go releases in module mode, with Go installed:

go get github.com/veraison/go-cose

will resolve and add the package to the current development module, along with its dependencies.

Alternatively the same can be achieved if you use import in a package:

import "github.com/veraison/go-cose"

and run go get without parameters.

Finally, to use the top-of-trunk version of this repo, use the following command:

go get github.com/veraison/go-cose@main

Usage

Signing and Verification

import "github.com/veraison/go-cose"

Construct a new COSE_Sign1 message, then sign it using ECDSA w/ SHA-256 and finally marshal it. For example:

package main

import (
    "crypto/ecdsa"
    "crypto/elliptic"
    "crypto/rand"
    _ "crypto/sha256"

    "github.com/veraison/go-cose"
)

func SignP256(data []byte) ([]byte, error) {
    // create a signer
    privateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
    if err != nil {
        return nil, err
    }
    signer, err := cose.NewSigner(cose.AlgorithmES256, privateKey)
    if err != nil {
        return nil, err
    }

    // create message header
    headers := cose.Headers{
        Protected: cose.ProtectedHeader{
            cose.HeaderLabelAlgorithm: cose.AlgorithmES256,
        },
    }

    // sign and marshal message
    return cose.Sign1(rand.Reader, signer, headers, data, nil)
}

Verify a raw COSE_Sign1 message. For example:

package main

import (
    "crypto"
    _ "crypto/sha256"

    "github.com/veraison/go-cose"
)

func VerifyP256(publicKey crypto.PublicKey, sig []byte) error {
    // create a verifier from a trusted private key
    verifier, err := cose.NewVerifier(cose.AlgorithmES512, publicKey)
    if err != nil {
        return err
    }

    // create a sign message from a raw COSE_Sign1 payload
    var msg cose.Sign1Message
    if err = msg.UnmarshalCBOR(sig); err != nil {
        return err
    }
    return msg.Verify(nil, verifier)
}

See example_test.go for more examples.

About hashing

go-cose does not import any hash package by its own to avoid linking unnecessary algorithms to the final binary. It is the the responsibility of the go-cose user to make the necessary hash functions available at runtime, i.e., by using a blank import:

import (
    _ "crypto/sha256"
    _ "crypto/sha512"
)

These are the required packages for each built-in cose.Algorithm:

• cose.AlgorithmPS256, cose.AlgorithmES256: crypto/sha256
• cose.AlgorithmPS384, cose.AlgorithmPS512, cose.AlgorithmES384, cose.AlgorithmES512: crypto/sha512
• cose.AlgorithmEd25519: none

Features

Signing and Verifying Objects

go-cose supports two different signature structures:

• cose.Sign1Message implements COSE_Sign1.
• cose.SignMessage implements COSE_Sign.

⚠️ The COSE_Sign API is currently EXPERIMENTAL and may be changed or removed in a later release. In addition, the amount of functional and security testing it has received so far is significantly lower than the COSE_Sign1 API.

Built-in Algorithms

go-cose has built-in supports the following algorithms:

• PS{256,384,512}: RSASSA-PSS w/ SHA as defined in RFC 8230.
• ES{256,384,512}: ECDSA w/ SHA as defined in RFC 8152.
• Ed25519: PureEdDSA as defined in RFC 8152.

Custom Algorithms

The supported algorithms can be extended at runtime by using cose.RegisterAlgorithm.

API docs

Integer Ranges

CBOR supports integers in the range [-2⁶⁴, -1] ∪ [0, 2⁶⁴ - 1].

This does not map onto a single Go integer type.

go-cose uses int64 to encompass both positive and negative values to keep data sizes smaller and easy to use.

The main effect is that integer label values in the [-2⁶⁴, -2⁶³ - 1] and the [2⁶³, 2⁶⁴ - 1] ranges, which are nominally valid per RFC 8152, are rejected by the go-cose library.

Conformance Tests

go-cose runs the GlueCOSE test suite on every local go test execution. These are also executed on every CI job.

Fuzz Tests

go-cose implements several fuzz tests using Go's native fuzzing.

Fuzzing requires Go 1.18 or higher, and can be executed as follows:

go test -fuzz=FuzzSign1

Security Reviews

go-cose undergoes periodic security review. The security review reports are located here