// SPDX-License-Identifier: GPL-2.0-or-later
/* Request a key from userspace
*
* Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*
* See Documentation/security/keys/request-key.rst
*/
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/err.h>
#include <linux/keyctl.h>
#include <linux/slab.h>
#include <net/net_namespace.h>
#include "internal.h"
#include <keys/request_key_auth-type.h>
#define key_negative_timeout 60 /* default timeout on a negative key's existence */
static struct key *check_cached_key(struct keyring_search_context *ctx)
{
#ifdef CONFIG_KEYS_REQUEST_CACHE
struct key *key = current->cached_requested_key;
if (key &&
ctx->match_data.cmp(key, &ctx->match_data) &&
!(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED))))
return key_get(key);
#endif
return NULL;
}
static void cache_requested_key(struct key *key)
{
#ifdef CONFIG_KEYS_REQUEST_CACHE
struct task_struct *t = current;
/* Do not cache key if it is a kernel thread */
if (!(t->flags & PF_KTHREAD)) {
key_put(t->cached_requested_key);
t->cached_requested_key = key_get(key);
set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
}
#endif
}
/**
* complete_request_key - Complete the construction of a key.
* @authkey: The authorisation key.
* @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 *authkey, int error)
{
struct request_key_auth *rka = get_request_key_auth(authkey);
struct key *key = rka->target_key;
kenter("%d{%d},%d", authkey->serial, key->serial, error);
if (error < 0)
key_negate_and_link(key, key_negative_timeout, NULL, authkey);
else
key_revoke(authkey);
}
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(const 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 *authkey, void *aux)
{
static char const request_key[] = "/sbin/request-key";
struct request_key_auth *rka = get_request_key_auth(authkey);
const struct cred *cred = current_cred();
key_serial_t prkey, sskey;
struct key *key = rka->target_key, *keyring, *session, *user_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, rka->op);
ret = look_up_user_keyrings(NULL, &user_session);
if (ret < 0)
goto error_us;
/* 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, 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);
session = cred->session_keyring;
if (!session)
session = user_session;
sskey = session->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++] = (char *)request_key;
argv[i++] = (char *)rka->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(request_key, 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:
key_put(user_session);
error_us:
complete_request_key(authkey, 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)
{
request_key_actor_t actor;
struct key *authkey;
int ret;
kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
/* allocate an authorisation key */
authkey = request_key_auth_new(key, "create", callout_info, callout_len,
dest_keyring);
if (IS_ERR(authkey))
return PTR_ERR(authkey);
/* Make the call */
actor = call_sbin_request_key;
if (key->type->request_key)
actor = key->type->request_key;
ret = actor(authkey, aux);
/* check that the actor called complete_request_key() prior to
* returning an error */
WARN_ON(ret < 0 &&
!test_bit(KEY_FLAG_INVALIDATED, &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 int 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;
int ret;
kenter("%p", dest_keyring);
/* find the appropriate keyring */
if (dest_keyring) {
/* the caller supplied one */
key_get(dest_keyring);
} else {
bool do_perm_check = true;
/* 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 = get_request_key_auth(authkey);
if (!test_bit(KEY_FLAG_REVOKED,
&authkey->flags))
dest_keyring =
key_get(rka->dest_keyring);
up_read(&authkey->sem);
if (dest_keyring) {
do_perm_check = false;
break;
}
}
fallthrough;
case KEY_REQKEY_DEFL_THREAD_KEYRING:
dest_keyring = key_get(cred->thread_keyring);
if (dest_keyring)
break;
fallthrough;
case KEY_REQKEY_DEFL_PROCESS_KEYRING:
dest_keyring = key_get(cred->process_keyring);
if (dest_keyring)
break;
fallthrough;
case KEY_REQKEY_DEFL_SESSION_KEYRING:
dest_keyring = key_get(cred->session_keyring);
if (dest_keyring)
break;
fallthrough;
case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
ret = look_up_user_keyrings(NULL, &dest_keyring);
if (ret < 0)
return ret;
break;
case KEY_REQKEY_DEFL_USER_KEYRING:
ret = look_up_user_keyrings(&dest_keyring, NULL);
if (ret < 0)
return ret;
break;
case KEY_REQKEY_DEFL_GROUP_KEYRING:
default:
BUG();
}
/*
* Require Write permission on the keyring. This is essential
* because the default keyring may be the session keyring, and
* joining a keyring only requires Search permission.
*
* However, this check is skipped for the "requestor keyring" so
* that /sbin/request-key can itself use request_key() to add
* keys to the original requestor's destination keyring.
*/
if (dest_keyring && do_perm_check) {
ret = key_permission(make_key_ref(dest_keyring, 1),
KEY_NEED_WRITE);
if (ret) {
key_put(dest_keyring);
return ret;
}
}
}
*_dest_keyring = dest_keyring;
kleave(" [dk %d]", key_serial(dest_keyring));
return 0;
}
/*
* 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 = NULL;
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, NULL);
if (IS_ERR(key))
goto alloc_failed;
set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
if (dest_keyring) {
ret = __key_link_lock(dest_keyring, &key->index_key);
if (ret < 0)
goto link_lock_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.
