Re: [PATCH] Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve fromgranting privs

[Kees Cook]

On Thu, Jan 12, 2012 at 6:12 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> With this set, a lot of dangerous operations (chroot, unshare, etc)
> become a lot less dangerous because there is no possibility of
> subverting privileged binaries.
>
> This patch completely breaks apparmor.  Someone who understands (and
> uses) apparmor should fix it or at least give me a hint.
>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> [....]
> diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
> index c1e18ba..7f480b7 100644
> --- a/security/apparmor/domain.c
> +++ b/security/apparmor/domain.c
> @@ -360,6 +360,9 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>        if (bprm->cred_prepared)
>                return 0;
>
> +       /* XXX: someone who understands apparmor needs to fix this. */
> +       BUG_ON(bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS);
> +
>        cxt = bprm->cred->security;
>        BUG_ON(!cxt);
>

Since apparmor_bprm_set_creds() calls cap_bprm_set_creds() already[1],
I think AppArmor needs no changes at all, but John will know better.
:)

-Kees

[1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=security/apparmor/domain.c;h=c1e18ba5bdc09c65d259ad4bd9f374ef04dffd2f;hb=HEAD#l356

-- 
Kees Cook
ChromeOS Security
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