SELinux: allow userspace to read policy back out of the kernel

There is interest in being able to see what the actual policy is that was
loaded into the kernel.  The patch creates a new selinuxfs file
/selinux/policy which can be read by userspace.  The actual policy that is
loaded into the kernel will be written back out to userspace.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 123 insertions, 0 deletions

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index c91e150c3087..655fe1c6cc69 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -490,6 +490,129 @@ err:
 	return rc;
 }
 
+int cond_write_bool(void *vkey, void *datum, void *ptr)
+{
+	char *key = vkey;
+	struct cond_bool_datum *booldatum = datum;
+	struct policy_data *pd = ptr;
+	void *fp = pd->fp;
+	__le32 buf[3];
+	u32 len;
+	int rc;
+
+	len = strlen(key);
+	buf[0] = cpu_to_le32(booldatum->value);
+	buf[1] = cpu_to_le32(booldatum->state);
+	buf[2] = cpu_to_le32(len);
+	rc = put_entry(buf, sizeof(u32), 3, fp);
+	if (rc)
+		return rc;
+	rc = put_entry(key, 1, len, fp);
+	if (rc)
+		return rc;
+	return 0;
+}
+
+/*
+ * cond_write_cond_av_list doesn't write out the av_list nodes.
+ * Instead it writes out the key/value pairs from the avtab. This
+ * is necessary because there is no way to uniquely identifying rules
+ * in the avtab so it is not possible to associate individual rules
+ * in the avtab with a conditional without saving them as part of
+ * the conditional. This means that the avtab with the conditional
+ * rules will not be saved but will be rebuilt on policy load.
+ */
+static int cond_write_av_list(struct policydb *p,
+			      struct cond_av_list *list, struct policy_file *fp)
+{
+	__le32 buf[1];
+	struct cond_av_list *cur_list;
+	u32 len;
+	int rc;
+
+	len = 0;
+	for (cur_list = list; cur_list != NULL; cur_list = cur_list->next)
+		len++;
+
+	buf[0] = cpu_to_le32(len);
+	rc = put_entry(buf, sizeof(u32), 1, fp);
+	if (rc)
+		return rc;
+
+	if (len == 0)
+		return 0;
+
+	for (cur_list = list; cur_list != NULL; cur_list = cur_list->next) {
+		rc = avtab_write_item(p, cur_list->node, fp);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+int cond_write_node(struct policydb *p, struct cond_node *node,
+		    struct policy_file *fp)
+{
+	struct cond_expr *cur_expr;
+	__le32 buf[2];
+	int rc;
+	u32 len = 0;
+
+	buf[0] = cpu_to_le32(node->cur_state);
+	rc = put_entry(buf, sizeof(u32), 1, fp);
+	if (rc)
+		return rc;
+
+	for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next)
+		len++;
+
+	buf[0] = cpu_to_le32(len);
+	rc = put_entry(buf, sizeof(u32), 1, fp);
+	if (rc)
+		return rc;
+
+	for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next) {
+		buf[0] = cpu_to_le32(cur_expr->expr_type);
+		buf[1] = cpu_to_le32(cur_expr->bool);
+		rc = put_entry(buf, sizeof(u32), 2, fp);
+		if (rc)
+			return rc;
+	}
+
+	rc = cond_write_av_list(p, node->true_list, fp);
+	if (rc)
+		return rc;
+	rc = cond_write_av_list(p, node->false_list, fp);
+	if (rc)
+		return rc;
+
+	return 0;
+}
+
+int cond_write_list(struct policydb *p, struct cond_node *list, void *fp)
+{
+	struct cond_node *cur;
+	u32 len;
+	__le32 buf[1];
+	int rc;
+
+	len = 0;
+	for (cur = list; cur != NULL; cur = cur->next)
+		len++;
+	buf[0] = cpu_to_le32(len);
+	rc = put_entry(buf, sizeof(u32), 1, fp);
+	if (rc)
+		return rc;
+
+	for (cur = list; cur != NULL; cur = cur->next) {
+		rc = cond_write_node(p, cur, fp);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
 /* Determine whether additional permissions are granted by the conditional
  * av table, and if so, add them to the result
  */