diff mbox series

[v10,12/27] ima: Define mac_admin_ns_capable() as a wrapper for ns_capable()

Message ID 20220201203735.164593-13-stefanb@linux.ibm.com (mailing list archive)
State New, archived
Headers show
Series ima: Namespace IMA with audit support in IMA-ns | expand

Commit Message

Stefan Berger Feb. 1, 2022, 8:37 p.m. UTC 
Define mac_admin_ns_capable() as a wrapper for the combined ns_capable()
checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return
true on the check if either capability or both are available.

Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This will allow
an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has
less privileges than CAP_SYS_ADMIN.

Signed-off-by: Denis Semakin <denis.semakin@huawei.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 include/linux/capability.h      | 6 ++++++
 security/integrity/ima/ima.h    | 6 ++++++
 security/integrity/ima/ima_fs.c | 5 ++++-
 3 files changed, 16 insertions(+), 1 deletion(-)

Comments

Serge E. Hallyn Feb. 5, 2022, 5:58 a.m. UTC | #1 
On Tue, Feb 01, 2022 at 03:37:20PM -0500, Stefan Berger wrote:
> Define mac_admin_ns_capable() as a wrapper for the combined ns_capable()
> checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return
> true on the check if either capability or both are available.
> 
> Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This will allow
> an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has
> less privileges than CAP_SYS_ADMIN.
> 
> Signed-off-by: Denis Semakin <denis.semakin@huawei.com>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  include/linux/capability.h      | 6 ++++++
>  security/integrity/ima/ima.h    | 6 ++++++
>  security/integrity/ima/ima_fs.c | 5 ++++-
>  3 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/capability.h b/include/linux/capability.h
> index 65efb74c3585..991579178f32 100644
> --- a/include/linux/capability.h
> +++ b/include/linux/capability.h
> @@ -270,6 +270,12 @@ static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns)
>  		ns_capable(ns, CAP_SYS_ADMIN);
>  }
>  
> +static inline bool mac_admin_ns_capable(struct user_namespace *ns)
> +{
> +	return ns_capable(ns, CAP_MAC_ADMIN) ||
> +		ns_capable(ns, CAP_SYS_ADMIN);

Do you care about audit warnings?  If the task has CAP_SYS_ADMIN but
not CAP_MAC_ADMIN, is it desirable that selinux_capable() will audit the
CAP_MAC_ADMIN failure?

> +}
> +
>  /* audit system wants to get cap info from files as well */
>  int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
>  			   const struct dentry *dentry,
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index fb6bd054d899..0057b1fd6c18 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -487,4 +487,10 @@ static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op,
>  #define	POLICY_FILE_FLAGS	S_IWUSR
>  #endif /* CONFIG_IMA_READ_POLICY */
>  
> +static inline
> +struct user_namespace *ima_user_ns_from_file(const struct file *filp)
> +{
> +	return file_inode(filp)->i_sb->s_user_ns;
> +}
> +
>  #endif /* __LINUX_IMA_H */
> diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
> index 89d3113ceda1..c41aa61b7393 100644
> --- a/security/integrity/ima/ima_fs.c
> +++ b/security/integrity/ima/ima_fs.c
> @@ -377,6 +377,9 @@ static const struct seq_operations ima_policy_seqops = {
>   */
>  static int ima_open_policy(struct inode *inode, struct file *filp)
>  {
> +#ifdef CONFIG_IMA_READ_POLICY
> +	struct user_namespace *user_ns = ima_user_ns_from_file(filp);
> +#endif
>  	struct ima_namespace *ns = &init_ima_ns;
>  
>  	if (!(filp->f_flags & O_WRONLY)) {
> @@ -385,7 +388,7 @@ static int ima_open_policy(struct inode *inode, struct file *filp)
>  #else
>  		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
>  			return -EACCES;
> -		if (!capable(CAP_SYS_ADMIN))
> +		if (!mac_admin_ns_capable(user_ns))
>  			return -EPERM;
>  		return seq_open(filp, &ima_policy_seqops);
>  #endif
> -- 
> 2.31.1
Stefan Berger Feb. 6, 2022, 5:20 p.m. UTC | #2 
On 2/5/22 00:58, Serge E. Hallyn wrote:
> On Tue, Feb 01, 2022 at 03:37:20PM -0500, Stefan Berger wrote:
>> Define mac_admin_ns_capable() as a wrapper for the combined ns_capable()
>> checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return
>> true on the check if either capability or both are available.
>>
>> Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This will allow
>> an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has
>> less privileges than CAP_SYS_ADMIN.
>>
>> Signed-off-by: Denis Semakin <denis.semakin@huawei.com>
>> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
>> ---
>>   include/linux/capability.h      | 6 ++++++
>>   security/integrity/ima/ima.h    | 6 ++++++
>>   security/integrity/ima/ima_fs.c | 5 ++++-
>>   3 files changed, 16 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/capability.h b/include/linux/capability.h
>> index 65efb74c3585..991579178f32 100644
>> --- a/include/linux/capability.h
>> +++ b/include/linux/capability.h
>> @@ -270,6 +270,12 @@ static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns)
>>   		ns_capable(ns, CAP_SYS_ADMIN);
>>   }
>>   
>> +static inline bool mac_admin_ns_capable(struct user_namespace *ns)
>> +{
>> +	return ns_capable(ns, CAP_MAC_ADMIN) ||
>> +		ns_capable(ns, CAP_SYS_ADMIN);
> Do you care about audit warnings?  If the task has CAP_SYS_ADMIN but
> not CAP_MAC_ADMIN, is it desirable that selinux_capable() will audit the
> CAP_MAC_ADMIN failure?

