os-posix.c

   1 /*
   2  * os-posix.c
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  * Copyright (c) 2010 Red Hat, Inc.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #include "qemu/osdep.h"
  27 #include <sys/wait.h>
  28 #include <pwd.h>
  29 #include <grp.h>
  30 #include <libgen.h>
  31
  32 /* Needed early for CONFIG_BSD etc. */
  33 #include "net/slirp.h"
  34 #include "qemu/qemu-options.h"
  35 #include "qemu/error-report.h"
  36 #include "qemu/log.h"
  37 #include "sysemu/runstate.h"
  38 #include "qemu/cutils.h"
  39 #include "qemu/config-file.h"
  40 #include "qemu/option.h"
  41
  42 #ifdef CONFIG_LINUX
  43 #include <sys/prctl.h>
  44 #include "qemu/async-teardown.h"
  45 #endif
  46
  47 /*
  48  * Must set all three of these at once.
  49  * Legal combinations are              unset   by name   by uid
  50  */
  51 static struct passwd *user_pwd;    /*   NULL   non-NULL   NULL   */
  52 static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
  53 static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */
  54
  55 static const char *chroot_dir;
  56 static int daemonize;
  57 static int daemon_pipe;
  58
  59 void os_setup_early_signal_handling(void)
  60 {
  61     struct sigaction act;
  62     sigfillset(&act.sa_mask);
  63     act.sa_flags = 0;
  64     act.sa_handler = SIG_IGN;
  65     sigaction(SIGPIPE, &act, NULL);
  66 }
  67
  68 static void termsig_handler(int signal, siginfo_t *info, void *c)
  69 {
  70     qemu_system_killed(info->si_signo, info->si_pid);
  71 }
  72
  73 void os_setup_signal_handling(void)
  74 {
  75     struct sigaction act;
  76
  77     memset(&act, 0, sizeof(act));
  78     act.sa_sigaction = termsig_handler;
  79     act.sa_flags = SA_SIGINFO;
  80     sigaction(SIGINT,  &act, NULL);
  81     sigaction(SIGHUP,  &act, NULL);
  82     sigaction(SIGTERM, &act, NULL);
  83 }
  84
  85 void os_set_proc_name(const char *s)
  86 {
  87 #if defined(PR_SET_NAME)
  88     char name[16];
  89     if (!s)
  90         return;
  91     pstrcpy(name, sizeof(name), s);
  92     /* Could rewrite argv[0] too, but that's a bit more complicated.
  93        This simple way is enough for `top'. */
  94     if (prctl(PR_SET_NAME, name)) {
  95         error_report("unable to change process name: %s", strerror(errno));
  96         exit(1);
  97     }
  98 #else
  99     error_report("Change of process name not supported by your OS");
 100     exit(1);
 101 #endif
 102 }
 103
 104
 105 static bool os_parse_runas_uid_gid(const char *optarg)
 106 {
 107     unsigned long lv;
 108     const char *ep;
 109     uid_t got_uid;
 110     gid_t got_gid;
 111     int rc;
 112
 113     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 114     got_uid = lv; /* overflow here is ID in C99 */
 115     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 116         return false;
 117     }
 118
 119     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 120     got_gid = lv; /* overflow here is ID in C99 */
 121     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 122         return false;
 123     }
 124
 125     user_pwd = NULL;
 126     user_uid = got_uid;
 127     user_gid = got_gid;
 128     return true;
 129 }
 130
 131 /*
 132  * Parse OS specific command line options.
