Tag Archives: owasp

Two-Factor Authentication Considerations

There was a recent article talking about how a very small percentage of google users actually use 2-factor authentication. You can read the full article at http://www.theregister.co.uk/2018/01/17/no_one_uses_two_factor_authentication/

Why 2-Factor

Two-factor authentication, or multi-factor authentication, is a valuable step in the process to protect accounts from unauthorized users. Traditionally, we have relied just on a username/password combination. That process had its own weaknesses that many applications have moved to improve. For example, many sites now require “complex” passwords. Of course, complex is up for debate. But we have seen the minimum password length go up and limitations on using known weak passwords go up. Each year we see lists of the most common passwords to not use, some being 123456 or Password. I hope no one is using these types of passwords. To be honest, I don’t know of any sites I use that would allow this type of password. So many these days require a mix of characters or special characters.


The above controls are meant to help reduce the risk of someone just guessing your password, there are other controls to help try to limit brute forcing techniques. Many accounts offer account lockout after X number of invalid attempts. There are other controls that we also see implemented around protecting the username/password logic. None of these controls help protect against a user reusing passwords on another site that may be compromised. They also do not protect against a user falling for a social engineering attack to trick them into sharing their passwords. To help combat this, many sites will implement a second factor beyond username/password.

The idea of the second factor is that even if you have the username and password, you will not have this other piece of information. In most cases, it is a value that changes every 60 seconds or so, and is delivered over a protected channel. For example, the token used may be sent via SMS, a voice call, or created through a phone application like the Google Authenticator application. So even if the attacker is able to get your password, via a breach, brute force, or just lucky guessing, in theory they would not have access to that second factor.

Why Are People Not Using It?

So why do people not enable the second factor on their Google accounts? Unfortunately, the presentation didn’t appear to explain that, which makes sense since it is difficult to know why people do or do not do certain things. I think there may be a few reasons for it that we will briefly touch on.

First, I think many people just are not aware of enabling the second factor. To be fair, it is sort of buried down in settings that may be difficult to find if you are not really looking for it. If it is not front and center, then there is a much smaller chance people will go seeking it out. To add to the issue, many people really don’t understand what 2-factor authentication means or how it really helps them. Sure, in security we get it, but that doesn’t mean everyone else does. How do we make it more prominent that this is a positive security feature? Many users will already be aware of 2-factor if they use online banking as most of those have started enforcing it.

Many people think that two factor authentication is a burden or it will slow their access down. This is usually not the case unless the application has implemented it poorly. Many sites will allow you to save your computer so you don’t need to enter the 2nd factor every time you access the site. However, it will require it if you access from a different computer.

To complicate things, other applications may not support signing in with 2 factors, like your email client. In these cases, you have to generate an app password which can be very confusing to many users, especially those that are not technically savvy.

There may be a chance that users don’t think they need to protect their email accounts, that it is not sensitive. If you just use email to communicate with friends and receive junk mail, what could be so bad, right? Most people forget that things like password resets are performed using an email account. Having control of an email account provides a lot of control over a lot of things. While it may seem small, email is an important function to protect.

If you are using Gmail, I recommend configuring 2-factor authentication. The following video walks through setting it up using SMS (Although there are other options as well):

Demo- Google 2 factor

If you are developing applications, I recommend looking into providing the option of 2-factor authentication. When you do this, make sure that you are promoting its use in a positive way. If you already have 2-factor with your application, can you run a report to determine what percentage of users are actually using it? If that number is low, what steps can you take to increase them?

Don’t assume that any application is not worthy of the extra security. Many applications are already providing 2-factor and that number will just increase. While we still have the password, we will always be looking for ways to add more protection. When implemented properly, it is simple for the end user, but effective in increasing security. If your user base is not taking advantage of the option, take the time to assess why that is and how it can be improved.

As I was writing this up, I ran into an interesting situation with 2-factor that sparked some more thoughts. When looking to support 2-factor authentication and not using SMS, take careful consideration to the applications you may choose to support. On the Apple App Store alone there are over 200 different authenticator apps available. Some are interchangeable while others are not. This can be another barrier in users choosing to enable 2-factor authentication.

