/* Management of a process's keyrings
*
* Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/user_namespace.h>
#include <asm/uaccess.h>
#include "internal.h"
/* session keyring create vs join semaphore */
static DEFINE_MUTEX(key_session_mutex);
/* user keyring creation semaphore */
static DEFINE_MUTEX(key_user_keyring_mutex);
/* the root user's tracking struct */
struct key_user root_key_user = {
.usage = ATOMIC_INIT(3),
.cons_lock = __MUTEX_INITIALIZER(root_key_user.cons_lock),
.lock = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
.nkeys = ATOMIC_INIT(2),
.nikeys = ATOMIC_INIT(2),
.uid = 0,
.user_ns = &init_user_ns,
};
/*****************************************************************************/
/*
* install user and user session keyrings for a particular UID
*/
int install_user_keyrings(void)
{
struct user_struct *user;
const struct cred *cred;
struct key *uid_keyring, *session_keyring;
char buf[20];
int ret;
cred = current_cred();
user = cred->user;
kenter("%p{%u}", user, user->uid);
if (user->uid_keyring) {
kleave(" = 0 [exist]");
return 0;
}
mutex_lock(&key_user_keyring_mutex);
ret = 0;
if (!user->uid_keyring) {
/* get the UID-specific keyring
* - there may be one in existence already as it may have been
* pinned by a session, but the user_struct pointing to it
* may have been destroyed by setuid */
sprintf(buf, "_uid.%u", user->uid);
uid_keyring = find_keyring_by_name(buf, true);
if (IS_ERR(uid_keyring)) {
uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1,
cred, KEY_ALLOC_IN_QUOTA,
NULL);
if (IS_ERR(uid_keyring)) {
ret = PTR_ERR(uid_keyring);
goto error;
}
}
/* get a default session keyring (which might also exist
* already) */
sprintf(buf, "_uid_ses.%u", user->uid);
session_keyring = find_keyring_by_name(buf, true);
if (IS_ERR(session_keyring)) {
session_keyring =
keyring_alloc(buf, user->uid, (gid_t) -1,
cred, KEY_ALLOC_IN_QUOTA, NULL);
if (IS_ERR(session_keyring)) {
ret = PTR_ERR(session_keyring);
goto error_release;
}
/* we install a link from the user session keyring to
* the user keyring */
ret = key_link(session_keyring, uid_keyring);
if (ret < 0)
goto error_release_both;
}
/* install the keyrings */
user->uid_keyring = uid_keyring;
user->session_keyring = session_keyring;
}
mutex_unlock(&key_user_keyring_mutex);
kleave(" = 0");
return 0;
error_release_both:
key_put(session_keyring);
error_release:
key_put(uid_keyring);
error:
mutex_unlock(&key_user_keyring_mutex);
kleave(" = %d", ret);
return ret;
}
/*
* install a fresh thread keyring directly to new credentials
*/
int install_thread_keyring_to_cred(struct cred *new)
{
struct key *keyring;
keyring = keyring_alloc("_tid", new->uid, new->gid, new,
KEY_ALLOC_QUOTA_OVERRUN, NULL);
if (IS_ERR(keyring))
return PTR_ERR(keyring);
new->thread_keyring = keyring;
return 0;
}
/*
* install a fresh thread keyring, discarding the old one
*/
static int install_thread_keyring(void)
{
struct cred *new;
int ret;
new = prepare_creds();
if (!new)
return -ENOMEM;
BUG_ON(new->thread_keyring);
ret = install_thread_keyring_to_cred(new);
if (ret < 0) {
abort_creds(new);
return ret;
}
return commit_creds(new);
}
/*
* install a process keyring directly to a credentials struct
* - returns -EEXIST if there was already a process keyring, 0 if one installed,
* and other -ve on any other error
*/
int install_process_keyring_to_cred(struct cred *new)
{
struct key *keyring;
int ret;
if (new->tgcred->process_keyring)
return -EEXIST;
keyring = keyring_alloc("_pid", new->uid, new->gid,
new, KEY_ALLOC_QUOTA_OVERRUN, NULL);
if (IS_ERR(keyring))
return PTR_ERR(keyring);
spin_lock_irq(&new->tgcred->lock);
if (!new->tgcred->process_keyring) {
new->tgcred->process_keyring = keyring;
keyring = NULL;
ret = 0;
} else {
ret = -EEXIST;
}
spin_unlock_irq(&new->tgcred->lock);
key_put(keyring);
return ret;
}
/*
* make sure a process keyring is installed
* - we
*/
