harden build scripts and fix correctness issues from audit

Security & correctness fixes following the audit in REPORT.md.

  - setup-hypervisor.sh: fix broken error handling — use curl -fsSL,
    check failures properly, return valid exit codes, and fetch
    /releases/latest (arch-aware) instead of the possibly-draft .[0]
  - entrypoint.sh: quote "$@" and build --net conditionally so empty
    NET_INTERFACE/NET_MAC don't yield "tap=,mac="
  - image-updater: replace tight 3s retry loop with capped exponential
    backoff + periodic pull instead of hammering the registry
  - sshd: set PermitRootLogin prohibit-password explicitly (key-only root)
  - vm.Dockerfile: copy only host private keys at mode 600 instead of
    the whole secret/* glob (drops .gitkeep/.pub from /etc/ssh)
  - Makefile: stop generating redundant _pub key files
  - build-image.sh: detect failure via alpine-make-vm-image's real exit
    status rather than grepping stdout for "ERROR"
  - remove orphaned etc/alloy/config.alloy (service not installed)
  - README: correct data.raw path
  - add REPORT.md audit notes (H1/H2 accepted as out-of-scope)

Makefile

@@ -45,7 +45,6 @@ $(SECRET_FILES):
 	ssh-keygen -t "$(KEYTYPE_$(notdir $@))" -f "$@" \
 		-C "automatically generated bearcloud ssh key" \
 		-N ""
-	ssh-keygen -y -f "$@" > "$@_pub"
 
 secrets: $(SECRET_FILES)
 

README.md

@@ -11,8 +11,8 @@ Edit corresponding files in [image/overlay](./image/overlay) to customize VM beh
 # vim .env
 # VM_OPTS="--no-cache" HY_OPTS="--no-cache" make
 # fallocate -l 128G ./data/data.raw
-# sgdisk -o -n 1:0:0 -t 1:8300 ./data.raw
+# sgdisk -o -n 1:0:0 -t 1:8300 ./data/data.raw
-# losetup -Pf ./data.raw
+# losetup -Pf ./data/data.raw
 # mkfs.ext4 /dev/loop0p1
 # losetup -d /dev/loop0
 

image/build-image.sh

@@ -14,14 +14,18 @@ TMP=$(mktemp)
 modprobe nbd max_parts=8  && [ -e /dev/nbd0 ] || mknod /dev/nbd0 b 43 0
 
 cleanup() {
-	 rm $TMP
+	 rm -f "$TMP" "${TMP}.rc"
 }
 
 trap cleanup INT TERM EXIT
 
 # We use BIOS here to skip creating partitions
 
-alpine-make-vm-image \
+RC_FILE="${TMP}.rc"
+
+# Capture the real exit status of alpine-make-vm-image (the `| tee` pipeline
+# would otherwise mask it behind tee's status; busybox ash has no PIPESTATUS).
+{ alpine-make-vm-image \
 	--boot-mode "BIOS" \
     --branch "$ALPINE_BRANCH" \
 	--image-format   "$IMAGE_FORMAT" \
@@ -33,9 +37,11 @@ alpine-make-vm-image \
 	--script-chroot \
 	--packages       "nftables curl docker openssh" \
 	"$IMAGE_FILE" \
-	"$CONFIGURE_SH" | tee $TMP
+	"$CONFIGURE_SH"; echo $? > "$RC_FILE"; } 2>&1 | tee "$TMP"
 
-if grep -q "ERROR" $TMP; then
+rc=$(cat "$RC_FILE" 2>/dev/null || echo 1)
-    echo "BUILD FAILED"
+
-    exit 114514
+if [ "$rc" -ne 0 ]; then
+    echo "BUILD FAILED (alpine-make-vm-image exited $rc)"
+    exit 1
 fi

