warn if apt-key is run unconditionally in maintainerscript

We want to stop hard-depending on gnupg and for this it is essential
that apt-key isn't used in any critical execution path, which
maintainerscript are. Especially as it is likely that these script call
apt-key either only for (potentially now outdated cleanup) or still not
use the much simpler trusted.gpg.d infrastructure.

1 files changed, 14 insertions, 1 deletions

diff --git a/cmdline/apt-key.in b/cmdline/apt-key.in
index 3ed2a70ce..3f9f01627 100644
--- a/cmdline/apt-key.in
+++ b/cmdline/apt-key.in
@@ -493,8 +493,21 @@ create_gpg_home() {
 }
 
 prepare_gpg_home() {
+    # crude detection if we are called from a maintainerscript where the
+    # package depends on gnupg or not. We accept recommends here as
+    # well as the script hopefully uses apt-key optionally then like e.g.
+    # debian-archive-keyring for (upgrade) cleanup did
+    if [ -n "$DPKG_MAINTSCRIPT_PACKAGE" ]; then
+	if ! dpkg-query --show --showformat '${Pre-Depends}${Depends}${Recommends}' "$DPKG_MAINTSCRIPT_PACKAGE" 2>/dev/null | grep -q gnupg; then
+	    cat >&2 <<EOF
+Warning: The $DPKG_MAINTSCRIPT_NAME maintainerscript of the package $DPKG_MAINTSCRIPT_PACKAGE
+Warning: seems to use apt-key (provided by apt) without depending on gnupg or gnupg2.
+Warning: This will BREAK in the future and should be fixed by the package maintainer(s).
+Note: Check first if apt-key functionality is needed at all - it probably isn't!
+EOF
+	fi
+    fi
     eval "$(apt-config shell GPG_EXE Apt::Key::gpgcommand)"
-
     if [ -n "$GPG_EXE" ] && command_available "$GPG_EXE"; then
 	true
     elif command_available 'gpg'; then