From: David Howells <dhowells@redhat.com>
To: linux-security-module@vger.kernel.org
Subject: Re: [PATCH] KEYS: prevent creating a different user's keyrings
Date: Mon, 25 Sep 2017 11:54:20 +0000 [thread overview]
Message-ID: <26475.1506340460@warthog.procyon.org.uk> (raw)
In-Reply-To: <20170921220029.GB89627@gmail.com>
Eric Biggers <ebiggers3@gmail.com> wrote:
> Well, maybe. Whitelists are hard to get right, and it would be a bit ugly
> having to check the name in both add_key() and join_session_keyring(). And
> hopefully that would be everything?
Actually, having thought about it some more, I think your way is better.
> I think there's also a more fundamental problem with how keyring names work.
> If you try to join a keyring with a certain name, how are you supposed to
> know which one you're joining? There can be many keyrings that have the
> same name; and any unprivileged user can create a keyring with the name, and
> they can grant everyone SEARCH permission so that their keyring can be
> joined. So it can be the case that a user is wanting to join a particular
> keyring, but they actually get a keyring that a malicious user has crafted
> for them...
Yeah. With hindsight, I think that firstly, joinable keyrings really need
enablement and, secondly, thread, process, session, user and user-session need
to have to be non-manually-creatable.
However, I'm not sure they can be renamed, since they're searchable and
joinable by name and fixing this might break something in userspace (though I
should hope that this is unlikely).
> Also, if period ('.') is meant to be the reserved character in keyring names,
> why do most of the special names actually start with underscore ('_')?
'.' wasn't a reserved char originally.
David
WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com>
To: Eric Biggers <ebiggers3@gmail.com>
Cc: dhowells@redhat.com, keyrings@vger.kernel.org,
Michael Halcrow <mhalcrow@google.com>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org, Eric Biggers <ebiggers@google.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] KEYS: prevent creating a different user's keyrings
Date: Mon, 25 Sep 2017 12:54:20 +0100 [thread overview]
Message-ID: <26475.1506340460@warthog.procyon.org.uk> (raw)
In-Reply-To: <20170921220029.GB89627@gmail.com>
Eric Biggers <ebiggers3@gmail.com> wrote:
> Well, maybe. Whitelists are hard to get right, and it would be a bit ugly
> having to check the name in both add_key() and join_session_keyring(). And
> hopefully that would be everything?
Actually, having thought about it some more, I think your way is better.
> I think there's also a more fundamental problem with how keyring names work.
> If you try to join a keyring with a certain name, how are you supposed to
> know which one you're joining? There can be many keyrings that have the
> same name; and any unprivileged user can create a keyring with the name, and
> they can grant everyone SEARCH permission so that their keyring can be
> joined. So it can be the case that a user is wanting to join a particular
> keyring, but they actually get a keyring that a malicious user has crafted
> for them...
Yeah. With hindsight, I think that firstly, joinable keyrings really need
enablement and, secondly, thread, process, session, user and user-session need
to have to be non-manually-creatable.
However, I'm not sure they can be renamed, since they're searchable and
joinable by name and fixing this might break something in userspace (though I
should hope that this is unlikely).
> Also, if period ('.') is meant to be the reserved character in keyring names,
> why do most of the special names actually start with underscore ('_')?
'.' wasn't a reserved char originally.
David
WARNING: multiple messages have this Message-ID (diff)
From: dhowells@redhat.com (David Howells)
To: linux-security-module@vger.kernel.org
Subject: [PATCH] KEYS: prevent creating a different user's keyrings
Date: Mon, 25 Sep 2017 12:54:20 +0100 [thread overview]
Message-ID: <26475.1506340460@warthog.procyon.org.uk> (raw)
In-Reply-To: <20170921220029.GB89627@gmail.com>
Eric Biggers <ebiggers3@gmail.com> wrote:
> Well, maybe. Whitelists are hard to get right, and it would be a bit ugly
> having to check the name in both add_key() and join_session_keyring(). And
> hopefully that would be everything?
Actually, having thought about it some more, I think your way is better.
> I think there's also a more fundamental problem with how keyring names work.
> If you try to join a keyring with a certain name, how are you supposed to
> know which one you're joining? There can be many keyrings that have the
> same name; and any unprivileged user can create a keyring with the name, and
> they can grant everyone SEARCH permission so that their keyring can be
> joined. So it can be the case that a user is wanting to join a particular
> keyring, but they actually get a keyring that a malicious user has crafted
> for them...
Yeah. With hindsight, I think that firstly, joinable keyrings really need
enablement and, secondly, thread, process, session, user and user-session need
to have to be non-manually-creatable.
However, I'm not sure they can be renamed, since they're searchable and
joinable by name and fixing this might break something in userspace (though I
should hope that this is unlikely).
> Also, if period ('.') is meant to be the reserved character in keyring names,
> why do most of the special names actually start with underscore ('_')?
'.' wasn't a reserved char originally.
David
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next prev parent reply other threads:[~2017-09-25 11:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-18 18:37 [PATCH] KEYS: prevent creating a different user's keyrings Eric Biggers
2017-09-18 18:37 ` Eric Biggers
2017-09-18 18:37 ` Eric Biggers
2017-09-19 16:05 ` David Howells
2017-09-19 16:05 ` David Howells
2017-09-19 16:05 ` David Howells
2017-09-21 22:00 ` Eric Biggers
2017-09-21 22:00 ` Eric Biggers
2017-09-21 22:00 ` Eric Biggers
2017-09-25 11:54 ` David Howells [this message]
2017-09-25 11:54 ` David Howells
2017-09-25 11:54 ` David Howells
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