image/overlay/etc/alloy/config.alloy

@@ -1,88 +0,0 @@
-discovery.docker "local" {
-  host             = "unix:///var/run/docker.sock"
-  refresh_interval = "5s"
-}
-
-discovery.relabel "docker" {
-  targets = discovery.docker.local.targets
-
-  //
-  // Container Name
-  //
-  rule {
-    source_labels = ["__meta_docker_container_name"]
-    regex         = "/(.*)"
-    replacement   = "$1"
-    target_label  = "container"
-  }
-
-  //
-  // Docker Compose
-  //
-  rule {
-    source_labels = ["__meta_docker_container_label_com_docker_compose_service"]
-    target_label  = "service"
-  }
-
-  rule {
-    source_labels = ["__meta_docker_container_label_com_docker_compose_project"]
-    target_label  = "compose_project"
-  }
-
-  //
-  // Image
-  //
-  rule {
-    source_labels = ["__meta_docker_container_image"]
-    target_label  = "image"
-  }
-
-  //
-  // stdout / stderr
-  //
-  rule {
-    source_labels = ["__meta_docker_container_log_stream"]
-    target_label  = "stream"
-  }
-
-  //
-  // Query 用
-  //
-  rule {
-    source_labels = ["__meta_docker_container_label_com_docker_compose_service"]
-    target_label  = "job"
-  }
-}
-
-loki.process "docker" {
-
-  stage.static_labels {
-    values = {
-      node        = env("NODE_NAME"),
-      environment = env("ENVIRONMENT"),
-      platform    = "docker",
-    }
-  }
-
-  forward_to = [loki.write.default.receiver]
-}
-
-loki.source.docker "local" {
-  host = "unix:///var/run/docker.sock"
-
-  targets = discovery.relabel.docker.output
-
-  refresh_interval = "5s"
-
-  forward_to = [
-    loki.process.docker.receiver,
-  ]
-}
-
-loki.write "default" {
-
-  endpoint {
-    url = env("LOKI_URL")
-    tenant_id = env("LOKI_TENANT")
-  }
-}

image/overlay/etc/ssh/sshd_config.d/10-disable-password.conf

@@ -1,4 +1,8 @@
 KbdInteractiveAuthentication no
 PasswordAuthentication no
 PubkeyAuthentication yes
+# Root is the only account with an authorized_keys; allow key-based root login
+# only (never password), and make the policy explicit rather than relying on
+# the compile-time default.
+PermitRootLogin prohibit-password
 

image/overlay/usr/bin/image-updater

@@ -1,5 +1,22 @@
 #!/bin/sh
+# Keep the workspace image fresh. Runs long-lived under supervise-daemon:
+# pulls periodically, with capped exponential backoff on failure instead of a
+# tight retry loop that hammers the registry.
+set -u
 
-until docker pull git.sfclub.cc/cloud/workspace-image:latest >/dev/null 2>&1; do
+IMAGE="git.sfclub.cc/cloud/workspace-image:latest"
-	sleep 3
+INTERVAL="${IMAGE_UPDATER_INTERVAL:-3600}"   # seconds between successful pulls
+MIN_DELAY="${IMAGE_UPDATER_MIN_DELAY:-5}"     # initial retry delay on failure
+MAX_DELAY="${IMAGE_UPDATER_MAX_DELAY:-300}"   # cap on retry delay
+
+while true; do
+    delay="$MIN_DELAY"
+    until docker pull "$IMAGE" >/dev/null 2>&1; do
+        echo "image-updater: pull failed, retrying in ${delay}s" >&2
+        sleep "$delay"
+        delay=$((delay * 2))
+        [ "$delay" -gt "$MAX_DELAY" ] && delay="$MAX_DELAY"
+    done
+    echo "image-updater: pulled $IMAGE"
+    sleep "$INTERVAL"
 done

scripts/entrypoint.sh

@@ -1,8 +1,18 @@
 #!/bin/sh
-set -euo pipefail
+set -eu
 
 API_SOCKET="/hy.socks"
 
+# Build the --net argument, omitting empty fields so cloud-hypervisor can pick
+# sensible defaults (auto-created tap / generated MAC) instead of getting
+# "tap=,mac=".
+NET_INTERFACE="${NET_INTERFACE:-}"
+NET_MAC="${NET_MAC:-}"
+NET_ARG="tap=${NET_INTERFACE}"
+if [ -n "$NET_MAC" ]; then
+  NET_ARG="${NET_ARG},mac=${NET_MAC}"
+fi
+
 /usr/bin/cloud-hypervisor \
   --kernel /boot/vmlinuz-virt --initramfs /boot/initramfs-virt \
   --disk path=/image/vm.raw,image_type=raw \
@@ -11,8 +21,8 @@ API_SOCKET="/hy.socks"
   --cmdline "root=/dev/vda rootfstype=ext4 modules=ext4a rw console=hvc0" \
   --cpus boot=${CPU_COUNT:-4} \
   --memory size=${MEMORY:-4G},shared=on \
-  --net "tap=$NET_INTERFACE,mac=$NET_MAC" \
+  --net "$NET_ARG" \
-  $@ &
+  "$@" &
 
 CH_PID=$!
 

scripts/setup-hypervisor.sh

@@ -1,22 +1,64 @@
 #!/bin/sh
+# Download and install the latest cloud-hypervisor + ch-remote static binaries.
+set -eu
 
-set -u
+API="https://api.github.com/repos/cloud-hypervisor/cloud-hypervisor/releases/latest"
 
