smack: Add a new '-CIPSO' option to the network address label configuration

This patch adds a new special option '-CIPSO' to the Smack subsystem. When used
in the netlabel list, it means "use CIPSO networking". A use case is when your
local network speaks CIPSO and you want also to connect to the unlabeled
Internet. This patch also add some documentation describing that. The patch
also corrects an oops when setting a '' SMACK64 xattr to a file.

Signed-off-by: Etienne Basset <etienne.basset@numericable.fr>
Signed-off-by: Paul Moore <paul.moore@hp.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 30 insertions, 8 deletions

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 856c8a287523..e03a7e19c73b 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -86,6 +86,9 @@ LIST_HEAD(smack_rule_list);
 
 static int smk_cipso_doi_value = SMACK_CIPSO_DOI_DEFAULT;
 
+const char *smack_cipso_option = SMACK_CIPSO_OPTION;
+
+
 #define SEQ_READ_FINISHED       1
 
 /*
@@ -565,6 +568,11 @@ static ssize_t smk_write_cipso(struct file *file, const char __user *buf,
                 goto unlockedout;
         }
 
+        /* labels cannot begin with a '-' */
+        if (data[0] == '-') {
+                rc = -EINVAL;
+                goto unlockedout;
+        }
         data[count] = '\0';
         rule = data;
         /*
@@ -808,9 +816,18 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
         if (m > BEBITS)
                 return -EINVAL;
 
-        sp = smk_import(smack, 0);
-        if (sp == NULL)
-                return -EINVAL;
+        /* if smack begins with '-', its an option, don't import it */
+        if (smack[0] != '-') {
+                sp = smk_import(smack, 0);
+                if (sp == NULL)
+                        return -EINVAL;
+        } else {
+                /* check known options */
+                if (strcmp(smack, smack_cipso_option) == 0)
+                        sp = (char *)smack_cipso_option;
+                else
+                        return -EINVAL;
+        }
 
         for (temp_mask = 0; m > 0; m--) {
                 temp_mask |= mask_bits;
@@ -849,18 +866,23 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
                         smk_netlbladdr_insert(skp);
                 }
         } else {
-                rc = netlbl_cfg_unlbl_static_del(&init_net, NULL,
-                        &skp->smk_host.sin_addr, &skp->smk_mask,
-                        PF_INET, &audit_info);
+                /* we delete the unlabeled entry, only if the previous label
+                 * wasnt the special CIPSO option */
+                if (skp->smk_label != smack_cipso_option)
+                        rc = netlbl_cfg_unlbl_static_del(&init_net, NULL,
+                                        &skp->smk_host.sin_addr, &skp->smk_mask,
+                                        PF_INET, &audit_info);
+                else
+                        rc = 0;
                 skp->smk_label = sp;
         }
 
         /*
          * Now tell netlabel about the single label nature of
          * this host so that incoming packets get labeled.
+         * but only if we didn't get the special CIPSO option
          */
-
-        if (rc == 0)
+        if (rc == 0 && sp != smack_cipso_option)
                 rc = netlbl_cfg_unlbl_static_add(&init_net, NULL,
                         &skp->smk_host.sin_addr, &skp->smk_mask, PF_INET,
                         smack_to_secid(skp->smk_label), &audit_info);