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There are two possible scenarios here. The first is that your phone is not compromised. In this case there is no other app trying to steal your bank's authenti

There are two possible scenarios here. The first is that your phone is not compromised. In this case there is no other app trying to steal your bank's authentication token. This is true regardless of which OS you use or whether you have magisk installed or what other code you put on your phone that isn't trying to steal your bank's authentication token. The second is that your phone is compromised. Then what prevents the device from capturing your bank credentials is the same as if you use a compromised phone running Google Android: Nothing. If you enter your bank credentials into a compromised phone, the attacker gets them. Attestation can't prevent this because the phone is compromised, so the login screen isn't from a bank app that requires attestation, it's from a scam app which is exfiltrating your credentials.

charcircuit 1y ago
>Nothing This is far from the truth assuming by compromised you mean that the user has installed a malicous app. Android has proper sandboxing which means that other apps can't read the token owned by the bank app. This is part of the Android security model and attestation is evidence that the Android security model is being enforced. Phishing apps are different from an app that steals existing authentication tokens on the device.
- fc417fc802 1y ago
  You aren't responding to the scenario that was posed. You're assuming an isolated compromised app on an otherwise clean device. GP is assuming a compromised device. Of course attestation does nothing to improve the "single compromised app" case since (assuming Android) that goes nowhere either way. The only thing attestation does is meddle in end user affairs.
  - charcircuit 1y ago
    >if the phone isn't compromised then the owner having root isn't a security problem The scenario is the phone isn't compromised. Having root means you, or an app you run can bypass the security protecting the authentication token.
    - fc417fc802 1y ago
      And now you're being intentionally difficult. Please interpret things in the most plausible manner. Beyond common decency, it's part of the site guidelines. By "not compromised" GP clearly meant a scenario where no malicious apps are present. I agree that's a serious omission. I responded to your scenario (a nonzero number of malicious apps) in my earlier comment. Any Android device will defend against that regardless of the presence of attestation. Any non-android device can still use online banking and thus attestation doesn't appear to accomplish anything legitimate. Building out proper support for hardware tokens would provide superior security in approximately all cases. The specific "root on android" scenario isn't generally a concern. Typical implementations require explicitly granting the capability to a given app. A malicious app can't gain it without fooling the user, at which point it could more easily phish the credentials and possibly even proxy an entire session.
      - charcircuit 1y ago
        >Please interpret things in the most plausible manner. Your suggestion is not plausible as every security feature has 0 security value if there is nothing malicous. It would be like someone saying that antivirus is useless because if someone doesn't have a virus then it doesn't do anything. >Any Android device will defend against that regardless of the presence of attestation. Rooted android devices can be set up in a way that malicous apps can gain root and then read it. >Any non-android device can still use online banking But this comes with a different risk profile. A bank can reduce risk for a subset of their customers. >Building out proper support for hardware tokens would provide superior security in approximately all cases. I think usually the hardware token gains you access to an authentication token. You don't sign every request you are making with a hardware only key. >Typical implementations require explicitly granting the capability to a given app. And the majority of users have no clue what an app is able to do. If root is given to it then it can do anything. This is in contrast to when root isn't available and users are protected by the sandbox the app is in.
        AnthonyMouse 1y ago
        > It would be like someone saying that antivirus is useless because if someone doesn't have a virus then it doesn't do anything. Suppose you have an "antivirus" program that works like this: The system makes a list of every program that runs as root during boot and then at the end of boot the antivirus program checks the list for unexpected programs and if it finds any it displays an error and refuses to display the login prompt to prevent the user from typing their password into a compromised device. That "antivirus" system is useless, because if a malicious program did run as root during boot then it could just reconfigure the system to display the login prompt unconditionally. The way attestation is nominally supposed to work is that a remote system cryptographically verifies the state of the local machine before giving it some secret. But that doesn't work in this case because the secret -- the thing that allows the user to sign in -- is coming from the local user rather than a remote machine. The attacker doesn't need to perform attestation or retrieve anything from a remote machine in order to display a local login prompt and collect the user's credentials, and that's the end of the game. > Rooted android devices can be set up in a way that malicous apps can gain root and then read it. So can PCs, or various non-rooted android devices that bank apps run on even though they have known unpatched vulnerabilities. > But this comes with a different risk profile. A bank can reduce risk for a subset of their customers. How is it reducing risk for anyone? Each person still has the same risk profile as before. The person with a locked Android device still has a locked Android device, the person with an unlocked Android device is now forced to use a PC which is an inconvenience with no security advantage.
- AnthonyMouse 1y ago
  > Android has proper sandboxing which means that other apps can't read the token owned by the bank app. Let's consider this alternative as well: Scenario 1: Device has no malicious code at all; same as scenario 1 before. Scenario 2: Device has a malicious app but the malicious app doesn't have root and the OS (regardless of whether it's Android or something else) enforces proper sandboxing. The malicious app can't extract the bank authentication token regardless of attestation. Scenario 3: Device is fully compromised; malicious code has root. Same as before, if you enter your credentials into this device the attacker gets them. The problem is that the only useful thing for attestation to do is to distinguish between 1 or 2 vs. 3, but that's the thing it can't do because if the malicious code is privileged it can replace the bank app with one that exfiltrates the credentials without requiring attestation, so the only cases where attestation is happening are the ones where it isn't needed.
  - charcircuit 1y ago
    If the device is fully compromised then it can just take the authentication token. It's already game over.
    - AnthonyMouse 1y ago
      That's the point. The device being compromised to the point that malicious code is actually meddling with the bank app is the only time that having it fail attestation would be useful. The other cases are useless/vexing false positives. But attestation doesn't happen in the one case it would be useful because then the attacker-controlled code won't even attempt to do it, it will just exfiltrate the user's credentials to the attacker.

