systemctl: support remote and privileged systemctl access via SSH and pkexec

This adds support for executing systemctl operations remotely or as
privileged user while still running systemctl itself unprivileged and
locally.

This currently requires a D-Bus patch to work properly.

https://bugs.freedesktop.org/show_bug.cgi?id=35230

.gitignore

+systemd-stdio-bridge
 systemd-machine-id-setup
 systemd-detect-virt
 systemd-sysctl

Makefile.am

@@ -58,6 +58,7 @@ AM_CPPFLAGS = \
 	-DSYSTEMD_SHUTDOWN_BINARY_PATH=\"$(rootlibexecdir)/systemd-shutdown\" \
 	-DSYSTEMCTL_BINARY_PATH=\"$(rootbindir)/systemctl\" \
 	-DSYSTEMD_TTY_ASK_PASSWORD_AGENT_BINARY_PATH=\"$(rootbindir)/systemd-tty-ask-password-agent\" \
+        -DSYSTEMD_STDIO_BRIDGE_BINARY_PATH=\"$(bindir)/systemd-stdio-bridge\" \
 	-DRUNTIME_DIR=\"$(localstatedir)/run\" \
 	-DRANDOM_SEED=\"$(localstatedir)/lib/random-seed\" \
 	-DSYSTEMD_CRYPTSETUP_PATH=\"$(rootlibexecdir)/systemd-cryptsetup\" \
@@ -111,7 +112,8 @@ rootsbin_PROGRAMS = \
 	systemd-machine-id-setup
 
 bin_PROGRAMS = \
-	systemd-cgls
+	systemd-cgls \
+	systemd-stdio-bridge
 
 if HAVE_GTK
 bin_PROGRAMS += \
@@ -980,6 +982,12 @@ systemd_cgls_CFLAGS = \
 systemd_cgls_LDADD = \
 	libsystemd-basic.la
 
+systemd_stdio_bridge_SOURCES = \
+	src/bridge.c
+
+systemd_stdio_bridge_LDADD = \
+	libsystemd-basic.la
+
 systemadm_SOURCES = \
 	src/systemadm.vala \
 	src/systemd-interfaces.vala

TODO

@@ -26,6 +26,8 @@ Features:
 
 * optionally create watched directories in .path units
 
+* Support --test based on current system state
+
 * consider services with no [Install] section and stored in /lib enabled by "systemctl is-enabled"
 
 * consider services with any kind of link in /etc/systemd/system enabled

man/systemctl.xml

@@ -382,6 +382,27 @@
                                 file that shall be
                                 disabled.</para></listitem>
                         </varlistentry>
+
+                        <varlistentry>
+                                <term><option>-H</option></term>
+                                <term><option>--host</option></term>
+
+                                <listitem><para>Execute operation
+                                remotely. Specifiy a hostname, or
+                                username and hostname seperated by @,
+                                to connect to. This will use SSH to
+                                talk to the remote systemd
+                                instance.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><option>-P</option></term>
+                                <term><option>--privileged</option></term>
+
+                                <listitem><para>Acquire privileges via
+                                PolicyKit before executing the
+                                operation.</para></listitem>
+                        </varlistentry>
                 </variablelist>
 
