360 lines
11 KiB
C++
360 lines
11 KiB
C++
#include "command.hh"
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#include "shared.hh"
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#include "local-store.hh"
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#include "remote-store.hh"
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#include "util.hh"
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#include "serialise.hh"
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#include "archive.hh"
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#include "globals.hh"
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#include "derivations.hh"
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#include "finally.hh"
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#include "legacy.hh"
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#include "daemon.hh"
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#include <algorithm>
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#include <climits>
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#include <cstring>
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#include <unistd.h>
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#include <signal.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/stat.h>
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#include <sys/socket.h>
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#include <sys/un.h>
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#include <errno.h>
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#include <pwd.h>
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#include <grp.h>
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#include <fcntl.h>
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#if __APPLE__ || __FreeBSD__
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#include <sys/ucred.h>
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#endif
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using namespace nix;
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using namespace nix::daemon;
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#ifndef __linux__
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#define SPLICE_F_MOVE 0
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static ssize_t splice(int fd_in, void *off_in, int fd_out, void *off_out, size_t len, unsigned int flags)
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{
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// We ignore most parameters, we just have them for conformance with the linux syscall
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std::vector<char> buf(8192);
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auto read_count = read(fd_in, buf.data(), buf.size());
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if (read_count == -1)
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return read_count;
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auto write_count = decltype(read_count)(0);
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while (write_count < read_count) {
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auto res = write(fd_out, buf.data() + write_count, read_count - write_count);
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if (res == -1)
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return res;
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write_count += res;
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}
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return read_count;
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}
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#endif
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static void sigChldHandler(int sigNo)
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{
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// Ensure we don't modify errno of whatever we've interrupted
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auto saved_errno = errno;
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// Reap all dead children.
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while (waitpid(-1, 0, WNOHANG) > 0) ;
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errno = saved_errno;
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}
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static void setSigChldAction(bool autoReap)
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{
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struct sigaction act, oact;
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act.sa_handler = autoReap ? sigChldHandler : SIG_DFL;
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sigfillset(&act.sa_mask);
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act.sa_flags = 0;
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if (sigaction(SIGCHLD, &act, &oact))
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throw SysError("setting SIGCHLD handler");
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}
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bool matchUser(const std::string & user, const std::string & group, const Strings & users)
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{
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if (find(users.begin(), users.end(), "*") != users.end())
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return true;
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if (find(users.begin(), users.end(), user) != users.end())
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return true;
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for (auto & i : users)
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if (i.substr(0, 1) == "@") {
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if (group == i.substr(1)) return true;
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struct group * gr = getgrnam(i.c_str() + 1);
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if (!gr) continue;
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for (char * * mem = gr->gr_mem; *mem; mem++)
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if (user == std::string(*mem)) return true;
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}
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return false;
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}
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struct PeerInfo
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{
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bool pidKnown;
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pid_t pid;
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bool uidKnown;
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uid_t uid;
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bool gidKnown;
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gid_t gid;
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};
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// Get the identity of the caller, if possible.
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static PeerInfo getPeerInfo(int remote)
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{
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PeerInfo peer = { false, 0, false, 0, false, 0 };
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#if defined(SO_PEERCRED)
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ucred cred;
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socklen_t credLen = sizeof(cred);
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if (getsockopt(remote, SOL_SOCKET, SO_PEERCRED, &cred, &credLen) == -1)
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throw SysError("getting peer credentials");
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peer = { true, cred.pid, true, cred.uid, true, cred.gid };
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#elif defined(LOCAL_PEERCRED)
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#if !defined(SOL_LOCAL)
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#define SOL_LOCAL 0
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#endif
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xucred cred;
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socklen_t credLen = sizeof(cred);
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if (getsockopt(remote, SOL_LOCAL, LOCAL_PEERCRED, &cred, &credLen) == -1)
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throw SysError("getting peer credentials");
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peer = { false, 0, true, cred.cr_uid, false, 0 };
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#endif
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return peer;
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}
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#define SD_LISTEN_FDS_START 3
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static ref<Store> openUncachedStore()
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{
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Store::Params params; // FIXME: get params from somewhere
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// Disable caching since the client already does that.
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params["path-info-cache-size"] = "0";
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return openStore(settings.storeUri, params);
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}
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static void daemonLoop()
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{
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if (chdir("/") == -1)
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throw SysError("cannot change current directory");
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AutoCloseFD fdSocket;
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// Handle socket-based activation by systemd.
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auto listenFds = getEnv("LISTEN_FDS");
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if (listenFds) {
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if (getEnv("LISTEN_PID") != std::to_string(getpid()) || listenFds != "1")
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throw Error("unexpected systemd environment variables");
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fdSocket = SD_LISTEN_FDS_START;
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closeOnExec(fdSocket.get());
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}
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// Otherwise, create and bind to a Unix domain socket.
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else {
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createDirs(dirOf(settings.nixDaemonSocketFile));
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fdSocket = createUnixDomainSocket(settings.nixDaemonSocketFile, 0666);
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}
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// Get rid of children automatically; don't let them become zombies.
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setSigChldAction(true);
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// Loop accepting connections.
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while (1) {
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try {
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// Accept a connection.