Good point.  I will switch both to ns_capable_noaudit() so that the user 
cannot provoke unnecessary audit message.

Thanks.

     Stefan

>
>> +}
>> +
>>   /* audit system wants to get cap info from files as well */
>>   int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
>>   			   const struct dentry *dentry,
>> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
>> index fb6bd054d899..0057b1fd6c18 100644
>> --- a/security/integrity/ima/ima.h
>> +++ b/security/integrity/ima/ima.h
>> @@ -487,4 +487,10 @@ static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op,
>>   #define	POLICY_FILE_FLAGS	S_IWUSR
>>   #endif /* CONFIG_IMA_READ_POLICY */
>>   
>> +static inline
>> +struct user_namespace *ima_user_ns_from_file(const struct file *filp)
>> +{
>> +	return file_inode(filp)->i_sb->s_user_ns;
>> +}
>> +
>>   #endif /* __LINUX_IMA_H */
>> diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
>> index 89d3113ceda1..c41aa61b7393 100644
>> --- a/security/integrity/ima/ima_fs.c
>> +++ b/security/integrity/ima/ima_fs.c
>> @@ -377,6 +377,9 @@ static const struct seq_operations ima_policy_seqops = {
>>    */
>>   static int ima_open_policy(struct inode *inode, struct file *filp)
>>   {
>> +#ifdef CONFIG_IMA_READ_POLICY
>> +	struct user_namespace *user_ns = ima_user_ns_from_file(filp);
>> +#endif
>>   	struct ima_namespace *ns = &init_ima_ns;
>>   
>>   	if (!(filp->f_flags & O_WRONLY)) {
>> @@ -385,7 +388,7 @@ static int ima_open_policy(struct inode *inode, struct file *filp)
>>   #else
>>   		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
>>   			return -EACCES;
>> -		if (!capable(CAP_SYS_ADMIN))
>> +		if (!mac_admin_ns_capable(user_ns))
>>   			return -EPERM;
>>   		return seq_open(filp, &ima_policy_seqops);
>>   #endif
>> -- 
>> 2.31.1
Stefan Berger Feb. 7, 2022, 6:43 p.m. UTC | #3 
On 2/6/22 12:20, Stefan Berger wrote:
>
> On 2/5/22 00:58, Serge E. Hallyn wrote:
>> On Tue, Feb 01, 2022 at 03:37:20PM -0500, Stefan Berger wrote:
>>> Define mac_admin_ns_capable() as a wrapper for the combined 
>>> ns_capable()
>>> checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return
>>> true on the check if either capability or both are available.
>>>
>>> Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This will 
>>> allow
>>> an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has
>>> less privileges than CAP_SYS_ADMIN.
>>>
>>> Signed-off-by: Denis Semakin <denis.semakin@huawei.com>
>>> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
>>> ---
>>>   include/linux/capability.h      | 6 ++++++
>>>   security/integrity/ima/ima.h    | 6 ++++++
>>>   security/integrity/ima/ima_fs.c | 5 ++++-
>>>   3 files changed, 16 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/capability.h b/include/linux/capability.h
>>> index 65efb74c3585..991579178f32 100644
>>> --- a/include/linux/capability.h
>>> +++ b/include/linux/capability.h
>>> @@ -270,6 +270,12 @@ static inline bool 
>>> checkpoint_restore_ns_capable(struct user_namespace *ns)
>>>           ns_capable(ns, CAP_SYS_ADMIN);
>>>   }
>>>   +static inline bool mac_admin_ns_capable(struct user_namespace *ns)
>>> +{
>>> +    return ns_capable(ns, CAP_MAC_ADMIN) ||
>>> +        ns_capable(ns, CAP_SYS_ADMIN);
>> Do you care about audit warnings?  If the task has CAP_SYS_ADMIN but
>> not CAP_MAC_ADMIN, is it desirable that selinux_capable() will audit the
>> CAP_MAC_ADMIN failure?
>
> Good point.  I will switch both to ns_capable_noaudit() so that the 
> user cannot provoke unnecessary audit message.

