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MFA page grammatical fixes #1017

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Co-authored-by: Jonah Aragon <jonah@triplebit.net>
Co-authored-by: Daniel Gray <dng@disroot.org>
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@ -10,7 +10,7 @@ icon: 'material/two-factor-authentication'
![YubiKeys](assets/img/multi-factor-authentication/yubikey.png)
The **YubiKeys** are among the most popular security keys. Some YubiKey models have a wide range of features such as: [Universal 2nd Factor (U2F)](https://en.wikipedia.org/wiki/Universal_2nd_Factor), [FIDO2 WebAuthn](https://en.wikipedia.org/wiki/WebAuthn), [Yubico OTP](https://developers.yubico.com/OTP/), [PIV](https://en.wikipedia.org/wiki/FIPS_201), [OpenPGP](https://developers.yubico.com/PGP/), [TOTP and HOTP](https://developers.yubico.com/OATH/) authentication.
The **YubiKeys** are among the most popular security keys. Some YubiKey models have a wide range of features such as: [Universal 2nd Factor (U2F)](https://en.wikipedia.org/wiki/Universal_2nd_Factor), [FIDO2 and WebAuthn](security/multi-factor-authentication.md#fido-fast-identity-online), [Yubico OTP](security/multi-factor-authentication.md#yubico-otp), [Personal Identity Verification (PIV)](https://developers.yubico.com/PIV), [OpenPGP](https://developers.yubico.com/PGP/), [TOTP and HOTP](https://developers.yubico.com/OATH) authentication.
One of the benefits of the YubiKey is that one key can do almost everything (YubiKey 5), you could expect from a hardware security key. We do encourage you to take the [quiz](https://www.yubico.com/quiz/) before purchasing in order to make sure you make the right choice.
@ -31,7 +31,7 @@ For models which support HOTP and TOTP, there are 2 slots in the OTP interface w
![Nitrokey](assets/img/multi-factor-authentication/nitrokey.jpg){ align=right }
**Nitrokey** has a security key capable of [FIDO2 WebAuthn](https://en.wikipedia.org/wiki/WebAuthn) called the **Nitrokey FIDO2**. For PGP support, you need to purchase one of their other keys such as the **Nitrokey Start**, **Nitrokey Pro 2** or the **Nitrokey Storage 2**.
**Nitrokey** has a security key capable of [FIDO2 and WebAuthn](security/multi-factor-authentication.md#fido-fast-identity-online) called the **Nitrokey FIDO2**. For PGP support, you need to purchase one of their other keys such as the **Nitrokey Start**, **Nitrokey Pro 2** or the **Nitrokey Storage 2**.
[Visit nitrokey.com](https://www.nitrokey.com){ .md-button .md-button--primary } [Privacy Policy](https://www.nitrokey.com/data-privacy-policy){ .md-button }

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@ -2,51 +2,53 @@
title: "Multi-factor Authentication"
icon: 'material/two-factor-authentication'
---
**Multi-factor authentication** (MFA, or 2FA) is a security mechanism that requires additional steps beyond entering your username (or email) and password. The most common method are time limited codes you might receive from an SMS or app.
**Multi-factor authentication** (MFA, or 2FA) is a security mechanism that requires additional steps beyond entering your username (or email) and password. The most common method is time limited codes you might receive from an SMS or app.
The idea behind MFA is that even if a hacker (or adversary) is able to figure out your password (something you *know*), they will still need a device you own like your phone (something you *have*) in order to generate the code needed to log in to your account. MFA methods vary in security based on this premise: The more difficult it is for an attacker to gain access to your MFA method, the better. Examples of MFA methods (from weakest to strongest) include [SMS codes](https://en.wikipedia.org/wiki/One-time_password#SMS), email codes, app push notifications, [Time-based One-time Passwords (TOTP)](https://en.wikipedia.org/wiki/Time-based_one-time_password), Yubico OTP, and [FIDO2](https://en.wikipedia.org/wiki/FIDO2_Project) / [U2F](https://en.wikipedia.org/wiki/Universal_2nd_Factor).
Normally, if a hacker (or adversary) is able to figure out your password then they’d gain access to the account that password belongs to. An account with MFA forces the hacker to have both the password (something you *know*) and a device that you own (something you *have*), like your phone.
