From: Stefan Berger <stefanb@linux.ibm.com>
To: jejb@linux.ibm.com, linux-integrity@vger.kernel.org
Cc: zohar@linux.ibm.com, serge@hallyn.com,
christian.brauner@ubuntu.com, containers@lists.linux.dev,
dmitry.kasatkin@gmail.com, ebiederm@xmission.com,
krzysztof.struczynski@huawei.com, roberto.sassu@huawei.com,
mpeters@redhat.com, lhinds@redhat.com, lsturman@redhat.com,
puiterwi@redhat.com, jamjoom@us.ibm.com,
linux-kernel@vger.kernel.org, paul@paul-moore.com,
rgb@redhat.com, linux-security-module@vger.kernel.org,
jmorris@namei.org
Subject: Re: [RFC 20/20] ima: Setup securityfs_ns for IMA namespace
Date: Wed, 1 Dec 2021 13:11:15 -0500 [thread overview]
Message-ID: <f2113d60-49d3-2e2d-7dbe-b831035f96a1@linux.ibm.com> (raw)
In-Reply-To: <6599ac61289e3316bff53602a0bc5970133251aa.camel@linux.ibm.com>
On 12/1/21 12:56, James Bottomley wrote:
> On Tue, 2021-11-30 at 11:06 -0500, Stefan Berger wrote:
> [...]
>> +
>> +/*
>> + * Fix the ownership (uid/gid) of the dentry's that couldn't be set
>> at the
>> + * time of their creation because the user namespace wasn't
>> configured, yet.
>> + */
>> +static void ima_fs_ns_fixup_uid_gid(struct ima_namespace *ns)
>> +{
>> + struct inode *inode;
>> + size_t i;
>> +
>> + if (ns->file_ownership_fixes_done ||
>> + ns->user_ns->uid_map.nr_extents == 0)
>> + return;
>> +
>> + ns->file_ownership_fixes_done = true;
>> + for (i = 0; i < IMAFS_DENTRY_LAST; i++) {
>> + if (!ns->dentry[i])
>> + continue;
>> + inode = ns->dentry[i]->d_inode;
>> + inode->i_uid = make_kuid(ns->user_ns, 0);
>> + inode->i_gid = make_kgid(ns->user_ns, 0);
>> + }
>> +}
>> +
>> +/* Fix the permissions when a file is opened */
>> +int ima_fs_ns_permission(struct user_namespace *mnt_userns, struct
>> inode *inode,
>> + int mask)
>> +{
>> + ima_fs_ns_fixup_uid_gid(get_current_ns());
>> + return generic_permission(mnt_userns, inode, mask);
>> +}
>> +
>> +const struct inode_operations ima_fs_ns_inode_operations = {
>> + .lookup = simple_lookup,
>> + .permission = ima_fs_ns_permission,
>> +};
>> +
> In theory this uid/gid shifting should have already been done for you
> and all of the above code should be unnecessary. What is supposed to
> happen is that the mount of securityfs_ns in the new user namespace
> should pick up a superblock s_user_ns for that new user namespace. Now
> inode_alloc() uses i_uid_write(inode, 0) which maps back through the
> s_user_ns to obtain the owner of the user namespace.
>
> What can happen is that if you do the inode allocation before (or even
> without) writing to the uid_map file, it maps back through an empty map
> and ends up with -1 for i_uid ... is this what you're seeing?
I tried this with runc and a user namespace active mapping uid 1000 on
the host to uid 0 in the container. There I run into the problem that
all of the files and directories without the above work-around are
mapped to 'nobody', just like all the files in sysfs in this case are
also mapped to nobody. This code resolved the issue.
sh-5.1# ls -l /sys/
total 0
drwxr-xr-x. 2 nobody nobody 0 Dec 1 18:06 block
drwxr-xr-x. 28 nobody nobody 0 Dec 1 18:06 bus
drwxr-xr-x. 54 nobody nobody 0 Dec 1 18:06 class
drwxr-xr-x. 4 nobody nobody 0 Dec 1 18:06 dev
drwxr-xr-x. 15 nobody nobody 0 Dec 1 18:06 devices
drwxrwxrwt. 2 root root 40 Dec 1 18:06 firmware
drwxr-xr-x. 9 nobody nobody 0 Dec 1 18:06 fs
drwxr-xr-x. 16 nobody nobody 0 Dec 1 18:06 kernel
drwxr-xr-x. 161 nobody nobody 0 Dec 1 18:06 module
drwxr-xr-x. 3 nobody nobody 0 Dec 1 18:06 power
sh-5.1# ls -l /sys/kernel/security/
total 0
lr--r--r--. 1 nobody nobody 0 Dec 1 18:06 ima -> integrity/ima
drwxr-xr-x. 3 nobody nobody 0 Dec 1 18:06 integrity
sh-5.1# ls -l /sys/kernel/security/ima/
total 0
-r--r-----. 1 root root 0 Dec 1 18:06 ascii_runtime_measurements
-r--r-----. 1 root root 0 Dec 1 18:06 binary_runtime_measurements
-rw-------. 1 root root 0 Dec 1 18:06 policy
-r--r-----. 1 root root 0 Dec 1 18:06 runtime_measurements_count
-r--r-----. 1 root root 0 Dec 1 18:06 violations
The nobody's are obviously sufficient to cd into the directories, but
for file accesses I wanted to see root and no changes to permissions.
