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Merge tag 'keys-next-20200602' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull keyring updates from David Howells:

 - Fix a documentation warning.

 - Replace a zero-length array with a flexible one

 - Make the big_key key type use ChaCha20Poly1305 and use the crypto
   algorithm directly rather than going through the crypto layer.

 - Implement the update op for the big_key type.

* tag 'keys-next-20200602' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  keys: Implement update for the big_key type
  security/keys: rewrite big_key crypto to use library interface
  KEYS: Replace zero-length array with flexible-array
  Documentation: security: core.rst: add missing argument
This commit is contained in:
Linus Torvalds 2020-06-04 10:27:07 -07:00
commit a484a497c9
5 changed files with 60 additions and 212 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
Documentation/security/keys/core.rst
View File

@ -920,10 +920,14 @@ The keyctl syscall functions are:
long keyctl(KEYCTL_PKEY_QUERY,
key_serial_t key_id, unsigned long reserved,
const char *params,
struct keyctl_pkey_query *info);
Get information about an asymmetric key. The information is returned in
the keyctl_pkey_query struct::
Get information about an asymmetric key. Specific algorithms and
encodings may be queried by using the ``params`` argument. This is a
string containing a space- or tab-separated string of key-value pairs.
Currently supported keys include ``enc`` and ``hash``. The information
is returned in the keyctl_pkey_query struct::
__u32 supported_ops;
__u32 key_size;

1
include/keys/big_key-type.h
View File

@ -18,5 +18,6 @@ extern void big_key_revoke(struct key *key);
extern void big_key_destroy(struct key *key);
extern void big_key_describe(const struct key *big_key, struct seq_file *m);
extern long big_key_read(const struct key *key, char *buffer, size_t buflen);
extern int big_key_update(struct key *key, struct key_preparsed_payload *prep);
#endif /* _KEYS_BIG_KEY_TYPE_H */

2
include/keys/user-type.h
View File

@ -27,7 +27,7 @@
struct user_key_payload {
struct rcu_head rcu; /* RCU destructor */
unsigned short datalen; /* length of this data */
char data[0] __aligned(__alignof__(u64)); /* actual data */
char data[] __aligned(__alignof__(u64)); /* actual data */
};
extern struct key_type key_type_user;

4
security/keys/Kconfig
View File

@ -60,9 +60,7 @@ config BIG_KEYS
bool "Large payload keys"
depends on KEYS
depends on TMPFS
select CRYPTO
select CRYPTO_AES
select CRYPTO_GCM
depends on CRYPTO_LIB_CHACHA20POLY1305 = y
help
This option provides support for holding large keys within the kernel
(for example Kerberos ticket caches). The data may be stored out to

