core,scripts: When no cachedir+unified-core, disable rofiles-fuse

This is prep for running inside (unprivileged) Kube containers
as they exist today: #1329

Sadly FUSE today uses a suid binary that ends up wanting CAP_SYS_ADMIN.
I think there's some work on FUSE-in-containers but I'm not sure of
the current status.

What rofiles-fuse here is doing here is protecting is the hardlinked
repo imports.  But if `--cachedir` isn't specified, that repository
gets thrown away anyways.  So there's no real value to using FUSE
here.

Also since nothing is cached, disable the devino cache.

We also make use of --force-copy-zerosized that just landed
in libostree: ostreedev/ostree#1752

Down the line ideally we gain the capability to detect if either
unprivileged overlayfs/FUSE are available.  Then if `--cachedir`
is specified we can make things work.

src/app/rpmostree-compose-builtin-tree.c

@@ -113,6 +113,7 @@ typedef struct {
   int workdir_dfd;
   int rootfs_dfd;
   int cachedir_dfd;
+  gboolean unified_core_and_fuse;
   OstreeRepo *repo;
   OstreeRepo *pkgcache_repo;
   OstreeRepoDevInoCache *devino_cache;
@@ -340,9 +341,37 @@ install_packages_in_root (RpmOstreeTreeComposeContext  *self,
                                                    cancellable, error);
       if (!self->pkgcache_repo)
         return FALSE;
+
+      if (!opt_cachedir)
+        {
+          /* This is part of enabling rpm-ostree inside Docker/Kubernetes/OpenShift;
+           * in this case we probably don't have access to FUSE as today it uses a
+           * suid binary which doesn't have the capabilities it needs.
+           *
+           * So this magical bit tells the core to disable FUSE, which we only do
+           * if --cachedir isn't specified.  Another way to say this is that
+           * running inside an unprivileged container today requires turning off
+           * some of the rpm-ostree intelligence around caching.
+           *
+           * We don't make this actually conditional somehow on running in a
+           * container since if you're not using a persistent cache there's no
+           * real advantage to taking the overhead of FUSE. If the hardlinks are
+           * corrupted, it doesn't matter as they're going to be deleted
+           * anyways.
+           */
+          rpmostree_context_disable_rofiles (self->corectx);
+        }
+      else
+        {
+          self->unified_core_and_fuse = TRUE;
+          /* We also only enable the devino cache if we know we have the FUSE protection
+           * against mutation of the underlying files.
+           */
+          self->devino_cache = ostree_repo_devino_cache_new ();
+          rpmostree_context_set_devino_cache (self->corectx, self->devino_cache);
+        }
+
       rpmostree_context_set_repos (self->corectx, self->repo, self->pkgcache_repo);
-      self->devino_cache = ostree_repo_devino_cache_new ();
-      rpmostree_context_set_devino_cache (self->corectx, self->devino_cache);
 
       /* Ensure that the imported packages are labeled with *a* policy if
        * possible, even if it's not the final one. This helps avoid duplicating
@@ -886,7 +915,7 @@ impl_install_tree (RpmOstreeTreeComposeContext *self,
 
   /* Start postprocessing */
   if (!rpmostree_treefile_postprocessing (self->rootfs_dfd, self->treefile_rs, self->treefile,
-                                          next_version, opt_unified_core,
+                                          next_version, self->unified_core_and_fuse,
                                           cancellable, error))
     return glnx_prefix_error (error, "Postprocessing");
 
@@ -999,7 +1028,7 @@ impl_commit_tree (RpmOstreeTreeComposeContext *self,
 
   if (!rpmostree_rootfs_postprocess_common (self->rootfs_dfd, cancellable, error))
     return FALSE;
-  if (!rpmostree_postprocess_final (self->rootfs_dfd, self->treefile, opt_unified_core,
+  if (!rpmostree_postprocess_final (self->rootfs_dfd, self->treefile, self->unified_core_and_fuse,
                                     cancellable, error))
     return FALSE;
 

