lsm: add lsmprop_to_secctx hook

Add a new hook security_lsmprop_to_secctx() and its LSM specific
implementations. The LSM specific code will use the lsm_prop element
allocated for that module. This allows for the possibility that more
than one module may be called upon to translate a secid to a string,
as can occur in the audit code.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: subject line tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: cschaufler

include/linux/lsm_hook_defs.h

@@ -294,6 +294,8 @@ LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size)
 LSM_HOOK(int, 0, ismaclabel, const char *name)
 LSM_HOOK(int, -EOPNOTSUPP, secid_to_secctx, u32 secid, char **secdata,
 	 u32 *seclen)
+LSM_HOOK(int, -EOPNOTSUPP, lsmprop_to_secctx, struct lsm_prop *prop,
+	 char **secdata, u32 *seclen)
 LSM_HOOK(int, 0, secctx_to_secid, const char *secdata, u32 seclen, u32 *secid)
 LSM_HOOK(void, LSM_RET_VOID, release_secctx, char *secdata, u32 seclen)
 LSM_HOOK(void, LSM_RET_VOID, inode_invalidate_secctx, struct inode *inode)

include/linux/security.h

@@ -535,6 +535,7 @@ int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
 int security_netlink_send(struct sock *sk, struct sk_buff *skb);
 int security_ismaclabel(const char *name);
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
+int security_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata, u32 *seclen);
 int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
 void security_release_secctx(char *secdata, u32 seclen);
 void security_inode_invalidate_secctx(struct inode *inode);
@@ -1488,7 +1489,14 @@ static inline int security_ismaclabel(const char *name)
 	return 0;
 }
 
-static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
+static inline int security_secid_to_secctx(u32 secid, char **secdata,
+					   u32 *seclen)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int security_lsmprop_to_secctx(struct lsm_prop *prop,
+					     char **secdata, u32 *seclen)
 {
 	return -EOPNOTSUPP;
 }

security/apparmor/include/secid.h

@@ -26,6 +26,8 @@ extern int apparmor_display_secid_mode;
 
 struct aa_label *aa_secid_to_label(u32 secid);
 int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
+int apparmor_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata,
+			       u32 *seclen);
 int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
 void apparmor_release_secctx(char *secdata, u32 seclen);
 

security/apparmor/lsm.c

@@ -1517,6 +1517,7 @@ static struct security_hook_list apparmor_hooks[] __ro_after_init = {
 #endif
 
 	LSM_HOOK_INIT(secid_to_secctx, apparmor_secid_to_secctx),
+	LSM_HOOK_INIT(lsmprop_to_secctx, apparmor_lsmprop_to_secctx),
 	LSM_HOOK_INIT(secctx_to_secid, apparmor_secctx_to_secid),
 	LSM_HOOK_INIT(release_secctx, apparmor_release_secctx),
 

security/apparmor/secid.c

@@ -61,10 +61,10 @@ struct aa_label *aa_secid_to_label(u32 secid)
 	return xa_load(&aa_secids, secid);
 }
 
-int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
+static int apparmor_label_to_secctx(struct aa_label *label, char **secdata,
+				    u32 *seclen)
 {
 	/* TODO: cache secctx and ref count so we don't have to recreate */
-	struct aa_label *label = aa_secid_to_label(secid);
 	int flags = FLAG_VIEW_SUBNS | FLAG_HIDDEN_UNCONFINED | FLAG_ABS_ROOT;
 	int len;
 
@@ -90,6 +90,27 @@ int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 	return 0;
 }
 
+int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
+{
+	struct aa_label *label = aa_secid_to_label(secid);
+
+	return apparmor_label_to_secctx(label, secdata, seclen);
+}
+
+int apparmor_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata,
+			       u32 *seclen)
+{
+	struct aa_label *label;
+
+	/* scaffolding */
+	if (!prop->apparmor.label && prop->scaffold.secid)
+		label = aa_secid_to_label(prop->scaffold.secid);
+	else
+		label = prop->apparmor.label;
+
+	return apparmor_label_to_secctx(label, secdata, seclen);
+}
+
 int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid)
 {
 	struct aa_label *label;

security/security.c

@@ -4311,6 +4311,27 @@ int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 }
 EXPORT_SYMBOL(security_secid_to_secctx);
 
