Autumn  Blick

Autumn Blick

1601385115

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

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Buddha Community

API Security Weekly: Issue #101

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

Autumn  Blick

Autumn Blick

1601385115

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

API Security Weekly: Issue #90

This week, we take a look at how Twitter API erroneously allowed browsers to cache sensitive data, and how skimmers have found a way to use Google Analytics APIs to get their hands on credit card data. Plus, there is a live demo of API hacking, as well as a new book on API security.

Vulnerability: Twitter

HTTP headers can play an important role in API security, like the case with Twitter API shows. The header cache-control:no-store had not been set on the API, which meant that the data that this API returned to the web page was stored in the browser cache.

Unfortunately, this particular API was for Twitter’s advertisers’ portal ads.twitter.com and their analytics.twitter.com site, and the returned data did include sensitive billing information. The flaw could not be exploited remotely, but someone with a physical access to the computer a user used could gain access to the information, meaning that Twitter still had to classify this as a Data Security Incident.

Twitter has since fixed this vulnerability.

Attack Vector: Google Analytics APIs

Attackers use skimmers on e-commerce sites to inject their code (for example, JavaScript) to intercept credit card information on purchases. This is the first leg of the journey: attackers still need a way to ship that stolen data to their servers, and lots of sites are using Content Security Policy (CSP) to prevent that. With CSP, site owners effectively prohibit any API calls outside of their own. Sounds good, right?

Unfortunately, as Amir Shaked from PerimeterX demonstrates, CSP is not really compatible with Google Analytics APIs. Google Analytics is widely used on websites to gather statistics and data for business decisions, and thus its domain is typically placed in the allowlist of the CSP.

In a way, this opens a backdoor (or open window, as Shaked puts it) to CSP. All attackers need to do to get that stolen data from the skimmer is to just call Google Analytics APIs and ship the data to their Google Analytics account. The domain of this call is identical to any other Google Analytics call, only the tag parameter is different. This it not enough for CSP to use as a discriminator, so the call sails through no problem.

This is a cautionary tale to keep in mind whenever a multitenant 3rd-party API is in use.

Book: API Security in Action

Neil Madden has just finished his book “API Security in Action”, published by Manning. This was one of the books in their early access program (MEAP) that allowed readers to get it chapter by chapter as released by the author. Now you can get full content, and pre-order your hard-copy if you want.

Here’s the quick abstract of the book:

“API Security in Action shows you how to create secure web APIs that you can confidently share with your business partners and expose for public usage. Security expert Neil Madden takes you under the hood of modern API security concepts, including token-based authentication for flexible multi-user security, bootstrapping a secure environment in a Kubernetes microservices architecture, and using lightweight cryptography to secure an IoT device.”

Madden goes into great detail about different authentication mechanisms used in REST APIs and also covers modern API-based architectures, including microservice and IoT deployments.

As a cherry on top, you can get 42% off the list price when you use the coupon code 42Crunch40 at checkout!

Video: API Hacking Demo

Live, practical demos are always exciting. Katie Paxton-Fear has posted a recording of her live API Hacking Demo that is definitely worth checking out.

In her demo, she uses Burp to discover APIs on a server, enumerates paths, discovers IDOR/BOLA vulnerabilities, takes over an account, and concludes by escalating her privileges.

To provide practical examples, Paxton-Fear also shows what these bugs look like in her sample application code.

#security #api #cybersecurity #apis #api security #api vulnerabilities #google analytics api #attack vector

Flo  D'Amore

Flo D'Amore

1602678734

API Security Weekly: Issue #104

This week, we check out the recent API-related vulnerabilities at Twitter and Grandstream Networks, the newly added support for mutual TLS (mTLS) in AWS API Gateway, and the API security episode in the Application Security Podcast.

Vulnerability: Twitter

A misconfiguration in the Twitter developer portal caused browsers to cache API keys, account access tokens, and account secrets.

