diff options
Diffstat (limited to 'sh.asm')
| -rw-r--r-- | sh.asm | 241 |
1 files changed, 125 insertions, 116 deletions
@@ -1,43 +1,51 @@ section .data - sigs: dd 0x2 - cpid: dd 0x0 - eol: db `\n` - msg: db "Welcome to deadbeef shell", 0x21, `\n` - prompt: db "[0xdeadbeef]", 0x20 - nfe: db "Error: program not found", 0x2e, `\n` - env: db "/etc/environment", 0x0 - boem: db "Error: input overflows buffer", 0x2e, `\n` - no_dir_str: db "cd: Unknown directory",`\n` - no_dir_str_len: equ $-no_dir_str - invalid_int_str: db "exit: Invalid integer",`\n` - invalid_int_str_len: equ $-invalid_int_str - ;Flag indicating ability to execute - X_OK equ 0x1 - - ;Indicates that a file can be accessed in the way specified - F_OK equ 0x0 - - ;option for waitid - P_PGID equ 2 + sigs dd 0x2 + cpid dd 0x0 + eol db `\n` + msg db "Welcome to deadbeef shell!", `\n` + env_str db "/etc/environment", 0x0 + + prompt_str db "[0xdeadbeef] " + prompt_str_len equ $-prompt_str - ;Special file descriptors - fd_stdin equ 0x00 - fd_stdout equ 0x01 - fd_stderr equ 0x02 - - ;Syscall constants - sys_read equ 0x00 - sys_write equ 0x01 - sys_open equ 0x02 - sys_close equ 0x03 - sys_access equ 0x15 - stub_fork equ 0x39 - stub_execve equ 0x3b - sys_exit equ 0x3c - sys_wait4 equ 0x3d - sys_kill equ 0x3e - sys_chdir equ 0x50 - sys_waitid equ 0xf7 + not_func_str db "Error: program not found.", `\n` + not_func_str_len equ $-not_func_str + + boe_str db "Error: input overflows buffer.", `\n` + boe_str_len equ $-boe_str + + no_dir_str db "cd: Unknown directory.",`\n` + no_dir_str_len equ $-no_dir_str + + invalid_int_str db "exit: Invalid integer.",`\n` + invalid_int_str_len equ $-invalid_int_str + ;Flag indicating ability to execute + X_OK equ 0x1 + + ;Indicates that a file can be accessed in the way specified + F_OK equ 0x0 + + ;option for waitid + P_PGID equ 2 + + ;Special file descriptors + fd_stdin equ 0x00 + fd_stdout equ 0x01 + fd_stderr equ 0x02 + + ;Syscall constants + sys_read equ 0x00 + sys_write equ 0x01 + sys_open equ 0x02 + sys_close equ 0x03 + sys_access equ 0x15 + stub_fork equ 0x39 + stub_execve equ 0x3b + sys_exit equ 0x3c + sys_wait4 equ 0x3d + sys_kill equ 0x3e + sys_chdir equ 0x50 + sys_waitid equ 0xf7 section .text @@ -66,8 +74,8 @@ _start: _read_loop: mov rax, sys_write mov rdi, fd_stdout - mov rsi, prompt - mov rdx, 0xd + mov rsi, prompt_str + mov rdx, prompt_str_len syscall mov r8, -0x1 @@ -85,8 +93,8 @@ _read_loopr: mov r12, _quit cmp byte [r15], 0x0 je _weol - ;Start using r12 to hold the number of args - xor r12,r12 + ;Start using r12 to hold the number of args + xor r12,r12 ; call _parse jmp _parse @@ -111,17 +119,17 @@ _exec: ;waits for the process to close _wait_for_proc: - mov r12, r10 ;backup + mov r12, r10 ;backup - mov rsi, rax - mov rax, sys_waitid - xor rdi, rdi - xor rdx, rdx - mov r10, P_PGID - xor r8, r8 - syscall + mov rsi, rax + mov rax, sys_waitid + xor rdi, rdi + xor rdx, rdx + mov r10, P_PGID + xor r8, r8 + syscall - mov r10, r12 ;restore + mov r10, r12 ;restore mov dword [cpid], -0x1 jmp _read_loop @@ -132,7 +140,7 @@ _wait_for_proc: ; other: r15 (buffer) _parse_path: mov rax, sys_open - mov rdi, env + mov rdi, env_str xor rsi, rsi syscall test rax, rax ;check if rax is 0 @@ -213,7 +221,7 @@ _bzero: ;input: r15 (buffer) ;output: r13 (path), r14 (arguments) ;clobbered: r8, rax, rbx, rcx -_parse: ; needs special commands: cd exit export eval +_parse: ;syscall 80 is chdir, so do that first, it's easiest ;It takes a path string. ;also needs pipes (|, >, <) @@ -255,7 +263,7 @@ _subzp: mov byte [r8+r15], 0x0 lea rax, [r8+r15+1] push rax - inc r12 + inc r12 jmp _parse1 _parse2: @@ -269,40 +277,41 @@ _parse3: inc r8 cmp r8, r10 je _parse4 - ;r15 holds the name that the user entered, so we'll use that for shell builtins - mov