fetch-jwk

This library provides methods to fetch jwt keys from jwks url

Rationale

If you're using library like jwt-go for JWT validation you should supply Keyfunc that receives the JWT and returns public key for the JWT.

This library provides set of such key functions.

Usage

In the following example the JWT iss claim is test-issuer.com. If the OpenID Connect server discovery page URL is https://test-issuer.com/.well-known/openid-configuration (just like Goodle or Azure AD are) you can use FromIssuerClaim key function.

Otherwise you can use FromDiscoverURL or FromJWKsURL functions.

import (
    "fmt"
    jwkfetch "github.com/Soluto/fetch-jwk"
    jwt "github.com/dgrijalva/jwt-go"
)

var tokenString = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJleHAiOjE1MDAwLCJpc3MiOiJ0ZXN0LWlzc3Vlci5jb20iLCJhdWQiOiJ0ZXMtYXVkaWVuY2UifQ.dOUobGY8J6yxll7hGMWyQ9sVPsrCIjVNuFB1gsMhF4s"

token, err := jwt.Parse(tokenString, jwkfetch.FromIssuerClaim)

if token.Valid {
    fmt.Println("You look nice today")
} else if ve, ok := err.(*jwt.ValidationError); ok {
    if ve.Errors&jwt.ValidationErrorMalformed != 0 {
        fmt.Println("That's not even a token")
    } else if ve.Errors&(jwt.ValidationErrorExpired|jwt.ValidationErrorNotValidYet) != 0 {
        // Token is either expired or not active yet
        fmt.Println("Timing is everything")
    } else {
        fmt.Println("Couldn't handle this token:", err)
    }
} else {
    fmt.Println("Couldn't handle this token:", err)
}

JWK Caching

JWK that were used for JWT validation are cached and used to validate another JWT with same issuer.

Note: JWK are being changed usually every 24 hours. So the library refreshes the cache automatically every 24 hours.

If issuer or jwks_url are known in advance use Init method during your app startup.

API Reference

API reference documentation is here.

License

Licensed under the MIT License