Fix it!

tests/build-remote-trustless-should-fail-0.sh

@@ -1,11 +1,25 @@
 source common.sh
 
-# We act as if remote trusts us, but it doesn't. This fails since we are
-# building input-addressed derivations with `buildDerivation`, which
-# depends on trust.
+[[ $busybox =~ busybox ]] || skipTest "no busybox"
+
+unset NIX_STORE_DIR
+unset NIX_STATE_DIR
+
+# We first build a dependency of the derivation we eventually want to
+# build.
+nix-build build-hook.nix -A passthru.input2 \
+  -o "$TEST_ROOT/input2" \
+  --arg busybox "$busybox" \
+  --store "$TEST_ROOT/local" \
+  --option system-features bar
+
+# Now when we go to build that downstream derivation, Nix will try to
+# copy our already-build `input2` to the remote store. That store object
+# is input-addressed, so this will fail.
+
 file=build-hook.nix
 prog=$(readlink -e ./nix-daemon-untrusting.sh)
 proto=ssh-ng
-trusting=true
 
-! source build-remote-trustless.sh
+expectStderr 1 source build-remote-trustless.sh \
+    | grepQuiet "cannot add path '[^ ]*' because it lacks a signature by a trusted key"