[mirror_ubuntu-bionic-kernel.git] / security / integrity / evm / evm_crypto.c

/*
 * Copyright (C) 2005-2010 IBM Corporation
 *
 * Authors:
 * Mimi Zohar <zohar@us.ibm.com>
 * Kylene Hall <kjhall@us.ibm.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 2 of the License.
 *
 * File: evm_crypto.c
 *	 Using root's kernel master key (kmk), calculate the HMAC
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/xattr.h>
#include <linux/evm.h>
#include <keys/encrypted-type.h>
#include <crypto/hash.h>
#include "evm.h"

#define EVMKEY "evm-key"
#define MAX_KEY_SIZE 128
static unsigned char evmkey[MAX_KEY_SIZE];
static int evmkey_len = MAX_KEY_SIZE;

struct crypto_shash *hmac_tfm;
struct crypto_shash *hash_tfm;

static DEFINE_MUTEX(mutex);

#define EVM_SET_KEY_BUSY 0

static unsigned long evm_set_key_flags;

/**
 * evm_set_key() - set EVM HMAC key from the kernel
 * @key: pointer to a buffer with the key data
 * @size: length of the key data
 *
 * This function allows setting the EVM HMAC key from the kernel
 * without using the "encrypted" key subsystem keys. It can be used
 * by the crypto HW kernel module which has its own way of managing
 * keys.
 *
 * key length should be between 32 and 128 bytes long
 */
int evm_set_key(void *key, size_t keylen)
{
	int rc;

	rc = -EBUSY;
	if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags))
		goto busy;
	rc = -EINVAL;
	if (keylen > MAX_KEY_SIZE)
		goto inval;
	memcpy(evmkey, key, keylen);
	evm_initialized |= EVM_INIT_HMAC;
	pr_info("key initialized\n");
	return 0;
inval:
	clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
busy:
	pr_err("key initialization failed\n");
	return rc;
}
EXPORT_SYMBOL_GPL(evm_set_key);

static struct shash_desc *init_desc(char type)
{
	long rc;
	char *algo;
	struct crypto_shash **tfm;
	struct shash_desc *desc;

	if (type == EVM_XATTR_HMAC) {
		if (!(evm_initialized & EVM_INIT_HMAC)) {
			pr_err_once("HMAC key is not set\n");
			return ERR_PTR(-ENOKEY);
		}
		tfm = &hmac_tfm;
		algo = evm_hmac;
	} else {
		tfm = &hash_tfm;
		algo = evm_hash;
	}

	if (*tfm == NULL) {
		mutex_lock(&mutex);
		if (*tfm)
			goto out;
		*tfm = crypto_alloc_shash(algo, 0,
					  CRYPTO_ALG_ASYNC | CRYPTO_NOLOAD);
		if (IS_ERR(*tfm)) {
			rc = PTR_ERR(*tfm);
			pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
			*tfm = NULL;
			mutex_unlock(&mutex);
			return ERR_PTR(rc);
		}
		if (type == EVM_XATTR_HMAC) {
			rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
			if (rc) {
				crypto_free_shash(*tfm);
				*tfm = NULL;
				mutex_unlock(&mutex);
				return ERR_PTR(rc);
			}
		}
out:
		mutex_unlock(&mutex);
	}

	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
			GFP_KERNEL);
	if (!desc)
		return ERR_PTR(-ENOMEM);

	desc->tfm = *tfm;
	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

	rc = crypto_shash_init(desc);
	if (rc) {
		kfree(desc);
		return ERR_PTR(rc);
	}
	return desc;
}

