Heap Overflow in Fiber with Cockroachdb

A heap‑overflow risk arises in a Fiber service using CockroachDB when untrusted input is used to size buffers, deserialize payloads, or build SQL arguments that are passed to CockroachDB. In Go, this typically manifests as writing past the bounds of a slice or byte array that backs a CockroachDB client operation (for example, constructing a row value or a batch insert) based on attacker‑controlled length fields. Because CockroachDB drivers and ORM‑style helpers often allocate buffers from the heap, an oversized length can move the allocation to the heap, making the overflow persistent beyond the current function call and potentially corrupting internal metadata.

With this combination, the vulnerability is exposed across three dimensions:

• Language and runtime: Go’s lack of automatic bounds checks on slice headers means a programmer‑controlled index or length can overwrite adjacent heap metadata if a slice is manipulated unsafely (e.g., using unsafe.Pointer or CGO) while preparing data for CockroachDB.
• CockroachDB interaction: When request payloads are mapped into SQL arguments or row structures for CockroachDB, large or malformed field sizes can cause the driver or an intermediate buffer to allocate and copy data in an unbounded way, increasing the surface for heap corruption if length checks are missing.
• Fiber layer: Because Fiber keeps request handling hot and often reuses buffers for performance, a crafted request that triggers a large allocation for CockroachDB operations can overflow a heap‑based buffer that is reused across requests, turning a logic bug into a persistent memory corruption vector.

Consider an endpoint that reads a JSON data field and uses its length to preallocate a byte slice for a CockroachDB INSERT. If the length is not validated, an attacker can send a small JSON with a huge data length, causing the program to allocate a small-looking slice on the stack but then write far beyond it via an unchecked copy, corrupting the heap.

In practice, this class of issue can lead to arbitrary code execution when adjacent heap metadata is overwritten, and it becomes especially critical when the service performs sensitive operations against CockroachDB (e.g., financial transactions or multi‑tenant data isolation). Because the scanner category Input Validation tests for oversized payloads and missing length checks, such a flaw would be surfaced with high severity and guidance to enforce strict bounds and use safe abstractions.

Remediation centers on strict input validation, bounded copying, and safe use of CockroachDB drivers in Fiber handlers. Always validate and constrain sizes before allocating buffers, prefer streaming or chunked operations for large payloads, and avoid unsafe patterns when preparing data for CockroachDB.

Example 1: Safe bulk insert with size limits

Use a maximum page size and validate each field length before building rows for CockroachDB. This prevents unbounded heap allocations driven by attacker input.

// fiber-safe-cockroachdb.go
package main

import (
	"context"
	"fmt"
	"net/http"

	"github.com/gofiber/fiber/v2"
	"github.com/lib/pq" // assuming CockroachDB compatible wire protocol
)

const maxFieldSize = 1 << 20 // 1 MiB
const maxRows = 1000

type Record struct {
	ID   int64  `json:"id"`
	Data string `json:"data"`
}

func insertRecords(c *fiber.Ctx) error {
	var records []Record
	if err := c.BodyParser(&records); err != nil {
		return c.Status(http.StatusBadRequest).JSON(fiber.Map{"error": "invalid body"})
	}
	if len(records) > maxRows {
		return c.Status(http.StatusRequestEntityTooLarge).JSON(fiber.Map{"error": "too many rows"})
	}

	// Open a CockroachDB connection (use a real driver in production)
	conn, err := pq.Connect(context.Background(), "postgresql://user@localhost:26257/defaultdb?sslmode=disable")
	if err != nil {
		return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "db connect failed"})
	}
	defer conn.Close(context.Background())

	tx, err := conn.Begin(context.Background())
	if err != nil {
		return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "begin failed"})
	}

	stmt, err := tx.Prepare(context.Background(), "insert_record",
		`INSERT INTO records (id, data) VALUES ($1, $2)`)
	if err != nil {
		tx.Rollback(context.Background())
		return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "prepare failed"})
	}
	defer stmt.Close(context.Background())

	for _, rec := range records {
		if len(rec.Data) > maxFieldSize {
			tx.Rollback(context.Background())
			return c.Status(http.StatusRequestEntityTooLarge).JSON(fiber.Map{"error": "data field too large"})
		}
		_, err = stmt.Exec(context.Background(), rec.ID, rec.Data)
		if err != nil {
			tx.Rollback(context.Background())
			return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "exec failed"})
		}
	}
	if err := tx.Commit(context.Background()); err != nil {
		return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "commit failed"})
	}
	return c.SendStatus(http.StatusCreated)
}

Example 2: Bounded buffer for batch arguments

When constructing batch arguments for CockroachDB, cap the buffer size and copy with explicit bounds to avoid heap overflows.

// bounded-batch.go
package main

import (
	"context"
	"io"
	"net/http"

	"github.com/gofiber/fiber/v2"
)

const maxBatchBytes = 5 << 20 // 5 MiB

func uploadBatch(c *fiber.Ctx) error {
	// Limit the request body to prevent unbounded heap growth
	limited := io.LimitReader(c.Request().Body(), maxBatchBytes+1)
	data, err := io.ReadAll(limited)
	if err == io.ErrUnexpectedEOF {
		return c.Status(http.StatusRequestEntityTooLarge).JSON(fiber.Map{"error": "payload exceeds limit"})
	}
	if err != nil {
		return c.Status(http.StatusBadRequest).JSON(fiber.Map{"error": "read error"})
	}
	if int64(len(data)) > maxBatchBytes {
		return c.Status(http.StatusRequestEntityTooLarge).JSON(fiber.Map{"error": "payload exceeds limit"})
	}

	// Here you would parse data and build batch operations for CockroachDB
	// Use bounded loops and avoid unchecked copies into C-style or unsafe buffers.
	// For example, prefer driver-specific batch insert APIs that enforce limits.
	_, err = processBatchForCockroachDB(data)
	if err != nil {
		return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "batch failed"})
	}
	return c.SendStatus(http.StatusOK)
}

func processBatchForCockroachDB(payload []byte) (interface{}, error) {
	// Validate and process payload with strict size checks.
	// Example: iterate records using binary.Read with max sizes.
	return nil, nil
}

Additional operational guidance:

• Use the middleBrick CLI to scan your Fiber endpoints regularly: middlebrick scan <url>. This will highlight missing length checks and unsafe handling patterns that can lead to heap overflow when interacting with CockroachDB.
• If you use an OpenAPI spec, ensure definitions for request bodies include explicit maxLength or minimum/maximum for numeric fields; the spec analysis will cross-reference these with runtime findings.
• In production, combine these code-level fixes with the middleBrick Dashboard to track security scores over time and the GitHub Action to fail builds if a regression introduces a high-severity input validation issue.