It is highly unlikely that the vulnerability has been exploited. Not only would attackers have to had known about the vulnerability, they would also have needed physical access to the computers of their victims. That being said, this flaw could potentially had leaked these secrets on shared computers.

To avoid issues like this one, make sure you never cache any sensitive data on client-side.

Vulnerability: Grandstream Networks

Grandstream Networks is a global provider for IP video and voice services as well as WiFi and related services and equipment, and they operate in over 150 countries around the world.

The about 5 million Grandstream devices and services are managed in their GWN.Cloud management platform. Researchers from Pen Test Partners took a look at the platform and found vulnerabilities in the APIs behind it.

The web UI used an API to change device and network settings. When a user applied chang

#security #api #cybersecurity #apis #twitter #podcast #api security #newsletter #api vulnerabilities #aws api gateway

API Security Weekly: Issue #90

This week, we take a look at how Twitter API erroneously allowed browsers to cache sensitive data, and how skimmers have found a way to use Google Analytics APIs to get their hands on credit card data. Plus, there is a live demo of API hacking, as well as a new book on API security.

Vulnerability: Twitter

HTTP headers can play an important role in API security, like the case with Twitter API shows. The header cache-control:no-store had not been set on the API, which meant that the data that this API returned to the web page was stored in the browser cache.

Unfortunately, this particular API was for Twitter’s advertisers’ portal ads.twitter.com and their analytics.twitter.com site, and the returned data did include sensitive billing information. The flaw could not be exploited remotely, but someone with a physical access to the computer a user used could gain access to the information, meaning that Twitter still had to classify this as a Data Security Incident.

Twitter has since fixed this vulnerability.

Attack Vector: Google Analytics APIs

Attackers use skimmers on e-commerce sites to inject their code (for example, JavaScript) to intercept credit card information on purchases. This is the first leg of the journey: attackers still need a way to ship that stolen data to their servers, and lots of sites are using Content Security Policy (CSP) to prevent that. With CSP, site owners effectively prohibit any API calls outside of their own. Sounds good, right?

Unfortunately, as Amir Shaked from PerimeterX demonstrates, CSP is not really compatible with Google Analytics APIs. Google Analytics is widely used on websites to gather statistics and data for business decisions, and thus its domain is typically placed in the allowlist of the CSP.

In a way, this opens a backdoor (or open window, as Shaked puts it) to CSP. All attackers need to do to get that stolen data from the skimmer is to just call Google Analytics APIs and ship the data to their Google Analytics account. The domain of this call is identical to any other Google Analytics call, only the tag parameter is different. This it not enough for CSP to use as a discriminator, so the call sails through no problem.

This is a cautionary tale to keep in mind whenever a multitenant 3rd-party API is in use.

Book: API Security in Action

Neil Madden has just finished his book “API Security in Action”, published by Manning. This was one of the books in their early access program (MEAP) that allowed readers to get it chapter by chapter as released by the author. Now you can get full content, and pre-order your hard-copy if you want.

Here’s the quick abstract of the book:

“API Security in Action shows you how to create secure web APIs that you can confidently share with your business partners and expose for public usage. Security expert Neil Madden takes you under the hood of modern API security concepts, including token-based authentication for flexible multi-user security, bootstrapping a secure environment in a Kubernetes microservices architecture, and using lightweight cryptography to secure an IoT device.”

Madden goes into great detail about different authentication mechanisms used in REST APIs and also covers modern API-based architectures, including microservice and IoT deployments.

As a cherry on top, you can get 42% off the list price when you use the coupon code 42Crunch40 at checkout!

Video: API Hacking Demo

Live, practical demos are always exciting. Katie Paxton-Fear has posted a recording of her live API Hacking Demo that is definitely worth checking out.

In her demo, she uses Burp to discover APIs on a server, enumerates paths, discovers IDOR/BOLA vulnerabilities, takes over an account, and concludes by escalating her privileges.

To provide practical examples, Paxton-Fear also shows what these bugs look like in her sample application code.

#security #api #cybersecurity #apis #api security #api vulnerabilities #google analytics api #attack vector