/* Protect against 'cutting & pasting' security.evm xattr, include inode
 * specific info.
 *
 * (Additional directory/file metadata needs to be added for more complete
 * protection.)
 */
static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
			  char type, char *digest)
{
	struct h_misc {
		unsigned long ino;
		__u32 generation;
		uid_t uid;
		gid_t gid;
		umode_t mode;
	} hmac_misc;

	memset(&hmac_misc, 0, sizeof(hmac_misc));
	/* Don't include the inode or generation number in portable
	 * signatures
	 */
	if (type != EVM_XATTR_PORTABLE_DIGSIG) {
		hmac_misc.ino = inode->i_ino;
		hmac_misc.generation = inode->i_generation;
	}
	/* The hmac uid and gid must be encoded in the initial user
	 * namespace (not the filesystems user namespace) as encoding
	 * them in the filesystems user namespace allows an attack
	 * where first they are written in an unprivileged fuse mount
	 * of a filesystem and then the system is tricked to mount the
	 * filesystem for real on next boot and trust it because
	 * everything is signed.
	 */
	hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
	hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
	hmac_misc.mode = inode->i_mode;
	crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
	if ((evm_hmac_attrs & EVM_ATTR_FSUUID) &&
	    type != EVM_XATTR_PORTABLE_DIGSIG)
		crypto_shash_update(desc, &inode->i_sb->s_uuid.b[0],
				    sizeof(inode->i_sb->s_uuid));
	crypto_shash_final(desc, digest);
}

/*
 * Calculate the HMAC value across the set of protected security xattrs.
 *
 * Instead of retrieving the requested xattr, for performance, calculate
 * the hmac using the requested xattr value. Don't alloc/free memory for
 * each xattr, but attempt to re-use the previously allocated memory.
 */
static int evm_calc_hmac_or_hash(struct dentry *dentry,
				const char *req_xattr_name,
				const char *req_xattr_value,
				size_t req_xattr_value_len,
				char type, char *digest)
{
	struct inode *inode = d_backing_inode(dentry);
	struct shash_desc *desc;
	char **xattrname;
	size_t xattr_size = 0;
	char *xattr_value = NULL;
	int error;
	int size;
	bool ima_present = false;

	if (!(inode->i_opflags & IOP_XATTR) ||
	    inode->i_sb->s_user_ns != &init_user_ns)
		return -EOPNOTSUPP;

	desc = init_desc(type);
	if (IS_ERR(desc))
		return PTR_ERR(desc);

	error = -ENODATA;
	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
		bool is_ima = false;

		if (strcmp(*xattrname, XATTR_NAME_IMA) == 0)
			is_ima = true;

		if ((req_xattr_name && req_xattr_value)
		    && !strcmp(*xattrname, req_xattr_name)) {
			error = 0;
			crypto_shash_update(desc, (const u8 *)req_xattr_value,
					     req_xattr_value_len);
			if (is_ima)
				ima_present = true;
			continue;
		}
		size = vfs_getxattr_alloc(dentry, *xattrname,
					  &xattr_value, xattr_size, GFP_NOFS);
		if (size == -ENOMEM) {
			error = -ENOMEM;
			goto out;
		}
		if (size < 0)
			continue;

		error = 0;
		xattr_size = size;
		crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
		if (is_ima)
			ima_present = true;
	}
	hmac_add_misc(desc, inode, type, digest);

	/* Portable EVM signatures must include an IMA hash */
	if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present)
		return -EPERM;
out:
	kfree(xattr_value);
	kfree(desc);
	return error;
}

int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
		  const char *req_xattr_value, size_t req_xattr_value_len,
		  char *digest)
{
	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
			       req_xattr_value_len, EVM_XATTR_HMAC, digest);
}

int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
		  const char *req_xattr_value, size_t req_xattr_value_len,
		  char type, char *digest)
{
	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
				     req_xattr_value_len, type, digest);
}

static int evm_is_immutable(struct dentry *dentry, struct inode *inode)
{
	const struct evm_ima_xattr_data *xattr_data = NULL;
	struct integrity_iint_cache *iint;
	int rc = 0;

	iint = integrity_iint_find(inode);
	if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG))
		return 1;

	/* Do this the hard way */
	rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
				GFP_NOFS);
	if (rc <= 0) {
		if (rc == -ENODATA)
			return 0;
		return rc;
	}
	if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG)
		rc = 1;
	else
		rc = 0;

	kfree(xattr_data);
	return rc;
}


/*
 * Calculate the hmac and update security.evm xattr
 *
 * Expects to be called with i_mutex locked.
 */
int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
			const char *xattr_value, size_t xattr_value_len)
{
	struct inode *inode = d_backing_inode(dentry);
	struct evm_ima_xattr_data xattr_data;
	int rc = 0;

