1 files changed, 27 insertions, 7 deletions

diff --git a/nix/libstore/build.cc b/nix/libstore/build.cc
index 889ee3d2bd..38048ceebc 100644
--- a/nix/libstore/build.cc
+++ b/nix/libstore/build.cc
@@ -1680,7 +1680,11 @@ void DerivationGoal::startBuilder()
             % drv.platform % settings.thisSystem % drvPath);
     }
 
-    useChroot = settings.useChroot;
+    /* Note: built-in builders are *not* running in a chroot environment so
+       that we can easily implement them in Guile without having it as a
+       derivation input (they are running under a separate build user,
+       though).  */
+    useChroot = settings.useChroot && !isBuiltin(drv);
 
     /* Construct the environment passed to the builder. */
     env.clear();
@@ -2048,12 +2052,7 @@ void DerivationGoal::runChild()
         commonChildInit(builderOut);
 
 #if CHROOT_ENABLED
-	/* Note: built-in builders are *not* running in a chroot environment
-	   so that we can easily implement them in Guile without having it as
-	   a derivation input (they are running under a separate build user,
-	   though).  */
-
-        if (useChroot && !isBuiltin(drv)) {
+        if (useChroot) {
             /* Initialise the loopback interface. */
             AutoCloseFD fd(socket(PF_INET, SOCK_DGRAM, IPPROTO_IP));
             if (fd == -1) throw SysError("cannot open IP socket");
@@ -2631,6 +2630,21 @@ void DerivationGoal::closeLogFile()
 }
 
 
+static void _chown(const Path & path, uid_t uid, gid_t gid)
+{
+    checkInterrupt();
+
+    if (lchown(path.c_str(), uid, gid) == -1) {
+	throw SysError(format("change owner and group of `%1%'") % path);
+    }
+    struct stat st = lstat(path);
+    if (S_ISDIR(st.st_mode)) {
+        for (auto & i : readDirectory(path))
+            _chown(path + "/" + i.name, uid, gid);
+    }
+}
+
+
 void DerivationGoal::deleteTmpDir(bool force)
 {
     if (tmpDir != "") {
@@ -2639,6 +2653,12 @@ void DerivationGoal::deleteTmpDir(bool force)
                 format("note: keeping build directory `%2%'")
                 % drvPath % tmpDir);
             chmod(tmpDir.c_str(), 0755);
+            // Change the ownership if clientUid is set. Never change the
+            // ownership or the group to "root" for security reasons.
+            if (settings.clientUid != (uid_t) -1 && settings.clientUid != 0) {
+                _chown(tmpDir, settings.clientUid,
+                       settings.clientGid != 0 ? settings.clientGid : -1);
+            }
         }
         else
             deletePath(tmpDir);