Merge branch 'checks-contrib-docs' into main

docs/community/contribute/checks/overview.md

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+# Contribute Rego Checks
+
+The following guide provides an overview of contributing checks to the default checks in Trivy. 
+
+All of the checks in Trivy can be found in the [trivy-policies](https://github.com/aquasecurity/trivy-policies/tree/main) repository on GitHub. Before you begin writing a check, ensure:
+
+1. The check does not already exist as part of the default checks in the [trivy-policies](https://github.com/aquasecurity/trivy-policies/tree/main) repository.
+2. The pull requests in the [trivy-policies](https://github.com/aquasecurity/trivy-policies/pulls) repository to see  whether someone else is already contributing the check that you wanted to add. 
+3. The [issues in Trivy](https://github.com/aquasecurity/trivy/issues) to see whether any specific checks are missing in Trivy that you can contribute.
+
+If anything is unclear, please [start a discussion](https://github.com/aquasecurity/trivy/discussions/new) and we'll do our best to help.
+
+## Check structure
+
+Checks are written in Rego and follow a particular structure in Trivy. Below is an example check for AWS:
+
+```rego
+# METADATA
+# title: "RDS IAM Database Authentication Disabled"
+# description: "Ensure IAM Database Authentication is enabled for RDS database instances to manage database access"
+# scope: package
+# schemas:
+# - input: schema["aws"]
+# related_resources:
+# - https://docs.aws.amazon.com/neptune/latest/userguide/iam-auth.html
+# custom:
+#   id: AVD-AWS-0176
+#   avd_id: AVD-AWS-0176
+#   provider: aws
+#   service: rds
+#   severity: MEDIUM
+#   short_code: enable-iam-auth
+#   recommended_action: "Modify the PostgreSQL and MySQL type RDS instances to enable IAM database authentication."
+#   input:
+#     selector:
+#     - type: cloud
+#       subtypes:
+#         - service: rds
+#           provider: aws
+
+package builtin.aws.rds.aws0176
+
+deny[res] {
+	instance := input.aws.rds.instances[_]
+	instance.engine.value == ["postgres", "mysql"][_]
+	not instance.iamauthenabled.value
+	res := result.new("Instance does not have IAM Authentication enabled", instance.iamauthenabled)
+}
+```
+
+## Verify the provider and service exists
+
+Every check for a cloud service references a cloud provider. The list of providers are found in the [Trivy](https://github.com/aquasecurity/trivy/tree/main/pkg/iac/providers) repository. 
+
+Before writing a new check for a cloud provider, you need to verify if the cloud provider or resource type that your check targets is supported by Trivy. If it's not, you'll need to add support for it. Additionally, if the provider that you want to target exists, you need to check whether the service your policy will target is supported. As a reference you can take a look at the AWS provider [here](https://github.com/aquasecurity/trivy/blob/main/pkg/iac/providers/aws/aws.go).
+
+???+ note
+    New Kubernetes and Dockerfile checks do not require any additional provider definitions. You can find an example of a Dockerfile check [here](https://github.com/aquasecurity/trivy-policies/blob/main/checks/docker/add_instead_of_copy.rego) and a Kubernetes check [here](https://github.com/aquasecurity/trivy-policies/blob/main/checks/kubernetes/general/CPU_not_limited.rego).
+
+Before writing a new check, you need to verify if the provider your check targets is supported by Trivy. If the provider that you want to target exists, you need to check whether the service your policy will target is supported. If the service is not support, please refer to the documentation on adding support for a new service in an existing provider.
+
+### Add Support for a New Service in an existing Provider
+
+[Please reference the documentation on adding Support for a New Service](./service-support.md).
+
+This guide also showcases how to add new properties for an existing Service.
+
+## Create a new .rego file
+
