[linux-block.git] / security / keys / big_key.c

// 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) 2013 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) "big_key: "fmt
#include <linux/init.h>
#include <linux/seq_file.h>
#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[];
};

/*
 * Layout of key payload words.
 */
enum {
	big_key_data,
	big_key_path,
	big_key_path_2nd_part,
	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
 * least as large as the data.
 */
#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
 */
struct key_type key_type_big_key = {
	.name			= "big_key",
	.preparse		= big_key_preparse,
	.free_preparse		= big_key_free_preparse,
	.instantiate		= generic_key_instantiate,
	.revoke			= big_key_revoke,
	.destroy		= big_key_destroy,
	.describe		= big_key_describe,
	.read			= big_key_read,
	/* no ->update(); don't add it without changing big_key_crypt() nonce */
};

/*
 * 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;
	ssize_t written;
	size_t datalen = prep->datalen, enclen = datalen + ENC_AUTHTAG_SIZE;
	int ret;

	if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
		return -EINVAL;

	/* Set an arbitrary quota */
	prep->quotalen = 16;

	prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;

	if (datalen > BIG_KEY_FILE_THRESHOLD) {
		/* Create a shmem file to store the data in.  This will permit the data
		 * to be swapped out if needed.
		 *
		 * File content is stored encrypted with randomly generated key.
		 */
		loff_t pos = 0;

		buf = big_key_alloc_buffer(enclen);
		if (!buf)
			return -ENOMEM;
		memcpy(buf->virt, prep->data, datalen);

		/* generate random key */
		enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL);
		if (!enckey) {
			ret = -ENOMEM;
			goto error;
		}
		ret = get_random_bytes_wait(enckey, ENC_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;

		/* save aligned data to file */
		file = shmem_kernel_file_setup("", enclen, 0);
		if (IS_ERR(file)) {
			ret = PTR_ERR(file);
			goto err_enckey;
		}

		written = kernel_write(file, buf->virt, enclen, &pos);
		if (written != enclen) {
			ret = written;
			if (written >= 0)
				ret = -ENOMEM;
			goto err_fput;
		}

		/* Pin the mount and dentry to the key so that we can open it again
		 * later
		 */
		prep->payload.data[big_key_data] = enckey;
		*path = file->f_path;
		path_get(path);
		fput(file);
		big_key_free_buffer(buf);
	} else {
		/* Just store the data in a buffer */
		void *data = kmalloc(datalen, GFP_KERNEL);

		if (!data)
			return -ENOMEM;

		prep->payload.data[big_key_data] = data;
		memcpy(data, prep->data, prep->datalen);
	}
	return 0;

err_fput:
	fput(file);
err_enckey:
	kzfree(enckey);
error:
	big_key_free_buffer(buf);
	return ret;
}

/*
 * Clear preparsement.
 */
void big_key_free_preparse(struct key_preparsed_payload *prep)
{
	if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
		struct path *path = (struct path *)&prep->payload.data[big_key_path];

		path_put(path);
	}
	kzfree(prep->payload.data[big_key_data]);
}

/*
 * dispose of the links from a revoked keyring
 * - called with the key sem write-locked
 */
void big_key_revoke(struct key *key)
{
	struct path *path = (struct path *)&key->payload.data[big_key_path];

	/* clear the quota */
	key_payload_reserve(key, 0);
	if (key_is_positive(key) &&
	    (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
		vfs_truncate(path, 0);
}

/*
 * dispose of the data dangling from the corpse of a big_key key
 */
void big_key_destroy(struct key *key)
{
	size_t datalen = (size_t)key->payload.data[big_key_len];

	if (datalen > BIG_KEY_FILE_THRESHOLD) {
		struct path *path = (struct path *)&key->payload.data[big_key_path];

		path_put(path);
		path->mnt = NULL;
		path->dentry = NULL;
	}
	kzfree(key->payload.data[big_key_data]);
	key->payload.data[big_key_data] = NULL;
}

/*
 * describe the big_key key
 */
void big_key_describe(const struct key *key, struct seq_file *m)
{
	size_t datalen = (size_t)key->payload.data[big_key_len];

	seq_puts(m, key->description);

	if (key_is_positive(key))
		seq_printf(m, ": %zu [%s]",
			   datalen,
			   datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
}

