src/getty-generator/getty-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7
   8 #include "alloc-util.h"
   9 #include "fd-util.h"
  10 #include "fileio.h"
  11 #include "log.h"
  12 #include "mkdir.h"
  13 #include "path-util.h"
  14 #include "process-util.h"
  15 #include "string-util.h"
  16 #include "terminal-util.h"
  17 #include "unit-name.h"
  18 #include "util.h"
  19 #include "virt.h"
  20
  21 static const char *arg_dest = "/tmp";
  22
  23 static int add_symlink(const char *fservice, const char *tservice) {
  24         char *from, *to;
  25         int r;
  26
  27         assert(fservice);
  28         assert(tservice);
  29
  30         from = strjoina(SYSTEM_DATA_UNIT_PATH "/", fservice);
  31         to = strjoina(arg_dest, "/getty.target.wants/", tservice);
  32
  33         mkdir_parents_label(to, 0755);
  34
  35         r = symlink(from, to);
  36         if (r < 0) {
  37                 /* In case console=hvc0 is passed this will very likely result in EEXIST */
  38                 if (errno == EEXIST)
  39                         return 0;
  40
  41                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
  42         }
  43
  44         return 0;
  45 }
  46
  47 static int add_serial_getty(const char *tty) {
  48         _cleanup_free_ char *n = NULL;
  49         int r;
  50
  51         assert(tty);
  52
  53         log_debug("Automatically adding serial getty for /dev/%s.", tty);
  54
  55         r = unit_name_from_path_instance("serial-getty", tty, ".service", &n);
  56         if (r < 0)
  57                 return log_error_errno(r, "Failed to generate service name: %m");
  58
  59         return add_symlink("serial-getty@.service", n);
  60 }
  61
  62 static int add_container_getty(const char *tty) {
  63         _cleanup_free_ char *n = NULL;
  64         int r;
  65
  66         assert(tty);
  67
  68         log_debug("Automatically adding container getty for /dev/pts/%s.", tty);
  69
  70         r = unit_name_from_path_instance("container-getty", tty, ".service", &n);
  71         if (r < 0)
  72                 return log_error_errno(r, "Failed to generate service name: %m");
  73
  74         return add_symlink("container-getty@.service", n);
  75 }
  76
  77 static int verify_tty(const char *name) {
  78         _cleanup_close_ int fd = -1;
  79         const char *p;
  80
  81         /* Some TTYs are weird and have been enumerated but don't work
  82          * when you try to use them, such as classic ttyS0 and
  83          * friends. Let's check that and open the device and run
  84          * isatty() on it. */
  85
  86         p = strjoina("/dev/", name);
  87
  88         /* O_NONBLOCK is essential here, to make sure we don't wait
  89          * for DCD */
  90         fd = open(p, O_RDWR|O_NONBLOCK|O_NOCTTY|O_CLOEXEC|O_NOFOLLOW);
  91         if (fd < 0)
  92                 return -errno;
  93
  94         errno = 0;
  95         if (isatty(fd) <= 0)
  96                 return errno > 0 ? -errno : -EIO;
  97
  98         return 0;
  99 }
 100
 101 int main(int argc, char *argv[]) {
 102
 103         static const char virtualization_consoles[] =
 104                 "hvc0\0"
 105                 "xvc0\0"
 106                 "hvsi0\0"
 107                 "sclp_line0\0"
 108                 "ttysclp0\0"
 109                 "3270!tty1\0";
 110
 111         _cleanup_free_ char *active = NULL;
 112         const char *j;
 113         int r;
 114
 115         if (argc > 1 && argc != 4) {
 116                 log_error("This program takes three or no arguments.");
 117                 return EXIT_FAILURE;
 118         }
 119
 120         if (argc > 1)
 121                 arg_dest = argv[1];
 122
 123         log_set_prohibit_ipc(true);
 124         log_set_target(LOG_TARGET_AUTO);
 125         log_parse_environment();
 126         log_open();
 127
 128         umask(0022);
 129
 130         if (detect_container() > 0) {
 131                 _cleanup_free_ char *container_ttys = NULL;
 132
 133                 log_debug("Automatically adding console shell.");
 134
 135                 if (add_symlink("console-getty.service", "console-getty.service") < 0)
 136                         return EXIT_FAILURE;
 137
 138                 /* When $container_ttys is set for PID 1, spawn
 139                  * gettys on all ptys named therein. Note that despite
 140                  * the variable name we only support ptys here. */
 141
 142                 r = getenv_for_pid(1, "container_ttys", &container_ttys);
 143                 if (r > 0) {
 144                         const char *word, *state;
 145                         size_t l;
 146
 147                         FOREACH_WORD(word, l, container_ttys, state) {
 148                                 const char *t;
 149                                 char tty[l + 1];
 150
 151                                 memcpy(tty, word, l);
 152                                 tty[l] = 0;
 153
 154                                 /* First strip off /dev/ if it is specified */
 155                                 t = path_startswith(tty, "/dev/");
 156                                 if (!t)
 157                                         t = tty;
 158
 159                                 /* Then, make sure it's actually a pty */
 160                                 t = path_startswith(t, "pts/");
 161                                 if (!t)
 162                                         continue;
 163
 164                                 if (add_container_getty(t) < 0)
 165                                         return EXIT_FAILURE;
 166                         }
 167                 }
 168
 169                 /* Don't add any further magic if we are in a container */
 170                 return EXIT_SUCCESS;
 171         }
 172
 173         if (read_one_line_file("/sys/class/tty/console/active", &active) >= 0) {
 174                 const char *word, *state;
 175                 size_t l;
 176
 177                 /* Automatically add in a serial getty on all active
 178                  * kernel consoles */
 179                 FOREACH_WORD(word, l, active, state) {
 180                         _cleanup_free_ char *tty = NULL;
 181
 182                         tty = strndup(word, l);
 183                         if (!tty) {
 184                                 log_oom();
 185                                 return EXIT_FAILURE;
 186                         }
 187
 188                         /* We assume that gettys on virtual terminals are
 189                          * started via manual configuration and do this magic
 190                          * only for non-VC terminals. */
 191
 192                         if (isempty(tty) || tty_is_vc(tty))
 193                                 continue;
 194
 195                         if (verify_tty(tty) < 0)
 196                                 continue;
 197
 198                         if (add_serial_getty(tty) < 0)
 199                                 return EXIT_FAILURE;
 200                 }
 201         }
 202
 203         /* Automatically add in a serial getty on the first
 204          * virtualizer console */
 205         NULSTR_FOREACH(j, virtualization_consoles) {
 206                 char *p;
 207
 208                 p = strjoina("/sys/class/tty/", j);
 209                 if (access(p, F_OK) < 0)
 210                         continue;
 211
 212                 if (add_serial_getty(j) < 0)
 213                         return EXIT_FAILURE;
 214         }
 215
 216         return EXIT_SUCCESS;
 217 }