Re: [PATCH 05/17] Security: Add Hook to test if the particular xattr is part of a MAC model.

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Apr 24, 2013 at 04:17:51PM -0400, Steve Dickson wrote:
> From: David Quigley <dpquigl@davequigley.com>
> 
> The interface to request security labels from user space is the xattr
> interface. When requesting the security label from an NFS server it is
> important to make sure the requested xattr actually is a MAC label. 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.

Ditto.--b.

> 
> 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   | 14 ++++++++++++++
>  security/capability.c      |  6 ++++++
>  security/security.c        |  6 ++++++
>  security/selinux/hooks.c   |  6 ++++++
>  security/smack/smack_lsm.c | 11 +++++++++++
>  5 files changed, 43 insertions(+)
> 
> diff --git a/include/linux/security.h b/include/linux/security.h
> index f3d7956..934f96f 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1323,6 +1323,13 @@ 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. Returns 1 if name is a MAC
> + *	attribute otherwise returns 0.
> + *	@name full extended attribute name to check against
> + *	LSM as a MAC label.
> + *
>   * @secid_to_secctx:
>   *	Convert secid to security context.  If secdata is NULL the length of
>   *	the result will be returned in seclen, but no secdata will be returned.
> @@ -1604,6 +1611,7 @@ 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);
> @@ -1857,6 +1865,7 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode);
>  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_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);
> @@ -2545,6 +2554,11 @@ static inline int security_netlink_send(struct sock *sk, struct sk_buff *skb)
>  	return cap_netlink_send(sk, skb);
>  }
>  
> +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/capability.c b/security/capability.c
> index 782045e..71e5052 100644
> --- a/security/capability.c
> +++ b/security/capability.c
> @@ -822,6 +822,11 @@ static int cap_setprocattr(struct task_struct *p, char *name, void *value,
>  	return -EINVAL;
>  }
>  
> +static int cap_ismaclabel(const char *name)
> +{
> +	return 0;
> +}
> +
>  static int cap_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
>  {
>  	return -EOPNOTSUPP;
> @@ -1041,6 +1046,7 @@ void __init security_fixup_ops(struct security_operations *ops)
>  	set_to_cap_if_null(ops, d_instantiate);
>  	set_to_cap_if_null(ops, getprocattr);
>  	set_to_cap_if_null(ops, setprocattr);
> +	set_to_cap_if_null(ops, ismaclabel);
>  	set_to_cap_if_null(ops, secid_to_secctx);
>  	set_to_cap_if_null(ops, secctx_to_secid);
>  	set_to_cap_if_null(ops, release_secctx);
> diff --git a/security/security.c b/security/security.c
> index 7c18e3c..07391f3 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1057,6 +1057,12 @@ int security_netlink_send(struct sock *sk, struct sk_buff *skb)
>  	return security_ops->netlink_send(sk, skb);
>  }
>  
> +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 622b205..273e28b 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5423,6 +5423,11 @@ abort_change:
>  	return error;
>  }
>  
> +static int selinux_ismaclabel(const char *name)
> +{
> +	return (strcmp(name, XATTR_SELINUX_SUFFIX) == 0);
> +}
> +
>  static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
>  {
>  	return security_sid_to_context(secid, secdata, seclen);
> @@ -5661,6 +5666,7 @@ 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 fa64740..ca01d71 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -3329,6 +3329,16 @@ 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.
> + */
> +static int smack_ismaclabel(const char *name)
> +{
> +	return (strcmp(name, XATTR_SMACK_SUFFIX) == 0);
> +}
> +
> +
> +/**
>   * smack_secid_to_secctx - return the smack label for a secid
>   * @secid: incoming integer
>   * @secdata: destination
> @@ -3524,6 +3534,7 @@ 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,
> -- 
> 1.8.1.4
> 
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