Use After Free in Chi with Cockroachdb

Use After Free (UAF) occurs when memory is deallocated but references to it remain in use, leading to unpredictable behavior or potential code execution. In the context of Chi (a lightweight HTTP router for Go) combined with CockroachDB, the interaction typically arises through connection pooling, prepared statement handles, or row scanning objects that may be reused after being released.

Chi itself does not manage database connections; it relies on the underlying database/sql interface. When using CockroachDB with the Go driver, developers often prepare statements or iterate over rows via Rows objects. If these objects are closed prematurely or if a handler reuses a pointer after the associated result set or prepared statement has been freed, a UAF condition can emerge. For example, launching a goroutine that references a *sql.Rows after the outer handler has returned can expose memory that has been reallocated, leading to data corruption or crashes.

Consider a scenario where a Chi route prepares a statement and defers cleanup, but an error path skips proper release while a background process still holds a reference. This pattern can surface in distributed transaction handling across CockroachDB nodes, where session states are long-lived and connection reuse is common. The risk is compounded when integrating with observability tools or middleware that capture references to request-scoped objects for logging or tracing, potentially keeping pointers alive beyond their intended lifecycle.

In security terms, UAF in this stack may not directly allow remote code execution under default configurations, but it can lead to information disclosure or denial of service. An attacker able to influence query parameters or timing might trigger the vulnerable code path repeatedly, causing instability or leaking adjacent memory contents during garbage collection cycles.

middleBrick detects such patterns indirectly through input validation and unsafe consumption checks when analyzing API behavior against CockroachDB endpoints. While it does not perform source-level memory analysis, its runtime scanning can highlight inconsistent error handling, missing context cancellation, or improper resource closure in API routes that interact with distributed SQL databases.

Developers should ensure deterministic cleanup of database resources and avoid capturing long-lived references to transient request objects. Using context timeouts and structured cancellation is essential when working with CockroachDB through Chi to prevent lingering pointers into freed memory.

To mitigate Use After Free risks when using Chi and CockroachDB, follow these patterns that ensure safe resource management and avoid retaining references to freed memory.

1. Always close rows and statements in the same execution path

Ensure that every Rows or Stmt object is closed before the function returns, even during error conditions. Use defer immediately after creation and avoid early returns that bypass cleanup.

import (
    "context"
    "database/sql"
    "net/http"

    "github.com/go-chi/chi/v5"
    _ "github.com/cockroachdb/cockroach-go/v2/crdb"
)

func getUserHandler(db *sql.DB) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        userID := chi.URLParam(r, "id")
        ctx := r.Context()

        rows, err := db.QueryContext(ctx, "SELECT id, name FROM users WHERE id = $1", userID)
        if err != nil {
            http.Error(w, "failed to query", http.StatusInternalServerError)
            return
        }
        defer rows.Close()

        var users []string
        for rows.Next() {
            var id int
            var name string
            if err := rows.Scan(&id, &name); err != nil {
                http.Error(w, "failed to scan", http.StatusInternalServerError)
                return
            }
            users = append(users, name)
        }
        if err := rows.Err(); err != nil {
            http.Error(w, "rows error", http.StatusInternalServerError)
            return
        }

        w.Write([]byte(users))
    }
}

2. Use context cancellation to prevent goroutine leaks

When passing database calls to background goroutines, always propagate the request’s context to ensure cancellation and avoid holding references after the HTTP request completes.

func backgroundAudit(db *sql.DB) {
    go func(ctx context.Context) {
        for {
            select {
            case <-ctx.Done():
                return
            default:
                var count int
                err := db.QueryRowContext(ctx, "SELECT count(*) FROM audit_log")
                if err != nil {
                    // handle error without blocking
                    return
                }
                // process audit safely
            }
        }
    }(r.Context())
}

3. Avoid global or cached pointers to result sets

Do not store references to *sql.Rows or *sql.Stmt in global variables or long-lived caches. If caching is required, copy the data into value types instead of holding pointers to database objects.

type UserProfile struct {
    ID   int
    Name string
}

func fetchProfile(db *sql.DB, userID int) (*UserProfile, error) {
    row := db.QueryRow("SELECT id, name FROM profiles WHERE id = $1", userID)
    var p UserProfile
    if err := row.Scan(&p.ID, &p.Name); err != nil {
        return nil, err
    }
    return &p, nil
}

4. Prefer parameterized queries over string building

Constructing SQL with string concatenation increases parsing complexity and can obscure resource ownership. Use placeholders consistently to let the driver manage statement lifecycle.

_, err := db.ExecContext(r.Context(),
    "INSERT INTO sessions (user_id, token) VALUES ($1, $2)",
    userID, token)
if err != nil {
    return err
}

By combining disciplined resource closure, context-aware execution, and avoidance of pointer retention, developers can effectively eliminate Use After Free conditions in Chi applications that interact with CockroachDB.