forked from lix-project/lix
736b9cede7
The new `nix daemon` command didn't accept the same flags that `nix-daemon` did. * docs(daemon): clarify the daemon trust override flags * fix: change declaration order * docs: add examples of nix daemon usage * Apply suggestions from code review --------- Co-authored-by: Eelco Dolstra <edolstra@gmail.com> Co-authored-by: John Ericson <git@JohnEricson.me> Co-authored-by: tomberek <tomberek@users.noreply.github.com>
563 lines
17 KiB
C++
563 lines
17 KiB
C++
///@file
|
|
|
|
#include "command.hh"
|
|
#include "shared.hh"
|
|
#include "local-store.hh"
|
|
#include "remote-store.hh"
|
|
#include "remote-store-connection.hh"
|
|
#include "util.hh"
|
|
#include "serialise.hh"
|
|
#include "archive.hh"
|
|
#include "globals.hh"
|
|
#include "derivations.hh"
|
|
#include "finally.hh"
|
|
#include "legacy.hh"
|
|
#include "daemon.hh"
|
|
|
|
#include <algorithm>
|
|
#include <climits>
|
|
#include <cstring>
|
|
|
|
#include <unistd.h>
|
|
#include <signal.h>
|
|
#include <sys/types.h>
|
|
#include <sys/wait.h>
|
|
#include <sys/stat.h>
|
|
#include <sys/socket.h>
|
|
#include <sys/un.h>
|
|
#include <sys/select.h>
|
|
#include <errno.h>
|
|
#include <pwd.h>
|
|
#include <grp.h>
|
|
#include <fcntl.h>
|
|
|
|
#if __APPLE__ || __FreeBSD__
|
|
#include <sys/ucred.h>
|
|
#endif
|
|
|
|
using namespace nix;
|
|
using namespace nix::daemon;
|
|
|
|
/**
|
|
* Settings related to authenticating clients for the Nix daemon.
|
|
*
|
|
* For pipes we have little good information about the client side, but
|
|
* for Unix domain sockets we do. So currently these options implemented
|
|
* mandatory access control based on user names and group names (looked
|
|
* up and translated to UID/GIDs in the CLI process that runs the code
|
|
* in this file).
|
|
*
|
|
* No code outside of this file knows about these settings (this is not
|
|
* exposed in a header); all authentication and authorization happens in
|
|
* `daemon.cc`.
|
|
*/
|
|
struct AuthorizationSettings : Config {
|
|
|
|
Setting<Strings> trustedUsers{
|
|
this, {"root"}, "trusted-users",
|
|
R"(
|
|
A list of user names, separated by whitespace.
|
|
These users will have additional rights when connecting to the Nix daemon, such as the ability to specify additional [substituters](#conf-substituters), or to import unsigned [NARs](@docroot@/glossary.md#gloss-nar).
|
|
|
|
You can also specify groups by prefixing names with `@`.
|
|
For instance, `@wheel` means all users in the `wheel` group.
|
|
|
|
> **Warning**
|
|
>
|
|
> Adding a user to `trusted-users` is essentially equivalent to giving that user root access to the system.
|
|
> For example, the user can access or replace store path contents that are critical for system security.
|
|
)"};
|
|
|
|
/**
|
|
* Who we trust to use the daemon in safe ways
|
|
*/
|
|
Setting<Strings> allowedUsers{
|
|
this, {"*"}, "allowed-users",
|
|
R"(
|
|
A list user names, separated by whitespace.
|
|
These users are allowed to connect to the Nix daemon.
|
|
|
|
You can specify groups by prefixing names with `@`.
|
|
For instance, `@wheel` means all users in the `wheel` group.
|
|
Also, you can allow all users by specifying `*`.
|
|
|
|
> **Note**
|
|
>
|
|
> Trusted users (set in [`trusted-users`](#conf-trusted-users)) can always connect to the Nix daemon.
