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sec(api): renderAuthError Cache-Control: no-store + lang=en (BUG-API-257/404) #196

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Merged
mastermanas805 merged 1 commit into from
May 30, 2026
Merged

sec(api): renderAuthError Cache-Control: no-store + lang=en (BUG-API-257/404) #196

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20 changes: 19 additions & 1 deletion internal/handlers/auth.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1131,8 +1131,26 @@ func (h *AuthHandler) consumeOAuthState(ctx context.Context, state string) bool
// remember to escape — defense in depth.
func renderAuthError(c *fiber.Ctx, status int, headline, detail string) error {
c.Set("Content-Type", "text/html; charset=utf-8")
// BUG-API-404 (QA 2026-05-29): the OAuth / magic-link callback HTML
// is a per-request rendering of session-bound state — a back-button,
// browser-history-restore, or service-worker re-fetch must NOT replay
// it (the underlying token has been consumed or expired). Without
// Cache-Control, the body could be re-served by the browser fetch
// cache or any intermediary, which both leaks the "you tried this
// link" UX state across sessions AND, in the success-redirect cousin
// of this surface, would re-set the exchange cookie. `no-store`
// (RFC 9111 §5.2.2.5) is the strongest stop-cache directive and
// matches the contract every other auth-result surface in the api
// already follows.
c.Set(fiber.HeaderCacheControl, "no-store")
// BUG-API-257 (QA 2026-05-29): the <html> element used to ship with
// no `lang` attribute. WCAG 3.1.1 "Language of Page" requires a
// programmatically determinable primary language; assistive tech
// (VoiceOver, NVDA) falls back to the OS locale otherwise, mis-
// pronouncing English copy in non-English locales. `lang="en"` is
// the correct value for the static English-only copy below.
body := fmt.Sprintf(`<!DOCTYPE html>
<html>
<html lang="en">
<head><meta charset="UTF-8"><title>Sign-in error</title></head>
<body style="font-family:sans-serif;max-width:480px;margin:48px auto;padding:24px;color:#111;">
<h2>%s</h2>
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12 changes: 12 additions & 0 deletions internal/handlers/auth_helpers_coverage_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -263,12 +263,24 @@ func TestAuth_RenderAuthError_StatusAndContentType(t *testing.T) {
defer resp.Body.Close()
assert.Equal(t, http.StatusBadRequest, resp.StatusCode)
assert.Contains(t, resp.Header.Get("Content-Type"), "text/html")
// BUG-API-404 (QA 2026-05-29): the OAuth / magic-link callback HTML
// is per-request session-bound state — back-button or service-worker
// re-fetch must NOT replay it. Pin Cache-Control: no-store so a
// future regression that drops the c.Set call fails before merge.
assert.Equal(t, "no-store", resp.Header.Get("Cache-Control"),
"BUG-API-404: renderAuthError must stamp Cache-Control: no-store on every callback HTML response")
buf := make([]byte, 1024)
n, _ := resp.Body.Read(buf)
body := string(buf[:n])
assert.Contains(t, body, "<title>Sign-in error")
assert.Contains(t, body, "Hello")
assert.Contains(t, body, "Detail")
// BUG-API-257 (QA 2026-05-29): WCAG 3.1.1 — the <html> element MUST
// carry a lang attribute so assistive tech (VoiceOver, NVDA) doesn't
// fall back to the OS locale and mispronounce English copy. Pin the
// value here so a future revert to the bare <html> fails before merge.
assert.Contains(t, body, `<html lang="en">`,
"BUG-API-257: renderAuthError HTML must include lang=\"en\" on the <html> element (WCAG 3.1.1)")
}

// SEC-API FINDING-23 regression: renderAuthError must HTML-escape both
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