/* request_key.c: request a key from userspace
*
* Copyright (C) 2004-5 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.
*
* See Documentation/keys-request-key.txt
*/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/err.h>
#include <linux/keyctl.h>
#include "internal.h"
struct key_construction {
struct list_head link; /* link in construction queue */
struct key *key; /* key being constructed */
};
/* when waiting for someone else's keys, you get added to this */
DECLARE_WAIT_QUEUE_HEAD(request_key_conswq);
/*****************************************************************************/
/*
* request userspace finish the construction of a key
* - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
*/
static int call_sbin_request_key(struct key *key,
struct key *authkey,
const char *op)
{
struct task_struct *tsk = current;
key_serial_t prkey, sskey;
struct key *keyring;
char *argv[9], *envp[3], uid_str[12], gid_str[12];
char key_str[12], keyring_str[3][12];
char desc[20];
int ret, i;
kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
/* allocate a new session keyring */
sprintf(desc, "_req.%u", key->serial);
keyring = keyring_alloc(desc, current->fsuid, current->fsgid, 1, NULL);
if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
goto error_alloc;
}
/* attach the auth key to the session keyring */
ret = __key_link(keyring, authkey);
if (ret < 0)
goto error_link;
/* record the UID and GID */
sprintf(uid_str, "%d", current->fsuid);
sprintf(gid_str, "%d", current->fsgid);
/* we say which key is under construction */
sprintf(key_str, "%d", key->serial);
/* we specify the process's default keyrings */
sprintf(keyring_str[0], "%d",
tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
prkey = 0;
if (tsk->signal->process_keyring)
prkey = tsk->signal->process_keyring->serial;
sprintf(keyring_str[1], "%d", prkey);
if (tsk->signal->session_keyring) {
rcu_read_lock();
sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
rcu_read_unlock();
}
else {
sskey = tsk->user->session_keyring->serial;
}
sprintf(keyring_str[2], "%d", sskey);
/* set up a minimal environment */
i = 0;
envp[i++] = "HOME=/";
envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
envp[i] = NULL;
/* set up the argument list */
i = 0;
argv[i++] = "/sbin/request-key";
argv[i++] = (char *) op;
argv[i++] = key_str;
argv[i++] = uid_str;
argv[i++] = gid_str;
argv[i++] = keyring_str[0];
argv[i++] = keyring_str[1];
argv[i++] = keyring_str[2];
argv[i] = NULL;
/* do it */
ret = call_usermodehelper_keys(argv[0], argv, envp, keyring, 1);
error_link:
key_put(keyring);
error_alloc:
kleave(" = %d", ret);
return ret;
} /* end call_sbin_request_key() */
/*****************************************************************************/
/*
* call out to userspace for the key
* - called with the construction sem held, but the sem is dropped here
* - we ignore program failure and go on key status instead
*/
static struct key *__request_key_construction(struct key_type *type,
const char *description,
const char *callout_info)
{
request_key_actor_t actor;
struct key_construction cons;
struct timespec now;
struct key *key, *authkey;
int ret, negated;
kenter("%s,%s,%s", type->name, description, callout_info);
/* create a key and add it to the queue */
key = key_alloc(type, description,
current->fsuid, current->fsgid, KEY_POS_ALL, 0);
if (IS_ERR(key))
goto alloc_failed;
set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
cons.key = key;
list_add_tail(&cons.link, &key->user->consq);
/* we drop the construction sem here on behalf of the caller */
up_write(&key_construction_sem);
/* allocate an authorisation key */
authkey = request_key_auth_new(key, callout_info);
if (IS_ERR(authkey)) {
ret = PTR_ERR(authkey);
authkey = NULL;
goto alloc_authkey_failed;
}
/* make the call */
actor = call_sbin_request_key;
if (type->request_key)
actor = type->request_key;
ret = actor(key, authkey, "create");
if (ret < 0)
goto request_failed;
/* if the key wasn't instantiated, then we want to give an error */
ret = -ENOKEY;
if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
goto request_failed;
key_revoke(authkey);
key_put(authkey);
down_write(&key_construction_sem);
list_del(&cons.link);
up_write(&key_construction_sem);
/* also give an error if the key was negatively instantiated */
check_not_negative:
if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
key_put(key);
key = ERR_PTR(-ENOKEY);
}
out:
kleave(" = %p", key);
return key;
request_failed:
key_revoke(authkey);
key_put(authkey);
alloc_authkey_failed:
/* it wasn't instantiated
* - remove from construction queue
* - mark the key as dead
*/
negated = 0;
down_write(&key_construction_sem);
list_del(&cons.link);
/* check it didn't get instantiated between the check and the down */
if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
set_bit(KEY_FLAG_NEGATIVE, &key->flags);
set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
negated = 1;
}
clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
up_write(&key_construction_sem);
if (!negated)
goto check_not_negative; /* surprisingly, the key got
* instantiated */
/* set the timeout and store in the session keyring if we can */
now = current_kernel_time();
key->expiry = now.tv_sec + key_negative_timeout;
if (current->signal->session_keyring) {
struct key *keyring;
rcu_read_lock();
keyring = rcu_dereference(current->signal->session_keyring);
atomic_inc(&keyring->usage);
rcu_read_unlock();
key_link(keyring, key);
key_put(keyring);
}
key_put(key);
/* notify anyone who was waiting */
wake_up_all(&request_key_conswq);
key = ERR_PTR(ret);
goto out;