Actually,  I will only change the MAC_ADMIN to not do auditing and not 
change the auditing behavior related to SYS_ADMIN.

    Stefan
Serge E. Hallyn Feb. 23, 2022, 5:51 p.m. UTC | #4 
On Mon, Feb 07, 2022 at 01:43:31PM -0500, Stefan Berger wrote:
> 
> On 2/6/22 12:20, Stefan Berger wrote:
> > 
> > On 2/5/22 00:58, Serge E. Hallyn wrote:
> > > On Tue, Feb 01, 2022 at 03:37:20PM -0500, Stefan Berger wrote:
> > > > Define mac_admin_ns_capable() as a wrapper for the combined
> > > > ns_capable()
> > > > checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return
> > > > true on the check if either capability or both are available.
> > > > 
> > > > Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This
> > > > will allow
> > > > an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has
> > > > less privileges than CAP_SYS_ADMIN.
> > > > 
> > > > Signed-off-by: Denis Semakin <denis.semakin@huawei.com>
> > > > Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> > > > ---
> > > >   include/linux/capability.h      | 6 ++++++
> > > >   security/integrity/ima/ima.h    | 6 ++++++
> > > >   security/integrity/ima/ima_fs.c | 5 ++++-
> > > >   3 files changed, 16 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/include/linux/capability.h b/include/linux/capability.h
> > > > index 65efb74c3585..991579178f32 100644
> > > > --- a/include/linux/capability.h
> > > > +++ b/include/linux/capability.h
> > > > @@ -270,6 +270,12 @@ static inline bool
> > > > checkpoint_restore_ns_capable(struct user_namespace *ns)
> > > >           ns_capable(ns, CAP_SYS_ADMIN);
> > > >   }
> > > >   +static inline bool mac_admin_ns_capable(struct user_namespace *ns)
> > > > +{
> > > > +    return ns_capable(ns, CAP_MAC_ADMIN) ||
> > > > +        ns_capable(ns, CAP_SYS_ADMIN);
> > > Do you care about audit warnings?  If the task has CAP_SYS_ADMIN but
> > > not CAP_MAC_ADMIN, is it desirable that selinux_capable() will audit the
> > > CAP_MAC_ADMIN failure?
> > 
> > Good point.  I will switch both to ns_capable_noaudit() so that the user
> > cannot provoke unnecessary audit message.
> 
> Actually,  I will only change the MAC_ADMIN to not do auditing and not
> change the auditing behavior related to SYS_ADMIN.

Right, that makes the most sense.
diff mbox series

Patch

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 65efb74c3585..991579178f32 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -270,6 +270,12 @@  static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns)
 		ns_capable(ns, CAP_SYS_ADMIN);
 }
 
+static inline bool mac_admin_ns_capable(struct user_namespace *ns)
+{
+	return ns_capable(ns, CAP_MAC_ADMIN) ||
+		ns_capable(ns, CAP_SYS_ADMIN);
+}
+
 /* audit system wants to get cap info from files as well */
 int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
 			   const struct dentry *dentry,
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index fb6bd054d899..0057b1fd6c18 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -487,4 +487,10 @@  static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op,
 #define	POLICY_FILE_FLAGS	S_IWUSR
 #endif /* CONFIG_IMA_READ_POLICY */
 
+static inline
+struct user_namespace *ima_user_ns_from_file(const struct file *filp)
+{
+	return file_inode(filp)->i_sb->s_user_ns;
+}
+
 #endif /* __LINUX_IMA_H */
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 89d3113ceda1..c41aa61b7393 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -377,6 +377,9 @@  static const struct seq_operations ima_policy_seqops = {
  */
 static int ima_open_policy(struct inode *inode, struct file *filp)
 {
+#ifdef CONFIG_IMA_READ_POLICY
+	struct user_namespace *user_ns = ima_user_ns_from_file(filp);
+#endif
 	struct ima_namespace *ns = &init_ima_ns;
 
 	if (!(filp->f_flags & O_WRONLY)) {
@@ -385,7 +388,7 @@  static int ima_open_policy(struct inode *inode, struct file *filp)
 #else
 		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 			return -EACCES;
-		if (!capable(CAP_SYS_ADMIN))
+		if (!mac_admin_ns_capable(user_ns))
 			return -EPERM;
 		return seq_open(filp, &ima_policy_seqops);
 #endif