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

From: David Howells <dhowells@redhat.com>
To: Mimi Zohar <zohar@linux.ibm.com>
Cc: dhowells@redhat.com,
	Linus Torvalds <torvalds@linux-foundation.org>,
	James Morris <jmorris@namei.org>,
	keyrings@vger.kernel.org, Netdev <netdev@vger.kernel.org>,
	linux-nfs@vger.kernel.org, CIFS <linux-cifs@vger.kernel.org>,
	linux-afs@lists.infradead.org,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-integrity@vger.kernel.org,
	LSM List <linux-security-module@vger.kernel.org>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] Keys: Set 4 - Key ACLs for 5.3
Date: Fri, 16 Aug 2019 13:36:42 +0000	[thread overview]
Message-ID: <23498.1565962602@warthog.procyon.org.uk> (raw)
In-Reply-To: <1562814435.4014.11.camel@linux.ibm.com>

Mimi Zohar <zohar@linux.ibm.com> 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),
 	}
 };
