linux/security/keys/process_keys.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

745 lines
17 KiB
C

/* process_keys.c: management of a process's keyrings
*
* 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.
*/
#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 <asm/uaccess.h>
#include "internal.h"
/* session keyring create vs join semaphore */
static DECLARE_MUTEX(key_session_sem);
/* the root user's tracking struct */
struct key_user root_key_user = {
.usage = ATOMIC_INIT(3),
.consq = LIST_HEAD_INIT(root_key_user.consq),
.lock = SPIN_LOCK_UNLOCKED,
.nkeys = ATOMIC_INIT(2),
.nikeys = ATOMIC_INIT(2),
.uid = 0,
};
/* the root user's UID keyring */
struct key root_user_keyring = {
.usage = ATOMIC_INIT(1),
.serial = 2,
.type = &key_type_keyring,
.user = &root_key_user,
.sem = __RWSEM_INITIALIZER(root_user_keyring.sem),
.perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
.flags = 1 << KEY_FLAG_INSTANTIATED,
.description = "_uid.0",
#ifdef KEY_DEBUGGING
.magic = KEY_DEBUG_MAGIC,
#endif
};
/* the root user's default session keyring */
struct key root_session_keyring = {
.usage = ATOMIC_INIT(1),
.serial = 1,
.type = &key_type_keyring,
.user = &root_key_user,
.sem = __RWSEM_INITIALIZER(root_session_keyring.sem),
.perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
.flags = 1 << KEY_FLAG_INSTANTIATED,
.description = "_uid_ses.0",
#ifdef KEY_DEBUGGING
.magic = KEY_DEBUG_MAGIC,
#endif
};
/*****************************************************************************/
/*
* allocate the keyrings to be associated with a UID
*/
int alloc_uid_keyring(struct user_struct *user)
{
struct key *uid_keyring, *session_keyring;
char buf[20];
int ret;
/* concoct a default session keyring */
sprintf(buf, "_uid_ses.%u", user->uid);
session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0, NULL);
if (IS_ERR(session_keyring)) {
ret = PTR_ERR(session_keyring);
goto error;
}
/* and a UID specific keyring, pointed to by the default session
* keyring */
sprintf(buf, "_uid.%u", user->uid);
uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0,
session_keyring);
if (IS_ERR(uid_keyring)) {
key_put(session_keyring);
ret = PTR_ERR(uid_keyring);
goto error;
}
/* install the keyrings */
user->uid_keyring = uid_keyring;
user->session_keyring = session_keyring;
ret = 0;
error:
return ret;
} /* end alloc_uid_keyring() */
/*****************************************************************************/
/*
* deal with the UID changing
*/
void switch_uid_keyring(struct user_struct *new_user)
{
#if 0 /* do nothing for now */
struct key *old;
/* switch to the new user's session keyring if we were running under
* root's default session keyring */
if (new_user->uid != 0 &&
current->session_keyring == &root_session_keyring
) {
atomic_inc(&new_user->session_keyring->usage);
task_lock(current);
old = current->session_keyring;
current->session_keyring = new_user->session_keyring;
task_unlock(current);
key_put(old);
}
#endif
} /* end switch_uid_keyring() */
/*****************************************************************************/
/*
* install a fresh thread keyring, discarding the old one
*/
int install_thread_keyring(struct task_struct *tsk)
{
struct key *keyring, *old;
char buf[20];
int ret;
sprintf(buf, "_tid.%u", tsk->pid);
keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
goto error;
}
task_lock(tsk);
old = tsk->thread_keyring;
tsk->thread_keyring = keyring;
task_unlock(tsk);
ret = 0;
key_put(old);
error:
return ret;
} /* end install_thread_keyring() */
/*****************************************************************************/
/*
* make sure a process keyring is installed
*/
int install_process_keyring(struct task_struct *tsk)
{
unsigned long flags;
struct key *keyring;
char buf[20];
int ret;
if (!tsk->signal->process_keyring) {
sprintf(buf, "_pid.%u", tsk->tgid);
keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
goto error;
}
/* attach keyring */
spin_lock_irqsave(&tsk->sighand->siglock, flags);
if (!tsk->signal->process_keyring) {
tsk->signal->process_keyring = keyring;
keyring = NULL;
}
spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
key_put(keyring);
}
ret = 0;
error:
return ret;
} /* end install_process_keyring() */
/*****************************************************************************/
/*
* 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 task_struct *tsk,
struct key *keyring)
{
unsigned long flags;
struct key *old;
char buf[20];
int ret;
/* create an empty session keyring */
if (!keyring) {
sprintf(buf, "_ses.%u", tsk->tgid);
keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
goto error;
}
}
else {
atomic_inc(&keyring->usage);
}
/* install the keyring */
spin_lock_irqsave(&tsk->sighand->siglock, flags);
old = rcu_dereference(tsk->signal->session_keyring);
rcu_assign_pointer(tsk->signal->session_keyring, keyring);
spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
ret = 0;
/* we're using RCU on the pointer */
synchronize_rcu();
key_put(old);
error:
return ret;
} /* end install_session_keyring() */
/*****************************************************************************/
/*
* copy the keys in a thread group for fork without CLONE_THREAD
*/
int copy_thread_group_keys(struct task_struct *tsk)
{
key_check(current->thread_group->session_keyring);
key_check(current->thread_group->process_keyring);
/* no process keyring yet */
tsk->signal->process_keyring = NULL;
/* same session keyring */
rcu_read_lock();
tsk->signal->session_keyring =
key_get(rcu_dereference(current->signal->session_keyring));
rcu_read_unlock();
return 0;
} /* end copy_thread_group_keys() */
/*****************************************************************************/
/*
* copy the keys for fork
*/
int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
{
key_check(tsk->thread_keyring);
key_check(tsk->request_key_auth);
/* no thread keyring yet */
tsk->thread_keyring = NULL;
/* copy the request_key() authorisation for this thread */
key_get(tsk->request_key_auth);