static int install_process_keyring(void)
{
struct cred *new;
int ret;
new = prepare_creds();
if (!new)
return -ENOMEM;
ret = install_process_keyring_to_cred(new);
if (ret < 0) {
abort_creds(new);
return ret != -EEXIST ?: 0;
}
return commit_creds(new);
}
/*
* install a session keyring directly to a credentials struct
*/
static int install_session_keyring_to_cred(struct cred *cred,
struct key *keyring)
{
unsigned long flags;
struct key *old;
might_sleep();
/* create an empty session keyring */
if (!keyring) {
flags = KEY_ALLOC_QUOTA_OVERRUN;
if (cred->tgcred->session_keyring)
flags = KEY_ALLOC_IN_QUOTA;
keyring = keyring_alloc("_ses", cred->uid, cred->gid,
cred, flags, NULL);
if (IS_ERR(keyring))
return PTR_ERR(keyring);
} else {
atomic_inc(&keyring->usage);
}
/* install the keyring */
spin_lock_irq(&cred->tgcred->lock);
old = cred->tgcred->session_keyring;
rcu_assign_pointer(cred->tgcred->session_keyring, keyring);
spin_unlock_irq(&cred->tgcred->lock);
/* we're using RCU on the pointer, but there's no point synchronising
* on it if it didn't previously point to anything */
if (old) {
synchronize_rcu();
key_put(old);
}
return 0;
}
/*
* install a session keyring, discarding the old one
* - if a keyring is not supplied, an empty one is invented
*/
static int install_session_keyring(struct key *keyring)
{
struct cred *new;
int ret;
new = prepare_creds();
if (!new)
return -ENOMEM;
ret = install_session_keyring_to_cred(new, NULL);
if (ret < 0) {
abort_creds(new);
return ret;
}
return commit_creds(new);
}
/*****************************************************************************/
/*
* the filesystem user ID changed
*/
void key_fsuid_changed(struct task_struct *tsk)
{
/* update the ownership of the thread keyring */
BUG_ON(!tsk->cred);
if (tsk->cred->thread_keyring) {
down_write(&tsk->cred->thread_keyring->sem);
tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
up_write(&tsk->cred->thread_keyring->sem);
}
} /* end key_fsuid_changed() */
/*****************************************************************************/
/*
* the filesystem group ID changed
*/
void key_fsgid_changed(struct task_struct *tsk)
{
/* update the ownership of the thread keyring */
BUG_ON(!tsk->cred);
if (tsk->cred->thread_keyring) {
down_write(&tsk->cred->thread_keyring->sem);
tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
up_write(&tsk->cred->thread_keyring->sem);
}
} /* end key_fsgid_changed() */
/*****************************************************************************/
/*
* search the process keyrings for the first matching key
* - we use the supplied match function to see if the description (or other
* feature of interest) matches
* - we return -EAGAIN if we didn't find any matching key
* - we return -ENOKEY if we found only negative matching keys
*/
key_ref_t search_process_keyrings(struct key_type *type,
const void *description,
key_match_func_t match,
const struct cred *cred)
{
struct request_key_auth *rka;
key_ref_t key_ref, ret, err;
might_sleep();
/* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
* searchable, but we failed to find a key or we found a negative key;
* otherwise we want to return a sample error (probably -EACCES) if
* none of the keyrings were searchable
*
* in terms of priority: success > -ENOKEY > -EAGAIN > other error
*/
key_ref = NULL;
ret = NULL;
err = ERR_PTR(-EAGAIN);
/* search the thread keyring first */
if (cred->thread_keyring) {
key_ref = keyring_search_aux(
make_key_ref(cred->thread_keyring, 1),
cred, type, description, match);
if (!IS_ERR(key_ref))
goto found;
switch (PTR_ERR(key_ref)) {
case -EAGAIN: /* no key */
if (ret)
break;
case -ENOKEY: /* negative key */
ret = key_ref;
break;
default:
err = key_ref;
break;
}
}
/* search the process keyring second */
if (cred->tgcred->process_keyring) {
key_ref = keyring_search_aux(
make_key_ref(cred->tgcred->process_keyring, 1),
