diff mbox

[01/19] Security: Add hook to calculate context based on a negative dentry.

Message ID 1364939160-20874-2-git-send-email-SteveD@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Steve Dickson April 2, 2013, 9:45 p.m. UTC 
From: David Quigley <dpquigl@davequigley.com>

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: Miguel Rodel Felipe <Rodel_FM@dsi.a-star.edu.sg>
Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@dsi.a-star.edu.sg>
Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@dsi.a-star.edu.sg>
---
 include/linux/security.h | 27 +++++++++++++++++++++++++++
 security/capability.c    |  8 ++++++++
 security/security.c      | 10 ++++++++++
 security/selinux/hooks.c | 35 +++++++++++++++++++++++++++++++++++
 4 files changed, 80 insertions(+)

Comments

Trond Myklebust April 2, 2013, 11:35 p.m. UTC | #1 
On Tue, 2013-04-02 at 17:45 -0400, Steve Dickson wrote:
> From: David Quigley <dpquigl@davequigley.com>
> 
> 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.
> 

Can you remind me again why this is needed? Basing security decisions on
the namespace seems just seems to run against the basic selinux concept.
Is it for apparmor and tomoyo support in LNFS?
Dave Quigley April 3, 2013, 7:57 p.m. UTC | #2 
On 04/02/2013 19:35, Myklebust, Trond wrote:
> On Tue, 2013-04-02 at 17:45 -0400, Steve Dickson wrote:
>> From: David Quigley <dpquigl@davequigley.com>
>>
>> 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.
>>
>
> Can you remind me again why this is needed? Basing security decisions 
> on
> the namespace seems just seems to run against the basic selinux 
> concept.
> Is it for apparmor and tomoyo support in LNFS?

The thing is we aren't creating it based on the namespace. The negative 
dentry has a reference to its parent which is the label being used for 
the computation. The problem is there is no way for us to do this 
calculation in NFS because the place it needs to be done is lacking the 
actual inode so instead we use the process and the parent label. If 
there is a transition in place it would act on the parent label and 
process label anyway. Its not like we're deciding that /usr/foo/bar gets 
labeled with bar_t but instead we're saying that process foo created a 
file in a directory labeled foo_t so it becomes bar_t. Alternatively if 
no transition is in place we'd instead say that because foo is labeled 
foo_t we're creating a file underneath that so it gets labeled foo_t.
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diff mbox

Patch

diff --git a/include/linux/security.h b/include/linux/security.h
index eee7478..a957e7a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -26,6 +26,7 @@ 
 #include <linux/capability.h>
 #include <linux/slab.h>
 #include <linux/err.h>
+#include <linux/string.h>
 
 struct linux_binprm;
 struct cred;
@@ -306,6 +307,15 @@  static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *	Parse a string of security data filling in the opts structure
  *	@options string containing all mount options known by the LSM
  *	@opts binary data structure usable by the LSM
+ * @dentry_init_security:
+ *	Compute a context for a dentry as the inode is not yet available
+ *	since NFSv4 has no label backed by an EA anyway.
+ *	@dentry dentry to use in calculating the context.
+ *	@mode mode used to determine resource type.
+ *	@name name of the last path component used to create file
+ *	@ctx pointer to place the pointer to the resulting context in.
+ *	@ctxlen point to place the length of the resulting context.
+ *
  *
  * Security hooks for inode operations.
  *
@@ -1439,6 +1449,10 @@  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,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen);
+
 
 #ifdef CONFIG_SECURITY_PATH
 	int (*path_unlink) (struct path *dir, struct dentry *dentry);
@@ -1724,6 +1738,9 @@  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,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen);
 
 int security_inode_alloc(struct inode *inode);
 void security_inode_free(struct inode *inode);
@@ -2028,6 +2045,16 @@  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,
+						 struct qstr *name,
+						 void **ctx,
+						 u32 *ctxlen)
+{
+	return -EOPNOTSUPP;
+}
+
+
 static inline int security_inode_init_security(struct inode *inode,
 						struct inode *dir,
 						const struct qstr *qstr,
diff --git a/security/capability.c b/security/capability.c
index 5797750..456bd9d 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -108,6 +108,13 @@  static int cap_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
 	return 0;
 }
 
+static int cap_dentry_init_security(struct dentry *dentry, int mode,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen)
+{
+	return 0;
+}
+
 static int cap_inode_alloc_security(struct inode *inode)
 {
 	return 0;
@@ -925,6 +932,7 @@  void __init security_fixup_ops(struct security_operations *ops)
 	set_to_cap_if_null(ops, sb_set_mnt_opts);
 	set_to_cap_if_null(ops, sb_clone_mnt_opts);
 	set_to_cap_if_null(ops, sb_parse_opts_str);
+	set_to_cap_if_null(ops, dentry_init_security);
 	set_to_cap_if_null(ops, inode_alloc_security);
 	set_to_cap_if_null(ops, inode_free_security);
 	set_to_cap_if_null(ops, inode_init_security);
diff --git a/security/security.c b/security/security.c
index 7b88c6a..723a10c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -12,6 +12,7 @@ 
  */
 
 #include <linux/capability.h>
+#include <linux/dcache.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -324,6 +325,15 @@  void security_inode_free(struct inode *inode)
 	security_ops->inode_free_security(inode);
 }
 
+int security_dentry_init_security(struct dentry *dentry, int mode,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen)
+{
+	return security_ops->dentry_init_security(dentry, mode, name,
+							ctx, ctxlen);
+}
+EXPORT_SYMBOL(security_dentry_init_security);
+
 int security_inode_init_security(struct inode *inode, struct inode *dir,
 				 const struct qstr *qstr,
 				 const initxattrs initxattrs, void *fs_data)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 2fa28c8..c7f1905 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2483,6 +2483,40 @@  static void selinux_inode_free_security(struct inode *inode)
 	inode_free_security(inode);
 }
 
+static int selinux_dentry_init_security(struct dentry *dentry, int mode,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen)
+{
+	const struct cred *cred = current_cred();
+	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 = cred->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),
+					     name,
+					     &newsid);
+		if (rc) {
+			printk(KERN_WARNING
+				"%s: security_transition_sid failed, rc=%d\n",
+			       __func__, -rc);
+			return rc;
+		}
+	}
+
+	return security_sid_to_context(newsid, (char **)ctx, ctxlen);
+}
+
 static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 				       const struct qstr *qstr, char **name,
 				       void **value, size_t *len)
@@ -5525,6 +5559,7 @@  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,