Insecure Deserialization in Fiber with Cockroachdb
Insecure Deserialization in Fiber with Cockroachdb
Insecure deserialization occurs when an application processes untrusted data into object instances without sufficient validation. In a Fiber application that uses Cockroachdb as the backend data store, the risk is not that Cockroachdb performs deserialization on attacker-controlled data, but that the application layer constructs objects from request payloads and then uses those objects to build queries or interpret results from Cockroachdb. If the application deserializes JSON, form values, or custom formats into Go structs and then passes field values directly to SQL without strict validation, attackers can manipulate types, inject unexpected values, or exploit mismatches between the application’s expectations and the database schema.
Consider a Fiber handler that decodes a JSON body into an interface{} or a loosely typed map and then uses type assertions to construct SQL arguments for Cockroachdb. Because Cockroachdb is compatible with PostgreSQL wire protocol, it supports rich data types including arrays, JSONB, and composite types. If the application deserializes a JSON payload into a generic map[string]interface{} and then injects values into a Cockroachdb query via string concatenation or insufficiently parameterized statements, attackers can supply nested structures, booleans, or numbers that change the intended SQL logic. For example, a price field expected to be a decimal might be replaced with a JSON object that, when converted to string, produces unexpected SQL syntax or exposes internal schema details through error messages.
Another scenario involves session or token deserialization. If the application stores user permissions or roles in a serialized blob (e.g., JSON or gob) and later deserializes it to make authorization decisions before querying Cockroachdb, tampering with that blob can lead to privilege escalation. Because Cockroachdb may return user data based on identifiers deserialized from client-supplied tokens, an attacker who modifies a serialized payload to change a user ID could leverage BOLA/IDOR to access other users’ records. The combination of Fiber’s high-performance routing and Cockroachdb’s distributed SQL engine means that unchecked deserialization can quickly lead to unauthorized data access or inconsistent enforcement of property-level authorization.
To detect this pattern, middleBrick runs checks for unsafe consumption of serialized data and input validation while also analyzing OpenAPI specs for endpoints that accept loosely typed payloads and interact with database operations. When scanning a Fiber service that communicates with Cockroachdb, middleBrick flags endpoints where request bodies are unmarshaled into interface{} or where type assertions are used to construct SQL arguments without strict schema validation.
Cockroachdb-Specific Remediation in Fiber
Remediation focuses on strict schema validation, typed structures, and safe database interactions. Avoid deserializing into generic types such as interface{} for data that will influence SQL construction. Instead, define explicit structs that mirror expected request shapes and use strong validation libraries. When working with Cockroachdb, always use parameterized queries so that values are never interpreted as SQL syntax, regardless of their type.
Example: Safe Struct-Based Handling with Cockroachdb
Define a concrete request structure and validate each field before using it in a query against Cockroachdb. Use placeholders ($1, $2) for parameterized statements.
package main
import (
"context"
"net/http"
"strconv"
"github.com/gofiber/fiber/v2"
"github.com/jackc/pgx/v5/pgxpool"
)
type CreateProductRequest struct {
Name string `json:"name" validate:"required,min=1,max=200"`
Price int64 `json:"price" validate:"required,min=0"`
Stock int32 `json:"stock" validate:"required,min=0"`
}
func main() {
pool, err := pgxpool.New(context.Background(), "postgres://user:pass@host:26257/db?sslmode=require")
if err != nil {
panic(err)
}
defer pool.Close()
app := fiber.New()
app.Post("/products", func(c *fiber.Ctx) error {
var req CreateProductRequest
if err := c.BodyParser(req); err != nil {
return c.Status(http.StatusBadRequest).JSON(fiber.Map{"error": "invalid request"})
}
// In a real app, use a validator middleware to enforce struct tags.
// For brevity, validation is assumed to pass.
query := `INSERT INTO products (name, price, stock) VALUES ($1, $2, $3) RETURNING id`
var productID int64
if err := pool.QueryRow(c.Context(), query, req.Name, req.Price, req.Stock).Scan(&productID); err != nil {
return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "database error"})
}
return c.JSON(fiber.Map{"id": productID})
})
app.Listen(":3000")
}
This approach ensures that each field matches an expected Go type before reaching Cockroachdb. The use of $1, $2, $3 placeholders ensures that integer, string, and other typed values are sent as parameters, preventing type confusion or SQL injection via crafted JSON numbers or nested objects.
Handling Arrays and JSONB Safely
If your Fiber service must work with JSONB columns in Cockroachdb, deserialize into a known Go type (such as a struct or a map[string]interface{} with strict validation) and pass the value as a parameterized argument. Do not concatenate JSON strings into SQL.
package main
import (
"context"
"encoding/json"
"net/http"
"github.com/gofiber/fiber/v2"
"github.com/jackc/pgx/v5/pgxpool"
)
func updateMetadata(c *fiber.Ctx) error {
pool := c.Locals("dbpool").(*pgxpool.Pool)
var input struct {
ID int64 `json:"id" validate:"required,min=1"`
Metadata json.RawMessage `json:"metadata" validate:"required"`
}
if err := c.BodyParser(&input); err != nil {
return c.Status(http.StatusBadRequest).JSON(fiber.Map{"error": "invalid body"})
}
// Validate metadata structure here if needed
var metadata map[string]interface{}
if err := json.Unmarshal(input.Metadata, &metadata); err != nil {
return c.Status(http.StatusBadRequest).JSON(fiber.Map{"error": "invalid metadata format"})
}
query := `UPDATE products SET metadata = $1 WHERE id = $2`
if _, err := pool.Exec(c.Context(), query, input.Metadata, input.ID); err != nil {
return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "update failed"})
}
return c.SendStatus(http.StatusOK)
}
By unmarshaling into json.RawMessage first, you can perform schema checks or size limits before sending the value as a parameterized argument. This prevents attackers from injecting unexpected types that could alter query behavior when interpreted by Cockroachdb’s JSONB operators.
Authorization Before Data Access
Ensure that any identifiers extracted from deserialized tokens or request parameters are verified against the database using parameterized queries. Never construct WHERE clauses by string interpolation, even when the identifier originates from a trusted-looking token.
package main
func getUserProfile(c *fiber.Ctx) error {
pool := c.Locals("dbpool").(*pgxpool.Pool)
userID, err := strconv.ParseInt(c.Params("id"), 10, 64)
if err != nil {
return c.Status(http.StatusBadRequest).JSON(fiber.Map{"error": "invalid user id"})
}
var username string
query := `SELECT username FROM users WHERE id = $1`
if err := pool.QueryRow(c.Context(), query, userID).Scan(&username); err != nil {
return c.Status(http.StatusInternalServerError).JSON(fiber.Map{"error": "database error"})
}
return c.JSON(fiber.Map{"username": username})
}
Using explicit integer parsing and parameterized queries ensures that even if an attacker manipulates the URL or token, the resulting SQL sent to Cockroachdb remains safe and type-consistent.