|
|
)"};
|
|
};
|
|
|
|
AuthorizationSettings authorizationSettings;
|
|
|
|
static GlobalConfig::Register rSettings(&authorizationSettings);
|
|
|
|
#ifndef __linux__
|
|
#define SPLICE_F_MOVE 0
|
|
static ssize_t splice(int fd_in, void *off_in, int fd_out, void *off_out, size_t len, unsigned int flags)
|
|
{
|
|
// We ignore most parameters, we just have them for conformance with the linux syscall
|
|
std::vector<char> buf(8192);
|
|
auto read_count = read(fd_in, buf.data(), buf.size());
|
|
if (read_count == -1)
|
|
return read_count;
|
|
auto write_count = decltype(read_count)(0);
|
|
while (write_count < read_count) {
|
|
auto res = write(fd_out, buf.data() + write_count, read_count - write_count);
|
|
if (res == -1)
|
|
return res;
|
|
write_count += res;
|
|
}
|
|
return read_count;
|
|
}
|
|
#endif
|
|
|
|
|
|
static void sigChldHandler(int sigNo)
|
|
{
|
|
// Ensure we don't modify errno of whatever we've interrupted
|
|
auto saved_errno = errno;
|
|
// Reap all dead children.
|
|
while (waitpid(-1, 0, WNOHANG) > 0) ;
|
|
errno = saved_errno;
|
|
}
|
|
|
|
|
|
static void setSigChldAction(bool autoReap)
|
|
{
|
|
struct sigaction act, oact;
|
|
act.sa_handler = autoReap ? sigChldHandler : SIG_DFL;
|
|
sigfillset(&act.sa_mask);
|
|
act.sa_flags = 0;
|
|
if (sigaction(SIGCHLD, &act, &oact))
|
|
throw SysError("setting SIGCHLD handler");
|
|
}
|
|
|
|
/**
|
|
* @return Is the given user a member of this group?
|
|
*
|
|
* @param user User specified by username.
|
|
*
|
|
* @param group Group the user might be a member of.
|
|
*/
|
|
static bool matchUser(std::string_view user, const struct group & gr)
|
|
{
|
|
for (char * * mem = gr.gr_mem; *mem; mem++)
|
|
if (user == std::string_view(*mem)) return true;
|
|
return false;
|
|
}
|
|
|
|
|
|
/**
|
|
* Does the given user (specified by user name and primary group name)
|
|
* match the given user/group whitelist?
|
|
*
|
|
* If the list allows all users: Yes.
|
|
*
|
|
* If the username is in the set: Yes.
|
|
*
|
|
* If the groupname is in the set: Yes.
|
|
*
|
|
* If the user is in another group which is in the set: yes.
|
|
*
|
|
* Otherwise: No.
|
|
*/
|
|
static bool matchUser(const std::string & user, const std::string & group, const Strings & users)
|
|
{
|
|
if (find(users.begin(), users.end(), "*") != users.end())
|
|
return true;
|
|
|
|
if (find(users.begin(), users.end(), user) != users.end())
|
|
return true;
|
|
|
|
for (auto & i : users)
|
|
if (i.substr(0, 1) == "@") {
|
|
if (group == i.substr(1)) return true;
|
|
struct group * gr = getgrnam(i.c_str() + 1);
|
|
if (!gr) continue;
|
|
if (matchUser(user, *gr)) return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
|
|
struct PeerInfo
|
|
{
|
|
bool pidKnown;
|
|
pid_t pid;
|
|
bool uidKnown;
|
|
uid_t uid;
|
|
bool gidKnown;
|
|
gid_t gid;
|
|
};
|
|
|
|
|
|
/**
|
|
* Get the identity of the caller, if possible.
|
|
*/
|
|
static PeerInfo getPeerInfo(int remote)
|
|
{
|
|
PeerInfo peer = { false, 0, false, 0, false, 0 };
|
|
|
|
#if defined(SO_PEERCRED)
|
|
|
|
ucred cred;
|
|
socklen_t credLen = sizeof(cred);
|
|
if (getsockopt(remote, SOL_SOCKET, SO_PEERCRED, &cred, &credLen) == -1)
|
|
throw SysError("getting peer credentials");
|
|
peer = { true, cred.pid, true, cred.uid, true, cred.gid };
|
|
|
|
#elif defined(LOCAL_PEERCRED)
|
|
|
|
#if !defined(SOL_LOCAL)
|
|
#define SOL_LOCAL 0
|
|
#endif
|
|
|
|
xucred cred;
|
|
socklen_t credLen = sizeof(cred);
|
|
if (getsockopt(remote, SOL_LOCAL, LOCAL_PEERCRED, &cred, &credLen) == -1)
|
|
throw SysError("getting peer credentials");
|
|
peer = { false, 0, true, cred.cr_uid, false, 0 };
|
|
|
|
#endif
|
|
|
|
return peer;
|
|
}
|
|
|
|
|
|
#define SD_LISTEN_FDS_START 3
|
|
|
|
|
|
/**
|
|
* Open a store without a path info cache.
