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linux/security/keys/request_key.c

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/* Request a key from userspace
*
* Copyright (C) 2004-2007 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/security/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 <linux/slab.h>
#include "internal.h"
#define key_negative_timeout 60 /* default timeout on a negative key's existence */
/**
* complete_request_key - Complete the construction of a key.
* @cons: The key construction record.
* @error: The success or failute of the construction.
*
* Complete the attempt to construct a key. The key will be negated
* if an error is indicated. The authorisation key will be revoked
* unconditionally.
*/
void complete_request_key(struct key_construction *cons, int error)
{
kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
if (error < 0)
key_negate_and_link(cons->key, key_negative_timeout, NULL,
cons->authkey);
else
key_revoke(cons->authkey);
key_put(cons->key);
key_put(cons->authkey);
kfree(cons);
}
EXPORT_SYMBOL(complete_request_key);
/*
* Initialise a usermode helper that is going to have a specific session
* keyring.
*
* This is called in context of freshly forked kthread before kernel_execve(),
* so we can simply install the desired session_keyring at this point.
*/
static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
{
struct key *keyring = info->data;
return install_session_keyring_to_cred(cred, keyring);
}
/*
* Clean up a usermode helper with session keyring.
*/
static void umh_keys_cleanup(struct subprocess_info *info)
{
struct key *keyring = info->data;
key_put(keyring);
}
/*
* Call a usermode helper with a specific session keyring.
*/
static int call_usermodehelper_keys(char *path, char **argv, char **envp,
struct key *session_keyring, int wait)
{
struct subprocess_info *info;
info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
umh_keys_init, umh_keys_cleanup,
session_keyring);
if (!info)
return -ENOMEM;
key_get(session_keyring);
return call_usermodehelper_exec(info, wait);
}
/*
* 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_construction *cons,
const char *op,
void *aux)
{
const struct cred *cred = current_cred();
key_serial_t prkey, sskey;
struct key *key = cons->key, *authkey = cons->authkey, *keyring,
*session;
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);
ret = install_user_keyrings();
if (ret < 0)
goto error_alloc;
/* allocate a new session keyring */
sprintf(desc, "_req.%u", key->serial);
cred = get_current_cred();
keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
KEY_ALLOC_QUOTA_OVERRUN, NULL);
put_cred(cred);
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", from_kuid(&init_user_ns, cred->fsuid));
sprintf(gid_str, "%d", from_kgid(&init_user_ns, cred->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",
cred->thread_keyring ? cred->thread_keyring->serial : 0);
prkey = 0;
if (cred->process_keyring)
prkey = cred->process_keyring->serial;
sprintf(keyring_str[1], "%d", prkey);
rcu_read_lock();
session = rcu_dereference(cred->session_keyring);
if (!session)
session = cred->user->session_keyring;
sskey = session->serial;
rcu_read_unlock();
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,
UMH_WAIT_PROC);
kdebug("usermode -> 0x%x", ret);
if (ret >= 0) {
/* ret is the exit/wait code */
if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
key_validate(key) < 0)
ret = -ENOKEY;
else
/* ignore any errors from userspace if the key was
* instantiated */
ret = 0;
}
error_link:
key_put(keyring);
error_alloc:
complete_request_key(cons, ret);
kleave(" = %d", ret);
return ret;
}
/*
* Call out to userspace for key construction.
*
* Program failure is ignored in favour of key status.
*/
static int construct_key(struct key *key, const void *callout_info,
size_t callout_len, void *aux,
struct key *dest_keyring)
{
struct key_construction *cons;
request_key_actor_t actor;
struct key *authkey;
int ret;
kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
cons = kmalloc(sizeof(*cons), GFP_KERNEL);
if (!cons)
return -ENOMEM;
/* allocate an authorisation key */
authkey = request_key_auth_new(key, callout_info, callout_len,
dest_keyring);
if (IS_ERR(authkey)) {
kfree(cons);
ret = PTR_ERR(authkey);
authkey = NULL;
} else {
cons->authkey = key_get(authkey);
cons->key = key_get(key);
/* make the call */
actor = call_sbin_request_key;
if (key->type->request_key)
actor = key->type->request_key;
ret = actor(cons, "create", aux);
/* check that the actor called complete_request_key() prior to
* returning an error */
WARN_ON(ret < 0 &&
!test_bit(KEY_FLAG_REVOKED, &authkey->flags));
key_put(authkey);
}
kleave(" = %d", ret);
return ret;
}
/*
* Get the appropriate destination keyring for the request.
