* [PATCH] apparmor: enforce nullbyte at end of tag string
@ 2019-05-28 15:32 Jann Horn
2019-05-28 19:05 ` John Johansen
0 siblings, 1 reply; 2+ messages in thread
From: Jann Horn @ 2019-05-28 15:32 UTC (permalink / raw)
To: John Johansen, jannh; +Cc: Serge E. Hallyn, linux-security-module, linux-kernel
A packed AppArmor policy contains null-terminated tag strings that are read
by unpack_nameX(). However, unpack_nameX() uses string functions on them
without ensuring that they are actually null-terminated, potentially
leading to out-of-bounds accesses.
Make sure that the tag string is null-terminated before passing it to
strcmp().
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
---
Warning: The existence of this bug has not been verified at runtime, and
the patch is compile-tested only. I noticed this while browsing through
the code, but didn't want to spend the time necessary to figure out how
to actually test this at runtime.
security/apparmor/policy_unpack.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
index f6c2bcb2ab14..33041c4fb69f 100644
--- a/security/apparmor/policy_unpack.c
+++ b/security/apparmor/policy_unpack.c
@@ -276,7 +276,7 @@ static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name)
char *tag = NULL;
size_t size = unpack_u16_chunk(e, &tag);
/* if a name is specified it must match. otherwise skip tag */
- if (name && (!size || strcmp(name, tag)))
+ if (name && (!size || tag[size-1] != '\0' || strcmp(name, tag)))
goto fail;
} else if (name) {
/* if a name is specified and there is no name tag fail */
--
2.22.0.rc1.257.g3120a18244-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] apparmor: enforce nullbyte at end of tag string
2019-05-28 15:32 [PATCH] apparmor: enforce nullbyte at end of tag string Jann Horn
@ 2019-05-28 19:05 ` John Johansen
0 siblings, 0 replies; 2+ messages in thread
From: John Johansen @ 2019-05-28 19:05 UTC (permalink / raw)
To: Jann Horn; +Cc: Serge E. Hallyn, linux-security-module, linux-kernel
On 5/28/19 8:32 AM, Jann Horn wrote:
> A packed AppArmor policy contains null-terminated tag strings that are read
> by unpack_nameX(). However, unpack_nameX() uses string functions on them
> without ensuring that they are actually null-terminated, potentially
> leading to out-of-bounds accesses.
>
> Make sure that the tag string is null-terminated before passing it to
> strcmp().
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jann Horn <jannh@google.com>
gah! yes!
Acked-by: John Johansen <john.johansen@canonical.com>
> ---
> Warning: The existence of this bug has not been verified at runtime, and
> the patch is compile-tested only. I noticed this while browsing through
> the code, but didn't want to spend the time necessary to figure out how
> to actually test this at runtime.
>
>
> security/apparmor/policy_unpack.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
> index f6c2bcb2ab14..33041c4fb69f 100644
> --- a/security/apparmor/policy_unpack.c
> +++ b/security/apparmor/policy_unpack.c
> @@ -276,7 +276,7 @@ static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name)
> char *tag = NULL;
> size_t size = unpack_u16_chunk(e, &tag);
> /* if a name is specified it must match. otherwise skip tag */
> - if (name && (!size || strcmp(name, tag)))
> + if (name && (!size || tag[size-1] != '\0' || strcmp(name, tag)))
> goto fail;
> } else if (name) {
> /* if a name is specified and there is no name tag fail */
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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