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Fix obscure corner case in name resolution for builtin:fetchurl in sandboxed environments

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This commit is contained in:
Dan Peebles 2018-01-23 14:13:30 -05:00
parent c382866cd2
commit d43a8b25f0
1 changed files with 17 additions and 0 deletions
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17
src/libstore/build.cc
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@ -6,6 +6,7 @@
#include "archive.hh" #include "archive.hh"
#include "affinity.hh" #include "affinity.hh"
#include "builtins.hh" #include "builtins.hh"
#include "download.hh"
#include "finally.hh" #include "finally.hh"
#include "compression.hh" #include "compression.hh"
#include "json.hh" #include "json.hh"
@ -1777,6 +1778,19 @@ PathSet exportReferences(Store & store, PathSet storePaths)
return paths; 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() void DerivationGoal::startBuilder()
{ {
@ -1787,6 +1801,9 @@ void DerivationGoal::startBuilder()
% drv->platform % settings.thisSystem % drvPath); % drv->platform % settings.thisSystem % drvPath);
} }
if (drv->isBuiltin())
preloadNSS();
#if __APPLE__ #if __APPLE__
additionalSandboxProfile = get(drv->env, "__sandboxProfile"); additionalSandboxProfile = get(drv->env, "__sandboxProfile");
#endif #endif