deblobbify, replacing the system folder with several other components

Author: robertkirkman

.github/workflows/docker_build.yml

@@ -14,38 +14,29 @@ env:
   DOCKER_BUILDKIT: 1
 
 jobs:
-  main:
-    runs-on: ubuntu-latest
+  generate:
     strategy:
       matrix:
-        CPU_ARCH:
-          - aarch64
-          - arm
-          - i686
-          - x86_64
+        include:
+          - runner: ubuntu-24.04
+            architecture: i686
+          - runner: ubuntu-24.04
+            architecture: x86_64
+          - runner: ubuntu-24.04-arm
+            architecture: arm
+          - runner: ubuntu-24.04-arm
+            architecture: aarch64
+    runs-on: ${{ matrix.runner }}
     steps:
 
+    - name: Set architecture variable
+      run: echo "TERMUX_ARCH=${{ matrix.architecture }}" >> $GITHUB_ENV
+
     - name: Clone repository
       uses: actions/checkout@v4
 
-    - name: Setup binfmt_misc
-      if: (matrix.CPU_ARCH == 'aarch64') || (matrix.CPU_ARCH == 'arm')
-      run: docker run --rm --privileged aptman/qus -s -- -p aarch64 arm
-
-    - name: Build images
-      run: |
-        case '${{ matrix.CPU_ARCH }}' in
-          arm)     SYSTEM_TYPE=arm; PLATFORM_TAG="linux/arm/v7";;
-          aarch64) SYSTEM_TYPE=arm; PLATFORM_TAG="linux/arm64";;
-          i686)    SYSTEM_TYPE=x86; PLATFORM_TAG="linux/386";;
-          *)       SYSTEM_TYPE=x86; PLATFORM_TAG="linux/amd64";;
-        esac
-        docker buildx build -t \
-          termux/termux-docker:${{ matrix.CPU_ARCH }} \
-          --platform "$PLATFORM_TAG" \
-          --build-arg BOOTSTRAP_ARCH=${{ matrix.CPU_ARCH }} \
-          --build-arg SYSTEM_TYPE="${SYSTEM_TYPE}" \
-          .
+    - name: Build image
+      run: ./generate.sh
 
     - name: Login to Docker Hub
       if: github.ref == 'refs/heads/master' && github.event_name != 'pull_request' && github.repository == 'termux/termux-docker'
@@ -57,28 +48,26 @@ jobs:
     - name: Push to Docker Hub
       if: github.ref == 'refs/heads/master' && github.event_name != 'pull_request' && github.repository == 'termux/termux-docker'
       run: |
-        docker push termux/termux-docker:${{ matrix.CPU_ARCH }}
-        if [ ${{ matrix.CPU_ARCH }} = i686 ]; then
-          docker tag termux/termux-docker:i686 termux/termux-docker:latest
+        docker push termux/termux-docker:${{ env.TERMUX_ARCH }}
+        if [ ${{ env.TERMUX_ARCH }} = x86_64 ]; then
           docker push termux/termux-docker:latest
         fi
 
     - name: Export container as tar archive
       if: always()
       run: |
         docker run \
-          --privileged \
-          --name termux-docker-${{ matrix.CPU_ARCH }} \
-          termux/termux-docker:${{ matrix.CPU_ARCH }} \
+          --name termux-docker-${{ env.TERMUX_ARCH }} \
+          termux/termux-docker:${{ env.TERMUX_ARCH }} \
           uname -a
-        docker stop termux-docker-${{ matrix.CPU_ARCH }}
-        docker export -o termux-docker-${{ matrix.CPU_ARCH }}.tar \
-          termux-docker-${{ matrix.CPU_ARCH }}
-        sha256sum termux-docker-${{ matrix.CPU_ARCH }}.tar
+        docker stop termux-docker-${{ env.TERMUX_ARCH }}
+        docker export -o termux-docker-${{ env.TERMUX_ARCH }}.tar \
+          termux-docker-${{ env.TERMUX_ARCH }}
+        sha256sum termux-docker-${{ env.TERMUX_ARCH }}.tar
 