+The following directory in the trivy-policies repository contains all of our custom checks. Depending on what type of check you want to create, you will need to nest a new `.rego` file in either of the [subdirectories](https://github.com/aquasecurity/trivy-policies/tree/main/checks):
+
+* cloud: All checks related to cloud providers and their services
+* docker: Docker specific checks
+* kubernetes: Kubernetes specific checks
+
+## Check Package name
+
+Have a look at the existing package names in the [built in checks](https://github.com/aquasecurity/trivy-policies/tree/main/checks). 
+
+The package name should be in the format `builtin.PROVIDER.SERVICE.ID`, e.g. `builtin.aws.rds.aws0176`.
+
+## Generating an ID
+
+Every check has a custom ID that is referenced throughout the metadata of the check to uniquely identify the check. If you plan to contribue your check back into the [trivy-policies](https://github.com/aquasecurity/trivy-policies) repository, it will require a valid ID. 
+
+Running `make id` in the root of the trivy-policies repository will provide you with the next available _ID_ for your rule. 
+
+## Check Schemas
+
+Rego Checks for Trivy can utilise Schemas to map the input to specific objects. The schemas available are listed [here.](https://github.com/aquasecurity/trivy/tree/main/pkg/iac/rego/schemas). 
+
+More information on using the builtin schemas is provided in the [main documentation.](../../../docs/scanner/misconfiguration/custom/schema.md)
+
+## Check Metadata
+
+The metadata is the top section that starts with `# METADATA`, and has to be placed on top of the check. You can copy and paste from another check as a starting point. This format is effectively _yaml_ within a Rego comment, and is [defined as part of Rego itself](https://www.openpolicyagent.org/docs/latest/policy-language/#metadata).
+
+For detailed information on each component of the Check Metadata, please refer to the [main documentation.](../../../docs/scanner/misconfiguration/custom/index.md)
+
+Note that while the Metadata is optional in your own custom checks for Trivy, if you are contributing your check to the Trivy builtin checks, the Metadata section will be required.
+
+
+## Writing Rego Rules
+
+Rules are defined using _OPA Rego_. You can find a number of examples in the `checks` directory ([Link](https://github.com/aquasecurity/trivy-policies/tree/main/checks)). The [OPA documentation](https://www.openpolicyagent.org/docs/latest/policy-language/) is a great place to start learning Rego. You can also check out the [Rego Playground](https://play.openpolicyagent.org/) to experiment with Rego, and [join the OPA Slack](https://slack.openpolicyagent.org/).
+
+
+```rego
+deny[res] {
+	instance := input.aws.rds.instances[_]
+	instance.engine.value == ["postgres", "mysql"][_]
+	not instance.iamauthenabled.value
+	res := result.new("Instance does not have IAM Authentication enabled", instance.iamauthenabled)
+}
+```
+
+The rule should return a result, which can be created using `result.new`. This function does not need to be imported, it is defined internally and provided at runtime. The first argument is the message to display and the second argument is the resource that the issue was detected on.
+
+It is possible to pass any rego variable that references a field of the input document.
+
+## Generate docs
+
+Finally, you'll want to generate documentation for your newly added rule. Please run `make docs` in the [trivy-policies](https://github.com/aquasecurity/trivy-policies) directory to generate the documentation for your new policy and submit a PR for us to take a look at.
+
+## Adding Tests
+
+All Rego checks need to have tests. There are many examples of these in the `checks` directory for each check ([Link](https://github.com/aquasecurity/trivy-policies/tree/main/checks)). More information on how to write tests for Rego checks is provided in the [custom misconfiguration](../../../docs/scanner/misconfiguration/custom/testing.md) section of the docs.
+
+## Example PR
+
+You can see a full example PR for a new rule being added here: [https://github.com/aquasecurity/defsec/pull/1000](https://github.com/aquasecurity/defsec/pull/1000).

