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Message-ID: <20190614175513.27097-2-roberto.sassu@huawei.com>
Date: Fri, 14 Jun 2019 19:55:00 +0200
From: Roberto Sassu <roberto.sassu@...wei.com>
To: <zohar@...ux.ibm.com>, <dmitry.kasatkin@...wei.com>,
<mjg59@...gle.com>
CC: <linux-integrity@...r.kernel.org>,
<linux-security-module@...r.kernel.org>,
<linux-fsdevel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <silviu.vlasceanu@...wei.com>,
Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH v4 01/14] ima: read hash algorithm from security.ima even if appraisal is not enabled
IMA reads the hash algorithm from security.ima, if exists, so that a
signature can be verified even if the algorithm used for the signature
differs from IMA algorithm.
This patch moves ima_read_xattr() and ima_get_hash_algo() to ima_main.c, to
retrieve the algorithm even if appraisal is not enabled. Knowing the
algorithm in advance would be useful also for measurement. The new Digest
Lists extension does not add a new entry to the measurement list if the
actual file digest is found in a loaded list. It might be possible that the
algorithm used for the digest lists differs from IMA algorithm.
This patch also changes the requirement that security.ima must contain a
signature, if the type is EVM_IMA_XATTR_DIGSIG. A signature with length
zero is accepted.
Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
security/integrity/ima/ima.h | 16 --------
security/integrity/ima/ima_appraise.c | 55 ++-------------------------
security/integrity/ima/ima_main.c | 51 +++++++++++++++++++++++++
3 files changed, 55 insertions(+), 67 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index ee509c68fe14..b4a0d2a02ff2 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -248,10 +248,6 @@ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func);
void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file);
enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
enum ima_hooks func);
-enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
- int xattr_len);
-int ima_read_xattr(struct dentry *dentry,
- struct evm_ima_xattr_data **xattr_value);
#else
static inline int ima_appraise_measurement(enum ima_hooks func,
@@ -282,18 +278,6 @@ static inline enum integrity_status ima_get_cache_status(struct integrity_iint_c
return INTEGRITY_UNKNOWN;
}
-static inline enum hash_algo
-ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len)
-{
- return ima_hash_algo;
-}
-
-static inline int ima_read_xattr(struct dentry *dentry,
- struct evm_ima_xattr_data **xattr_value)
-{
- return 0;
-}
-
#endif /* CONFIG_IMA_APPRAISE */
/* LSM based policy rules require audit */
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 9b3b172f9748..2566dbfd2464 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -151,57 +151,6 @@ static void ima_cache_flags(struct integrity_iint_cache *iint,
}
}
-enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
- int xattr_len)
-{
- struct signature_v2_hdr *sig;
- enum hash_algo ret;
-
- if (!xattr_value || xattr_len < 2)
- /* return default hash algo */
- return ima_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 ima_hash_algo;
- return sig->hash_algo;
- break;
- case IMA_XATTR_DIGEST_NG:
- ret = xattr_value->digest[0];
- if (ret < HASH_ALGO__LAST)
- return ret;
- 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))
- return HASH_ALGO_MD5;
- else
- return HASH_ALGO_SHA1;
- } else if (xattr_len == 17)
- return HASH_ALGO_MD5;
- break;
- }
-
- /* return default hash algo */
- return ima_hash_algo;
-}
-
-int ima_read_xattr(struct dentry *dentry,
- struct evm_ima_xattr_data **xattr_value)
-{
- ssize_t ret;
-
- ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
- 0, GFP_NOFS);
- if (ret == -EOPNOTSUPP)
- ret = 0;
- return ret;
-}
-
/*
* ima_appraise_measurement - appraise file measurement
*
@@ -226,6 +175,10 @@ int ima_appraise_measurement(enum ima_hooks func,
if (!(inode->i_opflags & IOP_XATTR))
return INTEGRITY_UNKNOWN;
+ if (xattr_len == sizeof(struct signature_v2_hdr) &&
+ xattr_value->type == EVM_IMA_XATTR_DIGSIG)
+ rc = -ENODATA;
+
if (rc <= 0) {
if (rc && rc != -ENODATA)
goto out;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 0c49cf6470a4..dc53ed8b0dd0 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -143,6 +143,57 @@ static void ima_rdwr_violation_check(struct file *file,
"invalid_pcr", "open_writers");
}
+static enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
+ int xattr_len)
+{
+ struct signature_v2_hdr *sig;
+ enum hash_algo ret;
+
+ if (!xattr_value || xattr_len < 2)
+ /* return default hash algo */
+ return ima_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 ima_hash_algo;
+ return sig->hash_algo;
+ case IMA_XATTR_DIGEST_NG:
+ ret = xattr_value->digest[0];
+ if (ret < HASH_ALGO__LAST)
+ return ret;
+ 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))
+ return HASH_ALGO_MD5;
+ else
+ return HASH_ALGO_SHA1;
+ } else if (xattr_len == 17)
+ return HASH_ALGO_MD5;
+ break;
+ }
+
+ /* return default hash algo */
+ return ima_hash_algo;
+}
+
+static int ima_read_xattr(struct dentry *dentry,
+ struct evm_ima_xattr_data **xattr_value)
+{
+ ssize_t ret;
+
+ ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
+ 0, GFP_NOFS);
+ if (ret == -EOPNOTSUPP)
+ ret = 0;
+ return ret;
+}
+
static void ima_check_last_writer(struct integrity_iint_cache *iint,
struct inode *inode, struct file *file)
{
--
2.17.1
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