eslint-plugin-no-secrets

An eslint rule that searches for potential secrets/keys in code and JSON files.

This plugin has two rules:

• no-secrets: Find potential secrets using cryptographic entropy or patterns in the AST (acts like a standard eslint rule, more configurable)
• no-pattern-match: Find potential secrets in text (acts like grep, less configurable, but potentially more flexible)

---

• 1. Usage
  • 1.1. Flat config
  • 1.2. eslintrc
  • 1.3. Include JSON files
    • 1.3.1. Include JSON files with in "flat configs"
• 2. no-secrets
  • 2.1. no-secrets examples
  • 2.2. When it's really not a secret
    • 2.2.1. Either disable it with a comment
    • 2.2.2. use the ignoreContent to ignore certain content
    • 2.2.3. Use ignoreIdentifiers to ignore certain variable/property names
    • 2.2.4. Use additionalDelimiters to further split up tokens
  • 2.3. no-secrets Options
• 3. no-pattern-match
  • 3.1. no-pattern-match options
• 4. Acknowledgements

1. Usage

npm i -D eslint-plugin-no-secrets

1.1. Flat config

eslint.config.js

import noSecrets from "eslint-plugin-no-secrets";

export default [
  {
    files: ["**/*.js"],
    plugins: {
      "no-secrets": noSecrets,
    },
    rules: {
      "no-secrets/no-secrets": "error",
    },
  },
];

1.2. eslintrc

.eslintrc

{
  "plugins": ["no-secrets"],
  "rules": {
    "no-secrets/no-secrets": "error"
  }
}

//Found a string with entropy 4.3 : "ZWVTjPQSdhwRgl204Hc51YCsritMIzn8B=/p9UyeX7xu6KkAGqfm3FJ+oObLDNEva"
const A_SECRET =
  "ZWVTjPQSdhwRgl204Hc51YCsritMIzn8B=/p9UyeX7xu6KkAGqfm3FJ+oObLDNEva";
//Found a string that matches "AWS API Key" : "AKIAIUWUUQQN3GNUA88V"
const AWS_TOKEN = "AKIAIUWUUQQN3GNUA88V";

1.3. Include JSON files

To include JSON files, install eslint-plugin-jsonc

npm install --save-dev eslint-plugin-jsonc

Then in your .eslint configuration file, extend the jsonc base config

{
  "extends": ["plugin:jsonc/base"]
}

1.3.1. Include JSON files with in "flat configs"

eslint.config.js

import noSecrets from "eslint-plugin-no-secrets";
import jsoncExtend from "eslint-plugin-jsonc";

export default [
  ...jsoncExtend.configs["flat/recommended-with-jsonc"],
  {
    languageOptions: { ecmaVersion: 6 },
    plugins: {
      "no-secrets": noSecrets,
    },
    rules: {
      "no-secrets/no-secrets": "error",
    },
  },
];

2. no-secrets

no-secrets is a rule that does two things:

1. Search for patterns that often contain sensitive information
2. Measure cryptographic entropy to find potentially leaked secrets/passwords

It's modeled after early truffleHog, but acts on ECMAscripts AST. This allows closer inspection into areas where secrets are commonly leaked like string templates or comments.

2.1. no-secrets examples

Decrease the tolerance for entropy

{
  "plugins": ["no-secrets"],
  "rules": {
    "no-secrets/no-secrets": ["error", { "tolerance": 3.2 }]
  }
}

Add additional patterns to check for certain token formats.
Standard patterns can be found here

{
  "plugins": ["no-secrets"],
  "rules": {
    "no-secrets/no-secrets": [
      "error",
      {
        "additionalRegexes": {
          "Basic Auth": "Authorization: Basic [A-Za-z0-9+/=]*"
        }
      }
    ]
  }
}

2.2. When it's really not a secret

2.2.1. Either disable it with a comment

// Set of potential base64 characters
// eslint-disable-next-line no-secrets/no-secrets
const BASE64_CHARS =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

This will tell future maintainers of the codebase that this suspicious string isn't an oversight

2.2.2. use the ignoreContent to ignore certain content

{
  "plugins": ["no-secrets"],
  "rules": {
    "no-secrets/no-secrets": ["error", { "ignoreContent": "^ABCD" }]
  }
}

2.2.3. Use ignoreIdentifiers to ignore certain variable/property names

{
  "plugins": ["no-secrets"],
  "rules": {
    "no-secrets/no-secrets": [
      "error",
      { "ignoreIdentifiers": ["BASE64_CHARS"] }
    ]
  }
}

2.2.4. Use additionalDelimiters to further split up tokens

Tokens will always be split up by whitespace within a string. However, sometimes words that are delimited by something else (e.g. dashes, periods, camelcase words). You can use additionalDelimiters to handle these cases.

For example, if you want to split words up by the character . and by camelcase, you could use this configuration:

{
  "plugins": ["no-secrets"],
  "rules": {
    "no-secrets/no-secrets": [
      "error",
      { "additionalDelimiters": [".", "(?=[A-Z][a-z])"] }
    ]
  }
}

2.3. no-secrets Options

Option	Description	Default	Type
tolerance	Minimum "randomness"/entropy allowed. Only strings above this threshold will be shown.	4	number
additionalRegexes	Object of additional patterns to check. Key is check name and value is corresponding pattern	{}	{[regexCheckName:string]:string | RegExp}
ignoreContent	Will ignore the entire string if matched. Expects either a pattern or an array of patterns. This option takes precedent over additionalRegexes and the default regular expressions	[]	string | RegExp | (string|RegExp)[]
ignoreModules	Ignores strings that are an argument in import() and require() or is the path in an import statement.	true	boolean
ignoreIdentifiers	Ignores the values of properties and variables that match a pattern or an array of patterns.	[]	string | RegExp | (string|RegExp)[]
ignoreCase	Ignores character case when calculating entropy. This could lead to some false negatives	false	boolean
additionalDelimiters	In addition to splitting the string by whitespace, tokens will be further split by these delimiters	[]	(string|RegExp)[]

3. no-pattern-match

While this rule was originally made to take advantage of ESLint's AST, sometimes you may want to see if a pattern matches any text in a file, kinda like grep.

For example, if we configure as follows:

import noSecrets from "eslint-plugin-no-secrets";

//Flat config

export default [
  {
    files: ["**/*.js"],
    plugins: {
      "no-secrets": noSecret,
    },
    rules: {
      "no-secrets/no-pattern-match": [
        "error",
        { patterns: { SecretJS: /const SECRET/, SecretJSON: /\"SECRET\"/ } },
      ],
    },
  },
];

We would match const SECRET, but not var SECRET. We would match keys that were called "SECRET" in JSON files if they were configured to be scanned.

3.1. no-pattern-match options

Option	Description	Default	Type
patterns	An object of patterns to check the text contents of files against	{}	{[regexCheckName:string]:string | RegExp}

4. Acknowledgements

Huge thanks to truffleHog for the inspiration, the regexes, and the measure of entropy.