Files
MealQuest/internal/server/csrf.go
T
dev_agentandClaude Opus 5.5 15cc3c5ce4
Independent review Codex gpt-6-sol high: APPROVED (0 findings)
CI / ci (pull_request) Successful in 1m27s
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Add CSRF protection and GET /api/v1/me
RequireSession now stores the validated session in the request context
(auth.WithSession / auth.SessionFrom); auth.ActorFrom derives the actor
from it, so there is one context value.

Every /api/v1 request other than GET, HEAD and OPTIONS must carry
X-MealQuest-CSRF equal to the session's csrf_token (constant-time
compare), else 403 {"error":{"code":"csrf"}}. The check runs after
RequireSession, so unauthenticated requests still get 401. A session
with no token is a 500, never a match against a missing header.

GET /api/v1/me returns {name, email, household: {label: "Our kitchen"},
csrfToken} with Cache-Control: no-store.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-03 10:32:31 -04:00

43 lines
1.4 KiB
Go

package server
import (
"crypto/subtle"
"log/slog"
"net/http"
"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/auth"
)
// CSRFHeader carries the session's CSRF token, which the client reads from
// GET /api/v1/me.
const CSRFHeader = "X-MealQuest-CSRF"
// requireCSRF passes GET, HEAD and OPTIONS requests to next; every other
// request must carry CSRFHeader equal to its session's CSRF token or get 403
// csrf. It runs behind requireSession, which puts the session in the context.
func requireCSRF(logger *slog.Logger) func(http.Handler) http.Handler {
forbidden := apiErrorHandler(logger, http.StatusForbidden, "csrf", "missing or invalid CSRF token")
internal := apiErrorHandler(logger, http.StatusInternalServerError, "internal", "internal error")
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
switch r.Method {
case http.MethodGet, http.MethodHead, http.MethodOptions:
next.ServeHTTP(w, r)
return
}
s, ok := auth.SessionFrom(r.Context())
if !ok || s.CSRFToken == "" {
// An empty token would match a missing header.
logger.ErrorContext(r.Context(), "csrf check without a session token", "session", ok)
internal(w, r)
return
}
if subtle.ConstantTimeCompare([]byte(r.Header.Get(CSRFHeader)), []byte(s.CSRFToken)) != 1 {
forbidden(w, r)
return
}
next.ServeHTTP(w, r)
})
}
}