MFA methods vary in security, but are based on the premise that the more difficult it is for an attacker to gain access to your MFA method, the better. Examples of MFA methods (from weakest to strongest) include [SMS, Email codes](#sms-or-email-mfa), app push notifications, [Time-based One-time Passwords (TOTP)](#time-based-one-time-password-totp), [Yubico OTP](#yubico-otp), and [FIDO (Fast IDentity Online)](#fido-fast-identity-online).
## MFA Method Comparison
### SMS or Email MFA
Receiving codes either from **SMS** or **email** are one of the weaker ways to secure your accounts with MFA. Obtaining a code by email or SMS takes away from the "something you *have*" idea, because there are a variety of ways a hacker could [take over your phone number](https://en.wikipedia.org/wiki/SIM_swap_scam) or gain access to your email without having physical access to any of your devices at all. If an unauthorized person gained access to your email, they would be able to use that access to both reset your password and receive the authentication code, giving them full access to your account.
Receiving codes either from [**SMS**](https://en.wikipedia.org/wiki/One-time_password#SMS) or **email** are one of the weaker ways to secure your accounts with MFA. Obtaining a code by email or SMS takes away from the "something you *have*" idea, because there are a variety of ways a hacker could [take over your phone number](https://en.wikipedia.org/wiki/SIM_swap_scam) or gain access to your email without having physical access to any of your devices at all. If an unauthorized person gained access to your email, they would be able to use that access to both reset your password and receive the authentication code, giving them full access to your account.
### Push Notifications
**Push Notifications** take the form of a message being sent to an app on your phone asking you to confirm new account logins. This method is a lot better than SMS or email, since an attacker typically wouldn't be able to get these push notifications without having an already logged-in device, which means they would need to compromise one of your other devices first.
**Push notifications** take the form of a message being sent to an app on your phone asking you to confirm new account logins. This method is a lot better than SMS or email, since an attacker typically wouldn't be able to get these push notifications without having an already logged-in device, which means they would need to compromise one of your other devices first.
We all make mistakes, and there is the risk that a user may accept the login attempt by accident. Push notification login authorizations are typically sent to *all* your devices at once, widening the availability of the MFA code if you have many devices.
The security of push notification MFA is dependent on both the quality of the app, the server component and the trust of the developer who produces it. Installing an app may also require you to accept invasive privileges that grant access to other data on your device. An individual app also requires that you have a specific app for each service which may not require a password to open unlike a good [Time-based One-time Password (TOTP)](#time-based-one-time-password-totp) app.
The security of push notification MFA is dependent on both the quality of the app, the server component and the trust of the developer who produces it. Installing an app may also require you to accept invasive privileges that grant access to other data on your device. An individual app also requires that you have a specific app for each service which may not require a password to open, unlike a good [Time-based One-time Password (TOTP)](#time-based-one-time-password-totp) app.
### Time-based One-time Password (TOTP)
**TOTP** is one of the most commons form of MFA available. When a user sets up TOTP they are generally required to scan a [QR Code](https://en.wikipedia.org/wiki/QR_code) which establishes a "shared secret" with the service that they intend to use. The shared secret is secured inside of the authenticator app's data, and is sometimes protected by a password.
**TOTP** is one of the most commons form of MFA available. When a user sets up TOTP they are generally required to scan a [QR Code](https://en.wikipedia.org/wiki/QR_code) which establishes a "[shared secret](https://en.wikipedia.org/wiki/Shared_secret)" with the service that they intend to use. The shared secret is secured inside of the authenticator app's data, and is sometimes protected by a password.
The time-limited code is then derived from the shared secret and the current time. As the code is only valid for a short time, without access to the shared secret an adversary cannot generate new codes.
If you have a hardware security key with TOTP support (such as a YubiKey with [Yubico Authenticator](https://www.yubico.com/products/yubico-authenticator/)), we recommend that you store your "shared secrets" on the hardware. Hardware such as the YubiKey was developed with making the "shared secret" difficult to extract and copy. A YubiKey is also not connected to the Internet, unlike a phone with a TOTP app.
If you have a hardware security key with TOTP support (such as a YubiKey with [Yubico Authenticator](https://www.yubico.com/products/yubico-authenticator/)), we recommend that you store your "shared secrets" on the hardware. Hardware such as the YubiKey was developed with the intention of making the "shared secret" difficult to extract and copy. A YubiKey is also not connected to the Internet, unlike a phone with a TOTP app.
Unlike [FIDO2 / U2F](#fido2-u2f), TOTP offers no protection against [phishing](https://en.wikipedia.org/wiki/Phishing) or reuse attacks. If an adversary obtains a valid code from you they may use it as many times as they like until it expires (generally 60 seconds).