|
|
*/
|
|
static ref<Store> openUncachedStore()
|
|
{
|
|
Store::Params params; // FIXME: get params from somewhere
|
|
// Disable caching since the client already does that.
|
|
params["path-info-cache-size"] = "0";
|
|
return openStore(settings.storeUri, params);
|
|
}
|
|
|
|
/**
|
|
* Authenticate a potential client
|
|
*
|
|
* @param peer Information about other end of the connection, the client which
|
|
* wants to communicate with us.
|
|
*
|
|
* @return A pair of a `TrustedFlag`, whether the potential client is trusted,
|
|
* and the name of the user (useful for printing messages).
|
|
*
|
|
* If the potential client is not allowed to talk to us, we throw an `Error`.
|
|
*/
|
|
static std::pair<TrustedFlag, std::string> authPeer(const PeerInfo & peer)
|
|
{
|
|
TrustedFlag trusted = NotTrusted;
|
|
|
|
struct passwd * pw = peer.uidKnown ? getpwuid(peer.uid) : 0;
|
|
std::string user = pw ? pw->pw_name : std::to_string(peer.uid);
|
|
|
|
struct group * gr = peer.gidKnown ? getgrgid(peer.gid) : 0;
|
|
std::string group = gr ? gr->gr_name : std::to_string(peer.gid);
|
|
|
|
const Strings & trustedUsers = authorizationSettings.trustedUsers;
|
|
const Strings & allowedUsers = authorizationSettings.allowedUsers;
|
|
|
|
if (matchUser(user, group, trustedUsers))
|
|
trusted = Trusted;
|
|
|
|
if ((!trusted && !matchUser(user, group, allowedUsers)) || group == settings.buildUsersGroup)
|
|
throw Error("user '%1%' is not allowed to connect to the Nix daemon", user);
|
|
|
|
return { trusted, std::move(user) };
|
|
}
|
|
|
|
|
|
/**
|
|
* Run a server. The loop opens a socket and accepts new connections from that
|
|
* socket.
|
|
*
|
|
* @param forceTrustClientOpt If present, force trusting or not trusted
|
|
* the client. Otherwise, decide based on the authentication settings
|
|
* and user credentials (from the unix domain socket).
|
|
*/
|
|
static void daemonLoop(std::optional<TrustedFlag> forceTrustClientOpt)
|
|
{
|
|
if (chdir("/") == -1)
|
|
throw SysError("cannot change current directory");
|
|
|
|
AutoCloseFD fdSocket;
|
|
|
|
// Handle socket-based activation by systemd.
|
|
auto listenFds = getEnv("LISTEN_FDS");
|
|
if (listenFds) {
|
|
if (getEnv("LISTEN_PID") != std::to_string(getpid()) || listenFds != "1")
|
|
throw Error("unexpected systemd environment variables");
|
|
fdSocket = SD_LISTEN_FDS_START;
|
|
closeOnExec(fdSocket.get());
|
|
}
|
|
|
|
// Otherwise, create and bind to a Unix domain socket.
|
|
else {
|
|
createDirs(dirOf(settings.nixDaemonSocketFile));
|
|
fdSocket = createUnixDomainSocket(settings.nixDaemonSocketFile, 0666);
|
|
}
|
|
|
|
// Get rid of children automatically; don't let them become zombies.
|
|
setSigChldAction(true);
|
|
|
|
// Loop accepting connections.
|
|
while (1) {
|
|
|
|
try {
|
|
// Accept a connection.
|
|
struct sockaddr_un remoteAddr;
|
|
socklen_t remoteAddrLen = sizeof(remoteAddr);
|
|
|
|
AutoCloseFD remote = accept(fdSocket.get(),
|
|
(struct sockaddr *) &remoteAddr, &remoteAddrLen);
|
|
checkInterrupt();
|
|
if (!remote) {
|
|
if (errno == EINTR) continue;
|
|
throw SysError("accepting connection");
|
|
}
|
|
|
|
closeOnExec(remote.get());
|
|
|
|
PeerInfo peer { .pidKnown = false };
|
|
TrustedFlag trusted;
|
|
std::string user;
|
|
|
|
if (forceTrustClientOpt)
|
|
trusted = *forceTrustClientOpt;
|
|
else {
|
|
peer = getPeerInfo(remote.get());
|
|
auto [_trusted, _user] = authPeer(peer);
|
|
trusted = _trusted;
|
|
user = _user;
|
|
};
|
|
|
|
printInfo((std::string) "accepted connection from pid %1%, user %2%" + (trusted ? " (trusted)" : ""),
|
|
peer.pidKnown ? std::to_string(peer.pid) : "<unknown>",
|
|
peer.uidKnown ? user : "<unknown>");
|
|
|
|
// Fork a child to handle the connection.
