[PATCH v2] nbd/server: Add --selinux-label option

[PATCH v2] nbd/server: Add --selinux-label option

[Richard W.M. Jones]

v1 was here:
https://lists.nongnu.org/archive/html/qemu-block/2021-07/threads.html#00713

v2 adds the changes to CI docker files as suggested by
Dan Berrange in his review.

Rich.

[PATCH v2] nbd/server: Add --selinux-label option

[Richard W.M. Jones]

Under SELinux, Unix domain sockets have two labels.  One is on the
disk and can be set with commands such as chcon(1).  There is a
different label stored in memory (called the process label).  This can
only be set by the process creating the socket.  When using SELinux +
SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
you must set both labels correctly first.

For qemu-nbd the options to set the second label are awkward.  You can
create the socket in a wrapper program and then exec into qemu-nbd.
Or you could try something with LD_PRELOAD.

This commit adds the ability to set the label straightforwardly on the
command line, via the new --selinux-label flag.  (The name of the flag
is the same as the equivalent nbdkit option.)

A worked example showing how to use the new option can be found in
this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
 configure                                     |  9 ++++-
 meson.build                                   | 10 +++++-
 meson_options.txt                             |  3 ++
 qemu-nbd.c                                    | 33 +++++++++++++++++++
 tests/docker/dockerfiles/centos8.docker       |  1 +
 tests/docker/dockerfiles/fedora.docker        |  1 +
 tests/docker/dockerfiles/opensuse-leap.docker |  1 +
 tests/docker/dockerfiles/ubuntu1804.docker    |  1 +
 tests/docker/dockerfiles/ubuntu2004.docker    |  1 +
 9 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index b5965b159f..7e04bd485f 100755
--- a/configure
+++ b/configure
@@ -443,6 +443,7 @@ fuse="auto"
 fuse_lseek="auto"
 multiprocess="auto"
 slirp_smbd="$default_feature"
+selinux="auto"
 
 malloc_trim="auto"
 gio="$default_feature"
@@ -1578,6 +1579,10 @@ for opt do
   ;;
   --disable-slirp-smbd) slirp_smbd=no
   ;;
+  --enable-selinux) selinux="enabled"
+  ;;
+  --disable-selinux) selinux="disabled"
+  ;;
   *)
       echo "ERROR: unknown option $opt"
       echo "Try '$0 --help' for more information"
@@ -1965,6 +1970,7 @@ disabled with --disable-FEATURE, default is enabled if available
   multiprocess    Out of process device emulation support
   gio             libgio support
   slirp-smbd      use smbd (at path --smbd=*) in slirp networking
+  selinux         SELinux support in qemu-nbd
 
 NOTE: The object files are built at the place where configure is launched
 EOF
@@ -5220,7 +5226,8 @@ if test "$skip_meson" = no; then
         -Dattr=$attr -Ddefault_devices=$default_devices -Dvirglrenderer=$virglrenderer \
         -Ddocs=$docs -Dsphinx_build=$sphinx_build -Dinstall_blobs=$blobs \
         -Dvhost_user_blk_server=$vhost_user_blk_server -Dmultiprocess=$multiprocess \
-        -Dfuse=$fuse -Dfuse_lseek=$fuse_lseek -Dguest_agent_msi=$guest_agent_msi -Dbpf=$bpf\
+        -Dfuse=$fuse -Dfuse_lseek=$fuse_lseek -Dguest_agent_msi=$guest_agent_msi -Dbpf=$bpf \
+        -Dselinux=$selinux \
         $(if test "$default_features" = no; then echo "-Dauto_features=disabled"; fi) \
 	-Dtcg_interpreter=$tcg_interpreter \
         $cross_arg \
diff --git a/meson.build b/meson.build
index 2f377098d7..2d7206233e 100644
--- a/meson.build
+++ b/meson.build
@@ -1064,6 +1064,11 @@ keyutils = dependency('libkeyutils', required: false,
 
 has_gettid = cc.has_function('gettid')
 
+# libselinux
+selinux = dependency('libselinux',
+                     required: get_option('selinux'),
+                     method: 'pkg-config', kwargs: static_kwargs)
+
 # Malloc tests
 
 malloc = []
@@ -1291,6 +1296,7 @@ config_host_data.set('CONFIG_FUSE', fuse.found())
 config_host_data.set('CONFIG_FUSE_LSEEK', fuse_lseek.found())
 config_host_data.set('CONFIG_X11', x11.found())
 config_host_data.set('CONFIG_CFI', get_option('cfi'))
+config_host_data.set('CONFIG_SELINUX', selinux.found())
 config_host_data.set('QEMU_VERSION', '"@0@"'.format(meson.project_version()))
 config_host_data.set('QEMU_VERSION_MAJOR', meson.project_version().split('.')[0])
 config_host_data.set('QEMU_VERSION_MINOR', meson.project_version().split('.')[1])
@@ -2739,7 +2745,8 @@ if have_tools
   qemu_io = executable('qemu-io', files('qemu-io.c'),
              dependencies: [block, qemuutil], install: true)
   qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
-               dependencies: [blockdev, qemuutil, gnutls], install: true)
+               dependencies: [blockdev, qemuutil, gnutls, selinux],
+               install: true)
 
