Mass Assignment in Buffalo with Cockroachdb

Mass assignment in a Buffalo application using Cockroachdb occurs when form or JSON input is mapped directly to database columns without explicit allowlists. Buffalo encourages binding request parameters to models via form posts or JSON payloads; if the model includes sensitive or unintended fields, those values can be persisted to Cockroachdb because Cockroachdb accepts standard SQL INSERT and UPDATE statements generated by GORM or the database/sql layer. This becomes a vulnerability when user-controlled keys map to fields like is_admin, role, or deleted_at that should never be set by external input.

Because Cockroachdb is compatible with PostgreSQL wire protocol and SQL semantics, the same mass assignment risks that exist in other PostgreSQL backends apply. However, developers may assume Cockroachdb enforces stricter defaults or column-level protections, which is not the case. Without explicit parameter filtering or Go struct tags to control binding, Buffalo will happily populate any exported field that matches a form key or JSON key. This can lead to privilege escalation or data tampering when combined with Cockroachdb’s strong consistency and transactional guarantees that make injected changes durable immediately.

Real-world attack patterns include crafting a POST request with an extra parameter such as role=admin or is_active=true. If the Buffalo action uses c.Bind to map to a model and then saves via DB.Create, Cockroachdb will execute the SQL and persist the elevated values. Common OWASP API Top 10 risks like Broken Access Control map here, because the API effectively trusts input that should have been constrained. The scanner’s BFLA/Privilege Escalation and Property Authorization checks are designed to detect these unchecked binding paths and surface them with severity and remediation guidance.

To prevent mass assignment with Cockroachdb in Buffalo, use explicit allowlists when binding input and avoid binding directly to database models. Define separate input structs that include only the fields a client may set, and then map those fields to the database model. This ensures Cockroachdb receives only intended column values, regardless of extra keys in the request.

Example: Safe binding with an allowlist struct

// models/user.go
package models

type User struct {
	ID        int64
	Email     string
	HashedPass string
	Role      string
	CreatedAt time.Time
	UpdatedAt time.Time
}

// handlers/user_create.go — explicit allowlist binding
type CreateUserPayload struct {
	Email    string `json:"email"`
	Password string `json:"password"`
	// Role is intentionally omitted; default role is applied server-side
}

func CreateUser(c buffalo.Context) error {
	var payload CreateUserPayload
	if err := c.Bind(&payload); err != nil {
		return c.Render(400, r.JSON(err))
	}

	user := &models.User{
		Email:    payload.Email,
		HashedPass: hashPassword(payload.Password),
		Role:     "user", // server-determined default
	}

	if err := c.Session().DB().Create(user).Error; err != nil {
		// Cockroachdb returns specific error codes; handle unique violation, etc.
		return c.Render(500, r.JSON(map[string]string{"error": "failed to create user"}))
	}
	return c.Render(201, r.JSON(user))
}

Example: Selective updates with Omit

// handlers/user_patch.go
func UpdateUser(c buffalo.Context) error {
	user := c.Params().Get("user").(*models.User)
	var updates map[string]interface{}
	if err := c.Bind(&updates); err != nil {
		return c.Render(400, r.JSON(err))
	}

	// Explicitly remove sensitive keys if they somehow arrive
	delete(updates, "is_admin")
	delete(updates, "role")
	delete(updates, "deleted_at")

	if err := c.Session().DB().Model(user).Updates(updates).Error; err != nil {
		return c.Render(500, r.JSON(map[string]string{"error": "update failed"}))
	}
	return c.Render(200, r.JSON(user))
}

Schema considerations on Cockroachdb

Ensure your Cockroachdb schema uses server-side defaults for sensitive columns and, where possible, restrict application-level permissions used by Buffalo to a principle of least privilege. For instance, the database user for Buffalo should have INSERT/UPDATE rights on specific tables but not necessarily rights to alter schema or modify system columns like is_admin if they are managed by server-side triggers or defaults.