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Date: Mon, 21 Oct 2013 18:43:08 -0400
From: Mimi Zohar <zohar@...ux.vnet.ibm.com>
To: linux-security-module@...r.kernel.org
Cc: Dmitry Kasatkin <d.kasatkin@...sung.com>,
linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>,
David Howells <dhowells@...hat.com>,
Mimi Zohar <zohar@...ux.vnet.ibm.com>
Subject: [PATCH v2 23/23] ima: provide hash algo info in the xattr
From: Dmitry Kasatkin <d.kasatkin@...sung.com>
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@...sung.com>
Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
---
security/integrity/ima/ima_appraise.c | 61 +++++++++++++++++++++++++++--------
security/integrity/integrity.h | 13 +++++++-
2 files changed, 59 insertions(+), 15 deletions(-)
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 116630c..734e946 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -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
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 5429ca5..2fb5e53 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -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;
--
1.8.1.4
--
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