- Introduction
- How does Regula work?
- Rule library
- Running Regula locally
- Regula rules
- Compliance controls vs. rules
- Interpreting the results
- Running Regula in CI
- Running Regula with Conftest
- Development
Regula is a tool that evaluates Terraform infrastructure-as-code for potential AWS, Azure, and Google Cloud security misconfigurations and compliance violations prior to deployment.
Regula includes a library of rules written in Rego, the policy language used by the Open Policy Agent (opa) project. Regula works with your favorite CI/CD tools such as Jenkins, Circle CI, and AWS CodePipeline; we’ve included a GitHub Actions example so you can get started quickly (see our blog post here). Where relevant, we’ve mapped Regula policies to the CIS AWS, Azure, and GCP Foundations Benchmarks so you can assess your compliance posture. We'll be adding more rules in the coming weeks, sourced from Fugue.
There are two parts to Regula. The first is a shell script that generates a terraform plan in JSON format, ready for consumption by opa.
The second part is a Rego framework that:
- Merges resource info from
planned_values
andconfiguration
in the Terraform plan into a more conveniently accessible format. - Walks through the imported Terraform modules and merges them into a flat format.
- Looks for rules and executes them.
- Creates a report with the results of all rules and a control mapping in the output.
See rules directory. Fugue is currently working on open sourcing more rules from our product to Regula.
Provider | Service | Rule Name | Rule Summary |
---|---|---|---|
AWS | CloudTrail | cloudtrail_log_file_validation | CloudTrail log file validation should be enabled |
AWS | EBS | ebs_volume_encrypted | EBS volume encryption should be enabled |
AWS | IAM | iam_admin_policy | IAM policies should not have full ":" administrative privileges |
AWS | IAM | iam_user_attached_policy | IAM policies should not be attached directly to users |
AWS | KMS | kms_rotate | KMS CMK rotation should be enabled |
AWS | VPC | security_group_ingress_anywhere | VPC security group rules should not permit ingress from '0.0.0.0/0' except to ports 80 and 443 |
AWS | VPC | security_group_ingress_anywhere_rdp | VPC security group rules should not permit ingress from '0.0.0.0/0' to port 3389 (Remote Desktop Protocol) |
AWS | VPC | security_group_ingress_anywhere_ssh | VPC security group rules should not permit ingress from '0.0.0.0/0' to port 22 (SSH) |
AWS | VPC | vpc_flow_log | VPC flow logging should be enabled |
GCP | KMS | kms_cryptokey_rotate | KMS crypto keys should be rotated at least once every 365 days |
GCP | Compute | compute_firewall_no_ingress_22 | VPC firewall rules should not permit ingress from '0.0.0.0/0' to port 22 (SSH) |
GCP | Compute | compute_firewall_no_ingress_3389 | VPC firewall rules should not permit ingress from '0.0.0.0/0' to port 3389 (RDP) |
GCP | Compute | compute_subnet_private_google_access | VPC subnet 'Private Google Access' should be enabled |
GCP | Compute | compute_subnet_flow_log_enabled | VPC subnet flow logging should be enabled |
Azure | Storage Account | storage_account_deny_access | Storage accounts should deny access from all networks by default |
Azure | Storage Account | storage_account_microsoft_services | Storage accounts 'Trusted Microsoft Services' access should be enabled |
Azure | Storage Account | storage_account_secure_transfer | Storage accounts 'Secure transfer required' should be enabled |
Azure | Blob Storage | storage_container_private_access | Storage containers should have access set to 'private' |
Azure | Virtual Network | network_security_group_no_inbound_22 | Network security group rules should not permit ingress from '0.0.0.0/0' to port 22 (SSH) |
network_security_rule_no_inbound_22 | |||
Azure | Virtual Network | network_security_group_no_inbound_3389 | Network security group rules should not permit ingress from '0.0.0.0/0' to port 3389 (RDP) |
network_security_rule_no_inbound_3389 | |||
Azure | SQL Server | sql_server_firewall_no_inbound_all | SQL Server firewall rules should not permit ingress from 0.0.0.0/0 to all ports and protocols |
Install the prerequisites:
Run the following command:
./bin/regula [TERRAFORM_PATH] [REGO_PATHS...]
TERRAFORM_PATH
is the directory where your Terraform configuration files are
located.
REGO_PATHS
are the directories that need to be searched for Rego code. This
should at least include lib/
.
Some examples:
./bin/regula ../my-tf-infra .
: conveniently check../my-tf-infra
against all rules in this main repository../bin/regula ../my-tf-infra lib examples/aws/t2_only.rego
: run Regula using only the specified rule../bin/regula ../my-tf-infra lib ../custom-rules
: run Regula using a directory of custom rules.
It is also possible to set the name of the terraform
executable, which is
useful if you have several versions installed:
env TERRAFORM=terraform-v0.12.18 ./bin/regula ../regula-ci-example/ lib
Note that Regula requires Terraform 0.12+ in order to generate the JSON-formatted plan.
