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I think the jailbreak IPA signing isn’t working because it needs the `get-task-allow` entitlement which idk if every tool is aware of. This entitlement is only

by osy 7y ago

I think the jailbreak IPA signing isn’t working because it needs the `get-task-allow` entitlement which idk if every tool is aware of. This entitlement is only given out in development profiles and not any distribution profiles so I can’t upload to TestFlight either. If Apple locks down what you can do with `get-task-allow` in the future then a jailbreak would be required to run this.

lazerl0rd 7y ago
Would you by any chance consider TestFlight to distribute UTM? iSH (a usermode Linux "terminal" emulator) has been for quite some time, and I can't see why you shouldn't be able to.
- osy 7y ago
  > This entitlement is only given out in development profiles and not any distribution profiles so I can’t upload to TestFlight either.
  - lazerl0rd 7y ago
    Ah sorry, my bad, I skipped over that. Here's an idea - you could start a "fundraising" of sorts and if you get enough you could purchase a developer profile to publish to TestFlight.
    - osy 7y ago
      You can’t purchase such a profile. Apple doesn’t ever give them out.
      - lazerl0rd 7y ago
        I thought this would be part of their $99/year subscription, well that's unfortunate. Thanks again for your project.
    - JimDabell 7y ago
      The problem here is not that they can't obtain a development certificate. The problem is that you cannot use a development certificate to distribute an app on TestFlight or the App Store to other people. There are two types of certificate – development certificates, which allow get-task-allow for debugging purposes and can be installed directly to a device; and distribution certificates, which do not allow get-task-allow and can be distributed through ad-hoc means, Test Flight, or the App Store. If this app requires get-task-allow, then it needs to be signed with a development certificate to run. If it's signed with a development certificate, then it can't be distributed to other people.
- jsjohnst 7y ago
  iSH works differently. It’s not running “Linux” and it isn’t virtualizing hardware either. Anything you run has to be compiled already and the syscalls are emulated, there is no Linux kernel in iSH.
  - lazerl0rd 7y ago
    I said it was a 'usermode Linux "terminal" emulator', never said it was a VM or anything like that. IIRC the dev said he also wasn't allowed to publish it to the App Store and I assume it falls under the same catagory of "not allowed" in Apple's eyes as UTM would've had.
    - saagarjha 7y ago
      > I said it was a 'usermode Linux "terminal" emulator', never said it was a VM or anything like that. It's a full x86 emulator. > IIRC the dev said he also wasn't allowed to publish it to the App Store He didn't, it's just never been tested whether it could be on the store or not.
      - jedieaston 7y ago
        Actually, someone compiled it, added ads, and put it on the App Store. Not sure if it is still there, but it got through approval.
        saagarjha 7y ago
        Oh, that happens all the time. The real test is when the official app gets approved and stays on the App Store.
  - kdrag0n 7y ago
    iSH actually uses a semi-JIT to emulate an x86 CPU — it doesn't run ARM64 code. It basically creates an arrray of function pointers to snippets of pre-translated code. It's not a full JIT like UTM, but it's an interesting workaround for iOS' restrictions. Official description: https://github.com/tbodt/ish#a-note-on-the-jit https://github.com/tbodt/ish#a-note-on-the-jit
asveikau 7y ago
Curious what you use that for. My previous exposure for "get task" on Darwin/XNU is it's useful for reading or writing the memory of another process and suspending or resuming its threads, as in writing a debugger.
- saagarjha 7y ago
  The app pretends to debug itself, which tricks the kernel into allowing it to flip the permissions of pages between write and execute. To do this it needs the get_task_allow entitlement.
  - asveikau 7y ago
    Ah ok. So everything with a JIT will need this. I think I might even have read that somewhere long ago. This is a weird thing by the way. It seems to me like you should be able to debug or do VM syscalls against yourself because there is no escalation of privilege. Debugging another process makes much more sense to block. But maybe my opinion is invalid because I also happen to think disallowing jit with kernel permissions is very silly. (Maybe dropping ability to do this in the style of openbsd's pledge(2) would be appropriate, but only for a process that really wants extra security.)
    - saagarjha 7y ago
      > So everything with a JIT will need this. Actual JITs (ones blessed by Apple, not hacks like these) possess the dynamic-codesigning entitlement, and can just make RWX pages. > But maybe my opinion is invalid because I also happen to think disallowing jit with kernel permissions is very silly. Your opinion isn't invalid, but it goes against Apple's security model of iOS (namely: apps should not be able to modify themselves).
      - asveikau 7y ago
        > Your opinion isn't invalid, but it goes against Apple's security model of iOS (namely: apps should not be able to modify themselves). And my position is this is a silly approach, or, maybe is ok but should be opt-in, or perhaps opt-out with third parties being automatically trusted to decide they want to use JIT without hoops. W^X is good default policy but Apple's policy is unreasonable and paranoid.