Unlike [WebAuthn](#fido-fast-identity-online), TOTP offers no protection against [phishing](https://en.wikipedia.org/wiki/Phishing) or reuse attacks. If an adversary obtains a valid code from you they may use it as many times as they like until it expires (generally 60 seconds).
An adversary could set up a website to imitate an official service in an attempt to trick you into giving out your username, password and current TOTP code. If the adversary then uses those recorded credentials they may be able to log into the real service and hijack the account.
Although not perfect it is secure enough for most people, and when [Hardware Security Keys](#hardware-security-keys) are not supported TOTP with [Authenticator Apps](#authenticator-apps) are still a good option.
Although not perfect, TOTP is secure enough for most people, and when [hardware security keys](/multi-factor-authentication/#hardware-security-keys) are not supported [authenticator apps](/multi-factor-authentication/#authenticator-apps) are still a good option.
### Hardware security keys
The YubiKey stores data on a tamper-resistant solid-state chip which is [impossible to access](https://security.stackexchange.com/a/245772) non-destructively without a expensive processes and a forensics laboratory.
As these keys are generally multi-function and provide a number of methods to authenticate we discuss below the most common ones.
These keys are generally multi-function and provide a number of methods to authenticate. Below are the most common ones.
#### Yubico OTP
Yubico OTP is an authentication protocol typically implemented in hardware security keys. When a user decides to use Yubico OTP, the key will generate a public ID, private ID, and a Secret Key which is then uploaded to the Yubico OTP server.
When logging into a website all a user needs to do is to physically touch the security key. The security key will emulate a keyboard and print out a one-time password into the password field.
When logging into a website, all a user needs to do is to physically touch the security key. The security key will emulate a keyboard and print out a one-time password into the password field.
The service will then forward the one-time password to the Yubico OTP server for validation. A counter is incremented both on the key and Yubico's validation server. The OTP can only only be used once and when a successful authentication occurs the counter is increased which prevents reuse of the OTP. Yubico does provide a [detailed document](https://developers.yubico.com/OTP/OTPs_Explained.html) about the process.
The service will then forward the one-time password to the Yubico OTP server for validation. A counter is incremented both on the key and Yubico's validation server. The OTP can only only be used once, and when a successful authentication occurs the counter is increased which prevents reuse of the OTP. Yubico provides a [detailed document](https://developers.yubico.com/OTP/OTPs_Explained.html) about the process.
<figure markdown>
![Yubico OTP](../assets/img/multi-factor-authentication/yubico-otp.png)
@ -54,15 +56,23 @@ The service will then forward the one-time password to the Yubico OTP server for
There are some benefits and disadvantages to using Yubico OTP when compared to [TOTP](#time-based-one-time-password-totp).
The Yubico validation server is a cloud based service, and users do place trust in Yubico that they are storing data securely and not profiling users. The public ID associated with Yubico OTP is reused on every website and could be another avenue for third parties to profile the user. Like [TOTP](#time-based-one-time-password-totp), Yubico OTP does not provide phishing resistance.
The Yubico validation server is a cloud based service, and users place trust in Yubico that they are storing data securely and not profiling users. The public ID associated with Yubico OTP is reused on every website and could be another avenue for third parties to profile the user. Like [TOTP](#time-based-one-time-password-totp), Yubico OTP does not provide phishing resistance.
If your threat model requires you to have different identities on different websites, **do not** use Yubico OTP with the same hardware security key across those websites as public ID is unique to each security key.
#### FIDO2 / U2F
#### FIDO (Fast IDentity Online)
[FIDO2](https://en.wikipedia.org/wiki/FIDO2_Project) / [**U2F**](https://en.wikipedia.org/wiki/Universal_2nd_Factor) is the most secure and private form of second factor authentication. While the user experience is similar to Yubico OTP, the key does not print out a one-time password and validate with a third party server. Instead FIDO2 (and U2F) use [public key cryptography](https://en.wikipedia.org/wiki/Public-key_cryptography) for authentication.
[FIDO](https://en.wikipedia.org/wiki/FIDO_Alliance) includes a number of standards, first there was [U2F](https://en.wikipedia.org/wiki/Universal_2nd_Factor) and then later [FIDO2](https://en.wikipedia.org/wiki/FIDO2_Project) with the web standard [WebAuthn](https://en.wikipedia.org/wiki/WebAuthn).
