Creating Queries

Create a new Query

The queries are written in Rego and our internal parser transforms every IaC file that supports into a universal JSON format. This way anyone can start working on a query by picking up a small sample of the vulnerability that the query should target, and convert this sample, which can be a .tf or .yaml file, to our JSON structure JSON. To convert the sample you can run the following command:

go run ./cmd/console/main.go scan -p "pathToTestData" -d "pathToGenerateJson"

So for example, if we wanted to transform a .tf file in ./code/test we could type:

go run ./cmd/console/main.go scan -p  "./src/test" -d "src/test/input.json"

Example of input.json

{
    "document": [
        {
            "resource": {
                "aws_cloudtrail": {
                    "positive1": {
                        "name": "npositive_1",
                        "s3_bucket_name": "bucketlog_1"
                    }
                }
            },
            "id": "02926636-f2c1-46c3-93cc-c7dc2a79791f",
            "file": "/assets/queries/terraform/aws/cloudtrail_multi_region_disabled/test/positive1.tf"
        },
        {
            "resource": {
                "aws_cloudtrail": {
                    "positive2": {
                        "name": "npositive_2",
                        "s3_bucket_name": "bucketlog_2",
                        "is_multi_region_trail": false
                    }
                }
            },
            "id": "4b27da84-4d38-4422-b2b5-fa85029dad2a",
            "file": "assets/queries/terraform/aws/cloudtrail_multi_region_disabled/test/positive2.tf"
        }
    ]
}

After having the .json that will be our Rego input, we can begin to write queries. To test and debug there are two ways:

• Using Rego playground
• Install Open Policy Agent extension in VS Code and create a simple folder with a .rego file for the query and a input.json for the sample to test against

Query Development Tutorial

In the first instance, take a look at the query composition: - query.rego: Includes the policy and defines the result. The policy builds the pattern that breaks the security of the infrastructure code, which the query is looking for. The result defines the specific data used to present the vulnerability in the infrastructure code. - metadata.json: Each query has a metadata.json companion file with all the relevant information about the vulnerability, including the severity, category and its description; - test: Folder that contains at least one negative and positive case and a JSON file with data about the expected results.

- <technology>
    |- <provider>
    |   |- <queryfolder>
    |   |   |- test
    |   |   |   |- positive1<.ext>
    |   |   |   |- positive2<.ext>
    |   |   |   |- negative1<.ext>
    |   |   |   |- negative2<.ext>
    |   |   |   |- positive_expected_result.json
    |   |   |- metadata.json
    |   |   |- query.rego

Now, focus on the content of each file:

👨‍💻 REGO File

As a first step, it is important to be familiar with the libraries available (check them in assets/libraries) and the JSON structure (Rego input). Also, we need to study all the possible cases related to the vulnerability we want to verify before starting the implementation.

For example, if we want to verify if the AWS CloudTrail has MultiRegion disabled in a Terraform sample, we need to focus on the attribute is_multi_region_trail of the resource aws_cloudtrail. Since this attribute is optional and false by default, we have two cases: (1) is_multi_region_trail is undefined and (2) is_multi_region_trail is set to false. Observe the following implementation as an example and check the Guidelines below.

:rotating_light: Make sure you use package Cx. If you give another name, the query will not load. :rotating_light:

package Cx

CxPolicy[result] {
    cloudtrail := input.document[i].resource.aws_cloudtrail[name]
    object.get(cloudtrail, "is_multi_region_trail", "undefined") == "undefined"

    result := {
        "documentId": input.document[i].id,
        "searchKey": sprintf("aws_cloudtrail[%s]", [name]),
        "issueType": "MissingAttribute",
        "keyExpectedValue": "CloudTrail Multi Region should be defined",
        "keyActualValue": "CloudTrail Multi Region is undefined",
    }
}

