API Security Best Practices

By nature, APIs are meant to be used. Even if all of your users are internal, security problems can still arise. To help with this, we’ve assembled a list of best practices to keep in mind when securing and locking-down an API or web service.

Use HTTPS

The web has moved past standard HTTP. With browser vendors flagging URLs that don’t use a secure layer, it’s time to do the same for your API. HTTPS uses Transport Layer Security (TLS) to encrypt traffic. This means communication between the client and server is encrypted. For your API, this means the content sent from your API is secured from third-parties, but more importantly it means that the access credentials are secured.

Authenticate

Speaking of access credentials, the clearest way to avoid unexpected use of your API is to ensure proper authentication. Authentication is how you allow or prevent access to the API. Even publicly available APIs that are free to use should consider an authentication strategy. This allows you to limit or remove users that abuse the API, and also protect your users by giving them the ability to reset their credentials if needed. You can learn more about types of API authentication in our article on the three most common authentication methods.

Authorize

Authentication’s sibling is authorization. Where authentication is concerned with who the user of your API is, authorization focuses on what they have access to. For example, free plan users may only be authorized to access a subset of your full API. When you think about integrations like social login, the user authorizes your application to read their profile data from the social platform.

Secure endpoints AND resources (Object level authorization)

It’s common to secure an endpoint or set of endpoints through authorization. A more future-proof approach is to secure the individual resources as well. This prevents misconfigured, endpoint-level authorization from reaching your data. It also means that the endpoints themselves aren’t restricted by user type, but instead the resource controls who can and cannot view it.

Rate limit

When we think of security, we often think of inappropriate access. It can also be useful to think of security as managing resources. Rate-limiting is a technique for throttling the usage of an API. It can protect your resources financially, but also ensure that your servers aren’t overloaded by a flood of requests at one time. Many rate-limiting approaches are time-based. They can be set for a billing period to handle overall usage, as well as use a “burst” approach to limit large influxes of requests. If you’ve ever seen the 429 HTTP status code, you’ve experienced rate-limiting.

Validate and sanitize input

One of the oldest attack points for web applications is input fields. The way we access data may have changed, but the need to validate any user input hasn’t. Client-side validation is helpful for preventing mistakes and improving the user experience, but your API needs to also validate and sanitize all input before acting on it. Sanitization strips malicious or invalid code from requests. Validation ensures that the data meets the necessary criteria that your resources expect. This could be type and shape, or even factors like password structure.

Expose only what is needed

It can be tempting to take a shortcut and directly map data models to endpoints. Not only can this provide overly-verbose responses and increase bandwidth usage, but it can also expose data that users don’t need access to. For example, consider a /user endpoint that returns the user’s profile. It may need some basic information about the user, but it doesn’t need the user’s password or access levels.

Configure error messages

In addition to sanitizing data that goes into your API, you’ll want to sanitize the information that comes out of it. Error messages play a key role in helping users understand that a problem occurred, but make sure not to leak any sensitive data. Providing end-users with details about the structure of your internal code can open up areas for attackers to focus on. Make sure to configure error messages to provide enough information to help users debug and enough for them to report problems, but not enough to expose the inner workings of your application or sensitive data.

Don’t expose sensitive info

To build on protecting sensitive data, make sure not to expose details in JSON web tokens (JWTs) or cookies. The body of a JWT have the illusion of being secure, but can easily be decoded. Because of this, you should avoid including user information that could be used to access your application. The same advice goes for URLs as well. Make sure query strings aren’t exposing sensitive details.

Assess your dependencies

We no longer develop in a silo. A good portion of every codebase now contains libraries, middleware, and a variety of dependencies from outside sources. While it is generally safe to assume that popular packages are “battle-tested”, that doesn’t mean they aren’t completely safe from vulnerabilities. Make sure to assess your dependencies. Are they well maintained? Are you using the latest version? Is there a history of problems? Perhaps more importantly: Do you really need a library for what you’re doing?