Because Regula uses a bash script to automatically generate a plan, convert it to JSON, and run the Rego validations, Windows users can instead manually run the steps that Regula performs. See those steps here. Alternatively, you can run the script using WSL.
Regula rules are written in standard Rego and use a similar format to Fugue Custom Rules. This means there are (currently) two kinds of rules: simple rules and advanced rules.
Simple rules are useful when the policy applies to a single resource type only, and you want to make simple yes/no decision.
# Rules must always be located right below the `rules` package.
package rules.my_simple_rule
# Simple rules must specify the resource type they will police.
resource_type = "aws_ebs_volume"
# Simple rules must specify `allow` or `deny`. For this example, we use
# an `allow` rule to check that the EBS volume is encrypted.
default allow = false
allow {
input.encrypted == true
}
Advanced rules are harder to write, but more powerful. They allow you to observe different kinds of resource types and decide which specific resources are valid or invalid.
# Rules still must be located in the `rules` package.
package rules.user_attached_policy
# Advanced rules typically use functions from the `fugue` library.
import data.fugue
# We mark an advanced rule by setting `resource_type` to `MULTIPLE`.
resource_type = "MULTIPLE"
# `fugue.resources` is a function that allows querying for resources of a
# specific type. In our case, we are just going to ask for the EBS volumes
# again.
ebs_volumes = fugue.resources("aws_ebs_volume")
# Auxiliary function.
is_encrypted(resource) {
resource.encrypted == true
}
# Regula expects advanced rules to contain a `policy` rule that holds a set
# of _judgements_.
policy[p] {
resource = ebs_volumes[_]
is_encrypted(resource)
p = fugue.allow_resource(resource)
} {
resource = ebs_volumes[_]
not is_encrypted(resource)
p = fugue.deny_resource(resource)
}
The fugue
API consists of four functions:
fugue.resources(resource_type)
returns an object with all resources of the requested type.fugue.allow_resource(resource)
marks a resource as valid.fugue.deny_resource(resource)
marks a resource as invalid.fugue.missing_resource(resource_type)
marks a resource as missing. This is useful if you for example require a log group to be present.
Whereas the rules included in the Regula rules library are generally applicable, we've built rule examples that look at tags, region restrictions, and EC2 instance usage that should be modified to fit user/organization policies.
Provider | Service | Rule Name | Rule Description |
---|---|---|---|
AWS | EC2 | ec2_t2_only | Restricts instances to a whitelist of instance types |
AWS | IAM | iam_password_length | Requires IAM Password Policies with a certain minimum password length |
AWS | Tags | tag_all_resources | Checks whether resources that are taggable have at least one tag with a minimum of 6 characters |
AWS | Regions | useast1_only | Restricts resources to a given AWS region |
What's the difference between controls and rules? A control represents an individual recommendation within a compliance standard, such as "IAM policies should not have full "*:*"
administrative privileges" (CIS AWS Foundations Benchmark 1-22).
In Regula, a rule is a Rego policy that validates whether a cloud resource violates a control (or multiple controls). One example of a rule is iam_admin_policy
, which checks whether an IAM policy in a Terraform file has "*:*"
privileges. If it does not, the resource fails validation.
Controls map to sets of rules, and rules can map to multiple controls. For example, control CIS_1-22
and REGULA_R00002
both map to the rule iam_admin_policy
.
Controls can be specified within the rules: just add a controls
set.
# Rules must always be located right below the `rules` package.
package rules.my_simple_rule
# Simple rules must specify the resource type they will police.
resource_type = "aws_ebs_volume"
# Controls.
controls = {"CIS_1-16"}
# Rule logic
...
Here's a snippet of test results from a Regula report. The output is from an example GitHub Action:
{
"result": [
{
"expressions": [
{
"value": {
"controls": {
"CIS_1-22": {
"rules": [
"iam_admin_policy"
],
"valid": false
}
},
"rules": {
"iam_admin_policy": {
"resources": {
"aws_iam_policy.basically_allow_all": {
"id": "aws_iam_policy.basically_allow_all",
"message": "invalid",
"type": "aws_iam_policy",
"valid": false
},
"aws_iam_policy.basically_deny_all": {
"id": "aws_iam_policy.basically_deny_all",
"message": "",
"type": "aws_iam_policy",
"valid": true
}
},
"valid": false
}
},
"summary": {
"controls_failed": 2,
"controls_passed": 12,
"rules_failed": 2,
"rules_passed": 8,
"valid": false
}
},
"text": "data.fugue.regula.report",
"location": {
"row": 1,
"col": 1
}
}
]
}
]
}
These are the important bits:
- Summary
- Controls
- Rules
The summary
block contains a breakdown of the compliance state of your Terraform files. In the output above, the Terraform violated 2 rules and 2 controls, so the test as a whole failed.