	/*
	 * Don't permit any transformation of the EVM xattr if the signature
	 * is of an immutable type
	 */
	rc = evm_is_immutable(dentry, inode);
	if (rc < 0)
		return rc;
	if (rc)
		return -EPERM;

	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
			   xattr_value_len, xattr_data.digest);
	if (rc == 0) {
		xattr_data.type = EVM_XATTR_HMAC;
		rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
					   &xattr_data,
					   sizeof(xattr_data), 0);
	} else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
		rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
	}
	return rc;
}

int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
		  char *hmac_val)
{
	struct shash_desc *desc;

	desc = init_desc(EVM_XATTR_HMAC);
	if (IS_ERR(desc)) {
		pr_info("init_desc failed\n");
		return PTR_ERR(desc);
	}

	crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
	hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
	kfree(desc);
	return 0;
}

/*
 * Get the key from the TPM for the SHA1-HMAC
 */
int evm_init_key(void)
{
	struct key *evm_key;
	struct encrypted_key_payload *ekp;
	int rc;

	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
	if (IS_ERR(evm_key))
		return -ENOENT;

	down_read(&evm_key->sem);
	ekp = evm_key->payload.data[0];

	rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);

	/* burn the original key contents */
	memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
	up_read(&evm_key->sem);
	key_put(evm_key);
	return rc;
}
Commit	Line	Data
66dbc325 MZ	1	/*
	2	* Copyright (C) 2005-2010 IBM Corporation
	3	*
	4	* Authors:
	5	* Mimi Zohar <zohar@us.ibm.com>
	6	* Kylene Hall <kjhall@us.ibm.com>
	7	*
	8	* This program is free software; you can redistribute it and/or modify
	9	* it under the terms of the GNU General Public License as published by
	10	* the Free Software Foundation, version 2 of the License.
	11	*
	12	* File: evm_crypto.c
	13	* Using root's kernel master key (kmk), calculate the HMAC
	14	*/
	15
20ee451f JP	16	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
20ee451f JP	17
66dbc325 MZ	18	#include <linux/module.h>
	19	#include <linux/crypto.h>
	20	#include <linux/xattr.h>
76266763	21	#include <linux/evm.h>
66dbc325	22	#include <keys/encrypted-type.h>
d46eb369	23	#include <crypto/hash.h>
66dbc325 MZ	24	#include "evm.h"
	25
	26	#define EVMKEY "evm-key"
	27	#define MAX_KEY_SIZE 128
	28	static unsigned char evmkey[MAX_KEY_SIZE];
	29	static int evmkey_len = MAX_KEY_SIZE;
	30
d46eb369	31	struct crypto_shash *hmac_tfm;
15647eb3	32	struct crypto_shash *hash_tfm;
d46eb369	33
97426f98 DK	34	static DEFINE_MUTEX(mutex);
97426f98 DK	35
76266763 DK	36	#define EVM_SET_KEY_BUSY 0
	37
	38	static unsigned long evm_set_key_flags;
	39
	40	/**
	41	* evm_set_key() - set EVM HMAC key from the kernel
	42	* @key: pointer to a buffer with the key data
	43	* @size: length of the key data
	44	*
	45	* This function allows setting the EVM HMAC key from the kernel
	46	* without using the "encrypted" key subsystem keys. It can be used
	47	* by the crypto HW kernel module which has its own way of managing
	48	* keys.
	49	*
	50	* key length should be between 32 and 128 bytes long
	51	*/
	52	int evm_set_key(void *key, size_t keylen)
	53	{
	54	int rc;
	55
	56	rc = -EBUSY;
	57	if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags))
	58	goto busy;
	59	rc = -EINVAL;
