android_kernel_xiaomi_sm8350/security/keys/request_key.c
David Howells b5f545c880 [PATCH] keys: Permit running process to instantiate keys
Make it possible for a running process (such as gssapid) to be able to
instantiate a key, as was requested by Trond Myklebust for NFS4.

The patch makes the following changes:

 (1) A new, optional key type method has been added. This permits a key type
     to intercept requests at the point /sbin/request-key is about to be
     spawned and do something else with them - passing them over the
     rpc_pipefs files or netlink sockets for instance.

     The uninstantiated key, the authorisation key and the intended operation
     name are passed to the method.

 (2) The callout_info is no longer passed as an argument to /sbin/request-key
     to prevent unauthorised viewing of this data using ps or by looking in
     /proc/pid/cmdline.

     This means that the old /sbin/request-key program will not work with the
     patched kernel as it will expect to see an extra argument that is no
     longer there.

     A revised keyutils package will be made available tomorrow.

 (3) The callout_info is now attached to the authorisation key. Reading this
     key will retrieve the information.

 (4) A new field has been added to the task_struct. This holds the
     authorisation key currently active for a thread. Searches now look here
     for the caller's set of keys rather than looking for an auth key in the
     lowest level of the session keyring.

     This permits a thread to be servicing multiple requests at once and to
     switch between them. Note that this is per-thread, not per-process, and
     so is usable in multithreaded programs.

     The setting of this field is inherited across fork and exec.

 (5) A new keyctl function (KEYCTL_ASSUME_AUTHORITY) has been added that
     permits a thread to assume the authority to deal with an uninstantiated
     key. Assumption is only permitted if the authorisation key associated
     with the uninstantiated key is somewhere in the thread's keyrings.

     This function can also clear the assumption.

 (6) A new magic key specifier has been added to refer to the currently
     assumed authorisation key (KEY_SPEC_REQKEY_AUTH_KEY).

 (7) Instantiation will only proceed if the appropriate authorisation key is
     assumed first. The assumed authorisation key is discarded if
     instantiation is successful.

 (8) key_validate() is moved from the file of request_key functions to the
     file of permissions functions.

 (9) The documentation is updated.

From: <Valdis.Kletnieks@vt.edu>

    Build fix.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Alexander Zangerl <az@bond.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-08 20:13:53 -08:00

491 lines
12 KiB
C

/* 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);