src/libpriv/rpmostree-core-private.h

@@ -42,6 +42,7 @@ struct _RpmOstreeContext {
   RpmOstreeContextDnfCachePolicy dnf_cache_policy;
   OstreeRepo *ostreerepo;
   OstreeRepo *pkgcache_repo;
+  gboolean enable_rofiles;
   OstreeRepoDevInoCache *devino_cache;
   gboolean unprivileged;
   OstreeSePolicy *sepolicy;

src/libpriv/rpmostree-core.c

@@ -381,6 +381,7 @@ rpmostree_context_init (RpmOstreeContext *self)
 {
   self->tmprootfs_dfd = -1;
   self->dnf_cache_policy = RPMOSTREE_CONTEXT_DNF_CACHE_DEFAULT;
+  self->enable_rofiles = TRUE;
 }
 
 static void
@@ -555,11 +556,19 @@ void
 rpmostree_context_set_devino_cache (RpmOstreeContext *self,
                                     OstreeRepoDevInoCache *devino_cache)
 {
+  g_assert (self->enable_rofiles);
   if (self->devino_cache)
     ostree_repo_devino_cache_unref (self->devino_cache);
   self->devino_cache = devino_cache ? ostree_repo_devino_cache_ref (devino_cache) : NULL;
 }
 
+void
+rpmostree_context_disable_rofiles (RpmOstreeContext *self)
+{
+  g_assert (!self->devino_cache);
+  self->enable_rofiles = FALSE;
+}
+
 DnfContext *
 rpmostree_context_get_dnf (RpmOstreeContext *self)
 {
@@ -2577,6 +2586,7 @@ checkout_package (OstreeRepo   *repo,
                   const char   *pkg_commit,
                   GHashTable   *files_skip,
                   OstreeRepoCheckoutOverwriteMode ovwmode,
+                  gboolean      force_copy_zerosized,
                   GCancellable *cancellable,
                   GError      **error)
 {
@@ -2591,6 +2601,8 @@ checkout_package (OstreeRepo   *repo,
 
   /* Always want hardlinks */
   opts.no_copy_fallback = TRUE;
+  /* Used in the no-rofiles-fuse path */
+  opts.force_copy_zerosized = force_copy_zerosized;
 
   if (files_skip && g_hash_table_size (files_skip) > 0)
     {
@@ -2632,6 +2644,7 @@ checkout_package_into_root (RpmOstreeContext *self,
 
   if (!checkout_package (pkgcache_repo, dfd, path,
                          devino_cache, pkg_commit, files_skip, ovwmode,
+                         !self->enable_rofiles,
                          cancellable, error))
     return glnx_prefix_error (error, "Checkout %s", dnf_package_get_nevra (pkg));
 
@@ -2887,7 +2900,7 @@ relabel_in_thread_impl (RpmOstreeContext *self,
   g_autoptr(OstreeRepoDevInoCache) cache = ostree_repo_devino_cache_new ();
 
   if (!checkout_package (repo, tmpdir_dfd, pkg_dirname, cache,
-                         commit_csum, NULL, OSTREE_REPO_CHECKOUT_OVERWRITE_NONE,
+                         commit_csum, NULL, OSTREE_REPO_CHECKOUT_OVERWRITE_NONE, FALSE,
                          cancellable, error))
     return FALSE;
 
@@ -3256,7 +3269,7 @@ run_script_sync (RpmOstreeContext *self,
     return FALSE;
 
   if (!rpmostree_script_run_sync (pkg, hdr, kind, rootfs_dfd, var_lib_rpm_statedir,
-                                  out_n_run, cancellable, error))
+                                  self->enable_rofiles, out_n_run, cancellable, error))
     return FALSE;
 
   return TRUE;
@@ -3521,7 +3534,8 @@ run_all_transfiletriggers (RpmOstreeContext *self,
       Header hdr;
       while ((hdr = rpmdbNextIterator (mi)) != NULL)
         {
-          if (!rpmostree_transfiletriggers_run_sync (hdr, rootfs_dfd, out_n_run,
+          if (!rpmostree_transfiletriggers_run_sync (hdr, rootfs_dfd, self->enable_rofiles,
+                                                     out_n_run,
                                                      cancellable, error))
             return FALSE;
         }
@@ -3540,8 +3554,8 @@ run_all_transfiletriggers (RpmOstreeContext *self,
       if (!get_package_metainfo (self, path, &hdr, NULL, error))
         return FALSE;
 
