2019-08-16 13:37:41

by David Howells

Subject: Re: [GIT PULL] Keys: Set 4 - Key ACLs for 5.3

Mimi Zohar <[email protected]> wrote:

> Sorry for the delay.  An exception is needed for loading builtin keys
> "KEY_ALLOC_BUILT_IN" onto a keyring that is not writable by userspace.
>  The following works, but probably is not how David would handle the
> exception.

I think the attached is the right way to fix it.

load_system_certificate_list(), for example, when it creates keys does this:

key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),

marking the keyring as "possessed" in make_key_ref(). This allows the
possessor permits to be used - and that's the *only* way to use them for
internal keyrings like this because you can't link to them and you can't join
them.

David
---
diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 57be78b5fdfc..1f8f26f7bb05 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -99,7 +99,7 @@ static __init int system_trusted_keyring_init(void)
builtin_trusted_keys =
keyring_alloc(".builtin_trusted_keys",
KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
- &internal_key_acl, KEY_ALLOC_NOT_IN_QUOTA,
+ &internal_keyring_acl, KEY_ALLOC_NOT_IN_QUOTA,
NULL, NULL);
if (IS_ERR(builtin_trusted_keys))
panic("Can't allocate builtin trusted keyring\n");
diff --git a/security/keys/permission.c b/security/keys/permission.c
index fc84d9ef6239..86efd3eaf083 100644
--- a/security/keys/permission.c
+++ b/security/keys/permission.c
@@ -47,7 +47,7 @@ struct key_acl internal_keyring_acl = {
.usage = REFCOUNT_INIT(1),
.nr_ace = 2,
.aces = {
- KEY_POSSESSOR_ACE(KEY_ACE_SEARCH),
+ KEY_POSSESSOR_ACE(KEY_ACE_SEARCH | KEY_ACE_WRITE),
KEY_OWNER_ACE(KEY_ACE_VIEW | KEY_ACE_READ | KEY_ACE_SEARCH),
}
};

2019-08-21 15:52:29

by Mimi Zohar

Subject: Re: [GIT PULL] Keys: Set 4 - Key ACLs for 5.3

On Fri, 2019-08-16 at 14:36 +0100, David Howells wrote:
> Mimi Zohar <[email protected]> wrote:
>
> > Sorry for the delay.  An exception is needed for loading builtin keys
> > "KEY_ALLOC_BUILT_IN" onto a keyring that is not writable by userspace.
> >  The following works, but probably is not how David would handle the
> > exception.
>
> I think the attached is the right way to fix it.
>
> load_system_certificate_list(), for example, when it creates keys does this:
>
> key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
>
> marking the keyring as "possessed" in make_key_ref(). This allows the
> possessor permits to be used - and that's the *only* way to use them for
> internal keyrings like this because you can't link to them and you can't join
> them.

In addition, as long as additional keys still can't be added or
existing keys updated by userspace on the .builtin_trusted_keys, then
this is fine.

>
> David
> ---
> diff --git a/certs/system_keyring.c b/certs/system_keyring.c
> index 57be78b5fdfc..1f8f26f7bb05 100644
> --- a/certs/system_keyring.c
> +++ b/certs/system_keyring.c
> @@ -99,7 +99,7 @@ static __init int system_trusted_keyring_init(void)
> builtin_trusted_keys =
> keyring_alloc(".builtin_trusted_keys",
> KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
> - &internal_key_acl, KEY_ALLOC_NOT_IN_QUOTA,
> + &internal_keyring_acl, KEY_ALLOC_NOT_IN_QUOTA,
> NULL, NULL);
> if (IS_ERR(builtin_trusted_keys))
> panic("Can't allocate builtin trusted keyring\n");
> diff --git a/security/keys/permission.c b/security/keys/permission.c
> index fc84d9ef6239..86efd3eaf083 100644
> --- a/security/keys/permission.c
> +++ b/security/keys/permission.c
> @@ -47,7 +47,7 @@ struct key_acl internal_keyring_acl = {
> .usage = REFCOUNT_INIT(1),
> .nr_ace = 2,
> .aces = {
> - KEY_POSSESSOR_ACE(KEY_ACE_SEARCH),
> + KEY_POSSESSOR_ACE(KEY_ACE_SEARCH | KEY_ACE_WRITE),
> KEY_OWNER_ACE(KEY_ACE_VIEW | KEY_ACE_READ | KEY_ACE_SEARCH),
> }
> };

Thanks, David.  The builtin keys are now being loaded.

Mimi