Ruby Code Vulnerability Analysis: ConfirmSnsSubscription RCE

Overview

The security flaws discovered in the Ruby code snippet for the ConfirmSnsSubscription class have been thoroughly examined in this report.

The remote code execution (RCE) vulnerability was the main focus of the code review to find any potential security problems. The paper lists the vulnerabilities that were found, such as poor input validation and unsafe URL processing, and offers doable advice to resolve these issues.

By putting the proposed changes into practise, the codebase’s overall security posture may be improved, reducing the dangers of unauthorised code execution and potential attacks.

Vulnerable Code Snippet

module Jobs

  class ConfirmSnsSubscription < ::Jobs::Base
    sidekiq_options retry: false

    def execute(args)
      return unless raw = args[:raw].presence
      return unless json = args[:json].presence
      return unless subscribe_url = json["SubscribeURL"].presence

      require "aws-sdk-sns"
      return unless Aws::SNS::MessageVerifier.new.authentic?(raw)

      # confirm subscription by visiting the URL
      open(subscribe_url)
    end

  end

end

The possibility for Remote Code Execution (RCE) is the flaw in the code snippet. The following line of code causes this vulnerability:

open(subscribe_url)

Without any verification or sanitization, the code just opens and navigates to the subscribe_url. The subscribe_url option may be manipulated by an attacker to contain malicious code or a URL pointing to a malicious script. The server hosting this code snippet might execute arbitrary code if the open function is invoked on this URL.

Unauthorised commands or malicious scripts might be executed on the server by an attacker using this vulnerability if the subscribe_url argument is not properly validated and sanitised, jeopardising the security of the system.

Findings

1. Lack of Input Validation:

• Inputs like subscribe_url, raw, and json don’t get the required validation and sanitization in the code. This may result in a number of security problems, such as code injection and malicious URL execution.

2. RCE Vulnerability:

• Without any validation or sanitization, the open(subscribe_url) statement opens and accesses the subscribe_url. RCE may be caused by an attacker using the subscribe_url option to run arbitrary code on the server.

3. Absence of Error Handling:

• There are no facilities for managing errors in the code. The code will not be handled correctly if an error, such as a network problem or a URL with a mistake, happens while it is being run, which might result in crashes or strange behaviour.

4. Insecure Dependency Usage:

• The Aws::SNS::MessageVerifier is imported from the aws-sdk-sns gem without checking the gem’s integrity or specifying a particular gem version. Utilising old or vulnerable dependencies might result in danger.

Compliant Solution

The code must properly validate and sanitise the subscribe_url argument in order to resolve the issue and prevent Remote Code Execution (RCE). Here is the code that has been modified to address the vulnerability:

require "open-uri"

module Jobs
  class ConfirmSnsSubscription < ::Jobs::Base
    sidekiq_options retry: false

    def execute(args)
      return unless raw = args[:raw].presence
      return unless json = args[:json].presence
      return unless subscribe_url = json["SubscribeURL"].presence

      require "aws-sdk-sns"
      return unless Aws::SNS::MessageVerifier.new.authentic?(raw)

      # Fixed: Validate and sanitize the subscribe_url before opening
      if safe_url?(subscribe_url)
        open(sanitize_url(subscribe_url))
      else
        raise "Invalid subscribe_url"
      end
    end

    private

    def safe_url?(url)
      # Implement URL validation logic here, e.g., using a whitelist approach
      # to allow only trusted and expected URLs.
      # Example validation logic:
      whitelist = ["https://trusted-example.com", "https://another-trusted-url.com"]
      whitelist.include?(url)
    end

    def sanitize_url(url)
      # Implement URL sanitization logic here, if required.
      # This step is to ensure the URL is safe and free from any potentially malicious parts.
      # You may use appropriate methods or libraries to sanitize the URL.
      url
    end
  end
end

A new safe_url? function is added in the modified code to handle URL checking. The correct logic should be implemented within this function to check the subscribe_url against a whitelist of approved and anticipated URLs. This makes sure that only secure URLs may be viewed.

There is also a sanitize_url function available if the URL has to be cleaned up. This phase verifies that the URL is clear of any components that may be harmful. To execute URL sanitization, you can make use of the appropriate techniques or frameworks.

These modifications allow the code to check and sanitise the subscribe_url argument, effectively reducing the RCE vulnerability by only allowing trustworthy and secure URLs to be viewed.

Conclusion

Because input is not validated and URLs are handled insecurely, the code sample for the ConfirmSnsSubscription class has serious security flaws, including the possibility for Remote Code Execution (RCE).

Implementing input validation, sanitization, and secure coding practises is essential to addressing these issues. The codebase’s security posture will be further improved by adding error handling features and maintaining dependencies.

To guarantee continuous security and reduce any new threats, regular security testing and reviews are advised.

原文始发于ASWIN K V：Ruby Code Vulnerability Analysis: ConfirmSnsSubscription RCE