     - name: Store tar archive
       if: always()
       uses: actions/upload-artifact@v4
       with:
-        name: termux-docker-${{ matrix.CPU_ARCH }}-${{ github.sha }}
-        path: termux-docker-${{ matrix.CPU_ARCH }}.tar
+        name: termux-docker-${{ env.TERMUX_ARCH }}-${{ github.sha }}
+        path: termux-docker-${{ env.TERMUX_ARCH }}.tar

.gitignore

@@ -0,0 +1 @@
+termux-docker-rootfs

Dockerfile

@@ -2,90 +2,64 @@
 # Bootstrap Termux environment.
 FROM scratch AS bootstrap
 
-ARG BOOTSTRAP_VERSION=2023.02.19-r1%2Bapt-android-7
-ARG BOOTSTRAP_ARCH=i686
-ARG SYSTEM_TYPE=x86
+ARG TERMUX_DOCKER__ROOTFS
+ARG TERMUX__PREFIX
+ARG TERMUX__CACHE_DIR
 
-# Docker uses /bin/sh by default, but we don't have it currently.
-SHELL ["/system/bin/sh", "-c"]
-ENV PATH /system/bin
+# Install generated rootfs containing:
+# - termux bootstrap
+# - aosp-libs (bionic libc, linker, boringssl, zlib, libicuuc, debuggerd)
+# - aosp-utils (toybox, mksh, iputils)
+# - libandroid-stub
+# - dnsmasq
+# Since /system is now a symbolic link to $PREFIX/opt/aosp,
+# which has contents that can be updated by the system user via apt,
+# the entire rootfs is now owned by the system user (1000:1000).
+COPY --chown=1000:1000 ${TERMUX_DOCKER__ROOTFS} /
 
-# Copy libc, linker and few utilities.
-COPY /system/$SYSTEM_TYPE /system
+# Docker uses /bin/sh by default, but we don't have it.
+ENV PATH=/system/bin
+SHELL ["sh", "-c"]
 
