Technical Details¶

easy_infra.yml¶

easy_infra is a project which makes heavy use of generated code and composable container images. easy_infra.yml is the centralized configuration to instruct those generation and composition processes. It describes which version of software to use, where, how to generate the very important /functions.sh script (more on that in functions.sh and functions.j2), which is what provides all of the hooking and capabilities.

Here is a fictitious easy_infra.yml that concisely demonstrates the various features that are possible:

_anchors:
  file_extensions: &id001
  - tf
  security: &id002
    checkov:
      command: checkov -d . --download-external-modules True --skip-download --output
        json --output-file-path ${CHECKOV_JSON_REPORT_PATH}/checkov.json,
      arg_customizations:
        CHECKOV_BASELINE: --baseline
      env_customizations:
        CHECKOV_LOG_LEVEL: LOG_LEVEL
      description: directory scan
  validation: &id003
  - command: terraform init -backend=false
    description: initialization
  - command: terraform validate
    description: validation
packages:
  fluent-bit:
    helper: ["all"]
    version: v2.0.5
    version_argument: --version
  checkov:
    allow_update: False
    version: 2.2.8
    version_argument: --version
  tfenv:
    aliases:
    - tfe
    allow_filter:
    - match: exec
      position: 0
    file_extensions: *id001
    helper: ["terraform"]
    security: *id002
    monitor:
      env_vars:
        - TF_DATA_DIR
    tool:
      name: customname
      environments:
      - none
      - aws
      - azure
    validation: *id003
    version: v3.0.0
    version_argument: --version

Note

Not all of these features are always in use in easy_infra.yml

YAML Anchors and Aliases¶

Anchors and Aliases are a yaml concept, and are fully supported in easy_infra.yml to support reusable components. See &id001 and *id001 above to see an example. Learn more here and here.

Packages¶

All of the terms under packages are the names of packages, and the details of how and when they are installed are described in that object of the easy_infra.yml. In order to register a runtime hook against a package (Learn more about hooks here), or define what security scans occur prior to executing, it must be defined under packages.

Alias¶

Certain tools have multiple ways to run them, such as by running kubectl or simply k. These aliases often point to the exact same binary, and if you’d like to support multiple aliases for a tool, provide a list of those aliases under aliases in easy_infra.yml, which will result in /functions.sh containing an appropriate function hook for each of the aliases.

Allow filter¶

The allow_filter allows you to perform security scans only for a very specific sub-command of a given package or alias. For instance, in the above example, we have:

tfenv:
  allow_filter:
  - match: exec
    position: 0

This ensures that, in the generated tfenv function in /functions.sh, it will check for exec in the 0 position (0-indexed, starting after the command, and after any easy_infra specific arguments have been removed (i.e. --skip-checkov)), and only if there’s a match will it continue to perform security scans as described in the security object under the respective package (i.e. tfenv).

Allow update¶

When projects are added to easy_infra they are automatically on-boarded to our automated maintenance scripts (see def update in tasks.py for how that works). All projects that are properly configured will be automatically updated when invoke update is run, and allow_update is a boolean field under that package in easy_infra.yml which allows the on-boarding of a package, while exempting it from automatic updates. This is typically temporary, and only done when a given project changes how it performs releases or makes a breaking changes that we have yet to accommodate.

File extensions¶

file_extensions exist to support the AUTODETECT function. If a package doesn’t have file extensions defined, the project’s autodetect logic is unable to detect where files that relate to the command being run exist.

Monitor¶

The monitor section is how you can specify which additional locations on the filesystem we should monitor for changes to determine if we should rerun the security scans. For instance, if AUTODETECT is true and you’re running a command in multiple directories, and/or if you’re chaining commands which may modify the filesystem.

Monitor currently only supports a env_vars key containing a list of names of environment variables that the related tool uses to identify alternative locations to store runtime-critical files. This may be expanded in the future.

Security¶

The backbone of this project is the security section. All of the terms underneath security define the series of security tools which will be run every time the related command is run. An alternative easy_infra.yml would look something like this:

packages:
  checkov:
    version: 2.2.8
    version_argument: --version
  kics:
    version: v1.5.1
    version_argument: version
  tfenv:
    aliases:
    - tfe
    allow_filter:
    - match: exec
      position: 0
    file_extensions:
    - .tf
    security:
      checkov:
        command: checkov -d . --download-external-modules True --skip-download --output
          json --output-file-path ${CHECKOV_JSON_REPORT_PATH}/checkov.json,
        arg_customizations:
          CHECKOV_BASELINE: --baseline
          CHECKOV_EXTERNAL_CHECKS_DIR: --external-checks-dir
          CHECKOV_SKIP_CHECK: --skip-check
        env_customizations:
          CHECKOV_LOG_LEVEL: LOG_LEVEL
        description: directory scan
      kics:
        command: kics scan --type Terraform --no-progress --queries-path ${KICS_INCLUDE_QUERIES_PATH}
          --libraries-path ${KICS_LIBRARY_PATH} --report-formats json --output-path
          ${KICS_JSON_REPORT_PATH} --output-name kics --path .
        arg_customizations:
          KICS_EXCLUDE_SEVERITIES: --exclude-severities
          KICS_INCLUDE_QUERIES: --include-queries
        description: directory scan
    version: v3.0.0
    version_argument: --version

After building easy_infra with this configuration, you should be able to expect that when you run tfenv exec init inside of an easy_infra container, then it would run both the kics and checkov security tools as described under kics: command: ... and checkov: command: ..., with additional arg_ or env_ customizations as defined under security_tool: arg_customizations: ... or security_tool: env_customizations: ..., when the associated environment variables are set.