*
* The keyring selected is returned with an extra reference upon it which the
* caller must release.
*/
static void construct_get_dest_keyring(struct key **_dest_keyring)
{
struct request_key_auth *rka;
const struct cred *cred = current_cred();
struct key *dest_keyring = *_dest_keyring, *authkey;
kenter("%p", dest_keyring);
/* find the appropriate keyring */
if (dest_keyring) {
/* the caller supplied one */
key_get(dest_keyring);
} else {
/* use a default keyring; falling through the cases until we
* find one that we actually have */
switch (cred->jit_keyring) {
case KEY_REQKEY_DEFL_DEFAULT:
case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
if (cred->request_key_auth) {
authkey = cred->request_key_auth;
down_read(&authkey->sem);
rka = authkey->payload.data[0];
if (!test_bit(KEY_FLAG_REVOKED,
&authkey->flags))
dest_keyring =
key_get(rka->dest_keyring);
up_read(&authkey->sem);
if (dest_keyring)
break;
}
case KEY_REQKEY_DEFL_THREAD_KEYRING:
dest_keyring = key_get(cred->thread_keyring);
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_PROCESS_KEYRING:
dest_keyring = key_get(cred->process_keyring);
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_SESSION_KEYRING:
rcu_read_lock();
dest_keyring = key_get(
rcu_dereference(cred->session_keyring));
rcu_read_unlock();
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
dest_keyring =
key_get(cred->user->session_keyring);
break;
case KEY_REQKEY_DEFL_USER_KEYRING:
dest_keyring = key_get(cred->user->uid_keyring);
break;
case KEY_REQKEY_DEFL_GROUP_KEYRING:
default:
BUG();
}
}
*_dest_keyring = dest_keyring;
kleave(" [dk %d]", key_serial(dest_keyring));
return;
}
/*
* Allocate a new key in under-construction state and attempt to link it in to
* the requested keyring.
*
* May return a key that's already under construction instead if there was a
* race between two thread calling request_key().
*/
static int construct_alloc_key(struct keyring_search_context *ctx,
struct key *dest_keyring,
unsigned long flags,
struct key_user *user,
struct key **_key)
{
struct assoc_array_edit *edit;
struct key *key;
key_perm_t perm;
key_ref_t key_ref;
int ret;
kenter("%s,%s,,,",
ctx->index_key.type->name, ctx->index_key.description);
*_key = NULL;
mutex_lock(&user->cons_lock);
perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
perm |= KEY_USR_VIEW;
if (ctx->index_key.type->read)
perm |= KEY_POS_READ;
if (ctx->index_key.type == &key_type_keyring ||
ctx->index_key.type->update)
perm |= KEY_POS_WRITE;
key = key_alloc(ctx->index_key.type, ctx->index_key.description,
ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
perm, flags);
if (IS_ERR(key))
goto alloc_failed;
set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
if (dest_keyring) {
ret = __key_link_begin(dest_keyring, &ctx->index_key, &edit);
if (ret < 0)
goto link_prealloc_failed;
}
/* attach the key to the destination keyring under lock, but we do need
* to do another check just in case someone beat us to it whilst we
* waited for locks */
mutex_lock(&key_construction_mutex);
key_ref = search_process_keyrings(ctx);
if (!IS_ERR(key_ref))
goto key_already_present;
if (dest_keyring)
__key_link(key, &edit);
mutex_unlock(&key_construction_mutex);
if (dest_keyring)
__key_link_end(dest_keyring, &ctx->index_key, edit);
mutex_unlock(&user->cons_lock);
*_key = key;
kleave(" = 0 [%d]", key_serial(key));
return 0;
/* the key is now present - we tell the caller that we found it by
* returning -EINPROGRESS */
key_already_present:
key_put(key);
mutex_unlock(&key_construction_mutex);
key = key_ref_to_ptr(key_ref);
if (dest_keyring) {
ret = __key_link_check_live_key(dest_keyring, key);
if (ret == 0)
__key_link(key, &edit);
__key_link_end(dest_keyring, &ctx->index_key, edit);
if (ret < 0)
goto link_check_failed;
}
mutex_unlock(&user->cons_lock);
*_key = key;
kleave(" = -EINPROGRESS [%d]", key_serial(key));
return -EINPROGRESS;
link_check_failed:
mutex_unlock(&user->cons_lock);
key_put(key);
kleave(" = %d [linkcheck]", ret);
return ret;
link_prealloc_failed:
mutex_unlock(&user->cons_lock);
key_put(key);
kleave(" = %d [prelink]", ret);
return ret;
alloc_failed:
mutex_unlock(&user->cons_lock);
kleave(" = %ld", PTR_ERR(key));
return PTR_ERR(key);
}
/*
* Commence key construction.