charcircuit 1y ago

>Nothing This is far from the truth assuming by compromised you mean that the user has installed a malicous app. Android has proper sandboxing which means that other apps can't read the token owned by the bank app. This is part of the Android security model and attestation is evidence that the Android security model is being enforced. Phishing apps are different from an app that steals existing authentication tokens on the device.

fc417fc802 1y ago
You aren't responding to the scenario that was posed. You're assuming an isolated compromised app on an otherwise clean device. GP is assuming a compromised device. Of course attestation does nothing to improve the "single compromised app" case since (assuming Android) that goes nowhere either way. The only thing attestation does is meddle in end user affairs.
- charcircuit 1y ago
  >if the phone isn't compromised then the owner having root isn't a security problem The scenario is the phone isn't compromised. Having root means you, or an app you run can bypass the security protecting the authentication token.
  - fc417fc802 1y ago
    And now you're being intentionally difficult. Please interpret things in the most plausible manner. Beyond common decency, it's part of the site guidelines. By "not compromised" GP clearly meant a scenario where no malicious apps are present. I agree that's a serious omission. I responded to your scenario (a nonzero number of malicious apps) in my earlier comment. Any Android device will defend against that regardless of the presence of attestation. Any non-android device can still use online banking and thus attestation doesn't appear to accomplish anything legitimate. Building out proper support for hardware tokens would provide superior security in approximately all cases. The specific "root on android" scenario isn't generally a concern. Typical implementations require explicitly granting the capability to a given app. A malicious app can't gain it without fooling the user, at which point it could more easily phish the credentials and possibly even proxy an entire session.
    - charcircuit 1y ago
      >Please interpret things in the most plausible manner. Your suggestion is not plausible as every security feature has 0 security value if there is nothing malicous. It would be like someone saying that antivirus is useless because if someone doesn't have a virus then it doesn't do anything. >Any Android device will defend against that regardless of the presence of attestation. Rooted android devices can be set up in a way that malicous apps can gain root and then read it. >Any non-android device can still use online banking But this comes with a different risk profile. A bank can reduce risk for a subset of their customers. >Building out proper support for hardware tokens would provide superior security in approximately all cases. I think usually the hardware token gains you access to an authentication token. You don't sign every request you are making with a hardware only key. >Typical implementations require explicitly granting the capability to a given app. And the majority of users have no clue what an app is able to do. If root is given to it then it can do anything. This is in contrast to when root isn't available and users are protected by the sandbox the app is in.
      - AnthonyMouse 1y ago
        > It would be like someone saying that antivirus is useless because if someone doesn't have a virus then it doesn't do anything. Suppose you have an "antivirus" program that works like this: The system makes a list of every program that runs as root during boot and then at the end of boot the antivirus program checks the list for unexpected programs and if it finds any it displays an error and refuses to display the login prompt to prevent the user from typing their password into a compromised device. That "antivirus" system is useless, because if a malicious program did run as root during boot then it could just reconfigure the system to display the login prompt unconditionally. The way attestation is nominally supposed to work is that a remote system cryptographically verifies the state of the local machine before giving it some secret. But that doesn't work in this case because the secret -- the thing that allows the user to sign in -- is coming from the local user rather than a remote machine. The attacker doesn't need to perform attestation or retrieve anything from a remote machine in order to display a local login prompt and collect the user's credentials, and that's the end of the game. > Rooted android devices can be set up in a way that malicous apps can gain root and then read it. So can PCs, or various non-rooted android devices that bank apps run on even though they have known unpatched vulnerabilities. > But this comes with a different risk profile. A bank can reduce risk for a subset of their customers. How is it reducing risk for anyone? Each person still has the same risk profile as before. The person with a locked Android device still has a locked Android device, the person with an unlocked Android device is now forced to use a PC which is an inconvenience with no security advantage.
AnthonyMouse 1y ago
> Android has proper sandboxing which means that other apps can't read the token owned by the bank app. Let's consider this alternative as well: Scenario 1: Device has no malicious code at all; same as scenario 1 before. Scenario 2: Device has a malicious app but the malicious app doesn't have root and the OS (regardless of whether it's Android or something else) enforces proper sandboxing. The malicious app can't extract the bank authentication token regardless of attestation. Scenario 3: Device is fully compromised; malicious code has root. Same as before, if you enter your credentials into this device the attacker gets them. The problem is that the only useful thing for attestation to do is to distinguish between 1 or 2 vs. 3, but that's the thing it can't do because if the malicious code is privileged it can replace the bank app with one that exfiltrates the credentials without requiring attestation, so the only cases where attestation is happening are the ones where it isn't needed.
- charcircuit 1y ago
  If the device is fully compromised then it can just take the authentication token. It's already game over.
  - AnthonyMouse 1y ago
    That's the point. The device being compromised to the point that malicious code is actually meddling with the bank app is the only time that having it fail attestation would be useful. The other cases are useless/vexing false positives. But attestation doesn't happen in the one case it would be useful because then the attacker-controlled code won't even attempt to do it, it will just exfiltrate the user's credentials to the attacker.