 133  * return 0 if option handled, -1 otherwise
 134  */
 135 int os_parse_cmd_args(int index, const char *optarg)
 136 {
 137     switch (index) {
 138     case QEMU_OPTION_runas:
 139         user_pwd = getpwnam(optarg);
 140         if (user_pwd) {
 141             user_uid = -1;
 142             user_gid = -1;
 143         } else if (!os_parse_runas_uid_gid(optarg)) {
 144             error_report("User \"%s\" doesn't exist"
 145                          " (and is not <uid>:<gid>)",
 146                          optarg);
 147             exit(1);
 148         }
 149         break;
 150     case QEMU_OPTION_chroot:
 151         chroot_dir = optarg;
 152         break;
 153     case QEMU_OPTION_daemonize:
 154         daemonize = 1;
 155         break;
 156 #if defined(CONFIG_LINUX)
 157     /* deprecated */
 158     case QEMU_OPTION_asyncteardown:
 159         init_async_teardown();
 160         break;
 161     case QEMU_OPTION_run_with: {
 162         QemuOpts *opts = qemu_opts_parse_noisily(qemu_find_opts("run-with"),
 163                                                  optarg, false);
 164         if (!opts) {
 165             exit(1);
 166         }
 167         if (qemu_opt_get_bool(opts, "async-teardown", false)) {
 168             init_async_teardown();
 169         }
 170         break;
 171     }
 172 #endif
 173     default:
 174         return -1;
 175     }
 176
 177     return 0;
 178 }
 179
 180 static void change_process_uid(void)
 181 {
 182     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 183     assert((user_uid == (uid_t)-1) ==
 184            (user_gid == (gid_t)-1));
 185
 186     if (user_pwd || user_uid != (uid_t)-1) {
 187         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 188         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 189         if (setgid(intended_gid) < 0) {
 190             error_report("Failed to setgid(%d)", intended_gid);
 191             exit(1);
 192         }
 193         if (user_pwd) {
 194             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 195                 error_report("Failed to initgroups(\"%s\", %d)",
 196                         user_pwd->pw_name, user_pwd->pw_gid);
 197                 exit(1);
 198             }
 199         } else {
 200             if (setgroups(1, &user_gid) < 0) {
 201                 error_report("Failed to setgroups(1, [%d])",
 202                         user_gid);
 203                 exit(1);
 204             }
 205         }
 206         if (setuid(intended_uid) < 0) {
 207             error_report("Failed to setuid(%d)", intended_uid);
 208             exit(1);
 209         }
 210         if (setuid(0) != -1) {
 211             error_report("Dropping privileges failed");
 212             exit(1);
 213         }
 214     }
 215 }
 216
 217 static void change_root(void)
 218 {
 219     if (chroot_dir) {
 220         if (chroot(chroot_dir) < 0) {
 221             error_report("chroot failed");
 222             exit(1);
 223         }
 224         if (chdir("/")) {
 225             error_report("not able to chdir to /: %s", strerror(errno));
 226             exit(1);
 227         }
 228     }
 229
 230 }
 231
 232 void os_daemonize(void)
 233 {
 234     if (daemonize) {
 235         pid_t pid;
 236         int fds[2];
 237
 238         if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
 239             exit(1);
 240         }
 241
 242         pid = fork();
 243         if (pid > 0) {
 244             uint8_t status;
 245             ssize_t len;
 246
 247             close(fds[1]);
 248
 249             do {
 250                 len = read(fds[0], &status, 1);
 251             } while (len < 0 && errno == EINTR);
 252
 253             /* only exit successfully if our child actually wrote
 254              * a one-byte zero to our pipe, upon successful init */
 255             exit(len == 1 && status == 0 ? 0 : 1);
 256
 257         } else if (pid < 0) {
 258             exit(1);
 259         }
 260
 261         close(fds[0]);
 262         daemon_pipe = fds[1];
 263
 264         setsid();
 265
 266         pid = fork();
 267         if (pid > 0) {
 268             exit(0);
 269         } else if (pid < 0) {
 270             exit(1);
 271         }
 272         umask(027);
 273
 274         signal(SIGTSTP, SIG_IGN);
 275         signal(SIGTTOU, SIG_IGN);
 276         signal(SIGTTIN, SIG_IGN);
 277     }
 278 }
 279
 280 void os_setup_post(void)
 281 {
 282     int fd = 0;
 283
 284     if (daemonize) {
 285         if (chdir("/")) {
 286             error_report("not able to chdir to /: %s", strerror(errno));
 287             exit(1);
 288         }
 289         fd = RETRY_ON_EINTR(qemu_open_old("/dev/null", O_RDWR));
 290         if (fd == -1) {
 291             exit(1);
 292         }
 293     }
 294
 295     change_root();
 296     change_process_uid();
 297
 298     if (daemonize) {
 299         uint8_t status = 0;
 300         ssize_t len;
 301
 302         dup2(fd, 0);
 303         dup2(fd, 1);
 304         /* In case -D is given do not redirect stderr to /dev/null */
 305         if (!qemu_log_enabled()) {
 306             dup2(fd, 2);
 307         }
 308
 309         close(fd);
 310
 311         do {
 312             len = write(daemon_pipe, &status, 1);
 313         } while (len < 0 && errno == EINTR);
 314         if (len != 1) {
 315             exit(1);
 316         }
 317     }
 318 }
 319
 320 void os_set_line_buffering(void)
 321 {
 322     setvbuf(stdout, NULL, _IOLBF, 0);
 323 }
 324
 325 bool is_daemonized(void)
 326 {
 327     return daemonize;
 328 }
 329
 330 int os_set_daemonize(bool d)
 331 {
 332     daemonize = d;
 333     return 0;
 334 }
 335
 336 int os_mlock(void)
 337 {
 338 #ifdef HAVE_MLOCKALL
 339     int ret = 0;
 340
 341     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 342     if (ret < 0) {
 343         error_report("mlockall: %s", strerror(errno));
 344     }
 345
 346     return ret;
 347 #else
 348     return -ENOSYS;
 349 #endif
 350 }