-# Copy entrypoint script.
-COPY /entrypoint.sh /entrypoint.sh
-COPY /entrypoint_root.sh /entrypoint_root.sh
-
-# Extract bootstrap archive and create symlinks.
-ADD https://github.com/termux/termux-packages/releases/download/bootstrap-$BOOTSTRAP_VERSION/bootstrap-$BOOTSTRAP_ARCH.zip /bootstrap.zip
-RUN busybox mkdir -p /data/data/com.termux/files && \
-    cd /data/data/com.termux/files && \
-    busybox mkdir ../cache ./usr ./home && \
-    busybox unzip -d usr /bootstrap.zip && \
-    busybox rm /bootstrap.zip && \
-    cd ./usr && \
-    busybox cat SYMLINKS.txt | while read -r line; do \
-      dest=$(echo "$line" | busybox awk -F '←' '{ print $1 }'); \
-      link=$(echo "$line" | busybox awk -F '←' '{ print $2 }'); \
-      busybox ln -s "$dest" "$link"; \
-    done && \
-    busybox rm SYMLINKS.txt && \
-    busybox ln -s /data/data/com.termux/files/usr /usr && \
-    busybox ln -s /data/data/com.termux/files/usr/bin /bin && \
-    busybox ln -s /data/data/com.termux/files/usr/tmp /tmp
-
-# Link some utilities to busybox.
-# Some utilities in $PREFIX are actually a wrapper of the same binary
-# from /system/bin. See termux-tools/build.sh#L29.
-RUN for tool in df mount ping ping6 su top umount; do \
-        busybox ln -s /system/bin/busybox /system/bin/$tool; \
-    done
-
-# Set ownership and file access modes:
-# * User content is owned by 1000:1000.
-# * Termux file modes are set only for user.
-# * Rest is owned by root and has 755/644 modes.
-RUN busybox chown -Rh 0:0 /system && \
-    busybox chown -Rh 1000:1000 /data/data/com.termux && \
-    busybox ln -s /system/etc/passwd /etc/passwd && \
-    busybox ln -s /system/etc/group /etc/group && \
-    busybox find /system -type d -exec busybox chmod 755 "{}" \; && \
-    busybox find /system -type f -executable -exec busybox chmod 755 "{}" \; && \
-    busybox find /system -type f ! -executable -exec busybox chmod 644 "{}" \; && \
-    busybox find /data -type d -exec busybox chmod 755 "{}" \; && \
-    busybox find /data/data/com.termux/files -type f -o -type d -exec busybox chmod g-rwx,o-rwx "{}" \; && \
-    cd /data/data/com.termux/files/usr && \
-    busybox find ./bin ./lib/apt ./libexec -type f -exec busybox chmod 700 "{}" \;
-
-# Install updates and cleanup when not building for arm.
-ENV PATH /data/data/com.termux/files/usr/bin
-RUN if [ ${SYSTEM_TYPE} = 'arm' ]; then exit; else \
-    /system/bin/mksh -T /dev/ptmx -c "/system/bin/dnsmasq -u root -g root --pid-file /dnsmasq.pid" && sleep 1 && \
-    su - system -c "/data/data/com.termux/files/usr/bin/apt update" && \
-    su - system -c "/data/data/com.termux/files/usr/bin/apt upgrade -o Dpkg::Options::=--force-confnew -yq" && \
-    rm -rf /data/data/com.termux/files/usr/var/lib/apt/* && \
-    rm -rf /data/data/com.termux/files/usr/var/log/apt/* && \
-    rm -rf /data/data/com.termux/cache/apt/* ;\
-    fi
+# Install updates and cleanup
+# Start dnsmasq to resolve hostnames, and,
+# for some reason the -c argument of toybox-su is not working,
+# so this odd-looking script forces the update process
+# to work using the -s argument of toybox-su instead, which is working.
+RUN sh -T /dev/ptmx -c "$TERMUX__PREFIX/bin/dnsmasq -u root -g root --pid-file=/dnsmasq.pid" && \
+    sleep 1 && \
+    echo '#!/system/bin/sh' > /update.sh && \
+    echo "PATH=$TERMUX__PREFIX/bin" >> /update.sh && \
+    echo 'apt update' >> /update.sh && \
+    echo 'apt upgrade -o Dpkg::Options::=--force-confnew -y' >> /update.sh && \
+    chmod +x /update.sh && \
+    su system -s /update.sh && \
+    rm -f /update.sh && \
+    rm -rf "${TERMUX__PREFIX}"/var/lib/apt/* && \
+    rm -rf "${TERMUX__PREFIX}"/var/log/apt/* && \
+    rm -rf "${TERMUX__CACHE_DIR}"/apt/*
 
 ##############################################################################
 # Create final image.
 FROM scratch
 
-ENV ANDROID_DATA     /data
-ENV ANDROID_ROOT     /system
-ENV HOME             /data/data/com.termux/files/home
-ENV LANG             en_US.UTF-8
-ENV PATH             /data/data/com.termux/files/usr/bin
-ENV PREFIX           /data/data/com.termux/files/usr
-ENV TMPDIR           /data/data/com.termux/files/usr/tmp
-ENV TZ               UTC
+ARG TERMUX__PREFIX
+ARG TERMUX__HOME
+
+ENV ANDROID_DATA=/data
+ENV ANDROID_ROOT=/system
+ENV HOME=${TERMUX__HOME}
+ENV LANG=en_US.UTF-8
+ENV PATH=${TERMUX__PREFIX}/bin
+ENV PREFIX=${TERMUX__PREFIX}
+ENV TMPDIR=${TERMUX__PREFIX}/tmp
+ENV TZ=UTC
+ENV TERM=xterm
 
 COPY --from=bootstrap / /
 
-WORKDIR /data/data/com.termux/files/home
-SHELL ["/data/data/com.termux/files/usr/bin/sh", "-c"]
+WORKDIR ${TERMUX__HOME}
+SHELL ["sh", "-c"]
 