|
|
ProcessOptions options;
|
|
options.errorPrefix = "unexpected Nix daemon error: ";
|
|
options.dieWithParent = false;
|
|
options.runExitHandlers = true;
|
|
options.allowVfork = false;
|
|
startProcess([&]() {
|
|
fdSocket = -1;
|
|
|
|
// Background the daemon.
|
|
if (setsid() == -1)
|
|
throw SysError("creating a new session");
|
|
|
|
// Restore normal handling of SIGCHLD.
|
|
setSigChldAction(false);
|
|
|
|
// For debugging, stuff the pid into argv[1].
|
|
if (peer.pidKnown && savedArgv[1]) {
|
|
auto processName = std::to_string(peer.pid);
|
|
strncpy(savedArgv[1], processName.c_str(), strlen(savedArgv[1]));
|
|
}
|
|
|
|
// Handle the connection.
|
|
FdSource from(remote.get());
|
|
FdSink to(remote.get());
|
|
processConnection(openUncachedStore(), from, to, trusted, NotRecursive);
|
|
|
|
exit(0);
|
|
}, options);
|
|
|
|
} catch (Interrupted & e) {
|
|
return;
|
|
} catch (Error & error) {
|
|
auto ei = error.info();
|
|
// FIXME: add to trace?
|
|
ei.msg = hintfmt("error processing connection: %1%", ei.msg.str());
|
|
logError(ei);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Forward a standard IO connection to the given remote store.
|
|
*
|
|
* We just act as a middleman blindly ferry output between the standard
|
|
* input/output and the remote store connection, not processing anything.
|
|
*
|
|
* Loops until standard input disconnects, or an error is encountered.
|
|
*/
|
|
static void forwardStdioConnection(RemoteStore & store) {
|
|
auto conn = store.openConnectionWrapper();
|
|
int from = conn->from.fd;
|
|
int to = conn->to.fd;
|
|
|
|
auto nfds = std::max(from, STDIN_FILENO) + 1;
|
|
while (true) {
|
|
fd_set fds;
|
|
FD_ZERO(&fds);
|
|
FD_SET(from, &fds);
|
|
FD_SET(STDIN_FILENO, &fds);
|
|
if (select(nfds, &fds, nullptr, nullptr, nullptr) == -1)
|
|
throw SysError("waiting for data from client or server");
|
|
if (FD_ISSET(from, &fds)) {
|
|
auto res = splice(from, nullptr, STDOUT_FILENO, nullptr, SSIZE_MAX, SPLICE_F_MOVE);
|
|
if (res == -1)
|
|
throw SysError("splicing data from daemon socket to stdout");
|
|
else if (res == 0)
|
|
throw EndOfFile("unexpected EOF from daemon socket");
|
|
}
|
|
if (FD_ISSET(STDIN_FILENO, &fds)) {
|
|
auto res = splice(STDIN_FILENO, nullptr, to, nullptr, SSIZE_MAX, SPLICE_F_MOVE);
|
|
if (res == -1)
|
|
throw SysError("splicing data from stdin to daemon socket");
|
|
else if (res == 0)
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Process a client connecting to us via standard input/output
|
|
*
|
|
* Unlike `forwardStdioConnection()` we do process commands ourselves in
|
|
* this case, not delegating to another daemon.
|
|
*
|
|
* @param trustClient Whether to trust the client. Forwarded directly to
|
|
* `processConnection()`.
|
|
*/
|
|
static void processStdioConnection(ref<Store> store, TrustedFlag trustClient)
|
|
{
|
|
FdSource from(STDIN_FILENO);
|
|
FdSink to(STDOUT_FILENO);
|
|
processConnection(store, from, to, trustClient, NotRecursive);
|
|
}
|
|
|
|
/**
|
|
* Entry point shared between the new CLI `nix daemon` and old CLI
|
|
* `nix-daemon`.
|
|
*
|
|
* @param forceTrustClientOpt See `daemonLoop()` and the parameter with
|
|
* the same name over there for details.
