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Defining custom patterns for secret scanning

You can extend secret scanning for advanced security to detect secrets beyond the default patterns.

Secret scanning for advanced security is available for organization-owned repositories in GitHub Enterprise Cloud if your enterprise has a license for GitHub Advanced Security. For more information, see "GitHub's products."

About custom patterns for secret scanning

You can define custom patterns to identify secrets that are not detected by the default patterns supported by secret scanning. For example, you might have a secret pattern that is internal to your organization. For details of the supported secrets and service providers, see "Secret scanning patterns."

You can define custom patterns for your enterprise, organization, or repository. Secret scanning supports up to 500 custom patterns for each organization or enterprise account, and up to 100 custom patterns per repository.

Regular expression syntax for custom patterns

You can specify custom patterns for secret scanning for advanced security as one or more regular expressions.

  • Secret format: an expression that describes the format of the secret itself.
  • Before secret: an expression that describes the characters that come before the secret. By default, this is set to \A|[^0-9A-Za-z] which means that the secret must be at the start of a line or be preceded by a non-alphanumeric character.
  • After secret: an expression that describes the characters that come after the secret. By default, this is set to \z|[^0-9A-Za-z] which means that the secret must be followed by a new line or a non-alphanumeric character.
  • Additional match requirements: one or more optional expressions that the secret itself must or must not match.

For simple tokens you will usually only need to specify a secret format. The other fields provide flexibility so that you can specify more complex secrets without creating complex regular expressions. For an example of a custom pattern, see "Example of a custom pattern specified using additional requirements" below.

Secret scanning uses the Hyperscan library and only supports Hyperscan regex constructs, which are a subset of PCRE syntax. Hyperscan option modifiers are not supported. For more information on Hyperscan pattern constructs, see "Pattern support" in the Hyperscan documentation.

Defining a custom pattern for a repository

Before defining a custom pattern, you must ensure that secret scanning is enabled on your repository. For more information, see "Configuring secret scanning for your repositories."

  1. On GitHub.com, navigate to the main page of the repository.

  2. Under your repository name, click Settings. Repository settings button

  3. In the "Security" section of the sidebar, click Code security and analysis.

  4. Under "Code security and analysis", find "GitHub Advanced Security."

  5. Under "Secret scanning", under "Custom patterns", click New pattern.

  6. Enter the details for your new custom pattern:

    1. You must at least provide the name for your pattern, and a regular expression for the format of your secret pattern.
    2. You can click More options to provide other surrounding content or additional match requirements for the secret format.
    3. Provide a sample test string to make sure your configuration is matching the patterns you expect.

    Create a custom secret scanning pattern form

  7. When you're ready to test your new custom pattern, to identify matches in the repository without creating alerts, click Save and dry run.

  8. When the dry run finishes, you'll see a sample of results (up to 1000). Review the results and identify any false positive results. Screenshot showing results from dry run

  9. Edit the new custom pattern to fix any problems with the results, then, to test your changes, click Save and dry run.

    Note: The dry run feature is currently in beta and subject to change.

  10. When you're satisfied with your new custom pattern, click Publish pattern.

After your pattern is created, secret scanning scans for any secrets in your entire Git history on all branches present in your GitHub repository. For more information on viewing secret scanning alerts, see "Managing alerts from secret scanning."

Example of a custom pattern specified using additional requirements

A company has an internal token with five characteristics. They use the different fields to specify how to identify tokens as follows:

CharacteristicField and regular expression
Length between 5 and 10 charactersSecret format: [$#%@AA-Za-z0-9]{5,10}
Does not end in a .After secret: [^\.]
Contains numbers and uppercase lettersAdditional requirements: secret must match [A-Z] and [0-9]
Does not include more than one lowercase letter in a rowAdditional requirements: secret must not match [a-z]{2,}
Contains one of $%@!Additional requirements: secret must match [$%@!]

These tokens would match the custom pattern described above:

a9@AAfT!         # Secret string match: a9@AAfT
ee95GG@ZA942@aa  # Secret string match: @ZA942@a
a9@AA!ee9        # Secret string match: a9@AA

These strings would not match the custom pattern described above:

a9@AA.!
a@AAAAA
aa9@AA!ee9
aAAAe9

Defining a custom pattern for an organization

Before defining a custom pattern, you must ensure that you enable secret scanning for the repositories that you want to scan in your organization. To enable secret scanning on all repositories in your organization, see "Managing security and analysis settings for your organization."

