| Message ID | 20200813151922.1093791-3-alex.popov@linux.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Break heap spraying needed for exploiting use-after-free | expand |
On Thu, Aug 13, 2020 at 06:19:22PM +0300, Alexander Popov wrote: > Add a simple test for CONFIG_SLAB_QUARANTINE. > > It performs heap spraying that aims to reallocate the recently freed heap > object. This technique is used for exploiting use-after-free > vulnerabilities in the kernel code. > > This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying > exploitation technique. Yay tests! > > Signed-off-by: Alexander Popov <alex.popov@linux.com> > --- > drivers/misc/lkdtm/core.c | 1 + > drivers/misc/lkdtm/heap.c | 40 ++++++++++++++++++++++++++++++++++++++ > drivers/misc/lkdtm/lkdtm.h | 1 + > 3 files changed, 42 insertions(+) > > diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c > index a5e344df9166..78b7669c35eb 100644 > --- a/drivers/misc/lkdtm/core.c > +++ b/drivers/misc/lkdtm/core.c > @@ -126,6 +126,7 @@ static const struct crashtype crashtypes[] = { > CRASHTYPE(SLAB_FREE_DOUBLE), > CRASHTYPE(SLAB_FREE_CROSS), > CRASHTYPE(SLAB_FREE_PAGE), > + CRASHTYPE(HEAP_SPRAY), > CRASHTYPE(SOFTLOCKUP), > CRASHTYPE(HARDLOCKUP), > CRASHTYPE(SPINLOCKUP), > diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c > index 1323bc16f113..a72a241e314a 100644 > --- a/drivers/misc/lkdtm/heap.c > +++ b/drivers/misc/lkdtm/heap.c > @@ -205,6 +205,46 @@ static void ctor_a(void *region) > static void ctor_b(void *region) > { } > > +#define HEAP_SPRAY_SIZE 128 > + > +void lkdtm_HEAP_SPRAY(void) > +{ > + int *addr; > + int *spray_addrs[HEAP_SPRAY_SIZE] = { 0 }; (the 0 isn't needed -- and it was left there, it should be NULL) > + unsigned long i = 0; > + > + addr = kmem_cache_alloc(a_cache, GFP_KERNEL); I would prefer this test add its own cache (e.g. spray_cache), to avoid misbehaviors between tests. (e.g. the a and b caches already run the risk of getting corrupted weirdly.) > + if (!addr) { > + pr_info("Unable to allocate memory in lkdtm-heap-a cache\n"); > + return; > + } > + > + *addr = 0x31337; > + kmem_cache_free(a_cache, addr); > + > + pr_info("Performing heap spraying...\n"); > + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { > + spray_addrs[i] = kmem_cache_alloc(a_cache, GFP_KERNEL); > + *spray_addrs[i] = 0x31337; > + pr_info("attempt %lu: spray alloc addr %p vs freed addr %p\n", > + i, spray_addrs[i], addr); That's 128 lines spewed into dmesg... I would leave this out. > + if (spray_addrs[i] == addr) { > + pr_info("freed addr is reallocated!\n"); > + break; > + } > + } > + > + if (i < HEAP_SPRAY_SIZE) > + pr_info("FAIL! Heap spraying succeed :(\n"); I'd move this into the "if (spray_addrs[i] == addr)" test instead of the pr_info() that is there. > + else > + pr_info("OK! Heap spraying hasn't succeed :)\n"); And then make this an "if (i == HEAP_SPRAY_SIZE)" test > + > + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { > + if (spray_addrs[i]) > + kmem_cache_free(a_cache, spray_addrs[i]); > + } > +} > + > void __init lkdtm_heap_init(void) > { > double_free_cache = kmem_cache_create("lkdtm-heap-double_free", > diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h > index 8878538b2c13..dfafb4ae6f3a 100644 > --- a/drivers/misc/lkdtm/lkdtm.h > +++ b/drivers/misc/lkdtm/lkdtm.h > @@ -45,6 +45,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void); > void lkdtm_SLAB_FREE_DOUBLE(void); > void lkdtm_SLAB_FREE_CROSS(void); > void lkdtm_SLAB_FREE_PAGE(void); > +void lkdtm_HEAP_SPRAY(void); > > /* lkdtm_perms.c */ > void __init lkdtm_perms_init(void); > -- > 2.26.2 > I assume enabling the quarantine defense also ends up being seen in the SLAB_FREE_DOUBLE LKDTM test too, yes?