docs/community/contribute/checks/service-support.md

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+# Add Service Support
+
+A service refers to a service by a cloud provider. This section details how to add a new service to an existing provider. All contributions need to be made to the [trivy repository](https://github.com/aquasecurity/trivy/).
+
+## Prerequisites
+
+Before you begin, verify that the [provider](https://github.com/aquasecurity/trivy/tree/main/pkg/iac/providers) does not already have the service that you plan to add.
+
+## Adding a new service to an existing provider
+
+Adding a new service involves two steps. The service will need a data structure to store information about the required resources that will be scanned. Additionally, the service will require one or more adapters to convert the scan targetes as input(s) into the aforementioned data structure.
+
+### Create a new file in the provider directory
+
+In this example, we are adding the CodeBuild service to the AWS provider.
+
+First, create a new directory and file for your new service under the provider directory: e.g. [aws/codebuild/codebuild.go](https://github.com/aquasecurity/trivy/blob/main/pkg/iac/providers/aws/codebuild/codebuild.go)
+
+The CodeBuild service will require a structure `struct` to hold the information on the input that is scanned. The input is the CodeBuild resource that a user configured and wants to scan for misconfiguration.
+
+```
+type CodeBuild struct {
+	Projects []Project
+}
+```
+
+The CodeBuild service manages `Project` resources. The `Project` struct has been added to hold information about each Project resources; `Project` Resources in turn manage `ArtifactSettings`:
+
+```
+type Project struct {
+	Metadata                  iacTypes.Metadata
+	ArtifactSettings          ArtifactSettings
+	SecondaryArtifactSettings []ArtifactSettings
+}
+
+type ArtifactSettings struct {
+	Metadata          iacTypes.Metadata
+	EncryptionEnabled iacTypes.BoolValue
+}
+```
+
+The `iacTypes.Metadata` struct is embedded in all of the Trivy types and provides a common set of metadata for all resources. This includes the file and line number where the resource was defined and the name of the resource.
+
+A resource in this example `Project` can have a name and can optionally be encrypted. Instead of using raw string and bool types respectively, we use the trivy types `iacTypes.Metadata` and `iacTypes.BoolValue`. These types wrap the raw values and provide additional metadata about the value. For instance, whether it was set by the user and the file and line number where the resource was defined. 
+
+Have a look at the other providers and services in the [`iac/providers`](https://github.com/aquasecurity/trivy/tree/main/pkg/iac/providers) directory in Trivy.
+
+Next you'll need to add a reference to your new service struct in the [provider struct](https://github.com/aquasecurity/trivy/blob/main/pkg/iac/providers/aws/aws.go) at `pkg/iac/providers/aws/aws.go`:
+
+```
+type AWS struct {
+	...
+	CodeBuild      codebuild.CodeBuild
+    ...
+}
+```
+
+### Update Adapters
+
+Now you'll need to update all of the [adapters](https://github.com/aquasecurity/trivy/tree/main/pkg/iac/adapters) which populate the struct of the provider that you have been using. Following the example above, if you want to add support for CodeBuild in Terraform, you'll need to update the Terraform AWS adatper as shown here: [`trivy/pkg/iac/adapters/terraform/aws/codebuild/adapt.go`](https://github.com/aquasecurity/trivy/blob/main/pkg/iac/adapters/terraform/aws/codebuild/adapt.go).
+
+Another example for updating the adapters is provided in the [following PR.](https://github.com/aquasecurity/defsec/pull/1000/files) Additionally, please refer to the respective Terraform documentation on the provider to which you are adding the service. For instance, the Terraform documentation for AWS CodeBuild is provided [here.](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/codebuild_project)
+
+
+## Create a new Schema for your provider
+
+Once the new service has been added to the provider, you need to create the schema for the service as part of the provider schema. 
+
+This process has been automated with mage commands. In the Trivy root directory run `mage schema:generate` to generate the schema for your new service and `mage schema:verify`.

docs/docs/scanner/misconfiguration/custom/contribute-checks.md

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+## Contribute Rego Checks
+
+The contributing section provides detailed information on
+
+* how to contribute custom checks to the [trivy-policies repository](../../../../community/contribute/checks/overview.md/)
+* add [new services](../../../../community/contribute/checks/service-support.md) to existing cloud providers
+* add [new fields](../../../../community/contribute/checks/service-support.md) to an existing Service
+
+This way, they become accessible as default [policies.](https://github.com/aquasecurity/trivy-policies)