  1. In the top right corner of GitHub.com, click your profile photo, then click Your organizations. Your organizations in the profile menu

  2. Next to the organization, click Settings. The settings button

  3. In the "Security" section of the sidebar, click Code security and analysis.

  4. Under "Code security and analysis", find "GitHub Advanced Security."

  5. Under "Secret scanning", under "Custom patterns", click New pattern.

  6. Enter the details for your new custom pattern:

    1. You must at least provide the name for your pattern, and a regular expression for the format of your secret pattern.
    2. You can click More options to provide other surrounding content or additional match requirements for the secret format.
    3. Provide a sample test string to make sure your configuration is matching the patterns you expect.

    Create a custom secret scanning pattern form

  7. When you're ready to test your new custom pattern, to identify matches in select repositories without creating alerts, click Save and dry run.

  8. Search for and select up to 10 repositories where you want to perform the dry run. Screenshot showing repositories selected for the dry run

  9. When you're ready to test your new custom pattern, click Dry run.

  10. When the dry run finishes, you'll see a sample of results (up to 1000). Review the results and identify any false positive results. Screenshot showing results from dry run

  11. Edit the new custom pattern to fix any problems with the results, then, to test your changes, click Save and dry run.

    Note: The dry run feature is currently in beta and subject to change.

  12. When you're satisfied with your new custom pattern, click Publish pattern.

After your pattern is created, secret scanning scans for any secrets in repositories in your organization, including their entire Git history on all branches. Organization owners and repository administrators will be alerted to any secrets found and can review the alert in the repository where the secret is found. For more information on viewing secret scanning alerts, see "Managing alerts from secret scanning."

Defining a custom pattern for an enterprise account

Before defining a custom pattern, you must ensure that you enable secret scanning for your enterprise account. For more information, see "Enabling GitHub Advanced Security for your enterprise."

Notes:

  • At the enterprise level, only the creator of a custom pattern can edit the pattern, and use it in a dry run.
  • Enterprise owners can only make use of dry runs on repositories that they have access to, and enterprise owners do not necessarily have access to all the organizations or repositories within the enterprise.
  1. In the top-right corner of GitHub.com, click your profile photo, then click Your enterprises. "Your enterprises" in drop-down menu for profile photo on GitHub Enterprise Cloud

  2. In the list of enterprises, click the enterprise you want to view. Name of an enterprise in list of your enterprises

  3. In the enterprise sidebar, click Policies. Policies tab in the enterprise account sidebar

  4. Under Policies, click "Advanced Security." "Advanced Security" policies in sidebar

  5. Under "GitHub Advanced Security", click the Security features tab.

  6. Under "Secret scanning custom patterns", click New pattern.

  7. Enter the details for your new custom pattern:

    1. You must at least provide the name for your pattern, and a regular expression for the format of your secret pattern.
    2. You can click More options to provide other surrounding content or additional match requirements for the secret format.
    3. Provide a sample test string to make sure your configuration is matching the patterns you expect.

    Create a custom secret scanning pattern form

  8. When you're ready to test your new custom pattern, to identify matches in the repository without creating alerts, click Save and dry run.

  9. Search for and select up to 10 repositories where you want to perform the dry run. Screenshot showing repositories selected for the dry run

  10. When you're ready to test your new custom pattern, click Dry run.

  11. When the dry run finishes, you'll see a sample of results (up to 1000). Review the results and identify any false positive results. Screenshot showing results from dry run

  12. Edit the new custom pattern to fix any problems with the results, then, to test your changes, click Save and dry run.

    Note: The dry run feature is currently in beta and subject to change.

  13. When you're satisfied with your new custom pattern, click Publish pattern.

After your pattern is created, secret scanning scans for any secrets in repositories within your enterprise's organizations with GitHub Advanced Security enabled, including their entire Git history on all branches. Organization owners and repository administrators will be alerted to any secrets found, and can review the alert in the repository where the secret is found. For more information on viewing secret scanning alerts, see "Managing alerts from secret scanning."

Editing a custom pattern

When you save a change to a custom pattern, this closes all the secret scanning alerts that were created using the previous version of the pattern.

  1. Navigate to where the custom pattern was created. A custom pattern can be created in a repository, organization, or enterprise account.
  2. Under "Secret scanning", to the right of the custom pattern you want to edit, click .
  3. When you have reviewed and tested your changes, click Save changes.

Removing a custom pattern

  1. Navigate to where the custom pattern was created. A custom pattern can be created in a repository, organization, or enterprise account.