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>

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)

security/selinux/include/av_perm_to_string.h

@@ -14,12 +14,17 @@
    S_(SECCLASS_DIR, DIR__REPARENT, "reparent")
    S_(SECCLASS_DIR, DIR__SEARCH, "search")
    S_(SECCLASS_DIR, DIR__RMDIR, "rmdir")
+   S_(SECCLASS_DIR, DIR__OPEN, "open")
    S_(SECCLASS_FILE, FILE__EXECUTE_NO_TRANS, "execute_no_trans")
    S_(SECCLASS_FILE, FILE__ENTRYPOINT, "entrypoint")
    S_(SECCLASS_FILE, FILE__EXECMOD, "execmod")
+   S_(SECCLASS_FILE, FILE__OPEN, "open")
    S_(SECCLASS_CHR_FILE, CHR_FILE__EXECUTE_NO_TRANS, "execute_no_trans")
    S_(SECCLASS_CHR_FILE, CHR_FILE__ENTRYPOINT, "entrypoint")
    S_(SECCLASS_CHR_FILE, CHR_FILE__EXECMOD, "execmod")
+   S_(SECCLASS_CHR_FILE, CHR_FILE__OPEN, "open")
+   S_(SECCLASS_BLK_FILE, BLK_FILE__OPEN, "open")
+   S_(SECCLASS_FIFO_FILE, FIFO_FILE__OPEN, "open")
    S_(SECCLASS_FD, FD__USE, "use")
    S_(SECCLASS_TCP_SOCKET, TCP_SOCKET__CONNECTTO, "connectto")
    S_(SECCLASS_TCP_SOCKET, TCP_SOCKET__NEWCONN, "newconn")

security/selinux/include/av_permissions.h

@@ -79,6 +79,7 @@
 #define DIR__REPARENT                             0x00080000UL
 #define DIR__SEARCH                               0x00100000UL
 #define DIR__RMDIR                                0x00200000UL
+#define DIR__OPEN                                 0x00400000UL
 #define FILE__IOCTL                               0x00000001UL
 #define FILE__READ                                0x00000002UL
 #define FILE__WRITE                               0x00000004UL
@@ -99,6 +100,7 @@
 #define FILE__EXECUTE_NO_TRANS                    0x00020000UL
 #define FILE__ENTRYPOINT                          0x00040000UL
 #define FILE__EXECMOD                             0x00080000UL
+#define FILE__OPEN                                0x00100000UL
 #define LNK_FILE__IOCTL                           0x00000001UL
 #define LNK_FILE__READ                            0x00000002UL
 #define LNK_FILE__WRITE                           0x00000004UL
@@ -136,6 +138,7 @@
 #define CHR_FILE__EXECUTE_NO_TRANS                0x00020000UL
 #define CHR_FILE__ENTRYPOINT                      0x00040000UL
 #define CHR_FILE__EXECMOD                         0x00080000UL
+#define CHR_FILE__OPEN                            0x00100000UL
 #define BLK_FILE__IOCTL                           0x00000001UL
 #define BLK_FILE__READ                            0x00000002UL
 #define BLK_FILE__WRITE                           0x00000004UL
@@ -153,6 +156,7 @@
 #define BLK_FILE__SWAPON                          0x00004000UL
 #define BLK_FILE__QUOTAON                         0x00008000UL
 #define BLK_FILE__MOUNTON                         0x00010000UL
+#define BLK_FILE__OPEN                            0x00020000UL
 #define SOCK_FILE__IOCTL                          0x00000001UL
 #define SOCK_FILE__READ                           0x00000002UL
 #define SOCK_FILE__WRITE                          0x00000004UL
@@ -187,6 +191,7 @@
 #define FIFO_FILE__SWAPON                         0x00004000UL
 #define FIFO_FILE__QUOTAON                        0x00008000UL
 #define FIFO_FILE__MOUNTON                        0x00010000UL
+#define FIFO_FILE__OPEN                           0x00020000UL
 #define FD__USE                                   0x00000001UL
 #define SOCKET__IOCTL                             0x00000001UL
 #define SOCKET__READ                              0x00000002UL

security/selinux/include/security.h

@@ -48,11 +48,13 @@ extern int selinux_mls_enabled;
 /* Policy capabilities */
 enum {
 	POLICYDB_CAPABILITY_NETPEER,
+	POLICYDB_CAPABILITY_OPENPERM,
 	__POLICYDB_CAPABILITY_MAX
 };
 #define POLICYDB_CAPABILITY_MAX (__POLICYDB_CAPABILITY_MAX - 1)
 
 extern int selinux_policycap_netpeer;
+extern int selinux_policycap_openperm;
 
 int security_load_policy(void * data, size_t len);
 

security/selinux/selinuxfs.c

@@ -42,7 +42,8 @@
 
 /* Policy capability filenames */
 static char *policycap_names[] = {
-	"network_peer_controls"
+	"network_peer_controls",
+	"open_perms"
 };
 
 unsigned int selinux_checkreqprot = CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE;

security/selinux/ss/services.c

@@ -61,6 +61,7 @@ extern void selnl_notify_policyload(u32 seqno);
 unsigned int policydb_loaded_version;
 
 int selinux_policycap_netpeer;
+int selinux_policycap_openperm;
 
 /*
  * This is declared in avc.c
@@ -1308,6 +1309,8 @@ static void security_load_policycaps(void)
 {
 	selinux_policycap_netpeer = ebitmap_get_bit(&policydb.policycaps,
 						  POLICYDB_CAPABILITY_NETPEER);
+	selinux_policycap_openperm = ebitmap_get_bit(&policydb.policycaps,
+						  POLICYDB_CAPABILITY_OPENPERM);
 }
 
 extern void selinux_complete_init(void);