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Patterns in Node Package Vulnerabilities Chetan Karande

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About Me ▪ Principal Engineer, DTCC ▪ Project Leader, OWASP NodeGoat Project ▪ Author

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532 packages/day

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~ 700,000 packages

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88 Disclosures

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603 Vulnerabilities

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1,098 Advisories

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npm audit Snyk CLI

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“By seeking and blundering we learn.” - Johann Wolfgang von Goethe

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1,084 + 528 1,023 Unique Advisories

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Insecure Access to File System

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Insecure Access to File System Pattern #1 Directory Traversal

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Root Cause: An insecure dependency vulnerable to Directory Traversal

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Root Cause behind Directory Traversal Missing or insufficient user input validation for path traversal characters before using it in a path to serve contents on the server.

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Root Cause for Directory Traversal Missing or insufficient user input validation for path traversal characters before using it in a URL to serve contents on the server. Examples: • / • ../ • %2f • %2e%2e/ • %2e%2e%2f,

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Preventing Directory Traversal ✓ If the path needs to be supplied from the user input, sanitize the input to remove path traversal characters (./ and ../ as well as encoded variations)

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Insecure Access to File System Pattern #2 Symlink Attack

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Symlink attack is like staying in a hotel and getting a really noisy neighbor... Symlink Attack

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Symlink Attack A malicious user sharing the host, could exploit this vulnerability to corrupt or destroy vital system or application files to which only the target application has the access.

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Root Cause for Symlink Attack • An application sharing the host server with other external users. • Using predictable file or folder names when writing to shared directories

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Example: The package writing logs to the shared /tmp directory with a predictable file name

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ln –s

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Preventing Symlink Attack ✓ Avoid using shared system folders.

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Example: The package using /tmp to buffer command results before returning values

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Preventing Symlink Attack ✓ Avoid using shared system folders. ✓ If you have to use a shared folder for writing non-sensitive data, use crypto module’s randomBytes method to generate random filenames.

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Sensitive Data Exposure

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“The more you leave out, the more you highlight what you leave in.” - Henry Green

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Sensitive Data Exposure Pattern #1 Leaking Application Secrets

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Root Causes for Leaking Application Secrets Application-specific secrets appearing at insecure places such as as: - code repositories, - log files, - client-side storage, - URLs, - application global namespace

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Example: Leaking the SSL private key in the code repository

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Example: URLs with authentication tokens appearing in the logs

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Example: OAuth Bearer Token appearing in the browser local-storage

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Preventing Application Secrets Leakage ✓ Securely store applications secrets in Hardware Security Module (HSM) or Key Management Services.

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Preventing Application Secrets Leakage ✓ Securely store applications secrets in Hardware Security Module (HSM) or Key Management Services. ✓ Mask any sensitive data before it appears in the log files.

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Preventing Application Secrets Leakage ✓ Securely store applications secrets in Hardware Security Module (HSM) or Key Management Services ✓ Mask any sensitive data before it appears in the log files ✓ To reduce impact of a leak, use short-lived tokens.

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Sensitive Data Exposure Pattern #2 Predictable Secrets (Insecure Randomness)

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Root causes for Insecure Randomness • Using Math.random() method is to generate random values in security- sensitive context (random tokens, resource IDs, or UUIDs). • Math.random() is cryptographically insecure. It can produce predictable values.

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Example: Using Math.random to generate UUID

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Example: Using Math.random() to generate Socket IDs

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Preventing Insecure Randomness ✓ Use crypto module to generate random numbers instead of Math.random()

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Preventing Insecure Randomness ✓ Use crypto module to generate random numbers instead of Math.random()

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Sensitive Data Exposure Pattern #3 Predictable Secrets (Non-constant Time Comparison)

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Root causes for Non-constant Time Comparison • Using fail-fast comparison logic to match user inputs against sensitive values. • JavaScript native string comparison operators (=== and ==) perform the non-constant time fail-first string comparison .

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Example: Using Fail Fast operators to compare csrf tokens

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Example: Using a Fail Fast iterator to compare byte arrays

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Preventing Timing Attacks ✓ Use a constant-time comparison logic that takes the same amount of time regardless of the input values.

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Preventing Timing Attacks ✓ Use a constant-time comparison logic that takes the same amount of time regardless of the input values.

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Sensitive Data Exposure Pattern #4 Remote Memory Exposure

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Root Cause for Remote Memory Exposure ▪ Prior to Node.js 8, the Buffer constructor that takes a number as an argument, generates a Buffer instance with uninitialized underlying memory.

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▪ Prior to Node.js 8, the Buffer constructor that takes a number as an argument, generates a Buffer instance with uninitialized underlying memory. ▪ The contents of a newly created Buffer remain unknown and might contain sensitive data. Root Cause for Remote Memory Exposure

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Examples of Uninitialized Memory Exposure Example: Using unsafe Buffer constructor

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Example: Using unsafe Buffer constructor

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Example: Using unsafe Buffer constructor

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Preventing Remote Memory Exposure ✓ Use a safe method Buffer.alloc(size) to create a buffer that is initialized with zeroes:

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Sensitive Data Exposure Pattern #5 Insecure Network Usage

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Root Cause for Insecure Network Usage ▪ Using insecure HTTP protocol to download resources as part of install scripts or at runtime.

