Don't read payload data into memory

[cg-cri-gl]

Hi,

can you please take a look into following crash (it's _sigkill_ed according to strace ) of command:
python3 -m pyimg4 im4p create -i work/ramdisk.dmg -o work/ramdisk.im4p -f rdsk
?

The details:

1. strace message
   ........
   write(1, "Reading work/ramdisk.dmg...\n", 28Reading work/ramdisk.dmg... ) = 28 lseek(3, 0, SEEK_CUR) = 0 newfstatat(3, "", {st_mode=S_IFREG|0644, st_size=300000000, ...}, AT_EMPTY_PATH) = 0 mmap(NULL, 300003328, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f60b7de5000 read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 300000001) = 300000000 read(3, "", 1) = 0 openat(AT_FDCWD, "work/ramdisk.im4p", O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = 4 newfstatat(4, "", {st_mode=S_IFREG|0644, st_size=0, ...}, AT_EMPTY_PATH) = 0 ioctl(4, TCGETS, 0x7fffb69102a0) = -1 ENOTTY (Inappropraiate ioctl for device) lseek(4, 0, SEEK_CUR) = 0 mmap(NULL, 300003328, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f60a5fca000 mmap(NULL, 300003328, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f60941af000 +++ killed by SIGKILL +++ Killed

2. The ramdisk image is crafted from few items (not familiar with this whole process), but obtaining this one seems relevant to me:
   pzb -g 078-34285-078.dmg https://updates.cdn-apple.com/2022SummerFCS/fullrestores/012-41753/03DF14B7-8351-497E-B02E-188251541117/iPhone_4.0_64bit_15.6_19G71_Restore.ipsw; however to get to this point following script was used : (which is itself called by palera1n.sh )

3. pip list | grep pyimg pyimg4 0.7
   Shout out if more info needed, Thanks !

[m1stadev]

From what I know about this issue, it's due to Python being killed because of too much memory being used. I'm assuming this is due to the fact that PyIMG4 reads the payload data into memory, and given that the ramdisk is like 100+ mbs, could cause a crash on resource-limited systems. I'll have to update PyIMG4 to not do that.