[PATCH 02/11] Security: Add hook to calculate context based on a negative dentry.

David P. Quigley
2008-02-27T23:11:17Z

There is a time where we need to calculate a context without the
inode having been created yet. To do this we take the negative dentry and
calculate a context based on the process and the parent directory contexts.

Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
---
include/linux/security.h | 11 +++++++++++
security/dummy.c | 7 +++++++
security/security.c | 9 +++++++++
security/selinux/hooks.c | 38 ++++++++++++++++++++++++++++++++++++++
4 files changed, 65 insertions(+), 0 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index c80bee4..9038f34 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1264,6 +1264,8 @@ struct security_operations {
void (*sb_clone_mnt_opts) (const struct super_block *oldsb,
struct super_block *newsb);

+ int (*dentry_init_security) (struct dentry *dentry, int mode,
+ void **ctx, u32 *ctxlen);
int (*inode_alloc_security) (struct inode *inode);
void (*inode_free_security) (struct inode *inode);
int (*inode_init_security) (struct inode *inode, struct inode *dir,
@@ -1528,6 +1530,7 @@ int security_sb_set_mnt_opts(struct super_block *sb, char **mount_options,
void security_sb_clone_mnt_opts(const struct super_block *oldsb,
struct super_block *newsb);

+int security_dentry_init_security(struct dentry *dentry, int mode, void **ctx, u32 *ctxlen);
int security_inode_alloc(struct inode *inode);
void security_inode_free(struct inode *inode);
int security_inode_init_security(struct inode *inode, struct inode *dir,
@@ -1822,6 +1825,14 @@ static inline void security_sb_post_pivotroot (struct nameidata *old_nd,
struct nameidata *new_nd)
{ }

+static inline int security_dentry_init_security(struct dentry *dentry,
+ int mode,
+ void **ctx,
+ u32 *ctxlen)
+{
+ return 0;
+}
+
static inline int security_inode_alloc (struct inode *inode)
{
return 0;
diff --git a/security/dummy.c b/security/dummy.c
index 928ef41..d322c73 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -268,6 +268,12 @@ static void dummy_sb_clone_mnt_opts(const struct super_block *oldsb,
return;
}

+static int dummy_dentry_init_security(struct dentry *dentry, int mode,
+ void **ctx, u32 *ctxlen)
+{
+ return -EOPNOTSUPP;
+}
+
static int dummy_inode_alloc_security (struct inode *inode)
{
return 0;
@@ -1033,6 +1039,7 @@ void security_fixup_ops (struct security_operations *ops)
set_to_dummy_if_null(ops, sb_get_mnt_opts);
set_to_dummy_if_null(ops, sb_set_mnt_opts);
set_to_dummy_if_null(ops, sb_clone_mnt_opts);
+ set_to_dummy_if_null(ops, dentry_init_security);
set_to_dummy_if_null(ops, inode_alloc_security);
set_to_dummy_if_null(ops, inode_free_security);
set_to_dummy_if_null(ops, inode_init_security);
diff --git a/security/security.c b/security/security.c
index 1a84eb1..b6e80bb 100644
--- a/security/security.c
+++ b/security/security.c
@@ -325,6 +325,15 @@ void security_sb_clone_mnt_opts(const struct super_block *oldsb,
security_ops->sb_clone_mnt_opts(oldsb, newsb);
}

+int security_dentry_init_security(struct dentry *dentry,
+ int mode,
+ void **ctx,
+ u32 *ctxlen)
+{
+ return security_ops->dentry_init_security(dentry, mode, ctx, ctxlen);
+}
+EXPORT_SYMBOL(security_dentry_init_security);
+
int security_inode_alloc(struct inode *inode)
{
inode->i_security = NULL;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e7fc9c9..a56b21a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -63,6 +63,7 @@
#include <linux/udp.h>
#include <linux/dccp.h>
#include <linux/quota.h>
+#include <linux/fsnotify.h>
#include <linux/un.h> /* for Unix socket types */
#include <net/af_unix.h> /* for Unix socket types */
#include <linux/parser.h>
@@ -2358,6 +2359,42 @@ static int selinux_umount(struct vfsmount *mnt, int flags)

/* inode security operations */

+/*
+ * For now, we need a way to compute a SID for
+ * a dentry as the inode is not yet available
+ * (and under NFSv4 has no label backed by an EA anyway.
+ */
+static int selinux_dentry_init_security(struct dentry *dentry, int mode,
+ void **ctx, u32 *ctxlen)
+{
+ struct task_security_struct *tsec;
+ struct inode_security_struct *dsec;
+ struct superblock_security_struct *sbsec;
+ struct inode *dir = dentry->d_parent->d_inode;
+ u32 newsid;
+ int rc;
+
+ tsec = current->security;
+ dsec = dir->i_security;
+ sbsec = dir->i_sb->s_security;
+
+ if (tsec->create_sid && sbsec->behavior != SECURITY_FS_USE_MNTPOINT) {
+ newsid = tsec->create_sid;
+ } else {
+ rc = security_transition_sid(tsec->sid, dsec->sid,
+ inode_mode_to_security_class(mode),
+ &newsid);
+ if (rc) {
+ printk(KERN_WARNING "%s: "
+ "security_transition_sid failed, rc=%d\n",
+ __FUNCTION__, -rc);
+ return rc;
+ }
+ }
+
+ return security_sid_to_context(newsid, (char **)ctx, ctxlen);
+}
+
static int selinux_inode_alloc_security(struct inode *inode)
{
return inode_alloc_security(inode);
@@ -5257,6 +5294,7 @@ static struct security_operations selinux_ops = {
.sb_set_mnt_opts = selinux_set_mnt_opts,
.sb_clone_mnt_opts = selinux_sb_clone_mnt_opts,

+ .dentry_init_security = selinux_dentry_init_security,
.inode_alloc_security = selinux_inode_alloc_security,
.inode_free_security = selinux_inode_free_security,
.inode_init_security = selinux_inode_init_security,
--
1.5.3.8