	60	if (keylen > MAX_KEY_SIZE)
	61	goto inval;
	62	memcpy(evmkey, key, keylen);
	63	evm_initialized \|= EVM_INIT_HMAC;
	64	pr_info("key initialized\n");
	65	return 0;
	66	inval:
	67	clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags);
	68	busy:
	69	pr_err("key initialization failed\n");
	70	return rc;
	71	}
	72	EXPORT_SYMBOL_GPL(evm_set_key);
	73
8fcc9954	74	static struct shash_desc *init_desc(char type)
66dbc325	75	{
143b01d3	76	long rc;
15647eb3 DK	77	char *algo;
15647eb3 DK	78	struct crypto_shash **tfm;
d46eb369 DK	79	struct shash_desc *desc;
d46eb369 DK	80
15647eb3	81	if (type == EVM_XATTR_HMAC) {
26ddabfe	82	if (!(evm_initialized & EVM_INIT_HMAC)) {
0485d066	83	pr_err_once("HMAC key is not set\n");
26ddabfe DK	84	return ERR_PTR(-ENOKEY);
26ddabfe DK	85	}
15647eb3 DK	86	tfm = &hmac_tfm;
	87	algo = evm_hmac;
	88	} else {
	89	tfm = &hash_tfm;
	90	algo = evm_hash;
	91	}
	92
	93	if (*tfm == NULL) {
97426f98	94	mutex_lock(&mutex);
143b01d3	95	if (*tfm)
97426f98	96	goto out;
42a729ed MG	97	*tfm = crypto_alloc_shash(algo, 0,
42a729ed MG	98	CRYPTO_ALG_ASYNC \| CRYPTO_NOLOAD);
15647eb3	99	if (IS_ERR(*tfm)) {
15647eb3	100	rc = PTR_ERR(*tfm);
143b01d3	101	pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
15647eb3	102	*tfm = NULL;
97426f98	103	mutex_unlock(&mutex);
d46eb369 DK	104	return ERR_PTR(rc);
d46eb369 DK	105	}
88d7ed35 DK	106	if (type == EVM_XATTR_HMAC) {
	107	rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
	108	if (rc) {
	109	crypto_free_shash(*tfm);
	110	*tfm = NULL;
143b01d3	111	mutex_unlock(&mutex);
88d7ed35 DK	112	return ERR_PTR(rc);
88d7ed35 DK	113	}
d21b5945	114	}
97426f98 DK	115	out:
97426f98 DK	116	mutex_unlock(&mutex);
66dbc325	117	}
d46eb369	118
15647eb3	119	desc = kmalloc(sizeof(desc) + crypto_shash_descsize(tfm),
d46eb369 DK	120	GFP_KERNEL);
	121	if (!desc)
	122	return ERR_PTR(-ENOMEM);
	123
15647eb3	124	desc->tfm = *tfm;
d46eb369 DK	125	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
d46eb369 DK	126
d46eb369	127	rc = crypto_shash_init(desc);
d46eb369 DK	128	if (rc) {
	129	kfree(desc);
	130	return ERR_PTR(rc);
	131	}
	132	return desc;
66dbc325 MZ	133	}
	134
	135	/* Protect against 'cutting & pasting' security.evm xattr, include inode
	136	* specific info.
	137	*
	138	* (Additional directory/file metadata needs to be added for more complete
	139	* protection.)
	140	*/
d46eb369	141	static void hmac_add_misc(struct shash_desc desc, struct inode inode,
21362f43	142	char type, char *digest)
66dbc325 MZ	143	{
	144	struct h_misc {
	145	unsigned long ino;
	146	__u32 generation;
	147	uid_t uid;
	148	gid_t gid;
	149	umode_t mode;
	150	} hmac_misc;
66dbc325	151
2bb930ab	152	memset(&hmac_misc, 0, sizeof(hmac_misc));
21362f43 MG	153	/* Don't include the inode or generation number in portable
	154	* signatures
	155	*/
	156	if (type != EVM_XATTR_PORTABLE_DIGSIG) {
	157	hmac_misc.ino = inode->i_ino;
	158	hmac_misc.generation = inode->i_generation;
	159	}
19339c25 EB	160	/* The hmac uid and gid must be encoded in the initial user
	161	* namespace (not the filesystems user namespace) as encoding
	162	* them in the filesystems user namespace allows an attack
	163	* where first they are written in an unprivileged fuse mount
	164	* of a filesystem and then the system is tricked to mount the
	165	* filesystem for real on next boot and trust it because