cred, type, description, match);
if (!IS_ERR(key_ref))
goto found;
switch (PTR_ERR(key_ref)) {
case -EAGAIN: /* no key */
if (ret)
break;
case -ENOKEY: /* negative key */
ret = key_ref;
break;
default:
err = key_ref;
break;
}
}
/* search the session keyring */
if (cred->tgcred->session_keyring) {
rcu_read_lock();
key_ref = keyring_search_aux(
make_key_ref(rcu_dereference(
cred->tgcred->session_keyring),
1),
cred, type, description, match);
rcu_read_unlock();
if (!IS_ERR(key_ref))
goto found;
switch (PTR_ERR(key_ref)) {
case -EAGAIN: /* no key */
if (ret)
break;
case -ENOKEY: /* negative key */
ret = key_ref;
break;
default:
err = key_ref;
break;
}
}
/* or search the user-session keyring */
else if (cred->user->session_keyring) {
key_ref = keyring_search_aux(
make_key_ref(cred->user->session_keyring, 1),
cred, type, description, match);
if (!IS_ERR(key_ref))
goto found;
switch (PTR_ERR(key_ref)) {
case -EAGAIN: /* no key */
if (ret)
break;
case -ENOKEY: /* negative key */
ret = key_ref;
break;
default:
err = key_ref;
break;
}
}
/* if this process has an instantiation authorisation key, then we also
* search the keyrings of the process mentioned there
* - we don't permit access to request_key auth keys via this method
*/
if (cred->request_key_auth &&
cred == current_cred() &&
type != &key_type_request_key_auth
) {
/* defend against the auth key being revoked */
down_read(&cred->request_key_auth->sem);
if (key_validate(cred->request_key_auth) == 0) {
rka = cred->request_key_auth->payload.data;
key_ref = search_process_keyrings(type, description,
match, rka->cred);
up_read(&cred->request_key_auth->sem);
if (!IS_ERR(key_ref))
goto found;
switch (PTR_ERR(key_ref)) {
case -EAGAIN: /* no key */
if (ret)
break;
case -ENOKEY: /* negative key */
ret = key_ref;
break;
default:
err = key_ref;
break;
}
} else {
up_read(&cred->request_key_auth->sem);
}
}
/* no key - decide on the error we're going to go for */
key_ref = ret ? ret : err;
found:
return key_ref;
} /* end search_process_keyrings() */
/*****************************************************************************/
/*
* see if the key we're looking at is the target key
*/
static int lookup_user_key_possessed(const struct key *key, const void *target)
{
return key == target;
} /* end lookup_user_key_possessed() */
/*****************************************************************************/
/*
* lookup a key given a key ID from userspace with a given permissions mask
* - don't create special keyrings unless so requested
* - partially constructed keys aren't found unless requested
*/
key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
key_perm_t perm)
{
struct request_key_auth *rka;
const struct cred *cred;
struct key *key;
key_ref_t key_ref, skey_ref;
int ret;
try_again:
cred = get_current_cred();
key_ref = ERR_PTR(-ENOKEY);
switch (id) {
case KEY_SPEC_THREAD_KEYRING:
if (!cred->thread_keyring) {
if (!create)
goto error;
ret = install_thread_keyring();
if (ret < 0) {
key = ERR_PTR(ret);
goto error;
}
goto reget_creds;
}
key = cred->thread_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_PROCESS_KEYRING:
if (!cred->tgcred->process_keyring) {
if (!create)
goto error;
ret = install_process_keyring();
if (ret < 0) {
key = ERR_PTR(ret);
goto error;
}
goto reget_creds;
}
key = cred->tgcred->process_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_SESSION_KEYRING:
if (!cred->tgcred->session_keyring) {
/* always install a session keyring upon access if one
* doesn't exist yet */
ret = install_user_keyrings();
if (ret < 0)
goto error;
ret = install_session_keyring(
cred->user->session_keyring);
if (ret < 0)
goto error;
goto reget_creds;
}
rcu_read_lock();
key = rcu_dereference(cred->tgcred->session_keyring);
atomic_inc(&key->usage);
rcu_read_unlock();
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_USER_KEYRING:
if (!cred->user->uid_keyring) {