   subdir('storage-daemon')
   subdir('contrib/rdmacm-mux')
@@ -3104,6 +3111,7 @@ summary_info += {'libpmem support':   libpmem.found()}
 summary_info += {'libdaxctl support': libdaxctl.found()}
 summary_info += {'libudev':           libudev.found()}
 summary_info += {'FUSE lseek':        fuse_lseek.found()}
+summary_info += {'selinux':           selinux.found()}
 summary(summary_info, bool_yn: true, section: 'Dependencies')
 
 if not supported_cpus.contains(cpu)
diff --git a/meson_options.txt b/meson_options.txt
index a9a9b8f4c6..a5938500a3 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -155,3 +155,6 @@ option('slirp', type: 'combo', value: 'auto',
 option('fdt', type: 'combo', value: 'auto',
        choices: ['disabled', 'enabled', 'auto', 'system', 'internal'],
        description: 'Whether and how to find the libfdt library')
+
+option('selinux', type: 'feature', value: 'auto',
+       description: 'SELinux support in qemu-nbd')
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 26ffbf15af..003ba2492e 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -47,6 +47,10 @@
 #include "trace/control.h"
 #include "qemu-version.h"
 
+#ifdef CONFIG_SELINUX
+#include <selinux/selinux.h>
+#endif
+
 #ifdef __linux__
 #define HAVE_NBD_DEVICE 1
 #else
@@ -64,6 +68,7 @@
 #define QEMU_NBD_OPT_FORK          263
 #define QEMU_NBD_OPT_TLSAUTHZ      264
 #define QEMU_NBD_OPT_PID_FILE      265
+#define QEMU_NBD_OPT_SELINUX_LABEL 266
 
 #define MBR_SIZE 512
 
@@ -116,6 +121,9 @@ static void usage(const char *name)
 "  --fork                    fork off the server process and exit the parent\n"
 "                            once the server is running\n"
 "  --pid-file=PATH           store the server's process ID in the given file\n"
+#ifdef CONFIG_SELINUX
+"  --selinux-label=LABEL     set SELinux process label on listening socket\n"
+#endif
 #if HAVE_NBD_DEVICE
 "\n"
 "Kernel NBD client support:\n"
@@ -532,6 +540,8 @@ int main(int argc, char **argv)
         { "trace", required_argument, NULL, 'T' },
         { "fork", no_argument, NULL, QEMU_NBD_OPT_FORK },
         { "pid-file", required_argument, NULL, QEMU_NBD_OPT_PID_FILE },
+        { "selinux-label", required_argument, NULL,
+          QEMU_NBD_OPT_SELINUX_LABEL },
         { NULL, 0, NULL, 0 }
     };
     int ch;
@@ -558,6 +568,7 @@ int main(int argc, char **argv)
     int old_stderr = -1;
     unsigned socket_activation;
     const char *pid_file_name = NULL;
+    const char *selinux_label = NULL;
     BlockExportOptions *export_opts;
 
 #ifdef CONFIG_POSIX
@@ -747,6 +758,9 @@ int main(int argc, char **argv)
         case QEMU_NBD_OPT_PID_FILE:
             pid_file_name = optarg;
             break;
+        case QEMU_NBD_OPT_SELINUX_LABEL:
+            selinux_label = optarg;
+            break;
         }
     }
 