by osy 7y ago

lazerl0rd 7y ago

Would you by any chance consider TestFlight to distribute UTM? iSH (a usermode Linux "terminal" emulator) has been for quite some time, and I can't see why you shouldn't be able to.

osy 7y ago
> This entitlement is only given out in development profiles and not any distribution profiles so I can’t upload to TestFlight either.
- lazerl0rd 7y ago
  Ah sorry, my bad, I skipped over that. Here's an idea - you could start a "fundraising" of sorts and if you get enough you could purchase a developer profile to publish to TestFlight.
  - osy 7y ago
    You can’t purchase such a profile. Apple doesn’t ever give them out.
    - lazerl0rd 7y ago
      I thought this would be part of their $99/year subscription, well that's unfortunate. Thanks again for your project.
  - JimDabell 7y ago
    The problem here is not that they can't obtain a development certificate. The problem is that you cannot use a development certificate to distribute an app on TestFlight or the App Store to other people. There are two types of certificate – development certificates, which allow get-task-allow for debugging purposes and can be installed directly to a device; and distribution certificates, which do not allow get-task-allow and can be distributed through ad-hoc means, Test Flight, or the App Store. If this app requires get-task-allow, then it needs to be signed with a development certificate to run. If it's signed with a development certificate, then it can't be distributed to other people.
jsjohnst 7y ago
iSH works differently. It’s not running “Linux” and it isn’t virtualizing hardware either. Anything you run has to be compiled already and the syscalls are emulated, there is no Linux kernel in iSH.
- lazerl0rd 7y ago
  I said it was a 'usermode Linux "terminal" emulator', never said it was a VM or anything like that. IIRC the dev said he also wasn't allowed to publish it to the App Store and I assume it falls under the same catagory of "not allowed" in Apple's eyes as UTM would've had.
  - saagarjha 7y ago
    > I said it was a 'usermode Linux "terminal" emulator', never said it was a VM or anything like that. It's a full x86 emulator. > IIRC the dev said he also wasn't allowed to publish it to the App Store He didn't, it's just never been tested whether it could be on the store or not.
    - jedieaston 7y ago
      Actually, someone compiled it, added ads, and put it on the App Store. Not sure if it is still there, but it got through approval.
      - saagarjha 7y ago
        Oh, that happens all the time. The real test is when the official app gets approved and stays on the App Store.
- kdrag0n 7y ago
  iSH actually uses a semi-JIT to emulate an x86 CPU — it doesn't run ARM64 code. It basically creates an arrray of function pointers to snippets of pre-translated code. It's not a full JIT like UTM, but it's an interesting workaround for iOS' restrictions. Official description: https://github.com/tbodt/ish#a-note-on-the-jit https://github.com/tbodt/ish#a-note-on-the-jit

asveikau 7y ago

Curious what you use that for. My previous exposure for "get task" on Darwin/XNU is it's useful for reading or writing the memory of another process and suspending or resuming its threads, as in writing a debugger.

saagarjha 7y ago
The app pretends to debug itself, which tricks the kernel into allowing it to flip the permissions of pages between write and execute. To do this it needs the get_task_allow entitlement.
- asveikau 7y ago
  Ah ok. So everything with a JIT will need this. I think I might even have read that somewhere long ago. This is a weird thing by the way. It seems to me like you should be able to debug or do VM syscalls against yourself because there is no escalation of privilege. Debugging another process makes much more sense to block. But maybe my opinion is invalid because I also happen to think disallowing jit with kernel permissions is very silly. (Maybe dropping ability to do this in the style of openbsd's pledge(2) would be appropriate, but only for a process that really wants extra security.)
  - saagarjha 7y ago
    > So everything with a JIT will need this. Actual JITs (ones blessed by Apple, not hacks like these) possess the dynamic-codesigning entitlement, and can just make RWX pages. > But maybe my opinion is invalid because I also happen to think disallowing jit with kernel permissions is very silly. Your opinion isn't invalid, but it goes against Apple's security model of iOS (namely: apps should not be able to modify themselves).
    - asveikau 7y ago
      > Your opinion isn't invalid, but it goes against Apple's security model of iOS (namely: apps should not be able to modify themselves). And my position is this is a silly approach, or, maybe is ok but should be opt-in, or perhaps opt-out with third parties being automatically trusted to decide they want to use JIT without hoops. W^X is good default policy but Apple's policy is unreasonable and paranoid.