3DS System Flaws

Exploits are used to execute unofficial code (homebrew) on the Nintendo 3DS. This page is a list of known 3DS-mode exploits.

Failed attempts

Here are listed all attempts at exploiting 3DS software that have failed so far.

• Pushmo (3DSWare), QR codes: level name is properly limited to 16 characters, game doesn't crash with a longer name. The only possible crashes are triggered by out-of-bounds values, these crashes are caused by the application attempting to load a ptr from a buffer located at NULL.
• Pyramids (3DSWare), QR codes: no strings. The LZ10 compression can't be exploited either. Only crashes are from out-of-bounds values (like background ID) and are not exploitable.
• 3DS browser, 2^32 characters long string: this is similar to the vuln fixed here, concat-large-strings-crash2.html triggers a crash which is about the same as the one triggered by a 2^32 string. Most of the time this vuln will cause a memory page permissions fault, since the webkit code attempts to copy the string text data to the output buffer located in read-only CRO heap memory. The only difference between a crash triggered by a 2^32 string and the concat-large-strings-crash2.html crash is that the former copies the string data using the original string length(like 1 text character for "x", 4 for "xxxx") while the latter attempts to copy >12MB. In some very rare cases a thread separate from the string data-copy thread will crash, this might be exploitable however this is useless since it rarely crashes this way.

Current efforts

There are people working on finding exploits and documenting the 3DS. Here's a list of some current efforts being made to make homebrew on the 3DS possible:

• Neimod has been working on a RAM dumping setup for a little while now. He's desoldered the 3DS's RAM chip and hooked it and the RAM pinouts on the 3DS's PCB up to a custom RAM dumping setup. Recent photos show that the setup is working quite well, with the 3DS successfully booting up. Pictures of neimod's work can be found on his Flickr stream.

Fixed vulnerabilities

• The following was fixed with 7.0.0-13, see here for details. Too long or corrupted strings (01Ah 2 Nickname length in characters 050h 2 Message length in characters) in the NVRAM DS user settings cause (System Settings->Other Settings->Profile->Nintendo DS Profile) to crash in 3DS-mode due to a stack-smash. The DSi is not vulnerable to this, DSi launcher(menu) and DSi System Settings will reset the NVRAM user-settings if the length field values are too long(same result as when the CRCs are invalid).

Tips and info

The 3DS uses the XN feature of the ARM processor, and only apps that have the necessary permissions in their headers can set memory to be executable. This means that although a usable buffer overflow exploit would still be useful, it would not go the entire way towards allowing code to be run in an easy/practical fashion (ie an actual homebrew launcher) - for that, an exploit in the system is required. A buffer overflow exploit does, however, provide enough wriggle room through the use of return-oriented programming to potentially trigger a system exploit.

SD card extdata and SD savegames can be attacked, for consoles where the console-unique movable.sed was dumped.

