Add support for per-user_namespace registers of persistent per-UID kerberos caches held within the kernel. This allows the kerberos cache to be retained beyond the life of all a user's processes so that the user's cron jobs can work. The kerberos cache is envisioned as a keyring/key tree looking something like: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 big_key - A ccache blob \___ tkt12345 big_key - Another ccache blob Or possibly: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 keyring - A ccache \___ krbtgt/REDHAT.COM@REDHAT.COM big_key \___ http/REDHAT.COM@REDHAT.COM user \___ afs/REDHAT.COM@REDHAT.COM user \___ nfs/REDHAT.COM@REDHAT.COM user \___ krbtgt/KERNEL.ORG@KERNEL.ORG big_key \___ http/KERNEL.ORG@KERNEL.ORG big_key What goes into a particular Kerberos cache is entirely up to userspace. Kernel support is limited to giving you the Kerberos cache keyring that you want. The user asks for their Kerberos cache by: krb_cache = keyctl_get_krbcache(uid, dest_keyring); The uid is -1 or the user's own UID for the user's own cache or the uid of some other user's cache (requires CAP_SETUID). This permits rpc.gssd or whatever to mess with the cache. The cache returned is a keyring named "_krb.<uid>" that the possessor can read, search, clear, invalidate, unlink from and add links to. Active LSMs get a chance to rule on whether the caller is permitted to make a link. Each uid's cache keyring is created when it first accessed and is given a timeout that is extended each time this function is called so that the keyring goes away after a while. The timeout is configurable by sysctl but defaults to three days. Each user_namespace struct gets a lazily-created keyring that serves as the register. The cache keyrings are added to it. This means that standard key search and garbage collection facilities are available. The user_namespace struct's register goes away when it does and anything left in it is then automatically gc'd. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Simo Sorce <simo@redhat.com> cc: Serge E. Hallyn <serge.hallyn@ubuntu.com> cc: Eric W. Biederman <ebiederm@xmission.com>
170 lines
4.6 KiB
C
170 lines
4.6 KiB
C
/* General persistent per-UID keyrings register
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*
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* Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/user_namespace.h>
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#include "internal.h"
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unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */
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/*
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* Create the persistent keyring register for the current user namespace.
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*
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* Called with the namespace's sem locked for writing.
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*/
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static int key_create_persistent_register(struct user_namespace *ns)
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{
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struct key *reg = keyring_alloc(".persistent_register",
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KUIDT_INIT(0), KGIDT_INIT(0),
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current_cred(),
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ),
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KEY_ALLOC_NOT_IN_QUOTA, NULL);
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if (IS_ERR(reg))
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return PTR_ERR(reg);
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ns->persistent_keyring_register = reg;
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return 0;
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}
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/*
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* Create the persistent keyring for the specified user.
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*
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* Called with the namespace's sem locked for writing.
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*/
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static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid,
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struct keyring_index_key *index_key)
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{
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struct key *persistent;
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key_ref_t reg_ref, persistent_ref;
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if (!ns->persistent_keyring_register) {
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long err = key_create_persistent_register(ns);
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if (err < 0)
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return ERR_PTR(err);
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} else {
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reg_ref = make_key_ref(ns->persistent_keyring_register, true);
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persistent_ref = find_key_to_update(reg_ref, index_key);
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if (persistent_ref)
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return persistent_ref;
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}
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persistent = keyring_alloc(index_key->description,
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uid, INVALID_GID, current_cred(),
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ),
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KEY_ALLOC_NOT_IN_QUOTA,
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ns->persistent_keyring_register);
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if (IS_ERR(persistent))
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return ERR_CAST(persistent);
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return make_key_ref(persistent, true);
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}
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/*
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* Get the persistent keyring for a specific UID and link it to the nominated
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* keyring.
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*/
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static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
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key_ref_t dest_ref)
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{
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struct keyring_index_key index_key;
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struct key *persistent;
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key_ref_t reg_ref, persistent_ref;
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char buf[32];
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long ret;
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/* Look in the register if it exists */
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index_key.type = &key_type_keyring;
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index_key.description = buf;
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index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));
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if (ns->persistent_keyring_register) {
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reg_ref = make_key_ref(ns->persistent_keyring_register, true);
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down_read(&ns->persistent_keyring_register_sem);
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persistent_ref = find_key_to_update(reg_ref, &index_key);
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up_read(&ns->persistent_keyring_register_sem);
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if (persistent_ref)
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goto found;
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}
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/* It wasn't in the register, so we'll need to create it. We might
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* also need to create the register.
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*/
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down_write(&ns->persistent_keyring_register_sem);
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persistent_ref = key_create_persistent(ns, uid, &index_key);
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up_write(&ns->persistent_keyring_register_sem);
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if (!IS_ERR(persistent_ref))
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goto found;
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return PTR_ERR(persistent_ref);
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found:
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ret = key_task_permission(persistent_ref, current_cred(), KEY_LINK);
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if (ret == 0) {
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persistent = key_ref_to_ptr(persistent_ref);
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ret = key_link(key_ref_to_ptr(dest_ref), persistent);
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if (ret == 0) {
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key_set_timeout(persistent, persistent_keyring_expiry);
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ret = persistent->serial;
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}
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}
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key_ref_put(persistent_ref);
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return ret;
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}
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/*
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* Get the persistent keyring for a specific UID and link it to the nominated
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* keyring.
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*/
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long keyctl_get_persistent(uid_t _uid, key_serial_t destid)
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{
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struct user_namespace *ns = current_user_ns();
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key_ref_t dest_ref;
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kuid_t uid;
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long ret;
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/* -1 indicates the current user */
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if (_uid == (uid_t)-1) {
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uid = current_uid();
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} else {
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uid = make_kuid(ns, _uid);
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if (!uid_valid(uid))
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return -EINVAL;
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/* You can only see your own persistent cache if you're not
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* sufficiently privileged.
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*/
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if (uid_eq(uid, current_uid()) &&
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uid_eq(uid, current_suid()) &&
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uid_eq(uid, current_euid()) &&
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uid_eq(uid, current_fsuid()) &&
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!ns_capable(ns, CAP_SETUID))
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return -EPERM;
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}
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/* There must be a destination keyring */
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dest_ref = lookup_user_key(destid, KEY_LOOKUP_CREATE, KEY_WRITE);
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if (IS_ERR(dest_ref))
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return PTR_ERR(dest_ref);
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if (key_ref_to_ptr(dest_ref)->type != &key_type_keyring) {
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ret = -ENOTDIR;
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goto out_put_dest;
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}
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ret = key_get_persistent(ns, uid, dest_ref);
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out_put_dest:
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key_ref_put(dest_ref);
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return ret;
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}
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