-      if (!rpmostree_transfiletriggers_run_sync (hdr, rootfs_dfd, out_n_run,
-                                                 cancellable, error))
+      if (!rpmostree_transfiletriggers_run_sync (hdr, rootfs_dfd, self->enable_rofiles,
+                                                 out_n_run, cancellable, error))
         return FALSE;
     }
   return TRUE;

src/libpriv/rpmostree-core.h

@@ -121,6 +121,7 @@ void rpmostree_context_set_repos (RpmOstreeContext *self,
                                   OstreeRepo       *pkgcache_repo);
 void rpmostree_context_set_devino_cache (RpmOstreeContext *self,
                                          OstreeRepoDevInoCache *devino_cache);
+void rpmostree_context_disable_rofiles (RpmOstreeContext *self);
 void rpmostree_context_set_sepolicy (RpmOstreeContext *self,
                                      OstreeSePolicy   *sepolicy);
 

src/libpriv/rpmostree-scripts.c

@@ -296,6 +296,7 @@ dump_buffered_output_noerr (const char *prefix,
 static gboolean
 run_script_in_bwrap_container (int rootfs_fd,
                                GLnxTmpDir *var_lib_rpm_statedir,
+                               gboolean    enable_fuse,
                                const char *name,
                                const char *scriptdesc,
                                const char *interp,
@@ -354,8 +355,10 @@ run_script_in_bwrap_container (int rootfs_fd,
    * See above for why we special case glibc.
    */
   const gboolean is_glibc_locales = strcmp (pkg_script, "glibc-all-langpacks.posttrans") == 0;
+  RpmOstreeBwrapMutability mutability =
+    (is_glibc_locales || !enable_fuse) ? RPMOSTREE_BWRAP_MUTATE_FREELY : RPMOSTREE_BWRAP_MUTATE_ROFILES;
   bwrap = rpmostree_bwrap_new (rootfs_fd,
-                               is_glibc_locales ? RPMOSTREE_BWRAP_MUTATE_FREELY : RPMOSTREE_BWRAP_MUTATE_ROFILES,
+                               mutability,
                                error);
   if (!bwrap)
     goto out;
@@ -473,6 +476,7 @@ impl_run_rpm_script (const KnownRpmScriptKind *rpmscript,
                      Header         hdr,
                      int            rootfs_fd,
                      GLnxTmpDir    *var_lib_rpm_statedir,
+                     gboolean       enable_fuse,
                      GCancellable  *cancellable,
                      GError       **error)
 {
@@ -541,7 +545,8 @@ impl_run_rpm_script (const KnownRpmScriptKind *rpmscript,
     }
 
   guint64 start_time_ms = g_get_monotonic_time () / 1000;
-  if (!run_script_in_bwrap_container (rootfs_fd, var_lib_rpm_statedir, dnf_package_get_name (pkg),
+  if (!run_script_in_bwrap_container (rootfs_fd, var_lib_rpm_statedir, enable_fuse,
+                                      dnf_package_get_name (pkg),
                                       rpmscript->desc, interp, script, script_arg,
                                       -1, cancellable, error))
     return glnx_prefix_error (error, "Running %s for %s", rpmscript->desc, dnf_package_get_name (pkg));
@@ -567,6 +572,7 @@ run_script (const KnownRpmScriptKind *rpmscript,
             Header                    hdr,
             int                       rootfs_fd,
             GLnxTmpDir               *var_lib_rpm_statedir,
+            gboolean                  enable_fuse,
             gboolean                 *out_did_run,
             GCancellable             *cancellable,
             GError                  **error)
@@ -595,7 +601,7 @@ run_script (const KnownRpmScriptKind *rpmscript,
 
   *out_did_run = TRUE;
   return impl_run_rpm_script (rpmscript, pkg, hdr, rootfs_fd, var_lib_rpm_statedir,
-                              cancellable, error);
+                              enable_fuse, cancellable, error);
 }
 