                 <para>The following commands are understood:</para>

src/bridge.c

+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/epoll.h>
+#include <stddef.h>
+
+#include "log.h"
+#include "util.h"
+#include "socket-util.h"
+
+#define BUFFER_SIZE (64*1024)
+#define EXTRA_SIZE 16
+
+static bool initial_nul = false;
+static bool auth_over = false;
+
+static void format_uid(char *buf, size_t l) {
+        char text[20 + 1]; /* enough space for a 64bit integer plus NUL */
+        unsigned j;
+
+        assert(l > 0);
+
+        snprintf(text, sizeof(text)-1, "%llu", (unsigned long long) geteuid());
+        text[sizeof(text)-1] = 0;
+
+        memset(buf, 0, l);
+
+        for (j = 0; text[j] && j*2+2 < l; j++) {
+                buf[j*2]   = hexchar(text[j] >> 4);
+                buf[j*2+1] = hexchar(text[j] & 0xF);
+        }
+
+        buf[j*2] = 0;
+}
+
+static size_t patch_in_line(char *line, size_t l, size_t left) {
+        size_t r;
+
+        if (line[0] == 0 && !initial_nul) {
+                initial_nul = true;
+                line += 1;
+                l -= 1;
+                r = 1;
+        } else
+                r = 0;
+
+        if (l == 5 && strncmp(line, "BEGIN", 5) == 0) {
+                r += l;
+                auth_over = true;
+
+        } else if (l == 17 && strncmp(line, "NEGOTIATE_UNIX_FD", 17) == 0) {
+                memmove(line + 13, line + 17, left);
+                memcpy(line, "NEGOTIATE_NOP", 13);
+                r += 13;
+
+        } else if (l >= 14 && strncmp(line, "AUTH EXTERNAL ", 14) == 0) {
+                char uid[20*2 + 1];
+                size_t len;
+
+                format_uid(uid, sizeof(uid));
+                len = strlen(uid);
+                assert(len <= EXTRA_SIZE);
+
+                memmove(line + 14 + len, line + l, left);
+                memcpy(line + 14, uid, len);
+
+                r += 14 + len;
+        } else
+                r += l;
+
+        return r;
+}
+
+static size_t patch_in_buffer(char* in_buffer, size_t *in_buffer_full) {
+        size_t i, good = 0;
+
+        if (*in_buffer_full <= 0)
+                return *in_buffer_full;
+
+        /* If authentication is done, we don't touch anything anymore */
+        if (auth_over)
+                return *in_buffer_full;
+
+        if (*in_buffer_full < 2)
+                return 0;
+
+        for (i = 0; i <= *in_buffer_full - 2; i ++) {
+
+                /* Fully lines can be send on */
+                if (in_buffer[i] == '\r' && in_buffer[i+1] == '\n') {
+                        if (i > good) {
+                                size_t old_length, new_length;
+
+                                old_length = i - good;
+                                new_length = patch_in_line(in_buffer+good, old_length, *in_buffer_full - i);
+                                *in_buffer_full = *in_buffer_full + new_length - old_length;
+
+                                good += new_length + 2;
+
+                        } else
+                                good = i+2;
+                }
+
+                if (auth_over)
+                        break;
+        }
+
+        return good;
+}
+
+int main(int argc, char *argv[]) {
+        int r = EXIT_FAILURE, fd = -1, ep = -1;
+        union sockaddr_union sa;
+        char in_buffer[BUFFER_SIZE+EXTRA_SIZE], out_buffer[BUFFER_SIZE+EXTRA_SIZE];
+        size_t in_buffer_full = 0, out_buffer_full = 0;
+        struct epoll_event stdin_ev, stdout_ev, fd_ev;
+        bool stdin_readable = false, stdout_writable = false, fd_readable = false, fd_writable = false;
+        bool stdin_rhup = false, stdout_whup = false, fd_rhup = false, fd_whup = false;
+
+        if (argc > 1) {
+                log_error("This program takes no argument.");
+                return EXIT_FAILURE;
+        }
+
+        log_set_target(LOG_TARGET_SYSLOG_OR_KMSG);
+        log_parse_environment();
+        log_open();
+
+        if ((fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0)) < 0) {
+                log_error("Failed to create socket: %s", strerror(errno));
+                goto finish;
+        }
+
+        zero(sa);
+        sa.un.sun_family = AF_UNIX;
+        strncpy(sa.un.sun_path, "/var/run/dbus/system_bus_socket", sizeof(sa.un.sun_path));
+
+        if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + 1 + strlen(sa.un.sun_path+1)) < 0) {
+                log_error("Failed to connect: %m");
+                goto finish;
+        }
+
+        fd_nonblock(STDIN_FILENO, 1);
+        fd_nonblock(STDOUT_FILENO, 1);
+
+        if ((ep = epoll_create1(EPOLL_CLOEXEC)) < 0) {
+                log_error("Failed to create epoll: %m");
+                goto finish;
+        }
+
+        zero(stdin_ev);
+        stdin_ev.events = EPOLLIN|EPOLLET;
+        stdin_ev.data.fd = STDIN_FILENO;
+
+        zero(stdout_ev);
+        stdout_ev.events = EPOLLOUT|EPOLLET;
+        stdout_ev.data.fd = STDOUT_FILENO;
+
+        zero(fd_ev);
+        fd_ev.events = EPOLLIN|EPOLLOUT|EPOLLET;
+        fd_ev.data.fd = fd;
+
+        if (epoll_ctl(ep, EPOLL_CTL_ADD, STDIN_FILENO, &stdin_ev) < 0 ||
+            epoll_ctl(ep, EPOLL_CTL_ADD, STDOUT_FILENO, &stdout_ev) < 0 ||
+            epoll_ctl(ep, EPOLL_CTL_ADD, fd, &fd_ev) < 0) {
+                log_error("Failed to regiser fds in epoll: %m");
+                goto finish;
+        }
+
+        do {
+                struct epoll_event ev[16];
+                ssize_t k;
+                int i, nfds;
+
+                if ((nfds = epoll_wait(ep, ev, ELEMENTSOF(ev), -1)) < 0) {
+
+                        if (errno == EINTR || errno == EAGAIN)
+                                continue;
+
+                        log_error("epoll_wait(): %m");
+                        goto finish;
+                }
+
+                assert(nfds >= 1);
+
+                for (i = 0; i < nfds; i++) {
+                        if (ev[i].data.fd == STDIN_FILENO) {
+
+                                if (!stdin_rhup && (ev[i].events & (EPOLLHUP|EPOLLIN)))
+                                        stdin_readable = true;
+
+                        } else if (ev[i].data.fd == STDOUT_FILENO) {
+
+                                if (ev[i].events & EPOLLHUP) {
+                                        stdout_writable = false;
+                                        stdout_whup = true;
+                                }
+
+                                if (!stdout_whup && (ev[i].events & EPOLLOUT))
+                                        stdout_writable = true;
+
+                        } else if (ev[i].data.fd == fd) {
