Check the signatures when copying store paths around

Broken atm

src/libstore/local-store.cc

@@ -652,6 +652,14 @@ void LocalStore::checkDerivationOutputs(const StorePath & drvPath, const Derivat
     }
 }
 
+void LocalStore::registerDrvOutput(const Realisation & info, CheckSigsFlag checkSigs)
+{
+    settings.requireExperimentalFeature("ca-derivations");
+    if (checkSigs == NoCheckSigs || !realisationIsUntrusted(info))
+        registerDrvOutput(info);
+    else
+        throw Error("cannot register realisation '%s' because it lacks a valid signature", info.outPath.to_string());
+}
 
 void LocalStore::registerDrvOutput(const Realisation & info)
 {

src/libstore/local-store.hh

@@ -203,6 +203,7 @@ public:
     /* Register the store path 'output' as the output named 'outputName' of
        derivation 'deriver'. */
     void registerDrvOutput(const Realisation & info) override;
+    void registerDrvOutput(const Realisation & info, CheckSigsFlag checkSigs) override;
     void cacheDrvOutputMapping(State & state, const uint64_t deriver, const string & outputName, const StorePath & output);
 
     std::optional<const Realisation> queryRealisation(const DrvOutput&) override;

src/libstore/store-api.cc

@@ -798,7 +798,7 @@ std::map<StorePath, StorePath> copyPaths(ref<Store> srcStore, ref<Store> dstStor
     auto pathsMap = copyPaths(srcStore, dstStore, storePaths, repair, checkSigs, substitute);
     try {
         for (auto & realisation : realisations) {
-            dstStore->registerDrvOutput(realisation);
+            dstStore->registerDrvOutput(realisation, checkSigs);
         }
     } catch (MissingExperimentalFeature & e) {
         // Don't fail if the remote doesn't support CA derivations is it might

src/libstore/store-api.hh

@@ -485,6 +485,8 @@ public:
      */
     virtual void registerDrvOutput(const Realisation & output)
     { unsupported("registerDrvOutput"); }
+    virtual void registerDrvOutput(const Realisation & output, CheckSigsFlag checkSigs)
+    { return registerDrvOutput(output); }
 
     /* Write a NAR dump of a store path. */
     virtual void narFromPath(const StorePath & path, Sink & sink) = 0;