Log Injection in Fiber with Cockroachdb

Log injection occurs when untrusted input is written directly into application logs without sanitization, enabling log forging or log injection attacks. In a Fiber application that uses CockroachDB, this typically arises when request-controlled data—such as user IDs, query parameters, or request IDs—is interpolated into structured log entries without validation or escaping. Because CockroachDB often serves as the backend for Fiber services, log entries may include database identifiers, SQL metadata, or connection-related details that can be influenced by an attacker through crafted requests.

Consider a scenario where a Fiber route logs user-supplied identifiers before executing a CockroachDB query:

app.Get("/users/:userID", func(c *fiber.Ctx) error {
    userID := c.Params("userID")
    log.Printf("Fetching user data for ID: %s", userID)
    row := db.QueryRowContext(c.Context(), "SELECT email FROM users WHERE id = $1", userID)
    // ...
})

If the attacker sends a request such as /users/attacker%0D%0AX-Forwarded-For:%20malicious, the injected newline characters can cause the log line to be split, allowing the attacker to inject fake metadata into the log stream. In distributed systems using CockroachDB, where request IDs and trace contexts are often logged alongside SQL statements, this can obscure the origin of operations or facilitate log forging. For example, an injected log entry might appear as a separate log event, making it difficult to correlate actions with the correct user or transaction.

Because CockroachDB exposes certain system columns and metadata (such as crdb_internal.node_statement_statistics or transaction timestamps), attackers might attempt to manipulate log entries to include sensitive internal details or to simulate legitimate operational messages. In a Fiber application that logs SQL execution details directly from CockroachDB responses, unsanitized fields like table names or constraint violations can be weaponized to inject structured log fragments that bypass simple text-based log parsers.

To prevent log injection in a Fiber application using CockroachDB, ensure that all data written to logs is sanitized and that structured logging is used where possible. Avoid direct string interpolation of user-controlled or database-derived values into log messages. Instead, use structured logging libraries that separate fields from message templates, preventing newline or formatting characters from altering log structure.

Below is a secure implementation example using structured logging with explicit field separation:

import (
    "context"
    "log/slog"
    "net/http"
    "github.com/gofiber/fiber/v2"
    "github.com/jackc/pgx/v5/pgxpool"
)

func setupDB() *pgxpool.Pool {
    // CockroachDB connection string
    connStr := "postgresql://root@localhost:26257/defaultdb?sslmode=disable"
    pool, err := pgxpool.New(context.Background(), connStr)
    if err != nil {
        panic(err)
    }
    return pool
}

func main() {
    db := setupDB()
    defer db.Close()

    app := fiber.New()

    app.Get("/users/:userID", func(c *fiber.Ctx) error {
        userID := c.Params("userID")
        // Use structured logging with explicit fields
        slog.Info("fetching user data",
            "user_id", userID,
            "operation", "select_email",
        )

        var email string
        err := db.QueryRow(c.Context(), "SELECT email FROM users WHERE id = $1", userID).Scan(&email)
        if err != nil {
            slog.Warn("database query failed",
                "user_id", userID,
                "error", err.Error(),
            )
            return c.Status(http.StatusInternalServerError).SendString("internal error")
        }

        slog.Info("user data retrieved",
            "user_id", userID,
            "email", email,
        )
        return c.JSON(fiber.Map{"email": email})
    })

    app.Listen(":3000")
}

In this example, slog is used to ensure that log entries are emitted as structured data, with each field clearly separated. Newline and other control characters in userID or error messages are treated as plain text values rather than log-formatting instructions. This approach neutralizes injection attempts that rely on line breaks or special characters to manipulate log parsers.

Additionally, ensure that any logging derived from CockroachDB internal objects—such as error messages containing schema or table names—is sanitized before emission. For example, if a database constraint violation returns a message like pq: duplicate key value violates unique constraint "users_email_key", extract only the necessary, sanitized information rather than logging the raw message directly.