From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTP id 983845A026F for ; Wed, 16 Aug 2023 11:12:23 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692177142; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=mAVarNZL6bxI3c8YkMQgLT7IMhLLrd8WcDjorjIuN9s=; b=Acc7jxGNgudqtqOlhIqxIBNJz+f3+pdP455xjmD+acOT3vzrPtGOr1nx88nJzcFY9DkrCf UamfbuiuMptH1K65kP+ezCaaUNdlmVHsoj4k9QiIrlmlMoiyjd6faxXdFBh0mQpAlZcsr1 Felq7UnfuLwc22RzuiFaYMsqDBuQCfQ= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-662-XV023-MvNzK3kHO24JijcQ-1; Wed, 16 Aug 2023 05:12:21 -0400 X-MC-Unique: XV023-MvNzK3kHO24JijcQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2FD21380610F; Wed, 16 Aug 2023 09:12:21 +0000 (UTC) Received: from localhost (unknown [10.42.28.15]) by smtp.corp.redhat.com (Postfix) with ESMTP id DD55A40C207A; Wed, 16 Aug 2023 09:12:20 +0000 (UTC) Date: Wed, 16 Aug 2023 10:12:20 +0100 From: "Richard W.M. Jones" To: Stefano Brivio Subject: Re: [PATCH 7/7] selinux: Fix domain transitions for typical commands pasta might run Message-ID: <20230816091220.GG7636@redhat.com> References: <20230816060038.870746-1-sbrivio@redhat.com> <20230816060038.870746-8-sbrivio@redhat.com> MIME-Version: 1.0 In-Reply-To: <20230816060038.870746-8-sbrivio@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Message-ID-Hash: GVXVVXI5QQRGWTZLEIQBEU6PPXBFRASW X-Message-ID-Hash: GVXVVXI5QQRGWTZLEIQBEU6PPXBFRASW X-MailFrom: rjones@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top, David Gibson X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Wed, Aug 16, 2023 at 08:00:38AM +0200, Stefano Brivio wrote: > ...now it gets ugly. If we use pasta without an existing target > namespace, and run commands directly or spawn a shell, and keep > the pasta_t domain when we do, they won't be able to do much: a > shell might even start, but it's not going to be usable, or to > even display a prompt. > > Ideally, pasta should behave like a shell when it spawns a command: > start as unconfined_t and automatically transition to whatever > domain is associated in the specific policy for that command. But > we can't run as unconfined_t, of course. > > It would seem natural to switch to unconfined_t "just before", so > that the default transitions happen. But transitions can only happen > when we execvp(), and that's one single transition -- not two. > > That is, this approach would work for: > > pasta -- sh -c 'ip address show' > > but not for: > > pasta -- ip address show > > If we configure a transition to unconfined_t when we run ip(8), we'll > really try to start that as unconfined_t -- but unconfined_t isn't > allowed as entrypoint for ip(8) itself, and execvp() will fail. > > However, there aren't many different types of binaries pasta might > commonly run -- for example, we're unlikely to see pasta used to run > a mount(8) command. > > Explicitly set up domain transition for common stuff -- switching to > unconfined_t for bin_t and shells works just fine, ip(8), ping(8), > arping(8) and similar need a different treatment. > > While at it, allow commands we spawn to inherit resource limits and > signal masks, because that's what happens by default, and don't > require AT_SECURE sanitisation of the environment (because that > won't happen by default). Slightly unrelated: we also need to > explicitly allow pasta_t to use TTYs, not just PTYs, otherwise > we can't keep stdin and stdout open for shells. > > Signed-off-by: Stefano Brivio > --- > contrib/selinux/pasta.te | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/contrib/selinux/pasta.te b/contrib/selinux/pasta.te > index 31e82dc..c37a847 100644 > --- a/contrib/selinux/pasta.te > +++ b/contrib/selinux/pasta.te > @@ -51,6 +51,7 @@ require { > type tun_tap_device_t; > type sysctl_net_t; > class tun_socket create; > + type user_tty_device_t; > > attribute port_type; > type port_t; > @@ -77,6 +78,11 @@ require { > type kernel_t; > class process setpgid; > type shell_exec_t; > + type ifconfig_exec_t; > + type netutils_exec_t; > + type ping_exec_t; > + type ifconfig_t; > + type ping_t; > type init_t; > > class capability { sys_tty_config setuid setgid }; > @@ -111,7 +117,12 @@ allow pasta_t self:user_namespace create; > auth_read_passwd_file(pasta_t) > sssd_search_lib(pasta_t) > > -allow pasta_t bin_t:file { execute execute_no_trans map }; > +domain_auto_trans(pasta_t, bin_t, unconfined_t); > +domain_auto_trans(pasta_t, shell_exec_t, unconfined_t); > +domain_auto_trans(pasta_t, ifconfig_exec_t, ifconfig_t); > +domain_auto_trans(pasta_t, netutils_exec_t, netutils_t); > +domain_auto_trans(pasta_t, ping_exec_t, ping_t); > + > allow pasta_t nsfs_t:file { open read }; > > allow pasta_t user_home_t:dir getattr; > @@ -192,3 +203,8 @@ allow pasta_t nsfs_t:file read; > allow pasta_t net_conf_t:lnk_file read; > allow pasta_t proc_net_t:lnk_file read; > > +allow pasta_t unconfined_t:process { noatsecure rlimitinh siginh }; > +allow pasta_t ifconfig_t:process { noatsecure rlimitinh siginh }; > +allow pasta_t netutils_t:process { noatsecure rlimitinh siginh }; > +allow pasta_t ping_t:process { noatsecure rlimitinh siginh }; > +allow pasta_t user_tty_device_t:chr_file { append read write }; No idea about this one, probably best to ask someone from the SELinux group at Red Hat about it ... Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top