Page History

package main

import (
        "context"
        "encoding/json"
        "fmt"
        "github.com/open-policy-agent/opa/rego"
        "io/ioutil"
        "net/http"
        "net/url"
        "os"
)

type Jwttoken struct {
        Access_token       string
        Expires_in         int
        Refresh_expires_in int
        Refresh_token      string
        Token_type         string
        Not_before_policy  int
        Session_state      string
        Scope              string
}

var token Jwttoken

var opaPolicy string = `
package authz

import future.keywords.in

default allow = false

jwks := jwks_request("http://keycloak:8080/auth/realms/opa/protocol/openid-connect/certs").body
filtered_jwks := [ key |
      some key in jwks.keys
      key.use == "sig"
    ]
token_cert := json.marshal({"keys": filtered_jwks})

token = { "isValid": isValid, "header": header, "payload": payload } {
        [isValid, header, payload] := io.jwt.decode_verify(input, { "cert": token_cert, "aud": "account", "iss": "http://keycloak:808
0/auth/realms/opa"})
}

allow {
    is_token_valid
}

is_token_valid {
        token.isValid
        now := time.now_ns() / 1000000000
        token.payload.iat <= now
        now < token.payload.exp
        token.payload.clientRole = "[opa-client-role]"
}

jwks_request(url) = http.send({
      "url": url,
      "method": "GET",
      "force_cache": true,
      "force_json_decode": true,
      "force_cache_duration_seconds": 3600 # Cache response for an hour
})
`

func getToken() string {
        clientSecret := "63wkv0RUXkp01pbqtNTSwghhTxeMW55I"
        clientId := "opacli"
        realmName := "opa"
        keycloakHost := "keycloak"
        keycloakPort := "8080"
        keycloakUrl := "http://" + keycloakHost + ":" + keycloakPort + "/auth/realms/" + realmName + "/protocol/openid-connect/token"        resp, err := http.PostForm(keycloakUrl,
                url.Values{"client_secret": {clientSecret}, "grant_type": {"client_credentials"}, "client_id": {clientId}})
        if err != nil {
                fmt.Println(err)
                panic("Something wrong with the credentials or url ")
        }
        defer resp.Body.Close()
        body, err := ioutil.ReadAll(resp.Body)
        json.Unmarshal([]byte(body), &token)
        return token.Access_token
}

func traceOpa(input string) {
        ctx := context.TODO()

        test := rego.New(
                rego.Query("x = data.authz.allow"),
                rego.Trace(true),
                rego.Module("example.rego", opaPolicy),
                rego.Input(input),
        )

        test.Eval(ctx)
        rego.PrintTraceWithLocation(os.Stdout, test)
}

func evaluateOpa(input string) {
        ctx := context.TODO()

        query, err := rego.New(
                rego.Query("x = data.authz.allow"),
                rego.Module("example.rego", opaPolicy),
        ).PrepareForEval(ctx)
        if err != nil {
                // Handle error.
                fmt.Println(err.Error())
        }

        results, err := query.Eval(ctx, rego.EvalInput(input))
        // Inspect results.
        if err != nil {
                // Handle evaluation error.
                fmt.Println("Error: " + err.Error())
        } else if len(results) == 0 {
                // Handle undefined result.
                fmt.Println("Results are empty")
        } else {
                // Handle result/decision.
                fmt.Printf("Results = %+v\n", results) //=> [{Expressions:[true] Bindings:map[x:true]}]
        }
  }

func main() {
        tokenStr := getToken()
        traceOpa(tokenStr)
        evaluateOpa(tokenStr)

}