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Subject[PATCH 03/14] Security: Add hook to calculate context based on a negative dentry.
Date
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: Matthew N. Dodd <Matthew.Dodd@sparta.com>
Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
---
include/linux/security.h | 14 ++++++++++++++
security/security.c | 7 +++++++
security/selinux/hooks.c | 36 ++++++++++++++++++++++++++++++++++++
3 files changed, 57 insertions(+), 0 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index 8b5b041..42b9128 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1379,6 +1379,9 @@ struct security_operations {
void (*sb_clone_mnt_opts) (const struct super_block *oldsb,
struct super_block *newsb);
int (*sb_parse_opts_str) (char *options, struct security_mnt_opts *opts);
+ 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);
@@ -1651,6 +1654,8 @@ int security_sb_set_mnt_opts(struct super_block *sb, struct security_mnt_opts *o
void security_sb_clone_mnt_opts(const struct super_block *oldsb,
struct super_block *newsb);
int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
+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);
@@ -1994,6 +1999,15 @@ static inline int security_inode_alloc(struct inode *inode)
static inline void security_inode_free(struct inode *inode)
{ }

+static inline int security_dentry_init_security (struct dentry *dentry,
+ int mode,
+ void **ctx,
+ u32 *ctxlen)
+{
+ return -EOPNOTSUPP;
+}
+
+
static inline int security_inode_init_security(struct inode *inode,
struct inode *dir,
char **name,
diff --git a/security/security.c b/security/security.c
index d0fd42a..b22a110 100644
--- a/security/security.c
+++ b/security/security.c
@@ -349,6 +349,13 @@ void security_inode_free(struct inode *inode)
security_ops->inode_free_security(inode);
}

+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_init_security(struct inode *inode, struct inode *dir,
char **name, void **value, size_t *len)
{
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index b07871b..680db1d 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2504,6 +2504,41 @@ static void selinux_inode_free_security(struct inode *inode)
inode_free_security(inode);
}

+/*
+ * 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_init_security(struct inode *inode, struct inode *dir,
char **name, void **value,
size_t *len)
@@ -5413,6 +5448,7 @@ static struct security_operations selinux_ops = {
.sb_clone_mnt_opts = selinux_sb_clone_mnt_opts,
.sb_parse_opts_str = selinux_parse_opts_str,

+ .dentry_init_security = selinux_dentry_init_security,

.inode_alloc_security = selinux_inode_alloc_security,
.inode_free_security = selinux_inode_free_security,
--
1.5.5.1


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