Artifact policy checks

Azure DevOps Services

Artifact policies are enforced before deploying to critical environments such as production. These policies are evaluated against all the deployable artifacts in the given pipeline run and block the deployment if the artifacts don't comply. Adding a check to evaluate Artifact requires the custom policy to be configured. This guide describes how custom policies can be created.

Lưu ý

Currently, the supported artifact types are for container images and Kubernetes environments

Prerequisites

Use Rego for defining policy that is easy to read and write.

Familiarize yourself with Rego query language. Basics will do.

To support structured document models like JSON, Rego extends Datalog. Rego queries are assertions on data stored in OPA. These queries can be used to define policies that enumerate instances of data that violate the expected state of the system.

Creating custom policies

Below are the sample policies shared. Based on your requirements, you can build your own set of policies.

Check specific project/pipeline

This policy checks if the images are built by Azure Pipelines and Pipeline-foo. For this to work, the pipeline definition should override the name field to something like: AzureDevOps_$(BuildDefinitionName)_$(Date:yyyyMMdd)$(Rev:.r). See more about naming pipeline runs here.

allowedBuilder := "AzureDevOps_pipeline-foo"

checkBuilder[errors] {
    trace("Check if images are built by Azure Pipelines")
    resourceUri := values[index].build.resourceUri    
    image := fetchImage(resourceUri)
    builder := values[index].build.build.provenance.builderVersion
    trace(sprintf("%s: builder", [builder]))
    not startswith(builder, "allowedBuilder")
    errors := sprintf("%s: image not built by Azure Pipeline [%s]", [image,builder])
}

fetchRegistry(uri) = reg {
    out := regex.find_n("//.*/", uri, 1)
    reg = trim(out[0], "/")
}

fetchImage(uri) = img {
    out := regex.find_n("/.*@", uri, 1)
    img := trim(out[0], "/@")
}

Check allowed registries

This policy checks if the images are from allowed registries only.

allowlist = {
 "gcr.io/myrepo",
 "raireg1.azurecr.io"
}

checkregistries[errors] {
    trace(sprintf("Allowed registries: %s", [concat(", ", allowlist)]))
    resourceUri := values[index].image.resourceUri
    registry := fetchRegistry(resourceUri)
    image := fetchImage(resourceUri)
    not allowlist[registry]
    errors := sprintf("%s: source registry not permitted", [image]) 
}

fetchRegistry(uri) = reg {
    out := regex.find_n("//.*/", uri, 1)
    reg = trim(out[0], "/")
}

fetchImage(uri) = img {
    out := regex.find_n("/.*@", uri, 1)
    img := trim(out[0], "/@")
}

Check forbidden ports

This policy checks for any forbidden ports exposed in the container image.

forbiddenPorts = {
    "80",
    "22"
}

checkExposedPorts[errors] {
    trace(sprintf("Checking for forbidden exposed ports: %s", [concat(", ", forbiddenPorts)]))
    layerInfos := values[index].image.image.layerInfo
    layerInfos[x].directive == "EXPOSE"
    resourceUri := values[index].image.resourceUri
    image := fetchImage(resourceUri)
    ports := layerInfos[x].arguments
    trace(sprintf("exposed ports: %s", [ports]))
    forbiddenPorts[ports]
    errors := sprintf("%s: image exposes forbidden port %s", [image,ports])
}

fetchRegistry(uri) = reg {
    out := regex.find_n("//.*/", uri, 1)
    reg = trim(out[0], "/")
}

fetchImage(uri) = img {
    out := regex.find_n("/.*@", uri, 1)
    img := trim(out[0], "/@")
}

Check prior deployments

This policy checks if the image has been pre-deployed to one/more of the environments before being deployed to specific environment/resources with Check configured.

predeployedEnvironments = {
    "env/resource1",
    "env2/resource3"
}

checkDeployedEnvironments[errors] {
    trace(sprintf("Checking if the image has been pre-deployed to one of: [%s]", [concat(", ", predeployedEnvironments)]))
    deployments := values[index].deployment
    deployedAddress := deployments[i].deployment.address
    trace(sprintf("deployed to : %s",[deployedAddress]))
    resourceUri := deployments[i].resourceUri
    image := fetchImage(resourceUri)
    not predeployedEnvironments[deployedAddress]
    trace(sprintf("%s: fails pre-deployed environment condition. found %s", [image,deployedAddress]))
    errors := sprintf("image %s fails pre-deployed environment condition. found %s", [image,deployedAddress])
}

fetchRegistry(uri) = reg {
    out := regex.find_n("//.*/", uri, 1)
    reg = trim(out[0], "/")
}

fetchImage(uri) = img {
    out := regex.find_n("/.*@", uri, 1)
    img := trim(out[0], "/@")
}