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 #include "qemu-common.h"
  33 /* Needed early for CONFIG_BSD etc. */
  34 #include "net/slirp.h"
  35 #include "qemu-options.h"
  36 #include "qemu/error-report.h"
  37 #include "qemu/log.h"
  38 #include "sysemu/runstate.h"
  39 #include "qemu/cutils.h"
  40
  41 #ifdef CONFIG_LINUX
  42 #include <sys/prctl.h>
  43 #endif
  44
  45 /*
  46  * Must set all three of these at once.
  47  * Legal combinations are              unset   by name   by uid
  48  */
  49 static struct passwd *user_pwd;    /*   NULL   non-NULL   NULL   */
  50 static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
  51 static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */
  52
  53 static const char *chroot_dir;
  54 static int daemonize;
  55 static int daemon_pipe;
  56
  57 void os_setup_early_signal_handling(void)
  58 {
  59     struct sigaction act;
  60     sigfillset(&act.sa_mask);
  61     act.sa_flags = 0;
  62     act.sa_handler = SIG_IGN;
  63     sigaction(SIGPIPE, &act, NULL);
  64 }
  65
  66 static void termsig_handler(int signal, siginfo_t *info, void *c)
  67 {
  68     qemu_system_killed(info->si_signo, info->si_pid);
  69 }
  70
  71 void os_setup_signal_handling(void)
  72 {
  73     struct sigaction act;
  74
  75     memset(&act, 0, sizeof(act));
  76     act.sa_sigaction = termsig_handler;
  77     act.sa_flags = SA_SIGINFO;
  78     sigaction(SIGINT,  &act, NULL);
  79     sigaction(SIGHUP,  &act, NULL);
  80     sigaction(SIGTERM, &act, NULL);
  81 }
  82
  83 /*
  84  * Find a likely location for support files using the location of the binary.
  85  * When running from the build tree this will be "$bindir/pc-bios".
  86  * Otherwise, this is CONFIG_QEMU_DATADIR.
  87  *
  88  * The caller must use g_free() to free the returned data when it is
  89  * no longer required.
  90  */
  91 char *os_find_datadir(void)
  92 {
  93     g_autofree char *dir = NULL;
  94
  95     dir = g_build_filename(qemu_get_exec_dir(), "pc-bios", NULL);
  96     if (g_file_test(dir, G_FILE_TEST_IS_DIR)) {
  97         return g_steal_pointer(&dir);
  98     }
  99
 100     return g_strdup(CONFIG_QEMU_DATADIR);
 101 }
 102
 103 void os_set_proc_name(const char *s)
 104 {
 105 #if defined(PR_SET_NAME)
 106     char name[16];
 107     if (!s)
 108         return;
 109     pstrcpy(name, sizeof(name), s);
 110     /* Could rewrite argv[0] too, but that's a bit more complicated.
 111        This simple way is enough for `top'. */
 112     if (prctl(PR_SET_NAME, name)) {
 113         error_report("unable to change process name: %s", strerror(errno));
 114         exit(1);
 115     }
 116 #else
 117     error_report("Change of process name not supported by your OS");
 118     exit(1);
 119 #endif
 120 }
 121
 122
 123 static bool os_parse_runas_uid_gid(const char *optarg)
 124 {
 125     unsigned long lv;
 126     const char *ep;
 127     uid_t got_uid;
 128     gid_t got_gid;
 129     int rc;
 130
 131     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 132     got_uid = lv; /* overflow here is ID in C99 */
 133     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 134         return false;
 135     }
 136
 137     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 138     got_gid = lv; /* overflow here is ID in C99 */
 139     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 140         return false;
 141     }
 142
 143     user_pwd = NULL;
 144     user_uid = got_uid;
 145     user_gid = got_gid;
 146     return true;
 147 }
 148
 149 /*
 150  * Parse OS specific command line options.
