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Message-Id: <1493218936-18522-2-git-send-email-sbuisson@ddn.com>
Date: Thu, 27 Apr 2017 00:02:15 +0900
From: Sebastien Buisson <sbuisson.ddn@...il.com>
To: linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, selinux@...ho.nsa.gov
Cc: serge@...lyn.com, james.l.morris@...cle.com, eparis@...isplace.org,
sds@...ho.nsa.gov, paul@...l-moore.com, danielj@...lanox.com,
Sebastien Buisson <sbuisson@....com>
Subject: [PATCH 2/3] selinux: add checksum to policydb
Add policycksum field to struct policydb. It holds the sha256
checksum computed on the binary policy every time the notifier is
called after a policy change.
Add security_policy_cksum hook to give access to policy checksum to
the rest of the kernel. Lustre client makes use of this information.
Signed-off-by: Sebastien Buisson <sbuisson@....com>
---
include/linux/lsm_hooks.h | 2 +
include/linux/security.h | 7 +++
security/security.c | 6 +++
security/selinux/hooks.c | 12 ++++-
security/selinux/include/security.h | 2 +
security/selinux/ss/policydb.h | 4 ++
security/selinux/ss/services.c | 91 +++++++++++++++++++++++++++++++++++++
7 files changed, 123 insertions(+), 1 deletion(-)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 080f34e..7aada73 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1568,6 +1568,7 @@
int (*inode_setsecctx)(struct dentry *dentry, void *ctx, u32 ctxlen);
int (*inode_getsecctx)(struct inode *inode, void **ctx, u32 *ctxlen);
+ ssize_t (*policy_cksum)(char *cksum, size_t len);
#ifdef CONFIG_SECURITY_NETWORK
int (*unix_stream_connect)(struct sock *sock, struct sock *other,
struct sock *newsk);
@@ -1813,6 +1814,7 @@ struct security_hook_heads {
struct list_head inode_notifysecctx;
struct list_head inode_setsecctx;
struct list_head inode_getsecctx;
+ struct list_head policy_cksum;
#ifdef CONFIG_SECURITY_NETWORK
struct list_head unix_stream_connect;
struct list_head unix_may_send;
diff --git a/include/linux/security.h b/include/linux/security.h
index 73a9c93..8461d31 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -385,6 +385,8 @@ int security_sem_semop(struct sem_array *sma, struct sembuf *sops,
int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
+
+ssize_t security_policy_cksum(char *cksum, size_t len);
#else /* CONFIG_SECURITY */
struct security_mnt_opts {
};
@@ -1189,6 +1191,11 @@ static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32
{
return -EOPNOTSUPP;
}
+
+static inline ssize_t security_policy_cksum(char *cksum, size_t len)
+{
+ return -EOPNOTSUPP;
+}
#endif /* CONFIG_SECURITY */
#ifdef CONFIG_SECURITY_NETWORK
diff --git a/security/security.c b/security/security.c
index ef9d9e1..a82c08c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1305,6 +1305,12 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
}
EXPORT_SYMBOL(security_inode_getsecctx);
+ssize_t security_policy_cksum(char *cksum, size_t len)
+{
+ return call_int_hook(policy_cksum, -EOPNOTSUPP, cksum, len);
+}
+EXPORT_SYMBOL(security_policy_cksum);
+
#ifdef CONFIG_SECURITY_NETWORK
int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index a4d36f8..3759198 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -173,8 +173,11 @@ static int selinux_netcache_avc_callback(u32 event)
static int selinux_lsm_notifier_avc_callback(u32 event)
{
- if (event == AVC_CALLBACK_RESET)
+ if (event == AVC_CALLBACK_RESET) {
+ if (security_policydb_compute_cksum() != 0)
+ printk(KERN_ERR "Failed to compute policydb cksum\n");
call_lsm_notifier(LSM_POLICY_CHANGE, NULL);
+ }
return 0;
}
@@ -6071,6 +6074,11 @@ static int selinux_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
*ctxlen = len;
return 0;
}
+
+static ssize_t selinux_policy_cksum(char *cksum, size_t len)
+{
+ return security_policydb_cksum(cksum, len);
+}
#ifdef CONFIG_KEYS
static int selinux_key_alloc(struct key *k, const struct cred *cred,
