Cache Poisoning in Buffalo with Cockroachdb

Cache poisoning in a Buffalo application using Cockroachdb occurs when an attacker manipulates cached responses so that malicious or incorrect data is served to subsequent users. Because Buffalo does not enforce strict cache-key scoping by default and Cockroachdb returns consistent, serializable results for identical queries, an attacker can inject parameters or headers that alter the cache key without invalidating the poisoned entry.

Consider a Buffalo endpoint that renders a user profile based on an ID passed via query string. If the response is cached with a key derived only from the ID and not the full request context (including headers such as Accept or Authorization), an authenticated user’s cached response might be reused for an unauthenticated request. Cockroachdb’s strong consistency means the data returned for a given ID is reliable, but it does not prevent the application from caching a response that should not be shared across contexts.

For example, an endpoint mapped as GET /users/:id might internally execute SELECT * FROM users WHERE id = $1. If caching is applied at the handler layer using a naive key like user-123, an attacker who can influence the cache key (e.g., via subdomain or header manipulation) may cause sensitive user data to be cached under a shared key and later retrieved by unrelated users. This is a cache poisoning vector specific to the interaction between Buffalo’s flexible routing and Cockroachdb’s predictable query outputs.

Additionally, if the application uses HTTP caching headers (e.g., Cache-Control: public, max-age=60) on responses that vary by authentication status or tenant, the cache may store a privileged response and serve it to lower-privileged users. Because Cockroachdb does not embed request context in its responses, the responsibility to vary cache keys correctly falls entirely on the application logic in Buffalo.

Real-world impacts include exposure of private user data, session confusion, and bypass of authorization checks. While this pattern is not a direct flaw in Cockroachdb, the database’s consistency guarantees can make poisoned cache entries persist longer and appear more reliable, increasing the severity of the exposure.

To remediate cache poisoning in Buffalo when using Cockroachdb, ensure that cache keys incorporate all request dimensions that affect the response, and avoid caching sensitive or user-specific data unless strictly isolated.

First, vary the cache key by tenant or user context when appropriate. For example, include the authenticated user’s ID or tenant slug in the cache key:

// In a Buffalo controller
func UsersShow(c buffalo.Context) error {
    userID := c.Params().Get("id")
    tenantID := c.Session().Get("tenant_id") // example tenant context
    cacheKey := fmt.Sprintf("user:%s:tenant:%s", tenantID, userID)
    var user User
    found, _ := c.Cache().Get(c.Request().Context(), cacheKey, &user)
    if !found {
        if err := db.Select(&user, "SELECT * FROM users WHERE id = $1", userID); err != nil {
            return c.Error(500, err)
        }
        // Cache with explicit expiration and tenant-aware key
        c.Cache().Set(c.Request().Context(), cacheKey, user, 5*time.Minute)
    }
    return c.Render(200, r.HTML("users/show.html"), user)
}

Second, avoid caching responses that contain private data unless the cache is isolated per user. For public, non-user-specific data, explicitly set Vary headers to ensure intermediaries respect request context:

// In a Buffalo controller for public data
func ArticlesIndex(c buffalo.Context) error {
    cacheKey := "articles:latest"
    var articles []Article
    found, _ := c.Cache().Get(c.Request().Context(), cacheKey, &articles)
    if !found {
        if err := db.All(&articles); err != nil {
            return c.Error(500, err)
        }
        c.Cache().Set(c.Request().Context(), cacheKey, articles, 10*time.Minute)
        // Instruct caches to vary by Authorization or Cookie if needed
        c.Response().Header().Set("Vary", "Authorization")
    }
    return c.Render(200, r.HTML("articles/index.html"), articles)
}

Third, when using Cockroachdb’s SERIALIZABLE isolation, ensure that read-only queries do not inadvertently share prepared statements or cached execution plans that depend on unvalidated inputs. Use parameterized queries consistently and avoid string interpolation in SQL strings within cached paths.

Finally, if you integrate middleBrick into your workflow, you can automatically detect cache-related misconfigurations during scans. The dashboard and CLI allow you to track these findings over time, and the GitHub Action can fail builds if new cache-sensitive endpoints are introduced without appropriate key diversification.