@@ -938,6 +952,16 @@ int main(int argc, char **argv)
         } else {
             backlog = MIN(shared, SOMAXCONN);
         }
+        if (sockpath && selinux_label) {
+#ifdef CONFIG_SELINUX
+            if (setsockcreatecon_raw(selinux_label) == -1) {
+                error_report("Cannot set SELinux socket create context "
+                             "to %s: %s",
+                             selinux_label, strerror(errno));
+                exit(EXIT_FAILURE);
+            }
+#endif
+        }
         saddr = nbd_build_socket_address(sockpath, bindto, port);
         if (qio_net_listener_open_sync(server, saddr, backlog,
                                        &local_err) < 0) {
@@ -945,6 +969,15 @@ int main(int argc, char **argv)
             error_report_err(local_err);
             exit(EXIT_FAILURE);
         }
+        if (sockpath && selinux_label) {
+#ifdef CONFIG_SELINUX
+            if (setsockcreatecon_raw(NULL) == -1) {
+                error_report("Cannot clear SELinux socket create context: %s",
+                             strerror(errno));
+                exit(EXIT_FAILURE);
+            }
+#endif
+        }
     } else {
         size_t i;
         /* See comment in check_socket_activation above. */
diff --git a/tests/docker/dockerfiles/centos8.docker b/tests/docker/dockerfiles/centos8.docker
index 46398c61ee..7f135f8e8c 100644
--- a/tests/docker/dockerfiles/centos8.docker
+++ b/tests/docker/dockerfiles/centos8.docker
@@ -51,6 +51,7 @@ ENV PACKAGES \
     libpng-devel \
     librbd-devel \
     libseccomp-devel \
+    libselinux-devel \
     libslirp-devel \
     libssh-devel \
     libtasn1-devel \
diff --git a/tests/docker/dockerfiles/fedora.docker b/tests/docker/dockerfiles/fedora.docker
index eec1add7f6..c6fd7e1113 100644
--- a/tests/docker/dockerfiles/fedora.docker
+++ b/tests/docker/dockerfiles/fedora.docker
@@ -53,6 +53,7 @@ ENV PACKAGES \
     libpng-devel \
     librbd-devel \
     libseccomp-devel \
+    libselinux-devel \
     libslirp-devel \
     libssh-devel \
     libtasn1-devel \
diff --git a/tests/docker/dockerfiles/opensuse-leap.docker b/tests/docker/dockerfiles/opensuse-leap.docker
index 5a8bee0289..3bbdb67f4f 100644
--- a/tests/docker/dockerfiles/opensuse-leap.docker
+++ b/tests/docker/dockerfiles/opensuse-leap.docker
@@ -55,6 +55,7 @@ ENV PACKAGES \
     libpulse-devel \
     librbd-devel \
     libseccomp-devel \
+    libselinux-devel \
     libspice-server-devel \
     libssh-devel \
     libtasn1-devel \
diff --git a/tests/docker/dockerfiles/ubuntu1804.docker b/tests/docker/dockerfiles/ubuntu1804.docker
index 0880bf3e29..450fd06d0d 100644
--- a/tests/docker/dockerfiles/ubuntu1804.docker
+++ b/tests/docker/dockerfiles/ubuntu1804.docker
@@ -60,6 +60,7 @@ ENV PACKAGES \
     libsdl2-dev \
     libsdl2-image-dev \
     libseccomp-dev \
+    libselinux-dev \
     libsnappy-dev \
     libspice-protocol-dev \
     libspice-server-dev \
diff --git a/tests/docker/dockerfiles/ubuntu2004.docker b/tests/docker/dockerfiles/ubuntu2004.docker
index 39de63d012..15a026be09 100644
--- a/tests/docker/dockerfiles/ubuntu2004.docker
+++ b/tests/docker/dockerfiles/ubuntu2004.docker
@@ -60,6 +60,7 @@ ENV PACKAGES \
     libsdl2-dev \
     libsdl2-image-dev \
     libseccomp-dev \
+    libselinux-dev \
     libslirp-dev \
     libsnappy-dev \
     libspice-protocol-dev \
-- 
2.31.1

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Daniel P. Berrangé]

On Fri, Jul 23, 2021 at 11:33:03AM +0100, Richard W.M. Jones wrote:
> Under SELinux, Unix domain sockets have two labels.  One is on the
> disk and can be set with commands such as chcon(1).  There is a
> different label stored in memory (called the process label).  This can
> only be set by the process creating the socket.  When using SELinux +
> SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> you must set both labels correctly first.
> 
> For qemu-nbd the options to set the second label are awkward.  You can
> create the socket in a wrapper program and then exec into qemu-nbd.
> Or you could try something with LD_PRELOAD.
> 
> This commit adds the ability to set the label straightforwardly on the
> command line, via the new --selinux-label flag.  (The name of the flag
> is the same as the equivalent nbdkit option.)
> 
> A worked example showing how to use the new option can be found in
> this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> ---
>  configure                                     |  9 ++++-
>  meson.build                                   | 10 +++++-
>  meson_options.txt                             |  3 ++
>  qemu-nbd.c                                    | 33 +++++++++++++++++++
>  tests/docker/dockerfiles/centos8.docker       |  1 +
>  tests/docker/dockerfiles/fedora.docker        |  1 +
>  tests/docker/dockerfiles/opensuse-leap.docker |  1 +
>  tests/docker/dockerfiles/ubuntu1804.docker    |  1 +
>  tests/docker/dockerfiles/ubuntu2004.docker    |  1 +
>  9 files changed, 58 insertions(+), 2 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Kevin Wolf]

Am 23.07.2021 um 12:33 hat Richard W.M. Jones geschrieben:
> Under SELinux, Unix domain sockets have two labels.  One is on the
> disk and can be set with commands such as chcon(1).  There is a
> different label stored in memory (called the process label).  This can
> only be set by the process creating the socket.  When using SELinux +
> SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> you must set both labels correctly first.
> 
> For qemu-nbd the options to set the second label are awkward.  You can
> create the socket in a wrapper program and then exec into qemu-nbd.
> Or you could try something with LD_PRELOAD.
> 
> This commit adds the ability to set the label straightforwardly on the
> command line, via the new --selinux-label flag.  (The name of the flag
> is the same as the equivalent nbdkit option.)
> 
> A worked example showing how to use the new option can be found in
> this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>

I suppose this would also be relevant for the built-in NBD server,
especially in the context of qemu-storage-daemon?

If so, is this something specific to NBD sockets, or would it actually
make sense to have it as a generic option in UnixSocketAddress?

