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 /* Find a likely location for support files using the location of the binary.
  84    For installed binaries this will be "$bindir/../share/qemu".  When
  85    running from the build tree this will be "$bindir/../pc-bios".  */
  86 #define SHARE_SUFFIX "/share/qemu"
  87 #define BUILD_SUFFIX "/pc-bios"
  88 char *os_find_datadir(void)
  89 {
  90     char *dir, *exec_dir;
  91     char *res;
  92     size_t max_len;
  93
  94     exec_dir = qemu_get_exec_dir();
  95     if (exec_dir == NULL) {
  96         return NULL;
  97     }
  98     dir = g_path_get_dirname(exec_dir);
  99
 100     max_len = strlen(dir) +
 101         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
 102     res = g_malloc0(max_len);
 103     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
 104     if (access(res, R_OK)) {
 105         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
 106         if (access(res, R_OK)) {
 107             g_free(res);
 108             res = NULL;
 109         }
 110     }
 111
 112     g_free(dir);
 113     g_free(exec_dir);
 114     return res;
 115 }
 116 #undef SHARE_SUFFIX
 117 #undef BUILD_SUFFIX
 118
 119 void os_set_proc_name(const char *s)
 120 {
 121 #if defined(PR_SET_NAME)
 122     char name[16];
 123     if (!s)
 124         return;
 125     pstrcpy(name, sizeof(name), s);
 126     /* Could rewrite argv[0] too, but that's a bit more complicated.
 127        This simple way is enough for `top'. */
 128     if (prctl(PR_SET_NAME, name)) {
 129         error_report("unable to change process name: %s", strerror(errno));
 130         exit(1);
 131     }
 132 #else
 133     error_report("Change of process name not supported by your OS");
 134     exit(1);
 135 #endif
 136 }
 137
 138
 139 static bool os_parse_runas_uid_gid(const char *optarg)
 140 {
 141     unsigned long lv;
 142     const char *ep;
 143     uid_t got_uid;
 144     gid_t got_gid;
 145     int rc;
 146
 147     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 148     got_uid = lv; /* overflow here is ID in C99 */
 149     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 150         return false;
 151     }
 152
 153     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 154     got_gid = lv; /* overflow here is ID in C99 */
 155     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 156         return false;
 157     }
 158
 159     user_pwd = NULL;
 160     user_uid = got_uid;
 161     user_gid = got_gid;
 162     return true;
 163 }
 164
 165 /*
 166  * Parse OS specific command line options.
 167  * return 0 if option handled, -1 otherwise
 168  */
 169 int os_parse_cmd_args(int index, const char *optarg)
 170 {
 171     switch (index) {
 172     case QEMU_OPTION_runas:
 173         user_pwd = getpwnam(optarg);
 174         if (user_pwd) {
 175             user_uid = -1;
 176             user_gid = -1;
 177         } else if (!os_parse_runas_uid_gid(optarg)) {
 178             error_report("User \"%s\" doesn't exist"
 179                          " (and is not <uid>:<gid>)",
 180                          optarg);
 181             exit(1);
 182         }
 183         break;
 184     case QEMU_OPTION_chroot:
 185         chroot_dir = optarg;
 186         break;
 187     case QEMU_OPTION_daemonize:
 188         daemonize = 1;
 189         break;
 190 #if defined(CONFIG_LINUX)
 191     case QEMU_OPTION_enablefips:
 192         fips_set_state(true);
 193         break;
 194 #endif
 195     default:
 196         return -1;
 197     }
 198
 199     return 0;
 200 }
 201
 202 static void change_process_uid(void)
 203 {
 204     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 205     assert((user_uid == (uid_t)-1) ==
 206            (user_gid == (gid_t)-1));
 207
 208     if (user_pwd || user_uid != (uid_t)-1) {
 209         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 210         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 211         if (setgid(intended_gid) < 0) {