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Root Cause for Insecure Network Usage ▪ Using insecure HTTP protocol to download resources as part of install scripts or at runtime.

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Preventing Insecure Network Usage ✓ Download resources over secure HTTPS connection. ✓ Provide an option for users to download dependencies in advance and specify the location path.

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Denial of Service

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Denial of Service Pattern #1 Exhausting System Resources

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Root Cause behind DoS by Exhausting System Resources • Allocating unrestricted amount of system resources based on the size of a user input.

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Example: Exceeding V8’s maximum string size limit

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Example: Exceeding V8’s maximum buffer size limit

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Example: Unrestricted file uploads exhausting file-system space

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Example: Instantiating large number of Objects based on a user input (very large array index: foo[0][1000000000]=bar)

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Preventing DoS by Exhausting System Resources ✓ Validate size of a user input before processing it

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Denial of Service Pattern #2: Keeping Event Loop Busy

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Node is fast when the work associated with each client at any given time is "small". - Node.js Docs

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Examples of DoS By Keeping Event Loop Busy • Running an execution loop whose iterations depend on the length of a user input.

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• Running an execution loop whose iterations depend on the length of a user input. • Using unsafe Regular Expressions Examples of DoS By Keeping Event Loop Busy

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Regular Expression Denial of Service (ReDoS) ▪ By default, regular expressions get executed in the main event loop thread ▪ Evil regex can take exponential execution time when applied to certain non- matching inputs.

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^(.*,)+(.+)?$/

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Input format: ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,\n Input Length Execution Time 25 2 sec 26 4 sec 27 9 sec 28 15 sec 30 1 minute 35 34 minutes

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Denial of Service Pattern #3 Crashing Event Loop By Unhandled Exceptions

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Common Causes of Unhandled Exceptions #1 Failing to Handle Invalid User Inputs

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• Caused by failing to validate user inputs for unexpected value, type, or shape before processing them

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Unexpected Character Example: Trailing \ in URL localhost:3000/index.html\

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Unexpected Object Value Example: Unexpected HTTP Header Value { 'accept-encoding': 'a;b' }

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Unexpected Object Shape Example: Type coercion via HTTP Request Parameters

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▪ User input coercion via HTTP Request Parameters in qs, Express, Koa // GET /search?conference=fluent request.query.conference //=> "fluent”

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▪ User input coercion via HTTP Request Parameters in qs, Express, Koa // GET /search?conference=fluent&conference=velocity request.query.conference //=> ["fluent”, “velocity”]

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▪ User input coercion via HTTP Request Parameters in qs, Express, Koa // GET /search?conference[]=fluent request.query.conference //=> ["fluent”]

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▪ User input coercion via HTTP Request Parameters in qs, Express, Koa // GET /search?conference[fluent][year]=2018 request.query.conference //=>

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▪ User input coercion via HTTP Request Parameters in qs, Express, Koa // GET /search?conference[fluent][year]=2018 request.query.conference //=> {fluent: { year: '2018' }}

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✓ Validate user inputs for expected values, type or shape before processing it. (using joi package, for example) Preventing Unhanded Exception Caused by Invalid User Input

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Common Causes of Unhandled Exceptions #2 Missing or Incorrect Operational Error Handling

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Four mechanisms to communicate operational errors in Node.js: 1. throw new Error('something bad happened!');

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Four mechanisms to communicate operational errors in Node.js: 1. throw new Error('something bad happened!'); 1. callback(new Error('something bad happened!'));

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Four mechanisms to communicate operational errors in Node.js: 1. throw new Error('something bad happened!'); 1. callback(new Error('something bad happened!')); 1. return Promise.reject(new Error('something bad happened!'));

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Four mechanisms to communicate operational errors in Node.js: 1. throw new Error('something bad happened!'); 1. callback(new Error('something bad happened!')); 1. return Promise.reject(new Error('something bad happened!')); 1. myEmitter.emit('error', new Error(something bad happened!'));

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Example: Failure to handle error object passed in the callback

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Preventing Unhanded Exception due to Operational Errors ✓ Be aware of the error delivery mechanism used by the invoked function and handle errors accordingly.

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Recap ▪ Insecure Access to File System - Pattern #1 Directory Traversal - Pattern #2 Symlink Attack

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Recap ▪ Sensitive Data Exposure - Pattern #1 Leaking Application Secrets - Pattern #2 Predictable Secrets (Insecure Randomness) - Pattern #3 Predictable Secrets (Non-constant Time Comparison) - Pattern #4 Remote Memory Exposure - Pattern #5 Insecure Network Usage

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Recap ▪ Denial of Service - Pattern #1 Exhausting System Resources - Pattern #2 Keeping Event Loop Busy - Pattern #3 Crashing Event Loop By Unhandled Exceptions

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Learning Resources

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Patterns in Node Package Vulnerabilities

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node.advisories.io

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node.advisories.io

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@karande_c

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