+/**
+ * security_lsmprop_to_secctx() - Convert a lsm_prop to a secctx
+ * @prop: lsm specific information
+ * @secdata: secctx
+ * @seclen: secctx length
+ *
+ * Convert a @prop entry to security context.  If @secdata is NULL the
+ * length of the result will be returned in @seclen, but no @secdata
+ * will be returned.  This does mean that the length could change between
+ * calls to check the length and the next call which actually allocates
+ * and returns the @secdata.
+ *
+ * Return: Return 0 on success, error on failure.
+ */
+int security_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata,
+			       u32 *seclen)
+{
+	return call_int_hook(lsmprop_to_secctx, prop, secdata, seclen);
+}
+EXPORT_SYMBOL(security_lsmprop_to_secctx);
+
 /**
  * security_secctx_to_secid() - Convert a secctx to a secid
  * @secdata: secctx

security/selinux/hooks.c

@@ -6601,8 +6601,19 @@ static int selinux_ismaclabel(const char *name)
 
 static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
-	return security_sid_to_context(secid,
-				       secdata, seclen);
+	return security_sid_to_context(secid, secdata, seclen);
+}
+
+static int selinux_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata,
+				     u32 *seclen)
+{
+	u32 secid = prop->selinux.secid;
+
+	/* scaffolding */
+	if (!secid)
+		secid = prop->scaffold.secid;
+
+	return selinux_secid_to_secctx(secid, secdata, seclen);
 }
 
 static int selinux_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid)
@@ -7347,6 +7358,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(inode_alloc_security, selinux_inode_alloc_security),
 	LSM_HOOK_INIT(sem_alloc_security, selinux_sem_alloc_security),
 	LSM_HOOK_INIT(secid_to_secctx, selinux_secid_to_secctx),
+	LSM_HOOK_INIT(lsmprop_to_secctx, selinux_lsmprop_to_secctx),
 	LSM_HOOK_INIT(inode_getsecctx, selinux_inode_getsecctx),
 	LSM_HOOK_INIT(sk_alloc_security, selinux_sk_alloc_security),
 	LSM_HOOK_INIT(tun_dev_alloc_security, selinux_tun_dev_alloc_security),

security/selinux/include/audit.h

@@ -49,7 +49,8 @@ void selinux_audit_rule_free(void *rule);
  * Returns 1 if the context id matches the rule, 0 if it does not, and
  * -errno on failure.
  */
-int selinux_audit_rule_match(struct lsm_prop *prop, u32 field, u32 op, void *rule);
+int selinux_audit_rule_match(struct lsm_prop *prop, u32 field, u32 op,
+			     void *rule);
 
 /**
  * selinux_audit_rule_known - check to see if rule contains selinux fields.

security/smack/smack_lsm.c

@@ -4768,7 +4768,7 @@ static int smack_audit_rule_known(struct audit_krule *krule)
 static int smack_audit_rule_match(struct lsm_prop *prop, u32 field, u32 op,
 				  void *vrule)
 {
-	struct smack_known *skp;
+	struct smack_known *skp = prop->smack.skp;
 	char *rule = vrule;
 
 	if (unlikely(!rule)) {
@@ -4780,10 +4780,8 @@ static int smack_audit_rule_match(struct lsm_prop *prop, u32 field, u32 op,
 		return 0;
 
 	/* scaffolding */
-	if (!prop->smack.skp && prop->scaffold.secid)
+	if (!skp && prop->scaffold.secid)
 		skp = smack_from_secid(prop->scaffold.secid);
-	else
-		skp = prop->smack.skp;
 
 	/*
 	 * No need to do string comparisons. If a match occurs,
@@ -4814,7 +4812,6 @@ static int smack_ismaclabel(const char *name)
 	return (strcmp(name, XATTR_SMACK_SUFFIX) == 0);
 }
 
-
 /**
  * smack_secid_to_secctx - return the smack label for a secid
  * @secid: incoming integer
@@ -4833,6 +4830,29 @@ static int smack_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 	return 0;
 }
 
+/**
+ * smack_lsmprop_to_secctx - return the smack label
+ * @prop: includes incoming Smack data
+ * @secdata: destination
+ * @seclen: how long it is
+ *
+ * Exists for audit code.
+ */
+static int smack_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata,
+				   u32 *seclen)
+{
+	struct smack_known *skp = prop->smack.skp;
+
+	/* scaffolding */
+	if (!skp && prop->scaffold.secid)
+		skp = smack_from_secid(prop->scaffold.secid);
+
+	if (secdata)
+		*secdata = skp->smk_known;
+	*seclen = strlen(skp->smk_known);
+	return 0;
+}
+
 /**
  * smack_secctx_to_secid - return the secid for a smack label
  * @secdata: smack label
@@ -5192,6 +5212,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
 
 	LSM_HOOK_INIT(ismaclabel, smack_ismaclabel),
 	LSM_HOOK_INIT(secid_to_secctx, smack_secid_to_secctx),
+	LSM_HOOK_INIT(lsmprop_to_secctx, smack_lsmprop_to_secctx),
 	LSM_HOOK_INIT(secctx_to_secid, smack_secctx_to_secid),
 	LSM_HOOK_INIT(inode_notifysecctx, smack_inode_notifysecctx),
 	LSM_HOOK_INIT(inode_setsecctx, smack_inode_setsecctx),