ret = install_user_keyrings();
if (ret < 0)
goto error;
}
key = cred->user->uid_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_USER_SESSION_KEYRING:
if (!cred->user->session_keyring) {
ret = install_user_keyrings();
if (ret < 0)
goto error;
}
key = cred->user->session_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_GROUP_KEYRING:
/* group keyrings are not yet supported */
key = ERR_PTR(-EINVAL);
goto error;
case KEY_SPEC_REQKEY_AUTH_KEY:
key = cred->request_key_auth;
if (!key)
goto error;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_REQUESTOR_KEYRING:
if (!cred->request_key_auth)
goto error;
down_read(&cred->request_key_auth->sem);
if (cred->request_key_auth->flags & KEY_FLAG_REVOKED) {
key_ref = ERR_PTR(-EKEYREVOKED);
key = NULL;
} else {
rka = cred->request_key_auth->payload.data;
key = rka->dest_keyring;
atomic_inc(&key->usage);
}
up_read(&cred->request_key_auth->sem);
if (!key)
goto error;
key_ref = make_key_ref(key, 1);
break;
default:
key_ref = ERR_PTR(-EINVAL);
if (id < 1)
goto error;
key = key_lookup(id);
if (IS_ERR(key)) {
key_ref = ERR_CAST(key);
goto error;
}
key_ref = make_key_ref(key, 0);
/* check to see if we possess the key */
skey_ref = search_process_keyrings(key->type, key,
lookup_user_key_possessed,
cred);
if (!IS_ERR(skey_ref)) {
key_put(key);
key_ref = skey_ref;
}
break;
}
if (!partial) {
ret = wait_for_key_construction(key, true);
switch (ret) {
case -ERESTARTSYS:
goto invalid_key;
default:
if (perm)
goto invalid_key;
case 0:
break;
}
} else if (perm) {
ret = key_validate(key);
if (ret < 0)
goto invalid_key;
}
ret = -EIO;
if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
goto invalid_key;
/* check the permissions */
ret = key_task_permission(key_ref, cred, perm);
if (ret < 0)
goto invalid_key;
error:
put_cred(cred);
return key_ref;
invalid_key:
key_ref_put(key_ref);
key_ref = ERR_PTR(ret);
goto error;
/* if we attempted to install a keyring, then it may have caused new
* creds to be installed */
reget_creds:
put_cred(cred);
goto try_again;
} /* end lookup_user_key() */
/*****************************************************************************/
/*
* join the named keyring as the session keyring if possible, or attempt to
* create a new one of that name if not
* - if the name is NULL, an empty anonymous keyring is installed instead
* - named session keyring joining is done with a semaphore held
*/
long join_session_keyring(const char *name)
{
const struct cred *old;
struct cred *new;
struct key *keyring;
long ret, serial;
/* only permit this if there's a single thread in the thread group -
* this avoids us having to adjust the creds on all threads and risking
* ENOMEM */
if (!is_single_threaded(current))
return -EMLINK;
new = prepare_creds();
if (!new)
return -ENOMEM;
old = current_cred();
/* if no name is provided, install an anonymous keyring */
if (!name) {
ret = install_session_keyring_to_cred(new, NULL);
if (ret < 0)
goto error;
serial = new->tgcred->session_keyring->serial;
ret = commit_creds(new);
if (ret == 0)
ret = serial;
goto okay;
}
/* allow the user to join or create a named keyring */
mutex_lock(&key_session_mutex);
/* look for an existing keyring of this name */
keyring = find_keyring_by_name(name, false);
if (PTR_ERR(keyring) == -ENOKEY) {
/* not found - try and create a new one */
keyring = keyring_alloc(name, old->uid, old->gid, old,
KEY_ALLOC_IN_QUOTA, NULL);
if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
goto error2;
}
} else if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
goto error2;
}
/* we've got a keyring - now to install it */
ret = install_session_keyring_to_cred(new, keyring);
if (ret < 0)
goto error2;
commit_creds(new);
mutex_unlock(&key_session_mutex);
ret = keyring->serial;
key_put(keyring);
okay:
return ret;
error2:
mutex_unlock(&key_session_mutex);
error:
abort_creds(new);
return ret;
}
