build: Sensitive directory permissions (#3120)

Author: shaohuzhang1

installer/Dockerfile

@@ -66,9 +66,10 @@ RUN chmod 755 /opt/maxkb/app/installer/run-maxkb.sh && \
     curl -L --connect-timeout 120 -m 1800 https://resource.fit2cloud.com/maxkb/ffmpeg/get-ffmpeg-linux | sh && \
     mkdir -p /opt/maxkb/app/sandbox/python-packages &&  \
     find /opt/maxkb/app -mindepth 1 -not -name 'sandbox' -exec chmod 700 {} + && \
-    chmod 755 /tmp && \
-    useradd --no-create-home --home /opt/maxkb/app/sandbox sandbox -g root && \
-    chown -R sandbox:root /opt/maxkb/app/sandbox && \
+    chmod 755 /tmp && chmod 750 /etc &&\
+    groupadd sandbox &&\
+    useradd --no-create-home --home /opt/maxkb/app/sandbox sandbox -g sandbox && \
+    chown -R sandbox:sandbox /opt/maxkb/app/sandbox && \
     chmod g-x /usr/local/bin/* /usr/bin/* /bin/* /usr/sbin/* /sbin/* /usr/lib/postgresql/15/bin/* && \
     chmod g+x /usr/local/bin/python*