[PATCH 2.6.26 #repost] Smack: Integrate with Audit

[Ahmed S. Darwish]

Hi James/all,

On Thu, Apr 17, 2008 at 11:05:57AM +0000, James Morris wrote:
> 
> Please review the following security patches for 2.6.26, which have
> been undergoing testing in the "next" tree and affect multiple LSMs.
> 
> 

As a clarification, those new changes was added to the security tree 
to modularly integrate Smack with Audit. The final step is the
reposted below patch which setups the new Audit hooks for Smack.

The main concern against below patch was the reuse of SELinux Audit
fields. For such reuse, Stephen asked for an explicit ACK from the 
Audit devs. I've CCed Steve and Al as a kind request for the ACK.

Patch is re-based and re-tested over James's security/for-linus
branch.

Thanks all.

-->

Setup the new Audit hooks for Smack. SELinux Audit rule fields 
are recycled to avoid `auditd' userspace modifications.
Currently only equality testing is supported on labels acting 
as a subject (AUDIT_SUBJ_USER) or as an object (AUDIT_OBJ_USER).

Signed-off-by: Ahmed S. Darwish <darwish.07@xxxxxxxxx>
---

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 904bdc0..70e4abc 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -26,6 +26,7 @@
 #include <linux/pipe_fs_i.h>
 #include <net/netlabel.h>
 #include <net/cipso_ipv4.h>
+#include <linux/audit.h>
 
 #include "smack.h"
 
@@ -752,6 +753,18 @@ static int smack_inode_listsecurity(struct inode *inode, char *buffer,
 	return -EINVAL;
 }
 
+/**
+ * smack_inode_getsecid - Extract inode's security id
+ * @inode: inode to extract the info from
+ * @secid: where result will be saved
+ */
+static void smack_inode_getsecid(const struct inode *inode, u32 *secid)
+{
+	struct inode_smack *isp = inode->i_security;
+
+	*secid = smack_to_secid(isp->smk_inode);
+}
+
 /*
  * File Hooks
  */
@@ -1805,6 +1818,18 @@ static int smack_ipc_permission(struct kern_ipc_perm *ipp, short flag)
 	return smk_curacc(isp, may);
 }
 
+/**
+ * smack_ipc_getsecid - Extract smack security id
+ * @ipcp: the object permissions
+ * @secid: where result will be saved
+ */
+static void smack_ipc_getsecid(struct kern_ipc_perm *ipp, u32 *secid)
+{
+	char *smack = ipp->security;
+
+	*secid = smack_to_secid(smack);
+}
+
 /* module stacking operations */
 
 /**
@@ -2382,6 +2407,124 @@ static int smack_key_permission(key_ref_t key_ref,
 #endif /* CONFIG_KEYS */
 
