On Fri, Apr 17, 2020 at 6:38 PM Richard Haines
<richard_c_haines@xxxxxxxxxxxxxx> wrote:
> Kernel 5.7 introduced the watch_queue service that allows watching for
> key changes. This requires key { view } permission, therefore check if
> allowed or not.
>
> Note that the keyctl_watch_key() function is not yet built into the
> keyutils library, therefore a syscall() is used.
>
> Signed-off-by: Richard Haines <richard_c_haines@xxxxxxxxxxxxxx>
OK, so I tried to build kernel RPMs(*) from the linux-next tree and
try out this patch, but I ran into a few problems:
1. <linux/watch_queue.h> includes <linux/fcntl.h>, which conflicts
with glibc's <sys/fcntl.h>. This will maybe get fixed in glibc/kernel
eventually, but I can't apply the patch as-is (maybe we can #define
_LINUX_FCNTL_H before including <linux/watch_queue.h> as a temporary
workaround?).
2. Even when I got the test program to build, the test failed. I ran
out of time to dig further, but it may be due to the issues I spotted
later in the test policy (see below).
(*) I wanted to try out the new Fedora's kernel build machinery, so I
burnt too much time on this... but I now have a semi-automated way to
build linux-next kernels as RPMs, which might come in handy in the
future :)
> ---
> defconfig | 5 ++
> policy/Makefile | 2 +-
> policy/test_watchkey.te | 34 ++++++++++++
> tests/Makefile | 4 ++
> tests/watchkey/.gitignore | 1 +
> tests/watchkey/Makefile | 7 +++
> tests/watchkey/test | 29 ++++++++++
> tests/watchkey/watchkey.c | 113 ++++++++++++++++++++++++++++++++++++++
> 8 files changed, 194 insertions(+), 1 deletion(-)
> create mode 100644 policy/test_watchkey.te
> create mode 100644 tests/watchkey/.gitignore
> create mode 100644 tests/watchkey/Makefile
> create mode 100755 tests/watchkey/test
> create mode 100644 tests/watchkey/watchkey.c
>
> diff --git a/defconfig b/defconfig
> index 0574f1d..9afbc2f 100644
> --- a/defconfig
> +++ b/defconfig
> @@ -78,3 +78,8 @@ CONFIG_KEY_DH_OPERATIONS=y
> # Test key management socket.
> # This is not required for SELinux operation itself.
> CONFIG_NET_KEY=m
> +
> +# watch_queue for key changes.
> +# They are not required for SELinux operation itself.
> +CONFIG_WATCH_QUEUE=y
> +CONFIG_KEY_NOTIFICATIONS=y
> diff --git a/policy/Makefile b/policy/Makefile
> index 87b2856..b3f5e3d 100644
> --- a/policy/Makefile
> +++ b/policy/Makefile
> @@ -86,7 +86,7 @@ TARGETS += test_bpf.te test_fdreceive_bpf.te test_binder_bpf.te
> endif
>
> ifeq ($(shell grep -q all_key_perms $(POLDEV)/include/support/all_perms.spt && echo true),true)
> -TARGETS += test_keys.te
> +TARGETS += test_keys.te test_watchkey.te
> endif
>
> ifeq ($(shell grep -q all_file_perms.*watch $(POLDEV)/include/support/all_perms.spt && echo true),true)
> diff --git a/policy/test_watchkey.te b/policy/test_watchkey.te
> new file mode 100644
> index 0000000..e1d4c78
> --- /dev/null
> +++ b/policy/test_watchkey.te
> @@ -0,0 +1,34 @@
> +#
> +######### Check watch_queue for key changes policy module ##########
> +#
> +attribute watchkeydomain;
> +
> +################# Allow watch_queue key { view } ##########################
> +type test_watchkey_t;
> +domain_type(test_watchkey_t)
> +unconfined_runs_test(test_watchkey_t)
> +typeattribute test_watchkey_t testdomain;
> +typeattribute test_watchkey_t keydomain;
You declare attribute "watchkeydomain" above and later call some
interfaces on it, but assign all the types to "keydomain". I assume
you meant to assign them to "watchkeydomain"?
> +
> +allow test_watchkey_t self:capability { ipc_lock };
> +allow test_watchkey_t device_t:chr_file { ioctl open read write };
> +allow test_watchkey_t self:key { view };
> +allow_map(test_watchkey_t, device_t, chr_file)
> +
> +################# Deny watch_queue key { view } ##########################
> +type test_watchkey_no_view_t;
> +domain_type(test_watchkey_no_view_t)
> +unconfined_runs_test(test_watchkey_no_view_t)
> +typeattribute test_watchkey_no_view_t testdomain;
> +typeattribute test_watchkey_no_view_t keydomain;
> +
> +allow test_watchkey_no_view_t self:capability { ipc_lock };
> +allow test_watchkey_no_view_t device_t:chr_file { ioctl open read write };
> +neverallow test_watchkey_no_view_t self:key { view };
> +allow_map(test_watchkey_no_view_t, device_t, chr_file)
> +
> +#
> +########### Allow these domains to be entered from sysadm domain ############
> +#
> +miscfiles_domain_entry_test_files(watchkeydomain)
> +userdom_sysadm_entry_spec_domtrans_to(watchkeydomain)
[...]
--
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.
