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PS5 Jailbreaking       Thread starter PSXHAX       Start date May 27, 2021 at 4:37 PM       10,466       15      
Recently an SMAP (Supervisor Mode Access Prevention) Bypass FreeBSD 12 Vulnerability reported by m00nbsd via Twitter was disclosed on the HackerOne.com bug bounty site in a flurry of PlayStation Hacktivity, which according to m00nbsd may also affect the PlayStation 5 although he reports being unable to confirm the SMAP bypass on a PS5 console. :geek:

For those following the PS5 Jailbreak updates and PS5 NFOs in the PS5Scene, this comes proceeding the Talos WebSocket Vulnerability that may be present in the PS5 WebKit... also unconfirmed in part due to the limited console supply as a result of PlayStation 5 Scalpers.

The potential PS5 SMAP Bypass references CVE-2021-29628, which is described as follows:

In FreeBSD 13.0-STABLE before n245764-876ffe28796c, 12.2-STABLE before r369857, 13.0-RELEASE before p1, and 12.2-RELEASE before p7, a system call triggering a fault could cause SMAP protections to be disabled for the duration of the system call. This weakness could be combined with other kernel bugs to craft an exploit.

Finally, below is the SMAP Bypass report summary for those interested to quote:

SMAP is a security feature on x86 CPUs, that forbids ring0 from reading/writing to ring3 pages, making it harder to exploit entire classes of vulnerabilities.

There is a vulnerability in FreeBSD 12 that allows SMAP to be bypassed by userland. There is a very high probability that it affects the PS5 but I was unable to access a PS5 firmware to confirm it.

This vuln downgrades the security properties of the OS, and is a building block for exploitation chains.

Details

With SMAP enabled, when %RFLAGS.AC is cleared the kernel will page-fault if it tries to access a page marked as "user page". When %RFLAGS.AC is set the kernel can access the user pages as if SMAP was not enabled.

In the FreeBSD kernel, a few functions exist that temporarily set %RFLAGS.AC in order to access user pages: the copyin() and copyout() functions.

These functions are used in all syscalls and are the only ways the kernel can copy data from/to userland.

These functions handle faults gracefully, that is, if userland passes an unmapped address and the kernel tries to copy data from it, the functions will simply return an error without kernel panic.

There is a bug in the fault handling of these functions. Typically copyin() is implemented as follows:
Code:
.macro    COPYIN smap erms     /* ... */    movq    $copy_fault,PCB_ONFAULT(%r11)    /* ... */    stac // set %RFLAGS.AC, to allow access to user pages    do_the_copyin    clac // clear %RFLAGS.AC, to forbid access to user pages    /* ... */ copy_fault:    movq    $0,PCB_ONFAULT(%r11)    movl    $EFAULT,%eax    POP_FRAME_POINTER    ret
Code:
void trap(struct trapframe *frame) {    /* ... */            if (curpcb->pcb_onfault != NULL) {                frame->tf_rip = (long)curpcb->pcb_onfault;                return;            }    /* ... */ }
The fault handler copy_fault is registered in pcb_onfault at the beginning, then %RFLAGS.AC is set, the copy is made, and %RFLAGS.AC is cleared back.

If the copy faults for whatever reason, an exception is raised, the trap() handler sees that pcb_onfault has a pointer registered, and simply IRETs back to the pointer that was registered.

The problem is, the fault handler copy_fault does not clear %RFLAGS.AC, meaning that it remains set after copyin()/copyout() returns. The rest of the syscall will therefore execute with SMAP effectively disabled, until the kernel returns to userland where the SMAP state gets reset back to normal.

This SMAP disablement survives context switches, so a user that disables SMAP during one of his syscalls can also disable SMAP in other user/kernel threads if a rescheduling happens after/during the syscall (taking a mutex for example).

Fix

Add a clac instruction in copy_fault to clear %RFLAGS.AC:
Code:
copy_fault: +    clac     movq    $0,PCB_ONFAULT(%r11)     movl    $EFAULT,%eax     POP_FRAME_POINTER     ret
Impact

Userland can open lage windows where the kernel executes with SMAP disabled.

Lack of SMAP makes exploitation of common vulnerabilities easy/trivial.
SMAP Bypass FreeBSD 12 Vulnerability May Affect PS5 via M00nbsd.jpg
 

Comments

handsfromhell

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Yes i am finding it very difficult to get my hands on one as soon as they go up online there gone or website crashes with all the traffic wont pay 1000+ on ebay will just have to wait at this stage we wont see a jailbreak until 2025 onwards lol :(
 

sandyy

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@handsfromhell That's why i don't like bug bounty hunters. I'm not willing to pay around 100$ for 1 game. I better would stay on PS4 Pro or get XBOX Series X and that's pretty good with their ultimate game pass. PS didn't have good offers.
 
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