Release 4.7 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;
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
dmitry kasatkin
dmitry kasatkin
88
100.00%
1
100.00%
Total
88
100.00%
1
100.00%


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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
dmitry kasatkin
dmitry kasatkin
227
78.82%
7
87.50%
mimi zohar
mimi zohar
61
21.18%
1
12.50%
Total
288
100.00%
8
100.00%

/* 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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
mimi zohar
mimi zohar
107
67.72%
1
16.67%
dmitry kasatkin
dmitry kasatkin
39
24.68%
4
66.67%
eric w. biederman
eric w. biederman
12
7.59%
1
16.67%
Total
158
100.00%
6
100.00%

/*
 * 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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
mimi zohar
mimi zohar
208
84.21%
1
25.00%
dmitry kasatkin
dmitry kasatkin
36
14.57%
2
50.00%
david howells
david howells
3
1.21%
1
25.00%
Total
247
100.00%
4
100.00%



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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
dmitry kasatkin
dmitry kasatkin
43
100.00%
1
100.00%
Total
43
100.00%
1
100.00%



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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
dmitry kasatkin
dmitry kasatkin
43
100.00%
1
100.00%
Total
43
100.00%
1
100.00%

/*
 * 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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
mimi zohar
mimi zohar
93
75.00%
1
25.00%
dmitry kasatkin
dmitry kasatkin
28
22.58%
2
50.00%
david howells
david howells
3
2.42%
1
25.00%
Total
124
100.00%
4
100.00%



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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
mimi zohar
mimi zohar
64
78.05%
1
25.00%
dmitry kasatkin
dmitry kasatkin
17
20.73%
2
50.00%
joe perches
joe perches
1
1.22%
1
25.00%
Total
82
100.00%
4
100.00%

/*
 * 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;
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
mimi zohar
mimi zohar
101
96.19%
1
33.33%
david howells
david howells
3
2.86%
1
33.33%
dmitry kasatkin
dmitry kasatkin
1
0.95%
1
33.33%
Total
105
100.00%
3
100.00%

Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
mimi zohar
mimi zohar
677
53.56%
2
10.53%
dmitry kasatkin
dmitry kasatkin
558
44.15%
13
68.42%
eric w. biederman
eric w. biederman
12
0.95%
1
5.26%
david howells
david howells
9
0.71%
2
10.53%
joe perches
joe perches
8
0.63%
1
5.26%
Total
1264
100.00%
19
100.00%
  
Directory: security/integrity/evm

Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.