return 0;
} /* end copy_keys() */
/*****************************************************************************/
/*
* dispose of thread group keys upon thread group destruction
*/
void exit_thread_group_keys(struct signal_struct *tg)
{
key_put(tg->session_keyring);
key_put(tg->process_keyring);
} /* end exit_thread_group_keys() */
/*****************************************************************************/
/*
* dispose of per-thread keys upon thread exit
*/
void exit_keys(struct task_struct *tsk)
{
key_put(tsk->thread_keyring);
key_put(tsk->request_key_auth);
} /* end exit_keys() */
/*****************************************************************************/
/*
* deal with execve()
*/
int exec_keys(struct task_struct *tsk)
{
unsigned long flags;
struct key *old;
/* newly exec'd tasks don't get a thread keyring */
task_lock(tsk);
old = tsk->thread_keyring;
tsk->thread_keyring = NULL;
task_unlock(tsk);
key_put(old);
/* discard the process keyring from a newly exec'd task */
spin_lock_irqsave(&tsk->sighand->siglock, flags);
old = tsk->signal->process_keyring;
tsk->signal->process_keyring = NULL;
spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
key_put(old);
return 0;
} /* end exec_keys() */
/*****************************************************************************/
/*
* deal with SUID programs
* - we might want to make this invent a new session keyring
*/
int suid_keys(struct task_struct *tsk)
{
return 0;
} /* end suid_keys() */
/*****************************************************************************/
/*
* the filesystem user ID changed
*/
void key_fsuid_changed(struct task_struct *tsk)
{
/* update the ownership of the thread keyring */
if (tsk->thread_keyring) {
down_write(&tsk->thread_keyring->sem);
tsk->thread_keyring->uid = tsk->fsuid;
up_write(&tsk->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 */
if (tsk->thread_keyring) {
down_write(&tsk->thread_keyring->sem);
tsk->thread_keyring->gid = tsk->fsgid;
up_write(&tsk->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,
struct task_struct *context)
{
struct request_key_auth *rka;
key_ref_t key_ref, ret, err;
/* 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 (context->thread_keyring) {
key_ref = keyring_search_aux(
make_key_ref(context->thread_keyring, 1),
context, 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 (context->signal->process_keyring) {
key_ref = keyring_search_aux(
make_key_ref(context->signal->process_keyring, 1),
context, 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 (context->signal->session_keyring) {
rcu_read_lock();
key_ref = keyring_search_aux(
make_key_ref(rcu_dereference(
context->signal->session_keyring),
1),
context, 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 {
key_ref = keyring_search_aux(
make_key_ref(context->user->session_keyring, 1),
context, 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 (context->request_key_auth &&
context == current &&
type != &key_type_request_key_auth &&
key_validate(context->request_key_auth) == 0
) {
rka = context->request_key_auth->payload.data;
key_ref = search_process_keyrings(type, description, match,
rka->context);
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;
}
}
/* 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(struct task_struct *context, key_serial_t id,
int create, int partial, key_perm_t perm)
{
key_ref_t key_ref, skey_ref;
struct key *key;
int ret;
if (!context)
context = current;
key_ref = ERR_PTR(-ENOKEY);
switch (id) {
case KEY_SPEC_THREAD_KEYRING:
if (!context->thread_keyring) {
if (!create)
goto error;
ret = install_thread_keyring(context);
if (ret < 0) {
key = ERR_PTR(ret);
goto error;
}
}
key = context->thread_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_PROCESS_KEYRING:
if (!context->signal->process_keyring) {
if (!create)
goto error;
ret = install_process_keyring(context);
if (ret < 0) {
key = ERR_PTR(ret);
goto error;
}
}
key = context->signal->process_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_SESSION_KEYRING:
if (!context->signal->session_keyring) {
/* always install a session keyring upon access if one
* doesn't exist yet */
ret = install_session_keyring(
context, context->user->session_keyring);
if (ret < 0)
goto error;
}
rcu_read_lock();
key = rcu_dereference(context->signal->session_keyring);
atomic_inc(&key->usage);
rcu_read_unlock();
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_USER_KEYRING:
key = context->user->uid_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_USER_SESSION_KEYRING:
key = context->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 = context->request_key_auth;
if (!key)
goto error;
atomic_inc(&key->usage);
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_PTR(PTR_ERR(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,
current);
if (!IS_ERR(skey_ref)) {
key_put(key);
key_ref = skey_ref;
}
break;
}
/* check the status */
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, context, perm);
if (ret < 0)
goto invalid_key;
error:
return key_ref;
invalid_key:
key_ref_put(key_ref);
key_ref = ERR_PTR(ret);
goto error;
} /* 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)
{
struct task_struct *tsk = current;
struct key *keyring;
long ret;
/* if no name is provided, install an anonymous keyring */
if (!name) {
ret = install_session_keyring(tsk, NULL);
if (ret < 0)
goto error;
rcu_read_lock();
ret = rcu_dereference(tsk->signal->session_keyring)->serial;
rcu_read_unlock();
goto error;
}
/* allow the user to join or create a named keyring */
down(&key_session_sem);
/* look for an existing keyring of this name */
keyring = find_keyring_by_name(name, 0);
if (PTR_ERR(keyring) == -ENOKEY) {
/* not found - try and create a new one */
keyring = keyring_alloc(name, tsk->uid, tsk->gid, 0, 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(tsk, keyring);
if (ret < 0)
goto error2;
ret = keyring->serial;
key_put(keyring);
error2:
up(&key_session_sem);
error:
return ret;
} /* end join_session_keyring() */