[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 <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);

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) {
		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 = 0;

	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];
	if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
		rc = -EINVAL;
		goto out;
	}
	memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
out:
	/* 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>
66dbc325	21	#include <keys/encrypted-type.h>
d46eb369	22	#include <crypto/hash.h>
66dbc325 MZ	23	#include "evm.h"
	24
	25	#define EVMKEY "evm-key"
	26	#define MAX_KEY_SIZE 128
	27	static unsigned char evmkey[MAX_KEY_SIZE];
	28	static int evmkey_len = MAX_KEY_SIZE;
	29
d46eb369	30	struct crypto_shash *hmac_tfm;
15647eb3	31	struct crypto_shash *hash_tfm;
d46eb369	32
97426f98 DK	33	static DEFINE_MUTEX(mutex);
97426f98 DK	34
8fcc9954	35	static struct shash_desc *init_desc(char type)
66dbc325	36	{
143b01d3	37	long rc;
15647eb3 DK	38	char *algo;
15647eb3 DK	39	struct crypto_shash **tfm;
d46eb369 DK	40	struct shash_desc *desc;
d46eb369 DK	41
15647eb3 DK	42	if (type == EVM_XATTR_HMAC) {
	43	tfm = &hmac_tfm;
	44	algo = evm_hmac;
	45	} else {
	46	tfm = &hash_tfm;
	47	algo = evm_hash;
	48	}
	49
	50	if (*tfm == NULL) {
97426f98	51	mutex_lock(&mutex);
143b01d3	52	if (*tfm)
97426f98	53	goto out;
15647eb3 DK	54	*tfm = crypto_alloc_shash(algo, 0, CRYPTO_ALG_ASYNC);
15647eb3 DK	55	if (IS_ERR(*tfm)) {
15647eb3	56	rc = PTR_ERR(*tfm);
143b01d3	57	pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
15647eb3	58	*tfm = NULL;
97426f98	59	mutex_unlock(&mutex);
d46eb369 DK	60	return ERR_PTR(rc);
d46eb369 DK	61	}
88d7ed35 DK	62	if (type == EVM_XATTR_HMAC) {
	63	rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
	64	if (rc) {
	65	crypto_free_shash(*tfm);
	66	*tfm = NULL;
143b01d3	67	mutex_unlock(&mutex);
88d7ed35 DK	68	return ERR_PTR(rc);
88d7ed35 DK	69	}
d21b5945	70	}
97426f98 DK	71	out:
97426f98 DK	72	mutex_unlock(&mutex);
66dbc325	73	}
d46eb369	74
15647eb3	75	desc = kmalloc(sizeof(desc) + crypto_shash_descsize(tfm),
d46eb369 DK	76	GFP_KERNEL);
	77	if (!desc)
	78	return ERR_PTR(-ENOMEM);
	79
15647eb3	80	desc->tfm = *tfm;
d46eb369 DK	81	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
d46eb369 DK	82
d46eb369	83	rc = crypto_shash_init(desc);
d46eb369 DK	84	if (rc) {
	85	kfree(desc);
	86	return ERR_PTR(rc);
	87	}
	88	return desc;
66dbc325 MZ	89	}
	90
	91	/* Protect against 'cutting & pasting' security.evm xattr, include inode
	92	* specific info.
	93	*
	94	* (Additional directory/file metadata needs to be added for more complete
	95	* protection.)
	96	*/
d46eb369	97	static void hmac_add_misc(struct shash_desc desc, struct inode inode,
66dbc325 MZ	98	char *digest)
	99	{
	100	struct h_misc {
	101	unsigned long ino;
	102	__u32 generation;
	103	uid_t uid;
	104	gid_t gid;
	105	umode_t mode;
	106	} hmac_misc;
66dbc325	107
2bb930ab	108	memset(&hmac_misc, 0, sizeof(hmac_misc));
66dbc325 MZ	109	hmac_misc.ino = inode->i_ino;
66dbc325 MZ	110	hmac_misc.generation = inode->i_generation;
cf9c9352 EB	111	hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
cf9c9352 EB	112	hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
66dbc325	113	hmac_misc.mode = inode->i_mode;
2bb930ab	114	crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
d3b33679	115	if (evm_hmac_attrs & EVM_ATTR_FSUUID)
74de6684 DK	116	crypto_shash_update(desc, inode->i_sb->s_uuid,
74de6684 DK	117	sizeof(inode->i_sb->s_uuid));
d46eb369	118	crypto_shash_final(desc, digest);
66dbc325 MZ	119	}
	120
	121	/*
	122	* Calculate the HMAC value across the set of protected security xattrs.
	123	*
	124	* Instead of retrieving the requested xattr, for performance, calculate
	125	* the hmac using the requested xattr value. Don't alloc/free memory for
	126	* each xattr, but attempt to re-use the previously allocated memory.