/*
 * read the key data
 * - the key's semaphore is read-locked
 */
long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
{
	size_t datalen = (size_t)key->payload.data[big_key_len];
	long ret;

	if (!buffer || buflen < datalen)
		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;
		loff_t pos = 0;

		buf = big_key_alloc_buffer(enclen);
		if (!buf)
			return -ENOMEM;

		file = dentry_open(path, O_RDONLY, current_cred());
		if (IS_ERR(file)) {
			ret = PTR_ERR(file);
			goto error;
		}

		/* read file to kernel and decrypt */
		ret = kernel_read(file, buf->virt, enclen, &pos);
		if (ret >= 0 && ret != enclen) {
			ret = -EIO;
			goto err_fput;
		}

		ret = big_key_crypt(BIG_KEY_DEC, buf, enclen, enckey);
		if (ret)
			goto err_fput;

		ret = datalen;

		/* copy decrypted data to user */
		if (copy_to_user(buffer, buf->virt, datalen) != 0)
			ret = -EFAULT;

err_fput:
		fput(file);
error:
		big_key_free_buffer(buf);
	} else {
		ret = datalen;
		if (copy_to_user(buffer, key->payload.data[big_key_data],
				 datalen) != 0)
			ret = -EFAULT;
	}

	return ret;
}

/*
 * Register key type
 */
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;
}

