Re: [PATCH 04/14] Security: Add Hook to test if the particular xattr is part of a MAC model.

[Casey Schaufler <casey@schaufler-ca.com>]

David P. Quigley wrote:
> There are areas in the Labeled NFS code where where we need to test if the
> attribute being requested exhibits the semantics of a MAC model. This allows us
> to make sure that we get the desired semantics from the attribute instead of
> something else such as capabilities or a time based LSM.
>
> Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
> Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
> ---
>  include/linux/security.h   |   11 +++++++++++
>  security/security.c        |    6 ++++++
>  security/selinux/hooks.c   |    6 ++++++
>  security/smack/smack_lsm.c |   11 +++++++++++
>  4 files changed, 34 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 42b9128..3031e6c 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1244,6 +1244,10 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
>   *	@pages contains the number of pages.
>   *	Return 0 if permission is granted.
>   *
> + * @ismaclabel:
> + * 	Check if the extended attribute specified by @name represents a MAC label.
> + * 	@name full extended attribute name to check against LSM as a MAC label.
> + *
>   * @secid_to_secctx:
>   *	Convert secid to security context.
>   *	@secid contains the security ID.
> @@ -1508,6 +1512,7 @@ struct security_operations {
>  
>  	int (*getprocattr) (struct task_struct *p, char *name, char **value);
>  	int (*setprocattr) (struct task_struct *p, char *name, void *value, size_t size);
> +	int (*ismaclabel) (const char * name);
>  	int (*secid_to_secctx) (u32 secid, char **secdata, u32 *seclen);
>  	int (*secctx_to_secid) (const char *secdata, u32 seclen, u32 *secid);
>  	void (*release_secctx) (char *secdata, u32 seclen);
> @@ -1762,6 +1767,7 @@ int security_getprocattr(struct task_struct *p, char *name, char **value);
>  int security_setprocattr(struct task_struct *p, char *name, void *value, size_t size);
>  int security_netlink_send(struct sock *sk, struct sk_buff *skb);
>  int security_netlink_recv(struct sk_buff *skb, int cap);
> +int security_ismaclabel(const char *name);
>  int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
>  int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
>  void security_release_secctx(char *secdata, u32 seclen);
> @@ -2494,6 +2500,11 @@ static inline void securityfs_remove(struct dentry *dentry)
>  {
>  }
>  
> +static inline int security_ismaclabel(const char *name)
> +{
> +	return 0;
> +}
> +
>  static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
>  {
>  	return -EOPNOTSUPP;
> diff --git a/security/security.c b/security/security.c
> index b22a110..1955094 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -858,6 +858,12 @@ int security_netlink_recv(struct sk_buff *skb, int cap)
>  }
>  EXPORT_SYMBOL(security_netlink_recv);
>  
> +int security_ismaclabel(const char *name)
> +{
> +	return security_ops->ismaclabel(name);
> +}
> +EXPORT_SYMBOL(security_ismaclabel);
> +
>  int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
>  {
>  	return security_ops->secid_to_secctx(secid, secdata, seclen);
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 680db1d..248fa5c 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5305,6 +5305,11 @@ static int selinux_setprocattr(struct task_struct *p,
>  	return size;
>  }
>  
> +static int selinux_ismaclabel(const char *name)
> +{
> +	return (strcmp(name,XATTR_NAME_SELINUX) == 0);
> +}
> +
>  static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
>  {
>  	return security_sid_to_context(secid, secdata, seclen);
> @@ -5546,6 +5551,7 @@ static struct security_operations selinux_ops = {
>  	.getprocattr =			selinux_getprocattr,
>  	.setprocattr =			selinux_setprocattr,
>  
> +	.ismaclabel =			selinux_ismaclabel,
>  	.secid_to_secctx =		selinux_secid_to_secctx,
>  	.secctx_to_secid =		selinux_secctx_to_secid,
>  	.release_secctx =		selinux_release_secctx,
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 87d7541..6b03a18 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -2526,6 +2526,16 @@ static void smack_audit_rule_free(void *vrule)
>  #endif /* CONFIG_AUDIT */
>  
>  /*
> + * smack_ismaclabel - check if xattr @name references a smack MAC label
> + * @name: Full xattr name to check.
> + *
>   
Lose the blank line in the comment.


> + */
> +static int smack_ismaclabel(const char *name)
> +{
> +	return (strcmp(name,XATTR_NAME_SMACK) == 0);
>   
Space after the comma.


> +}
> +
> +/*
>   * smack_secid_to_secctx - return the smack label for a secid
>   * @secid: incoming integer
>   * @secdata: destination
> @@ -2703,6 +2713,7 @@ struct security_operations smack_ops = {
>  	.audit_rule_free =		smack_audit_rule_free,
>  #endif /* CONFIG_AUDIT */
>  
> +	.ismaclabel =			smack_ismaclabel,
>  	.secid_to_secctx = 		smack_secid_to_secctx,
>  	.secctx_to_secid = 		smack_secctx_to_secid,
>  	.release_secctx = 		smack_release_secctx,
>