*/
static struct key *construct_key_and_link(struct keyring_search_context *ctx,
const char *callout_info,
size_t callout_len,
void *aux,
struct key *dest_keyring,
unsigned long flags)
{
struct key_user *user;
struct key *key;
int ret;
kenter("");
if (ctx->index_key.type == &key_type_keyring)
return ERR_PTR(-EPERM);
user = key_user_lookup(current_fsuid());
if (!user)
return ERR_PTR(-ENOMEM);
construct_get_dest_keyring(&dest_keyring);
ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
key_user_put(user);
if (ret == 0) {
ret = construct_key(key, callout_info, callout_len, aux,
dest_keyring);
if (ret < 0) {
kdebug("cons failed");
goto construction_failed;
}
} else if (ret == -EINPROGRESS) {
ret = 0;
} else {
goto couldnt_alloc_key;
}
key_put(dest_keyring);
kleave(" = key %d", key_serial(key));
return key;
construction_failed:
key_negate_and_link(key, key_negative_timeout, NULL, NULL);
key_put(key);
couldnt_alloc_key:
key_put(dest_keyring);
kleave(" = %d", ret);
return ERR_PTR(ret);
}
/**
* request_key_and_link - Request a key and cache it in a keyring.
* @type: The type of key we want.
* @description: The searchable description of the key.
* @callout_info: The data to pass to the instantiation upcall (or NULL).
* @callout_len: The length of callout_info.
* @aux: Auxiliary data for the upcall.
* @dest_keyring: Where to cache the key.
* @flags: Flags to key_alloc().
*
* A key matching the specified criteria is searched for in the process's
* keyrings and returned with its usage count incremented if found. Otherwise,
* if callout_info is not NULL, a key will be allocated and some service
* (probably in userspace) will be asked to instantiate it.
*
* If successfully found or created, the key will be linked to the destination
* keyring if one is provided.
*
* Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
* or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
* found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
* if insufficient key quota was available to create a new key; or -ENOMEM if
* insufficient memory was available.
*
* If the returned key was created, then it may still be under construction,
* and wait_for_key_construction() should be used to wait for that to complete.
*/
struct key *request_key_and_link(struct key_type *type,
const char *description,
const void *callout_info,
size_t callout_len,
void *aux,
struct key *dest_keyring,
unsigned long flags)
{
struct keyring_search_context ctx = {
.index_key.type = type,
.index_key.description = description,
.cred = current_cred(),
.match_data.cmp = key_default_cmp,
.match_data.raw_data = description,
.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
.flags = (KEYRING_SEARCH_DO_STATE_CHECK |
KEYRING_SEARCH_SKIP_EXPIRED),
};
struct key *key;
key_ref_t key_ref;
int ret;
kenter("%s,%s,%p,%zu,%p,%p,%lx",
ctx.index_key.type->name, ctx.index_key.description,
callout_info, callout_len, aux, dest_keyring, flags);
if (type->match_preparse) {
ret = type->match_preparse(&ctx.match_data);
if (ret < 0) {
key = ERR_PTR(ret);
goto error;
}
}
/* search all the process keyrings for a key */
key_ref = search_process_keyrings(&ctx);
if (!IS_ERR(key_ref)) {
key = key_ref_to_ptr(key_ref);
if (dest_keyring) {
construct_get_dest_keyring(&dest_keyring);
ret = key_link(dest_keyring, key);
key_put(dest_keyring);
if (ret < 0) {
key_put(key);
key = ERR_PTR(ret);
goto error_free;
}
}
} else if (PTR_ERR(key_ref) != -EAGAIN) {
key = ERR_CAST(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_free;
key = construct_key_and_link(&ctx, callout_info, callout_len,
aux, dest_keyring, flags);
}
error_free:
if (type->match_free)
type->match_free(&ctx.match_data);
error:
kleave(" = %p", key);
return key;
}
/**
* wait_for_key_construction - Wait for construction of a key to complete
* @key: The key being waited for.
