// SPDX-License-Identifier: GPL-2.0-or-later
/* Request key authorisation token key definition.
*
* Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*
* See Documentation/security/keys/request-key.rst
*/
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include "internal.h"
#include <keys/request_key_auth-type.h>
static int request_key_auth_preparse(struct key_preparsed_payload *);
static void request_key_auth_free_preparse(struct key_preparsed_payload *);
static int request_key_auth_instantiate(struct key *,
struct key_preparsed_payload *);
static void request_key_auth_describe(const struct key *, struct seq_file *);
static void request_key_auth_revoke(struct key *);
static void request_key_auth_destroy(struct key *);
static long request_key_auth_read(const struct key *, char *, size_t);
/*
* The request-key authorisation key type definition.
*/
struct key_type key_type_request_key_auth = {
.name = ".request_key_auth",
.def_datalen = sizeof(struct request_key_auth),
.preparse = request_key_auth_preparse,
.free_preparse = request_key_auth_free_preparse,
.instantiate = request_key_auth_instantiate,
.describe = request_key_auth_describe,
.revoke = request_key_auth_revoke,
.destroy = request_key_auth_destroy,
.read = request_key_auth_read,
};
static int request_key_auth_preparse(struct key_preparsed_payload *prep)
{
return 0;
}
static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
{
}
/*
* Instantiate a request-key authorisation key.
*/
static int request_key_auth_instantiate(struct key *key,
struct key_preparsed_payload *prep)
{
rcu_assign_keypointer(key, (struct request_key_auth *)prep->data);
return 0;
}
/*
* Describe an authorisation token.
*/
static void request_key_auth_describe(const struct key *key,
struct seq_file *m)
{
struct request_key_auth *rka = dereference_key_rcu(key);
if (!rka)
return;
seq_puts(m, "key:");
seq_puts(m, key->description);
if (key_is_positive(key))
seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
}
/*
* Read the callout_info data (retrieves the callout information).
* - the key's semaphore is read-locked
*/
static long request_key_auth_read(const struct key *key,
char *buffer, size_t buflen)
{
struct request_key_auth *rka = dereference_key_locked(key);
size_t datalen;
long ret;
if (!rka)
return -EKEYREVOKED;
datalen = rka->callout_len;
ret = datalen;
/* we can return the data as is */
if (buffer && buflen > 0) {
if (buflen > datalen)
buflen = datalen;
memcpy(buffer, rka->callout_info, buflen);
}
return ret;
}
static void free_request_key_auth(struct request_key_auth *rka)
{
if (!rka)
return;
key_put(rka->target_key);
key_put(rka->dest_keyring);
if (rka->cred)
put_cred(rka->cred);
kfree(rka->callout_info);
kfree(rka);
}
/*
* Dispose of the request_key_auth record under RCU conditions
*/
static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
{
struct request_key_auth *rka =
container_of(rcu, struct request_key_auth, rcu);
free_request_key_auth(rka);
}
/*
* Handle revocation of an authorisation token key.
*
* Called with the key sem write-locked.
*/
static void request_key_auth_revoke(struct key *key)
{
struct request_key_auth *rka = dereference_key_locked(key);
kenter("{%d}", key->serial);
rcu_assign_keypointer(key, NULL);
call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
}
/*
* Destroy an instantiation authorisation token key.
*/
static void request_key_auth_destroy(struct key *key)
{
struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0);
kenter("{%d}", key->serial);
if (rka) {
rcu_assign_keypointer(key, NULL);
call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
}
}
/*
* Create an authorisation token for /sbin/request-key or whoever to gain
* access to the caller's security data.
*/
struct key *request_key_auth_new(struct key *target, const char *op,
const void *callout_info, size_t callout_len,
struct key *dest_keyring)
{
struct request_key_auth *rka, *irka;
const struct cred *cred = current_cred();
struct key *authkey = NULL;
char desc[20];
int ret = -ENOMEM;
kenter("%d,", target->serial);
/* allocate a auth record */
rka = kzalloc(sizeof(*rka), GFP_KERNEL);
if (!rka)
goto error;
rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
if (!rka->callout_info)
goto error_free_rka;
rka->callout_len = callout_len;
strscpy(rka->op, op, sizeof(rka->op));
/* see if the calling process is already servicing the key request of
* another process */
if (cred->request_key_auth) {
/* it is - use that instantiation context here too */
down_read(&cred->request_key_auth->sem);
/* if the auth key has been revoked, then the key we're
* servicing is already instantiated */
if (test_bit(KEY_FLAG_REVOKED,
&cred->request_key_auth->flags)) {
up_read(&cred->request_key_auth->sem);
ret = -EKEYREVOKED;
goto error_free_rka;
}
irka = cred->request_key_auth->payload.data[0];
rka->cred = get_cred(irka->cred);
rka->pid = irka->pid;
up_read(&cred->request_key_auth->sem);
}
else {
/* it isn't - use this process as the context */
rka->cred = get_cred(cred);
rka->pid = current->pid;
}
rka->target_key = key_get(target);
rka->dest_keyring = key_get(dest_keyring);
/* allocate the auth key */
sprintf(desc, "%x", target->serial);
authkey = key_alloc(&key_type_request_key_auth, desc,
cred->fsuid, cred->fsgid, cred,
KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK |
KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
if (IS_ERR(authkey)) {
ret = PTR_ERR(authkey);
goto error_free_rka;
}
/* construct the auth key */
ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
if (ret < 0)
goto error_put_authkey;
kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
return authkey;
error_put_authkey:
key_put(authkey);
error_free_rka:
free_request_key_auth(rka);
error:
kleave("= %d", ret);
return ERR_PTR(ret);
}
/*
* Search the current process's keyrings for the authorisation key for
* instantiation of a key.
*/
struct key *key_get_instantiation_authkey(key_serial_t target_id)
{
char description[16];
struct keyring_search_context ctx = {
.index_key.type = &key_type_request_key_auth,
.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_RECURSE),
};
struct key *authkey;
key_ref_t authkey_ref;
ctx.index_key.desc_len = sprintf(description, "%x", target_id);
rcu_read_lock();
authkey_ref = search_process_keyrings_rcu(&ctx);
rcu_read_unlock();
if (IS_ERR(authkey_ref)) {
authkey = ERR_CAST(authkey_ref);
if (authkey == ERR_PTR(-EAGAIN))
authkey = ERR_PTR(-ENOKEY);
goto error;
}
authkey = key_ref_to_ptr(authkey_ref);
if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
key_put(authkey);
authkey = ERR_PTR(-EKEYREVOKED);
}
error:
return authkey;
}
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