Re: [PATCH 02/14] Security: Add Hook to test if the particular xattr is part of a MAC model.

[Steve Dickson <SteveD@redhat.com>]

On 29/03/13 07:43, Mimi Zohar wrote:
> On Thu, 2013-03-28 at 09:53 -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.
>>
>> 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 a957e7a..8a6faff 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -1319,6 +1319,13 @@ 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 0 if name is a MAC
>> + *	attribute otherwise returns non-zero.
> 
> Sorry, the comment doesn't match the code.
Nice catch! thanks!

steved.

> 
> Mimi
> 
>> + *	@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.
>> @@ -1600,6 +1607,7 @@ 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);
>> @@ -1852,6 +1860,7 @@ 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);
>> @@ -2540,6 +2549,11 @@ 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 456bd9d..07a6484 100644
>> --- a/security/capability.c
>> +++ b/security/capability.c
>> @@ -817,6 +817,11 @@ 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;
>> @@ -1036,6 +1041,7 @@ 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 723a10c..6d7389c 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 c7f1905..97231a0 100644
>> --- a/security/selinux/hooks.c
>> +++ b/security/selinux/hooks.c
>> @@ -5417,6 +5417,11 @@ 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);
>> @@ -5655,6 +5660,7 @@ 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,
> 
> 
>