From d43a8b25f044dffdbdd94777924e270cae3e0c8f Mon Sep 17 00:00:00 2001 From: Dan Peebles Date: Tue, 23 Jan 2018 14:13:30 -0500 Subject: [PATCH] Fix obscure corner case in name resolution for builtin:fetchurl in sandboxed environments --- src/libstore/build.cc | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/src/libstore/build.cc b/src/libstore/build.cc index 55066205d..cca51f17e 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -6,6 +6,7 @@ #include "archive.hh" #include "affinity.hh" #include "builtins.hh" +#include "download.hh" #include "finally.hh" #include "compression.hh" #include "json.hh" @@ -1777,6 +1778,19 @@ PathSet exportReferences(Store & store, PathSet storePaths) return paths; } +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 download of an invalid URL 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, []() { + DownloadRequest request("http://this.pre-initializes.the.dns.resolvers.invalid"); + request.tries = 1; // We only need to do it once, and this also suppresses an annoying warning + try { getDownloader()->download(request); } catch (...) {} + }); +} void DerivationGoal::startBuilder() { @@ -1787,6 +1801,9 @@ void DerivationGoal::startBuilder() % drv->platform % settings.thisSystem % drvPath); } + if (drv->isBuiltin()) + preloadNSS(); + #if __APPLE__ additionalSandboxProfile = get(drv->env, "__sandboxProfile"); #endif