When a user creates an account the public key is sent to the service. When the user logs in the service will require the user to "sign" some data with their private key. The benefit of this is that no password data is ever stored by the service, so there is nothing for an adversary to steal.
U2F and FIDO2 refer to the [CTAP (Client to Authenticator Protocol)](https://en.wikipedia.org/wiki/Client_to_Authenticator_Protocol), which is the protocol between the security key and the computer, such as a laptop or phone. It complements WebAuthn which is the component used to authenticate with the "Relying Party", the website, you're trying to log in on.
WebAuthn is the most secure and private form of second factor authentication. While the user experience is similar to Yubico OTP, the key does not print out a one-time password and validate with a third party server. Instead it uses [public key cryptography](https://en.wikipedia.org/wiki/Public-key_cryptography) for authentication.
<figure markdown>
![FIDO](../assets/img/multi-factor-authentication/fido.png)
</figure>
When a user creates an account the public key is sent to the service, then when the user logs in, the service will require the user to "sign" some data with their private key. The benefit of this is that no password data is ever stored by the service, so there is nothing for an adversary to steal.
This presentation discusses the history of password authentication, the pitfalls (such as password reuse), and discussion of FIDO2 and [WebAuthn](https://webauthn.guide) standards.
@ -74,43 +84,43 @@ This presentation discusses the history of password authentication, the pitfalls
allowfullscreen>
</iframe>
FIDO2 / U2F has superior security and privacy properties when compared to any MFA methods.
FIDO2 and WebAuthn have superior security and privacy properties when compared to any MFA methods.
Typically for web services it is used with [WebAuthn](https://en.wikipedia.org/wiki/WebAuthn) which is a part of the [W3C recommendations](https://en.wikipedia.org/wiki/World_Wide_Web_Consortium#W3C_recommendation_(REC)). It uses public key authentication and is more secure than shared secrets used in Yubico OTP and TOTP methods, as it includes the origin name (usually, the domain name) during authentication. Attestation is provided to protect the user from phishing as it helps them to determine that they are using the authentic service and not a fake copy.
Typically for web services it is used with WebAuthn which is a part of the [W3C recommendations](https://en.wikipedia.org/wiki/World_Wide_Web_Consortium#W3C_recommendation_(REC)). It uses public key authentication and is more secure than shared secrets used in Yubico OTP and TOTP methods, as it includes the origin name (usually, the domain name) during authentication. Attestation is provided to protect the user from phishing, as it helps them to determine that they are using the authentic service and not a fake copy.
WebAuthn does not use any public ID, so the key is **not** identifiable across different websites like Yubico OTP. It also does not use any third party cloud server for authentication. All communication is completed between the key and the website the user is logging into. FIDO2 / U2F also uses a counter which is incremented upon use in order to prevent session reuse.
Unlike Yubico OTP, WebAuthn does not use any public ID, so the key is **not** identifiable across different websites. It also does not use any third party cloud server for authentication. All communication is completed between the key and the website the user is logging into. FIDO also uses a counter which is incremented upon use in order to prevent session reuse and cloned keys.
If a website or service supports FIDO2 / U2F for the authentication, it is highly recommended that you use it over any other form of MFA.
If a website or service supports WebAuthn for the authentication, it is highly recommended that you use it over any other form of MFA.
## General Recommendations
We have these general recommendations:
### Which method to use?
### Which method should I use?
When configuring your MFA method, keep in mind that it is only as secure as your weakest authentication method you use. This means it is important that you only use the best MFA method available. For instance, if you are already using TOTP, you should disable email and SMS MFA. If you are already using FIDO2 / U2F, you should not be using Yubico OTP or TOTP on your account.
When configuring your MFA method, keep in mind that it is only as secure as your weakest authentication method you use. This means it is important that you only use the best MFA method available. For instance, if you are already using TOTP, you should disable email and SMS MFA. If you are already using FIDO2/WebAuthn, you should not be using Yubico OTP or TOTP on your account.
### Backups
You should always have backups for your MFA method. Hardware security keys can get lost, stolen, or simply stop working over time. It is recommended that you have a pair of hardware security keys with the same access to your accounts instead of just one.
When using TOTP with an authenticator app, be sure to back up your recovery keys, the app itself, or copy the "shared secrets" to another instance of the app on a different phone or into an encrypted container (e.g. [VeraCrypt](../encryption.md#veracrypt)).