257
security/keys/big_key.c
View File

@ -1,7 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/* Large capacity key type
*
* Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
* Copyright (C) 2017-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
* Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
@ -12,20 +12,10 @@
#include <linux/file.h>
#include <linux/shmem_fs.h>
#include <linux/err.h>
#include <linux/scatterlist.h>
#include <linux/random.h>
#include <linux/vmalloc.h>
#include <keys/user-type.h>
#include <keys/big_key-type.h>
#include <crypto/aead.h>
#include <crypto/gcm.h>
struct big_key_buf {
unsigned int nr_pages;
void *virt;
struct scatterlist *sg;
struct page *pages[];
};
#include <crypto/chacha20poly1305.h>
/*
* Layout of key payload words.
@ -37,14 +27,6 @@ enum {
big_key_len,
};
/*
* Crypto operation with big_key data
*/
enum big_key_op {
BIG_KEY_ENC,
BIG_KEY_DEC,
};
/*
* If the data is under this limit, there's no point creating a shm file to
* hold it as the permanently resident metadata for the shmem fs will be at
@ -52,16 +34,6 @@ enum big_key_op {
*/
#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
/*
* Key size for big_key data encryption
*/
#define ENC_KEY_SIZE 32
/*
* Authentication tag length
*/
#define ENC_AUTHTAG_SIZE 16
/*
* big_key defined keys take an arbitrary string as the description and an
* arbitrary blob of data as the payload
@ -75,136 +47,20 @@ struct key_type key_type_big_key = {
.destroy = big_key_destroy,
.describe = big_key_describe,
.read = big_key_read,
/* no ->update(); don't add it without changing big_key_crypt() nonce */
.update = big_key_update,
};
/*
* Crypto names for big_key data authenticated encryption
*/
static const char big_key_alg_name[] = "gcm(aes)";
#define BIG_KEY_IV_SIZE GCM_AES_IV_SIZE
/*
* Crypto algorithms for big_key data authenticated encryption
*/
static struct crypto_aead *big_key_aead;
/*
* Since changing the key affects the entire object, we need a mutex.
*/
static DEFINE_MUTEX(big_key_aead_lock);
/*
* Encrypt/decrypt big_key data
*/
static int big_key_crypt(enum big_key_op op, struct big_key_buf *buf, size_t datalen, u8 *key)
{
int ret;
struct aead_request *aead_req;
/* We always use a zero nonce. The reason we can get away with this is
* because we're using a different randomly generated key for every
* different encryption. Notably, too, key_type_big_key doesn't define
* an .update function, so there's no chance we'll wind up reusing the
* key to encrypt updated data. Simply put: one key, one encryption.
*/
u8 zero_nonce[BIG_KEY_IV_SIZE];
aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL);
if (!aead_req)
return -ENOMEM;
memset(zero_nonce, 0, sizeof(zero_nonce));
aead_request_set_crypt(aead_req, buf->sg, buf->sg, datalen, zero_nonce);
aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
aead_request_set_ad(aead_req, 0);
mutex_lock(&big_key_aead_lock);
if (crypto_aead_setkey(big_key_aead, key, ENC_KEY_SIZE)) {
ret = -EAGAIN;
goto error;
}
if (op == BIG_KEY_ENC)
ret = crypto_aead_encrypt(aead_req);
else
ret = crypto_aead_decrypt(aead_req);
error:
mutex_unlock(&big_key_aead_lock);
aead_request_free(aead_req);
return ret;
}
/*
* Free up the buffer.
*/
static void big_key_free_buffer(struct big_key_buf *buf)
{
unsigned int i;
if (buf->virt) {
memset(buf->virt, 0, buf->nr_pages * PAGE_SIZE);
vunmap(buf->virt);
}
for (i = 0; i < buf->nr_pages; i++)
if (buf->pages[i])
__free_page(buf->pages[i]);
kfree(buf);
}
/*
* Allocate a buffer consisting of a set of pages with a virtual mapping
* applied over them.
*/
static void *big_key_alloc_buffer(size_t len)
{
struct big_key_buf *buf;
unsigned int npg = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned int i, l;
buf = kzalloc(sizeof(struct big_key_buf) +
sizeof(struct page) * npg +
sizeof(struct scatterlist) * npg,
GFP_KERNEL);
if (!buf)
return NULL;
buf->nr_pages = npg;
buf->sg = (void *)(buf->pages + npg);
sg_init_table(buf->sg, npg);
for (i = 0; i < buf->nr_pages; i++) {
buf->pages[i] = alloc_page(GFP_KERNEL);
if (!buf->pages[i])
goto nomem;
l = min_t(size_t, len, PAGE_SIZE);
sg_set_page(&buf->sg[i], buf->pages[i], l, 0);
len -= l;
}
buf->virt = vmap(buf->pages, buf->nr_pages, VM_MAP, PAGE_KERNEL);
if (!buf->virt)
goto nomem;
return buf;
nomem:
big_key_free_buffer(buf);
return NULL;
}
/*
* Preparse a big key
*/
int big_key_preparse(struct key_preparsed_payload *prep)
{
struct big_key_buf *buf;
struct path *path = (struct path *)&prep->payload.data[big_key_path];
struct file *file;
u8 *enckey;
u8 *buf, *enckey;
ssize_t written;
size_t datalen = prep->datalen, enclen = datalen + ENC_AUTHTAG_SIZE;
