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Separate auth and logic for the daemon

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Before, processConnection wanted to know a user name and user id, and
`nix-daemon --stdio`, when it isn't proxying to an underlying daemon,
would just assume "root" and 0. But `nix-daemon --stdio` (no proxying)
shouldn't make guesses about who holds the other end of its standard
streams.

Now processConnection takes an "auth hook", so `nix-daemon` can provide
the appropriate policy and daemon.cc doesn't need to know or care what
it is.
This commit is contained in:
John Ericson 2020-08-12 15:14:56 +00:00
parent 574bf60b4d
commit 8d4162ff9e
5 changed files with 25 additions and 16 deletions
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3
src/libstore/build.cc
View file

@ -2920,7 +2920,8 @@ void DerivationGoal::startDaemon()
FdSink to(remote.get());
try {
daemon::processConnection(store, from, to,
daemon::NotTrusted, daemon::Recursive, "nobody", 65535);
daemon::NotTrusted, daemon::Recursive,
[&](Store & store) { store.createUser("nobody", 65535); });
debug("terminated daemon connection");
} catch (SysError &) {
ignoreException();

13
src/libstore/daemon.cc
View file

@ -817,8 +817,7 @@ void processConnection(
FdSink & to,
TrustedFlag trusted,
RecursiveFlag recursive,
const std::string & userName,
uid_t userId)
std::function<void(Store &)> authHook)
{
auto monitor = !recursive ? std::make_unique<MonitorFdHup>(from.fd) : nullptr;
@ -859,15 +858,7 @@ void processConnection(
/* If we can't accept clientVersion, then throw an error
*here* (not above). */
#if 0
/* Prevent users from doing something very dangerous. */
if (geteuid() == 0 &&
querySetting("build-users-group", "") == "")
throw Error("if you run 'nix-daemon' as root, then you MUST set 'build-users-group'!");
#endif
store->createUser(userName, userId);
authHook(*store);
tunnelLogger->stopWork();
to.flush();

7
src/libstore/daemon.hh
View file

@ -12,7 +12,10 @@ void processConnection(
FdSink & to,
TrustedFlag trusted,
RecursiveFlag recursive,
const std::string & userName,
uid_t userId);
/* Arbitrary hook to check authorization / initialize user data / whatever
after the protocol has been negotiated. The idea is that this function
and everything it calls doesn't know about this stuff, and the
`nix-daemon` handles that instead. */
std::function<void(Store &)> authHook);
}

15
src/nix-daemon/nix-daemon.cc
View file

@ -239,7 +239,15 @@ static void daemonLoop(char * * argv)
// Handle the connection.
FdSource from(remote.get());
FdSink to(remote.get());
processConnection(openUncachedStore(), from, to, trusted, NotRecursive, user, peer.uid);
processConnection(openUncachedStore(), from, to, trusted, NotRecursive, [&](Store & store) {
#if 0
/* Prevent users from doing something very dangerous. */
if (geteuid() == 0 &&
querySetting("build-users-group", "") == "")
throw Error("if you run 'nix-daemon' as root, then you MUST set 'build-users-group'!");
#endif
store.createUser(user, peer.uid);
});
exit(0);
}, options);
@ -324,7 +332,10 @@ static int _main(int argc, char * * argv)
} else {
FdSource from(STDIN_FILENO);
FdSink to(STDOUT_FILENO);
processConnection(openUncachedStore(), from, to, Trusted, NotRecursive, "root", 0);
/* Auth hook is empty because in this mode we blindly trust the
standard streams. Limitting access to thoses is explicitly
not `nix-daemon`'s responsibility. */
processConnection(openUncachedStore(), from, to, Trusted, NotRecursive, [&](Store & _){});
}
} else {
daemonLoop(argv);

3
tests/remote-store.sh
View file

@ -2,6 +2,9 @@ source common.sh
clearStore
# Ensure "fake ssh" remote store works just as legacy fake ssh would.
nix --store ssh-ng://localhost?remote-store=$TEST_ROOT/other-store doctor
startDaemon
storeCleared=1 NIX_REMOTE_=$NIX_REMOTE $SHELL ./user-envs.sh