 /*
+ * Smack Audit hooks
+ *
+ * Audit requires a unique representation of each Smack specific
+ * rule. This unique representation is used to distinguish the
+ * object to be audited from remaining kernel objects and also
+ * works as a glue between the audit hooks.
+ *
+ * Since repository entries are added but never deleted, we'll use
+ * the smack_known label address related to the given audit rule as
+ * the needed unique representation. This also better fits the smack
+ * model where nearly everything is a label.
+ */
+#ifdef CONFIG_AUDIT
+
+/**
+ * smack_audit_rule_init - Initialize a smack audit rule
+ * @field: audit rule fields given from user-space (audit.h)
+ * @op: required testing operator (=, !=, >, <, ...)
+ * @rulestr: smack label to be audited
+ * @vrule: pointer to save our own audit rule representation
+ *
+ * Prepare to audit cases where (@field @op @rulestr) is true.
+ * The label to be audited is created if necessay.
+ */
+static int smack_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
+{
+	char **rule = (char **)vrule;
+	*rule = NULL;
+
+	if (field != AUDIT_SUBJ_USER && field != AUDIT_OBJ_USER)
+		return -EINVAL;
+
+	if (op != AUDIT_EQUAL && op != AUDIT_NOT_EQUAL)
+		return -EINVAL;
+
+	*rule = smk_import(rulestr, 0);
+
+	return 0;
+}
+
+/**
+ * smack_audit_rule_known - Distinguish Smack audit rules
+ * @krule: rule of interest, in Audit kernel representation format
+ *
+ * This is used to filter Smack rules from remaining Audit ones.
+ * If it's proved that this rule belongs to us, the
+ * audit_rule_match hook will be called to do the final judgement.
+ */
+static int smack_audit_rule_known(struct audit_krule *krule)
+{
+	struct audit_field *f;
+	int i;
+
+	for (i = 0; i < krule->field_count; i++) {
+		f = &krule->fields[i];
+
+		if (f->type == AUDIT_SUBJ_USER || f->type == AUDIT_OBJ_USER)
+			return 1;
+	}
+
+	return 0;
+}
+
+/**
+ * smack_audit_rule_match - Audit given object ?
+ * @secid: security id for identifying the object to test
+ * @field: audit rule flags given from user-space
+ * @op: required testing operator
+ * @vrule: smack internal rule presentation
+ * @actx: audit context associated with the check
+ *
+ * The core Audit hook. It's used to take the decision of
+ * whether to audit or not to audit a given object.
+ */
+static int smack_audit_rule_match(u32 secid, u32 field, u32 op, void *vrule,
+				  struct audit_context *actx)
+{
+	char *smack;
+	char *rule = vrule;
+
+	if (!rule) {
+		audit_log(actx, GFP_KERNEL, AUDIT_SELINUX_ERR,
+			  "Smack: missing rule\n");
+		return -ENOENT;
+	}
+
+	if (field != AUDIT_SUBJ_USER && field != AUDIT_OBJ_USER)
+		return 0;
+
+	smack = smack_from_secid(secid);
+
+	/*
+	 * No need to do string comparisons. If a match occurs,
+	 * both pointers will point to the same smack_known
+	 * label.
+	 */
+	if (op == AUDIT_EQUAL)
+		return (rule == smack);
+	if (op == AUDIT_NOT_EQUAL)
+		return (rule != smack);
+
+	return 0;
+}
+
+/**
+ * smack_audit_rule_free - free smack rule representation
+ * @vrule: rule to be freed.
+ *
+ * No memory was allocated.
+ */
+static void smack_audit_rule_free(void *vrule)
+{
+	/* No-op */
+}
+
+#endif /* CONFIG_AUDIT */
+
+/*
  * smack_secid_to_secctx - return the smack label for a secid
  * @secid: incoming integer
  * @secdata: destination
@@ -2467,6 +2610,7 @@ struct security_operations smack_ops = {
 	.inode_getsecurity = 		smack_inode_getsecurity,
 	.inode_setsecurity = 		smack_inode_setsecurity,
 	.inode_listsecurity = 		smack_inode_listsecurity,
+	.inode_getsecid =		smack_inode_getsecid,
 
 	.file_permission = 		smack_file_permission,
 	.file_alloc_security = 		smack_file_alloc_security,
@@ -2497,6 +2641,7 @@ struct security_operations smack_ops = {
 	.task_to_inode = 		smack_task_to_inode,
 
 	.ipc_permission = 		smack_ipc_permission,
+	.ipc_getsecid =			smack_ipc_getsecid,
 
 	.msg_msg_alloc_security = 	smack_msg_msg_alloc_security,
 	.msg_msg_free_security = 	smack_msg_msg_free_security,
@@ -2541,12 +2686,22 @@ struct security_operations smack_ops = {
 	.sk_free_security = 		smack_sk_free_security,
 	.sock_graft = 			smack_sock_graft,
 	.inet_conn_request = 		smack_inet_conn_request,
+
  /* key management security hooks */
 #ifdef CONFIG_KEYS
 	.key_alloc = 			smack_key_alloc,
 	.key_free = 			smack_key_free,
 	.key_permission = 		smack_key_permission,
 #endif /* CONFIG_KEYS */
+
+ /* Audit hooks */
+#ifdef CONFIG_AUDIT
+	.audit_rule_init =		smack_audit_rule_init,
+	.audit_rule_known =		smack_audit_rule_known,
+	.audit_rule_match =		smack_audit_rule_match,
+	.audit_rule_free =		smack_audit_rule_free,
+#endif /* CONFIG_AUDIT */
+
 	.secid_to_secctx = 		smack_secid_to_secctx,
 	.secctx_to_secid = 		smack_secctx_to_secid,
 	.release_secctx = 		smack_release_secctx,

-- 

"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com

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