CxPolicy[result] {
    cloudtrail := input.document[i].resource.aws_cloudtrail[name]
    cloudtrail.is_multi_region_trail == false

    result := {
        "documentId": input.document[i].id,
        "searchKey": sprintf("aws_cloudtrail[%s].is_multi_region_trail", [name]),
        "issueType": "IncorrectValue",
        "keyExpectedValue": "CloudTrail Multi Region should be set to true",
        "keyActualValue": "CloudTrail Multi Region is set to false",
    }
}

To test the query in the Rego playground, perform the following steps: 1. Enable Coverage (highlights which statements were evaluated); 2. In the input, paste the payload (explained above); 3. In the playground, paste and/or write the policies. Check if the statements are painted green; 4. Click on Evaluate; 5. In the output, check if the results are as expected.

👨‍💻 Metadata File

Observe the following metadata.json example and check the Guidelines below for more detailed information.

{
  "id": "8173d5eb-96b5-4aa6-a71b-ecfa153c123d",
  "queryName": "CloudTrail Multi Region Disabled",
  "severity": "MEDIUM",
  "category": "Observability",
  "descriptionText": "CloudTrail should have 'is_multi_region_trail' and 'include_global_service_events' enabled",
  "descriptionUrl": "https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/cloudtrail#is_multi_region_trail",
  "platform": "Terraform",
  "descriptionID": "feb82a62",
  "cloudProvider": "aws"
}

👨‍💻 Data File

This file contains a map, with string keys, which will have default values for keys that can be overwritten as described on allowing users to overwrite query data section and using custom input data section of Running KICS

👨‍💻 Test Folder

Keep in mind that all the positive and negative files should contain only one breaking point case. This way, the results are more clear. As a best practice, the test folder should contain all the extensions available by the platform.

Each positive case should present a breaking point of the vulnerability. Continuing with the example, we should display two positive files: one without the is_multi_region_trail defined (positive1.tf) and another with the is_multi_region_trail set to false (positive2.tf).

positive1.tf

resource "aws_cloudtrail" "positive1" {
  name                          = "npositive_1"
  s3_bucket_name                = "bucketlog_1"
}

positive2.tf

resource "aws_cloudtrail" "positive2" {
  name                          = "npositive_2"
  s3_bucket_name                = "bucketlog_2"
  is_multi_region_trail         = false
}

Each negative case should present the remediation/best practice (a sample with the is_multi_region_trail set to true).

negative1.tf

resource "aws_cloudtrail" "negative1" {
  name                          = "negative"
  s3_bucket_name                = "bucketlog"
  is_multi_region_trail         = true
}

The positive expected result should present where the positive(s) file(s) break(s) the vulnerability (in line 2 (positive1.tf) and line 4 (positive2.tf)).

[
  {
    "queryName": "CloudTrail Multi Region Disabled",
    "severity": "MEDIUM",
    "line": 2,
    "fileName": "positive1.tf"
  },
  {
    "queryName": "CloudTrail Multi Region Disabled",
    "severity": "MEDIUM",
    "line": 4,
    "fileName": "positive2.tf"
  }
]

Testing

For a query to be considered complete, it must be compliant with at least one positive and one negative test case. To run the unit tests you can run this command:

make test

Check if the new test was added correctly and if all tests are passing locally. If succeeds, a Pull Request can now be created.

Guidelines

Filling metadata.json:

• id should be filled with a UUID. You can use the built-in command to generate this:

go run ./cmd/console/main.go generate-id

• queryName describes the name of the vulnerability
• severity can be filled with HIGH, MEDIUM, LOW or INFO
• category pick one of the following:
  • Access Control
  • Availability
  • Backup
  • Best Practices
  • Build Process
  • Encryption
  • Insecure Configurations
  • Insecure Defaults
  • Networking and Firewall
  • Observability
  • Resource Management
  • Secret Management
  • Supply-Chain
• descriptionText should explain with detail the vulnerability and if possible provide a way to remediate
• descriptionUrl points to the official documentation about the resource being targeted
• platform query target platform (e.g. Terraform, Kubernetes, etc.)
• descriptionID should be filled with the first eight characters of the go run ./cmd/console/main.go generate-id output
• cloudProvider should specify the target cloud provider, when necessary (e.g. AWS, AZURE, GCP, etc.)
• aggregation [optional] should be used when more than one query is implemented in the same query.rego file. Indicates how many queries are implemented
• override [optional] should only be used when a metadata.json is shared between queries from different platforms or different specification versions like for example OpenAPI 2.0 (Swagger) and OpenAPI 3.0. This field defines an object that each field is mapped to a given overrideKey that should be provided from the query execution result (covered in the next section), if an overrideKey is provided, this will generate a new query that inherits the root level metadata values and only rewrites the fields defined inside this object.

If the query.rego file implements more than one query, the metadata.json should indicate how many are implemented (through aggregation). That can be necessary due to two cases: 1. It implements more than one query in the same query.rego for the same platform

{
  "id": "0ac9abbc-6d7a-41cf-af23-2e57ddb3dbfc",
  "queryName": "Sensitive Port Is Exposed To Entire Network",
  "severity": "HIGH",
  "category": "Networking and Firewall",
  "descriptionText": "A sensitive port, such as port 23 or port 110, is open for the whole network in either TCP or UDP protocol",
  "descriptionUrl": "https://docs.ansible.com/ansible/latest/collections/azure/azcollection/azure_rm_securitygroup_module.html#parameter-rules",
  "platform": "Ansible",
  "descriptionID": "33745204",
  "cloudProvider": "azure",
  "aggregation": 62
}

1. It implements the same query for different platforms in the same query.rego, the metadata below defines the query metadata for both OpenAPI 2.0 and 3.0 in the same file:

{
  "id": "332cf2ad-380d-4b90-b436-46f8e635cf38",
  "queryName": "Invalid Contact URL (v3)",
  "severity": "INFO",
  "category": "Best Practices",
  "descriptionText": "Contact Object URL should be a valid URL",
  "descriptionUrl": "https://swagger.io/specification/#contact-object",
  "platform": "OpenAPI",
  "override": {
    "2.0": {
      "id": "c7000383-16d0-4509-8cd3-585e5ea2e2f2",
      "queryName": "Invalid Contact URL (v2)",
      "descriptionUrl": "https://swagger.io/specification/v2/#contactObject"
    }
  },
  "aggregation": 2,
  "descriptionID": "f3097573"
}

Filling query.rego:

• documentId id of the sample where the vulnerability occurs

• searchKey uses Levenshtein distance to go through the original document. It should “include” as much information as possible so that the result is as accurate as possible.

  Note the following special chars: - '=' -> value - '.' -> break line - '{{ }}' -> ignore special chars - '[ ]' -> same line

  As an example, take a look at the following sample:

  

  If we want to point to the field 'Name' set as 'My.bucket' of 'tags', the searchKey should be set to resource[positive].tags.Name={{My.bucket}}

• issueType pick one of the following:

  • IncorrectValue
  • MissingAttribute
  • RedundantAttribute
• keyExpectedValue should explain the expected value
• keyActualValue should explain the actual value detected
• overrideKey [optional] should be used when the query can be applied to more than one platform (for now, it is used for both OpenAPI 3.0 and Swagger)

For example, the query Invalid Contact URL can be implemented in both OpenAPI 3.0 and Swagger since both versions share the same properties:

package Cx

import data.generic.openapi as openapi_lib

CxPolicy[result] {
    doc := input.document[i]
    version := openapi_lib.check_openapi(doc)
    version != "undefined"

    not openapi_lib.is_valid_url(doc.info.contact.url)

    result := {
        "documentId": doc.id,
        "searchKey": "info.contact.url",
        "issueType": "IncorrectValue",
        "keyExpectedValue": "info.contact.url has a valid URL",
        "keyActualValue": "info.contact.url has an invalid URL",
        "overrideKey": version,
    }
}

