How to Easily Parse and Verify AWS Cognito JWT Tokens in Go?

Parsing and Verifying JWT Tokens from AWS Cognito in Go

Challenge

Verifying and extracting information from JWT tokens issued by AWS Cognito can be a daunting task due to the lack of suitable Go packages. Despite using commonly available libraries, the process remains complex. This article aims to simplify this task by providing a step-by-step solution using appropriate libraries.

The Key to Validation: Public Keys

To validate a JWT token, the corresponding public key is essential. These keys can be obtained from the JWK (JSON Web Key) URL provided by AWS Cognito:

https://cognito-idp.{region}.amazonaws.com/{userPoolId}/.well-known/jwks.json

Parsing Keys and Verifying Tokens

A recommended approach is to utilize the jwk and jwt-go libraries in tandem. jwx simplifies parsing public keys from the JWK URL, while jwt-go assists in handling the JWT token:

// Parse public keys
keySet, err := jwk.Fetch(THE_COGNITO_URL_DESCRIBED_ABOVE)

// Verify JWT token
token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
    // Check signing method
    if _, ok := token.Method.(*jwt.SigningMethodRS256); !ok {
        return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
    }

    // Extract key ID ("kid") from JWT header
    kid, ok := token.Header["kid"].(string)
    if !ok {
        return nil, errors.New("kid header not found")
    }

    // Find the public key
    keys := keySet.LookupKeyID(kid)
    if !ok {
        return nil, fmt.Errorf("key with specified kid is not present in jwks")
    }

    // Parse public key
    var publickey interface{}
    err = keys.Raw(&publickey)
    if err != nil {
        return nil, fmt.Errorf("could not parse pubkey")
    }

    return publickey, nil

Simplicity Regained in Go

By leveraging the jwx and jwt-go libraries, the process of validating and parsing JWT tokens issued by AWS Cognito becomes significantly simplified. This approach offers a clear and concise solution for authentication and authorization in Go.

The above is the detailed content of How to Easily Parse and Verify AWS Cognito JWT Tokens in Go?. For more information, please follow other related articles on the PHP Chinese website!