 #ifdef BUILDOPT_HAVE_RPM_FILETRIGGERS
@@ -715,6 +721,7 @@ rpmostree_script_run_sync (DnfPackage    *pkg,
                            RpmOstreeScriptKind kind,
                            int            rootfs_fd,
                            GLnxTmpDir    *var_lib_rpm_statedir,
+                           gboolean       enable_fuse,
                            guint         *out_n_run,
                            GCancellable  *cancellable,
                            GError       **error)
@@ -737,7 +744,7 @@ rpmostree_script_run_sync (DnfPackage    *pkg,
 
   gboolean did_run = FALSE;
   if (!run_script (scriptkind, pkg, hdr, rootfs_fd,
-                   var_lib_rpm_statedir,
+                   var_lib_rpm_statedir, enable_fuse,
                    &did_run, cancellable, error))
     return FALSE;
 
@@ -752,6 +759,7 @@ rpmostree_script_run_sync (DnfPackage    *pkg,
 gboolean
 rpmostree_transfiletriggers_run_sync (Header        hdr,
                                       int           rootfs_fd,
+                                      gboolean      enable_fuse,
                                       guint        *out_n_run,
                                       GCancellable *cancellable,
                                       GError      **error)
@@ -906,7 +914,7 @@ rpmostree_transfiletriggers_run_sync (Header        hdr,
 
       /* Run it, and log the result */
       guint64 start_time_ms = g_get_monotonic_time () / 1000;
-      if (!run_script_in_bwrap_container (rootfs_fd, NULL, pkg_name,
+      if (!run_script_in_bwrap_container (rootfs_fd, NULL, enable_fuse, pkg_name,
                                           "%transfiletriggerin", interp, script, NULL,
                                           fileno (tmpf_file), cancellable, error))
         return FALSE;

src/libpriv/rpmostree-scripts.h

@@ -63,13 +63,15 @@ rpmostree_script_run_sync (DnfPackage    *pkg,
                            RpmOstreeScriptKind kind,
                            int            rootfs_fd,
                            GLnxTmpDir    *var_lib_rpm_statedir,
+                           gboolean       enable_rofiles,
                            guint         *out_n_run,
                            GCancellable  *cancellable,
                            GError       **error);
 
 gboolean
 rpmostree_transfiletriggers_run_sync (Header         hdr,
                                       int            rootfs_fd,
+                                      gboolean       enable_rofiles,
                                       guint         *out_n_run,
                                       GCancellable  *cancellable,
                                       GError       **error);

tests/common/libtest.sh

@@ -549,3 +549,16 @@ EOF
                     post "semodule -n -i ${install_dir}/${name}.pp" \
                     files "${install_dir}/${name}.pp"
 }
+
+files_are_hardlinked() {
+    inode1=$(stat -c %i $1)
+    inode2=$(stat -c %i $2)
+    test -n "${inode1}" && test -n "${inode2}"
+    [ "${inode1}" == "${inode2}" ]
+}
+
+assert_files_hardlinked() {
+    if ! files_are_hardlinked "$1" "$2"; then
+        fatal "Files '$1' and '$2' are not hardlinked"
+    fi
+}

tests/compose-tests/test-basic-unified.sh

@@ -35,6 +35,21 @@ if ostree --repo=${repobuild} cat ${treeref} /usr/lib/tmpfiles.d/pkg-rpm.conf >
 fi
 echo "ok autovar"
 
+# And verify we're not hardlinking zero-sized files since this path isn't using
+# rofiles-fuse
+co=${repobuild}/tmp/usr-etc
+ostree --repo=${repobuild} checkout -UHz --subpath=/usr/etc ${treeref} ${co}
+# Verify the files exist and are zero-sized
+for f in ${co}/sub{u,g}id; do
+    test -f "$f"
+    test '!' -s "$f"
+done
+if files_are_hardlinked ${co}/sub{u,g}id; then
+    fatal "Hardlinked zero-sized files without cachedir"
+fi
+rm ${co} -rf
+echo "ok no cachedir zero-sized hardlinks"
+
 # And redo it to trigger relabeling
 origrev=$(ostree --repo=${repobuild} rev-parse ${treeref})
 runcompose  --force-nocache --ex-unified-core