#api #security

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Top 10 API Security Threats Every API Team Should Know

As more and more data is exposed via APIs either as API-first companies or for the explosion of single page apps/JAMStack, API security can no longer be an afterthought. The hard part about APIs is that it provides direct access to large amounts of data while bypassing browser precautions. Instead of worrying about SQL injection and XSS issues, you should be concerned about the bad actor who was able to paginate through all your customer records and their data.

Typical prevention mechanisms like Captchas and browser fingerprinting won’t work since APIs by design need to handle a very large number of API accesses even by a single customer. So where do you start? The first thing is to put yourself in the shoes of a hacker and then instrument your APIs to detect and block common attacks along with unknown unknowns for zero-day exploits. Some of these are on the OWASP Security API list, but not all.

Insecure pagination and resource limits

Most APIs provide access to resources that are lists of entities such as /users or /widgets. A client such as a browser would typically filter and paginate through this list to limit the number items returned to a client like so:

First Call: GET /items?skip=0&take=10 
Second Call: GET /items?skip=10&take=10

However, if that entity has any PII or other information, then a hacker could scrape that endpoint to get a dump of all entities in your database. This could be most dangerous if those entities accidently exposed PII or other sensitive information, but could also be dangerous in providing competitors or others with adoption and usage stats for your business or provide scammers with a way to get large email lists. See how Venmo data was scraped

A naive protection mechanism would be to check the take count and throw an error if greater than 100 or 1000. The problem with this is two-fold:

1. For data APIs, legitimate customers may need to fetch and sync a large number of records such as via cron jobs. Artificially small pagination limits can force your API to be very chatty decreasing overall throughput. Max limits are to ensure memory and scalability requirements are met (and prevent certain DDoS attacks), not to guarantee security.
2. This offers zero protection to a hacker that writes a simple script that sleeps a random delay between repeated accesses.

skip = 0
while True:    response = requests.post('https://api.acmeinc.com/widgets?take=10&skip=' + skip),                      headers={'Authorization': 'Bearer' + ' ' + sys.argv[1]})    print("Fetched 10 items")    sleep(randint(100,1000))    skip += 10

How to secure against pagination attacks

To secure against pagination attacks, you should track how many items of a single resource are accessed within a certain time period for each user or API key rather than just at the request level. By tracking API resource access at the user level, you can block a user or API key once they hit a threshold such as “touched 1,000,000 items in a one hour period”. This is dependent on your API use case and can even be dependent on their subscription with you. Like a Captcha, this can slow down the speed that a hacker can exploit your API, like a Captcha if they have to create a new user account manually to create a new API key.

Insecure API key generation

Most APIs are protected by some sort of API key or JWT (JSON Web Token). This provides a natural way to track and protect your API as API security tools can detect abnormal API behavior and block access to an API key automatically. However, hackers will want to outsmart these mechanisms by generating and using a large pool of API keys from a large number of users just like a web hacker would use a large pool of IP addresses to circumvent DDoS protection.

How to secure against API key pools

The easiest way to secure against these types of attacks is by requiring a human to sign up for your service and generate API keys. Bot traffic can be prevented with things like Captcha and 2-Factor Authentication. Unless there is a legitimate business case, new users who sign up for your service should not have the ability to generate API keys programmatically. Instead, only trusted customers should have the ability to generate API keys programmatically. Go one step further and ensure any anomaly detection for abnormal behavior is done at the user and account level, not just for each API key.

Accidental key exposure

APIs are used in a way that increases the probability credentials are leaked:

1. APIs are expected to be accessed over indefinite time periods, which increases the probability that a hacker obtains a valid API key that’s not expired. You save that API key in a server environment variable and forget about it. This is a drastic contrast to a user logging into an interactive website where the session expires after a short duration.
2. The consumer of an API has direct access to the credentials such as when debugging via Postman or CURL. It only takes a single developer to accidently copy/pastes the CURL command containing the API key into a public forum like in GitHub Issues or Stack Overflow.
3. API keys are usually bearer tokens without requiring any other identifying information. APIs cannot leverage things like one-time use tokens or 2-factor authentication.

If a key is exposed due to user error, one may think you as the API provider has any blame. However, security is all about reducing surface area and risk. Treat your customer data as if it’s your own and help them by adding guards that prevent accidental key exposure.

