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Network Config Analyzer (NCA)

What is NCA?

NCA is a tool for analyzing Network Policies and other connectivity-configuration resources. It takes such resources as input, in addition to a list of relevant endpoints, and provides answers to queries such as:

• What is my current connectivity posture?
• How is my connectivity posture changing?
• Is specific traffic allowed/denied?
• What are the endpoints that are not covered by any policy?
• Are my policies implemented efficiently?

Installation (requires Python 3.9 or above)

For command-line use, NCA is installed with:

pip install network-config-analyzer

NCA can also be consumed as a Docker container, GitHub Action or Tekton Tasks.

Usage

Basic NCA command-line usage:

nca <query> [--resource_list <resource_list>] [--base_resource_list <base_resource_list>]

For example:

nca --connectivity --resource_list k8s  # Read policies and endpoints from a live Kubernetes cluster and report connectivity
# OR
nca --semantic_diff -r istio --base_resource_list ./old_config  # Compare two istio connectivity configs  

The full list of queries is:

• --sanity - Running several sanity checks on the given set of NetworkPolicies
• --connectivity - Get the list of allowed connections (as firewall rules or as a graph) as implied by the given set of NetworkPolicies
• --semantic_diff - Get the semantic connectivity difference (as firewall rules) between two sets of NetworkPolicy sets
• --equiv - Semantically comparing two sets of NetworkPolicy sets to decide whether they allow exactly the same traffic
• --interferes - Checking whether the given set of NetworkPolicies interferes with the base set of NetworkPolicies (allows more traffic between relevant endpoints)
• --permits - Checking whether the base set of NetworkPolicies permits the traffic explicitly specified in the given set of NetworkPolicies
• --forbids - Checking whether the base set of NetworkPolicies forbids the traffic explicitly specified in the given set of NetworkPolicies

The arguments to --resource_list and to --base_resource_list should be one of:

• a path to a yaml/json file defining NetworkPolicies and/or endpoints
• a path to a directory with files containing NetworkPolicies and/or endpoints
• a URL of a GitHub repository/dir/file with NetworkPolicies and/or endpoints
• The string k8s, instructing the tool to take all NetworkPolicies and endpoints from a Kubernetes cluster (using kubectl)
• The string calico, instructing the tool to take all NetworkPolicies and endpoints from a Kubernetes cluster with Calico (using calicoctl)
• The string istio, instructing the tool to take all AuthorizationPolicies and endpoints from a Kubernetes cluster with Istio (using kubectl)

Additional command-line switches:

• --resource_list <an argument from the list above>
  Specifies where to take namespaces, endpoints and NetworkPolicies from. This switch may be specified multiple times
  shorthand: -r
• --ns_list <an argument from the list above>
  Specifies where to take the list of namespaces from (and ignoring namespaces found by --resource_list). This switch may be specified multiple times
  default: the result of kubectl get ns
  shorthand: -n
• --pod_list <an argument from the list above>
  Specifies where to take the list of pods/endpoints from (and ignoring those found by --resource_list). This switch may be specified multiple times
  default: the result of kubectl get pods -A
  shorthand: -p
• --base_resource_list <an argument from the list above>
  Specifies where to take namespaces, endpoints and NetworkPolicies to compare against. This switch may be specified multiple times
• --base_np_list <an argument from the list above>
  The set of NetworkPolicies to compare against. Using this switch will ignore NetworkPolicies found by --base_resource_list
  default: The result of kubectl get netpol -A
  shorthand: -b
• --base_ns_list <an argument from the list above>
  Specifies files with list of namespaces to compare against (and ignoring those found by --base_resource_list). This switch may be specified multiple times
• --base_pod_list <an argument from the list above>
  Specifies files with list of pods/endpoints to compare against (and ignoring those found by --base_resource_list). This switch may be specified multiple times
• --namespace_subset <A comma separated list of namespaces (no spaces allowed)>
  Specifies the namespaces to be included in the 'connectivity' query results
• --deployment_subset <A comma separated list of deployments (no spaces allowed)>
  Specifies the deployments to be included in the 'connectivity' query results. Deployments' names can include the namespace prefix followed by the '/' character.
• --label_subset <A comma separated list of pairs (key:value) of labels (no spaces allowed)>
  Specifies the labels to include in the 'connectivity' query results. An element should include all the labels in this list to be included in the subset and in the results (AND operation). This switch may be specified multiple times and an element will be included if it matches one of the label-sets given in one of the switches (OR operation).
• --ghe_token <token>
  A valid token to access a GHE repository
• --period <minutes>
  Run NCA with given arguments every specified number of minutes
• --output_format <format>
  Output format specification (txt/yaml/csv/md/dot/jpg/html/txt_no_fw_rules).
  jpg or html: Graphviz executables must be installed and on user systems' PATH.
  txt_no_fw_rules: supported for ConnectivityMap and SemanticDiff queries, printing connectivity rules for each pair of peers, without minimization and grouping of rules. (excluding connections between workload to itself). default: txt
  shorthand: -o
• --file_out <file name>
  A file path to redirect output into.
  shorthand -f
• --expected_output <file name>
  A file path to the expected query output (for connectivity or semantic_diff queries).\
• --simplify_graph
  simplify the connectivity graph, (relevant only when output_format is dot, jpg or html)
• --pr_url <URL>
  Write output as GitHub PR comment. URL points to the relevant comments resource in the GitHub API.
  e.g., https://api.github.com/repos/shift-left-netconfig/online-boutique/issues/1/comments
• --output_endpoints
  Choose endpoints type in output (pods/deployments).
  default: deployments
  • --explain
    A pair of node names (comma separated) to explain the policies affecting their connection or lack of it. Relevant only for connectivity query.
    Connections including IP-Blocks will show only the configurations of the node in that connection (since, IP-Blocks does not have configurations). IP-Blocks should be places in CIDR format as seen in the query results (run the connectivity query first, to see the nodes there).
    e.g. default/pod-A1,default/deployment-B1.
  • --print_ipv6
    include IPv6 range in the query results even when the policies of the config do not contain any IPv6 addresses.

For more information on command-line switches combinations, see Common Query Patterns

Simulating live cluster missing resources:

• There are several key elements that may be assumed to exist in the live cluster and be missing form the topology configurations in the repo. In those case, nca will add complementary configurations to make the topology and the connectivity whole.
• Fine-tuning instructions can be found here

Exit Code Meaning:

The exit value of running a command-line without a scheme is the combination of three factors:

1. The result of running the query (0/1) as specified here
2. The result of comparing the query output with the expected output file contents (if given)
3. The query was not executed because of one of the reasons listed here. If this is true, then other factors are ignored.

And it can be in the range 0 to 7 as followed:

• 0 : query result is 0, output comparison passed.
• 1 : query result is 1, output comparison passed.
• 2 : query result is 0, output comparison failed.
• 3 : query result is 1, output comparison failed.
• [4-7] : query was not executed.

Running with a scheme file

Scheme files allow running NCA on multiple queries in a single command-line, and also for fine-tuning the output. To run NCAs with a scheme file, use the --scheme switch.

nca --scheme <scheme_file>

where scheme_file is a yaml file describing what to verify.

Scheme files should follow this specification. See an example scheme file.

Supported platforms

• Kubernetes
• Calico
• Istio (see what is supported here.)

Contributing

If you have any questions or issues you can create a new issue here.

Pull requests are very welcome! Make sure your patches are well tested. Ideally create a topic branch for every separate change you make. For example:

1. Fork the repo
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

License

All source files must include a Copyright and License header. The SPDX license header is preferred because it can be easily scanned.

If you would like to see the detailed LICENSE click here.

#
# Copyright 2020- IBM Inc. All rights reserved
# SPDX-License-Identifier: Apache2.0
#