Remove build images

docker/Dockerfile

@@ -0,0 +1,42 @@
+FROM golang:1.16 AS build
+
+# Install dependencies
+RUN apt-get update && apt-get install -y libsecret-1-dev
+
+# Build
+WORKDIR /build/
+COPY VERSION /build/
+
+RUN VERSION=$(cat VERSION) && \
+    curl -L https://github.com/ProtonMail/proton-bridge/archive/refs/tags/${VERSION}.tar.gz \
+        | tar zx --strip-component 1 && \
+    make build-nogui
+
+FROM ubuntu:bionic
+LABEL maintainer="Xiaonan Shen <s@sxn.dev>"
+
+EXPOSE 25/tcp
+EXPOSE 143/tcp
+
+# Install dependencies
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        expect socat pass libsecret-1-0 ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy protonmail
+COPY --from=build /build/proton-bridge/proton-bridge /protonmail/
+
+# Copy bash scripts
+COPY gpgparams entrypoint.sh login.exp /protonmail/
+
+RUN chmod +x /protonmail/login.exp
+
+# Add a user 'protonmail' with UID 8535
+RUN useradd -u 8535 -d /home/protonmail protonmail \
+    && mkdir -p /home/protonmail \
+    && chown protonmail: /home/protonmail
+# change to non-privileged user for extra security
+USER protonmail
+
+ENTRYPOINT ["bash", "/protonmail/entrypoint.sh"]