Kevin

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Richard W.M. Jones]

On Fri, Jul 23, 2021 at 06:18:55PM +0200, Kevin Wolf wrote:
> Am 23.07.2021 um 12:33 hat Richard W.M. Jones geschrieben:
> > Under SELinux, Unix domain sockets have two labels.  One is on the
> > disk and can be set with commands such as chcon(1).  There is a
> > different label stored in memory (called the process label).  This can
> > only be set by the process creating the socket.  When using SELinux +
> > SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> > you must set both labels correctly first.
> > 
> > For qemu-nbd the options to set the second label are awkward.  You can
> > create the socket in a wrapper program and then exec into qemu-nbd.
> > Or you could try something with LD_PRELOAD.
> > 
> > This commit adds the ability to set the label straightforwardly on the
> > command line, via the new --selinux-label flag.  (The name of the flag
> > is the same as the equivalent nbdkit option.)
> > 
> > A worked example showing how to use the new option can be found in
> > this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > 
> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> 
> I suppose this would also be relevant for the built-in NBD server,
> especially in the context of qemu-storage-daemon?
>
> If so, is this something specific to NBD sockets, or would it actually
> make sense to have it as a generic option in UnixSocketAddress?

For other NBD sockets, most likely.  I'm not sure about Unix sockets
in general (as in: I know they also have the two label thing, but I
don't know if there's a situation where SVirt protects other sockets
apart from NBD sockets).  I'm sure Dan will know ...

By the way although it appears that setsockcreatecon_raw is setting a
global flag, it seems to actually use a thread-local variable, so
implementing this (although still ugly) would not require locks.

https://github.com/SELinuxProject/selinux/blob/32611aea6543e3a8f32635857e37b4332b0b5c99/libselinux/src/procattr.c#L347

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Daniel P. Berrangé]

On Fri, Jul 23, 2021 at 06:18:55PM +0200, Kevin Wolf wrote:
> Am 23.07.2021 um 12:33 hat Richard W.M. Jones geschrieben:
> > Under SELinux, Unix domain sockets have two labels.  One is on the
> > disk and can be set with commands such as chcon(1).  There is a
> > different label stored in memory (called the process label).  This can
> > only be set by the process creating the socket.  When using SELinux +
> > SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> > you must set both labels correctly first.
> > 
> > For qemu-nbd the options to set the second label are awkward.  You can
> > create the socket in a wrapper program and then exec into qemu-nbd.
> > Or you could try something with LD_PRELOAD.
> > 
> > This commit adds the ability to set the label straightforwardly on the
> > command line, via the new --selinux-label flag.  (The name of the flag
> > is the same as the equivalent nbdkit option.)
> > 
> > A worked example showing how to use the new option can be found in
> > this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > 
> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> 
> I suppose this would also be relevant for the built-in NBD server,
> especially in the context of qemu-storage-daemon?

It depends on the usage scenario really. nbdkit / qemu-nbd are
not commonly run under any SELinux policy, so then end up being
unconfined_t. A QEMU NBD client can't connect to an unconfined_t
socket, so we need to override it with this arg.

In the case of qemu system emulator, under libvirt, it will
already have a svirt_t type, so in that case there is no need
to override the type for the socket.

For qsd there's not really any strong practice established
but i expect most current usage is unconfined_t too and
would benefit from setting label.

> If so, is this something specific to NBD sockets, or would it actually
> make sense to have it as a generic option in UnixSocketAddress?

It is applicable to inet sockets too in fact.


Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Eric Blake]

On Fri, Jul 23, 2021 at 11:47:51AM +0100, Daniel P. Berrangé wrote:
> On Fri, Jul 23, 2021 at 11:33:03AM +0100, Richard W.M. Jones wrote:
> > Under SELinux, Unix domain sockets have two labels.  One is on the
> > disk and can be set with commands such as chcon(1).  There is a
> > different label stored in memory (called the process label).  This can
> > only be set by the process creating the socket.  When using SELinux +
> > SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> > you must set both labels correctly first.
> > 
> > For qemu-nbd the options to set the second label are awkward.  You can
> > create the socket in a wrapper program and then exec into qemu-nbd.
> > Or you could try something with LD_PRELOAD.
> > 
> > This commit adds the ability to set the label straightforwardly on the
> > command line, via the new --selinux-label flag.  (The name of the flag
> > is the same as the equivalent nbdkit option.)
> > 
> > A worked example showing how to use the new option can be found in
> > this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > 
> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> > ---
> >  configure                                     |  9 ++++-
> >  meson.build                                   | 10 +++++-
> >  meson_options.txt                             |  3 ++
> >  qemu-nbd.c                                    | 33 +++++++++++++++++++
> >  tests/docker/dockerfiles/centos8.docker       |  1 +
> >  tests/docker/dockerfiles/fedora.docker        |  1 +
> >  tests/docker/dockerfiles/opensuse-leap.docker |  1 +
> >  tests/docker/dockerfiles/ubuntu1804.docker    |  1 +
> >  tests/docker/dockerfiles/ubuntu2004.docker    |  1 +
> >  9 files changed, 58 insertions(+), 2 deletions(-)
> 
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Thanks. This is a new feature, so it doesn't qualify for inclusion in
6.1, but I'm queuing it through my NBD tree to go in as soon as
upstream reopens for 6.2.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Eric Blake]