• searchValue [optional] should be used when the query returns more than one result for the same line
• searchLine [optional] path where the breaking point occurs in the sample

For example, the query Sensitive Port Is Exposed To Entire Network can return more than one result in the same line (the ingress covers a range of ports). To avoid it, the searchValue should be used.

package Cx

import data.generic.terraform as terraLib
import data.generic.common as commonLib

CxPolicy[result] {
    resource := input.document[i].resource.aws_security_group[name]

    portContent := commonLib.tcpPortsMap[port]
    portNumber = port
    portName = portContent
    protocol := terraLib.getProtocolList(resource.ingress.protocol)[_]

    endswith(resource.ingress.cidr_blocks[_], "/0")
    terraLib.containsPort(resource.ingress, portNumber)
    isTCPorUDP(protocol)

    result := {
        "documentId": input.document[i].id,
        "searchKey": sprintf("aws_security_group[%s].ingress", [name]),
        "searchValue": sprintf("%s,%d", [protocol, portNumber]),
        "issueType": "IncorrectValue",
        "keyExpectedValue": sprintf("%s (%s:%d) should not be allowed", [portName, protocol, portNumber]),
        "keyActualValue": sprintf("%s (%s:%d) is allowed", [portName, protocol, portNumber]),
    }
}

isTCPorUDP("TCP") = true
isTCPorUDP("UDP") = true

Search Line

To improve the KICS line detection mechanism, searchLine was introduced.

SearchLine uses json path to get the correct line information from the payload (which can be seen with the flag payload-lines).

Original Content:

father:
  name: son

Payload With Line Information:

{
    "_kics_lines": {
        "_kics__default": {
            "_kics_line": 0
        },
        "_kics_father": {
            "_kics_line": 2
        }
    },
    "father": {
        "_kics_lines": {
            "_kics__default": {
                "_kics_line": 2
            },
            "_kics_name": {
                "_kics_line": 3
            }
        },
        "name": "son"
    }
},

Usage:

import data.generic.common as commonLib

result := {
        "documentId": doc.id,
        "searchKey": "father.son",
        "issueType": "IncorrectValue",
        "searchLine": commonLib.build_search_line(["father", "son"], []),
    }

Function build_search_line(path, obj):

The function build_search_line is a helper that builds the searchLine for the engine to create and use the json path. It take two arguments:

• path: An array containing the path elements (keys and indexes) to the desired key line.. (ex: ["father", "son"]; ["father", 1, "son"]; ["father", "son", 0])

• obj: For queries that use the function walk in rego, where the caller is given a path that should be placed in the path argument of build_search_line, the remaining path not present should be placed in obj. Obj can also be used in other queries that don't make use of the function walk, otherwise it should be passed empty. (ex: ["son"],["son", 0])

Examples:

    build_search_line(["father"], ["son"])

    build_search_line(["father", "son"], [])

    build_search_line(["father", "son"], ["grandson", 1])

    [path, value] := walk(x)
    son := value.son
    son == false
    build_search_line(path, ["son"])

Allowing users to overwrite query data

Starting on v1.3.5, KICS started to support custom data overwriting on queries. This can be useful if users want to provide their own dataset or if users have different datasets for multiple environments. This can be supported easily following some steps:

1. Create a data.json file on the same level as query.rego;
2. Define ALL keys that can be overwritten with their default value;
3. On query.rego file, use data.<key_on_data_json_file> to access the value of this key;

With these simple steps, users will be able to overwrite the keys they want, elsewhere will use the default value.

Query Dependencies

If you want to use the functions defined in your own library, you should use the flag -b to indicate the directory where the libraries are placed. The functions need to be grouped by platform and the library name should follow the following format: <platform>.rego. It doesn't matter your directory structure. In other words, for example, if you want to indicate a directory that contains a library for your terraform queries, you should group your functions (used in your terraform queries) in a file named terraform.rego wherever you want.