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ima: provide hash algo info in the xattr

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All files labeled with 'security.ima' hashes, are hashed using the
same hash algorithm.  Changing from one hash algorithm to another,
requires relabeling the filesystem.  This patch defines a new xattr
type, which includes the hash algorithm, permitting different files
to be hashed with different algorithms.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
This commit is contained in:
Dmitry Kasatkin 2013-08-12 11:22:51 +03:00 committed by Mimi Zohar
parent e7a2ad7eb6
commit 3ea7a56067
2 changed files with 59 additions and 15 deletions
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61
security/integrity/ima/ima_appraise.c
View File

@ -15,6 +15,7 @@
#include <linux/magic.h>
#include <linux/ima.h>
#include <linux/evm.h>
#include <crypto/hash_info.h>
#include "ima.h"
@ -45,10 +46,22 @@ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
static int ima_fix_xattr(struct dentry *dentry,
struct integrity_iint_cache *iint)
{
iint->ima_hash->type = IMA_XATTR_DIGEST;
return __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
&iint->ima_hash->type,
1 + iint->ima_hash->length, 0);
int rc, offset;
u8 algo = iint->ima_hash->algo;
if (algo <= HASH_ALGO_SHA1) {
offset = 1;
iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
} else {
offset = 0;
iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
iint->ima_hash->xattr.ng.algo = algo;
}
rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
&iint->ima_hash->xattr.data[offset],
(sizeof(iint->ima_hash->xattr) - offset) +
iint->ima_hash->length, 0);
return rc;
}
/* Return specific func appraised cached result */
@ -112,15 +125,31 @@ void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
{
struct signature_v2_hdr *sig;
if (!xattr_value || xattr_len < 0 || xattr_len <= 1 + sizeof(*sig))
if (!xattr_value || xattr_len < 2)
return;
sig = (typeof(sig)) xattr_value->digest;
if (xattr_value->type != EVM_IMA_XATTR_DIGSIG || sig->version != 2)
return;
hash->algo = sig->hash_algo;
switch (xattr_value->type) {
case EVM_IMA_XATTR_DIGSIG:
sig = (typeof(sig))xattr_value;
if (sig->version != 2 || xattr_len <= sizeof(*sig))
return;
hash->algo = sig->hash_algo;
break;
case IMA_XATTR_DIGEST_NG:
hash->algo = xattr_value->digest[0];
break;
case IMA_XATTR_DIGEST:
/* this is for backward compatibility */
if (xattr_len == 21) {
unsigned int zero = 0;
if (!memcmp(&xattr_value->digest[16], &zero, 4))
hash->algo = HASH_ALGO_MD5;
else
hash->algo = HASH_ALGO_SHA1;
} else if (xattr_len == 17)
hash->algo = HASH_ALGO_MD5;
break;
}
}
int ima_read_xattr(struct dentry *dentry,
@ -153,7 +182,7 @@ int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
enum integrity_status status = INTEGRITY_UNKNOWN;
const char *op = "appraise_data";
char *cause = "unknown";
int rc = xattr_len;
int rc = xattr_len, hash_start = 0;
if (!ima_appraise)
return 0;
@ -180,17 +209,21 @@ int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
goto out;
}
switch (xattr_value->type) {
case IMA_XATTR_DIGEST_NG:
/* first byte contains algorithm id */
hash_start = 1;
case IMA_XATTR_DIGEST:
if (iint->flags & IMA_DIGSIG_REQUIRED) {
cause = "IMA signature required";
status = INTEGRITY_FAIL;
break;
}
if (xattr_len - 1 >= iint->ima_hash->length)
if (xattr_len - sizeof(xattr_value->type) - hash_start >=
iint->ima_hash->length)
/* xattr length may be longer. md5 hash in previous
version occupied 20 bytes in xattr, instead of 16
*/
rc = memcmp(xattr_value->digest,
rc = memcmp(&xattr_value->digest[hash_start],
iint->ima_hash->digest,
iint->ima_hash->length);
else

13
security/integrity/integrity.h
View File

@ -54,6 +54,7 @@ enum evm_ima_xattr_type {
IMA_XATTR_DIGEST = 0x01,
EVM_XATTR_HMAC,
EVM_IMA_XATTR_DIGSIG,
IMA_XATTR_DIGEST_NG,
};
struct evm_ima_xattr_data {
@ -66,7 +67,17 @@ struct evm_ima_xattr_data {
struct ima_digest_data {
u8 algo;
u8 length;
u8 type;
union {
struct {
u8 unused;
u8 type;
} sha1;
struct {
u8 type;
u8 algo;
} ng;
u8 data[2];
} xattr;
u8 digest[0];
} __packed;