Re: [PATCH v10 00/25] LSM: Module stacking for AppArmor

[Stephen Smalley <sds@tycho.nsa.gov>]

On 10/24/19 4:52 PM, Casey Schaufler wrote:
> This patchset provides the changes required for
> the AppArmor security module to stack safely with any other.
> 
> v10: Ask the security modules if the display can be changed.
> 
> v9: There is no version 9
> 
> v8: Incorporate feedback from v7
>      - Minor clean-up in display value management
>      - refactor "compound" context creation to use a common
>        append_ctx() function.
> 
> v7: Incorporate feedback from v6
>      - Make setting the display a privileged operation. The
>        availability of compound contexts reduces the need for
>        setting the display.
> 
> v6: Incorporate feedback from v5
>      - Add subj_<lsm>= and obj_<lsm>= fields to audit records
>      - Add /proc/.../attr/context to get the full context in
>        lsmname\0value\0... format as suggested by Simon McVittie
>      - Add SO_PEERCONTEXT for getsockopt() to get the full context
>        in the same format, also suggested by Simon McVittie.
>      - Add /sys/kernel/security/lsm_display_default to provide
>        the display default value.
> 
> v5: Incorporate feedback from v4
>      - Initialize the lsmcontext in security_secid_to_secctx()
>      - Clear the lsmcontext in all security_release_secctx() cases
>      - Don't use the "display" on strictly internal context
>        interfaces.
>      - The SELinux binder hooks check for cases where the context
>        "display" isn't compatible with SELinux.
> 
> v4: Incorporate feedback from v3
>      - Mark new lsm_<blob>_alloc functions static
>      - Replace the lsm and slot fields of the security_hook_list
>        with a pointer to a LSM allocated lsm_id structure. The
>        LSM identifies if it needs a slot explicitly. Use the
>        lsm_id rather than make security_add_hooks return the
>        slot value.
>      - Validate slot values used in security.c
>      - Reworked the "display" process attribute handling so that
>        it works right and doesn't use goofy list processing.
>      - fix display value check in dentry_init_security
>      - Replace audit_log of secids with '?' instead of deleting
>        the audit log
> 
> v3: Incorporate feedback from v2
>      - Make lsmblob parameter and variable names more
>        meaningful, changing "le" and "l" to "blob".
>      - Improve consistency of constant naming.
>      - Do more sanity checking during LSM initialization.
>      - Be a bit clearer about what is temporary scaffolding.
>      - Rather than clutter security_getpeersec_dgram with
>        otherwise unnecessary checks remove the apparmor
>        stub, which does nothing useful.
> 
> Patche 0001 moves management of the sock security blob from the individual
> modules to the infrastructure.
> 
> Patches 0002-0012 replace system use of a "secid" with
> a structure "lsmblob" containing information from the
> security modules to be held and reused later. At this
> point lsmblob contains an array of u32 secids, one "slot"
> for each of the security modules compiled into the
> kernel that used secids. A "slot" is allocated when
> a security module requests one.
> The infrastructure is changed to use the slot number
> to pass the correct secid to or from the security module
> hooks.
> 
> It is important that the lsmblob be a fixed size entity
> that does not have to be allocated. Several of the places
> where it is used would have performance and/or locking
> issues with dynamic allocation.
> 
> Patch 0013 provides a mechanism for a process to
> identify which security module's hooks should be used
> when displaying or converting a security context string.
> A new interface /proc/.../attr/display contains the name
> of the security module to show. Reading from this file
> will present the name of the module, while writing to
> it will set the value. Only names of active security
> modules are accepted. Internally, the name is translated
> to the appropriate "slot" number for the module which
> is then stored in the task security blob. Setting the
> display requires that all modules using the /proc interfaces
> allow the transition.
> 
> Patch 0014 Starts the process of changing how a security
> context is represented. Since it is possible for a
> security context to have been generated by more than one
> security module it is now necessary to note which module
> created a security context so that the correct "release"
> hook can be called. There are several places where the
> module that created a security context cannot be inferred.
> 
> This is achieved by introducing a "lsmcontext" structure
> which contains the context string, its length and the
> "slot" number of the security module that created it.
> The security_release_secctx() interface is changed,
> replacing the (string,len) pointer pair with a lsmcontext
> pointer.
> 
> Patches 0015-0017 convert the security interfaces from
> (string,len) pointer pairs to a lsmcontext pointer.
> The slot number identifying the creating module is
> added by the infrastructure. Where the security context
> is stored for extended periods the data type is changed.
> 
> The Netlabel code is converted to save lsmblob structures
> instead of secids in Patches 0018-0019.
> 
> Patch 0020 adds checks to the binder hooks which verify
> that if both ends of a transaction use the same "display".
> 
> Patches 0021-0022 add addition data to the audit records
> to identify the LSM specific data for all active modules.
> 
> Patches 0023-0024 add new interfaces for getting the
> compound security contexts.
> 
> Finally, with all interference on the AppArmor hooks
> removed, Patch 0025 removes the exclusive bit from
> AppArmor. An unnecessary stub hook was also removed.
> 
> The Ubuntu project is using an earlier version of
> this patchset in their distribution to enable stacking
> for containers.
> 
> Performance measurements to date have the change
> within the "noise". The sockperf and dbench results
> are on the order of 0.2% to 0.8% difference, with
> better performance being as common as worse. The
> benchmarks were run with AppArmor and Smack on Ubuntu.
> 
> https://github.com/cschaufler/lsm-stacking.git#stack-5.2-v10-apparmor