How to prevent accidental key exposure

The easiest way to prevent key exposure is by leveraging two tokens rather than one. A refresh token is stored as an environment variable and can only be used to generate short lived access tokens. Unlike the refresh token, these short lived tokens can access the resources, but are time limited such as in hours or days.

The customer will store the refresh token with other API keys. Then your SDK will generate access tokens on SDK init or when the last access token expires. If a CURL command gets pasted into a GitHub issue, then a hacker would need to use it within hours reducing the attack vector (unless it was the actual refresh token which is low probability)

Exposure to DDoS attacks

APIs open up entirely new business models where customers can access your API platform programmatically. However, this can make DDoS protection tricky. Most DDoS protection is designed to absorb and reject a large number of requests from bad actors during DDoS attacks but still need to let the good ones through. This requires fingerprinting the HTTP requests to check against what looks like bot traffic. This is much harder for API products as all traffic looks like bot traffic and is not coming from a browser where things like cookies are present.

Stopping DDoS attacks

The magical part about APIs is almost every access requires an API Key. If a request doesn’t have an API key, you can automatically reject it which is lightweight on your servers (Ensure authentication is short circuited very early before later middleware like request JSON parsing). So then how do you handle authenticated requests? The easiest is to leverage rate limit counters for each API key such as to handle X requests per minute and reject those above the threshold with a 429 HTTP response. There are a variety of algorithms to do this such as leaky bucket and fixed window counters.

Incorrect server security

APIs are no different than web servers when it comes to good server hygiene. Data can be leaked due to misconfigured SSL certificate or allowing non-HTTPS traffic. For modern applications, there is very little reason to accept non-HTTPS requests, but a customer could mistakenly issue a non HTTP request from their application or CURL exposing the API key. APIs do not have the protection of a browser so things like HSTS or redirect to HTTPS offer no protection.

How to ensure proper SSL

Test your SSL implementation over at Qualys SSL Test or similar tool. You should also block all non-HTTP requests which can be done within your load balancer. You should also remove any HTTP headers scrub any error messages that leak implementation details. If your API is used only by your own apps or can only be accessed server-side, then review Authoritative guide to Cross-Origin Resource Sharing for REST APIs

Incorrect caching headers

APIs provide access to dynamic data that’s scoped to each API key. Any caching implementation should have the ability to scope to an API key to prevent cross-pollution. Even if you don’t cache anything in your infrastructure, you could expose your customers to security holes. If a customer with a proxy server was using multiple API keys such as one for development and one for production, then they could see cross-pollinated data.

#api management #api security #api best practices #api providers #security analytics #api management policies #api access tokens #api access #api security risks #api access keys

API Security Weekly: Issue #101

After the special 100th edition last week, which was all about API security advice from the industry’s thought leaders, this week we are back to our regular API security news, and we have twice the number of them, from the past two weeks.

Vulnerability: Giggle

Giggle is a women-only social network and mobile app. It is meant to be a safe place for everyone on the network but, turns out it was not all that safe: researchers from Digital Interruption found some serious API flaws in it.

The team ran the app through a proxy and observed the API traffic. They found that the API behind the app effectively had a query language:

This meant that they could query any user record:

The API returned full user info, even when the queried record was another user (classical BOLA/IDOR):

#security #integration #api #cybersecurity #apis #api security #api vulnerabilites #api newsletter #security newsletter

Security Best Practices for REST APIs

In the modern era, REST APIs become an integral part of the applications. By adopting the REST APIs, you can expose your services to web applications or mobile applications and all other digital platforms.

REST APIs must be built as a stateless service. REST API best practices deserve a separate article. This article primarily focuses only on security best practices for REST APIs.

Below are the key concepts that should be considered while designing the REST APIs.

• Authentication/authorization
• Input validations and sanitization
• Defining content-types
• Output encoding
• Rate limiters
• Security for data in transit and storage
• Responding with appropriate status codes to avoid the ambiguity

Before delving into details let us first understand authentication and authorization.