size_t datalen = prep->datalen;
size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE;
int ret;
if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
@ -220,28 +76,28 @@ int big_key_preparse(struct key_preparsed_payload *prep)
* to be swapped out if needed.
*
* File content is stored encrypted with randomly generated key.
* Since the key is random for each file, we can set the nonce
* to zero, provided we never define a ->update() call.
*/
loff_t pos = 0;
buf = big_key_alloc_buffer(enclen);
buf = kvmalloc(enclen, GFP_KERNEL);
if (!buf)
return -ENOMEM;
memcpy(buf->virt, prep->data, datalen);
/* generate random key */
enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL);
enckey = kmalloc(CHACHA20POLY1305_KEY_SIZE, GFP_KERNEL);
if (!enckey) {
ret = -ENOMEM;
goto error;
}
ret = get_random_bytes_wait(enckey, ENC_KEY_SIZE);
ret = get_random_bytes_wait(enckey, CHACHA20POLY1305_KEY_SIZE);
if (unlikely(ret))
goto err_enckey;
/* encrypt aligned data */
ret = big_key_crypt(BIG_KEY_ENC, buf, datalen, enckey);
if (ret)
goto err_enckey;
/* encrypt data */
chacha20poly1305_encrypt(buf, prep->data, datalen, NULL, 0,
0, enckey);
/* save aligned data to file */
file = shmem_kernel_file_setup("", enclen, 0);
@ -250,11 +106,11 @@ int big_key_preparse(struct key_preparsed_payload *prep)
goto err_enckey;
}
written = kernel_write(file, buf->virt, enclen, &pos);
written = kernel_write(file, buf, enclen, &pos);
if (written != enclen) {
ret = written;
if (written >= 0)
ret = -ENOMEM;
ret = -EIO;
goto err_fput;
}
@ -265,7 +121,8 @@ int big_key_preparse(struct key_preparsed_payload *prep)
*path = file->f_path;
path_get(path);
fput(file);
big_key_free_buffer(buf);
memzero_explicit(buf, enclen);
kvfree(buf);
} else {
/* Just store the data in a buffer */
void *data = kmalloc(datalen, GFP_KERNEL);
@ -283,7 +140,8 @@ err_fput:
err_enckey:
kzfree(enckey);
error:
big_key_free_buffer(buf);
memzero_explicit(buf, enclen);
kvfree(buf);
return ret;
}
@ -333,6 +191,23 @@ void big_key_destroy(struct key *key)
key->payload.data[big_key_data] = NULL;
}
/*
* Update a big key
*/
int big_key_update(struct key *key, struct key_preparsed_payload *prep)
{
int ret;
ret = key_payload_reserve(key, prep->datalen);
if (ret < 0)
return ret;
if (key_is_positive(key))
big_key_destroy(key);
return generic_key_instantiate(key, prep);
}
/*
* describe the big_key key
*/
@ -361,14 +236,13 @@ long big_key_read(const struct key *key, char *buffer, size_t buflen)
return datalen;
if (datalen > BIG_KEY_FILE_THRESHOLD) {
struct big_key_buf *buf;
struct path *path = (struct path *)&key->payload.data[big_key_path];
struct file *file;
u8 *enckey = (u8 *)key->payload.data[big_key_data];
size_t enclen = datalen + ENC_AUTHTAG_SIZE;
u8 *buf, *enckey = (u8 *)key->payload.data[big_key_data];
size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE;
loff_t pos = 0;
buf = big_key_alloc_buffer(enclen);
buf = kvmalloc(enclen, GFP_KERNEL);
if (!buf)
return -ENOMEM;
@ -379,25 +253,28 @@ long big_key_read(const struct key *key, char *buffer, size_t buflen)
}
/* read file to kernel and decrypt */
ret = kernel_read(file, buf->virt, enclen, &pos);
if (ret >= 0 && ret != enclen) {
ret = -EIO;
ret = kernel_read(file, buf, enclen, &pos);
if (ret != enclen) {
if (ret >= 0)
ret = -EIO;
goto err_fput;
}
ret = big_key_crypt(BIG_KEY_DEC, buf, enclen, enckey);
if (ret)
ret = chacha20poly1305_decrypt(buf, buf, enclen, NULL, 0, 0,
enckey) ? 0 : -EBADMSG;
if (unlikely(ret))
goto err_fput;
ret = datalen;
/* copy out decrypted data */
memcpy(buffer, buf->virt, datalen);
memcpy(buffer, buf, datalen);
err_fput:
fput(file);
error:
big_key_free_buffer(buf);
memzero_explicit(buf, enclen);
kvfree(buf);
} else {
ret = datalen;
memcpy(buffer, key->payload.data[big_key_data], datalen);
@ -411,39 +288,7 @@ error:
*/
static int __init big_key_init(void)
{
int ret;
/* init block cipher */
big_key_aead = crypto_alloc_aead(big_key_alg_name, 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(big_key_aead)) {
ret = PTR_ERR(big_key_aead);
pr_err("Can't alloc crypto: %d\n", ret);
return ret;
}
if (unlikely(crypto_aead_ivsize(big_key_aead) != BIG_KEY_IV_SIZE)) {
WARN(1, "big key algorithm changed?");
ret = -EINVAL;
goto free_aead;
}
ret = crypto_aead_setauthsize(big_key_aead, ENC_AUTHTAG_SIZE);
if (ret < 0) {
pr_err("Can't set crypto auth tag len: %d\n", ret);
goto free_aead;
}
ret = register_key_type(&key_type_big_key);
if (ret < 0) {
pr_err("Can't register type: %d\n", ret);
goto free_aead;
}
return 0;
free_aead:
crypto_free_aead(big_key_aead);
return ret;
return register_key_type(&key_type_big_key);
}
late_initcall(big_key_init);