As an example, if you ran tfenv exec init and also had the CHECKOV_BASELINE environment variable set to /iac/.checkov.baseline then the actual checkov command that would be run would be:

checkov -d . --download-external-modules True --skip-download --output json --output-file-path ${CHECKOV_JSON_REPORT_PATH}/checkov.json,
--baseline /iac/.checkov.baseline

Note

The --baseline ... at the end was dynamically added due to the environment variable.

Tool¶

If you have a situation where you’d like the tool to have a different name from the package, you can simply add the optional tool key in your easy_infra.yml, along with a name sub-key, and then it will use the provided value during building and testing. A good example of this is the aws-cli package and the cloudformation tool (which is technically aws cloudformation commands inside the container).

If your tool only supports a subset of all the possible environments, you can specify environments as a sub-key under the optional tool. For instance, our cloudformation images are not relevant to azure.

Validation¶

Sometimes security scanning tools are only equipped to run against IaC which is in a certain state, such as ensuring that the IaC is formatted properly and valid. validation is where you can specify what those are, and you can specify a list of commands to run in the specified order, prior to running the security scanning tools.

Version¶

version is where you can specify which versions of tool you want to include when you’re building an easy_infra image. This is what is maintained by this project’s automated maintenance scripts, and it is parsed into build arguments which are passed into the container image building process.

Version Argument¶

version_argument is a way for us to describe how a command requests its version inside of easy_infra. This is useful to know because we avoid running security scans (and validation, if any is specified) when the version of a tool is being queried inside of an easy_infra container.

build/¶

All build/Dockerfile* files must all be able to be built independently, as long as their pre-requisites are met. Typically this means you pass in the appropriate *_VERSION build arguments, and you pass in an EASY_INFRA_TAG build argument that maps to a seiso/easy_infra_base tag locally. For example, a command like the following should work when run from the build directory if seiso/easy_infra_base:2022.11.06-terraform-943a052 is available locally:

docker build -t ansible-test --build-arg ANSIBLE_VERSION=2.9.6+dfsg-1 --build-arg EASY_INFRA_TAG=2022.11.06-terraform-943a052 . -f
Dockerfile.ansible

All build/Dockerfrag* files cannot be built individually and are only fragments of an image specification. They are meant to be layered on top of their respective Dockerfile.

functions.sh and functions.j2¶

functions.j2 is a Jinja2 template, which is rendered into a functions script, and then copied into each easy_infra image at build time. This all works based on the combination of this /functions.sh file existing inside of the container, commands being run from within a shell (whether or not you specify bash -c or not when running a container), and the BASH_ENV environment variable pointing to /functions.sh. The way that we ensure that all commands are run inside a shell is by using "$@" in the easy_infra image entrypoint of docker-entrypoint.sh.

Because BASH_ENV will ensure that /functions.sh is loaded into the shell at initialization, and /functions.sh contains functions which match the name of tools which we are protecting, we can use those functions to perform security scans, arbitrary hooks, and logging prior to executing the original command.

Ultimately, this means that when you run terraform (or some other properly defined package in easy_infra.yml) inside of easy_infra, it will actually run the function “terraform”, which will run the security scans, hooks, and logging, and only after evaluating the precursor logic will it run command terraform which runs the terraform binary from the PATH.

Marking Git Directories Safe¶

As of git version 2.35.2, git safe.directory was added to mitigate CVE-2022-24765; however, support for configuration of safe directories via environment variables was not added until 2.38.0. We decided using environment variables was best way to do this, because it is the most dynamic.

Mounted directories must be considered “safe” by git, in order for logging to function properly. When mounting a .git folder into the container, the following variables work together to flag it as a safe directory for git:

export GIT_CONFIG_COUNT=1
export GIT_CONFIG_KEY_0="safe.directory"
GIT_CONFIG_VALUE_0="$(git rev-parse --show-toplevel 2>/dev/null || echo /iac)"
export GIT_CONFIG_VALUE_0

We set all of these vars once immediately after setting the hooks and then refresh the GIT_CONFIG_VALUE_0 for each iteration of the dirs loop to accommodate AUTODETECT=True.

