src/getty-generator/getty-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2010 Lennart Poettering
   6
   7   systemd is free software; you can redistribute it and/or modify it
   8   under the terms of the GNU Lesser General Public License as published by
   9   the Free Software Foundation; either version 2.1 of the License, or
  10   (at your option) any later version.
  11
  12   systemd is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   Lesser General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  19 ***/
  20
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25
  26 #include "alloc-util.h"
  27 #include "fd-util.h"
  28 #include "fileio.h"
  29 #include "log.h"
  30 #include "mkdir.h"
  31 #include "path-util.h"
  32 #include "process-util.h"
  33 #include "string-util.h"
  34 #include "terminal-util.h"
  35 #include "unit-name.h"
  36 #include "util.h"
  37 #include "virt.h"
  38
  39 static const char *arg_dest = "/tmp";
  40
  41 static int add_symlink(const char *fservice, const char *tservice) {
  42         char *from, *to;
  43         int r;
  44
  45         assert(fservice);
  46         assert(tservice);
  47
  48         from = strjoina(SYSTEM_DATA_UNIT_PATH "/", fservice);
  49         to = strjoina(arg_dest, "/getty.target.wants/", tservice);
  50
  51         mkdir_parents_label(to, 0755);
  52
  53         r = symlink(from, to);
  54         if (r < 0) {
  55                 /* In case console=hvc0 is passed this will very likely result in EEXIST */
  56                 if (errno == EEXIST)
  57                         return 0;
  58
  59                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
  60         }
  61
  62         return 0;
  63 }
  64
  65 static int add_serial_getty(const char *tty) {
  66         _cleanup_free_ char *n = NULL;
  67         int r;
  68
  69         assert(tty);
  70
  71         log_debug("Automatically adding serial getty for /dev/%s.", tty);
  72
  73         r = unit_name_from_path_instance("serial-getty", tty, ".service", &n);
  74         if (r < 0)
  75                 return log_error_errno(r, "Failed to generate service name: %m");
  76
  77         return add_symlink("serial-getty@.service", n);
  78 }
  79
  80 static int add_container_getty(const char *tty) {
  81         _cleanup_free_ char *n = NULL;
  82         int r;
  83
  84         assert(tty);
  85
  86         log_debug("Automatically adding container getty for /dev/pts/%s.", tty);
  87
  88         r = unit_name_from_path_instance("container-getty", tty, ".service", &n);
  89         if (r < 0)
  90                 return log_error_errno(r, "Failed to generate service name: %m");
  91
  92         return add_symlink("container-getty@.service", n);
  93 }
  94
  95 static int verify_tty(const char *name) {
  96         _cleanup_close_ int fd = -1;
  97         const char *p;
  98
  99         /* Some TTYs are weird and have been enumerated but don't work
 100          * when you try to use them, such as classic ttyS0 and
 101          * friends. Let's check that and open the device and run
 102          * isatty() on it. */
 103
 104         p = strjoina("/dev/", name);
 105
 106         /* O_NONBLOCK is essential here, to make sure we don't wait
 107          * for DCD */
 108         fd = open(p, O_RDWR|O_NONBLOCK|O_NOCTTY|O_CLOEXEC|O_NOFOLLOW);
 109         if (fd < 0)
 110                 return -errno;
 111
 112         errno = 0;
 113         if (isatty(fd) <= 0)
 114                 return errno > 0 ? -errno : -EIO;
 115
 116         return 0;
 117 }
 118
 119 int main(int argc, char *argv[]) {
 120
 121         static const char virtualization_consoles[] =
 122                 "hvc0\0"
 123                 "xvc0\0"
 124                 "hvsi0\0"
 125                 "sclp_line0\0"
 126                 "ttysclp0\0"
 127                 "3270!tty1\0";
 128
 129         _cleanup_free_ char *active = NULL;
 130         const char *j;
 131         int r;
 132
 133         if (argc > 1 && argc != 4) {
 134                 log_error("This program takes three or no arguments.");
 135                 return EXIT_FAILURE;
 136         }
 137
 138         if (argc > 1)
 139                 arg_dest = argv[1];
 140
 141         log_set_target(LOG_TARGET_SAFE);
 142         log_parse_environment();
 143         log_open();
 144
 145         umask(0022);
 146
 147         if (detect_container() > 0) {
 148                 _cleanup_free_ char *container_ttys = NULL;
 149
 150                 log_debug("Automatically adding console shell.");
 151
 152                 if (add_symlink("console-getty.service", "console-getty.service") < 0)
 153                         return EXIT_FAILURE;
 154
 155                 /* When $container_ttys is set for PID 1, spawn
 156                  * gettys on all ptys named therein. Note that despite
 157                  * the variable name we only support ptys here. */
 158
 159                 r = getenv_for_pid(1, "container_ttys", &container_ttys);
 160                 if (r > 0) {
 161                         const char *word, *state;
 162                         size_t l;
 163
 164                         FOREACH_WORD(word, l, container_ttys, state) {
 165                                 const char *t;
 166                                 char tty[l + 1];
 167
 168                                 memcpy(tty, word, l);
 169                                 tty[l] = 0;
 170
 171                                 /* First strip off /dev/ if it is specified */
 172                                 t = path_startswith(tty, "/dev/");
 173                                 if (!t)
 174                                         t = tty;
 175
 176                                 /* Then, make sure it's actually a pty */
 177                                 t = path_startswith(t, "pts/");
 178                                 if (!t)
 179                                         continue;
 180
 181                                 if (add_container_getty(t) < 0)
 182                                         return EXIT_FAILURE;
 183                         }
 184                 }
 185
 186                 /* Don't add any further magic if we are in a container */
 187                 return EXIT_SUCCESS;
 188         }
 189
 190         if (read_one_line_file("/sys/class/tty/console/active", &active) >= 0) {
 191                 const char *word, *state;
 192                 size_t l;
 193
 194                 /* Automatically add in a serial getty on all active
 195                  * kernel consoles */
 196                 FOREACH_WORD(word, l, active, state) {
 197                         _cleanup_free_ char *tty = NULL;
 198
 199                         tty = strndup(word, l);
 200                         if (!tty) {
 201                                 log_oom();
 202                                 return EXIT_FAILURE;
 203                         }
 204
 205                         /* We assume that gettys on virtual terminals are
 206                          * started via manual configuration and do this magic
 207                          * only for non-VC terminals. */
 208
 209                         if (isempty(tty) || tty_is_vc(tty))
 210                                 continue;
 211
 212                         if (verify_tty(tty) < 0)
 213                                 continue;
 214
 215                         if (add_serial_getty(tty) < 0)
 216                                 return EXIT_FAILURE;
 217                 }
 218         }
 219
 220         /* Automatically add in a serial getty on the first
 221          * virtualizer console */
 222         NULSTR_FOREACH(j, virtualization_consoles) {
 223                 char *p;
 224
 225                 p = strjoina("/sys/class/tty/", j);
 226                 if (access(p, F_OK) < 0)
 227                         continue;
 228
 229                 if (add_serial_getty(j) < 0)
 230                         return EXIT_FAILURE;
 231         }
 232
 233         return EXIT_SUCCESS;
 234 }