GoFiber never set HSTS header in helmet middleware due to incorrect protocol check
Summary
The helmet middleware in gofiber/fiber never sets the Strict-Transport-Security (HSTS) response header, even when HSTSMaxAge is explicitly configured, because the condition check at helmet.go:67 uses c.Protocol() — which returns the HTTP protocol version string (e.g., "HTTP/1.1", "HTTP/2.0") — instead of c.Scheme() — which returns the URL scheme ("http" or "https"). Since c.Protocol() never equals "https" in any real deployment, the HSTS header is permanently disabled, defeating the security protection.
Details
Root cause: middleware/helmet/helmet.go, line 67:
```go
if c.Protocol() == "https" && cfg.HSTSMaxAge != 0 {
```
c.Protocol() (defined at req.go:865-867) delegates to fasthttp.Request.Header.Protocol(), which returns the HTTP protocol version:
"HTTP/1.1" for HTTP/1.1 connections"HTTP/2.0" for HTTP/2 connections
The correct method is c.Scheme() (defined at req.go:844-862), which returns:
"http" for plain HTTP connections"https" for TLS connections
Since "HTTP/1.1" != "https" always evaluates to true, the entire HSTS block (lines 67-76) is dead code.
Note on test coverage: The existing helmet test (helmet_test.go) passes because it uses ctx.Request.Header.SetProtocol("https") to artificially force Protocol() to return "https". However, fasthttp.Request.Header.SetProtocol() sets the HTTP version field, and real HTTP requests never have protocol "https" — they have "HTTP/1.1" or "HTTP/2.0". The test is validating the wrong thing.
PoC
Clean-checkout maintainer-runnable recipe:
1. Save the following as middleware/helmet/poc_hsts_test.go:
```go
package helmet
import (
"crypto/tls"
"net/http/httptest"
"testing"
"github.com/gofiber/fiber/v3"
)
func Test_PoC_HSTS_NeverSet(t *testing.T) {
app := fiber.New()
app.Use(New(Config{
HSTSMaxAge: 31536000,
}))
app.Get("/", func(c fiber.Ctx) error {
return c.SendString("ok")
})
// Simulate HTTPS connection
req := httptest.NewRequest(fiber.MethodGet, "/", nil)
req.TLS = &tls.ConnectionState{}
resp, _ := app.Test(req)
hsts := resp.Header.Get("Strict-Transport-Security")
if hsts == "" {
t.Log("BUG CONFIRMED: HSTS header not set. c.Protocol() returns 'HTTP/1.1', not 'https'")
t.Log("Fix: change c.Protocol() == 'https' to c.Scheme() == 'https' on line 67")
}
}
```
2. Run: go test -run Test_PoC_HSTS_NeverSet -v ./middleware/helmet/
Expected vulnerable output:
```
=== RUN Test_PoC_HSTS_NeverSet
BUG CONFIRMED: HSTS header not set. c.Protocol() returns 'HTTP/1.1', not 'https'
Fix: change c.Protocol() == 'https' to c.Scheme() == 'https' on line 67
--- PASS: Test_PoC_HSTS_NeverSet
```
Expected output after fix:
```
=== RUN Test_PoC_HSTS_NeverSet
--- PASS: Test_PoC_HSTS_NeverSet
(HSTS header is set: "max-age=31536000; includeSubDomains")
```
Observed output from this environment (commit ee98695f):
```
=== RUN Test_PoC_HSTS_NeverSet
poc_hsts_test.go:39: HSTS header value: ""
poc_hsts_test.go:42: BUG CONFIRMED: HSTS header is NOT set even over TLS
poc_hsts_test.go:43: Root cause: helmet.go:67 uses c.Protocol() which returns HTTP version
poc_hsts_test.go:44: c.Protocol() returns 'HTTP/1.1' not 'https'
poc_hsts_test.go:45: Fix: use c.Scheme() == 'https' instead of c.Protocol() == 'https'
--- PASS: Test_PoC_HSTS_NeverSet
```
Negative/control case: With HSTSMaxAge: 0 (default), HSTS is correctly not set (this is expected behavior, not a bug).
Cleanup: Remove poc_hsts_test.go after verification.
Impact
The HSTS header is never applied in production, leaving all users vulnerable to:
- SSL stripping attacks: An active network attacker can downgrade HTTPS connections to HTTP, intercepting traffic between the client and server.
- Protocol downgrade: Without HSTS, browsers will silently accept HTTP connections to the site, even if the site supports HTTPS.
- Cookie theft over HTTP: Session cookies without the
Secure flag will be sent over HTTP if the user is tricked into an HTTP connection.
This affects any application that:
1. Uses the helmet middleware
2. Configures HSTSMaxAge > 0 expecting HSTS protection
3. Serves traffic over HTTPS
The vulnerability requires an active MITM attacker on the network path, which is realistic in public Wi-Fi, corporate networks, and ISP-level scenarios.
Suggested remediation
In middleware/helmet/helmet.go, line 67, replace c.Protocol() with c.Scheme():
```go
// Before (broken):
if c.Protocol() == "https" && cfg.HSTSMaxAge != 0 {
// After (fixed):
if c.Scheme() == "https" && cfg.HSTSMaxAge != 0 {
```
Additionally, update the existing test to use a realistic TLS simulation instead of SetProtocol("https"):
```go
// Before (artificial - sets HTTP versi
