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
  40 #ifdef CONFIG_LINUX
  41 #include <sys/prctl.h>
  42 #include "qemu/async-teardown.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 void os_set_proc_name(const char *s)
  84 {
  85 #if defined(PR_SET_NAME)
  86     char name[16];
  87     if (!s)
  88         return;
  89     pstrcpy(name, sizeof(name), s);
  90     /* Could rewrite argv[0] too, but that's a bit more complicated.
  91        This simple way is enough for `top'. */
  92     if (prctl(PR_SET_NAME, name)) {
  93         error_report("unable to change process name: %s", strerror(errno));
  94         exit(1);
  95     }
  96 #else
  97     error_report("Change of process name not supported by your OS");
  98     exit(1);
  99 #endif
 100 }
 101
 102
 103 static bool os_parse_runas_uid_gid(const char *optarg)
 104 {
 105     unsigned long lv;
 106     const char *ep;
 107     uid_t got_uid;
 108     gid_t got_gid;
 109     int rc;
 110
 111     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 112     got_uid = lv; /* overflow here is ID in C99 */
 113     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 114         return false;
 115     }
 116
 117     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 118     got_gid = lv; /* overflow here is ID in C99 */
 119     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 120         return false;
 121     }
 122
 123     user_pwd = NULL;
 124     user_uid = got_uid;
 125     user_gid = got_gid;
 126     return true;
 127 }
 128
 129 /*
 130  * Parse OS specific command line options.
 131  * return 0 if option handled, -1 otherwise
 132  */
 133 int os_parse_cmd_args(int index, const char *optarg)
 134 {
 135     switch (index) {
 136     case QEMU_OPTION_runas:
 137         user_pwd = getpwnam(optarg);
 138         if (user_pwd) {
 139             user_uid = -1;
 140             user_gid = -1;
 141         } else if (!os_parse_runas_uid_gid(optarg)) {
 142             error_report("User \"%s\" doesn't exist"
 143                          " (and is not <uid>:<gid>)",
 144                          optarg);
 145             exit(1);
 146         }
 147         break;
 148     case QEMU_OPTION_chroot:
 149         chroot_dir = optarg;
 150         break;
 151     case QEMU_OPTION_daemonize:
 152         daemonize = 1;
 153         break;
 154 #if defined(CONFIG_LINUX)
 155     case QEMU_OPTION_asyncteardown:
 156         init_async_teardown();
 157         break;
 158 #endif
 159     default:
 160         return -1;
 161     }
 162
 163     return 0;
 164 }
 165
 166 static void change_process_uid(void)
 167 {
 168     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 169     assert((user_uid == (uid_t)-1) ==
 170            (user_gid == (gid_t)-1));
 171
 172     if (user_pwd || user_uid != (uid_t)-1) {
 173         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 174         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 175         if (setgid(intended_gid) < 0) {
 176             error_report("Failed to setgid(%d)", intended_gid);
 177             exit(1);
 178         }
 179         if (user_pwd) {
 180             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 181                 error_report("Failed to initgroups(\"%s\", %d)",
 182                         user_pwd->pw_name, user_pwd->pw_gid);
 183                 exit(1);
 184             }
 185         } else {
 186             if (setgroups(1, &user_gid) < 0) {
 187                 error_report("Failed to setgroups(1, [%d])",
 188                         user_gid);
 189                 exit(1);
 190             }
 191         }
 192         if (setuid(intended_uid) < 0) {
 193             error_report("Failed to setuid(%d)", intended_uid);
 194             exit(1);
 195         }
 196         if (setuid(0) != -1) {
 197             error_report("Dropping privileges failed");
 198             exit(1);
 199         }
 200     }
 201 }
 202
 203 static void change_root(void)
 204 {
 205     if (chroot_dir) {
 206         if (chroot(chroot_dir) < 0) {
 207             error_report("chroot failed");
 208             exit(1);
 209         }
 210         if (chdir("/")) {
 211             error_report("not able to chdir to /: %s", strerror(errno));
 212             exit(1);
 213         }
 214     }
 215
 216 }
 217
 218 void os_daemonize(void)
 219 {
 220     if (daemonize) {
 221         pid_t pid;
 222         int fds[2];
 223
 224         if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
 225             exit(1);
 226         }
 227
 228         pid = fork();
 229         if (pid > 0) {
 230             uint8_t status;
 231             ssize_t len;
 232
 233             close(fds[1]);
 234
 235             do {
 236                 len = read(fds[0], &status, 1);
 237             } while (len < 0 && errno == EINTR);
 238
 239             /* only exit successfully if our child actually wrote
 240              * a one-byte zero to our pipe, upon successful init */
 241             exit(len == 1 && status == 0 ? 0 : 1);
 242
 243         } else if (pid < 0) {
 244             exit(1);
 245         }
 246
 247         close(fds[0]);
 248         daemon_pipe = fds[1];
 249
 250         setsid();
 251
 252         pid = fork();
 253         if (pid > 0) {
 254             exit(0);
 255         } else if (pid < 0) {
 256             exit(1);
 257         }
 258         umask(027);
 259
 260         signal(SIGTSTP, SIG_IGN);
 261         signal(SIGTTOU, SIG_IGN);
 262         signal(SIGTTIN, SIG_IGN);
 263     }
 264 }
 265
 266 void os_setup_post(void)
 267 {
 268     int fd = 0;
 269
 270     if (daemonize) {
 271         if (chdir("/")) {
 272             error_report("not able to chdir to /: %s", strerror(errno));
 273             exit(1);
 274         }
 275         TFR(fd = qemu_open_old("/dev/null", O_RDWR));
 276         if (fd == -1) {
 277             exit(1);
 278         }
 279     }
 280
 281     change_root();
 282     change_process_uid();
 283
 284     if (daemonize) {
 285         uint8_t status = 0;
 286         ssize_t len;
 287
 288         dup2(fd, 0);
 289         dup2(fd, 1);
 290         /* In case -D is given do not redirect stderr to /dev/null */
 291         if (!qemu_log_enabled()) {
 292             dup2(fd, 2);
 293         }
 294
 295         close(fd);
 296
 297         do {
 298             len = write(daemon_pipe, &status, 1);
 299         } while (len < 0 && errno == EINTR);
 300         if (len != 1) {
 301             exit(1);
 302         }
 303     }
 304 }
 305
 306 void os_set_line_buffering(void)
 307 {
 308     setvbuf(stdout, NULL, _IOLBF, 0);
 309 }
 310
 311 bool is_daemonized(void)
 312 {
 313     return daemonize;
 314 }
 315
 316 int os_set_daemonize(bool d)
 317 {
 318     daemonize = d;
 319     return 0;
 320 }
 321
 322 int os_mlock(void)
 323 {
 324 #ifdef HAVE_MLOCKALL
 325     int ret = 0;
 326
 327     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 328     if (ret < 0) {
 329         error_report("mlockall: %s", strerror(errno));
 330     }
 331
 332     return ret;
 333 #else
 334     return -ENOSYS;
 335 #endif
 336 }