On 15.08.2020 19:59, Kees Cook wrote: > On Thu, Aug 13, 2020 at 06:19:22PM +0300, Alexander Popov wrote: >> Add a simple test for CONFIG_SLAB_QUARANTINE. >> >> It performs heap spraying that aims to reallocate the recently freed heap >> object. This technique is used for exploiting use-after-free >> vulnerabilities in the kernel code. >> >> This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying >> exploitation technique. > > Yay tests! Yes :) I'm going to improve it to demonstrate the quarantine security properties. >> Signed-off-by: Alexander Popov <alex.popov@linux.com> >> --- >> drivers/misc/lkdtm/core.c | 1 + >> drivers/misc/lkdtm/heap.c | 40 ++++++++++++++++++++++++++++++++++++++ >> drivers/misc/lkdtm/lkdtm.h | 1 + >> 3 files changed, 42 insertions(+) >> >> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c >> index a5e344df9166..78b7669c35eb 100644 >> --- a/drivers/misc/lkdtm/core.c >> +++ b/drivers/misc/lkdtm/core.c >> @@ -126,6 +126,7 @@ static const struct crashtype crashtypes[] = { >> CRASHTYPE(SLAB_FREE_DOUBLE), >> CRASHTYPE(SLAB_FREE_CROSS), >> CRASHTYPE(SLAB_FREE_PAGE), >> + CRASHTYPE(HEAP_SPRAY), >> CRASHTYPE(SOFTLOCKUP), >> CRASHTYPE(HARDLOCKUP), >> CRASHTYPE(SPINLOCKUP), >> diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c >> index 1323bc16f113..a72a241e314a 100644 >> --- a/drivers/misc/lkdtm/heap.c >> +++ b/drivers/misc/lkdtm/heap.c >> @@ -205,6 +205,46 @@ static void ctor_a(void *region) >> static void ctor_b(void *region) >> { } >> >> +#define HEAP_SPRAY_SIZE 128 >> + >> +void lkdtm_HEAP_SPRAY(void) >> +{ >> + int *addr; >> + int *spray_addrs[HEAP_SPRAY_SIZE] = { 0 }; > > (the 0 isn't needed -- and it was left there, it should be NULL) It is used in tear-down below. I'll change it to { NULL }. >> + unsigned long i = 0; >> + >> + addr = kmem_cache_alloc(a_cache, GFP_KERNEL); > > I would prefer this test add its own cache (e.g. spray_cache), to avoid > misbehaviors between tests. (e.g. the a and b caches already run the > risk of getting corrupted weirdly.) Ok, I'll do that. >> + if (!addr) { >> + pr_info("Unable to allocate memory in lkdtm-heap-a cache\n"); >> + return; >> + } >> + >> + *addr = 0x31337; >> + kmem_cache_free(a_cache, addr); >> + >> + pr_info("Performing heap spraying...\n"); >> + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { >> + spray_addrs[i] = kmem_cache_alloc(a_cache, GFP_KERNEL); >> + *spray_addrs[i] = 0x31337; >> + pr_info("attempt %lu: spray alloc addr %p vs freed addr %p\n", >> + i, spray_addrs[i], addr); > > That's 128 lines spewed into dmesg... I would leave this out. Ok. >> + if (spray_addrs[i] == addr) { >> + pr_info("freed addr is reallocated!\n"); >> + break; >> + } >> + } >> + >> + if (i < HEAP_SPRAY_SIZE) >> + pr_info("FAIL! Heap spraying succeed :(\n"); > > I'd move this into the "if (spray_addrs[i] == addr)" test instead of the > pr_info() that is there. > >> + else >> + pr_info("OK! Heap spraying hasn't succeed :)\n"); > > And then make this an "if (i == HEAP_SPRAY_SIZE)" test Do you mean that I need to avoid the additional line in the test output, printing only the final result? >> + >> + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { >> + if (spray_addrs[i]) >> + kmem_cache_free(a_cache, spray_addrs[i]); >> + } >> +} >> + >> void __init lkdtm_heap_init(void) >> { >> double_free_cache = kmem_cache_create("lkdtm-heap-double_free", >> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h >> index 8878538b2c13..dfafb4ae6f3a 100644 >> --- a/drivers/misc/lkdtm/lkdtm.h >> +++ b/drivers/misc/lkdtm/lkdtm.h >> @@ -45,6 +45,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void); >> void lkdtm_SLAB_FREE_DOUBLE(void); >> void lkdtm_SLAB_FREE_CROSS(void); >> void lkdtm_SLAB_FREE_PAGE(void); >> +void lkdtm_HEAP_SPRAY(void); >> >> /* lkdtm_perms.c */ >> void __init lkdtm_perms_init(void); >> -- >> 2.26.2 >> > > I assume enabling the quarantine defense also ends up being seen in the > SLAB_FREE_DOUBLE LKDTM test too, yes? I'll experiment with that. Thank you! Best regards, Alexander
