SELinux: create new open permission

Adds a new open permission inside SELinux when 'opening' a file.  The idea
is that opening a file and reading/writing to that file are not the same
thing.  Its different if a program had its stdout redirected to /tmp/output
than if the program tried to directly open /tmp/output. This should allow
policy writers to more liberally give read/write permissions across the
policy while still blocking many design and programing flaws SELinux is so
good at catching today.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 30 insertions, 1 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 710894d4841b..d569cde440e6 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1615,6 +1615,35 @@ static inline u32 file_mask_to_av(int mode, int mask)
         return av;
 }
 
+/*
+ * Convert a file mask to an access vector and include the correct open
+ * open permission.
+ */
+static inline u32 open_file_mask_to_av(int mode, int mask)
+{
+        u32 av = file_mask_to_av(mode, mask);
+
+        if (selinux_policycap_openperm) {
+                /*
+                 * lnk files and socks do not really have an 'open'
+                 */
+                if (S_ISREG(mode))
+                        av |= FILE__OPEN;
+                else if (S_ISCHR(mode))
+                        av |= CHR_FILE__OPEN;
+                else if (S_ISBLK(mode))
+                        av |= BLK_FILE__OPEN;
+                else if (S_ISFIFO(mode))
+                        av |= FIFO_FILE__OPEN;
+                else if (S_ISDIR(mode))
+                        av |= DIR__OPEN;
+                else
+                        printk(KERN_ERR "SELinux: WARNING: inside open_file_to_av "
+                                "with unknown mode:%x\n", mode);
+        }
+        return av;
+}
+
 /* Convert a Linux file to an access vector. */
 static inline u32 file_to_av(struct file *file)
 {
@@ -2532,7 +2561,7 @@ static int selinux_inode_permission(struct inode *inode, int mask,
         }
 
         return inode_has_perm(current, inode,
-                               file_mask_to_av(inode->i_mode, mask), NULL);
+                               open_file_mask_to_av(inode->i_mode, mask), NULL);
 }
 
 static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)