From ff6867ab94cbe9ddcb4ba18d68a4a2dcb79b865d Mon Sep 17 00:00:00 2001
From: Daiderd Jordan <daiderd@gmail.com>
Date: Sun, 12 May 2019 15:53:40 +0200
Subject: [PATCH 1/3] build: move needsHashRewrite initialization to
 startBuilder

The value of useChroot is not set yet in the constructor, resulting in
hash rewriting being enabled in certain cases where it should not be.

Fixes #2801
---
 src/libstore/build.cc | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 91eb97dfb..30825add4 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -997,13 +997,6 @@ DerivationGoal::DerivationGoal(const Path & drvPath, const StringSet & wantedOut
     , wantedOutputs(wantedOutputs)
     , buildMode(buildMode)
 {
-#if __linux__
-    needsHashRewrite = !useChroot;
-#else
-    /* Darwin requires hash rewriting even when sandboxing is enabled. */
-    needsHashRewrite = true;
-#endif
-
     state = &DerivationGoal::getDerivation;
     name = (format("building of '%1%'") % drvPath).str();
     trace("created");
@@ -1852,6 +1845,13 @@ void DerivationGoal::startBuilder()
         #endif
     }
 
+#if __linux__
+    needsHashRewrite = !useChroot;
+#else
+    /* Darwin requires hash rewriting even when sandboxing is enabled. */
+    needsHashRewrite = true;
+#endif
+
     /* If `build-users-group' is not empty, then we have to build as
        one of the members of that group. */
     if (settings.buildUsersGroup != "" && getuid() == 0) {

From d75bdb5793e5ebf9e480f5a0012d141347725801 Mon Sep 17 00:00:00 2001
From: Daiderd Jordan <daiderd@gmail.com>
Date: Sun, 12 May 2019 16:46:21 +0200
Subject: [PATCH 2/3] build: add test for sandboxed --check

---
 tests/linux-sandbox.sh | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tests/linux-sandbox.sh b/tests/linux-sandbox.sh
index acfd46c54..52967d07d 100644
--- a/tests/linux-sandbox.sh
+++ b/tests/linux-sandbox.sh
@@ -25,3 +25,6 @@ nix path-info -r $outPath | grep input-2
 nix ls-store -R -l $outPath | grep foobar
 
 nix cat-store $outPath/foobar | grep FOOBAR
+
+# Test --check without hash rewriting.
+nix-build dependencies.nix --no-out-link --check --sandbox-paths /nix/store

From ce02fc74b2db35e45906865c8a3ce2e98871eeb8 Mon Sep 17 00:00:00 2001
From: Daiderd Jordan <daiderd@gmail.com>
Date: Sun, 12 May 2019 22:47:41 +0200
Subject: [PATCH 3/3] build: make needsHashRewrite a method

---
 src/libstore/build.cc | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 30825add4..79dcdddbe 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -803,9 +803,6 @@ private:
     /* Whether we're currently doing a chroot build. */
     bool useChroot = false;
 
-    /* Whether we need to perform hash rewriting if there are valid output paths. */
-    bool needsHashRewrite;
-
     Path chrootRootDir;
 
     /* RAII object to delete the chroot directory. */
@@ -885,6 +882,9 @@ public:
         Worker & worker, BuildMode buildMode = bmNormal);
     ~DerivationGoal();
 
+    /* Whether we need to perform hash rewriting if there are valid output paths. */
+    bool needsHashRewrite();
+
     void timedOut() override;
 
     string key() override
@@ -1037,6 +1037,17 @@ DerivationGoal::~DerivationGoal()
 }
 
 
+inline bool DerivationGoal::needsHashRewrite()
+{
+#if __linux__
+    return !useChroot;
+#else
+    /* Darwin requires hash rewriting even when sandboxing is enabled. */
+    return true;
+#endif
+}
+
+
 void DerivationGoal::killChild()
 {
     if (pid != -1) {
@@ -1845,13 +1856,6 @@ void DerivationGoal::startBuilder()
         #endif
     }
 
-#if __linux__
-    needsHashRewrite = !useChroot;
-#else
-    /* Darwin requires hash rewriting even when sandboxing is enabled. */
-    needsHashRewrite = true;
-#endif
-
     /* If `build-users-group' is not empty, then we have to build as
        one of the members of that group. */
     if (settings.buildUsersGroup != "" && getuid() == 0) {
@@ -2083,7 +2087,7 @@ void DerivationGoal::startBuilder()
 #endif
     }
 
-    if (needsHashRewrite) {
+    if (needsHashRewrite()) {
 
         if (pathExists(homeDir))
             throw Error(format("directory '%1%' exists; please remove it") % homeDir);
@@ -3067,7 +3071,7 @@ void DerivationGoal::registerOutputs()
             if (buildMode != bmCheck) actualPath = worker.store.toRealPath(path);
         }
 
-        if (needsHashRewrite) {
+        if (needsHashRewrite()) {
             Path redirected = redirectedOutputs[path];
             if (buildMode == bmRepair
                 && redirectedBadOutputs.find(path) != redirectedBadOutputs.end()