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 <[email protected]>
Signed-off-by: Stefan Berger <[email protected]>
---
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);
+}
+
/* 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
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 <[email protected]>
> Signed-off-by: Stefan Berger <[email protected]>
> ---
> 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
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 <[email protected]>
>> Signed-off-by: Stefan Berger <[email protected]>
>> ---
>> 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
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 <[email protected]>
>>> Signed-off-by: Stefan Berger <[email protected]>
>>> ---
>>> 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
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 <[email protected]>
> > > > Signed-off-by: Stefan Berger <[email protected]>
> > > > ---
> > > > ? 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.