alloc_failed:
up_write(&key_construction_sem);
goto out;
} /* end __request_key_construction() */
/*****************************************************************************/
/*
* call out to userspace to request the key
* - we check the construction queue first to see if an appropriate key is
* already being constructed by userspace
*/
static struct key *request_key_construction(struct key_type *type,
const char *description,
struct key_user *user,
const char *callout_info)
{
struct key_construction *pcons;
struct key *key, *ckey;
DECLARE_WAITQUEUE(myself, current);
kenter("%s,%s,{%d},%s",
type->name, description, user->uid, callout_info);
/* see if there's such a key under construction already */
down_write(&key_construction_sem);
list_for_each_entry(pcons, &user->consq, link) {
ckey = pcons->key;
if (ckey->type != type)
continue;
if (type->match(ckey, description))
goto found_key_under_construction;
}
/* see about getting userspace to construct the key */
key = __request_key_construction(type, description, callout_info);
error:
kleave(" = %p", key);
return key;
/* someone else has the same key under construction
* - we want to keep an eye on their key
*/
found_key_under_construction:
atomic_inc(&ckey->usage);
up_write(&key_construction_sem);
/* wait for the key to be completed one way or another */
add_wait_queue(&request_key_conswq, &myself);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
if (!test_bit(KEY_FLAG_USER_CONSTRUCT, &ckey->flags))
break;
if (signal_pending(current))
break;
schedule();
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&request_key_conswq, &myself);
/* we'll need to search this process's keyrings to see if the key is
* now there since we can't automatically assume it's also available
* there */
key_put(ckey);
ckey = NULL;
key = NULL; /* request a retry */
goto error;
} /* end request_key_construction() */
/*****************************************************************************/
/*
* link a freshly minted key to an appropriate destination keyring
*/
static void request_key_link(struct key *key, struct key *dest_keyring)
{
struct task_struct *tsk = current;
struct key *drop = NULL;
kenter("{%d},%p", key->serial, dest_keyring);
/* find the appropriate keyring */
if (!dest_keyring) {
switch (tsk->jit_keyring) {
case KEY_REQKEY_DEFL_DEFAULT:
case KEY_REQKEY_DEFL_THREAD_KEYRING:
dest_keyring = tsk->thread_keyring;
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_PROCESS_KEYRING:
dest_keyring = tsk->signal->process_keyring;
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_SESSION_KEYRING:
rcu_read_lock();
dest_keyring = key_get(
rcu_dereference(tsk->signal->session_keyring));
rcu_read_unlock();
drop = dest_keyring;
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
dest_keyring = current->user->session_keyring;
break;
case KEY_REQKEY_DEFL_USER_KEYRING:
dest_keyring = current->user->uid_keyring;
break;
case KEY_REQKEY_DEFL_GROUP_KEYRING:
default:
BUG();
}
}
/* and attach the key to it */
key_link(dest_keyring, key);
key_put(drop);
kleave("");
} /* end request_key_link() */
/*****************************************************************************/
/*
* request a key
* - search the process's keyrings
* - check the list of keys being created or updated
* - call out to userspace for a key if supplementary info was provided
* - cache the key in an appropriate keyring
*/
struct key *request_key_and_link(struct key_type *type,
const char *description,
const char *callout_info,
struct key *dest_keyring)
{
struct key_user *user;
struct key *key;
key_ref_t key_ref;
kenter("%s,%s,%s,%p",
type->name, description, callout_info, dest_keyring);
/* search all the process keyrings for a key */
key_ref = search_process_keyrings(type, description, type->match,
current);
kdebug("search 1: %p", key_ref);
if (!IS_ERR(key_ref)) {
key = key_ref_to_ptr(key_ref);
}
else if (PTR_ERR(key_ref) != -EAGAIN) {
key = ERR_PTR(PTR_ERR(key_ref));
}
else {
/* the search failed, but the keyrings were searchable, so we
* should consult userspace if we can */
key = ERR_PTR(-ENOKEY);
if (!callout_info)
goto error;
/* - get hold of the user's construction queue */
user = key_user_lookup(current->fsuid);
if (!user)
goto nomem;
for (;;) {
if (signal_pending(current))
goto interrupted;
/* ask userspace (returns NULL if it waited on a key
* being constructed) */
key = request_key_construction(type, description,
user, callout_info);
if (key)
break;
/* someone else made the key we want, so we need to
* search again as it might now be available to us */
key_ref = search_process_keyrings(type, description,
type->match,
current);
kdebug("search 2: %p", key_ref);
if (!IS_ERR(key_ref)) {
key = key_ref_to_ptr(key_ref);
break;
}
if (PTR_ERR(key_ref) != -EAGAIN) {
key = ERR_PTR(PTR_ERR(key_ref));
break;
}
}
key_user_put(user);
/* link the new key into the appropriate keyring */
if (!IS_ERR(key))
request_key_link(key, dest_keyring);
}
error:
kleave(" = %p", key);
return key;
nomem:
key = ERR_PTR(-ENOMEM);
goto error;
interrupted:
key_user_put(user);
key = ERR_PTR(-EINTR);
goto error;
} /* end request_key_and_link() */
/*****************************************************************************/
/*
* request a key
* - search the process's keyrings
* - check the list of keys being created or updated
* - call out to userspace for a key if supplementary info was provided
*/
struct key *request_key(struct key_type *type,
const char *description,
const char *callout_info)
{
return request_key_and_link(type, description, callout_info, NULL);
} /* end request_key() */
EXPORT_SYMBOL(request_key);