rcx,`\0\0\0exit\0` - mov r13, [r15] - shl r13, 24 ;Remove the last character, because it's an arg not the name of it - cmp r13, rcx - je _builtin_exit - mov rcx,`\0\0\0\0\0cd\0` - shl r13, 16 ;Remove the extra characters for cd, note how we're doing the - ;longest function names first then the shorter later - cmp r13, rcx - je _builtin_cd - ;END OF BUILTINS + ; Builtins to add: export, eval + ;r15 holds the name that the user entered, so we'll use that for shell builtins + mov rcx,`\0\0\0exit\0` + mov r13, [r15] + shl r13, 24 ;Remove the last character in r13, because it's an arg not the name of it + cmp r13, rcx + je _builtin_exit + mov rcx,`\0\0\0\0\0cd\0` + shl r13, 16 ;Remove the extra characters for cd, note how we're doing the + ;longest function names first then the shorter later + cmp r13, rcx + je _builtin_cd + ;END OF BUILTINS mov r13, r15 mov rcx, [r9+r8*8] push r8 jmp _concat -_parse4: ; not found +_parse4: ; Function not found mov rax, sys_write mov rdi, fd_stdout - mov rsi, nfe - mov rdx, 0x1a + mov rsi, not_func_str + mov rdx, not_func_str_len syscall jmp _read_loop ; Checks that the program rbx can be executed _parse5: - mov rax, sys_access - mov rdi, rbx - mov rsi, X_OK + mov rax, sys_access + mov rdi, rbx + mov rsi, X_OK syscall - pop r8 - ;Check if it can be executed + pop r8 + ;Check if it can be executed cmp rax, F_OK jl _parse3 @@ -312,10 +321,10 @@ _parse6: jmp _exec _parse7: ; absolute path - mov rax, sys_access - mov rdi, rbx - mov rsi, X_OK - syscall + mov rax, sys_access + mov rdi, rbx + mov rsi, X_OK + syscall cmp rax, F_OK jl _parse4 @@ -404,8 +413,8 @@ _join2: _boe: mov rax, sys_write mov rdi, 0x1 - mov rsi, boem - mov rdx, 0x1f + mov rsi, boe_str + mov rdx, boe_str_len jmp _quit ; interrupt signal handler @@ -442,48 +451,48 @@ _quit: ;cd [dir (rax)] ;changes to the given directory _builtin_cd: - mov rdi,rax - mov rax, sys_chdir - syscall - test rax, rax - jz _read_loop - mov rax, sys_write - mov rdi, fd_stdout - mov rsi, no_dir_str - mov rdx, no_dir_str_len - syscall - jmp _read_loop + mov rdi,rax + mov rax, sys_chdir + syscall + test rax, rax + jz _read_loop + mov rax, sys_write + mov rdi, fd_stdout + mov rsi, no_dir_str + mov rdx, no_dir_str_len + syscall + jmp _read_loop ;usage: exit [status] ;exits with the given status or 0 if one hasn't been provided _builtin_exit: - ;convert first arg to an int if present - ;exit with that code - _string_to_int: - xor rdi, rdi - ;accumulate in rdi since it's also the register used to provide the status - ;to sys_exit - xor rdx, rdx - cmp r12, 0 - jz _string_to_int_end - _string_to_int_loop: - mov dl, [rax] ; Convert this to a number - test dl, dl ;Checks for NULL - jz _string_to_int_end - sub dl, `0` ;sub because we'll need to do this anyway - jl _invalid_int - cmp dl, 9 ;since we've already subtracted we can just compase with 9 - jg _invalid_int - imul rdi,10 - add rdi, rdx - inc rax - jmp _string_to_int_loop - _string_to_int_end: + ;convert first arg to an int if present + ;exit with that code + _string_to_int: + xor rdi, rdi + ;accumulate in rdi since it's also the register used to provide the status + ;to sys_exit + xor rdx, rdx + cmp r12, 0 + jz _string_to_int_end + _string_to_int_loop: + mov dl, [rax] ; Convert this to a number + test dl, dl ;Checks for NULL + jz _string_to_int_end + sub dl, `0` ;sub because we'll need to do this anyway + jl _invalid_int + cmp dl, 9 ;since we've already subtracted we can just compase with 9 + jg _invalid_int + imul rdi,10 + add rdi, rdx + inc rax + jmp _string_to_int_loop + _string_to_int_end: mov rax, sys_exit syscall _invalid_int: - mov rax,sys_write + mov rax,sys_write mov rdi, fd_stdout mov rsi, invalid_int_str mov rdx, invalid_int_str_len - syscall - jmp _read_loop + syscall + jmp _read_loop |