Re: [PATCH 0/7 v21] LSM: Multiple concurrent LSMs

[Stephen Smalley]

On 03/09/2015 09:13 PM, Casey Schaufler wrote:
> Subject: [PATCH 0/7 v21] LSM: Multiple concurrent LSMs
> 
> Replace the current ad hoc stacking of the capabilities
> and Yama security modules with a generalized stacking scheme. 
> 
> The old structure had a single set of module hooks contained
> in a security_operations structure. This structure was initialized
> with a set of stubs referred to as the "capabilities" module.
> In fact only a few of these hooks actually did anything useful.
> When a module replaced the capabilities module the entries
> supplied replaced those from the capabilities module. The
> new hook was expected to call the replaced capability code
> if "stacking" was desired, which it usually was. Yama stacking
> is done by ifdefs in the security infrastructure.
> 
> The new structure provides a list of module hooks for each
> interface. The non-trivial functions from the capabilities
> module are add to the list first. If Yama stacking is configured
> the Yama functions are added next. If a module is specified as
> the "default" module, or is specified on the command line, it
> is added next.
> 
> Functions are called in the order added to the list. The
> security interfaces stop when a function indicates an access
> denial. It is possible for a list to be empty. That is treated
> as a success in most cases.
> 
> Each security module provides an array of function list entries.
> This is initialized with the information needed to properly add
> the entries to the function lists.
> 
> The sheer size of this patch set is somewhat frightening. This
> is an artifact of the number of security interfaces involved and
> except for a few cases the changes are mechanical in nature.
> Except for the removal of some information specific to the security
> module infrastructure itself, the change is transparent to the rest
> of the kernel.
> 
> This is going to break out-of-tree security modules. It's easy to
> update a module to the new scheme, and I'd be happy to do it for
> any module I know about, but if it isn't in the tree, I don't know
> about it.
> 
> The stacking of modules that use the security blob pointers
> cred->security, inode->i_security, etc has not been addressed.
> That is future work with a delightful set of issues. 
> 
> This patch set is based on James Morris' security-next tree,
> which is itself based on Linus' 4.0-rc1. It reflects the 11
> patches of v20.
> 
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>

Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx>

Passes the selinux-testsuite with SELINUX alone or
SELINUX+YAMA+YAMA_STACKED.

> ---
>  include/linux/lsm_hooks.h  | 1872 ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/security.h   | 1613 +-------------------------------------
>  security/Makefile          |    2 +-
>  security/apparmor/domain.c |    4 +-
>  security/apparmor/lsm.c    |  131 ++--
>  security/capability.c      | 1164 ---------------------------
>  security/commoncap.c       |   36 +-
>  security/security.c        |  979 ++++++++++++++++-------
>  security/selinux/hooks.c   |  477 +++++------
>  security/smack/smack.h     |    4 +-
>  security/smack/smack_lsm.c |  305 ++++----
>  security/smack/smackfs.c   |    2 +-
>  security/tomoyo/tomoyo.c   |   72 +-
>  security/yama/yama_lsm.c   |   60 +-
>  14 files changed, 3071 insertions(+), 3650 deletions(-)
> 
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