Added subordinate id ranges for jenkins on CI container hosts

ci/setup-ci-host.sh

@@ -25,6 +25,28 @@ function file-line()
   fi
 }
 
+# Replaces an existing range for the user rather than appending a second one.
+subids_changed=0
+function subid-range()
+{
+  local file=$1
+  local user=$2
+  local range=$3
+
+  touch "$file"
+  if grep -q "^$user:$range\$" "$file"; then
+    return
+  fi
+  if grep -q "^$user:" "$file"; then
+    echo "Correcting $user range in $file to $range"
+    sed -i "s|^$user:.*|$user:$range|" "$file"
+  else
+    echo "Adding $user:$range to $file"
+    echo "$user:$range" >> "$file"
+  fi
+  subids_changed=1
+}
+
 function github-known-hosts()
 {
   echo "ensuring github hostkeys are added to /home/jenkins/.ssh/known_hosts"
@@ -107,6 +129,17 @@ jenkins ALL=NOPASSWD: /usr/bin/podman
 EOF
         chmod 400 /etc/sudoers.d/999-local
         chown root:root /etc/sudoers.d/999-local
+
+        # Without a subordinate id range, rootless container storage runs single-uid
+        # and drops setuid bits while extracting layers, breaking sudo in the image.
+        subid-range /etc/subuid jenkins 100000:65536
+        subid-range /etc/subgid jenkins 100000:65536
+        if [ "$subids_changed" = 1 ]; then
+            # Remap storage and discard images extracted under the previous mapping:
+            # migrate cannot restore setuid bits, so those images must be rebuilt.
+            su - jenkins -c 'podman system migrate'
+            su - jenkins -c 'buildah rmi --all --force'
+        fi
     fi
     exit 0
 fi