1 files changed, 356 insertions, 0 deletions
diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
new file mode 100644
index 000000000000..f6b5f6eed6dd
--- /dev/null
+++ b/security/smack/smack_access.c
@@ -0,0 +1,356 @@
+/*
+ * Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com>
+ *
+ *      This program is free software; you can redistribute it and/or modify
+ *      it under the terms of the GNU General Public License as published by
+ *      the Free Software Foundation, version 2.
+ *
+ * Author:
+ *      Casey Schaufler <casey@schaufler-ca.com>
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include "smack.h"
+
+struct smack_known smack_known_unset = {
+	.smk_next	= NULL,
+	.smk_known	= "UNSET",
+	.smk_secid	= 1,
+	.smk_cipso	= NULL,
+};
+
+struct smack_known smack_known_huh = {
+	.smk_next	= &smack_known_unset,
+	.smk_known	= "?",
+	.smk_secid	= 2,
+	.smk_cipso	= NULL,
+};
+
+struct smack_known smack_known_hat = {
+	.smk_next	= &smack_known_huh,
+	.smk_known	= "^",
+	.smk_secid	= 3,
+	.smk_cipso	= NULL,
+};
+
+struct smack_known smack_known_star = {
+	.smk_next	= &smack_known_hat,
+	.smk_known	= "*",
+	.smk_secid	= 4,
+	.smk_cipso	= NULL,
+};
+
+struct smack_known smack_known_floor = {
+	.smk_next	= &smack_known_star,
+	.smk_known	= "_",
+	.smk_secid	= 5,
+	.smk_cipso	= NULL,
+};
+
+struct smack_known smack_known_invalid = {
+	.smk_next	= &smack_known_floor,
+	.smk_known	= "",
+	.smk_secid	= 6,
+	.smk_cipso	= NULL,
+};
+
+struct smack_known *smack_known = &smack_known_invalid;
+
+/*
+ * The initial value needs to be bigger than any of the
+ * known values above.
+ */
+static u32 smack_next_secid = 10;
+
+/**
+ * smk_access - determine if a subject has a specific access to an object
+ * @subject_label: a pointer to the subject's Smack label
+ * @object_label: a pointer to the object's Smack label
+ * @request: the access requested, in "MAY" format
+ *
+ * This function looks up the subject/object pair in the
+ * access rule list and returns 0 if the access is permitted,
+ * non zero otherwise.
+ *
+ * Even though Smack labels are usually shared on smack_list
+ * labels that come in off the network can't be imported
+ * and added to the list for locking reasons.
+ *
+ * Therefore, it is necessary to check the contents of the labels,
+ * not just the pointer values. Of course, in most cases the labels
+ * will be on the list, so checking the pointers may be a worthwhile
+ * optimization.
+ */
+int smk_access(char *subject_label, char *object_label, int request)
+{
+	u32 may = MAY_NOT;
+	struct smk_list_entry *sp;
+	struct smack_rule *srp;
+
+	/*
+	 * Hardcoded comparisons.
+	 *
+	 * A star subject can't access any object.
+	 */
+	if (subject_label == smack_known_star.smk_known ||
+	    strcmp(subject_label, smack_known_star.smk_known) == 0)
+		return -EACCES;
+	/*
+	 * A star object can be accessed by any subject.
+	 */
+	if (object_label == smack_known_star.smk_known ||
+	    strcmp(object_label, smack_known_star.smk_known) == 0)
+		return 0;
+	/*
+	 * An object can be accessed in any way by a subject
+	 * with the same label.
+	 */
+	if (subject_label == object_label ||
+	    strcmp(subject_label, object_label) == 0)
+		return 0;
+	/*
+	 * A hat subject can read any object.
+	 * A floor object can be read by any subject.
+	 */
+	if ((request & MAY_ANYREAD) == request) {
+		if (object_label == smack_known_floor.smk_known ||
+		    strcmp(object_label, smack_known_floor.smk_known) == 0)
+			return 0;
+		if (subject_label == smack_known_hat.smk_known ||
+		    strcmp(subject_label, smack_known_hat.smk_known) == 0)
+			return 0;
+	}
+	/*
+	 * Beyond here an explicit relationship is required.
+	 * If the requested access is contained in the available
+	 * access (e.g. read is included in readwrite) it's
+	 * good.
+	 */
+	for (sp = smack_list; sp != NULL; sp = sp->smk_next) {
+		srp = &sp->smk_rule;
+
+		if (srp->smk_subject == subject_label ||
+		    strcmp(srp->smk_subject, subject_label) == 0) {
+			if (srp->smk_object == object_label ||
+			    strcmp(srp->smk_object, object_label) == 0) {
+				may = srp->smk_access;
+				break;
+			}
+		}
+	}
+	/*
+	 * This is a bit map operation.
+	 */
+	if ((request & may) == request)
+		return 0;
+
+	return -EACCES;
+}
+
+/**
+ * smk_curacc - determine if current has a specific access to an object
+ * @object_label: a pointer to the object's Smack label
+ * @request: the access requested, in "MAY" format
+ *
+ * This function checks the current subject label/object label pair
+ * in the access rule list and returns 0 if the access is permitted,
+ * non zero otherwise. It allows that current my have the capability
+ * to override the rules.
+ */
+int smk_curacc(char *obj_label, u32 mode)
+{
+	int rc;
+
+	rc = smk_access(current->security, obj_label, mode);
+	if (rc == 0)
+		return 0;
+
+	if (capable(CAP_MAC_OVERRIDE))
+		return 0;
+
+	return rc;
+}
+
+static DEFINE_MUTEX(smack_known_lock);
+
+/**
+ * smk_import_entry - import a label, return the list entry
+ * @string: a text string that might be a Smack label
+ * @len: the maximum size, or zero if it is NULL terminated.
