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 char *os_find_datadir(void)
  89 {
  90     g_autofree char *exec_dir = NULL;
  91     g_autofree char *dir = NULL;
  92
  93     exec_dir = qemu_get_exec_dir();
  94     g_return_val_if_fail(exec_dir != NULL, NULL);
  95
  96     dir = g_build_filename(exec_dir, "..", "pc-bios", NULL);
  97     if (g_file_test(dir, G_FILE_TEST_IS_DIR)) {
  98         return g_steal_pointer(&dir);
  99     }
 100
 101     return g_strdup(CONFIG_QEMU_DATADIR);
 102 }
 103
 104 void os_set_proc_name(const char *s)
 105 {
 106 #if defined(PR_SET_NAME)
 107     char name[16];
 108     if (!s)
 109         return;
 110     pstrcpy(name, sizeof(name), s);
 111     /* Could rewrite argv[0] too, but that's a bit more complicated.
 112        This simple way is enough for `top'. */
 113     if (prctl(PR_SET_NAME, name)) {
 114         error_report("unable to change process name: %s", strerror(errno));
 115         exit(1);
 116     }
 117 #else
 118     error_report("Change of process name not supported by your OS");
 119     exit(1);
 120 #endif
 121 }
 122
 123
 124 static bool os_parse_runas_uid_gid(const char *optarg)
 125 {
 126     unsigned long lv;
 127     const char *ep;
 128     uid_t got_uid;
 129     gid_t got_gid;
 130     int rc;
 131
 132     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 133     got_uid = lv; /* overflow here is ID in C99 */
 134     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 135         return false;
 136     }
 137
 138     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 139     got_gid = lv; /* overflow here is ID in C99 */
 140     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 141         return false;
 142     }
 143
 144     user_pwd = NULL;
 145     user_uid = got_uid;
 146     user_gid = got_gid;
 147     return true;
 148 }
 149
 150 /*
 151  * Parse OS specific command line options.
 152  * return 0 if option handled, -1 otherwise
 153  */
 154 int os_parse_cmd_args(int index, const char *optarg)
 155 {
 156     switch (index) {
 157     case QEMU_OPTION_runas:
 158         user_pwd = getpwnam(optarg);
 159         if (user_pwd) {
 160             user_uid = -1;
 161             user_gid = -1;
 162         } else if (!os_parse_runas_uid_gid(optarg)) {
 163             error_report("User \"%s\" doesn't exist"
 164                          " (and is not <uid>:<gid>)",
 165                          optarg);
 166             exit(1);
 167         }
 168         break;
 169     case QEMU_OPTION_chroot:
 170         chroot_dir = optarg;
 171         break;
 172     case QEMU_OPTION_daemonize:
 173         daemonize = 1;
 174         break;
 175 #if defined(CONFIG_LINUX)
 176     case QEMU_OPTION_enablefips:
 177         fips_set_state(true);
 178         break;
 179 #endif
 180     default:
 181         return -1;
 182     }
 183
 184     return 0;
 185 }
 186
 187 static void change_process_uid(void)
 188 {
 189     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 190     assert((user_uid == (uid_t)-1) ==
 191            (user_gid == (gid_t)-1));
 192
 193     if (user_pwd || user_uid != (uid_t)-1) {
 194         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 195         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 196         if (setgid(intended_gid) < 0) {
 197             error_report("Failed to setgid(%d)", intended_gid);
 198             exit(1);
 199         }
 200         if (user_pwd) {
 201             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 202                 error_report("Failed to initgroups(\"%s\", %d)",
 203                         user_pwd->pw_name, user_pwd->pw_gid);
 204                 exit(1);
 205             }
 206         } else {
 207             if (setgroups(1, &user_gid) < 0) {
 208                 error_report("Failed to setgroups(1, [%d])",
 209                         user_gid);
 210                 exit(1);
 211             }
 212         }
 213         if (setuid(intended_uid) < 0) {
 214             error_report("Failed to setuid(%d)", intended_uid);
 215             exit(1);
 216         }
 217         if (setuid(0) != -1) {
 218             error_report("Dropping privileges failed");
 219             exit(1);
 220         }
 221     }
 222 }
 223
 224 static void change_root(void)
 225 {
 226     if (chroot_dir) {
 227         if (chroot(chroot_dir) < 0) {
 228             error_report("chroot failed");
 229             exit(1);
 230         }
 231         if (chdir("/")) {
 232             error_report("not able to chdir to /: %s", strerror(errno));
 233             exit(1);
 234         }
 235     }
 236
 237 }
 238
 239 void os_daemonize(void)
 240 {
 241     if (daemonize) {
 242         pid_t pid;
 243         int fds[2];
 244
 245         if (pipe(fds) == -1) {
 246             exit(1);
 247         }
 248
 249         pid = fork();
 250         if (pid > 0) {
 251             uint8_t status;
 252             ssize_t len;
 253
 254             close(fds[1]);
 255
 256             do {
 257                 len = read(fds[0], &status, 1);
 258             } while (len < 0 && errno == EINTR);
 259
 260             /* only exit successfully if our child actually wrote
 261              * a one-byte zero to our pipe, upon successful init */
 262             exit(len == 1 && status == 0 ? 0 : 1);
 263
 264         } else if (pid < 0) {
 265             exit(1);
 266         }
 267
 268         close(fds[0]);
 269         daemon_pipe = fds[1];
 270         qemu_set_cloexec(daemon_pipe);
 271
 272         setsid();
 273
 274         pid = fork();
 275         if (pid > 0) {
 276             exit(0);
 277         } else if (pid < 0) {
 278             exit(1);
 279         }
 280         umask(027);
 281
 282         signal(SIGTSTP, SIG_IGN);
 283         signal(SIGTTOU, SIG_IGN);
 284         signal(SIGTTIN, SIG_IGN);
 285     }
 286 }
 287
 288 void os_setup_post(void)
 289 {
 290     int fd = 0;
 291
 292     if (daemonize) {
 293         if (chdir("/")) {
 294             error_report("not able to chdir to /: %s", strerror(errno));
 295             exit(1);
 296         }
 297         TFR(fd = qemu_open("/dev/null", O_RDWR));
 298         if (fd == -1) {
 299             exit(1);
 300         }
 301     }
 302
 303     change_root();
 304     change_process_uid();
 305
 306     if (daemonize) {
 307         uint8_t status = 0;
 308         ssize_t len;
 309
 310         dup2(fd, 0);
 311         dup2(fd, 1);
 312         /* In case -D is given do not redirect stderr to /dev/null */
 313         if (!qemu_logfile) {
 314             dup2(fd, 2);
 315         }
 316
 317         close(fd);
 318
 319         do {
 320             len = write(daemon_pipe, &status, 1);
 321         } while (len < 0 && errno == EINTR);
 322         if (len != 1) {
 323             exit(1);
 324         }
 325     }
 326 }
 327
 328 void os_set_line_buffering(void)
 329 {
 330     setvbuf(stdout, NULL, _IOLBF, 0);
 331 }
 332
 333 bool is_daemonized(void)
 334 {
 335     return daemonize;
 336 }
 337
 338 int os_mlock(void)
 339 {
 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 }