Tinder Mobile Take-Aways

While browsing through the news I noticed an article talking about the Tinder mobile app and a privacy concern. You can read the article at https://www.consumerreports.org/privacy/tinder-app-security-flaws-put-users-privacy-at-risk/. To summarize what is considered the issue is that the mobile application does not transmit the photos that you see using HTTPS. This means that anyone on the same connection can see the traffic and, ultimately, see the photos you are presented. From my understanding, it doesn’t appear the potential attacker can tell who the user is that is viewing these photos as the rest of the traffic is properly using HTTPS.

We have discussed the move to all HTTPS multiple times on this blog and we are seeing a lot of sites making the switch. With web applications it is easy to see if the site is using HTTPS or not with the indicators near the address bar. Of course, these indicators are often confusing to most, but at least we have the ability to see the status. With a mobile application it is much more difficult to tell if data is transmitted using HTTPS or not because there is no visible indicator. Instead, one needs to view the raw traffic or use a web proxy to see how the data is transmitted. This can be misleading to many people because the assumption is that the data is protected because it is hidden under more layers.

In this instance, the ability to see these photos may not be considered that sensitive by many. Assuming that anyone can create an account and see the photos doesn’t make them a secret. People have opted to post their images for others to find them on the network. Of course, level of sensitivity is in the eye of the beholder these days. Another issue that is potentially possible in this situation is that the attacker could manipulate that image traffic to show a different image. This could lead to the end user seeing a different image than the one expected. The usefulness of this could be called into question at any type of large scale.

The take-away here is that when we are building applications we must take care in understanding how we are transmitting all of our data to determine what needs to be protected. As I mentioned, there is already a push to make everything HTTPS all the time. If you have decided not to use HTTPS for your connections, have you documented the reasons? What does your threat model tell you about the risks with that data and its communication. How does that risk line up with your acceptance procedures.

Another interesting tidbit came out of the article mentioned above. In addition to seeing the actual photos, they found it was possible to identify whether or not the end user liked or disliked the photo by comparing the network traffic. The interesting part about this part is that those decisions were encrypted when transmitted. The key point here is that the traffic for each decision was a set size and the sizes were different for like and dislike. By viewing the traffic after seeing a photo, it is possible to determine which ones were liked based on the size of the requests. In this case, it still doesn’t identify the end user that is using the application.

We don’t typically spend a lot of time analyzing the size of the requests we send in the event someone may try to determine what actions we are taking over an encrypted channel. Most of the time these actions are not possible to determine, or the level of effort is way above what is realistic. The easy solution would be to make sure all traffic was encrypted and we wouldn’t be able to know what images were liked or disliked. Maybe it would be possible to still see the difference, but with no way to tie it to specific images. The other option is to attempt to pad the requests so that they are all the same size. This would be for highly sensitive systems as the complexity may not be worth the benefit.

Of course, all of this is based on the attacker being on the same network as the end user so they can intercept or view the traffic in the first place. In the case of a public place, it might just be easier to hover over your shoulder and watch you use the app then intercept the traffic and guess at who is using it.

Both of these topics are good conversation starters within your organization. They help us realize that even just one request that doesn’t use HTTPS may be seen and could raise an issue. It also helps us to see that sometimes even encrypted data can be determined, but that doesn’t mean it is a high risk. Each situation is different and should be properly analyzed to determine the risk it creates for the company and the organization.

Password Storage Overview

Start reading the news and you are bound to read about another data breach involving user credentials. Whether you get any details about how the passwords (that were stolen) were stored, we can assume that in many of these cases that they were not well protected. Maybe they were stored in clear text (no, it can’t be true), or use weak hashes. Passwords hold the key to our access to most applications. What are you doing to help protect them?

First, lets just start with recommending that the users don’t re-use their passwords, ever. Don’t share them across applications, just don’t. Pick a password manager or some other mechanism to allow unique passwords for each application. That doesn’t mean using summer2015 for one site and summer2016 for another. Don’t have them relatable in any way.