On Fri, Jul 23, 2021 at 05:38:06PM +0100, Daniel P. Berrangé wrote:
> On Fri, Jul 23, 2021 at 06:18:55PM +0200, Kevin Wolf wrote:
> > Am 23.07.2021 um 12:33 hat Richard W.M. Jones geschrieben:
> > > Under SELinux, Unix domain sockets have two labels.  One is on the
> > > disk and can be set with commands such as chcon(1).  There is a
> > > different label stored in memory (called the process label).  This can
> > > only be set by the process creating the socket.  When using SELinux +
> > > SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> > > you must set both labels correctly first.
> > > 
> > > For qemu-nbd the options to set the second label are awkward.  You can
> > > create the socket in a wrapper program and then exec into qemu-nbd.
> > > Or you could try something with LD_PRELOAD.
> > > 
> > > This commit adds the ability to set the label straightforwardly on the
> > > command line, via the new --selinux-label flag.  (The name of the flag
> > > is the same as the equivalent nbdkit option.)
> > > 
> > > A worked example showing how to use the new option can be found in
> > > this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > > 
> > > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> > 
> > I suppose this would also be relevant for the built-in NBD server,
> > especially in the context of qemu-storage-daemon?
> 
> It depends on the usage scenario really. nbdkit / qemu-nbd are
> not commonly run under any SELinux policy, so then end up being
> unconfined_t. A QEMU NBD client can't connect to an unconfined_t
> socket, so we need to override it with this arg.
> 
> In the case of qemu system emulator, under libvirt, it will
> already have a svirt_t type, so in that case there is no need
> to override the type for the socket.
> 
> For qsd there's not really any strong practice established
> but i expect most current usage is unconfined_t too and
> would benefit from setting label.
> 
> > If so, is this something specific to NBD sockets, or would it actually
> > make sense to have it as a generic option in UnixSocketAddress?
> 
> It is applicable to inet sockets too in fact.

So now that 6.2 is open, should I queue the patch as is, or wait for a
v3 that makes the option more generic to all socket usage?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Eric Blake]

Ping

On Wed, Aug 25, 2021 at 02:35:04PM -0500, Eric Blake wrote:
> On Fri, Jul 23, 2021 at 05:38:06PM +0100, Daniel P. Berrangé wrote:
> > On Fri, Jul 23, 2021 at 06:18:55PM +0200, Kevin Wolf wrote:
> > > Am 23.07.2021 um 12:33 hat Richard W.M. Jones geschrieben:
> > > > Under SELinux, Unix domain sockets have two labels.  One is on the
> > > > disk and can be set with commands such as chcon(1).  There is a
> > > > different label stored in memory (called the process label).  This can
> > > > only be set by the process creating the socket.  When using SELinux +
> > > > SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> > > > you must set both labels correctly first.
> > > > 
> > > > For qemu-nbd the options to set the second label are awkward.  You can
> > > > create the socket in a wrapper program and then exec into qemu-nbd.
> > > > Or you could try something with LD_PRELOAD.
> > > > 
> > > > This commit adds the ability to set the label straightforwardly on the
> > > > command line, via the new --selinux-label flag.  (The name of the flag
> > > > is the same as the equivalent nbdkit option.)
> > > > 
> > > > A worked example showing how to use the new option can be found in
> > > > this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > > > 
> > > > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > > > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> > > 
> > > I suppose this would also be relevant for the built-in NBD server,
> > > especially in the context of qemu-storage-daemon?
> > 
> > It depends on the usage scenario really. nbdkit / qemu-nbd are
> > not commonly run under any SELinux policy, so then end up being
> > unconfined_t. A QEMU NBD client can't connect to an unconfined_t
> > socket, so we need to override it with this arg.
> > 
> > In the case of qemu system emulator, under libvirt, it will
> > already have a svirt_t type, so in that case there is no need
> > to override the type for the socket.
> > 
> > For qsd there's not really any strong practice established
> > but i expect most current usage is unconfined_t too and
> > would benefit from setting label.
> > 
> > > If so, is this something specific to NBD sockets, or would it actually
> > > make sense to have it as a generic option in UnixSocketAddress?
> > 
> > It is applicable to inet sockets too in fact.
> 
> So now that 6.2 is open, should I queue the patch as is, or wait for a
> v3 that makes the option more generic to all socket usage?
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Vladimir Sementsov-Ogievskiy]

