[deliverable/linux.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("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);
		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 *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));
	hmac_misc.ino = inode->i_ino;
	hmac_misc.generation = inode->i_generation;
	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)
		crypto_shash_update(desc, inode->i_sb->s_uuid,
				    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;

	if (!inode->i_op->getxattr)
		return -EOPNOTSUPP;
	desc = init_desc(type);
	if (IS_ERR(desc))
		return PTR_ERR(desc);

	error = -ENODATA;
	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
		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);
			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);
	}
	hmac_add_misc(desc, inode, digest);

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 *digest)
{
	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
				req_xattr_value_len, IMA_XATTR_DIGEST, digest);
}

/*
 * 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;

	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_op->removexattr) {
		rc = inode->i_op->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, 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 DK	82	if (!(evm_initialized & EVM_INIT_HMAC)) {
	83	pr_err("HMAC key is not set\n");
	84	return ERR_PTR(-ENOKEY);
	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;
15647eb3 DK	97	*tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
15647eb3 DK	98	if (IS_ERR(*tfm)) {
15647eb3	99	rc = PTR_ERR(*tfm);
143b01d3	100	pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
15647eb3	101	*tfm = NULL;
97426f98	102	mutex_unlock(&mutex);
d46eb369 DK	103	return ERR_PTR(rc);
d46eb369 DK	104	}
88d7ed35 DK	105	if (type == EVM_XATTR_HMAC) {
	106	rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
	107	if (rc) {
	108	crypto_free_shash(*tfm);
	109	*tfm = NULL;
143b01d3	110	mutex_unlock(&mutex);
88d7ed35 DK	111	return ERR_PTR(rc);
88d7ed35 DK	112	}
d21b5945	113	}
97426f98 DK	114	out:
97426f98 DK	115	mutex_unlock(&mutex);
66dbc325	116	}
d46eb369	117
15647eb3	118	desc = kmalloc(sizeof(desc) + crypto_shash_descsize(tfm),
d46eb369 DK	119	GFP_KERNEL);
	120	if (!desc)
	121	return ERR_PTR(-ENOMEM);
	122
15647eb3	123	desc->tfm = *tfm;
d46eb369 DK	124	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
d46eb369 DK	125
d46eb369	126	rc = crypto_shash_init(desc);
d46eb369 DK	127	if (rc) {
	128	kfree(desc);
	129	return ERR_PTR(rc);
	130	}
	131	return desc;
66dbc325 MZ	132	}
	133
	134	/* Protect against 'cutting & pasting' security.evm xattr, include inode
	135	* specific info.
	136	*
	137	* (Additional directory/file metadata needs to be added for more complete
	138	* protection.)
	139	*/
d46eb369	140	static void hmac_add_misc(struct shash_desc desc, struct inode inode,
66dbc325 MZ	141	char *digest)
	142	{
	143	struct h_misc {
	144	unsigned long ino;
	145	__u32 generation;
	146	uid_t uid;
	147	gid_t gid;
	148	umode_t mode;
	149	} hmac_misc;
66dbc325	150
2bb930ab	151	memset(&hmac_misc, 0, sizeof(hmac_misc));
66dbc325 MZ	152	hmac_misc.ino = inode->i_ino;
66dbc325 MZ	153	hmac_misc.generation = inode->i_generation;
cf9c9352 EB	154	hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
cf9c9352 EB	155	hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
66dbc325	156	hmac_misc.mode = inode->i_mode;
2bb930ab	157	crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
d3b33679	158	if (evm_hmac_attrs & EVM_ATTR_FSUUID)
74de6684 DK	159	crypto_shash_update(desc, inode->i_sb->s_uuid,
74de6684 DK	160	sizeof(inode->i_sb->s_uuid));
d46eb369	161	crypto_shash_final(desc, digest);
66dbc325 MZ	162	}
	163
	164	/*
	165	* Calculate the HMAC value across the set of protected security xattrs.
	166	*
	167	* Instead of retrieving the requested xattr, for performance, calculate
	168	* the hmac using the requested xattr value. Don't alloc/free memory for
	169	* each xattr, but attempt to re-use the previously allocated memory.
	170	*/
15647eb3 DK	171	static int evm_calc_hmac_or_hash(struct dentry *dentry,
