From 74033a844fe57e3e91c71ae37f9a65f6b2f22aa9 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Mon, 4 Dec 2006 23:29:16 +0000
Subject: [PATCH] * Add indirect root registration to the protocol so that
 unprivileged   processes can register indirect roots.  Of course, there is
 still   the problem that the garbage collector can only read the targets of  
 the indirect roots when it's running as root...

---
 src/libstore/gc.cc              | 15 ++++++++++-----
 src/libstore/local-store.hh     |  2 ++
 src/libstore/remote-store.cc    |  9 +++++++++
 src/libstore/remote-store.hh    |  2 ++
 src/libstore/store-api.hh       |  7 +++++++
 src/libstore/worker-protocol.hh |  3 ++-
 src/nix-worker/main.cc          | 10 ++++++++++
 7 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 56e64369a..ba59083ca 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -82,6 +82,15 @@ void LocalStore::syncWithGC()
 }
 
 
+void LocalStore::addIndirectRoot(const Path & path)
+{
+    string hash = printHash32(hashString(htSHA1, path));
+    Path realRoot = canonPath((format("%1%/%2%/auto/%3%")
+        % nixStateDir % gcRootsDir % hash).str());
+    createSymlink(realRoot, path, false);
+}
+
+
 Path addPermRoot(const Path & _storePath, const Path & _gcRoot,
     bool indirect, bool allowOutsideRootsDir)
 {
@@ -90,12 +99,8 @@ Path addPermRoot(const Path & _storePath, const Path & _gcRoot,
     assertStorePath(storePath);
 
     if (indirect) {
-        string hash = printHash32(hashString(htSHA1, gcRoot));
-        Path realRoot = canonPath((format("%1%/%2%/auto/%3%")
-            % nixStateDir % gcRootsDir % hash).str());
-        
         createSymlink(gcRoot, storePath, true);
-        createSymlink(realRoot, gcRoot, false);
+        store->addIndirectRoot(gcRoot);
     }
 
     else {
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 389be33a3..251f8922f 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -61,6 +61,8 @@ public:
 
     void addTempRoot(const Path & path);
 
+    void addIndirectRoot(const Path & path);
+    
     void syncWithGC();
 };
 
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index da63765cd..8dd87d046 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -253,6 +253,15 @@ void RemoteStore::addTempRoot(const Path & path)
 }
 
 
+void RemoteStore::addIndirectRoot(const Path & path)
+{
+    writeInt(wopAddIndirectRoot, to);
+    writeString(path, to);
+    processStderr();
+    readInt(from);
+}
+
+
 void RemoteStore::syncWithGC()
 {
     writeInt(wopSyncWithGC, to);
diff --git a/src/libstore/remote-store.hh b/src/libstore/remote-store.hh
index ad29305db..4b6983045 100644
--- a/src/libstore/remote-store.hh
+++ b/src/libstore/remote-store.hh
@@ -49,6 +49,8 @@ public:
 
     void addTempRoot(const Path & path);
 
+    void addIndirectRoot(const Path & path);
+    
     void syncWithGC();
     
 private:
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 67d230ca7..795488d17 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -91,6 +91,13 @@ public:
        The root disappears as soon as we exit. */
     virtual void addTempRoot(const Path & path) = 0;
 
+    /* Add an indirect root, which is merely a symlink to `path' from
+       /nix/var/nix/gcroots/auto/<hash of `path'>.  `path' is supposed
+       to be a symlink to a store path.  The garbage collector will
+       automatically remove the indirect root when it finds that
+       `path' has disappeared. */
+    virtual void addIndirectRoot(const Path & path) = 0;
+
     /* Acquire the global GC lock, then immediately release it.  This
        function must be called after registering a new permanent root,
        but before exiting.  Otherwise, it is possible that a running
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index 8b1d4e15d..ff47fdd67 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -19,7 +19,8 @@ typedef enum {
     wopBuildDerivations,
     wopEnsurePath,
     wopAddTempRoot,
-    wopSyncWithGC
+    wopAddIndirectRoot,
+    wopSyncWithGC,
 } WorkerOp;
 
 
diff --git a/src/nix-worker/main.cc b/src/nix-worker/main.cc
index c8abe1429..80db782e9 100644
--- a/src/nix-worker/main.cc
+++ b/src/nix-worker/main.cc
@@ -269,6 +269,15 @@ static void performOp(Source & from, Sink & to, unsigned int op)
         break;
     }
 
+    case wopAddIndirectRoot: {
+        Path path = absPath(readString(from));
+        startWork();
+        store->addIndirectRoot(path);
+        stopWork();
+        writeInt(1, to);
+        break;
+    }
+
     case wopSyncWithGC: {
         startWork();
         store->syncWithGC();
@@ -473,6 +482,7 @@ void run(Strings args)
     else if (daemon) {
         if (setuidMode)
             throw Error("daemon cannot be started in setuid mode");
+        chdir("/");
         daemonLoop();
     }