@@ -6285,6 +6293,8 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
LSM_HOOK_INIT(inode_setsecctx, selinux_inode_setsecctx),
LSM_HOOK_INIT(inode_getsecctx, selinux_inode_getsecctx),
+ LSM_HOOK_INIT(policy_cksum, selinux_policy_cksum),
+
LSM_HOOK_INIT(unix_stream_connect, selinux_socket_unix_stream_connect),
LSM_HOOK_INIT(unix_may_send, selinux_socket_unix_may_send),
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index f979c35..a329571 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -97,6 +97,8 @@ enum {
int security_load_policy(void *data, size_t len);
int security_read_policy(void **data, size_t *len);
size_t security_policydb_len(void);
+ssize_t security_policydb_cksum(char *cksum, size_t len);
+int security_policydb_compute_cksum(void);
int security_policycap_supported(unsigned int req_cap);
diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index 725d594..dc29492 100644
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -25,6 +25,7 @@
#define _SS_POLICYDB_H_
#include <linux/flex_array.h>
+#include <crypto/sha.h>
#include "symtab.h"
#include "avtab.h"
@@ -293,6 +294,9 @@ struct policydb {
size_t len;
unsigned int policyvers;
+ /* checksum computed on the policy */
+ unsigned char policycksum[SHA256_DIGEST_SIZE*2 + 1];
+ size_t policycksum_len;
unsigned int reject_unknown : 1;
unsigned int allow_unknown : 1;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 60d9b02..a35d294 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -53,6 +53,8 @@
#include <linux/flex_array.h>
#include <linux/vmalloc.h>
#include <net/netlabel.h>
+#include <crypto/hash.h>
+#include <crypto/sha.h>
#include "flask.h"
#include "avc.h"
@@ -2170,6 +2172,95 @@ size_t security_policydb_len(void)
}
/**
+ * security_policydb_cksum - Get policydb checksum.
+ * @cksum: string to store checksum to
+ * @len: length of checksum
+ */
+ssize_t security_policydb_cksum(char *cksum, size_t len)
+{
+ int rc;
+
+ read_lock(&policy_rwlock);
+ if (strlcpy(cksum, policydb.policycksum, len) >= len)
+ rc = -ENAMETOOLONG;
+ rc = policydb.policycksum_len;
+ read_unlock(&policy_rwlock);
+
+ return rc;
+}
+
+/**
+ * security_policydb_compute_cksum - Compute checksum of a policy database.
+ */
+int security_policydb_compute_cksum(void)
+{
+ struct crypto_ahash *tfm;
+ struct ahash_request *req;
+ struct scatterlist sl;
+ char hashval[SHA256_DIGEST_SIZE];
+ int idx;
+ unsigned char *p;
+ size_t len;
+ void *data;
+ int rc;
+
+ rc = security_read_policy(&data, &len);
+ if (rc) {
+ printk(KERN_ERR "Failed to read security policy\n");
+ return rc;
+ }
+
+ tfm = crypto_alloc_ahash("sha256", 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(tfm)) {
+ printk(KERN_ERR "Failed to alloc crypto hash sha256\n");
+ vfree(data);
+ rc = PTR_ERR(tfm);
+ return rc;
+ }
+
+ req = ahash_request_alloc(tfm, GFP_KERNEL);
+ if (!req) {
+ printk(KERN_ERR "Failed to alloc ahash_request for sha256\n");
+ crypto_free_ahash(tfm);
+ vfree(data);
+ rc = -ENOMEM;
+ return rc;
+ }
+
+ ahash_request_set_callback(req, 0, NULL, NULL);
+
+ rc = crypto_ahash_init(req);
+ if (rc) {
+ printk(KERN_ERR "Failed to init ahash\n");
+ ahash_request_free(req);
+ crypto_free_ahash(tfm);
+ vfree(data);
+ return rc;
+ }
+
+ sg_init_one(&sl, (void *)data, len);
+ ahash_request_set_crypt(req, &sl, hashval, sl.length);
+ rc = crypto_ahash_digest(req);
+
+ crypto_free_ahash(tfm);
+ ahash_request_free(req);
+ vfree(data);
+ if (rc) {
+ printk(KERN_ERR "Failed to compute digest\n");
+ return rc;
+ }
+
+ p = policydb.policycksum;
+ for (idx = 0; idx < SHA256_DIGEST_SIZE; idx++) {
+ snprintf(p, 3, "%02x", (unsigned char)(hashval[idx]));
+ p += 2;
+ }
+ policydb.policycksum_len = (size_t)(p - policydb.policycksum);
+
+ return 0;
+}
+
+/**
* security_port_sid - Obtain the SID for a port.
* @protocol: protocol number
* @port: port number
--
1.8.3.1
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