+ *
+ * Returns a pointer to the entry in the label list that
+ * matches the passed string, adding it if necessary.
+ */
+struct smack_known *smk_import_entry(const char *string, int len)
+{
+	struct smack_known *skp;
+	char smack[SMK_LABELLEN];
+	int found;
+	int i;
+
+	if (len <= 0 || len > SMK_MAXLEN)
+		len = SMK_MAXLEN;
+
+	for (i = 0, found = 0; i < SMK_LABELLEN; i++) {
+		if (found)
+			smack[i] = '\0';
+		else if (i >= len || string[i] > '~' || string[i] <= ' ' ||
+			 string[i] == '/') {
+			smack[i] = '\0';
+			found = 1;
+		} else
+			smack[i] = string[i];
+	}
+
+	if (smack[0] == '\0')
+		return NULL;
+
+	mutex_lock(&smack_known_lock);
+
+	for (skp = smack_known; skp != NULL; skp = skp->smk_next)
+		if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0)
+			break;
+
+	if (skp == NULL) {
+		skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL);
+		if (skp != NULL) {
+			skp->smk_next = smack_known;
+			strncpy(skp->smk_known, smack, SMK_MAXLEN);
+			skp->smk_secid = smack_next_secid++;
+			skp->smk_cipso = NULL;
+			spin_lock_init(&skp->smk_cipsolock);
+			/*
+			 * Make sure that the entry is actually
+			 * filled before putting it on the list.
+			 */
+			smp_mb();
+			smack_known = skp;
+		}
+	}
+
+	mutex_unlock(&smack_known_lock);
+
+	return skp;
+}
+
+/**
+ * smk_import - import a smack label
+ * @string: a text string that might be a Smack label
+ * @len: the maximum size, or zero if it is NULL terminated.
+ *
+ * Returns a pointer to the label in the label list that
+ * matches the passed string, adding it if necessary.
+ */
+char *smk_import(const char *string, int len)
+{
+	struct smack_known *skp;
+
+	skp = smk_import_entry(string, len);
+	if (skp == NULL)
+		return NULL;
+	return skp->smk_known;
+}
+
+/**
+ * smack_from_secid - find the Smack label associated with a secid
+ * @secid: an integer that might be associated with a Smack label
+ *
+ * Returns a pointer to the appropraite Smack label if there is one,
+ * otherwise a pointer to the invalid Smack label.
+ */
+char *smack_from_secid(const u32 secid)
+{
+	struct smack_known *skp;
+
+	for (skp = smack_known; skp != NULL; skp = skp->smk_next)
+		if (skp->smk_secid == secid)
+			return skp->smk_known;
+
+	/*
+	 * If we got this far someone asked for the translation
+	 * of a secid that is not on the list.
+	 */
+	return smack_known_invalid.smk_known;
+}
+
+/**
+ * smack_to_secid - find the secid associated with a Smack label
+ * @smack: the Smack label
+ *
+ * Returns the appropriate secid if there is one,
+ * otherwise 0
+ */
+u32 smack_to_secid(const char *smack)
+{
+	struct smack_known *skp;
+
+	for (skp = smack_known; skp != NULL; skp = skp->smk_next)
+		if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0)
+			return skp->smk_secid;
+	return 0;
+}
+
+/**
+ * smack_from_cipso - find the Smack label associated with a CIPSO option
+ * @level: Bell & LaPadula level from the network
+ * @cp: Bell & LaPadula categories from the network
+ * @result: where to put the Smack value
+ *
+ * This is a simple lookup in the label table.
+ *
+ * This is an odd duck as far as smack handling goes in that
+ * it sends back a copy of the smack label rather than a pointer
+ * to the master list. This is done because it is possible for
+ * a foreign host to send a smack label that is new to this
+ * machine and hence not on the list. That would not be an
+ * issue except that adding an entry to the master list can't
+ * be done at that point.
+ */
+void smack_from_cipso(u32 level, char *cp, char *result)
+{
+	struct smack_known *kp;
+	char *final = NULL;
+
+	for (kp = smack_known; final == NULL && kp != NULL; kp = kp->smk_next) {
+		if (kp->smk_cipso == NULL)
+			continue;
+
+		spin_lock_bh(&kp->smk_cipsolock);
+
+		if (kp->smk_cipso->smk_level == level &&
+		    memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0)
+			final = kp->smk_known;
+
+		spin_unlock_bh(&kp->smk_cipsolock);
+	}
+	if (final == NULL)
+		final = smack_known_huh.smk_known;
+	strncpy(result, final, SMK_MAXLEN);
+	return;
+}
+
+/**
+ * smack_to_cipso - find the CIPSO option to go with a Smack label
+ * @smack: a pointer to the smack label in question
+ * @cp: where to put the result
+ *
+ * Returns zero if a value is available, non-zero otherwise.
+ */
+int smack_to_cipso(const char *smack, struct smack_cipso *cp)
+{
+	struct smack_known *kp;
+
+	for (kp = smack_known; kp != NULL; kp = kp->smk_next)
+		if (kp->smk_known == smack ||
+		    strcmp(kp->smk_known, smack) == 0)
+			break;
+
+	if (kp == NULL || kp->smk_cipso == NULL)
+		return -ENOENT;
+
+	memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso));
+	return 0;
+}