diff mbox series

nbd/server: Add --selinux-label option

Message ID 20210722163240.1722364-2-rjones@redhat.com (mailing list archive)
State New, archived
Headers show
Series nbd/server: Add --selinux-label option | expand

Commit Message

Richard W.M. Jones July 22, 2021, 4:32 p.m. UTC
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 +++++++++++++++++++++++++++++++++
 4 files changed, 53 insertions(+), 2 deletions(-)

Comments

Daniel P. Berrangé July 22, 2021, 4:43 p.m. UTC | #1
On Thu, Jul 22, 2021 at 05:32:40PM +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 +++++++++++++++++++++++++++++++++
>  4 files changed, 53 insertions(+), 2 deletions(-)


> 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)
> +

For the new build dep we'll need updated package lists in
tests/docker/dockerfiles. For centos, fedra ,opensuse
add libselinux-devel and for ubuntu 18/20 add libselinux-dev

That'll make sure this new code gets tested in CI.


The rest looks ok to me

Regards,
Daniel
diff mbox series

Patch

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. */