Can you re-base on something more recent than v5.1-rc2 (that's the base 
for that branch currently)?
At present it won't even boot for me on modern Fedora.  Two key missing 
commits are:

e33c1b9923775d17ad246946fe67fcb9be288677 ("apparmor: Restore Y/N in /sys 
for apparmor's "enabled") - without this, dbus falls over (or at least 
dbus-broker in Fedora)

169ce0c081cd85f78388bb6c1638c1ad7b81bde7 ("selinux: fix residual uses of 
current_security() for the SELinux blob") - without this, selinux ends 
up dereferencing something other than its own security blob after these 
patches

> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>   arch/alpha/include/uapi/asm/socket.h    |   1 +
>   arch/mips/include/uapi/asm/socket.h     |   1 +
>   arch/parisc/include/uapi/asm/socket.h   |   1 +
>   arch/sparc/include/uapi/asm/socket.h    |   1 +
>   drivers/android/binder.c                |  24 +-
>   fs/kernfs/dir.c                         |   5 +-
>   fs/kernfs/inode.c                       |  35 +-
>   fs/kernfs/kernfs-internal.h             |   3 +-
>   fs/nfs/nfs4proc.c                       |  22 +-
>   fs/nfsd/nfs4xdr.c                       |  20 +-
>   fs/proc/base.c                          |   2 +
>   include/linux/audit.h                   |   1 +
>   include/linux/cred.h                    |   3 +-
>   include/linux/lsm_hooks.h               |  37 +-
>   include/linux/security.h                | 175 ++++++++--
>   include/net/af_unix.h                   |   2 +-
>   include/net/netlabel.h                  |   8 +-
>   include/net/scm.h                       |  15 +-
>   include/uapi/asm-generic/socket.h       |   1 +
>   kernel/audit.c                          |  70 +++-
>   kernel/audit.h                          |   9 +-
>   kernel/audit_fsnotify.c                 |   1 +
>   kernel/auditfilter.c                    |  10 +-
>   kernel/auditsc.c                        | 129 ++++---
>   kernel/cred.c                           |  12 +-
>   net/core/sock.c                         |   7 +-
>   net/ipv4/cipso_ipv4.c                   |   6 +-
>   net/ipv4/ip_sockglue.c                  |  12 +-
>   net/netfilter/nf_conntrack_netlink.c    |  20 +-
>   net/netfilter/nf_conntrack_standalone.c |  11 +-
>   net/netfilter/nfnetlink_queue.c         |  26 +-
>   net/netfilter/nft_meta.c                |  13 +-
>   net/netfilter/xt_SECMARK.c              |   5 +-
>   net/netlabel/netlabel_kapi.c            |   6 +-
>   net/netlabel/netlabel_unlabeled.c       |  97 +++---
>   net/netlabel/netlabel_unlabeled.h       |   2 +-
>   net/netlabel/netlabel_user.c            |  13 +-
>   net/netlabel/netlabel_user.h            |   6 +-
>   net/unix/af_unix.c                      |   6 +-
>   net/xfrm/xfrm_policy.c                  |   2 +
>   net/xfrm/xfrm_state.c                   |   2 +
>   security/apparmor/include/apparmor.h    |   3 +-
>   security/apparmor/include/net.h         |   6 +-
>   security/apparmor/lsm.c                 | 121 ++++---
>   security/commoncap.c                    |   7 +-
>   security/integrity/ima/ima.h            |  14 +-
>   security/integrity/ima/ima_api.c        |  10 +-
>   security/integrity/ima/ima_appraise.c   |   6 +-
>   security/integrity/ima/ima_main.c       |  36 +-
>   security/integrity/ima/ima_policy.c     |  19 +-
>   security/integrity/integrity_audit.c    |   1 +
>   security/loadpin/loadpin.c              |   8 +-
>   security/safesetid/lsm.c                |   8 +-
>   security/security.c                     | 586 +++++++++++++++++++++++++++++---
>   security/selinux/hooks.c                | 109 +++---
>   security/selinux/include/classmap.h     |   2 +-
>   security/selinux/include/objsec.h       |   5 +
>   security/selinux/include/security.h     |   1 +
>   security/selinux/netlabel.c             |  25 +-
>   security/selinux/ss/services.c          |   4 +-
>   security/smack/smack.h                  |   6 +
>   security/smack/smack_lsm.c              | 124 ++++---
>   security/smack/smack_netfilter.c        |   8 +-
>   security/smack/smackfs.c                |  10 +-
>   security/tomoyo/tomoyo.c                |   8 +-
>   security/yama/yama_lsm.c                |   7 +-
>   66 files changed, 1376 insertions(+), 580 deletions(-)
>