Alexander Popov <alex.popov@linux.com> writes: > Add a simple test for CONFIG_SLAB_QUARANTINE. > > It performs heap spraying that aims to reallocate the recently freed heap > object. This technique is used for exploiting use-after-free > vulnerabilities in the kernel code. > > This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying > exploitation technique. > > Signed-off-by: Alexander Popov <alex.popov@linux.com> Why put this test in the linux kernel dump test module? I have no problem with tests, and I may be wrong but this does not look like you are testing to see if heap corruption triggers a crash dump. Which is what the rest of the tests in lkdtm are about. Seeing if the test triggers successfully triggers a crash dump. Eric > --- > drivers/misc/lkdtm/core.c | 1 + > drivers/misc/lkdtm/heap.c | 40 ++++++++++++++++++++++++++++++++++++++ > drivers/misc/lkdtm/lkdtm.h | 1 + > 3 files changed, 42 insertions(+) > > diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c > index a5e344df9166..78b7669c35eb 100644 > --- a/drivers/misc/lkdtm/core.c > +++ b/drivers/misc/lkdtm/core.c > @@ -126,6 +126,7 @@ static const struct crashtype crashtypes[] = { > CRASHTYPE(SLAB_FREE_DOUBLE), > CRASHTYPE(SLAB_FREE_CROSS), > CRASHTYPE(SLAB_FREE_PAGE), > + CRASHTYPE(HEAP_SPRAY), > CRASHTYPE(SOFTLOCKUP), > CRASHTYPE(HARDLOCKUP), > CRASHTYPE(SPINLOCKUP), > diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c > index 1323bc16f113..a72a241e314a 100644 > --- a/drivers/misc/lkdtm/heap.c > +++ b/drivers/misc/lkdtm/heap.c > @@ -205,6 +205,46 @@ static void ctor_a(void *region) > static void ctor_b(void *region) > { } > > +#define HEAP_SPRAY_SIZE 128 > + > +void lkdtm_HEAP_SPRAY(void) > +{ > + int *addr; > + int *spray_addrs[HEAP_SPRAY_SIZE] = { 0 }; > + unsigned long i = 0; > + > + addr = kmem_cache_alloc(a_cache, GFP_KERNEL); > + if (!addr) { > + pr_info("Unable to allocate memory in lkdtm-heap-a cache\n"); > + return; > + } > + > + *addr = 0x31337; > + kmem_cache_free(a_cache, addr); > + > + pr_info("Performing heap spraying...\n"); > + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { > + spray_addrs[i] = kmem_cache_alloc(a_cache, GFP_KERNEL); > + *spray_addrs[i] = 0x31337; > + pr_info("attempt %lu: spray alloc addr %p vs freed addr %p\n", > + i, spray_addrs[i], addr); > + if (spray_addrs[i] == addr) { > + pr_info("freed addr is reallocated!\n"); > + break; > + } > + } > + > + if (i < HEAP_SPRAY_SIZE) > + pr_info("FAIL! Heap spraying succeed :(\n"); > + else > + pr_info("OK! Heap spraying hasn't succeed :)\n"); > + > + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { > + if (spray_addrs[i]) > + kmem_cache_free(a_cache, spray_addrs[i]); > + } > +} > + > void __init lkdtm_heap_init(void) > { > double_free_cache = kmem_cache_create("lkdtm-heap-double_free", > diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h > index 8878538b2c13..dfafb4ae6f3a 100644 > --- a/drivers/misc/lkdtm/lkdtm.h > +++ b/drivers/misc/lkdtm/lkdtm.h > @@ -45,6 +45,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void); > void lkdtm_SLAB_FREE_DOUBLE(void); > void lkdtm_SLAB_FREE_CROSS(void); > void lkdtm_SLAB_FREE_PAGE(void); > +void lkdtm_HEAP_SPRAY(void); > > /* lkdtm_perms.c */ > void __init lkdtm_perms_init(void);
On Mon, Aug 17, 2020 at 01:24:37PM -0500, Eric W. Biederman wrote: > Alexander Popov <alex.popov@linux.com> writes: > > > Add a simple test for CONFIG_SLAB_QUARANTINE. > > > > It performs heap spraying that aims to reallocate the recently freed heap > > object. This technique is used for exploiting use-after-free > > vulnerabilities in the kernel code. > > > > This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying > > exploitation technique. > > > > Signed-off-by: Alexander Popov <alex.popov@linux.com> > > Why put this test in the linux kernel dump test module? > > I have no problem with tests, and I may be wrong but this > does not look like you are testing to see if heap corruption > triggers a crash dump. Which is what the rest of the tests > in lkdtm are about. Seeing if the test triggers successfully > triggers a crash dump. The scope of LKDTM has shifted a bit, and I'm fine with tests that don't cause crashes as long as they're part of testing system-wide defenses, etc. It's easier to collect similar tests together (even if they don't break the system).