Internal naming¶

Tool: An executable file in the easy_infra and root user’s PATH which perform IaC actions and has an associated security tool, as described in the easy_infra.yml used when building the image.
Security tool: An executable file in the easy_infra and root user’s PATH which is configured to perform a security scan for an associated “tool” (see above), as configured in the easy_infra.yml file used to build the image.
Package: The name of a package that can be installed to perform a necessary function. It could be a tool, a security tool, or a generic helper such as fluent-bit or envconsul.
Command: A runtime command, following the use of the term by bash (see this documentation). This could be an alias, a package, or some other executable on the user’s PATH.
Alias: An executable file in the easy_infra and root user’s PATH which executes the installed by a package. While aws-cli would be a package, aws would be the associated alias.
Environment: A supported destination that a tool (see above) may deploy into, such as a cloud provider. An environment constitutes a bundle of packages.

Scan-only functions¶

In addition to the Alias and Package functions which are generated, scan_ functions are also created to allow you to run only the security scans (and related hooks) for a given Package or Alias. So, for instance, if you have a Package of terraform, the related scan function would be scan_terraform. Whereas, if you have a Package of ansible which has Aliases of ansible and ansible-playbook, you will get scan functions of scan_ansible and scan_ansible-playbook.

High-Level Design of the image build process¶

When building the easy_infra images, the high level design is that files in the build/ directory are composed together using tasks.py to create multiple final container images for various use cases. Those use cases are primarily based around the use of an IaC “tool” (i.e. terraform or ansible), and an associated set of “security tools” (i.e. checkov or kics) which will run transparently when the IaC tool is used inside of a container. There are also sometimes optional “environment” (i.e. aws or azure) images which add environment-specific helpers or tools, based on the tool that the image focuses on.

There are two general types of files in build/; Dockerfile* and Dockerfrag*.

All Dockerfile* files should be able to be built and tested independently, and are effectively the “install” step of building the easy_infra images. It is possible that an easy_infra Dockerfile may only contain a FROM statement, if we are using a container built and distributed by the upstream project. Dockerfile suffixes MUST also be the same as a given package as outlined in the easy_infra.yml (aliases are not supported), with the single exception of Dockerfile.base (for example, the terraform package’s Dockerfile must be Dockerfile.terraform).

All Dockerfrag* files should not be built and tested independently, as they are solely fragments which depend on the related Dockerfile. For instance, Dockerfrag.terraform is meant to build on top of Dockerfile.terraform. The contents of a Dockerfrag often hinge around running COPY commands to pull files from the Dockerfile. This model allows us to create extremely minimal final images with limited bloat and consideration of extraneous packages or dependencies which are only needed at build time.

In order for a Dockerfile and a Dockerfrag to be “linked” together, they must share the same suffix. For example, Dockerfrag.abc should build on top of Dockerfile.abc, and it is both expected that in Dockerfrag.abc it copies files using COPY --from=abc ..., and that in Dockerfile.abc the FROM statement ends with ... as abc.

Runtime user support¶

By default, easy_infra runs as the easy_infra user and should be fully functional, however we also support the root user due to various file system permission issues that often occur in pipelines when running as non-root users. Where possible, the easy_infra user should be used due to the security risks of running containers as root.

Adding to the project¶

Adding a tool¶

Add the package to easy-infra.yml under packages and include a valid security, version, and version_argument section. Consider other optional configurations as they apply (see easy_infra.yml for more details).
Modify docker-entrypoint.sh to print the tool version if the correct binary exists inside of the container.
Create a Dockerfile.{tool} and Dockerfrag.{tool} in the build/ directory.
You may need to add the tool name or any aliases in .github/etc/dictionary.txt if it is not a standard English word, assuming it is used in documentation.
Create a new folder in docs/ and add documentation regarding the tool. Reference the new docs in the toctree of docs/index.rst in line with the other toctree entries.
Consider developing any specialized hooks, using the hooks framework.
Write tests in tests/test.py by creating a new function named run_{tool} and following the pattern that other run_* functions follow by creating a list of 3-tuple tests, and then using the exec_tests function to perform the tests and return the number of tests that were successfully run, logging the amount and type of tests performed at the end of the function.
Add a folder under tests/ aligned to the tool name, and create a variety of different configuration files that will be referenced by the tests in tests/test.py. Ensure that there are:
- invalid and secure folders containing aligned configuration files, typically under tests/{tool}/general/.
- At least one security_tool/{security_tool} folder under tests/{tool} containing insecure code.
- If you developed hooks which register to the tool, create a tests/{tool}/hooks/ directory, containing a variety of folders that exercise those built-in hooks.
Identify how the latest released version of the tool (either the “package” or tool name under the package) can be retrieved. Ensure that the update function in tasks.py will retrieve the latest version appropriately. You may be able to use some of the existing mechanisms (such as using apt, GitHub repo releases, GitHub repo tags, python package versions, etc.) which are maintained in easy_infra/constants.py and whose update functions exist in easy_infra/utils.py (see the get_latest_release_from_* functions).

Note

If you need any special configuration at build time specific to the combination of a tool and an environment, you can create a Dockerfile.{tool}-{environment} and Dockerfrag.{tool}-{environment}. These are entirely optional.