git-secrets

Prevents you from committing passwords and other sensitive information to a git repository.

Contents

• Synopsis
• Description
• Installing git-secrets
  • *nix (Linux/macOS)
  • Windows
  • Homebrew (for macOS users)
• Advanced configuration
• Before making public a repository
• Options
  • Operation Modes
  • Options for --install
  • Options for --scan
  • Options for --list
  • Options for --add
  • Options for --register-aws
  • Options for --aws-provider
  • Options for --add-provider
• Defining prohibited patterns
• Ignoring false positives
• Secret providers
• Example walkthrough
• Skipping validation
• About

Synopsis

git secrets --scan [-r|--recursive] [--cached] [--no-index] [--untracked] [<files>...]
git secrets --scan-history
git secrets --install [-f|--force] [<target-directory>]
git secrets --list [--global]
git secrets --add [-a|--allowed] [-l|--literal] [--global] <pattern>
git secrets --add-provider [--global] <command> [arguments...]
git secrets --register-aws [--global]
git secrets --aws-provider [<credentials-file>]

Description

git-secrets scans commits, commit messages, and --no-ff merges to prevent adding secrets into your git repositories. If a commit, commit message, or any commit in a --no-ff merge history matches one of your configured prohibited regular expression patterns, then the commit is rejected.

Installing git-secrets

git-secrets must be placed somewhere in your PATH so that it is picked up by git when running git secrets.

*nix (Linux/macOS)

You can use the install target of the provided Makefile to install git secrets and the man page. You can customize the install path using the PREFIX and MANPREFIX variables.

make install

Windows

Run the provided install.ps1 powershell script. This will copy the needed files to an installation directory (%USERPROFILE%/.git-secrets by default) and add the directory to the current user PATH.

PS > ./install.ps1

Homebrew (for macOS users)

brew install git-secrets

Warning

You're not done yet! You MUST install the git hooks for every repo that you wish to use with git secrets --install.

Here's a quick example of how to ensure a git repository is scanned for secrets on each commit:

cd /path/to/my/repo
git secrets --install
git secrets --register-aws

Advanced configuration

Add a configuration template if you want to add hooks to all repositories you initialize or clone in the future.

git secrets --register-aws --global

Add hooks to all your local repositories.

git secrets --install ~/.git-templates/git-secrets
git config --global init.templateDir ~/.git-templates/git-secrets

Add custom providers to scan for security credentials.

git secrets --add-provider -- cat /path/to/secret/file/patterns

Before making public a repository

With git-secrets is also possible to scan a repository including all revisions:

git secrets --scan-history

Options

Operation Modes

Each of these options must appear first on the command line.

--install

Installs git hooks for a repository. Once the hooks are installed for a git repository, commits and non-fast-forward merges for that repository will be prevented from committing secrets.

--scan

Scans one or more files for secrets. When a file contains a secret, the matched text from the file being scanned will be written to stdout and the script will exit with a non-zero status. Each matched line will be written with the name of the file that matched, a colon, the line number that matched, a colon, and then the line of text that matched. If no files are provided, all files returned by git ls-files are scanned.

--scan-history

Scans repository including all revisions. When a file contains a secret, the matched text from the file being scanned will be written to stdout and the script will exit with a non-zero status. Each matched line will be written with the name of the file that matched, a colon, the line number that matched, a colon, and then the line of text that matched.

--list

Lists the git-secrets configuration for the current repo or in the global git config.

--add

Adds a prohibited or allowed pattern.

--add-provider

Registers a secret provider. Secret providers are executables that when invoked output prohibited patterns that git-secrets should treat as prohibited.

--register-aws

Adds common AWS patterns to the git config and ensures that keys present in ~/.aws/credentials are not found in any commit. The following checks are added:

• AWS Access Key IDs via (A3T[A-Z0-9]|AKIA|AGPA|AIDA|AROA|AIPA|ANPA|ANVA|ASIA)[A-Z0-9]{16}
• AWS Secret Access Key assignments via ":" or "=" surrounded by optional quotes
• AWS account ID assignments via ":" or "=" surrounded by optional quotes
• Allowed patterns for example AWS keys (AKIAIOSFODNN7EXAMPLE and wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY)
• Known credentials from ~/.aws/credentials

Note

While the patterns registered by this command should catch most instances of AWS credentials, these patterns are not guaranteed to catch them all. git-secrets should be used as an extra means of insurance -- you still need to do your due diligence to ensure that you do not commit credentials to a repository.

