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Subject[RFC][PATCH -v2] Smack: Integrate with Audit
From
Hi!,

Setup the new Audit hooks for Smack. The AUDIT_SUBJ_USER and
AUDIT_OBJ_USER SELinux flags are recycled to avoid `auditd'
userspace modifications. Smack only needs auditing on
a subject/object bases, so those flags were enough.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
---
smack_lsm.c | 153 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 153 insertions(+)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index afa7967..d471839 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"

@@ -759,6 +760,17 @@ 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
*/
@@ -1814,6 +1826,17 @@ static int smack_ipc_permission(struct kern_ipc_perm *ipp, short flag)
return smk_curacc(isp, may);
}

+/**
+ * smack_ipc_getsecid - Extract ipc object security id
+ * @ipp: 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 */

/**
@@ -2391,6 +2414,124 @@ 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 since we're sure
+ * that if a match occurs, both pointers will point
+ * to the same smack_konwn 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
@@ -2476,6 +2617,7 @@ 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,
@@ -2506,6 +2648,7 @@ 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,
@@ -2550,12 +2693,22 @@ 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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