Insecure Mass Assignment¶

ID: rb/insecure-mass-assignment
Kind: path-problem
Security severity: 9.8
Severity: error
Precision: high
Tags:
   - security
   - external/cwe/cwe-915
Query suites:
   - ruby-code-scanning.qls
   - ruby-security-extended.qls
   - ruby-security-and-quality.qls

Click to see the query in the CodeQL repository

Operations that allow for mass assignment (setting multiple attributes of an object using a hash), such as ActiveRecord::Base.new, should take care not to allow arbitrary parameters to be set by the user. Otherwise, unintended attributes may be set, such as an is_admin field for a User object.

Recommendation¶

When using a mass assignment operation from user supplied parameters, use ActionController::Parameters#permit to restrict the possible parameters a user can supply, rather than ActionController::Parameters#permit!, which permits arbitrary parameters to be used for mass assignment.

Example¶

In the following example, permit! is used which allows arbitrary parameters to be supplied by the user.

class UserController < ActionController::Base
    def create
        # BAD: arbitrary params are permitted to be used for this assignment
        User.new(user_params).save!
    end

    def user_params
        params.require(:user).permit!
    end
end

In the following example, only specific parameters are permitted, so the mass assignment is safe.

class UserController < ActionController::Base
    def create
        # GOOD: the permitted parameters are explicitly specified
        User.new(user_params).save!
    end

    def user_params
        params.require(:user).permit(:name, :email)
    end
end

References¶

Rails guides: Strong Parameters.
Common Weakness Enumeration: CWE-915.

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