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fix: generate token with alg not none when not vulnerable #85

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Merged
emmanuelgautier merged 1 commit into from
Sep 5, 2026
Merged

fix: generate token with alg not none when not vulnerable #85

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10 changes: 7 additions & 3 deletions challenges/jwt-alg-none-bypass/main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,13 +9,17 @@ import (
)

func generateToken(vulnerable bool) (string, error) {
token := jwt.NewWithClaims(jwt.SigningMethodNone, jwt.MapClaims{
claims := jwt.MapClaims{
"sub": "2cb307ba-bb46-4194-854f-4774046d9c9b",
"name": "John Doe",
"iat": time.Now().Unix(),
"exp": time.Now().Add(time.Hour).Unix(),
})
return token.SignedString(jwt.UnsafeAllowNoneSignatureType)
}
if vulnerable {
token := jwt.NewWithClaims(jwt.SigningMethodNone, claims)
return token.SignedString(jwt.UnsafeAllowNoneSignatureType)
}
return jwt.NewWithClaims(jwt.SigningMethodHS256, claims).SignedString([]byte(serve.Secret))
}

func main() {
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5 changes: 4 additions & 1 deletion challenges/jwt-alg-none-bypass/serve/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,9 @@ import (
"github.com/golang-jwt/jwt/v5"
)

// Secret is the HMAC secret used when the server runs in its fixed, non-vulnerable mode.
const Secret = "my_secret_key"

func RunServer(port string, vulnerable bool) {
mux := http.NewServeMux()
mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
Expand All @@ -28,7 +31,7 @@ func RunServer(port string, vulnerable bool) {
return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
}

return []byte("my_secret_key"), nil
return []byte(Secret), nil
})

if token != nil && token.Valid {
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