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 *exec_dir = NULL;
  94     g_autofree char *dir = NULL;
  95
  96     exec_dir = qemu_get_exec_dir();
  97     g_return_val_if_fail(exec_dir != NULL, NULL);
  98
  99     dir = g_build_filename(exec_dir, "..", "pc-bios", NULL);
 100     if (g_file_test(dir, G_FILE_TEST_IS_DIR)) {
 101         return g_steal_pointer(&dir);
 102     }
 103
 104     return g_strdup(CONFIG_QEMU_DATADIR);
 105 }
 106
 107 void os_set_proc_name(const char *s)
 108 {
 109 #if defined(PR_SET_NAME)
 110     char name[16];
 111     if (!s)
 112         return;
 113     pstrcpy(name, sizeof(name), s);
 114     /* Could rewrite argv[0] too, but that's a bit more complicated.
 115        This simple way is enough for `top'. */
 116     if (prctl(PR_SET_NAME, name)) {
 117         error_report("unable to change process name: %s", strerror(errno));
 118         exit(1);
 119     }
 120 #else
 121     error_report("Change of process name not supported by your OS");
 122     exit(1);
 123 #endif
 124 }
 125
 126
 127 static bool os_parse_runas_uid_gid(const char *optarg)
 128 {
 129     unsigned long lv;
 130     const char *ep;
 131     uid_t got_uid;
 132     gid_t got_gid;
 133     int rc;
 134
 135     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 136     got_uid = lv; /* overflow here is ID in C99 */
 137     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 138         return false;
 139     }
 140
 141     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 142     got_gid = lv; /* overflow here is ID in C99 */
 143     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 144         return false;
 145     }
 146
 147     user_pwd = NULL;
 148     user_uid = got_uid;
 149     user_gid = got_gid;
 150     return true;
 151 }
 152
 153 /*
 154  * Parse OS specific command line options.
 155  * return 0 if option handled, -1 otherwise
 156  */
 157 int os_parse_cmd_args(int index, const char *optarg)
 158 {
 159     switch (index) {
 160     case QEMU_OPTION_runas:
 161         user_pwd = getpwnam(optarg);
 162         if (user_pwd) {
 163             user_uid = -1;
 164             user_gid = -1;
 165         } else if (!os_parse_runas_uid_gid(optarg)) {
 166             error_report("User \"%s\" doesn't exist"
 167                          " (and is not <uid>:<gid>)",
 168                          optarg);
 169             exit(1);
 170         }
 171         break;
 172     case QEMU_OPTION_chroot:
 173         chroot_dir = optarg;
 174         break;
 175     case QEMU_OPTION_daemonize:
 176         daemonize = 1;
 177         break;
 178 #if defined(CONFIG_LINUX)
 179     case QEMU_OPTION_enablefips:
 180         fips_set_state(true);
 181         break;
 182 #endif
 183     default:
 184         return -1;
 185     }
 186
 187     return 0;
 188 }
 189
 190 static void change_process_uid(void)
 191 {
 192     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 193     assert((user_uid == (uid_t)-1) ==
 194            (user_gid == (gid_t)-1));
 195
 196     if (user_pwd || user_uid != (uid_t)-1) {
 197         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 198         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 199         if (setgid(intended_gid) < 0) {
 200             error_report("Failed to setgid(%d)", intended_gid);
 201             exit(1);
 202         }
 203         if (user_pwd) {
 204             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 205                 error_report("Failed to initgroups(\"%s\", %d)",
 206                         user_pwd->pw_name, user_pwd->pw_gid);
 207                 exit(1);
 208             }
 209         } else {
 210             if (setgroups(1, &user_gid) < 0) {
 211                 error_report("Failed to setgroups(1, [%d])",
 212                         user_gid);
 213                 exit(1);
 214             }
 215         }
 216         if (setuid(intended_uid) < 0) {
 217             error_report("Failed to setuid(%d)", intended_uid);
 218             exit(1);
 219         }
 220         if (setuid(0) != -1) {
 221             error_report("Dropping privileges failed");
 222             exit(1);
 223         }
 224     }
 225 }
 226
 227 static void change_root(void)
 228 {
 229     if (chroot_dir) {
 230         if (chroot(chroot_dir) < 0) {
 231             error_report("chroot failed");
 232             exit(1);
 233         }
 234         if (chdir("/")) {
 235             error_report("not able to chdir to /: %s", strerror(errno));
 236             exit(1);
 237         }
 238     }
 239
 240 }
 241
 242 void os_daemonize(void)
 243 {
 244     if (daemonize) {
 245         pid_t pid;
 246         int fds[2];
 247
 248         if (pipe(fds) == -1) {
 249             exit(1);
 250         }
 251
 252         pid = fork();
 253         if (pid > 0) {
 254             uint8_t status;
 255             ssize_t len;
 256
 257             close(fds[1]);
 258
 259             do {
 260                 len = read(fds[0], &status, 1);
 261             } while (len < 0 && errno == EINTR);
 262
 263             /* only exit successfully if our child actually wrote
 264              * a one-byte zero to our pipe, upon successful init */
 265             exit(len == 1 && status == 0 ? 0 : 1);
 266
 267         } else if (pid < 0) {
 268             exit(1);
 269         }
 270
 271         close(fds[0]);
 272         daemon_pipe = fds[1];
 273         qemu_set_cloexec(daemon_pipe);
 274
 275         setsid();
 276
 277         pid = fork();
 278         if (pid > 0) {
 279             exit(0);
 280         } else if (pid < 0) {
 281             exit(1);
 282         }
 283         umask(027);
 284
 285         signal(SIGTSTP, SIG_IGN);
 286         signal(SIGTTOU, SIG_IGN);
 287         signal(SIGTTIN, SIG_IGN);
 288     }
 289 }
 290
 291 void os_setup_post(void)
 292 {
 293     int fd = 0;
 294
 295     if (daemonize) {
 296         if (chdir("/")) {
 297             error_report("not able to chdir to /: %s", strerror(errno));
 298             exit(1);
 299         }
 300         TFR(fd = qemu_open("/dev/null", O_RDWR));
 301         if (fd == -1) {
 302             exit(1);
 303         }
 304     }
 305
 306     change_root();
 307     change_process_uid();
 308
 309     if (daemonize) {
 310         uint8_t status = 0;
 311         ssize_t len;
 312
 313         dup2(fd, 0);
 314         dup2(fd, 1);
 315         /* In case -D is given do not redirect stderr to /dev/null */
 316         if (!qemu_logfile) {
 317             dup2(fd, 2);
 318         }
 319
 320         close(fd);
 321
 322         do {
 323             len = write(daemon_pipe, &status, 1);
 324         } while (len < 0 && errno == EINTR);
 325         if (len != 1) {
 326             exit(1);
 327         }
 328     }
 329 }
 330
 331 void os_set_line_buffering(void)
 332 {
 333     setvbuf(stdout, NULL, _IOLBF, 0);
 334 }
 335
 336 bool is_daemonized(void)
 337 {
 338     return daemonize;
 339 }
 340
 341 int os_mlock(void)
 342 {
 343 #ifdef HAVE_MLOCKALL
 344     int ret = 0;
 345
 346     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 347     if (ret < 0) {
 348         error_report("mlockall: %s", strerror(errno));
 349     }
 350
 351     return ret;
 352 #else
 353     return -ENOSYS;
 354 #endif
 355 }