 212             error_report("Failed to setgid(%d)", intended_gid);
 213             exit(1);
 214         }
 215         if (user_pwd) {
 216             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 217                 error_report("Failed to initgroups(\"%s\", %d)",
 218                         user_pwd->pw_name, user_pwd->pw_gid);
 219                 exit(1);
 220             }
 221         } else {
 222             if (setgroups(1, &user_gid) < 0) {
 223                 error_report("Failed to setgroups(1, [%d])",
 224                         user_gid);
 225                 exit(1);
 226             }
 227         }
 228         if (setuid(intended_uid) < 0) {
 229             error_report("Failed to setuid(%d)", intended_uid);
 230             exit(1);
 231         }
 232         if (setuid(0) != -1) {
 233             error_report("Dropping privileges failed");
 234             exit(1);
 235         }
 236     }
 237 }
 238
 239 static void change_root(void)
 240 {
 241     if (chroot_dir) {
 242         if (chroot(chroot_dir) < 0) {
 243             error_report("chroot failed");
 244             exit(1);
 245         }
 246         if (chdir("/")) {
 247             error_report("not able to chdir to /: %s", strerror(errno));
 248             exit(1);
 249         }
 250     }
 251
 252 }
 253
 254 void os_daemonize(void)
 255 {
 256     if (daemonize) {
 257         pid_t pid;
 258         int fds[2];
 259
 260         if (pipe(fds) == -1) {
 261             exit(1);
 262         }
 263
 264         pid = fork();
 265         if (pid > 0) {
 266             uint8_t status;
 267             ssize_t len;
 268
 269             close(fds[1]);
 270
 271             do {
 272                 len = read(fds[0], &status, 1);
 273             } while (len < 0 && errno == EINTR);
 274
 275             /* only exit successfully if our child actually wrote
 276              * a one-byte zero to our pipe, upon successful init */
 277             exit(len == 1 && status == 0 ? 0 : 1);
 278
 279         } else if (pid < 0) {
 280             exit(1);
 281         }
 282
 283         close(fds[0]);
 284         daemon_pipe = fds[1];
 285         qemu_set_cloexec(daemon_pipe);
 286
 287         setsid();
 288
 289         pid = fork();
 290         if (pid > 0) {
 291             exit(0);
 292         } else if (pid < 0) {
 293             exit(1);
 294         }
 295         umask(027);
 296
 297         signal(SIGTSTP, SIG_IGN);
 298         signal(SIGTTOU, SIG_IGN);
 299         signal(SIGTTIN, SIG_IGN);
 300     }
 301 }
 302
 303 void os_setup_post(void)
 304 {
 305     int fd = 0;
 306
 307     if (daemonize) {
 308         if (chdir("/")) {
 309             error_report("not able to chdir to /: %s", strerror(errno));
 310             exit(1);
 311         }
 312         TFR(fd = qemu_open("/dev/null", O_RDWR));
 313         if (fd == -1) {
 314             exit(1);
 315         }
 316     }
 317
 318     change_root();
 319     change_process_uid();
 320
 321     if (daemonize) {
 322         uint8_t status = 0;
 323         ssize_t len;
 324
 325         dup2(fd, 0);
 326         dup2(fd, 1);
 327         /* In case -D is given do not redirect stderr to /dev/null */
 328         if (!qemu_logfile) {
 329             dup2(fd, 2);
 330         }
 331
 332         close(fd);
 333
 334         do {
 335             len = write(daemon_pipe, &status, 1);
 336         } while (len < 0 && errno == EINTR);
 337         if (len != 1) {
 338             exit(1);
 339         }
 340     }
 341 }
 342
 343 void os_set_line_buffering(void)
 344 {
 345     setvbuf(stdout, NULL, _IOLBF, 0);
 346 }
 347
 348 bool is_daemonized(void)
 349 {
 350     return daemonize;
 351 }
 352
 353 int os_mlock(void)
 354 {
 355     int ret = 0;
 356
 357     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 358     if (ret < 0) {
 359         error_report("mlockall: %s", strerror(errno));
 360     }
 361
 362     return ret;
 363 }