+
+                                if (ev[i].events & EPOLLHUP) {
+                                        fd_writable = false;
+                                        fd_whup = true;
+                                }
+
+                                if (!fd_rhup && (ev[i].events & (EPOLLHUP|EPOLLIN)))
+                                        fd_readable = true;
+
+                                if (!fd_whup && (ev[i].events & EPOLLOUT))
+                                        fd_writable = true;
+                        }
+                }
+
+                while ((stdin_readable && in_buffer_full <= 0) ||
+                       (fd_writable && patch_in_buffer(in_buffer, &in_buffer_full) > 0) ||
+                       (fd_readable && out_buffer_full <= 0) ||
+                       (stdout_writable && out_buffer_full > 0)) {
+
+                        size_t in_buffer_good = 0;
+
+                        if (stdin_readable && in_buffer_full < BUFFER_SIZE) {
+
+                                if ((k = read(STDIN_FILENO, in_buffer + in_buffer_full, BUFFER_SIZE - in_buffer_full)) < 0) {
+
+                                        if (errno == EAGAIN)
+                                                stdin_readable = false;
+                                        else if (errno == EPIPE || errno == ECONNRESET)
+                                                k = 0;
+                                        else {
+                                                log_error("read(): %m");
+                                                goto finish;
+                                        }
+                                } else
+                                        in_buffer_full += (size_t) k;
+
+                                if (k == 0) {
+                                        stdin_rhup = true;
+                                        stdin_readable = false;
+                                        shutdown(STDIN_FILENO, SHUT_RD);
+                                        close_nointr_nofail(STDIN_FILENO);
+                                }
+                        }
+
+                        in_buffer_good = patch_in_buffer(in_buffer, &in_buffer_full);
+
+                        if (fd_writable && in_buffer_good > 0) {
+
+                                if ((k = write(fd, in_buffer, in_buffer_good)) < 0) {
+
+                                        if (errno == EAGAIN)
+                                                fd_writable = false;
+                                        else if (errno == EPIPE || errno == ECONNRESET) {
+                                                fd_whup = true;
+                                                fd_writable = false;
+                                                shutdown(fd, SHUT_WR);
+                                        } else {
+                                                log_error("write(): %m");
+                                                goto finish;
+                                        }
+
+                                } else {
+                                        assert(in_buffer_full >= (size_t) k);
+                                        memmove(in_buffer, in_buffer + k, in_buffer_full - k);
+                                        in_buffer_full -= k;
+                                }
+                        }
+
+                        if (fd_readable && out_buffer_full < BUFFER_SIZE) {
+
+                                if ((k = read(fd, out_buffer + out_buffer_full, BUFFER_SIZE - out_buffer_full)) < 0) {
+
+                                        if (errno == EAGAIN)
+                                                fd_readable = false;
+                                        else if (errno == EPIPE || errno == ECONNRESET)
+                                                k = 0;
+                                        else {
+                                                log_error("read(): %m");
+                                                goto finish;
+                                        }
+                                }  else
+                                        out_buffer_full += (size_t) k;
+
+                                if (k == 0) {
+                                        fd_rhup = true;
+                                        fd_readable = false;
+                                        shutdown(fd, SHUT_RD);
+                                }
+                        }
+
+                        if (stdout_writable && out_buffer_full > 0) {
+
+                                if ((k = write(STDOUT_FILENO, out_buffer, out_buffer_full)) < 0) {
+
+                                        if (errno == EAGAIN)
+                                                stdout_writable = false;
+                                        else if (errno == EPIPE || errno == ECONNRESET) {
+                                                stdout_whup = true;
+                                                stdout_writable = false;
+                                                shutdown(STDOUT_FILENO, SHUT_WR);
+                                                close_nointr(STDOUT_FILENO);
+                                        } else {
+                                                log_error("write(): %m");
+                                                goto finish;
+                                        }
+
+                                } else {
+                                        assert(out_buffer_full >= (size_t) k);
+                                        memmove(out_buffer, out_buffer + k, out_buffer_full - k);
+                                        out_buffer_full -= k;
+                                }
+                        }
+                }
+
+                if (stdin_rhup && in_buffer_full <= 0 && !fd_whup) {
+                        fd_whup = true;
+                        fd_writable = false;
+                        shutdown(fd, SHUT_WR);
+                }
+
+                if (fd_rhup && out_buffer_full <= 0 && !stdout_whup) {
+                        stdout_whup = true;
+                        stdout_writable = false;
+                        shutdown(STDOUT_FILENO, SHUT_WR);
+                        close_nointr(STDOUT_FILENO);
+                }
+
+        } while (!stdout_whup || !fd_whup);
+
+        r = EXIT_SUCCESS;
+
+finish:
+        if (fd >= 0)
+                close_nointr_nofail(fd);
+
+        if (ep >= 0)
+                close_nointr_nofail(ep);
+
+        return r;
+}

