adds improvemement to CLI

main.go

@@ -0,0 +1,174 @@
+package main
+
+import (
+	"bytes"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/big"
+	"net/http"
+	"os"
+	"sort"
+
+	"github.com/urfave/cli"
+)
+
+type JWKeys struct {
+	Keys []JWKey `json:"keys"`
+}
+
+type JWKey struct {
+	Kty string `json:"kty"`
+	Use string `json:"use,omitempty"`
+	Kid string `json:"kid,omitempty"`
+	Alg string `json:"alg,omitempty"`
+
+	Crv string `json:"crv,omitempty"`
+	X   string `json:"x,omitempty"`
+	Y   string `json:"y,omitempty"`
+	D   string `json:"d,omitempty"`
+	N   string `json:"n,omitempty"`
+	E   string `json:"e,omitempty"`
+	K   string `json:"k,omitempty"`
+}
+
+var (
+	appName, appVer string
+)
+
+func main() {
+	app := cli.NewApp()
+	app.Name = appName
+	app.HelpName = appName
+	app.Usage = "Used for quick retrieval of public key from JWK"
+	app.Version = appVer
+	app.Copyright = ""
+	app.Authors = []cli.Author{
+		{
+			Name: "Rafpe ( https://rafpe.ninja )",
+		},
+	}
+
+	app.Commands = []cli.Command{
+		{
+			Name:  "pubkey",
+			Usage: "Get public key from JWKs",
+			Flags: []cli.Flag{
+				cli.StringFlag{
+					Name:  "url",
+					Usage: "URL from which details should be retrived",
+				},
+				cli.BoolFlag{
+					Name:  "show-kid",
+					Usage: "Show kid",
+				},
+			},
+			Action: cmdRetrievePublicKey,
+		},
+	}
+
+	sort.Sort(cli.FlagsByName(app.Flags))
+	sort.Sort(cli.CommandsByName(app.Commands))
+
+	app.Action = func(c *cli.Context) error {
+
+		return nil
+	}
+
+	err := app.Run(os.Args)
+	if err != nil {
+		fmt.Println(err)
+	}
+
+}
+
+func cmdRetrievePublicKey(c *cli.Context) error {
+	VerifyArgumentByName(c, "url")
+	url := c.String("url")
+
+	client := http.Client{}
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		fmt.Println(err)
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		fmt.Println(err)
+	}
+	defer resp.Body.Close()
+
+	byt, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		fmt.Println(err)
+	}
+
+	/*
+		Print out body
+	*/
+	//fmt.Println(string(byt))
+
+	jwsKeys := JWKeys{}
+	if err = json.Unmarshal([]byte(byt), &jwsKeys); err != nil {
+		fmt.Println(err)
+	}
+
+	for _, singleJWK := range jwsKeys.Keys {
+
+		if c.Bool("show-kid") {
+			fmt.Println(fmt.Sprintf("KID: %s", singleJWK.Kid))
+		}
+
+		if singleJWK.Kty != "RSA" {
+			log.Fatal("invalid key type:", singleJWK.Kty)
+		}
+
+		// decode the base64 bytes for n
+		nb, err := base64.RawURLEncoding.DecodeString(singleJWK.N)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		e := 0
+		// The default exponent is usually 65537, so just compare the
+		// base64 for [1,0,1] or [0,1,0,1]
+		if singleJWK.E == "AQAB" || singleJWK.E == "AAEAAQ" {
+			e = 65537
+		} else {
+			// need to decode "e" as a big-endian int
+			log.Fatal("need to deocde e:", singleJWK.E)
+		}
+
+		pk := &rsa.PublicKey{
+			N: new(big.Int).SetBytes(nb),
+			E: e,
+		}
+
+		der, err := x509.MarshalPKIXPublicKey(pk)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		block := &pem.Block{
+			Type:  "RSA PUBLIC KEY",
+			Bytes: der,
+		}
+
+		var out bytes.Buffer
+		pem.Encode(&out, block)
+		fmt.Println(out.String())
+
+	}
+
+	return nil
+}
+
+func VerifyArgumentByName(c *cli.Context, argName string) {
+	if c.String(argName) == "" {
+		log.Fatal(fmt.Sprintf("Please provide required argument(s)! [ %s ]", argName))
+	}
+}