On Tue, Feb 4, 2020 at 7:39 PM Richard Guy Briggs [off-list ref] wrote:

On 2020-01-22 16:29, Paul Moore wrote:

quoted

On Tue, Dec 31, 2019 at 2:51 PM Richard Guy Briggs [off-list ref] wrote:

quoted

Provide a mechanism similar to CAP_AUDIT_CONTROL to explicitly give a
process in a non-init user namespace the capability to set audit
container identifiers.

Provide /proc/$PID/audit_capcontid interface to capcontid.
Valid values are: 1==enabled, 0==disabled

It would be good to be more explicit about "enabled" and "disabled" in
the commit description.  For example, which setting allows the target
task to set audit container IDs of it's children processes?

Ok...

quoted

quoted

Report this action in message type AUDIT_SET_CAPCONTID 1022 with fields
opid= capcontid= old-capcontid=

Signed-off-by: Richard Guy Briggs <redacted>
---
 fs/proc/base.c             | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/audit.h      | 14 ++++++++++++
 include/uapi/linux/audit.h |  1 +
 kernel/audit.c             | 35 +++++++++++++++++++++++++++++
 4 files changed, 105 insertions(+)

...

quoted

quoted

diff --git a/kernel/audit.c b/kernel/audit.c
index 1287f0b63757..1c22dd084ae8 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c

@@ -2698,6 +2698,41 @@ static bool audit_contid_isowner(struct task_struct *tsk)
        return false;
 }

+int audit_set_capcontid(struct task_struct *task, u32 enable)
+{
+       u32 oldcapcontid;
+       int rc = 0;
+       struct audit_buffer *ab;
+
+       if (!task->audit)
+               return -ENOPROTOOPT;
+       oldcapcontid = audit_get_capcontid(task);
+       /* if task is not descendant, block */
+       if (task == current)
+               rc = -EBADSLT;
+       else if (!task_is_descendant(current, task))
+               rc = -EXDEV;

See my previous comments about error code sanity.

I'll go with EXDEV.

quoted

quoted

+       else if (current_user_ns() == &init_user_ns) {
+               if (!capable(CAP_AUDIT_CONTROL) && !audit_get_capcontid(current))
+                       rc = -EPERM;

I think we just want to use ns_capable() in the context of the current
userns to check CAP_AUDIT_CONTROL, yes?  Something like this ...

I thought we had firmly established in previous discussion that
CAP_AUDIT_CONTROL in anything other than init_user_ns was completely irrelevant
and untrustable.

In the case of a container with multiple users, and multiple
applications, one being a nested orchestrator, it seems relevant to
allow that container to control which of it's processes are able to
exercise CAP_AUDIT_CONTROL.  Granted, we still want to control it
within the overall host, e.g. the container in question must be
allowed to run a nested orchestrator, but allowing the container
itself to provide it's own granularity seems like the right thing to
do.

quoted

  if (current_user_ns() != &init_user_ns) {
    if (!ns_capable(CAP_AUDIT_CONTROL) || !audit_get_capcontid())
      rc = -EPERM;
  } else if (!capable(CAP_AUDIT_CONTROL))
    rc = -EPERM;

-- 
paul moore
www.paul-moore.com