From 3b72741f23a854d351db8c1d76a74c9255141873 Mon Sep 17 00:00:00 2001
From: Arthur Gautier <baloo@superbaloo.net>
Date: Wed, 8 Sep 2021 18:11:43 +0000
Subject: [PATCH] preloadNSS: load NSS before threads are started

preloadNSS is not thread-safe, this commit moves it before we start the
first thread.

Signed-off-by: Arthur Gautier <baloo@superbaloo.net>
---
 src/libmain/shared.cc                       | 30 ++++++++++++++++++
 src/libstore/build/local-derivation-goal.cc | 34 ---------------------
 2 files changed, 30 insertions(+), 34 deletions(-)

diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index 3a9529c4d..85f9f0d58 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -15,6 +15,9 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <signal.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
 
 #include <openssl/crypto.h>
 
@@ -110,6 +113,31 @@ static void opensslLockCallback(int mode, int type, const char * file, int line)
 }
 #endif
 
+static std::once_flag dns_resolve_flag;
+
+static void preloadNSS() {
+    /* builtin:fetchurl can trigger a DNS lookup, which with glibc can trigger a dynamic library load of
+       one of the glibc NSS libraries in a sandboxed child, which will fail unless the library's already
+       been loaded in the parent. So we force a lookup of an invalid domain to force the NSS machinery to
+       load its lookup libraries in the parent before any child gets a chance to. */
+    std::call_once(dns_resolve_flag, []() {
+        struct addrinfo *res = NULL;
+
+        /* nss will only force the "local" (not through nscd) dns resolution if its on the LOCALDOMAIN.
+           We need the resolution to be done locally, as nscd socket will not be accessible in the
+           sandbox. */
+        char * previous_env = getenv("LOCALDOMAIN");
+        setenv("LOCALDOMAIN", "invalid", 1);
+        if (getaddrinfo("this.pre-initializes.the.dns.resolvers.invalid.", "http", NULL, &res) == 0) {
+            if (res) freeaddrinfo(res);
+        }
+        if (previous_env) {
+             setenv("LOCALDOMAIN", previous_env, 1);
+        } else {
+             unsetenv("LOCALDOMAIN");
+        }
+    });
+}
 
 static void sigHandler(int signo) { }
 
@@ -176,6 +204,8 @@ void initNix()
     if (hasPrefix(getEnv("TMPDIR").value_or("/tmp"), "/var/folders/"))
         unsetenv("TMPDIR");
 #endif
+
+    preloadNSS();
 }
 
 
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 2dcbedd4a..5cc0691e8 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -17,10 +17,7 @@
 #include <regex>
 #include <queue>
 
-#include <sys/types.h>
-#include <sys/socket.h>
 #include <sys/un.h>
-#include <netdb.h>
 #include <fcntl.h>
 #include <termios.h>
 #include <unistd.h>
@@ -34,7 +31,6 @@
 
 /* Includes required for chroot support. */
 #if __linux__
-#include <sys/socket.h>
 #include <sys/ioctl.h>
 #include <net/if.h>
 #include <netinet/ip.h>
@@ -344,33 +340,6 @@ int childEntry(void * arg)
 }
 
 
-static std::once_flag dns_resolve_flag;
-
-static void preloadNSS() {
-    /* builtin:fetchurl can trigger a DNS lookup, which with glibc can trigger a dynamic library load of
-       one of the glibc NSS libraries in a sandboxed child, which will fail unless the library's already
-       been loaded in the parent. So we force a lookup of an invalid domain to force the NSS machinery to
-       load its lookup libraries in the parent before any child gets a chance to. */
-    std::call_once(dns_resolve_flag, []() {
-        struct addrinfo *res = NULL;
-
-        /* nss will only force the "local" (not through nscd) dns resolution if its on the LOCALDOMAIN.
-           We need the resolution to be done locally, as nscd socket will not be accessible in the
-           sandbox. */
-        char * previous_env = getenv("LOCALDOMAIN");
-        setenv("LOCALDOMAIN", "invalid", 1);
-        if (getaddrinfo("this.pre-initializes.the.dns.resolvers.invalid.", "http", NULL, &res) == 0) {
-            if (res) freeaddrinfo(res);
-        }
-        if (previous_env) {
-             setenv("LOCALDOMAIN", previous_env, 1);
-        } else {
-             unsetenv("LOCALDOMAIN");
-        }
-    });
-}
-
-
 static void linkOrCopy(const Path & from, const Path & to)
 {
     if (link(from.c_str(), to.c_str()) == -1) {
@@ -399,9 +368,6 @@ void LocalDerivationGoal::startBuilder()
             settings.thisSystem,
             concatStringsSep<StringSet>(", ", worker.store.systemFeatures));
 
-    if (drv->isBuiltin())
-        preloadNSS();
-
 #if __APPLE__
     additionalSandboxProfile = parsedDrv->getStringAttr("__sandboxProfile").value_or("");
 #endif