linux-kernel - Re: [PATCH v2 2/3] Teach SELinux about anonymous inodes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3e098729-dc6d-68d0-46a6-7add4fd75b11@tycho.nsa.gov>
Date:   Thu, 26 Mar 2020 13:37:36 -0400
From:   Stephen Smalley <sds@...ho.nsa.gov>
To:     Daniel Colascione <dancol@...gle.com>, timmurray@...gle.com,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, viro@...iv.linux.org.uk, paul@...l-moore.com,
        nnk@...gle.com, lokeshgidra@...gle.com
Subject: Re: [PATCH v2 2/3] Teach SELinux about anonymous inodes

On 3/25/20 7:02 PM, Daniel Colascione wrote:
> This change uses the anon_inodes and LSM infrastructure introduced in
> the previous patch to give SELinux the ability to control
> anonymous-inode files that are created using the new _secure()
> anon_inodes functions.
> 
> A SELinux policy author detects and controls these anonymous inodes by
> adding a name-based type_transition rule that assigns a new security
> type to anonymous-inode files created in some domain. The name used
> for the name-based transition is the name associated with the
> anonymous inode for file listings --- e.g., "[userfaultfd]" or
> "[perf_event]".
> 
> Example:
> 
> type uffd_t;
> type_transition sysadm_t sysadm_t : file uffd_t "[userfaultfd]";
> allow sysadm_t uffd_t:file { create };

These should use :anon_inode rather than :file since the class is no 
longer file.

> 
> (The next patch in this series is necessary for making userfaultfd
> support this new interface.  The example above is just
> for exposition.)
> 
> Signed-off-by: Daniel Colascione <dancol@...gle.com>
> ---
>   security/selinux/hooks.c            | 54 +++++++++++++++++++++++++++++
>   security/selinux/include/classmap.h |  2 ++
>   2 files changed, 56 insertions(+)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 1659b59fb5d7..b9eb45c2e4e5 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2915,6 +2915,59 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
>   	return 0;
>   }
>   
> +static int selinux_inode_init_security_anon(struct inode *inode,
> +					    const struct qstr *name,
> +					    const struct file_operations *fops,
> +					    const struct inode *context_inode)
> +{
> +	const struct task_security_struct *tsec = selinux_cred(current_cred());
> +	struct common_audit_data ad;
> +	struct inode_security_struct *isec;
> +	int rc;
> +
> +	if (unlikely(!selinux_state.initialized))
> +		return 0;
> +
> +	isec = selinux_inode(inode);
> +
> +	/*
> +	 * We only get here once per ephemeral inode.  The inode has
> +	 * been initialized via inode_alloc_security but is otherwise
> +	 * untouched.
> +	 */
> +
> +	if (context_inode) {
> +		struct inode_security_struct *context_isec =
> +			selinux_inode(context_inode);
> +		isec->sclass = context_isec->sclass;
> +		isec->sid = context_isec->sid;
> +	} else {
> +		isec->sclass = SECCLASS_ANON_INODE;
> +		rc = security_transition_sid(
> +			&selinux_state, tsec->sid, tsec->sid,
> +			SECCLASS_FILE, name, &isec->sid);

You should use isec->sclass == SECCLASS_ANON_INODE instead of 
SECCLASS_FILE here.