	172	const char *req_xattr_name,
	173	const char *req_xattr_value,
	174	size_t req_xattr_value_len,
	175	char type, char *digest)
66dbc325	176	{
c6f493d6	177	struct inode *inode = d_backing_inode(dentry);
d46eb369	178	struct shash_desc *desc;
66dbc325 MZ	179	char **xattrname;
	180	size_t xattr_size = 0;
	181	char *xattr_value = NULL;
	182	int error;
	183	int size;
	184
627bf81a	185	if (!inode->i_op->getxattr)
66dbc325	186	return -EOPNOTSUPP;
15647eb3	187	desc = init_desc(type);
d46eb369 DK	188	if (IS_ERR(desc))
d46eb369 DK	189	return PTR_ERR(desc);
66dbc325 MZ	190
	191	error = -ENODATA;
	192	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
	193	if ((req_xattr_name && req_xattr_value)
	194	&& !strcmp(*xattrname, req_xattr_name)) {
	195	error = 0;
d46eb369 DK	196	crypto_shash_update(desc, (const u8 *)req_xattr_value,
d46eb369 DK	197	req_xattr_value_len);
66dbc325 MZ	198	continue;
	199	}
	200	size = vfs_getxattr_alloc(dentry, *xattrname,
	201	&xattr_value, xattr_size, GFP_NOFS);
	202	if (size == -ENOMEM) {
	203	error = -ENOMEM;
	204	goto out;
	205	}
	206	if (size < 0)
	207	continue;
	208
	209	error = 0;
	210	xattr_size = size;
d46eb369	211	crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
66dbc325	212	}
d46eb369 DK	213	hmac_add_misc(desc, inode, digest);
d46eb369 DK	214
66dbc325	215	out:
d46eb369 DK	216	kfree(xattr_value);
d46eb369 DK	217	kfree(desc);
66dbc325 MZ	218	return error;
	219	}
	220
15647eb3 DK	221	int evm_calc_hmac(struct dentry dentry, const char req_xattr_name,
	222	const char *req_xattr_value, size_t req_xattr_value_len,
	223	char *digest)
	224	{
	225	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
	226	req_xattr_value_len, EVM_XATTR_HMAC, digest);
	227	}
	228
	229	int evm_calc_hash(struct dentry dentry, const char req_xattr_name,
	230	const char *req_xattr_value, size_t req_xattr_value_len,
	231	char *digest)
	232	{
	233	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
	234	req_xattr_value_len, IMA_XATTR_DIGEST, digest);
	235	}
	236
66dbc325 MZ	237	/*
	238	* Calculate the hmac and update security.evm xattr
	239	*
	240	* Expects to be called with i_mutex locked.
	241	*/
	242	int evm_update_evmxattr(struct dentry dentry, const char xattr_name,
	243	const char *xattr_value, size_t xattr_value_len)
	244	{
c6f493d6	245	struct inode *inode = d_backing_inode(dentry);
6be5cc52	246	struct evm_ima_xattr_data xattr_data;
66dbc325 MZ	247	int rc = 0;
	248
	249	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
6be5cc52 DK	250	xattr_value_len, xattr_data.digest);
	251	if (rc == 0) {
	252	xattr_data.type = EVM_XATTR_HMAC;
66dbc325	253	rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
6be5cc52 DK	254	&xattr_data,
6be5cc52 DK	255	sizeof(xattr_data), 0);
a67adb99	256	} else if (rc == -ENODATA && inode->i_op->removexattr) {
66dbc325	257	rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
a67adb99	258	}
66dbc325 MZ	259	return rc;
	260	}
	261
cb723180 MZ	262	int evm_init_hmac(struct inode inode, const struct xattr lsm_xattr,
	263	char *hmac_val)
	264	{
d46eb369	265	struct shash_desc *desc;
cb723180	266
15647eb3	267	desc = init_desc(EVM_XATTR_HMAC);
d46eb369	268	if (IS_ERR(desc)) {
20ee451f	269	pr_info("init_desc failed\n");
d46eb369	270	return PTR_ERR(desc);
cb723180 MZ	271	}
cb723180 MZ	272
d46eb369 DK	273	crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
	274	hmac_add_misc(desc, inode, hmac_val);
	275	kfree(desc);
cb723180 MZ	276	return 0;
	277	}
	278
66dbc325 MZ	279	/*
	280	* Get the key from the TPM for the SHA1-HMAC
	281	*/
	282	int evm_init_key(void)
	283	{
	284	struct key *evm_key;
	285	struct encrypted_key_payload *ekp;
76266763	286	int rc;
66dbc325 MZ	287
	288	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
	289	if (IS_ERR(evm_key))
	290	return -ENOENT;
	291
	292	down_read(&evm_key->sem);
146aa8b1	293	ekp = evm_key->payload.data[0];
76266763 DK	294
	295	rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen);
	296
66dbc325 MZ	297	/* burn the original key contents */
	298	memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
	299	up_read(&evm_key->sem);
	300	key_put(evm_key);
	301	return rc;
	302	}