core: Apply rpmfi overrides for /etc to /usr/etc

This fixes installing `mock`, which for some reason has files in `/etc/mock`
owned by `root:mock`.

Closes: https://github.com/projectatomic/rpm-ostree/issues/671

Closes: #677
Approved by: jlebon

src/libpriv/rpmostree-core.c

@@ -2230,6 +2230,7 @@ apply_rpmfi_overrides (int            tmp_metadata_dfd,
   while ((i = rpmfiNext (fi)) >= 0)
     {
       const char *fn = rpmfiFN (fi);
+      g_autofree char *modified_fn = NULL;  /* May be used to override fn */
       const char *user = rpmfiFUser (fi) ?: "root";
       const char *group = rpmfiFGroup (fi) ?: "root";
       const char *fcaps = rpmfiFCaps (fi) ?: '\0';
@@ -2255,6 +2256,11 @@ apply_rpmfi_overrides (int            tmp_metadata_dfd,
       if (g_str_has_prefix (fn, "run/") ||
           g_str_has_prefix (fn, "var/"))
         continue;
+      else if (g_str_has_prefix (fn, "etc/"))
+        {
+          /* The tree uses usr/etc */
+          fn = modified_fn = g_strconcat ("usr/", fn, NULL);
+        }
 
       if (fstatat (tmprootfs_dfd, fn, &stbuf, AT_SYMLINK_NOFOLLOW) != 0)
         {

tests/common/compose/yum/nonrootcap.spec

@@ -1,4 +1,4 @@
-Summary: An app that uses has non-root files and caps
+Summary: An app that has non-root files and caps
 Name: nonrootcap
 Version: 1.0
 Release: 1
@@ -19,6 +19,7 @@ echo "Hello!"
 EOF
 
 chmod a+x tmp
+echo nrc.conf > nrc.conf
 cp tmp nrc-none.sh
 cp tmp nrc-user.sh
 cp tmp nrc-group.sh
@@ -34,6 +35,7 @@ groupadd -r nrcgroup
 useradd -r nrcuser -g nrcgroup -s /sbin/nologin
 
 %install
+install -D nrc.conf %{buildroot}/etc/nrc.conf
 mkdir -p %{buildroot}/usr/bin
 install *.sh %{buildroot}/usr/bin
 mkdir -p %{buildroot}/var/lib/nonrootcap
@@ -46,6 +48,7 @@ rm -rf %{buildroot}
 
 %files
 /usr/bin/nrc-none.sh
+%attr(-, nrcuser, -) /etc/nrc.conf
 %attr(-, nrcuser, -) /usr/bin/nrc-user.sh
 %attr(-, -, nrcgroup) /usr/bin/nrc-group.sh
 %caps(cap_net_bind_service=ep) /usr/bin/nrc-caps.sh

tests/vmcheck/test-layering-non-root-caps.sh

@@ -45,6 +45,7 @@ vm_cmd getent group nrcgroup
 echo "ok user and group added"
 
 if ! vm_has_files /usr/bin/nrc-none.sh \
+                  /etc/nrc.conf \
                   /usr/bin/nrc-user.sh \
                   /usr/bin/nrc-group.sh \
                   /usr/bin/nrc-caps.sh \
@@ -100,4 +101,5 @@ check_file /var/lib/nonrootcap nrcuser nrcgroup
 check_file /run/nonrootcap nrcuser nrcgroup
 check_file /var/lib/nonrootcap-rootowned root root
 check_file /run/nonrootcap-rootowned root root
+check_file /etc/nrc.conf nrcuser root
 echo "ok correct user/group and fcaps"