late_initcall(big_key_init);
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0-or-later
	2	/* Large capacity key type
	3	*
	4	* Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
	5	* Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
	6	* Written by David Howells (dhowells@redhat.com)
	7	*/
	8
	9	#define pr_fmt(fmt) "big_key: "fmt
	10	#include <linux/init.h>
	11	#include <linux/seq_file.h>
	12	#include <linux/file.h>
	13	#include <linux/shmem_fs.h>
	14	#include <linux/err.h>
	15	#include <linux/scatterlist.h>
	16	#include <linux/random.h>
	17	#include <linux/vmalloc.h>
	18	#include <keys/user-type.h>
	19	#include <keys/big_key-type.h>
	20	#include <crypto/aead.h>
	21	#include <crypto/gcm.h>
	22
	23	struct big_key_buf {
	24	unsigned int nr_pages;
	25	void *virt;
	26	struct scatterlist *sg;
	27	struct page *pages[];
	28	};
	29
	30	/*
	31	* Layout of key payload words.
	32	*/
	33	enum {
	34	big_key_data,
	35	big_key_path,
	36	big_key_path_2nd_part,
	37	big_key_len,
	38	};
	39
	40	/*
	41	* Crypto operation with big_key data
	42	*/
	43	enum big_key_op {
	44	BIG_KEY_ENC,
	45	BIG_KEY_DEC,
	46	};
	47
	48	/*
	49	* If the data is under this limit, there's no point creating a shm file to
	50	* hold it as the permanently resident metadata for the shmem fs will be at
	51	* least as large as the data.
	52	*/
	53	#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
	54
	55	/*
	56	* Key size for big_key data encryption
	57	*/
	58	#define ENC_KEY_SIZE 32
	59
	60	/*
	61	* Authentication tag length
	62	*/
	63	#define ENC_AUTHTAG_SIZE 16
	64
	65	/*
	66	* big_key defined keys take an arbitrary string as the description and an
	67	* arbitrary blob of data as the payload
	68	*/
	69	struct key_type key_type_big_key = {
	70	.name = "big_key",
	71	.preparse = big_key_preparse,
	72	.free_preparse = big_key_free_preparse,
	73	.instantiate = generic_key_instantiate,
	74	.revoke = big_key_revoke,
	75	.destroy = big_key_destroy,
	76	.describe = big_key_describe,
	77	.read = big_key_read,
	78	/* no ->update(); don't add it without changing big_key_crypt() nonce */
	79	};
	80
	81	/*
	82	* Crypto names for big_key data authenticated encryption
	83	*/
	84	static const char big_key_alg_name[] = "gcm(aes)";
	85	#define BIG_KEY_IV_SIZE GCM_AES_IV_SIZE
	86
	87	/*
	88	* Crypto algorithms for big_key data authenticated encryption
	89	*/
	90	static struct crypto_aead *big_key_aead;
	91
	92	/*
	93	* Since changing the key affects the entire object, we need a mutex.
	94	*/
	95	static DEFINE_MUTEX(big_key_aead_lock);
	96
	97	/*
	98	* Encrypt/decrypt big_key data
	99	*/
	100	static int big_key_crypt(enum big_key_op op, struct big_key_buf buf, size_t datalen, u8 key)
	101	{
	102	int ret;
	103	struct aead_request *aead_req;
	104	/* We always use a zero nonce. The reason we can get away with this is
	105	* because we're using a different randomly generated key for every
	106	* different encryption. Notably, too, key_type_big_key doesn't define
	107	* an .update function, so there's no chance we'll wind up reusing the
	108	* key to encrypt updated data. Simply put: one key, one encryption.
	109	*/
	110	u8 zero_nonce[BIG_KEY_IV_SIZE];
	111
	112	aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL);
	113	if (!aead_req)
	114	return -ENOMEM;
	115
	116	memset(zero_nonce, 0, sizeof(zero_nonce));
	117	aead_request_set_crypt(aead_req, buf->sg, buf->sg, datalen, zero_nonce);
	118	aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
	119	aead_request_set_ad(aead_req, 0);
	120
	121	mutex_lock(&big_key_aead_lock);
	122	if (crypto_aead_setkey(big_key_aead, key, ENC_KEY_SIZE)) {
	123	ret = -EAGAIN;
	124	goto error;
	125	}
	126	if (op == BIG_KEY_ENC)
	127	ret = crypto_aead_encrypt(aead_req);
	128	else
	129	ret = crypto_aead_decrypt(aead_req);
	130	error:
	131	mutex_unlock(&big_key_aead_lock);
	132	aead_request_free(aead_req);
	133	return ret;
	134	}
	135
	136	/*
	137	* Free up the buffer.
	138	*/
	139	static void big_key_free_buffer(struct big_key_buf *buf)