• Authentication: Authentication is the process of identifying whether the credentials passed along with the request are valid or not. here credentials can be passed as user id and password or a token assigned for the user session.
• Authorization: Authorization is the process of identifying whether the received request is allowed to access the requested endpoint or method.

In the request processing pipeline, authentication comes first and authorization comes next. Authorization occurs only after successful authentication of the request.

Below are the most widely used authentication types when dealing with Remote APIs (REST APIs / Web Services).

Basic Auth is the simplest way of dealing with Authentication when compared to other methodologies.

In the Basic Auth, the user has to send the user id and password in the format of userid:password encoded in base64 format. This method is preferred only over the https protocol only. This is highly discouraged to use over HTTP as your credentials are transferring in plain format.

Plain Text

1

Authorization: Basic base64(userid:password)

Bearer Token Authentication is also known as Token-based Authentication. When the user logs into an application using the credentials, the Authorization server generates a cryptographic token to uniquely identifies the user. the applications can use the token to identify the user after a successful login. i.e. The application is required to send this token when accessing protected resources.

Similar to Basic Authentication, Bearer tokens are only recommended to send over HTTPS only.

Authorization Bearer <your token>API Tokens are widely used in the web services/REST APIs security before the evaluation of Client-side frameworks. Still, many organizations use the API Tokens as a security measure for the APIs. This is the simplest way of implementing the security in REST APIs.

This is recommended when providing the communication between server to server requests. It is recommended to use the IP Address registration as well when using the API keys. i.e. API Token is uniquely identified along with the IP Address. This is not recommended to use as a methodology for end-user authentication and Authorization.

The API Key key can be sent as part of the query string or _Authorization token _or custom header or as part of the data.

OAuth2.0 is an authorization framework that allows users to grant a third-party website or application to access the user’s protected resources without revealing their credentials or identity. For that purpose, an OAuth 2.0 server issues access tokens that the client applications can use to access protected resources on behalf of the resource owner.

You probably see this option in the form of ‘Login using Google’, ‘Login using Facebook’, ‘Login using Github’ etc.

By default, OAuth generates the access tokens in the format of JWT (JSON web tokens). JWTs contain three parts: a header, a payload, and a signature.

• Header: metadata about the token like cryptographic algorithms used to generate the token.
• Payload: payload contains the Subject (usually identifier of the user), claims (also known as permissions or grants), and other information like audience and expiration time, etc.
• Signature: used to validate the token is trustworthy and has not been tampered with.
• Below are the OAuth roles you must aware of when dealing OAuth2.0
• Resource Owner: the entity that can grant access to a protected resource. Typically this is the end-user.
• Resource Server: The server that is hosting the protected resources
• Client: the app requesting access to a protected resource on behalf of the Resource Owner.
• Authorization Server: the server that authenticates the Resource Owner, and issues Access Tokens after getting proper authorization.

OAuth2.0 provides various flows or grant types suitable for different types of API clients. Grant Types are out of scope for this article.

OIDC is a simple identity layer built on top of the OAuth2.0. OIDC defines a sign-in flow that enables a client application to authenticate a user, and to obtain information (or “claims”) about that user, such as the user name, email, and so on. User identity information is encoded in a secure JSON Web Token (JWT), called ID token.

In the Open ID Connect, Request flow will happen as below.

1. user will be navigated to the Authorization server from the client app
2. The user enters the credentials to identify the user
3. Upon successful authentication, Server sends back the user to client along with authorization code
4. Client app requests the Authorization server for tokens (Access Token and Id Token) using the authorization code (we can use nonce here to incorporated additional security)
5. Authorization server responds back with tokens.

Input validation should be applied to both syntactical and semantic levels.

• **Syntactical: **should enforce correct syntax of structured fields (e.g. SSN, date, currency symbol).
• **Semantic: **should enforce correctness of their values in the specific business context (e.g. start date is before the end date, price is within expected range).