src/dbus-common.c

@@ -23,6 +23,8 @@
 #include <sys/socket.h>
 #include <errno.h>
 #include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <dbus/dbus.h>
 
 #include "log.h"
@@ -55,59 +57,63 @@ int bus_check_peercred(DBusConnection *c) {
         return 1;
 }
 
-int bus_connect(DBusBusType t, DBusConnection **_bus, bool *private, DBusError *error) {
-        DBusConnection *bus;
+#define TIMEOUT_USEC (60*USEC_PER_SEC)
 
-        assert(_bus);
+static int sync_auth(DBusConnection *bus, DBusError *error) {
+        usec_t begin, tstamp;
 
-#define TIMEOUT_USEC (60*USEC_PER_SEC)
+        assert(bus);
 
-        /* If we are root, then let's not go via the bus */
-        if (geteuid() == 0 && t == DBUS_BUS_SYSTEM) {
-                usec_t begin, tstamp;
+        /* This complexity should probably move into D-Bus itself:
+         *
+         * https://bugs.freedesktop.org/show_bug.cgi?id=35189 */
 
-                if (!(bus = dbus_connection_open_private("unix:abstract=/org/freedesktop/systemd1/private", error)))
-                        return -EIO;
+        begin = tstamp = now(CLOCK_MONOTONIC);
+        for (;;) {
 
-                if (bus_check_peercred(bus) < 0) {
-                        dbus_connection_close(bus);
-                        dbus_connection_unref(bus);
+                if (tstamp > begin + TIMEOUT_USEC)
+                        break;
 
-                        dbus_set_error_const(error, DBUS_ERROR_ACCESS_DENIED, "Failed to verify owner of bus.");
-                        return -EACCES;
-                }
+                if (dbus_connection_get_is_authenticated(bus))
+                        break;
 
-                /* This complexity should probably move into D-Bus itself:
-                 *
-                 * https://bugs.freedesktop.org/show_bug.cgi?id=35189 */
-                begin = tstamp = now(CLOCK_MONOTONIC);
-                for (;;) {
+                if (!dbus_connection_read_write_dispatch(bus, ((begin + TIMEOUT_USEC - tstamp) + USEC_PER_MSEC - 1) / USEC_PER_MSEC))
+                        break;
 
-                        if (tstamp > begin + TIMEOUT_USEC)
-                                break;
+                tstamp = now(CLOCK_MONOTONIC);
+        }
 
-                        if (dbus_connection_get_is_authenticated(bus))
-                                break;
+        if (!dbus_connection_get_is_connected(bus)) {
+                dbus_set_error_const(error, DBUS_ERROR_NO_SERVER, "Connection terminated during authentication.");
+                return -ECONNREFUSED;
+        }
 