	140	{
	141	unsigned int i;
	142
	143	if (buf->virt) {
	144	memset(buf->virt, 0, buf->nr_pages * PAGE_SIZE);
	145	vunmap(buf->virt);
	146	}
	147
	148	for (i = 0; i < buf->nr_pages; i++)
	149	if (buf->pages[i])
	150	__free_page(buf->pages[i]);
	151
	152	kfree(buf);
	153	}
	154
	155	/*
	156	* Allocate a buffer consisting of a set of pages with a virtual mapping
	157	* applied over them.
	158	*/
	159	static void *big_key_alloc_buffer(size_t len)
	160	{
	161	struct big_key_buf *buf;
	162	unsigned int npg = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
	163	unsigned int i, l;
	164
	165	buf = kzalloc(sizeof(struct big_key_buf) +
	166	sizeof(struct page) * npg +
	167	sizeof(struct scatterlist) * npg,
	168	GFP_KERNEL);
	169	if (!buf)
	170	return NULL;
	171
	172	buf->nr_pages = npg;
	173	buf->sg = (void *)(buf->pages + npg);
	174	sg_init_table(buf->sg, npg);
	175
	176	for (i = 0; i < buf->nr_pages; i++) {
	177	buf->pages[i] = alloc_page(GFP_KERNEL);
	178	if (!buf->pages[i])
	179	goto nomem;
	180
	181	l = min_t(size_t, len, PAGE_SIZE);
	182	sg_set_page(&buf->sg[i], buf->pages[i], l, 0);
	183	len -= l;
	184	}
	185
	186	buf->virt = vmap(buf->pages, buf->nr_pages, VM_MAP, PAGE_KERNEL);
	187	if (!buf->virt)
	188	goto nomem;
	189
	190	return buf;
	191
	192	nomem:
	193	big_key_free_buffer(buf);
	194	return NULL;
	195	}
	196
	197	/*
	198	* Preparse a big key
	199	*/
	200	int big_key_preparse(struct key_preparsed_payload *prep)
	201	{
	202	struct big_key_buf *buf;
	203	struct path path = (struct path )&prep->payload.data[big_key_path];
	204	struct file *file;
	205	u8 *enckey;
	206	ssize_t written;
	207	size_t datalen = prep->datalen, enclen = datalen + ENC_AUTHTAG_SIZE;
	208	int ret;
	209
	210	if (datalen <= 0 \|\| datalen > 1024 * 1024 \|\| !prep->data)
	211	return -EINVAL;
	212
	213	/* Set an arbitrary quota */
	214	prep->quotalen = 16;
	215
	216	prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;
	217
	218	if (datalen > BIG_KEY_FILE_THRESHOLD) {
	219	/* Create a shmem file to store the data in. This will permit the data
	220	* to be swapped out if needed.
	221	*
	222	* File content is stored encrypted with randomly generated key.
	223	*/
	224	loff_t pos = 0;
	225
	226	buf = big_key_alloc_buffer(enclen);
	227	if (!buf)
	228	return -ENOMEM;
	229	memcpy(buf->virt, prep->data, datalen);
	230
	231	/* generate random key */
	232	enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL);
	233	if (!enckey) {
	234	ret = -ENOMEM;
	235	goto error;
	236	}
	237	ret = get_random_bytes_wait(enckey, ENC_KEY_SIZE);
	238	if (unlikely(ret))
	239	goto err_enckey;
	240
	241	/* encrypt aligned data */
	242	ret = big_key_crypt(BIG_KEY_ENC, buf, datalen, enckey);
	243	if (ret)
	244	goto err_enckey;
	245
	246	/* save aligned data to file */
	247	file = shmem_kernel_file_setup("", enclen, 0);
	248	if (IS_ERR(file)) {
	249	ret = PTR_ERR(file);
	250	goto err_enckey;
	251	}
	252
	253	written = kernel_write(file, buf->virt, enclen, &pos);
	254	if (written != enclen) {
	255	ret = written;
	256	if (written >= 0)
	257	ret = -ENOMEM;
	258	goto err_fput;
	259	}
	260
	261	/* Pin the mount and dentry to the key so that we can open it again
	262	* later
	263	*/
	264	prep->payload.data[big_key_data] = enckey;
	265	*path = file->f_path;
	266	path_get(path);
	267	fput(file);
	268	big_key_free_buffer(buf);
	269	} else {
	270	/* Just store the data in a buffer */
	271	void *data = kmalloc(datalen, GFP_KERNEL);
	272
	273	if (!data)
	274	return -ENOMEM;
	275
	276	prep->payload.data[big_key_data] = data;
	277	memcpy(data, prep->data, prep->datalen);
	278	}
	279	return 0;
	280
	281	err_fput:
	282	fput(file);
	283	err_enckey:
	284	kzfree(enckey);
	285	error:
	286	big_key_free_buffer(buf);
	287	return ret;
	288	}
	289
	290	/*
	291	* Clear preparsement.
	292	*/
	293	void big_key_free_preparse(struct key_preparsed_payload *prep)
	294	{
	295	if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
