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Set up GitLab merge request comments

Your deployment journey

Semgrep can create merge request (MR) comments in your GitLab repository. These comments provide a description of the issue detected by Semgrep and may offer possible solutions. These comments are a means for security teams, or any team responsible for creating standards to help their fellow developers write safe and standards-compliant code.

Automated comments on GitLab merge requests are displayed as follows:

Semgrep GitLab MR comment Figure An inline GitLab merge request comment.

Conditions for MR comment creation

MR comments appear for the following types of scans under these conditions:

Type of scanProduct nameTrigger conditionHow to set up
Static application security testing (SAST)Semgrep CodeA comment appears when a finding is generated by a rule in Comment or Block mode. This means you can fully customize what comments your developers receive.Complete the steps in the following sections:
  1. Confirm your Semgrep account's connection and access to your source code manager.
  2. Configure comments for Semgrep Code.
Software composition analysis (SCA)Semgrep Supply Chain (SSC)A comment appears only when the finding is reachable.Complete the steps in Confirm account connection and access.
SecretsSemgrep SecretsA comment appears on validated secrets.This product is in beta.
Contact support@semgrep.com to enable comments.

Comments from Supply Chain scans include the following information:

Risk
A description of the vulnerability, including the types of attack it is vulnerable to.
Fix
Indicates what versions to upgrade to, if any, that resolves or eliminates the vulnerability.
Reference
A link to additional information about the vulnerability from GitHub Advisory Database and the National Vulnerability Database (NVD), if available.
info

Pull or merge requests with vulnerabilities detected by SSC are not blocked from merging.

Steps to set up MR comments

Prerequisites

In addition to finishing the previous steps in your deployment journey, it is recommended to have completed a full scan on your default branch for the repository in which you want to receive comments.

Confirm your Semgrep account's connection

MR comments are enabled by default for users who have connected their GitLab organization (org) to Semgrep AppSec Platform. Confirm that you have the correct connection and access:

  1. In your Semgrep AppSec Platform account, click Settings > Source code managers.
  2. Check that an entry for your GitLab org exists and is correct.

Create a personal access token (PAT)

Creating a PAT grants the API scope to Semgrep, which lets it post comments.

  1. In GitLab, go to Profile > Access Tokens, and then add a token with api scope.
  2. Copy the token created in the previous step.
  3. For GitLab CI/CD users:
    1. Navigate to Your repository > Settings > CI/CD. The URL of the page where you are ends with: /username/project/-/settings/ci_cd.
    2. Under Variables click Expand, and then click Add variable.
    3. Enter PAT (change this placeholder name as necessary) in the Key field and paste the token value copied in step two to the Value field.
    4. Select the Mask variable checkbox option, and then clear the Protect variable checkbox option.
    5. Update your .gitlab-ci.yml file with variable GITLAB_TOKEN and value $PAT. Refer to the following sample, substituting the placeholder PAT with the name you created for this variable.
    semgrep:
    # A Docker image with Semgrep installed.
    image: semgrep/semgrep
    # Run the "semgrep ci" command on the command line of the docker image.
    script: semgrep ci

    rules:
    # Scan changed files in MRs, (diff-aware scanning):
    - if: $CI_MERGE_REQUEST_IID

    # Scan mainline (default) branches and report all findings.
    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH

    variables:
    # Connect to Semgrep AppSec Platform through your SEMGREP_APP_TOKEN.
    # Generate a token from Semgrep AppSec Platform > Settings
    # and add it as a variable in your GitLab CI/CD project settings.
    SEMGREP_APP_TOKEN: $SEMGREP_APP_TOKEN
    # Receive inline MR comments (requires Semgrep AppSec Platform account)
    GITLAB_TOKEN: $PAT
  4. For other CI providers:
    1. In your CI provider's interface, define the value of the PAT as a secret. Refer to your CI provider's documentation for steps to do this.
    2. Define the environment variable GITLAB_TOKEN and assign the PAT to it.