-                        if (!dbus_connection_read_write_dispatch(bus, ((begin + TIMEOUT_USEC - tstamp) + USEC_PER_MSEC - 1) / USEC_PER_MSEC))
-                                break;
+        if (!dbus_connection_get_is_authenticated(bus)) {
+                dbus_set_error_const(error, DBUS_ERROR_TIMEOUT, "Failed to authenticate in time.");
+                return -EACCES;
+        }
 
-                        tstamp = now(CLOCK_MONOTONIC);
-                }
+        return 0;
+}
 
-                if (!dbus_connection_get_is_connected(bus)) {
-                        dbus_connection_close(bus);
-                        dbus_connection_unref(bus);
+int bus_connect(DBusBusType t, DBusConnection **_bus, bool *private, DBusError *error) {
+        DBusConnection *bus;
+        int r;
 
-                        dbus_set_error_const(error, DBUS_ERROR_NO_SERVER, "Connection terminated during authentication.");
-                        return -ECONNREFUSED;
-                }
+        assert(_bus);
 
-                if (!dbus_connection_get_is_authenticated(bus)) {
+        /* If we are root, then let's not go via the bus */
+        if (geteuid() == 0 && t == DBUS_BUS_SYSTEM) {
+                if (!(bus = dbus_connection_open_private("unix:abstract=/org/freedesktop/systemd1/private", error)))
+                        return -EIO;
+
+                dbus_connection_set_exit_on_disconnect(bus, FALSE);
+
+                if (bus_check_peercred(bus) < 0) {
                         dbus_connection_close(bus);
                         dbus_connection_unref(bus);
 
-                        dbus_set_error_const(error, DBUS_ERROR_TIMEOUT, "Failed to authenticate in time.");
+                        dbus_set_error_const(error, DBUS_ERROR_ACCESS_DENIED, "Failed to verify owner of bus.");
                         return -EACCES;
                 }
 
@@ -118,12 +124,93 @@ int bus_connect(DBusBusType t, DBusConnection **_bus, bool *private, DBusError *
                 if (!(bus = dbus_bus_get_private(t, error)))
                         return -EIO;
 
+                dbus_connection_set_exit_on_disconnect(bus, FALSE);
+
                 if (private)
                         *private = false;
         }
 
+        if ((r = sync_auth(bus, error)) < 0) {
+                dbus_connection_close(bus);
+                dbus_connection_unref(bus);
+                return r;
+        }
+
+        *_bus = bus;
+        return 0;
+}
+
+int bus_connect_system_ssh(const char *user, const char *host, DBusConnection **_bus, DBusError *error) {
+        DBusConnection *bus;
+        char *p = NULL;
+        int r;
+
+        assert(_bus);
+        assert(user || host);
+
+        if (user && host)
+                asprintf(&p, "exec:path=ssh,argv1=-xT,argv2=%s@%s,argv3=systemd-stdio-bridge", user, host);
+        else if (user)
+                asprintf(&p, "exec:path=ssh,argv1=-xT,argv2=%s@localhost,argv3=systemd-stdio-bridge", user);
+        else if (host)
+                asprintf(&p, "exec:path=ssh,argv1=-xT,argv2=%s,argv3=systemd-stdio-bridge", host);
+
+        if (!p) {
+                dbus_set_error_const(error, DBUS_ERROR_NO_MEMORY, NULL);
+                return -ENOMEM;
+        }
+
+        bus = dbus_connection_open_private(p, error);
+        free(p);
+
+        if (!bus)
+                return -EIO;
+
+        dbus_connection_set_exit_on_disconnect(bus, FALSE);
+
+        if ((r = sync_auth(bus, error)) < 0) {
+                dbus_connection_close(bus);
+                dbus_connection_unref(bus);
+                return r;
+        }
+
+        if (!dbus_bus_register(bus, error)) {
+                dbus_connection_close(bus);
+                dbus_connection_unref(bus);
+                return r;
+        }
+
+        *_bus = bus;
+        return 0;
+}
+
+int bus_connect_system_polkit(DBusConnection **_bus, DBusError *error) {
+        DBusConnection *bus;
+        int r;
+
+        assert(_bus);
+
+        /* Don't bother with PolicyKit if we are root */
+        if (geteuid() == 0)
+                return bus_connect(DBUS_BUS_SYSTEM, _bus, NULL, error);
+
+        if (!(bus = dbus_connection_open_private("exec:path=pkexec,argv1=" SYSTEMD_STDIO_BRIDGE_BINARY_PATH, error)))
+                return -EIO;