	296	struct path path = (struct path )&prep->payload.data[big_key_path];
	297
	298	path_put(path);
	299	}
	300	kzfree(prep->payload.data[big_key_data]);
	301	}
	302
	303	/*
	304	* dispose of the links from a revoked keyring
	305	* - called with the key sem write-locked
	306	*/
	307	void big_key_revoke(struct key *key)
	308	{
	309	struct path path = (struct path )&key->payload.data[big_key_path];
	310
	311	/* clear the quota */
	312	key_payload_reserve(key, 0);
	313	if (key_is_positive(key) &&
	314	(size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
	315	vfs_truncate(path, 0);
	316	}
	317
	318	/*
	319	* dispose of the data dangling from the corpse of a big_key key
	320	*/
	321	void big_key_destroy(struct key *key)
	322	{
	323	size_t datalen = (size_t)key->payload.data[big_key_len];
	324
	325	if (datalen > BIG_KEY_FILE_THRESHOLD) {
	326	struct path path = (struct path )&key->payload.data[big_key_path];
	327
	328	path_put(path);
	329	path->mnt = NULL;
	330	path->dentry = NULL;
	331	}
	332	kzfree(key->payload.data[big_key_data]);
	333	key->payload.data[big_key_data] = NULL;
	334	}
	335
	336	/*
	337	* describe the big_key key
	338	*/
	339	void big_key_describe(const struct key key, struct seq_file m)
	340	{
	341	size_t datalen = (size_t)key->payload.data[big_key_len];
	342
	343	seq_puts(m, key->description);
	344
	345	if (key_is_positive(key))
	346	seq_printf(m, ": %zu [%s]",
	347	datalen,
	348	datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
	349	}
	350
	351	/*
	352	* read the key data
	353	* - the key's semaphore is read-locked
	354	*/
	355	long big_key_read(const struct key key, char __user buffer, size_t buflen)
	356	{
	357	size_t datalen = (size_t)key->payload.data[big_key_len];
	358	long ret;
	359
	360	if (!buffer \|\| buflen < datalen)
	361	return datalen;
	362
	363	if (datalen > BIG_KEY_FILE_THRESHOLD) {
	364	struct big_key_buf *buf;
	365	struct path path = (struct path )&key->payload.data[big_key_path];
	366	struct file *file;
	367	u8 enckey = (u8 )key->payload.data[big_key_data];
	368	size_t enclen = datalen + ENC_AUTHTAG_SIZE;
	369	loff_t pos = 0;
	370
	371	buf = big_key_alloc_buffer(enclen);
	372	if (!buf)
	373	return -ENOMEM;
	374
	375	file = dentry_open(path, O_RDONLY, current_cred());
	376	if (IS_ERR(file)) {
	377	ret = PTR_ERR(file);
	378	goto error;
	379	}
	380
	381	/* read file to kernel and decrypt */
	382	ret = kernel_read(file, buf->virt, enclen, &pos);
	383	if (ret >= 0 && ret != enclen) {
	384	ret = -EIO;
	385	goto err_fput;
	386	}
	387
	388	ret = big_key_crypt(BIG_KEY_DEC, buf, enclen, enckey);
	389	if (ret)
	390	goto err_fput;
	391
	392	ret = datalen;
	393
	394	/* copy decrypted data to user */
	395	if (copy_to_user(buffer, buf->virt, datalen) != 0)
	396	ret = -EFAULT;
	397
	398	err_fput:
	399	fput(file);
	400	error:
	401	big_key_free_buffer(buf);
	402	} else {
	403	ret = datalen;
	404	if (copy_to_user(buffer, key->payload.data[big_key_data],
	405	datalen) != 0)
	406	ret = -EFAULT;
	407	}
	408
	409	return ret;
	410	}
	411
	412	/*
	413	* Register key type
	414	*/
	415	static int __init big_key_init(void)
	416	{
	417	int ret;
	418
	419	/* init block cipher */
	420	big_key_aead = crypto_alloc_aead(big_key_alg_name, 0, CRYPTO_ALG_ASYNC);
	421	if (IS_ERR(big_key_aead)) {
	422	ret = PTR_ERR(big_key_aead);
	423	pr_err("Can't alloc crypto: %d\n", ret);
	424	return ret;
	425	}
	426
	427	if (unlikely(crypto_aead_ivsize(big_key_aead) != BIG_KEY_IV_SIZE)) {
	428	WARN(1, "big key algorithm changed?");
	429	ret = -EINVAL;
	430	goto free_aead;
	431	}
	432
	433	ret = crypto_aead_setauthsize(big_key_aead, ENC_AUTHTAG_SIZE);
	434	if (ret < 0) {
	435	pr_err("Can't set crypto auth tag len: %d\n", ret);
	436	goto free_aead;
	437	}
	438
	439	ret = register_key_type(&key_type_big_key);
	440	if (ret < 0) {
	441	pr_err("Can't register type: %d\n", ret);
	442	goto free_aead;
	443	}
	444
	445	return 0;
	446
	447	free_aead:
	448	crypto_free_aead(big_key_aead);
	449	return ret;
	450	}
	451
	452	late_initcall(big_key_init);