 151  * return 0 if option handled, -1 otherwise
 152  */
 153 int os_parse_cmd_args(int index, const char *optarg)
 154 {
 155     switch (index) {
 156     case QEMU_OPTION_runas:
 157         user_pwd = getpwnam(optarg);
 158         if (user_pwd) {
 159             user_uid = -1;
 160             user_gid = -1;
 161         } else if (!os_parse_runas_uid_gid(optarg)) {
 162             error_report("User \"%s\" doesn't exist"
 163                          " (and is not <uid>:<gid>)",
 164                          optarg);
 165             exit(1);
 166         }
 167         break;
 168     case QEMU_OPTION_chroot:
 169         chroot_dir = optarg;
 170         break;
 171     case QEMU_OPTION_daemonize:
 172         daemonize = 1;
 173         break;
 174 #if defined(CONFIG_LINUX)
 175     case QEMU_OPTION_enablefips:
 176         fips_set_state(true);
 177         break;
 178 #endif
 179     default:
 180         return -1;
 181     }
 182
 183     return 0;
 184 }
 185
 186 static void change_process_uid(void)
 187 {
 188     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 189     assert((user_uid == (uid_t)-1) ==
 190            (user_gid == (gid_t)-1));
 191
 192     if (user_pwd || user_uid != (uid_t)-1) {
 193         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 194         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 195         if (setgid(intended_gid) < 0) {
 196             error_report("Failed to setgid(%d)", intended_gid);
 197             exit(1);
 198         }
 199         if (user_pwd) {
 200             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 201                 error_report("Failed to initgroups(\"%s\", %d)",
 202                         user_pwd->pw_name, user_pwd->pw_gid);
 203                 exit(1);
 204             }
 205         } else {
 206             if (setgroups(1, &user_gid) < 0) {
 207                 error_report("Failed to setgroups(1, [%d])",
 208                         user_gid);
 209                 exit(1);
 210             }
 211         }
 212         if (setuid(intended_uid) < 0) {
 213             error_report("Failed to setuid(%d)", intended_uid);
 214             exit(1);
 215         }
 216         if (setuid(0) != -1) {
 217             error_report("Dropping privileges failed");
 218             exit(1);
 219         }
 220     }
 221 }
 222
 223 static void change_root(void)
 224 {
 225     if (chroot_dir) {
 226         if (chroot(chroot_dir) < 0) {
 227             error_report("chroot failed");
 228             exit(1);
 229         }
 230         if (chdir("/")) {
 231             error_report("not able to chdir to /: %s", strerror(errno));
 232             exit(1);
 233         }
 234     }
 235
 236 }
 237
 238 void os_daemonize(void)
 239 {
 240     if (daemonize) {
 241         pid_t pid;
 242         int fds[2];
 243
 244         if (pipe(fds) == -1) {
 245             exit(1);
 246         }
 247
 248         pid = fork();
 249         if (pid > 0) {
 250             uint8_t status;
 251             ssize_t len;
 252
 253             close(fds[1]);
 254
 255             do {
 256                 len = read(fds[0], &status, 1);
 257             } while (len < 0 && errno == EINTR);
 258
 259             /* only exit successfully if our child actually wrote
 260              * a one-byte zero to our pipe, upon successful init */
 261             exit(len == 1 && status == 0 ? 0 : 1);
 262
 263         } else if (pid < 0) {
 264             exit(1);
 265         }
 266
 267         close(fds[0]);
 268         daemon_pipe = fds[1];
 269         qemu_set_cloexec(daemon_pipe);
 270
 271         setsid();
 272
 273         pid = fork();
 274         if (pid > 0) {
 275             exit(0);
 276         } else if (pid < 0) {
 277             exit(1);
 278         }
 279         umask(027);
 280
 281         signal(SIGTSTP, SIG_IGN);
 282         signal(SIGTTOU, SIG_IGN);
 283         signal(SIGTTIN, SIG_IGN);
 284     }
 285 }
 286
 287 void os_setup_post(void)
 288 {
 289     int fd = 0;
 290
 291     if (daemonize) {
 292         if (chdir("/")) {
 293             error_report("not able to chdir to /: %s", strerror(errno));
 294             exit(1);
 295         }
 296         TFR(fd = qemu_open_old("/dev/null", O_RDWR));
 297         if (fd == -1) {
 298             exit(1);
 299         }
 300     }
 301
 302     change_root();
 303     change_process_uid();
 304
 305     if (daemonize) {
 306         uint8_t status = 0;
 307         ssize_t len;
 308
 309         dup2(fd, 0);
 310         dup2(fd, 1);
 311         /* In case -D is given do not redirect stderr to /dev/null */
 312         if (!qemu_logfile) {
 313             dup2(fd, 2);
 314         }
 315
 316         close(fd);
 317
 318         do {
 319             len = write(daemon_pipe, &status, 1);
 320         } while (len < 0 && errno == EINTR);
 321         if (len != 1) {
 322             exit(1);
 323         }
 324     }
 325 }
 326
 327 void os_set_line_buffering(void)
 328 {
 329     setvbuf(stdout, NULL, _IOLBF, 0);
 330 }
 331
 332 bool is_daemonized(void)
 333 {
 334     return daemonize;
 335 }
 336
 337 int os_mlock(void)
 338 {
 339 #ifdef HAVE_MLOCKALL
 340     int ret = 0;
 341
 342     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 343     if (ret < 0) {
 344         error_report("mlockall: %s", strerror(errno));
 345     }
 346
 347     return ret;
 348 #else
 349     return -ENOSYS;
 350 #endif
 351 }