--aws-provider

Secret provider that outputs credentials found in an INI file. You can optionally provide the path to an INI file.

Options for --install

-f, --force

Overwrites existing hooks if present.

<target-directory>

When provided, installs git hooks to the given directory. The current directory is assumed if <target-directory> is not provided.

If the provided <target-directory> is not in a git repository, the directory will be created and hooks will be placed in <target-directory>/hooks. This can be useful for creating git template directories using with git init --template <target-directory>.

You can run git init on a repository that has already been initialized. From the git init documentation:

From the git documentation: Running git init in an existing repository is safe. It will not overwrite things that are already there. The primary reason for rerunning git init is to pick up newly added templates (or to move the repository to another place if --separate-git-dir is given).

The following git hooks are installed:

1. pre-commit: Used to check if any of the files changed in the commit use prohibited patterns.
2. commit-msg: Used to determine if a commit message contains a prohibited patterns.
3. prepare-commit-msg: Used to determine if a merge commit will introduce a history that contains a prohibited pattern at any point. Please note that this hook is only invoked for non fast-forward merges.

Note

Git only allows a single script to be executed per hook. If the repository contains Debian-style subdirectories like pre-commit.d and commit-msg.d, then the git hooks will be installed into these directories, which assumes that you've configured the corresponding hooks to execute all of the scripts found in these directories. If these git subdirectories are not present, then the git hooks will be installed to the git repo's .git/hooks directory.

Examples

Install git hooks to the current directory:

cd /path/to/my/repository
git secrets --install

Install git hooks to a repository other than the current directory:

git secrets --install /path/to/my/repository

Create a git template that has git-secrets installed, and then copy that template into a git repository:

git secrets --install ~/.git-templates/git-secrets
git init --template ~/.git-templates/git-secrets

Overwrite existing hooks if present:

git secrets --install -f

Options for --scan

-r, --recursive

Scans the given files recursively. If a directory is encountered, the directory will be scanned. If -r is not provided, directories will be ignored.

-r cannot be used alongside --cached, --no-index, or --untracked.

--cached

Searches blobs registered in the index file.

--no-index

Searches files in the current directory that is not managed by git.

--untracked

In addition to searching in the tracked files in the working tree, --scan also in untracked files.

<files>...

The path to one or more files on disk to scan for secrets.

If no files are provided, all files returned by git ls-files are scanned.

Examples

Scan all files in the repo:

git secrets --scan

Scans a single file for secrets:

git secrets --scan /path/to/file

Scans a directory recursively for secrets:

git secrets --scan -r /path/to/directory

Scans multiple files for secrets:

git secrets --scan /path/to/file /path/to/other/file

You can scan by globbing:

git secrets --scan /path/to/directory/*

Scan from stdin:

echo 'hello!' | git secrets --scan -

Options for --list

--global

Lists only git-secrets configuration in the global git config.

Options for --add

--global

Adds patterns to the global git config

-l, --literal

Escapes special regular expression characters in the provided pattern so that the pattern is searched for literally.

-a, --allowed

Mark the pattern as allowed instead of prohibited. Allowed patterns are used to filter out false positives.

<pattern>

The regex pattern to search.

Examples

Adds a prohibited pattern to the current repo:

git secrets --add '[A-Z0-9]{20}'

Adds a prohibited pattern to the global git config:

git secrets --add --global '[A-Z0-9]{20}'

Adds a string that is scanned for literally (+ is escaped):

git secrets --add --literal 'foo+bar'

Add an allowed pattern:

git secrets --add -a 'allowed pattern'

Options for --register-aws

--global

Adds AWS specific configuration variables to the global git config.

Options for --aws-provider

[<credentials-file>]

If provided, specifies the custom path to an INI file to scan. If not provided, ~/.aws/credentials is assumed.

Options for --add-provider

--global

Adds the provider to the global git config.

<command>

Provider command to invoke. When invoked the command is expected to write prohibited patterns separated by new lines to stdout. Any extra arguments provided are passed on to the command.