24.09.2021 22:23, Eric Blake wrote:
> Ping
> 
> On Wed, Aug 25, 2021 at 02:35:04PM -0500, Eric Blake wrote:
>> On Fri, Jul 23, 2021 at 05:38:06PM +0100, Daniel P. Berrangé wrote:
>>> On Fri, Jul 23, 2021 at 06:18:55PM +0200, Kevin Wolf wrote:
>>>> Am 23.07.2021 um 12:33 hat Richard W.M. Jones geschrieben:
>>>>> Under SELinux, Unix domain sockets have two labels.  One is on the
>>>>> disk and can be set with commands such as chcon(1).  There is a
>>>>> different label stored in memory (called the process label).  This can
>>>>> only be set by the process creating the socket.  When using SELinux +
>>>>> SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
>>>>> you must set both labels correctly first.
>>>>>
>>>>> For qemu-nbd the options to set the second label are awkward.  You can
>>>>> create the socket in a wrapper program and then exec into qemu-nbd.
>>>>> Or you could try something with LD_PRELOAD.
>>>>>
>>>>> This commit adds the ability to set the label straightforwardly on the
>>>>> command line, via the new --selinux-label flag.  (The name of the flag
>>>>> is the same as the equivalent nbdkit option.)
>>>>>
>>>>> A worked example showing how to use the new option can be found in
>>>>> this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
>>>>>
>>>>> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
>>>>> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
>>>>
>>>> I suppose this would also be relevant for the built-in NBD server,
>>>> especially in the context of qemu-storage-daemon?
>>>
>>> It depends on the usage scenario really. nbdkit / qemu-nbd are
>>> not commonly run under any SELinux policy, so then end up being
>>> unconfined_t. A QEMU NBD client can't connect to an unconfined_t
>>> socket, so we need to override it with this arg.
>>>
>>> In the case of qemu system emulator, under libvirt, it will
>>> already have a svirt_t type, so in that case there is no need
>>> to override the type for the socket.
>>>
>>> For qsd there's not really any strong practice established
>>> but i expect most current usage is unconfined_t too and
>>> would benefit from setting label.
>>>
>>>> If so, is this something specific to NBD sockets, or would it actually
>>>> make sense to have it as a generic option in UnixSocketAddress?
>>>
>>> It is applicable to inet sockets too in fact.

If so, should patch at least be changed to call setsockcreatecon_raw() for inet sockets as well?

With current code selinux_label is silently ignored in that case.

>>
>> So now that 6.2 is open, should I queue the patch as is, or wait for a
>> v3 that makes the option more generic to all socket usage?
>>
> 

-- 
Best regards,
Vladimir

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Daniel P. Berrangé]

On Wed, Aug 25, 2021 at 02:35:04PM -0500, Eric Blake wrote:
> On Fri, Jul 23, 2021 at 05:38:06PM +0100, Daniel P. Berrangé wrote:
> > On Fri, Jul 23, 2021 at 06:18:55PM +0200, Kevin Wolf wrote:
> > > Am 23.07.2021 um 12:33 hat Richard W.M. Jones geschrieben:
> > > > Under SELinux, Unix domain sockets have two labels.  One is on the
> > > > disk and can be set with commands such as chcon(1).  There is a
> > > > different label stored in memory (called the process label).  This can
> > > > only be set by the process creating the socket.  When using SELinux +
> > > > SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> > > > you must set both labels correctly first.
> > > > 
> > > > For qemu-nbd the options to set the second label are awkward.  You can
> > > > create the socket in a wrapper program and then exec into qemu-nbd.
> > > > Or you could try something with LD_PRELOAD.
> > > > 
> > > > This commit adds the ability to set the label straightforwardly on the
> > > > command line, via the new --selinux-label flag.  (The name of the flag
> > > > is the same as the equivalent nbdkit option.)
> > > > 
> > > > A worked example showing how to use the new option can be found in
> > > > this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > > > 
> > > > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > > > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> > > 
> > > I suppose this would also be relevant for the built-in NBD server,
> > > especially in the context of qemu-storage-daemon?
> > 
> > It depends on the usage scenario really. nbdkit / qemu-nbd are
> > not commonly run under any SELinux policy, so then end up being
> > unconfined_t. A QEMU NBD client can't connect to an unconfined_t
> > socket, so we need to override it with this arg.
> > 
> > In the case of qemu system emulator, under libvirt, it will
> > already have a svirt_t type, so in that case there is no need
> > to override the type for the socket.
> > 
> > For qsd there's not really any strong practice established
> > but i expect most current usage is unconfined_t too and
> > would benefit from setting label.
> > 
> > > If so, is this something specific to NBD sockets, or would it actually
> > > make sense to have it as a generic option in UnixSocketAddress?
> > 
> > It is applicable to inet sockets too in fact.
> 
> So now that 6.2 is open, should I queue the patch as is, or wait for a
> v3 that makes the option more generic to all socket usage?

My gut feeling is that it makes sense to have a more generic option,
with the selinux label specified in the "SocketAddress" QAPI type,
and then have util/qemu-sockets.h be setting the context in
socket_listen().

I don't think this invalidates the patch that Richard proprosed
here, as we'll still need the command line argument he's added.
All that will differ is that the setsockcreatecon_raw will get
moved down.

So from that POV, I don't think we need the general solution to
be a blocker, it can be additive.