Stefan
>
> James
>
>
next prev parent reply other threads:[~2021-12-01 18:14 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-30 16:06 [RFC 00/20] ima: Namespace IMA with audit support in IMA-ns Stefan Berger
2021-11-30 16:06 ` [RFC 01/20] ima: Add IMA namespace support Stefan Berger
2021-11-30 16:06 ` [RFC 02/20] ima: Define ns_status for storing namespaced iint data Stefan Berger
2021-11-30 16:06 ` [RFC 03/20] ima: Namespace audit status flags Stefan Berger
2021-11-30 16:06 ` [RFC 04/20] ima: Move delayed work queue and variables into ima_namespace Stefan Berger
2021-11-30 16:06 ` [RFC 05/20] ima: Move IMA's keys queue related " Stefan Berger
2021-11-30 16:06 ` [RFC 06/20] ima: Move policy " Stefan Berger
2021-11-30 16:06 ` [RFC 07/20] ima: Move ima_htable " Stefan Berger
2021-11-30 16:06 ` [RFC 08/20] ima: Move measurement list related variables " Stefan Berger
2021-12-02 12:46 ` James Bottomley
2021-12-02 13:41 ` Stefan Berger
2021-12-02 16:29 ` James Bottomley
2021-12-02 16:45 ` Stefan Berger
2021-12-02 17:44 ` James Bottomley
2021-12-02 18:03 ` Stefan Berger
2021-12-02 20:03 ` James Bottomley
2021-11-30 16:06 ` [RFC 09/20] ima: Only accept AUDIT rules for IMA non-init_ima_ns namespaces for now Stefan Berger
2021-11-30 16:06 ` [RFC 10/20] ima: Implement hierarchical processing of file accesses Stefan Berger
2021-11-30 16:06 ` [RFC 11/20] securityfs: Prefix global variables with securityfs_ Stefan Berger
2021-11-30 16:06 ` [RFC 12/20] securityfs: Pass static variables as parameters from top level functions Stefan Berger
2021-11-30 16:06 ` [RFC 13/20] securityfs: Build securityfs_ns for namespacing support Stefan Berger
2021-12-02 13:35 ` Christian Brauner
2021-12-02 13:47 ` Stefan Berger
2021-11-30 16:06 ` [RFC 14/20] ima: Move some IMA policy and filesystem related variables into ima_namespace Stefan Berger
2021-11-30 16:06 ` [RFC 15/20] capabilities: Introduce CAP_INTEGRITY_ADMIN Stefan Berger
2021-11-30 17:27 ` Casey Schaufler
2021-11-30 17:41 ` Stefan Berger
2021-11-30 17:50 ` Casey Schaufler
2021-11-30 16:06 ` [RFC 16/20] ima: Use ns_capable() for namespace policy access Stefan Berger
2021-11-30 16:06 ` [RFC 17/20] ima: Use integrity_admin_ns_capable() to check corresponding capability Stefan Berger
2021-12-01 16:58 ` James Bottomley
2021-12-01 17:35 ` Stefan Berger
2021-12-01 19:29 ` James Bottomley
2021-12-02 7:16 ` Denis Semakin
2021-12-02 12:33 ` James Bottomley
2021-12-02 17:54 ` Stefan Berger
2021-12-02 12:59 ` Christian Brauner
2021-12-02 13:01 ` Christian Brauner
2021-12-02 15:58 ` Casey Schaufler
2021-11-30 16:06 ` [RFC 18/20] userns: Introduce a refcount variable for calling early teardown function Stefan Berger
2021-11-30 16:06 ` [RFC 19/20] ima/userns: Define early teardown function for IMA namespace Stefan Berger
2021-11-30 16:06 ` [RFC 20/20] ima: Setup securityfs_ns " Stefan Berger
2021-12-01 17:56 ` James Bottomley
2021-12-01 18:11 ` Stefan Berger [this message]
2021-12-01 19:21 ` James Bottomley
2021-12-01 20:25 ` Stefan Berger
2021-12-01 21:11 ` James Bottomley
2021-12-01 21:34 ` Stefan Berger
2021-12-01 22:01 ` James Bottomley
2021-12-01 22:09 ` Stefan Berger
2021-12-01 22:19 ` James Bottomley
2021-12-02 0:02 ` Stefan Berger
2021-12-02 13:18 ` Christian Brauner
2021-12-02 13:52 ` Stefan Berger
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