Drop support for running nix-worker in "slave" mode

AFAIK nobody uses this, setuid binaries are evil, and there is no good
reason why people can't just run the daemon.

doc/manual/conf-file.xml

@@ -201,10 +201,8 @@ flag, e.g. <literal>--option gc-keep-outputs false</literal>.</para>
     under the uid of the Nix process (that is, the uid of the caller
     if <envar>NIX_REMOTE</envar> is empty, the uid under which the Nix
     daemon runs if <envar>NIX_REMOTE</envar> is
-    <literal>daemon</literal>, or the uid that owns the setuid
-    <command>nix-worker</command> program if <envar>NIX_REMOTE</envar>
-    is <literal>slave</literal>).  Obviously, this should not be used
-    in multi-user settings with untrusted users.</para>
+    <literal>daemon</literal>).  Obviously, this should not be used in
+    multi-user settings with untrusted users.</para>
 
     </listitem>
 

src/libmain/shared.cc

@@ -125,8 +125,7 @@ static void initAndRun(int argc, char * * argv)
 
     /* There is no privacy in the Nix system ;-)  At least not for
        now.  In particular, store objects should be readable by
-       everybody.  This prevents nasty surprises when using a shared
-       store (with the setuid() hack). */
+       everybody. */
     umask(0022);
 
     /* Process the NIX_LOG_TYPE environment variable. */
@@ -218,56 +217,6 @@ static void initAndRun(int argc, char * * argv)
 }
 
 
-bool setuidMode = false;
-
-
-static void setuidInit()
-{
-    /* Don't do anything if this is not a setuid binary. */
-    if (getuid() == geteuid() && getgid() == getegid()) return;
-
-    uid_t nixUid = geteuid();
-    gid_t nixGid = getegid();
-
-    setuidCleanup();
-
-    /* Don't trust the current directory. */
-    if (chdir("/") == -1) abort();
-
-    /* Set the real (and preferably also the save) uid/gid to the
-       effective uid/gid.  This matters mostly when we're not using
-       build-users (bad!), since some builders (like Perl) complain
-       when real != effective.
-
-       On systems where setresuid is unavailable, we can't drop the
-       saved uid/gid.  This means that we could go back to the
-       original real uid (i.e., the uid of the caller).  That's not
-       really a problem, except maybe when we execute a builder and
-       we're not using build-users.  In that case, the builder may be
-       able to switch to the uid of the caller and possibly do bad
-       stuff.  But note that when not using build-users, the builder
-       could also modify the Nix executables (say, replace them by a
-       Trojan horse), so the problem is already there. */
-
-#if HAVE_SETRESUID
-    if (setresuid(nixUid, nixUid, nixUid)) abort();
-    if (setresgid(nixGid, nixGid, nixGid)) abort();
-#elif HAVE_SETREUID
-    /* Note: doesn't set saved uid/gid! */
-    fprintf(stderr, "warning: cannot set saved uid\n");
-    if (setreuid(nixUid, nixUid)) abort();
-    if (setregid(nixGid, nixGid)) abort();
-#else
-    /* Note: doesn't set real and saved uid/gid! */
-    fprintf(stderr, "warning: cannot set real and saved uids\n");
-    if (setuid(nixUid)) abort();
-    if (setgid(nixGid)) abort();
-#endif
-
-    setuidMode = true;
-}
-
-
 /* Called when the Boehm GC runs out of memory. */
 static void * oomHandler(size_t requested)
 {
@@ -298,11 +247,6 @@ int main(int argc, char * * argv)
 
     argvSaved = argv;
 
-    /* If we're setuid, then we need to take some security precautions
-       right away. */
-    if (argc == 0) abort();
-    setuidInit();
-
     /* Turn on buffering for cerr. */
 #if HAVE_PUBSETBUF
     std::cerr.rdbuf()->pubsetbuf(buf, sizeof(buf));

src/libmain/shared.hh

@@ -44,9 +44,6 @@ template<class N> N getIntArg(const string & opt,
 /* Show the manual page for the specified program. */
 void showManPage(const string & name);
 
