feat: apt wrapper

Signed-off-by: Brian Ketelsen <[email protected]>

Author: bketelsen

build_files/build

@@ -1,6 +1,9 @@
 #!/bin/bash
 set -ouex pipefail
 
+
+
+
 # Repository setup
 mkdir -p /etc/apt/keyrings
 curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.gpg
@@ -176,3 +179,20 @@ sed -i "s/^BUILD_ID=.*/BUILD_ID=\"$BUILD_ID\"/" /usr/lib/os-release
 # and avoid issues with /var/opt being mounted on top
 mkdir -p "/usr/share/factory/opt/incus"
 mv /opt/incus /usr/share/factory/opt/
+
+# probably belong in build_files/shared/finalize, but
+# Make wrapper scripts executable
+chmod +x /usr/libexec/apt-wrapper /usr/libexec/dpkg-wrapper 2>/dev/null || true
+
+
+
+# Set up apt/dpkg wrappers for read-only operation
+# Move real binaries and replace with wrappers
+if [ -f /usr/libexec/apt-wrapper ] && [ ! -f /usr/bin/apt.real ]; then
+  mv /usr/bin/apt /usr/bin/apt.real
+  ln -sf /usr/libexec/apt-wrapper /usr/bin/apt
+fi
+if [ -f /usr/libexec/dpkg-wrapper ] && [ ! -f /usr/bin/dpkg.real ]; then
+  mv /usr/bin/dpkg /usr/bin/dpkg.real
+  ln -sf /usr/libexec/dpkg-wrapper /usr/bin/dpkg
+fi

system_files/usr/libexec/apt-wrapper

@@ -0,0 +1,63 @@
+#!/bin/bash
+# Wrapper for apt that allows read-only operations on immutable systems
+# but blocks package installation/removal with a helpful message
+
+REAL_APT=/usr/bin/apt.real
+
+# Read-only commands that should always work
+readonly_commands=(
+    "list"
+    "search"
+    "show"
+    "showsrc"
+    "depends"
+    "rdepends"
+    "policy"
+    "madison"
+    "changelog"
+    "source"
+    "download"
+    "moo"
+    "help"
+    "--help"
+    "-h"
+    "--version"
+    "-v"
+)
+
+# Check if the first non-option argument is a read-only command
+for arg in "$@"; do
+    # Skip options
+    [[ "$arg" == -* ]] && continue
+
+    # Check if it's a read-only command
+    for cmd in "${readonly_commands[@]}"; do
+        if [[ "$arg" == "$cmd" ]]; then
+            exec "$REAL_APT" "$@"
+        fi
+    done
+
+    # First non-option arg wasn't a read-only command
+    break
+done
+
+# For any other command, check if we're on an immutable system
+if [[ -f /run/ostree-booted ]] || [[ -f /run/nbc-booted ]] || [[ -d /sysroot/ostree ]]; then
+    echo "Error: This is an immutable system (bootc/ostree/nbc)." >&2
+    echo "" >&2
+    echo "Package installation/removal is not supported at runtime." >&2
+    echo "To modify the system, you need to:" >&2
+    echo "  1. Modify the Containerfile and rebuild the image, or" >&2
+    echo "  2. Use 'bootc switch' to switch to a different image" >&2
+    echo "" >&2
+    echo "For user applications, consider using:" >&2
+    echo "  - Flatpak: flatpak install <app>" >&2
+    echo "  - Homebrew: brew install <package>" >&2
+    echo "  - Distrobox: distrobox create && distrobox enter" >&2
+    echo "" >&2
+    echo "Read-only apt commands still work: apt list, apt search, apt show" >&2
+    exit 1
+fi
+
+# If not immutable (e.g., in a container build), run normally
+exec "$REAL_APT" "$@"

system_files/usr/libexec/dpkg-wrapper

@@ -0,0 +1,51 @@
+#!/bin/bash
+# Wrapper for dpkg that allows read-only operations on immutable systems
+# but blocks package installation/removal with a helpful message
+
+REAL_DPKG=/usr/bin/dpkg.real
+
+# Read-only options (these query the database without modifying it)
+# Run normally if ANY of these are the primary action
+for arg in "$@"; do
+    case "$arg" in
+        -l|--list|-L|--listfiles|-s|--status|-S|--search|-p|--print-avail|\
+        --get-selections|--print-architecture|--print-foreign-architectures|\
+        --compare-versions|--help|--version|-\?|--license|--audit|-C|\
+        --yet-to-unpack|--predep-package|--admindir=*|--instdir=*|--root=*)
+            exec "$REAL_DPKG" "$@"
+            ;;
+    esac
+done
+
+# Check for query options that might appear anywhere
+has_query_option=false
+for arg in "$@"; do
+    case "$arg" in
+        -l|--list|-L|--listfiles|-s|--status|-S|--search|-p|--print-avail)
+            has_query_option=true
+            break
+            ;;
+    esac
+done
+
+if $has_query_option; then
+    exec "$REAL_DPKG" "$@"
+fi
+
+# For any other command, check if we're on an immutable system
+if [[ -f /run/ostree-booted ]] || [[ -f /run/nbc-booted ]] || [[ -d /sysroot/ostree ]]; then
+    echo "Error: This is an immutable system (bootc/ostree/nbc)." >&2
+    echo "" >&2
+    echo "Direct package manipulation is not supported at runtime." >&2
+    echo "To modify the system, rebuild the container image." >&2
+    echo "" >&2
+    echo "Read-only dpkg commands still work:" >&2
+    echo "  dpkg -l           # List installed packages" >&2
+    echo "  dpkg -L <pkg>     # List files in a package" >&2
+    echo "  dpkg -s <pkg>     # Show package status" >&2
+    echo "  dpkg -S <file>    # Find which package owns a file" >&2
+    exit 1
+fi
+
+# If not immutable (e.g., in a container build), run normally
+exec "$REAL_DPKG" "$@"