System flaws

ARM11 kernel

Summary	Description	Fixed in system version
SVC table too small	The table of function pointers for SVC's only contains entries up to 0x7D, but the biggest allowed SVC for the table is 0x7F. Thus, executing svc7E or svc7F would make the SVC-handler read after the buffer, and interpret some ARM instructions as function pointers. However this would require patching the kernel .text or modifying SVC-access-control. Even if you could get these to execute, they would still jump to memory that isn't mapped as executable.	None
svcBackdoor (0x7B)	This backdoor allows executing SVC-mode code at the user-specified code-address. This is used by Process9, using this on the ARM11(with NATIVE_FIRM) requires patching the kernel .text or modifying SVC-access-control.	None
0xEFF00000 / 0xDFF00000 ARM11 kernel virtual-memory	The ARM11 kernel-mode 0xEFF00000/0xDFF00000 virtual-memory(size 0x100000) is mapped to phys-mem 0x1FF00000(entire DSP-mem + entire AXIWRAM), with permissions RW-. This is used during ARM11 kernel startup, this never seems to be used after that however.	None
svcStartInterProcessDma	For svcStartInterProcessDma, the kernel code had the following flaws: Originally the ARM11-kernel read the input DmaConfig structure directly in kernel-mode(ldr(b/h) instructions), without checking whether the DmaConfig address is readable under userland. This was fixed by copying that structure to the SVC-mode stack, using the ldrbt instruction. Integer overflows for srcaddr+size and dstaddr+size are now checked(with 6.0.0-11), which were not checked before. The kernel now also checks whether the srcaddr/dstaddr(+size) is within userland memory(0x20000000), the kernel now(with 6.0.0-11) returns an error when the address is beyond userland memory. Using an address >=0x20000000 would only result in the kernel reading from the process L1 MMU table, beyond the memory allocated for that MMU table(for vaddr->physaddr conversion), therefore this issue likely(?) wasn't useful.	6.0.0-11
svcControlMemory Parameter checks	For svcControlMemory the parameter check had these two flaws: The allowed range for addr0, addr1, size parameters depends on which MemoryOperation is being specified. The limitation for GSP heap was only checked if op=(u32)0x10003. By setting a random bit in op that has no meaning (like bit17?), op would instead be (u32)0x30003, and the range-check would be less strict and not accurate. However, the kernel doesn't actually use the input address for LINEAR memory-mapping at all besides the range-checks, so this isn't actually useful. This was fixed in the kernel by just checking for the LINEAR bit, instead of comparing the entire MemoryOperation value with 0x10003. Integer overflows on (addr0+size) are now checked that previously weren't(this also applies to most other address checks elsewhere in the kernel).	5.0.0-11
Command request/response buffer overflow	Originally the kernel did not check the word-values from the command-header. Starting with 5.0.0-11, the kernel will trigger a kernelpanic() when the total word-size of the entire command(including the cmd-header) is larger than 0x40-words(0x100-bytes). This allows overwriting threadlocalstorage+0x180 in the destination thread, however since the data written there would be translate parameters(such as header-words + buffer addresses), exploiting this would likely be very difficult if possible at all. If the two words at threadlocalstorage+0x180 could be overwritten with controlled data this way, one could then use a command with a buffer-header of ((size<<14) | 2) to write arbitrary memory to any RW userland memory in the destination process.	5.0.0-11
SVC stack allocation overflows	svcSetResourceLimitValues, svcGetThreadList, svcGetProcessList, svcReplyAndReceive, svcWaitSynchronizationN only checked bit31 before multiplying by 4/16. If a large integer was passed as input to one of these syscalls, an integer overflow would occur, and too little memory would have been allocated on stack. It might allow for arbitrary kernel code execution.	5.0.0-11
svcControlMemory MemoryOperation MAP memory-permissions	svcControlMemory with MemoryOperation=MAP allows mapping the already-mapped process virtual-mem at addr1, to addr0. The lowest address permitted for addr1 is 0x00100000. Originally the ARM11 kernel didn't check memory permissions for addr1. Therefore .text as addr1 could be mapped elsewhere as RW- memory, which allowed ARM11 userland code-execution.	4.1.0-8
Command input/output buffer permissions	Originally the ARM11 kernel didn't check memory permissions for the input/output buffers for commands. Starting with 4.0.0-7 the ARM11 kernel will trigger a kernelpanic() if the input/output buffers don't have the required memory permissions. For example, this allowed a FSUSER file-read to .text, which therefore allowed ARM11-userland code execution.	4.0.0-7
svcReadProcessMemory/svcWriteProcessMemory memory permissions	Originally the kernel only checked the first page(0x1000-bytes) of the src/dst buffers, for svcReadProcessMemory and svcWriteProcessMemory. There is no known retail processes which have access to these SVCs.	4.0.0-7

FIRM ARM11 modules

Summary	Description	Fixed in system version
"srv:pm" process registration	Originally any process had access to the port "srv:pm". The PID's used for the (un)registration commands are not checked either. This allowed any process to re-register itself with "srv:pm", and therefore allowed the process to give itself access to any service, bypassing the exheader service-access-control list. This was fixed in 7.0.0-13: starting with 7.0.0-13 "srv:pm" is now a service instead of a globally accessible port. Only processes with PID's less than 6 (in other words: fs, ldr, sm, pm, pxi modules) have access to it. With 7.0.0-13 there can only be one session for "srv:pm" open at a time(this is used by pm module), svcBreak will be executed if more sessions are opened by the processes which can access this. This flaw was needed for exploiting the <=v4.x Process9 PXI vulnerabilities from ARM11 userland ROP, since most applications don't have access to those service(s).	7.0.0-13