When using TOTP with an authenticator app, be sure to back up your recovery keys or the app itself, or copy the "shared secrets" to another instance of the app on a different phone or to an encrypted container (e.g [VeraCrypt](../encryption.md#veracrypt)).
### Initial setup
When buying a security key, it is important that you change the default credentials, setup password protection for the key, and enable touch confirmation if your key supports such feature. Products such as the [YubiKey](#yubikey) have multiple interfaces with seperate credentials for each one of them, so you should go over each interface and set up protection as well.
When buying a security key, it is important that you change the default credentials, setup password protection for the key, and enable touch confirmation if your key supports it. Products such as the [YubiKey](#yubico-otp) have multiple interfaces with seperate credentials for each one of them, so you should go over each interface and set up protection as well.
### Email and SMS
If you have to use email for MFA, make sure that the email account itself is secured with a proper MFA method.
If you use SMS MFA, use a carrier who will not switch your phone number to a new SIM card without account access or use a dedicated VOIP number from a provider with similar security to avoid a [SIM swap](https://en.wikipedia.org/wiki/SIM_swap_scam) attack.
If you use SMS MFA, use a carrier who will not switch your phone number to a new SIM card without account access, or use a dedicated VOIP number from a provider with similar security to avoid a [SIM swap](https://en.wikipedia.org/wiki/SIM_swap_scam) attack.
[MFA tools we recommend](../multi-factor-authentication.md){ .md-button }
## More places to setup MFA
Beyond just securing your website logins, multi-factor authentication can be used to secure your local logins, ssh keys or even password databases as well.
Beyond just securing your website logins, multi-factor authentication can be used to secure your local logins, SSH keys or even password databases as well.
### Windows
@ -135,11 +145,11 @@ The command will prevent an adversary from bypassing MFA when the computer boots
!!! warning
If the [hostname](https://en.wikipedia.org/wiki/Hostname) of your system changes (such as due to DHCP), you would be unable to login. It is vital that you setup a proper hostname for your computer before following this guide.
The `pam_u2f` module on Linux can provide two factor authentication for user login on most popular Linux distributions. If you have a hardware security key that supports U2F, you can set up MFA authentication for your login. Yubico has a guide [Ubuntu Linux Login Guide - U2F](https://support.yubico.com/hc/en-us/articles/360016649099-Ubuntu-Linux-Login-Guide-U2F) which should work on any distribution. The package manager commands such as "apt-get" and package names may however differ. This guide does **not** apply to Qubes OS.
The `pam_u2f` module on Linux can provide two factor authentication for user login on most popular Linux distributions. If you have a hardware security key that supports U2F, you can set up MFA authentication for your login. Yubico has a guide [Ubuntu Linux Login Guide - U2F](https://support.yubico.com/hc/en-us/articles/360016649099-Ubuntu-Linux-Login-Guide-U2F) which should work on any distribution. The package manager commands—such as "apt-get"—and package names may however differ. This guide does **not** apply to Qubes OS.
### Qubes OS
Qubes OS has support for Challenge-Response authentication with YubiKeys. If you have a YubiKey with Challenge-Response authentication support, take a look at the Qubes OS' [YubiKey documentation](https://www.qubes-os.org/doc/yubikey/) if you want to set up MFA on Qubes OS.
Qubes OS has support for Challenge-Response authentication with YubiKeys. If you have a YubiKey with Challenge-Response authentication support, take a look at the Qubes OS [YubiKey documentation](https://www.qubes-os.org/doc/yubikey/) if you want to set up MFA on Qubes OS.
### SSH
@ -149,7 +159,7 @@ SSH MFA could be set up using multiple different authentication methods that are
#### Time-based One-time Password (TOTP)
SSH MFA can also be set up using TOTP and DigitalOcean has provided a tutorial [How To Set Up Multi-Factor Authentication for SSH on Ubuntu 20.04](https://www.digitalocean.com/community/tutorials/how-to-set-up-multi-factor-authentication-for-ssh-on-ubuntu-20-04). Most things should be the same regardless of distribution, however the package manager commands such as "apt-get" and package names may differ.
SSH MFA can also be set up using TOTP. DigitalOcean has provided a tutorial [How To Set Up Multi-Factor Authentication for SSH on Ubuntu 20.04](https://www.digitalocean.com/community/tutorials/how-to-set-up-multi-factor-authentication-for-ssh-on-ubuntu-20-04). Most things should be the same regardless of distribution, however the package manager commands—such as "apt-get"—and package names may differ.
### KeePass (and KeePassXC)