Examples

Registers a secret provider with arguments:

git secrets --add-provider -- git secrets --aws-provider

Cats secrets out of a file:

git secrets --add-provider -- cat /path/to/secret/file/patterns

Defining prohibited patterns

egrep-compatible regular expressions are used to determine if a commit or commit message contains any prohibited patterns. These regular expressions are defined using the git config command. It is important to note that different systems use different versions of egrep. For example, when running on macOS, you will use a different version of egrep than when running on something like Ubuntu (BSD vs GNU).

You can add prohibited regular expression patterns to your git config using git secrets --add <pattern>.

Ignoring false positives

Sometimes a regular expression might match false positives. For example, git commit SHAs look a lot like AWS access keys. You can specify many different regular expression patterns as false positives using the following command:

git secrets --add --allowed 'my regex pattern'

You can also add regular expressions patterns to filter false positives to a .gitallowed file located in the repository's root directory. Lines starting with # are skipped (comment line) and empty lines are also skipped.

First, git-secrets will extract all lines from a file that contain a prohibited match. Included in the matched results will be the full path to the name of the file that was matched, followed by ':', followed by the line number that was matched, followed by the entire line from the file that was matched by a secret pattern. Then, if you've defined allowed regular expressions, git-secrets will check to see if all of the matched lines match at least one of your registered allowed regular expressions. If all of the lines that were flagged as secret are canceled out by an allowed match, then the subject text does not contain any secrets. If any of the matched lines are not matched by an allowed regular expression, then git-secrets will fail the commit/merge/message.

Important

Just as it is a bad practice to add prohibited patterns that are too greedy, it is also a bad practice to add allowed patterns that are too forgiving. Be sure to test out your patterns using ad-hoc calls to git secrets --scan $filename to ensure they are working as intended.

Secret providers

Sometimes you want to check for an exact pattern match against a set of known secrets. For example, you might want to ensure that no credentials present in ~/.aws/credentials ever show up in a commit. In these cases, it's better to leave these secrets in one location rather than spread them out across git repositories in git configs. You can use "secret providers" to fetch these types of credentials. A secret provider is an executable that when invoked outputs prohibited patterns separated by new lines.

You can add secret providers using the --add-provider command:

git secrets --add-provider -- git secrets --aws-provider

Notice the use of --. This ensures that any arguments associated with the provider are passed to the provider each time it is invoked when scanning for secrets.

Example walkthrough

Let's take a look at an example. Given the following subject text (stored in /tmp/example):

This is a test!
password=ex@mplepassword
password=******
More test...

And the following registered patterns:

git secrets --add 'password\s*=\s*.+'
git secrets --add --allowed --literal 'ex@mplepassword'

Running git secrets --scan /tmp/example, the result will result in the following error output:

/tmp/example:3:password=******

[ERROR] Matched prohibited pattern

Possible mitigations:
- Mark false positives as allowed using: git config --add secrets.allowed ...
- List your configured patterns: git config --get-all secrets.patterns
- List your configured allowed patterns: git config --get-all secrets.allowed
- Use --no-verify if this is a one-time false positive

Breaking this down, the prohibited pattern value of password\s*=\s*.+ will match the following lines:

/tmp/example:2:password=ex@mplepassword
/tmp/example:3:password=******

...But the first match will be filtered out due to the fact that it matches the allowed regular expression of ex@mplepassword. Because there is still a remaining line that did not match, it is considered a secret.

Because that matching lines are placed on lines that start with the filename and line number (e.g., /tmp/example:3:...), you can create allowed patterns that take filenames and line numbers into account in the regular expression. For example, you could whitelist an entire file using something like:

git secrets --add --allowed '/tmp/example:.*'
git secrets --scan /tmp/example && echo $?
# Outputs: 0

Alternatively, you could allow a specific line number of a file if that line is unlikely to change using something like the following:

git secrets --add --allowed '/tmp/example:3:.*'
git secrets --scan /tmp/example && echo $?
# Outputs: 0

Keep this in mind when creating allowed patterns to ensure that your allowed patterns are not inadvertently matched due to the fact that the filename is included in the subject text that allowed patterns are matched against.

Skipping validation

Use the --no-verify option in the event of a false positive match in a commit, merge, or commit message. This will skip the execution of the git hook and allow you to make the commit or merge.

About

• Author: Michael Dowling
• Issue tracker: This project's source code and issue tracker can be found at https://github.com/awslabs/git-secrets
• Special thanks to Adrian Vatchinsky and Ari Juels of Cornell University for providing suggestions and feedback.

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