Now that we have that out of the way, how can the applications better protect their passwords? Lets look at the storage options:

  • Clear Text
  • Encrypted
  • Hashed

Clear Text

While this may seem harmless, since the data is stored in your highly secured, super secret database, it is looked down upon. As a developer, it may seem easy, throwing a prototype together to have the password in plain text. You don’t have to worry if your storage algorithm is working properly, or if you forget your password as you are building up the feature set. It is right there in the database. While convenience may be there, this is just a bad idea. Remember that passwords should only be known by the user that created it. They should also not be shared. Take an unauthorized breach out of the picture for a moment, the password could still be viewed by certain admins of the system or database administrators. Bring a breach back into the picture, now the passwords can be easily seen by anyone with no effort. There are no excuses for storing passwords as plain text. By now, you should know better.


Another option commonly seen is the use of reversible encryption. With encryption, the data is unreadable, but with the right keys, it is possible to read the actual data. In this case, the real password. The encryption algorithm used can make a difference on how long it takes to reverse it if it falls into the wrong hands. Like the clear text storage, the passwords are still left exposed to certain individuals that have access to the encrypt/decrypt routines. There shouldn’t be a need to ever see the plain text version of the password again, so why store it so that it can be decrypted? Again, not recommended for strong, secure password storage.


Hashing is process of transforming the data so that it is un-readable and not reversible. Unlike when the data is encrypted, a hashed password cannot be transformed back to the original value. To crack a hashed password you would typically run password guesses through the same hashing algorithm looking for the same result. If you find a plaintext value that creates the same hash, then you have found the password.

Depending on the hashing algorithm you use, it can be easy or very difficult to identify the password. Using MD5 with no salt is typically very easy to crack. Using a strong salt and SHA-512 may be a lot harder to crack. Using PBKDF or bcrypt, which include work factors, can be extremely difficult to crack. As you can see, not all hashing algorithms are created equally.

The Salt

The salt, mentioned earlier, is an important factor in hashing passwords to create uniqueness. First, a unique, randomly generated salt will make sure that if two users have the same password, they will not have the same hash. The salt is appended to the password, to basically create a new password, before the data is hashed. Second, a unique salt makes it more difficult for people cracking passwords because they have to regenerate hashes for all their password lists now using a new salt for each user. Generating a database of hashes based on a dictionary of passwords is known as creating a rainbow table. Makes for quicker lookups of hashes. The unique salt negates the rainbow table already generated and requires creating a new one (which can cost a lot of time).

The salt should be unique for each user, randomly generated, and of sufficient length.

The Algorithm

As I mentioned earlier, using MD5, probably not a good idea. Take the time to do some research on hashing algorithms to see which ones have collision issues or have been considered weak. SHA256 or SHA512 are better choices, obviously going with the strongest first if it is supported. As time goes on and computers get faster, algorithms start to weaken. Do your research.

Work Factor
The new standard being implemented and recommended is adding not only a salt, but a work factor to the process of hashing the password. This is done currently by using PBKDF, BCRYPT, or SCRYPT. The work factor slows the process of the hashing down. Keep in mind that hashing algorithms are fast by nature. In the example of PBKDF, iterations are added. That means that instead of just appending a salt to the password and hashing it once, it gets hashed 1,000 or 10,000 times. These iterations increase the work factor and can slow down the ability for an attacker to loop through millions of potential passwords. When comparing BCRYPT to SCRYPT, the big difference is where the work factor is. For BCRYPT, the work factor effects the CPU. For SCRYPT, the work factor is memory based.

Moving forward, you will start to see a lot more of PBKDF, BCRYPT and SCRYPT for password storage. If you are implementing these, test them out with different work factors to see what works for your environment. If 10,000 iterations is too slow on the login page, try decreasing it a little. Keep in mind that comparing a hash to verify a user’s credentials should not be happening very often, so the hit is typically on initial login only.


Password storage is very important in any application. Take a moment to look at how you are doing this in your apps and spread the word to help educate others on more secure ways of storing passwords. Not only could storing them incorrectly be embarrassing or harmful if they are breached, it could lead to issues with different regulatory requirements out there. For more information on storing passwords, check out OWASP’s Password Storage Cheat Sheet.

Keep in mind that if users use very common passwords, even with a strong algorithm, they can be cracked rather quickly. This is because a list of common passwords will be tried first. Creating the hash of the top 1000 passwords won’t take nearly as long as a list of a million or billion passwords.