*
* The caller might specify a comparison function which looks for keys
* that do not exactly match but are still equivalent from the caller's
* perspective. The __key_link_begin() operation must be done only after
* an actual key is determined.
*/
mutex_lock(&key_construction_mutex);
rcu_read_lock();
key_ref = search_process_keyrings_rcu(ctx);
rcu_read_unlock();
if (!IS_ERR(key_ref))
goto key_already_present;
if (dest_keyring) {
ret = __key_link_begin(dest_keyring, &key->index_key, &edit);
if (ret < 0)
goto link_alloc_failed;
__key_link(dest_keyring, key, &edit);
}
mutex_unlock(&key_construction_mutex);
if (dest_keyring)
__key_link_end(dest_keyring, &key->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_begin(dest_keyring, &key->index_key, &edit);
if (ret < 0)
goto link_alloc_failed_unlocked;
ret = __key_link_check_live_key(dest_keyring, key);
if (ret == 0)
__key_link(dest_keyring, key, &edit);
__key_link_end(dest_keyring, &key->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_alloc_failed:
mutex_unlock(&key_construction_mutex);
link_alloc_failed_unlocked:
__key_link_end(dest_keyring, &key->index_key, edit);
link_lock_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);
ret = construct_get_dest_keyring(&dest_keyring);
if (ret)
goto error;
user = key_user_lookup(current_fsuid());
if (!user) {
ret = -ENOMEM;
goto error_put_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 error_put_dest_keyring;
}
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);
error_put_dest_keyring:
key_put(dest_keyring);
error:
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.
* @domain_tag: The domain in which the key operates.
* @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 (type, description, domain_tag) 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,
struct key_tag *domain_tag,
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.domain_tag = domain_tag,
.index_key.description = description,
.index_key.desc_len = strlen(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 |
KEYRING_SEARCH_RECURSE),
};
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;
}
}
key = check_cached_key(&ctx);
if (key)
goto error_free;
/* search all the process keyrings for a key */
rcu_read_lock();
key_ref = search_process_keyrings_rcu(&ctx);
rcu_read_unlock();
if (!IS_ERR(key_ref)) {
if (dest_keyring) {
ret = key_task_permission(key_ref, current_cred(),
KEY_NEED_LINK);
if (ret < 0) {
key_ref_put(key_ref);
key = ERR_PTR(ret);
goto error_free;
}
}
key = key_ref_to_ptr(key_ref);
if (dest_keyring) {
ret = key_link(dest_keyring, key);
if (ret < 0) {
key_put(key);
key = ERR_PTR(ret);
goto error_free;
}
}
/* Only cache the key on immediate success */
cache_requested_key(key);
} 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;
ret = key_read_state(key);
if (ret < 0)
return ret;
return key_validate(key);
}
EXPORT_SYMBOL(wait_for_key_construction);
/**
* request_key_tag - Request a key and wait for construction
* @type: Type of key.
* @description: The searchable description of the key.
* @domain_tag: The domain in which the key operates.
* @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_tag(struct key_type *type,
const char *description,
struct key_tag *domain_tag,
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, domain_tag,
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_tag);
/**
* 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.
* @domain_tag: The domain in which the key operates.
* @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,
struct key_tag *domain_tag,
const void *callout_info,
size_t callout_len,
void *aux)
{
struct key *key;
int ret;
key = request_key_and_link(type, description, domain_tag,
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_rcu - Request key from RCU-read-locked context
* @type: The type of key we want.
* @description: The name of the key we want.
* @domain_tag: The domain in which the key operates.
*
* Request a key from a context that we may not sleep in (such as RCU-mode
* pathwalk). Keys under construction are ignored.
*
* Return a pointer to the found key if successful, -ENOKEY if we couldn't find
* a key or some other error if the key found was unsuitable or inaccessible.
*/
struct key *request_key_rcu(struct key_type *type,
const char *description,
struct key_tag *domain_tag)
{
struct keyring_search_context ctx = {
.index_key.type = type,
.index_key.domain_tag = domain_tag,
.index_key.description = description,
.index_key.desc_len = strlen(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;
kenter("%s,%s", type->name, description);
key = check_cached_key(&ctx);
if (key)
return key;
/* search all the process keyrings for a key */
key_ref = search_process_keyrings_rcu(&ctx);
if (IS_ERR(key_ref)) {
key = ERR_CAST(key_ref);
if (PTR_ERR(key_ref) == -EAGAIN)
key = ERR_PTR(-ENOKEY);
} else {
key = key_ref_to_ptr(key_ref);
cache_requested_key(key);
}
kleave(" = %p", key);
return key;
}
EXPORT_SYMBOL(request_key_rcu);
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