 ENTRYPOINT ["/entrypoint.sh"]
-CMD ["/data/data/com.termux/files/usr/bin/login"]
+CMD ["login"]

README.md

@@ -21,15 +21,15 @@ normal Termux installation.
 docker run -it termux/termux-docker:latest
 ```
 
-When using the tag `latest`, container will be 32 bit (i686 architecture).
+When using the tag `latest`, container will be 64 bit (x86_64 architecture).
 
 Other architecture can be installed using a different tags. Available
 tags:
 
 - `aarch64`
 - `arm`
-- `i686` (`latest`)
-- `x86_64`
+- `i686`
+- `x86_64` (`latest`)
 
 If architecture is not compatible with host, the additional setup will
 be needed. Read this document further to learn how you can run containers
@@ -39,7 +39,7 @@ of incompatible CPU architecture.
 The initial user of container must be root. Otherwise DNS will be broken
 because of `dnsmasq` server failure.
 
-### Running ARM containers on x86 host
+### Running ARM containers
 
 In order to run AArch64 container on x86(64) host, you need to setup
 QEMU emulator through binfmt_misc. This can be easily done by one
@@ -49,9 +49,12 @@ command:
 docker run --rm --privileged aptman/qus -s -- -p aarch64 arm
 ```
 
-Note that AArch64 and ARM containers work properly only in privileged
-mode. If you want your containers to have standard privileges, a custom
-seccomp profile is required.
+Note that AArch64 and ARM containers sometimes work properly only in privileged
+mode, even on some real ARM devices. If you want your containers to have standard privileges, a custom
+seccomp profile or a custom build of Docker might be required. The custom build
+of Docker limits the customizations to purely what is necessary for
+the `personality()` system call, leaving the security settings of all other system
+calls untouched.
 
 Variant with privileged container:
 
@@ -65,6 +68,25 @@ Variant with seccomp unconfined profile:
 docker run -it --security-opt seccomp:unconfined termux/termux-docker:aarch64
 ```
 
+Variant with custom build of Docker:
+
+> [!NOTE]
+> Example with Debian bookworm `armhf` host and the `docker.io` package. Assumes that [`deb-src` URIs](https://wiki.debian.org/Packaging/SourcePackage?action=show&redirect=SourcePackage#With_apt-get_source) and the [`devscripts` package](https://wiki.debian.org/Packaging#Suggested_tools_to_create_an_environment_for_packaging) are already installed, and that the current user is a member of the `docker` group.
+
+```.sh
+sudo apt build-dep docker.io
+apt source docker.io
+cp /path/to/termux-docker/custom-docker-with-unrestricted-personality.patch docker.io-*/debian/patches/
+echo 'custom-docker-with-unrestricted-personality.patch' >> docker.io-*/debian/patches/series 
+cd docker.io-*/
+DEB_BUILD_OPTIONS=nocheck debuild -b -uc -us
+rm ../golang*
+sudo apt install ../*.deb
+docker run -it termux/termux-docker:arm
+```
+
+You might then want to temporarily use `sudo apt-mark hold docker.io` to ensure the package is not automatically upgraded, causing termux-docker to stop working on the device in the future, but **not upgrading can be a security risk**. If using the patch, it is recommended to patch and recompile the Docker daemon after every upgrade.
+
 ### Non-interactive execution of commands
 
 You can run commands in non-interactive mode. Just append them to Docker
@@ -99,20 +121,20 @@ docker run -it --entrypoint /entrypoint_root.sh termux/termux-docker:latest
 Docker:
 
 ```.sh
-./build-all.sh
+./generate.sh
 ```
 
 Podman:
 
 ```.sh
-./build-all.sh --podman
+./generate.sh --podman
 ```
 
 ## Known issues
 
 There a number of known issues which may not be resolved:
 
-* ARM containers may require a custom seccomp profile to remove restrictions from
+* ARM containers might require a custom seccomp profile or custom build of Docker to remove restrictions from the
   `personality()` system call.
 
 * When running certain multi threaded program in 32bit containers, the PIDs can