-/* Whether we're running setuid. */
-extern bool setuidMode;
-
 extern volatile ::sig_atomic_t blockInt;
 
 /* Exit code of the program. */

src/libstore/remote-store.cc

@@ -50,16 +50,12 @@ void RemoteStore::openConnection(bool reserveSpace)
 
     string remoteMode = getEnv("NIX_REMOTE");
 
-    if (remoteMode == "slave")
-        /* Fork off a setuid worker to do the privileged work. */
-        forkSlave();
-    else if (remoteMode == "daemon")
+    if (remoteMode == "daemon")
         /* Connect to a daemon that does the privileged work for
            us. */
-       connectToDaemon();
+        connectToDaemon();
     else
-         throw Error(format("invalid setting for NIX_REMOTE, `%1%'")
-             % remoteMode);
+        throw Error(format("invalid setting for NIX_REMOTE, `%1%'") % remoteMode);
 
     from.fd = fdSocket;
     to.fd = fdSocket;
@@ -88,54 +84,6 @@ void RemoteStore::openConnection(bool reserveSpace)
 }
 
 
-void RemoteStore::forkSlave()
-{
-    int sockets[2];
-    if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) == -1)
-        throw SysError("cannot create sockets");
-
-    fdSocket = sockets[0];
-    AutoCloseFD fdChild = sockets[1];
-
-    /* Start the worker. */
-    Path worker = getEnv("NIX_WORKER");
-    if (worker == "")
-        worker = settings.nixBinDir + "/nix-worker";
-
-    child = fork();
-
-    switch (child) {
-
-    case -1:
-        throw SysError("unable to fork");
-
-    case 0:
-        try { /* child */
-
-            if (dup2(fdChild, STDOUT_FILENO) == -1)
-                throw SysError("dupping write side");
-
-            if (dup2(fdChild, STDIN_FILENO) == -1)
-                throw SysError("dupping read side");
-
-            close(fdSocket);
-            close(fdChild);
-
-            execlp(worker.c_str(), worker.c_str(), "--slave", NULL);
-
-            throw SysError(format("executing `%1%'") % worker);
-
-        } catch (std::exception & e) {
-            std::cerr << format("child error: %1%\n") % e.what();
-        }
-        quickExit(1);
-    }
-
-    fdChild.close();
-
-}
-
-
 void RemoteStore::connectToDaemon()
 {
     fdSocket = socket(PF_UNIX, SOCK_STREAM, 0);

src/nix-worker/nix-worker.cc

@@ -893,33 +893,15 @@ static void daemonLoop()
 
 void run(Strings args)
 {
-    bool slave = false;
     bool daemon = false;
 
     for (Strings::iterator i = args.begin(); i != args.end(); ) {
         string arg = *i++;
-        if (arg == "--slave") slave = true;
-        if (arg == "--daemon") daemon = true;
+        if (arg == "--daemon") /* ignored for backwards compatibility */;
     }
 
-    if (slave) {
-        /* This prevents us from receiving signals from the terminal
-           when we're running in setuid mode. */
-        if (setsid() == -1)
-            throw SysError(format("creating a new session"));
-
-        processConnection();
-    }
-
-    else if (daemon) {
-        if (setuidMode)
-            throw Error("daemon cannot be started in setuid mode");
-        chdir("/");
-        daemonLoop();
-    }
-
-    else
-        throw Error("must be run in either --slave or --daemon mode");
+    chdir("/");
+    daemonLoop();
 }
 
 

tests/remote-store.sh

@@ -1,11 +1,5 @@
 source common.sh
 
-echo '*** testing slave mode ***'
-clearStore
-clearManifests
-NIX_REMOTE_=slave $SHELL ./user-envs.sh
-
-echo '*** testing daemon mode ***'
 clearStore
 clearManifests
 startDaemon