For more configuration options, see GitLab CI Sample.

Define environment variables needed for other CI providers

For CI providers aside from GitLab CI/CD, additional environment variables must be set:

These values do not have to be fixed or hardcoded. They can be variables passed to the job. For more information, see Sample CI configurations.

Configure comments for Semgrep Code

In addition to setting up the connection between Semgrep and GitLab, you must assign rules to Comment or Block mode. This customization enables you to:

  • Manage the amount of MR comments your developers receive.

  • Ensure that only rules that meet your criteria, such as high severity or high confidence rules, produce comments visible to developers, reducing noise.
tip

Rules in Block mode fail the CI job that runs on the MR. Depending on your workflow, this may prevent your MR from merging.

Set rules to Comment or Block mode

The following instructions let you customize what findings or security issues your developers see as comments in their PRs:

  1. In your Semgrep AppSec Platform account, click Rules > Policies. You are taken to the Policies page. Under Modes , you can quickly see if you have existing rules in either Comment or Block mode.
  2. Optional: Use the filters to quickly find rules to set to Comment or Block.
  3. Click the checkbox of the rules you want to set. You can use Ctrl + Click to select rules in bulk.
  4. Click Change modes.
  5. Click either Block or Comment.

You have successfully configured MR comments for Semgrep Code.



Receive comments in your VPN or on-premise SCM

To enable comments within self-hosted SCMs behind firewalls or VPNs (Virtual Private Networks):

  1. Add the following IP addresses to your VPN's ingress allowlist and egress allowlist, if you have one.
    # These IP addresses are inbound and outbound:
    35.166.231.235
    52.35.248.246
    52.34.137.110
    44.225.64.41
  2. Test that you are able to receive findings by manually triggering a scan through your CI provider.

Receiving PR or MR comments may require additional steps depending on the custom configuration of your VPN or SCM (for example, if you use a static IP without a hostname). Reach out to Semgrep support through the Semgrep Community Slack or send an email to support@semgrep.com for any concerns.

You've set up MR comments! Enable optional features provided in the following sections, or see Next steps.

Optional features

Enable autofix in GitLab repositories

Autofix is a Semgrep feature in which rules contain suggested fixes to resolve findings.

To enable autofix for all projects in your Semgrep AppSec Platform organization, follow these steps:

  1. In Semgrep AppSec Platform, click Settings on the left sidebar.
  2. Click Autofix toggle.

Dataflow traces in MR comments

Screenshot of a GitLab MR comment with dataflow traces Figure An inline GitLab pull request comment with dataflow traces.

With dataflow traces, Semgrep Code can provide you with a visualization of the path of tainted, or untrusted, data in specific findings. This path can help you track the sources and sinks of the tainted data as they propagate through the body of a function or a method. For general information about taint analysis, see Taint tracking.

When running Semgrep Code from the command line, you can pass in the flag --dataflow-traces to use this feature.

You can view dataflow traces in:

Get cross-file findings

To get cross-file (interfile) findings in your organization, follow the steps in Perform cross-file analysis.

View the path of tainted data in MR comments

To enable dataflow traces in your CI pipeline, fulfill the following prerequisites:

Prerequisites
  • Set up Semgrep to post GitLab merge request comments, as described on this page.
  • To obtain meaningful results of dataflow traces in MR comments, use cross-file analysis while scanning your repositories. To enable cross-file analysis, see Perform cross-file analysis.
  • Not all Semgrep rules or rulesets make use of taint tracking. Ensure that you have a ruleset, such as the default ruleset added in your Policies. If this ruleset is not added, go to https://semgrep.dev/p/default, and then click Add to Policy. You can add rules that use taint tracking from Semgrep Registry.

Next steps

You've finished setting up a core deployment of Semgrep 🎉.

Additional references


Not finding what you need in this doc? Ask questions in our Community Slack group, or see Support for other ways to get help.