	166	* everything is signed.
	167	*/
	168	hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
	169	hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
66dbc325	170	hmac_misc.mode = inode->i_mode;
2bb930ab	171	crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
21362f43 MG	172	if ((evm_hmac_attrs & EVM_ATTR_FSUUID) &&
21362f43 MG	173	type != EVM_XATTR_PORTABLE_DIGSIG)
85787090	174	crypto_shash_update(desc, &inode->i_sb->s_uuid.b[0],
74de6684	175	sizeof(inode->i_sb->s_uuid));
d46eb369	176	crypto_shash_final(desc, digest);
66dbc325 MZ	177	}
	178
	179	/*
	180	* Calculate the HMAC value across the set of protected security xattrs.
	181	*
	182	* Instead of retrieving the requested xattr, for performance, calculate
	183	* the hmac using the requested xattr value. Don't alloc/free memory for
	184	* each xattr, but attempt to re-use the previously allocated memory.
	185	*/
15647eb3 DK	186	static int evm_calc_hmac_or_hash(struct dentry *dentry,
	187	const char *req_xattr_name,
	188	const char *req_xattr_value,
	189	size_t req_xattr_value_len,
	190	char type, char *digest)
66dbc325	191	{
c6f493d6	192	struct inode *inode = d_backing_inode(dentry);
d46eb369	193	struct shash_desc *desc;
66dbc325 MZ	194	char **xattrname;
	195	size_t xattr_size = 0;
	196	char *xattr_value = NULL;
	197	int error;
	198	int size;
21362f43	199	bool ima_present = false;
66dbc325	200
7c026e69 SF	201	if (!(inode->i_opflags & IOP_XATTR) \|\|
7c026e69 SF	202	inode->i_sb->s_user_ns != &init_user_ns)
66dbc325	203	return -EOPNOTSUPP;
5d6c3191	204
15647eb3	205	desc = init_desc(type);
d46eb369 DK	206	if (IS_ERR(desc))
d46eb369 DK	207	return PTR_ERR(desc);
66dbc325 MZ	208
	209	error = -ENODATA;
	210	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
21362f43 MG	211	bool is_ima = false;
	212
	213	if (strcmp(*xattrname, XATTR_NAME_IMA) == 0)
	214	is_ima = true;
	215
66dbc325 MZ	216	if ((req_xattr_name && req_xattr_value)
	217	&& !strcmp(*xattrname, req_xattr_name)) {
	218	error = 0;
d46eb369 DK	219	crypto_shash_update(desc, (const u8 *)req_xattr_value,
d46eb369 DK	220	req_xattr_value_len);
21362f43 MG	221	if (is_ima)
21362f43 MG	222	ima_present = true;
66dbc325 MZ	223	continue;
	224	}
	225	size = vfs_getxattr_alloc(dentry, *xattrname,
	226	&xattr_value, xattr_size, GFP_NOFS);
	227	if (size == -ENOMEM) {
	228	error = -ENOMEM;
	229	goto out;
	230	}
	231	if (size < 0)
	232	continue;
	233
	234	error = 0;
	235	xattr_size = size;
d46eb369	236	crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
21362f43 MG	237	if (is_ima)
21362f43 MG	238	ima_present = true;
66dbc325	239	}
21362f43	240	hmac_add_misc(desc, inode, type, digest);
d46eb369	241
21362f43 MG	242	/* Portable EVM signatures must include an IMA hash */
	243	if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present)
	244	return -EPERM;
66dbc325	245	out:
d46eb369 DK	246	kfree(xattr_value);
d46eb369 DK	247	kfree(desc);
66dbc325 MZ	248	return error;
	249	}
	250
15647eb3 DK	251	int evm_calc_hmac(struct dentry dentry, const char req_xattr_name,
	252	const char *req_xattr_value, size_t req_xattr_value_len,
	253	char *digest)
	254	{
	255	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
21362f43	256	req_xattr_value_len, EVM_XATTR_HMAC, digest);
15647eb3 DK	257	}
	258
	259	int evm_calc_hash(struct dentry dentry, const char req_xattr_name,
	260	const char *req_xattr_value, size_t req_xattr_value_len,
