Make builtins.{path,filterSource} work with chroot stores

src/libexpr/eval.cc

@@ -445,7 +445,7 @@ EvalState::EvalState(
                     StorePathSet closure;
                     store->computeFSClosure(store->toStorePath(r.second).first, closure);
                     for (auto & path : closure)
-                        allowPath(store->printStorePath(path));
+                        allowPath(path);
                 } catch (InvalidPath &) {
                     allowPath(r.second);
                 }
@@ -488,6 +488,12 @@ void EvalState::allowPath(const Path & path)
         allowedPaths->insert(path);
 }
 
+void EvalState::allowPath(const StorePath & storePath)
+{
+    if (allowedPaths)
+        allowedPaths->insert(store->toRealPath(storePath));
+}
+
 Path EvalState::checkSourcePath(const Path & path_)
 {
     if (!allowedPaths) return path_;
@@ -1895,9 +1901,9 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
             ? store->computeStorePathForPath(std::string(baseNameOf(path)), checkSourcePath(path)).first
             : store->addToStore(std::string(baseNameOf(path)), checkSourcePath(path), FileIngestionMethod::Recursive, htSHA256, defaultPathFilter, repair);
         dstPath = store->printStorePath(p);
+        allowPath(p);
         srcToStore.insert_or_assign(path, std::move(p));
         printMsg(lvlChatty, "copied source '%1%' -> '%2%'", path, dstPath);
-        allowPath(dstPath);
     }
 
     context.insert(dstPath);

src/libexpr/eval.hh

@@ -153,6 +153,10 @@ public:
     /* Allow access to a path. */
     void allowPath(const Path & path);
 
+    /* Allow access to a store path. Note that this gets remapped to
+       the real store path if `store` is a chroot store. */
+    void allowPath(const StorePath & storePath);
+
     /* Check whether access to a path is allowed and throw an error if
        not. Otherwise return the canonicalised path. */
     Path checkSourcePath(const Path & path);

src/libexpr/flake/flake.cc

@@ -64,7 +64,7 @@ static std::tuple<fetchers::Tree, FlakeRef, FlakeRef> fetchOrSubstituteTree(
     debug("got tree '%s' from '%s'",
         state.store->printStorePath(tree.storePath), lockedRef);
 
-    state.allowPath(tree.actualPath);
+    state.allowPath(tree.storePath);
 
     assert(!originalRef.input.getNarHash() || tree.storePath == originalRef.input.computeStorePath(*state.store));
 

src/libexpr/primops.cc

@@ -1859,18 +1859,19 @@ static void addPath(
         // be rewritten to the actual output).
         state.realiseContext(context);
 
-        path = evalSettings.pureEval && expectedHash
-            ? path
-            : state.checkSourcePath(path);
-
         if (state.store->isInStore(path)) {
-            auto storePath = state.store->toStorePath(path).first;
+            auto [storePath, subPath] = state.store->toStorePath(path);
             auto info = state.store->queryPathInfo(storePath);
             if (!info->references.empty())
                 throw EvalError("store path '%s' is not allowed to have references",
                     state.store->printStorePath(storePath));
+            path = state.store->toRealPath(storePath) + subPath;
         }
 
+        path = evalSettings.pureEval && expectedHash
+            ? path
+            : state.checkSourcePath(path);
+
         PathFilter filter = filterFun ? ([&](const Path & path) {
             auto st = lstat(path);
 
@@ -1911,7 +1912,7 @@ static void addPath(
 
         mkString(v, dstPath, {dstPath});
 
-        state.allowPath(v.string.s);
+        state.allowPath(dstPath);
 
     } catch (Error & e) {
         e.addTrace(pos, "while adding path '%s'", path);

src/libexpr/primops/fetchMercurial.cc

@@ -84,7 +84,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
         mkInt(*state.allocAttr(v, state.symbols.create("revCount")), *revCount);
     v.attrs->sort();
 
-    state.allowPath(tree.actualPath);
+    state.allowPath(tree.storePath);
 }
 
 static RegisterPrimOp r_fetchMercurial("fetchMercurial", 1, prim_fetchMercurial);

src/libexpr/primops/fetchTree.cc

@@ -169,7 +169,7 @@ static void fetchTree(
 
     auto [tree, input2] = input.fetch(state.store);
 
-    state.allowPath(tree.actualPath);
+    state.allowPath(tree.storePath);
 
     emitTreeAttrs(state, tree, input2, v, params.emptyRevFallback, false);
 }
@@ -233,18 +233,16 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
         ? fetchers::downloadTarball(state.store, *url, name, (bool) expectedHash).first.storePath
         : fetchers::downloadFile(state.store, *url, name, (bool) expectedHash).storePath;
 
-    auto realPath = state.store->toRealPath(storePath);
-
     if (expectedHash) {
         auto hash = unpack
             ? state.store->queryPathInfo(storePath)->narHash
-            : hashFile(htSHA256, realPath);
+            : hashFile(htSHA256, state.store->toRealPath(storePath));
         if (hash != *expectedHash)
             throw Error((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n  specified: %s\n  got:       %s",
                 *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true));
     }
 
-    state.allowPath(realPath);
+    state.allowPath(storePath);
 
     auto path = state.store->printStorePath(storePath);
     mkString(v, path, PathSet({path}));