Regards,
Daniel
-- 
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Re: [PATCH v2] nbd/server: Add --selinux-label option

[Eric Blake]

On Fri, Jul 23, 2021 at 11:33:03AM +0100, Richard W.M. Jones wrote:
> Under SELinux, Unix domain sockets have two labels.  One is on the
> disk and can be set with commands such as chcon(1).  There is a
> different label stored in memory (called the process label).  This can
> only be set by the process creating the socket.  When using SELinux +
> SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> you must set both labels correctly first.
> 
> For qemu-nbd the options to set the second label are awkward.  You can
> create the socket in a wrapper program and then exec into qemu-nbd.
> Or you could try something with LD_PRELOAD.
> 
> This commit adds the ability to set the label straightforwardly on the
> command line, via the new --selinux-label flag.  (The name of the flag
> is the same as the equivalent nbdkit option.)
> 
> A worked example showing how to use the new option can be found in
> this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> ---

I'm making one tweak to your patch before sending the pull request:

> +++ b/qemu-nbd.c
> @@ -64,6 +68,7 @@
>  #define QEMU_NBD_OPT_FORK          263
>  #define QEMU_NBD_OPT_TLSAUTHZ      264
>  #define QEMU_NBD_OPT_PID_FILE      265
> +#define QEMU_NBD_OPT_SELINUX_LABEL 266
>  
>  #define MBR_SIZE 512
>  
> @@ -116,6 +121,9 @@ static void usage(const char *name)
>  "  --fork                    fork off the server process and exit the parent\n"
>  "                            once the server is running\n"
>  "  --pid-file=PATH           store the server's process ID in the given file\n"
> +#ifdef CONFIG_SELINUX
> +"  --selinux-label=LABEL     set SELinux process label on listening socket\n"
> +#endif

The new option is only conditionally advertised under --help (qemu-nbd
lacks a stable machine-parseable output, so scraping --help output
will have to do for now)...

>  #if HAVE_NBD_DEVICE
>  "\n"
>  "Kernel NBD client support:\n"
> @@ -532,6 +540,8 @@ int main(int argc, char **argv)
>          { "trace", required_argument, NULL, 'T' },
>          { "fork", no_argument, NULL, QEMU_NBD_OPT_FORK },
>          { "pid-file", required_argument, NULL, QEMU_NBD_OPT_PID_FILE },
> +        { "selinux-label", required_argument, NULL,
> +          QEMU_NBD_OPT_SELINUX_LABEL },

...but is unconditionally supported as a long option even when support
was not compiled in...

>          { NULL, 0, NULL, 0 }
>      };
>      int ch;
> @@ -558,6 +568,7 @@ int main(int argc, char **argv)
>      int old_stderr = -1;
>      unsigned socket_activation;
>      const char *pid_file_name = NULL;
> +    const char *selinux_label = NULL;
>      BlockExportOptions *export_opts;
>  
>  #ifdef CONFIG_POSIX
> @@ -747,6 +758,9 @@ int main(int argc, char **argv)
>          case QEMU_NBD_OPT_PID_FILE:
>              pid_file_name = optarg;
>              break;
> +        case QEMU_NBD_OPT_SELINUX_LABEL:
> +            selinux_label = optarg;
> +            break;
>          }
>      }
>  
> @@ -938,6 +952,16 @@ int main(int argc, char **argv)
>          } else {
>              backlog = MIN(shared, SOMAXCONN);
>          }
> +        if (sockpath && selinux_label) {
> +#ifdef CONFIG_SELINUX
> +            if (setsockcreatecon_raw(selinux_label) == -1) {
> +                error_report("Cannot set SELinux socket create context "
> +                             "to %s: %s",
> +                             selinux_label, strerror(errno));
> +                exit(EXIT_FAILURE);
> +            }
> +#endif

...but here we silently ignore it if support is not compiled in.
Better is to issue an error message about using an unsupported option,
so I'll squash this in:

diff --git i/qemu-nbd.c w/qemu-nbd.c
index 5dc82c419255..94f8ec07c064 100644
--- i/qemu-nbd.c
+++ w/qemu-nbd.c
@@ -962,6 +962,9 @@ int main(int argc, char **argv)
                              selinux_label, strerror(errno));
                 exit(EXIT_FAILURE);
             }
+#else
+            error_report("SELinux support not enabled in this binary");
+            exit(EXIT_FAILURE);
 #endif
         }
         saddr = nbd_build_socket_address(sockpath, bindto, port);
@@ -978,6 +981,9 @@ int main(int argc, char **argv)
                              strerror(errno));
                 exit(EXIT_FAILURE);
             }
+#else
+            error_report("SELinux support not enabled in this binary");
+            exit(EXIT_FAILURE);
 #endif
         }
     } else {


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v2] nbd/server: Add --selinux-label option

[Richard W.M. Jones]