	127	*/
15647eb3 DK	128	static int evm_calc_hmac_or_hash(struct dentry *dentry,
	129	const char *req_xattr_name,
	130	const char *req_xattr_value,
	131	size_t req_xattr_value_len,
	132	char type, char *digest)
66dbc325	133	{
c6f493d6	134	struct inode *inode = d_backing_inode(dentry);
d46eb369	135	struct shash_desc *desc;
66dbc325 MZ	136	char **xattrname;
	137	size_t xattr_size = 0;
	138	char *xattr_value = NULL;
	139	int error;
	140	int size;
	141
627bf81a	142	if (!inode->i_op->getxattr)
66dbc325	143	return -EOPNOTSUPP;
15647eb3	144	desc = init_desc(type);
d46eb369 DK	145	if (IS_ERR(desc))
d46eb369 DK	146	return PTR_ERR(desc);
66dbc325 MZ	147
	148	error = -ENODATA;
	149	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
	150	if ((req_xattr_name && req_xattr_value)
	151	&& !strcmp(*xattrname, req_xattr_name)) {
	152	error = 0;
d46eb369 DK	153	crypto_shash_update(desc, (const u8 *)req_xattr_value,
d46eb369 DK	154	req_xattr_value_len);
66dbc325 MZ	155	continue;
	156	}
	157	size = vfs_getxattr_alloc(dentry, *xattrname,
	158	&xattr_value, xattr_size, GFP_NOFS);
	159	if (size == -ENOMEM) {
	160	error = -ENOMEM;
	161	goto out;
	162	}
	163	if (size < 0)
	164	continue;
	165
	166	error = 0;
	167	xattr_size = size;
d46eb369	168	crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
66dbc325	169	}
d46eb369 DK	170	hmac_add_misc(desc, inode, digest);
d46eb369 DK	171
66dbc325	172	out:
d46eb369 DK	173	kfree(xattr_value);
d46eb369 DK	174	kfree(desc);
66dbc325 MZ	175	return error;
	176	}
	177
15647eb3 DK	178	int evm_calc_hmac(struct dentry dentry, const char req_xattr_name,
	179	const char *req_xattr_value, size_t req_xattr_value_len,
	180	char *digest)
	181	{
	182	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
	183	req_xattr_value_len, EVM_XATTR_HMAC, digest);
	184	}
	185
	186	int evm_calc_hash(struct dentry dentry, const char req_xattr_name,
	187	const char *req_xattr_value, size_t req_xattr_value_len,
	188	char *digest)
	189	{
	190	return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
	191	req_xattr_value_len, IMA_XATTR_DIGEST, digest);
	192	}
	193
66dbc325 MZ	194	/*
	195	* Calculate the hmac and update security.evm xattr
	196	*
	197	* Expects to be called with i_mutex locked.
	198	*/
	199	int evm_update_evmxattr(struct dentry dentry, const char xattr_name,
	200	const char *xattr_value, size_t xattr_value_len)
	201	{
c6f493d6	202	struct inode *inode = d_backing_inode(dentry);
6be5cc52	203	struct evm_ima_xattr_data xattr_data;
66dbc325 MZ	204	int rc = 0;
	205
	206	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
6be5cc52 DK	207	xattr_value_len, xattr_data.digest);
	208	if (rc == 0) {
	209	xattr_data.type = EVM_XATTR_HMAC;
66dbc325	210	rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
6be5cc52 DK	211	&xattr_data,
6be5cc52 DK	212	sizeof(xattr_data), 0);
a67adb99	213	} else if (rc == -ENODATA && inode->i_op->removexattr) {
66dbc325	214	rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
a67adb99	215	}
66dbc325 MZ	216	return rc;
	217	}
	218
cb723180 MZ	219	int evm_init_hmac(struct inode inode, const struct xattr lsm_xattr,
	220	char *hmac_val)
	221	{
d46eb369	222	struct shash_desc *desc;
cb723180	223
15647eb3	224	desc = init_desc(EVM_XATTR_HMAC);
d46eb369	225	if (IS_ERR(desc)) {
20ee451f	226	pr_info("init_desc failed\n");
d46eb369	227	return PTR_ERR(desc);
cb723180 MZ	228	}
cb723180 MZ	229
d46eb369 DK	230	crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
	231	hmac_add_misc(desc, inode, hmac_val);
	232	kfree(desc);
cb723180 MZ	233	return 0;
	234	}
	235
66dbc325 MZ	236	/*
	237	* Get the key from the TPM for the SHA1-HMAC
	238	*/
	239	int evm_init_key(void)
	240	{
	241	struct key *evm_key;
	242	struct encrypted_key_payload *ekp;
	243	int rc = 0;
	244
	245	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
	246	if (IS_ERR(evm_key))
	247	return -ENOENT;
	248
	249	down_read(&evm_key->sem);
146aa8b1	250	ekp = evm_key->payload.data[0];
66dbc325 MZ	251	if (ekp->decrypted_datalen > MAX_KEY_SIZE) {
	252	rc = -EINVAL;
	253	goto out;
	254	}
	255	memcpy(evmkey, ekp->decrypted_data, ekp->decrypted_datalen);
	256	out:
	257	/* burn the original key contents */
	258	memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);
	259	up_read(&evm_key->sem);
	260	key_put(evm_key);
	261	return rc;
	262	}