* @intr: Whether to wait interruptibly.
*
* Wait for a key to finish being constructed.
*
* Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
* if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
* revoked or expired.
*/
int wait_for_key_construction(struct key *key, bool intr)
{
int ret;
ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
if (ret)
return -ERESTARTSYS;
if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
smp_rmb();
return key->reject_error;
}
return key_validate(key);
}
EXPORT_SYMBOL(wait_for_key_construction);
/**
* request_key - Request a key and wait for construction
* @type: Type of key.
* @description: The searchable description of the key.
* @callout_info: The data to pass to the instantiation upcall (or NULL).
*
* As for request_key_and_link() except that it does not add the returned key
* to a keyring if found, new keys are always allocated in the user's quota,
* the callout_info must be a NUL-terminated string and no auxiliary data can
* be passed.
*
* Furthermore, it then works as wait_for_key_construction() to wait for the
* completion of keys undergoing construction with a non-interruptible wait.
*/
struct key *request_key(struct key_type *type,
const char *description,
const char *callout_info)
{
struct key *key;
size_t callout_len = 0;
int ret;
if (callout_info)
callout_len = strlen(callout_info);
key = request_key_and_link(type, description, callout_info, callout_len,
NULL, NULL, KEY_ALLOC_IN_QUOTA);
if (!IS_ERR(key)) {
ret = wait_for_key_construction(key, false);
if (ret < 0) {
key_put(key);
return ERR_PTR(ret);
}
}
return key;
}
EXPORT_SYMBOL(request_key);
/**
* request_key_with_auxdata - Request a key with auxiliary data for the upcaller
* @type: The type of key we want.
* @description: The searchable description of the key.
* @callout_info: The data to pass to the instantiation upcall (or NULL).
* @callout_len: The length of callout_info.
* @aux: Auxiliary data for the upcall.
*
* As for request_key_and_link() except that it does not add the returned key
* to a keyring if found and new keys are always allocated in the user's quota.
*
* Furthermore, it then works as wait_for_key_construction() to wait for the
* completion of keys undergoing construction with a non-interruptible wait.
*/
struct key *request_key_with_auxdata(struct key_type *type,
const char *description,
const void *callout_info,
size_t callout_len,
void *aux)
{
struct key *key;
int ret;
key = request_key_and_link(type, description, callout_info, callout_len,
aux, NULL, KEY_ALLOC_IN_QUOTA);
if (!IS_ERR(key)) {
ret = wait_for_key_construction(key, false);
if (ret < 0) {
key_put(key);
return ERR_PTR(ret);
}
}
return key;
}
EXPORT_SYMBOL(request_key_with_auxdata);
/*
* request_key_async - Request a key (allow async construction)
* @type: Type of key.
* @description: The searchable description of the key.
* @callout_info: The data to pass to the instantiation upcall (or NULL).
* @callout_len: The length of callout_info.
*
* As for request_key_and_link() except that it does not add the returned key
* to a keyring if found, new keys are always allocated in the user's quota and
* no auxiliary data can be passed.
*
* The caller should call wait_for_key_construction() to wait for the
* completion of the returned key if it is still undergoing construction.
*/
struct key *request_key_async(struct key_type *type,
const char *description,
const void *callout_info,
size_t callout_len)
{
return request_key_and_link(type, description, callout_info,
callout_len, NULL, NULL,
KEY_ALLOC_IN_QUOTA);
}
EXPORT_SYMBOL(request_key_async);
/*
* request a key with auxiliary data for the upcaller (allow async construction)
* @type: Type of key.
* @description: The searchable description of the key.
* @callout_info: The data to pass to the instantiation upcall (or NULL).
* @callout_len: The length of callout_info.
* @aux: Auxiliary data for the upcall.
*
* As for request_key_and_link() except that it does not add the returned key
* to a keyring if found and new keys are always allocated in the user's quota.
*
* The caller should call wait_for_key_construction() to wait for the
* completion of the returned key if it is still undergoing construction.
*/
struct key *request_key_async_with_auxdata(struct key_type *type,
const char *description,
const void *callout_info,
size_t callout_len,
void *aux)
{
return request_key_and_link(type, description, callout_info,
callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
}
EXPORT_SYMBOL(request_key_async_with_auxdata);
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