On Mon, Sep 27, 2021 at 04:18:34PM -0500, Eric Blake wrote:
> On Fri, Jul 23, 2021 at 11:33:03AM +0100, Richard W.M. Jones wrote:
> > Under SELinux, Unix domain sockets have two labels.  One is on the
> > disk and can be set with commands such as chcon(1).  There is a
> > different label stored in memory (called the process label).  This can
> > only be set by the process creating the socket.  When using SELinux +
> > SVirt and wanting qemu to be able to connect to a qemu-nbd instance,
> > you must set both labels correctly first.
> > 
> > For qemu-nbd the options to set the second label are awkward.  You can
> > create the socket in a wrapper program and then exec into qemu-nbd.
> > Or you could try something with LD_PRELOAD.
> > 
> > This commit adds the ability to set the label straightforwardly on the
> > command line, via the new --selinux-label flag.  (The name of the flag
> > is the same as the equivalent nbdkit option.)
> > 
> > A worked example showing how to use the new option can be found in
> > this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > 
> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1984938
> > Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> > ---
> 
> I'm making one tweak to your patch before sending the pull request:
> 
> > +++ b/qemu-nbd.c
> > @@ -64,6 +68,7 @@
> >  #define QEMU_NBD_OPT_FORK          263
> >  #define QEMU_NBD_OPT_TLSAUTHZ      264
> >  #define QEMU_NBD_OPT_PID_FILE      265
> > +#define QEMU_NBD_OPT_SELINUX_LABEL 266
> >  
> >  #define MBR_SIZE 512
> >  
> > @@ -116,6 +121,9 @@ static void usage(const char *name)
> >  "  --fork                    fork off the server process and exit the parent\n"
> >  "                            once the server is running\n"
> >  "  --pid-file=PATH           store the server's process ID in the given file\n"
> > +#ifdef CONFIG_SELINUX
> > +"  --selinux-label=LABEL     set SELinux process label on listening socket\n"
> > +#endif
> 
> The new option is only conditionally advertised under --help (qemu-nbd
> lacks a stable machine-parseable output, so scraping --help output
> will have to do for now)...
> 
> >  #if HAVE_NBD_DEVICE
> >  "\n"
> >  "Kernel NBD client support:\n"
> > @@ -532,6 +540,8 @@ int main(int argc, char **argv)
> >          { "trace", required_argument, NULL, 'T' },
> >          { "fork", no_argument, NULL, QEMU_NBD_OPT_FORK },
> >          { "pid-file", required_argument, NULL, QEMU_NBD_OPT_PID_FILE },
> > +        { "selinux-label", required_argument, NULL,
> > +          QEMU_NBD_OPT_SELINUX_LABEL },
> 
> ...but is unconditionally supported as a long option even when support
> was not compiled in...
> 
> >          { NULL, 0, NULL, 0 }
> >      };
> >      int ch;
> > @@ -558,6 +568,7 @@ int main(int argc, char **argv)
> >      int old_stderr = -1;
> >      unsigned socket_activation;
> >      const char *pid_file_name = NULL;
> > +    const char *selinux_label = NULL;
> >      BlockExportOptions *export_opts;
> >  
> >  #ifdef CONFIG_POSIX
> > @@ -747,6 +758,9 @@ int main(int argc, char **argv)
> >          case QEMU_NBD_OPT_PID_FILE:
> >              pid_file_name = optarg;
> >              break;
> > +        case QEMU_NBD_OPT_SELINUX_LABEL:
> > +            selinux_label = optarg;
> > +            break;
> >          }
> >      }
> >  
> > @@ -938,6 +952,16 @@ int main(int argc, char **argv)
> >          } else {
> >              backlog = MIN(shared, SOMAXCONN);
> >          }
> > +        if (sockpath && selinux_label) {
> > +#ifdef CONFIG_SELINUX
> > +            if (setsockcreatecon_raw(selinux_label) == -1) {
> > +                error_report("Cannot set SELinux socket create context "
> > +                             "to %s: %s",
> > +                             selinux_label, strerror(errno));
> > +                exit(EXIT_FAILURE);
> > +            }
> > +#endif
> 
> ...but here we silently ignore it if support is not compiled in.
> Better is to issue an error message about using an unsupported option,
> so I'll squash this in:
> 
> diff --git i/qemu-nbd.c w/qemu-nbd.c
> index 5dc82c419255..94f8ec07c064 100644
> --- i/qemu-nbd.c
> +++ w/qemu-nbd.c
> @@ -962,6 +962,9 @@ int main(int argc, char **argv)
>                               selinux_label, strerror(errno));
>                  exit(EXIT_FAILURE);
>              }
> +#else
> +            error_report("SELinux support not enabled in this binary");
> +            exit(EXIT_FAILURE);
>  #endif
>          }
>          saddr = nbd_build_socket_address(sockpath, bindto, port);
> @@ -978,6 +981,9 @@ int main(int argc, char **argv)
>                               strerror(errno));
>                  exit(EXIT_FAILURE);
>              }
> +#else
> +            error_report("SELinux support not enabled in this binary");
> +            exit(EXIT_FAILURE);
>  #endif
>          }
>      } else {
> 

Good idea, thanks.

Rich.

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