|
|
*/
|
|
static void runDaemon(bool stdio, std::optional<TrustedFlag> forceTrustClientOpt)
|
|
{
|
|
if (stdio) {
|
|
auto store = openUncachedStore();
|
|
|
|
// If --force-untrusted is passed, we cannot forward the connection and
|
|
// must process it ourselves (before delegating to the next store) to
|
|
// force untrusting the client.
|
|
if (auto remoteStore = store.dynamic_pointer_cast<RemoteStore>(); remoteStore && (!forceTrustClientOpt || *forceTrustClientOpt != NotTrusted))
|
|
forwardStdioConnection(*remoteStore);
|
|
else
|
|
// `Trusted` is passed in the auto (no override case) because we
|
|
// cannot see who is on the other side of a plain pipe. Limiting
|
|
// access to those is explicitly not `nix-daemon`'s responsibility.
|
|
processStdioConnection(store, forceTrustClientOpt.value_or(Trusted));
|
|
} else
|
|
daemonLoop(forceTrustClientOpt);
|
|
}
|
|
|
|
static int main_nix_daemon(int argc, char * * argv)
|
|
{
|
|
{
|
|
auto stdio = false;
|
|
std::optional<TrustedFlag> isTrustedOpt = std::nullopt;
|
|
|
|
parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
|
|
if (*arg == "--daemon")
|
|
; // ignored for backwards compatibility
|
|
else if (*arg == "--help")
|
|
showManPage("nix-daemon");
|
|
else if (*arg == "--version")
|
|
printVersion("nix-daemon");
|
|
else if (*arg == "--stdio")
|
|
stdio = true;
|
|
else if (*arg == "--force-trusted") {
|
|
experimentalFeatureSettings.require(Xp::DaemonTrustOverride);
|
|
isTrustedOpt = Trusted;
|
|
} else if (*arg == "--force-untrusted") {
|
|
experimentalFeatureSettings.require(Xp::DaemonTrustOverride);
|
|
isTrustedOpt = NotTrusted;
|
|
} else if (*arg == "--default-trust") {
|
|
experimentalFeatureSettings.require(Xp::DaemonTrustOverride);
|
|
isTrustedOpt = std::nullopt;
|
|
} else return false;
|
|
return true;
|
|
});
|
|
|
|
runDaemon(stdio, isTrustedOpt);
|
|
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
static RegisterLegacyCommand r_nix_daemon("nix-daemon", main_nix_daemon);
|
|
|
|
struct CmdDaemon : StoreCommand
|
|
{
|
|
bool stdio = false;
|
|
std::optional<TrustedFlag> isTrustedOpt = std::nullopt;
|
|
|
|
CmdDaemon()
|
|
{
|
|
addFlag({
|
|
.longName = "stdio",
|
|
.description = "Attach to standard I/O, instead of trying to bind to a UNIX socket.",
|
|
.handler = {&stdio, true},
|
|
});
|
|
|
|
addFlag({
|
|
.longName = "force-trusted",
|
|
.description = "Force the daemon to trust connecting clients.",
|
|
.handler = {[&]() {
|
|
isTrustedOpt = Trusted;
|
|
}},
|
|
.experimentalFeature = Xp::DaemonTrustOverride,
|
|
});
|
|
|
|
addFlag({
|
|
.longName = "force-untrusted",
|
|
.description = "Force the daemon to not trust connecting clients. The connection will be processed by the receiving daemon before forwarding commands.",
|
|
.handler = {[&]() {
|
|
isTrustedOpt = NotTrusted;
|
|
}},
|
|
.experimentalFeature = Xp::DaemonTrustOverride,
|
|
});
|
|
|
|
addFlag({
|
|
.longName = "default-trust",
|
|
.description = "Use Nix's default trust.",
|
|
.handler = {[&]() {
|
|
isTrustedOpt = std::nullopt;
|
|
}},
|
|
.experimentalFeature = Xp::DaemonTrustOverride,
|
|
});
|
|
}
|
|
|
|
std::string description() override
|
|
{
|
|
return "daemon to perform store operations on behalf of non-root clients";
|
|
}
|
|
|
|
Category category() override { return catUtility; }
|
|
|
|
std::string doc() override
|
|
{
|
|
return
|
|
#include "daemon.md"
|
|
;
|
|
}
|
|
|
|
void run(ref<Store> store) override
|
|
{
|
|
runDaemon(stdio, isTrustedOpt);
|
|
}
|
|
};
|
|
|
|
static auto rCmdDaemon = registerCommand2<CmdDaemon>({"daemon"});
|