Regula shows you compliance results for both controls and rules, in addition to which specific resources failed. Above, in the controls
block, you can see that the Terraform in the example is noncompliant with CIS_1-22
, and the mapped rules that failed are listed underneath (in this case, iam_admin_policy
).
In the rules
block further down from controls
, each rule lists the resources that failed. Above, you'll see that the resource aws_iam_policy.basically_allow_all
was the one that failed the mapped rule -- as noted by "valid": false
. In contrast, aws_iam_policy.basically_deny_all
passed.
You can see the full example report in this GitHub Action log. For a detailed explanation of the report, see the regula-ci-example README.
Regula is designed to be easy to run in CI. We provide a GitHub Action that can be easily added to your repository:
https://github.com/fugue/regula-action
Setting up Regula with different CI/CD solutions such as Jenkins, CodePipeline, CircleCI, TravisCI, and others would follow a similar pattern. This repository contains an example:
https://github.com/fugue/regula-ci-example
Conftest is a test runner for configuration files that uses Rego for policy-as-code. Conftest supports Terraform; but policies need to be written directly against the plan file which is often inconvenient and tricky.
Since Regula is just a Rego library; it works works seamlessly with Conftest. This way you get the advantages of both projects, in particular:
- Easy CI integration and policy retrieval from Conftest
- Terraform plan parsing & the rule set from Regula
To use Regula with Conftest:
-
Generate a
plan.json
using the following terraform commands:terraform init terraform plan -refresh=false -out=plan.tfplan terraform show -json plan.tfplan >plan.json
-
Now, we'll pull the conftest support for Regula and the Regula library in.
conftest pull -p policy/ github.com/fugue/regula/conftest conftest pull -p policy/regula/lib github.com/fugue/regula/lib
If we want to use the rules that come with regula, we can use:
conftest pull -p policy/regula/rules github.com/fugue/regula/rules
And of course you can pull in your own Regula rules as well.
-
As this point, it's simply a matter of running conftest!
conftest test plan.json
bin/
: the main Regula script that callsterraform
&opa
.lib/
: the OPA library code to evaluate rules and mangle input.rules/
: a collection of rules. We may split this up further as the number of rules increases.examples/
: a collection of example rules that you can use as inspiration for your own rules.scripts/
: scripts for development; currently only a script to generate test input.tests/
:tests/lib
: internal tests for the library.tests/rules/
: tests for the various rules.tests/rules/inputs
: terraform files that can be used to generate Rego files.tests/examples/
: tests for the example rules.tests/examples/inputs
: input files for the example rules.
If you would like to add a rule, we recommend starting with a test.
Put your terraform code in a file in tests/rules/<provider>/inputs
; for example
tests/rules/aws/inputs/kms_rotate_infra.tf.
From this, you can generate a mock input by running:
bash scripts/generate-test-inputs.sh
The mock input will then be placed in a .rego
file with the same name,
in our case tests/rules/aws/inputs/kms_rotate_infra.rego.
Next, add the actual tests to a Rego file with the same name (appended with _test
instead of _infra
),
but outside of the inputs/
subdirectory. Using this example, that would be tests/rules/aws/kms_rotate_test.rego.
Once you have generated the mock input, it is easy to debug a rule with
fregot. Fire up fregot
with the right directories and set a breakpoint on
the rule you are trying to debug:
$ fregot repl lib rules tests
F u g u e R E G O T o o l k i t
fregot v0.7.2 repl - use :help for usage info
repl% :break data.rules.t2_only.allow
Now, we can just evaluate the entire report with the mock input. If your rule is triggered, that will drop you into a debug prompt:
repl% data.fugue.regula.report with input as data.tests.rules.t2_only.mock_input
19| valid_instance_types[input.instance_type]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
From here, you can evaluate anything in context; such as input
to look at the
resource, or any other auxiliary rules such as valid_instance_types
in this
example.
In some cases (such as development and testing), you may want to manually reproduce the steps that Regula performs automatically. If that is something you want to step through, this section is for you.
We first need to obtain a JSON-formatted terraform plan. In order to do get that, you can use:
terraform init
terraform plan -refresh=false -out=plan.tfplan
terraform show -json plan.tfplan >input.json
This gives you input.json
. Now you can test this input against the rules by
evaluating data.fugue.regula.report
with OPA. In order to do that, point OPA
to the input file, and the regula project directory.
opa eval -d /path/to/regula --input input.json 'data.fugue.regula.report'
Or using fregot
:
fregot eval --input input.json 'data.fugue.regula.report' . | jq
If all goes well, you should now see the results for each rule.
To locally produce a Regula report on Windows, use the following steps:
-
Generate a JSON-based terraform plan:
.\terraform.exe init .\terraform.exe plan -refresh=false -out=infra .\terraform.exe show -json infra >infra.json
-
Run OPA against this input file:
.\opa_windows_amd64.exe eval -i .\infra.json -d .\regula\lib\ -d .\regula\rules\ 'data.fugue.regula.report'