-echo "fetching latest version of cloud-hypervisor"
+# Pick the asset matching this architecture.
-RESPONSE=$(curl https://api.github.com/repos/cloud-hypervisor/cloud-hypervisor/releases)
+case "$(uname -m)" in
-HYPERVISOR_URL=$(echo $RESPONSE | jq -r '.[0].assets.[] | select( .name == "cloud-hypervisor-static") | .browser_download_url')
+    x86_64|amd64)
-CH_REMOTE_URL=$(echo $RESPONSE | jq -r '.[0].assets.[] | select( .name == "ch-remote-static") | .browser_download_url' )
+        ch_asset="cloud-hypervisor-static"
+        chremote_asset="ch-remote-static"
+        ;;
+    aarch64|arm64)
+        ch_asset="cloud-hypervisor-static-aarch64"
+        chremote_asset="ch-remote-static-aarch64"
+        ;;
+    *)
+        echo "unsupported architecture: $(uname -m)" >&2
+        exit 1
+        ;;
+esac
 
-if [ $? -ne 0 ]; then
+echo "fetching latest cloud-hypervisor release metadata"
-    echo "FAILED TO FETCH DOWNLOAD LINK OF CLOUD-HYPERVISOR-STATIC"
+if ! RESPONSE=$(curl -fsSL "$API"); then
-    exit -1
+    echo "FAILED TO QUERY CLOUD-HYPERVISOR RELEASES API" >&2
+    exit 1
 fi
 
-curl -sLo /usr/bin/cloud-hypervisor "$HYPERVISOR_URL" && chmod +x /usr/bin/cloud-hypervisor && cloud-hypervisor --help >/dev/null 2>&1 
+HYPERVISOR_URL=$(printf '%s' "$RESPONSE" | jq -r --arg n "$ch_asset" \
+    '.assets[] | select(.name == $n) | .browser_download_url')
+CH_REMOTE_URL=$(printf '%s' "$RESPONSE" | jq -r --arg n "$chremote_asset" \
+    '.assets[] | select(.name == $n) | .browser_download_url')
 
-curl -sLo /usr/bin/ch-remote "$CH_REMOTE_URL" && chmod +x /usr/bin/ch-remote && ch-remote --help >/dev/null 2>&1
+if [ -z "$HYPERVISOR_URL" ] || [ "$HYPERVISOR_URL" = "null" ] \
-
+    || [ -z "$CH_REMOTE_URL" ] || [ "$CH_REMOTE_URL" = "null" ]; then
-if [ $? -ne 0 ]; then
+    echo "FAILED TO RESOLVE DOWNLOAD URLS (asset missing for $(uname -m)?)" >&2
-    echo "FAILED TO DOWNLOAD CLOUD-HYPERVISOR or CLOUD-HYPERVISOR IS NOT EXECUTABLE. (wrong arch?)"
+    exit 1
-    exit -1
 fi
+
+# install_bin <url> <dest>
+install_bin() {
+    _url="$1"; _dest="$2"
+    echo "downloading $_url"
+    if ! curl -fsSL -o "$_dest" "$_url"; then
+        echo "FAILED TO DOWNLOAD $_url" >&2
+        exit 1
+    fi
+    chmod +x "$_dest"
+}
+
+install_bin "$HYPERVISOR_URL" /usr/bin/cloud-hypervisor
+install_bin "$CH_REMOTE_URL" /usr/bin/ch-remote
+
+# Sanity-check the binaries actually run on this platform.
+if ! /usr/bin/cloud-hypervisor --version >/dev/null 2>&1; then
+    echo "cloud-hypervisor is not executable (wrong arch?)" >&2
+    exit 1
+fi
+if ! /usr/bin/ch-remote --version >/dev/null 2>&1; then
+    echo "ch-remote is not executable (wrong arch?)" >&2
+    exit 1
+fi
+
+echo "cloud-hypervisor installed"

vm.Dockerfile

@@ -17,7 +17,13 @@ COPY .env /kitchen/.env
 RUN sh /kitchen/substitution.sh < /kitchen/.env
 COPY --from=bubble-builder --chmod=755 /build/daemon /kitchen/overlay/usr/bin/bubble
 COPY --from=bubble-builder --chmod=755 /build/auth_server /kitchen/overlay/usr/bin/auth-server
-COPY ./secret/* /kitchen/overlay/etc/ssh/
+# Ship only the SSH host private keys (sshd derives the public halves), with
+# strict perms — not the whole secret/ dir (which also holds .pub/.gitkeep).
+COPY --chmod=600 \
+	secret/ssh_host_ed25519_key \
+	secret/ssh_host_ecdsa_key \
+	secret/ssh_host_rsa_key \
+	/kitchen/overlay/etc/ssh/
 RUN --security=insecure \
 	 --mount=type=bind,from=host-modules,source=/,target=/lib/modules \
     cd /kitchen && rm -f vm.raw && ALPINE_BRANCH="3.24" ./build-image.sh