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index a5e344df9166..78b7669c35eb 100644 --- a/drivers/misc/lkdtm/core.c +++ b/drivers/misc/lkdtm/core.c @@ -126,6 +126,7 @@ static const struct crashtype crashtypes[] = { CRASHTYPE(SLAB_FREE_DOUBLE), CRASHTYPE(SLAB_FREE_CROSS), CRASHTYPE(SLAB_FREE_PAGE), + CRASHTYPE(HEAP_SPRAY), CRASHTYPE(SOFTLOCKUP), CRASHTYPE(HARDLOCKUP), CRASHTYPE(SPINLOCKUP), diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c index 1323bc16f113..a72a241e314a 100644 --- a/drivers/misc/lkdtm/heap.c +++ b/drivers/misc/lkdtm/heap.c @@ -205,6 +205,46 @@ static void ctor_a(void *region) static void ctor_b(void *region) { } +#define HEAP_SPRAY_SIZE 128 + +void lkdtm_HEAP_SPRAY(void) +{ + int *addr; + int *spray_addrs[HEAP_SPRAY_SIZE] = { 0 }; + unsigned long i = 0; + + addr = kmem_cache_alloc(a_cache, GFP_KERNEL); + if (!addr) { + pr_info("Unable to allocate memory in lkdtm-heap-a cache\n"); + return; + } + + *addr = 0x31337; + kmem_cache_free(a_cache, addr); + + pr_info("Performing heap spraying...\n"); + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { + spray_addrs[i] = kmem_cache_alloc(a_cache, GFP_KERNEL); + *spray_addrs[i] = 0x31337; + pr_info("attempt %lu: spray alloc addr %p vs freed addr %p\n", + i, spray_addrs[i], addr); + if (spray_addrs[i] == addr) { + pr_info("freed addr is reallocated!\n"); + break; + } + } + + if (i < HEAP_SPRAY_SIZE) + pr_info("FAIL! Heap spraying succeed :(\n"); + else + pr_info("OK! Heap spraying hasn't succeed :)\n"); + + for (i = 0; i < HEAP_SPRAY_SIZE; i++) { + if (spray_addrs[i]) + kmem_cache_free(a_cache, spray_addrs[i]); + } +} + void __init lkdtm_heap_init(void) { double_free_cache = kmem_cache_create("lkdtm-heap-double_free", diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index 8878538b2c13..dfafb4ae6f3a 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -45,6 +45,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void); void lkdtm_SLAB_FREE_DOUBLE(void); void lkdtm_SLAB_FREE_CROSS(void); void lkdtm_SLAB_FREE_PAGE(void); +void lkdtm_HEAP_SPRAY(void); /* lkdtm_perms.c */ void __init lkdtm_perms_init(void);
Add a simple test for CONFIG_SLAB_QUARANTINE. It performs heap spraying that aims to reallocate the recently freed heap object. This technique is used for exploiting use-after-free vulnerabilities in the kernel code. This test shows that CONFIG_SLAB_QUARANTINE breaks heap spraying exploitation technique. Signed-off-by: Alexander Popov <alex.popov@linux.com> --- drivers/misc/lkdtm/core.c | 1 + drivers/misc/lkdtm/heap.c | 40 ++++++++++++++++++++++++++++++++++++++ drivers/misc/lkdtm/lkdtm.h | 1 + 3 files changed, 42 insertions(+)