Basic Input validation guidelines

• Define an implicit input validation by using strong types like numbers, booleans, dates, times, or fixed data ranges in API parameters.
• Constrain string inputs with regular expressions.
• Use whitelisting and blacklisting techniques
• Define min and maximum lengths as a mandatory
• Enforce Input validations on client-side and server-side
• Reject unexpected/illegal content with valid error messages

We must define the allowed content types explicitly. It is always good practice to define the valid content types and share them with the required shareholders. Upon receiving an unexpected or missing content-type header, API must respond with HTTP response status 406 Unacceptable or 415 Unsupported Media Type.

Content of given resources must be interpreted correctly by the browser, the server should always send the Content-Type header with the correct Content-Type, and preferably the Content-Type header should include a charset.

JSON encoders must be used when dealing with JSON Data.

Rate limiters allow you to secure your APIs from the DDoS attacks. When exposing your API to publicly you must define the rate limiters. If you are opt-in for any cloud provider tools, they explicitly provide the rate-limiting capabilities to the public faced resources. you must adjust the configurations accordingly to your needs.

Ensure data is sent over HTTPS only. if any user tries to access over HTTP, you should upgrade it HTTPS and handle the request

Data in storage must be protected using best security practices. All the cloud providers provide you the inbuilt security (Encryption)for your backups.

Below are few common status codes used along with REST APIs

• 201 - Created
• 200 - OK
• 202 - Accepted and queued for processing
• 204 - No Content
• 304 - Not Modified
• 400 - Bad Request
• 401 - UnAuthorized
• 403 - Forbidden
• 404 - Not Found
• 405 - Method Not Allowed
• 406 - Not Acceptable (Used with Content Types)
• 415 - Unsupported Media Type
• 429 - Two Many requests

Please share your thoughts in the comments box to improve it further.

If you found this helpful please share it on Twitter, Facebook, LinkedIn, and your favorite forums. Big thanks for reading!

#rest api #microservice architecture #api security #security best practices #rest api security #architecture and design

Public ASX100 APIs: The Essential List

We’ve conducted some initial research into the public APIs of the ASX100 because we regularly have conversations about what others are doing with their APIs and what best practices look like. Being able to point to good local examples and explain what is happening in Australia is a key part of this conversation.

Method

The method used for this initial research was to obtain a list of the ASX100 (as of 18 September 2020). Then work through each company looking at the following:

1. Whether the company had a public API: this was found by googling “[company name] API” and “[company name] API developer” and “[company name] developer portal”. Sometimes the company’s website was navigated or searched.
2. Some data points about the API were noted, such as the URL of the portal/documentation and the method they used to publish the API (portal, documentation, web page).
3. Observations were recorded that piqued the interest of the researchers (you will find these below).
4. Other notes were made to support future research.
5. You will find a summary of the data in the infographic below.

Data

With regards to how the APIs are shared:

• Documentation is where just the Swagger/OpenAPI docs are hosted somewhere. e.g. https://api.linkgroup.com/member/docs/index
• Portal is where an interactive portal has been developed. e.g. https://dev.telstra.com/
• The web page is where the company has a single page that isn’t interactive explaining their Public APIs. e.g. https://www.bendigoadelaide.com.au/banking-products-api.asp

#api #api-development #api-analytics #apis #api-integration #api-testing #api-security #api-gateway

What Are Good Traits That Make Great API Product Managers

As more companies realize the benefits of an API-first mindset and treating their APIs as products, there is a growing need for good API product management practices to make a company’s API strategy a reality. However, API product management is a relatively new field with little established knowledge on what is API product management and what a PM should be doing to ensure their API platform is successful.

Many of the current practices of API product management have carried over from other products and platforms like web and mobile, but API products have their own unique set of challenges due to the way they are marketed and used by customers. While it would be rare for a consumer mobile app to have detailed developer docs and a developer relations team, you’ll find these items common among API product-focused companies. A second unique challenge is that APIs are very developer-centric and many times API PMs are engineers themselves. Yet, this can cause an API or developer program to lose empathy for what their customers actually want if good processes are not in place. Just because you’re an engineer, don’t assume your customers will want the same features and use cases that you want.

This guide lays out what is API product management and some of the things you should be doing to be a good product manager.

#api #analytics #apis #product management #api best practices #api platform #api adoption #product managers #api product #api metrics