21362f43	261	char type, char *digest)
15647eb3 DK	262	{
15647eb3 DK	263	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
21362f43 MG	264	req_xattr_value_len, type, digest);
	265	}
	266
	267	static int evm_is_immutable(struct dentry dentry, struct inode inode)
	268	{
	269	const struct evm_ima_xattr_data *xattr_data = NULL;
	270	struct integrity_iint_cache *iint;
	271	int rc = 0;
	272
	273	iint = integrity_iint_find(inode);
	274	if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG))
	275	return 1;
	276
	277	/* Do this the hard way */
	278	rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
	279	GFP_NOFS);
	280	if (rc <= 0) {
	281	if (rc == -ENODATA)
	282	return 0;
	283	return rc;
	284	}
	285	if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG)
	286	rc = 1;
	287	else
	288	rc = 0;
	289
	290	kfree(xattr_data);
	291	return rc;
15647eb3 DK	292	}
15647eb3 DK	293
21362f43	294
66dbc325 MZ	295	/*
	296	* Calculate the hmac and update security.evm xattr
	297	*
	298	* Expects to be called with i_mutex locked.
	299	*/
	300	int evm_update_evmxattr(struct dentry dentry, const char xattr_name,
	301	const char *xattr_value, size_t xattr_value_len)
	302	{
c6f493d6	303	struct inode *inode = d_backing_inode(dentry);
6be5cc52	304	struct evm_ima_xattr_data xattr_data;
66dbc325 MZ	305	int rc = 0;
66dbc325 MZ	306
21362f43 MG	307	/*
	308	* Don't permit any transformation of the EVM xattr if the signature
	309	* is of an immutable type
	310	*/
	311	rc = evm_is_immutable(dentry, inode);
	312	if (rc < 0)
	313	return rc;
	314	if (rc)
	315	return -EPERM;
	316
66dbc325	317	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
6be5cc52 DK	318	xattr_value_len, xattr_data.digest);
	319	if (rc == 0) {
	320	xattr_data.type = EVM_XATTR_HMAC;
66dbc325	321	rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
6be5cc52 DK	322	&xattr_data,
6be5cc52 DK	323	sizeof(xattr_data), 0);
5d6c3191 AG	324	} else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) {
5d6c3191 AG	325	rc = __vfs_removexattr(dentry, XATTR_NAME_EVM);
a67adb99	326	}
66dbc325 MZ	327	return rc;
	328	}
	329
cb723180 MZ	330	int evm_init_hmac(struct inode inode, const struct xattr lsm_xattr,
	331	char *hmac_val)
	332	{
d46eb369	333	struct shash_desc *desc;
cb723180	334
15647eb3	335	desc = init_desc(EVM_XATTR_HMAC);
d46eb369	336	if (IS_ERR(desc)) {
20ee451f	337	pr_info("init_desc failed\n");
d46eb369	338	return PTR_ERR(desc);
cb723180 MZ	339	}
cb723180 MZ	340
d46eb369	341	crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
21362f43	342	hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
d46eb369	343	kfree(desc);
cb723180 MZ	344	return 0;
	345	}
	346
66dbc325 MZ	347	/*
	348	* Get the key from the TPM for the SHA1-HMAC
	349	*/
	350	int evm_init_key(void)
	351	{
	352	struct key *evm_key;
	353	struct encrypted_key_payload *ekp;
76266763	354	int rc;
66dbc325 MZ	355
	356	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
	357	if (IS_ERR(evm_key))
	358	return -ENOENT;
	359
	360	down_read(&evm_key->sem);
146aa8b1	361	ekp = evm_key->payload.data[0];
76266763 DK	362
	363	rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
	364
66dbc325 MZ	365	/* burn the original key contents */
	366	memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
	367	up_read(&evm_key->sem);
	368	key_put(evm_key);
	369	return rc;
	370	}