Container Image Scanning:

In a summary of the book titled "Effective Vulnerability Management”, we brought up how container images have become relevant in today’s security assessment. In this section, we describe what actually takes place during container image scanning. Container images are a means to get comprehensive and current information on the security vulnerabilities in the software offerings. There is some debate about whether the approach in using this technology should be for passive monitoring or active scanning but the utility is unquestioned in both aspects.

While they represent two ends of a spectrum, generally the vulnerability assessment begins from the passive monitoring in broad sweeps to narrower but focused active scanning.  Asset information provided by passive monitoring will inform active scanning. Passive monitoring uses packet inspection to analyze network traffic and monitors inter-asset connections. Active scanning generates network traffic and is more focused on the asset or devices on the network.

Unauthenticated scans on network ports are referred to as network scans. They examine device from outside-in. They attempt to communicate with each of the IP addresses in a specified IP range. Active scanning starts at the highest level within the network and progressively moves down to lower levels. This step-down occurs in graded manner and over an evaluation period

When a scan is run, a container is seen as a form of layers. Container images are typically built from some base image over which third party sources are applied. These images and libraries may contain obsolete or vulnerable code. Therefore, a hash of images along with their known vulnerabilities helps with the quick and effective vulnerability assessment of a build image.  Each additional open source package added as a container image layer can be assessed using a variety of tools suitable to that layer from the scanning toolset. Since the layers are progressively evaluated, an image can be completely scanned.

Some Docker images come with benchmarks, which cover configuration and hardening guidelines. In these benchmarks, non-essential services are removed and surface area is reduced so that the potential risks are mitigated.  Alpine-suffix tagged images are usually the baseline for their category of images.

As with all asset management, images can also be classified as assets. Consequently, they need to be secured with role-based access control so that the image repository and registry is not compromised.

These salient features can be enumerated as steps with the following list:

1. Know the source and content of the images.

2. Minimize risks from the containers by removing or analyzing layers.

3. Reduce the surface area in images, containers and hosts

4. Leverage the build integration tools to do it on every image generation

5. Enforce the role segregation and access control for your Docker environment

6. Automate the detection actions and enforcement such as failing a build

7. Routinely examine the registries and repositories to prevent sprawl.

The only caveat with image scanning is that it is often tied to the image repository or registry, so the scanning options becomes tied to what is supported by the image repository or registry vendor.

#codingexercise 

Problem: Count the number of ways to climb up the staircase and we can modify the number of steps at any time to 1 or 2

Solution: int getCount(int n)

{

    int [] dp = new int[n+2];

    dp [0] = 0;

    dp [1] = 1;

    dp [2] = 2;

    for (int k = 3; k <= n; k++) {

                 dp [k] = dp [k-1] + dp [k-2];

    }

   return dp [n];

}