[PATCH v4 6/6] landlock: Document LANDLOCK_SCOPED_SIGNAL

[Mickaël Salaün]

On Fri, Sep 06, 2024 at 03:30:08PM -0600, Tahera Fahimi wrote:
> Improving Landlock ABI version 6 to support signal scoping with
> LANDLOCK_SCOPED_SIGNAL.
> 
> Signed-off-by: Tahera Fahimi <fahimitahera at gmail.com>
> ---
> v3:
> - update date
> ---
>  Documentation/userspace-api/landlock.rst | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
> index c3b87755e98d..c694e9fe36fc 100644
> --- a/Documentation/userspace-api/landlock.rst
> +++ b/Documentation/userspace-api/landlock.rst
> @@ -82,7 +82,8 @@ to be explicit about the denied-by-default access rights.
>              LANDLOCK_ACCESS_NET_BIND_TCP |
>              LANDLOCK_ACCESS_NET_CONNECT_TCP,
>          .scoped =
> -            LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET,
> +            LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET |
> +            LANDLOCK_SCOPED_SIGNAL,
>      };
>  
>  Because we may not know on which kernel version an application will be
> @@ -123,7 +124,8 @@ version, and only use the available subset of access rights:
>          ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
>      case 5:
>          /* Removes LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET for ABI < 6 */
> -        ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
> +        ruleset_attr.scoped &= ~(LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET |
> +                                 LANDLOCK_SCOPED_SIGNAL);
>      }
>  
>  This enables to create an inclusive ruleset that will contain our rules.
> @@ -320,11 +322,15 @@ explicitly scoped for a set of actions by specifying it on a ruleset.
>  For example, if a sandboxed process should not be able to
>  :manpage:`connect(2)` to a non-sandboxed process through abstract
>  :manpage:`unix(7)` sockets, we can specify such restriction with
> -``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET``.
> +``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET``. Moreover, if a sandboxed
> +process should not be able to send a signal to a non-sandboxed process,
> +we can specify this restriction with ``LANDLOCK_SCOPED_SIGNAL``.
>  
>  A sandboxed process can connect to a non-sandboxed process when its
>  domain is not scoped. If a process's domain is scoped, it can only
>  connect to sockets created by processes in the same scoped domain.
> +Moreover, If a process is scoped to send signal to a non-scoped process,
> +it can only send signals to processes in the same scoped domain.
>  
>  A connected datagram socket behaves like a stream socket when its domain
>  is scoped, meaning if the domain is scoped after the socket is connected
> @@ -575,12 +581,14 @@ earlier ABI.
>  Starting with the Landlock ABI version 5, it is possible to restrict the use of
>  :manpage:`ioctl(2)` using the new ``LANDLOCK_ACCESS_FS_IOCTL_DEV`` right.
>  
> -Abstract UNIX sockets Restriction  (ABI < 6)
> ---------------------------------------------
> +Abstract Unix sockets and Signal Restriction  (ABI < 6)
> +-------------------------------------------------------

I created a dedicated section instead of merging both.

>  
> +<<<<<<< current

I fixed that.

>  With ABI version 6, it is possible to restrict connection to an abstract
> -Unix socket through ``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET``, thanks to
> -the ``scoped`` ruleset attribute.
> +:manpage:`unix(7)` socket through
> +``LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET`` and sending signal through
> +``LANDLOCK_SCOPED_SIGNAL``, thanks to the ``scoped`` ruleset attribute.

I cleaned up this fix that should be part of the other series.

>  
>  .. _kernel_support:
>  
> -- 
> 2.34.1
> 
>