linux-stable/security/keys/request_key_auth.c
Azeem Shaikh 604b8e7558 KEYS: Replace all non-returning strlcpy with strscpy
strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
2023-08-17 20:12:35 +00:00

283 lines
7.1 KiB
C

// 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 (dhowells@redhat.com)
*
* 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;
}