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struct sockaddr_un remoteAddr;
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socklen_t remoteAddrLen = sizeof(remoteAddr);
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AutoCloseFD remote = accept(fdSocket.get(),
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(struct sockaddr *) &remoteAddr, &remoteAddrLen);
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checkInterrupt();
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if (!remote) {
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if (errno == EINTR) continue;
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throw SysError("accepting connection");
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}
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closeOnExec(remote.get());
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TrustedFlag trusted = NotTrusted;
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PeerInfo peer = getPeerInfo(remote.get());
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struct passwd * pw = peer.uidKnown ? getpwuid(peer.uid) : 0;
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std::string user = pw ? pw->pw_name : std::to_string(peer.uid);
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struct group * gr = peer.gidKnown ? getgrgid(peer.gid) : 0;
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std::string group = gr ? gr->gr_name : std::to_string(peer.gid);
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Strings trustedUsers = settings.trustedUsers;
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Strings allowedUsers = settings.allowedUsers;
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if (matchUser(user, group, trustedUsers))
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trusted = Trusted;
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if ((!trusted && !matchUser(user, group, allowedUsers)) || group == settings.buildUsersGroup)
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throw Error("user '%1%' is not allowed to connect to the Nix daemon", user);
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printInfo(format((std::string) "accepted connection from pid %1%, user %2%" + (trusted ? " (trusted)" : ""))
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% (peer.pidKnown ? std::to_string(peer.pid) : "<unknown>")
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% (peer.uidKnown ? user : "<unknown>"));
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// Fork a child to handle the connection.
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ProcessOptions options;
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options.errorPrefix = "unexpected Nix daemon error: ";
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options.dieWithParent = false;
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options.runExitHandlers = true;
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options.allowVfork = false;
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startProcess([&]() {
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fdSocket = -1;
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// Background the daemon.
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if (setsid() == -1)
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throw SysError("creating a new session");
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// Restore normal handling of SIGCHLD.
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setSigChldAction(false);
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// For debugging, stuff the pid into argv[1].
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if (peer.pidKnown && savedArgv[1]) {
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auto processName = std::to_string(peer.pid);
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strncpy(savedArgv[1], processName.c_str(), strlen(savedArgv[1]));
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}
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// Handle the connection.
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FdSource from(remote.get());
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FdSink to(remote.get());
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processConnection(openUncachedStore(), from, to, trusted, NotRecursive, [&](Store & store) {
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#if 0
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/* Prevent users from doing something very dangerous. */
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if (geteuid() == 0 &&
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querySetting("build-users-group", "") == "")
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throw Error("if you run 'nix-daemon' as root, then you MUST set 'build-users-group'!");
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#endif
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store.createUser(user, peer.uid);
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});
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exit(0);
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}, options);
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} catch (Interrupted & e) {
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return;
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} catch (Error & error) {
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auto ei = error.info();
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// FIXME: add to trace?
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ei.msg = hintfmt("error processing connection: %1%", ei.msg.str());
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logError(ei);
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}
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}
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}
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static void runDaemon(bool stdio)
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{
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if (stdio) {
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if (auto store = openUncachedStore().dynamic_pointer_cast<RemoteStore>()) {
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auto conn = store->openConnectionWrapper();
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int from = conn->from.fd;
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int to = conn->to.fd;
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auto nfds = std::max(from, STDIN_FILENO) + 1;
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while (true) {
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fd_set fds;
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FD_ZERO(&fds);
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FD_SET(from, &fds);
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FD_SET(STDIN_FILENO, &fds);
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if (select(nfds, &fds, nullptr, nullptr, nullptr) == -1)
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throw SysError("waiting for data from client or server");
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if (FD_ISSET(from, &fds)) {
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auto res = splice(from, nullptr, STDOUT_FILENO, nullptr, SSIZE_MAX, SPLICE_F_MOVE);
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if (res == -1)
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throw SysError("splicing data from daemon socket to stdout");
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else if (res == 0)
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throw EndOfFile("unexpected EOF from daemon socket");
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}
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if (FD_ISSET(STDIN_FILENO, &fds)) {
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auto res = splice(STDIN_FILENO, nullptr, to, nullptr, SSIZE_MAX, SPLICE_F_MOVE);
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if (res == -1)
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throw SysError("splicing data from stdin to daemon socket");
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else if (res == 0)
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return;
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}
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}
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} else {
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FdSource from(STDIN_FILENO);
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FdSink to(STDOUT_FILENO);
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/* Auth hook is empty because in this mode we blindly trust the
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standard streams. Limiting access to those is explicitly
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not `nix-daemon`'s responsibility. */
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processConnection(openUncachedStore(), from, to, Trusted, NotRecursive, [&](Store & _){});
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}
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} else
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daemonLoop();
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}
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static int main_nix_daemon(int argc, char * * argv)
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{
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{
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auto stdio = false;
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parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
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if (*arg == "--daemon")
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; // ignored for backwards compatibility
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else if (*arg == "--help")
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showManPage("nix-daemon");
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else if (*arg == "--version")
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printVersion("nix-daemon");
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else if (*arg == "--stdio")
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stdio = true;
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else return false;
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return true;
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});
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runDaemon(stdio);
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return 0;
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}
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}
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static RegisterLegacyCommand r_nix_daemon("nix-daemon", main_nix_daemon);
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struct CmdDaemon : StoreCommand
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{
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std::string description() override
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{
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return "daemon to perform store operations on behalf of non-root clients";
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}
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Category category() override { return catUtility; }
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std::string doc() override
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{
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return
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#include "daemon.md"
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;
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}
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void run(ref<Store> store) override
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{
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runDaemon(false);
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}
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};
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static auto rCmdDaemon = registerCommand2<CmdDaemon>({"daemon"});
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