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 "sysemu/sysemu.h"
  34 #include "net/slirp.h"
  35 #include "qemu-options.h"
  36 #include "qemu/error-report.h"
  37 #include "qemu/log.h"
  38 #include "qemu/cutils.h"
  39
  40 #ifdef CONFIG_LINUX
  41 #include <sys/prctl.h>
  42 #endif
  43
  44 /*
  45  * Must set all three of these at once.
  46  * Legal combinations are              unset   by name   by uid
  47  */
  48 static struct passwd *user_pwd;    /*   NULL   non-NULL   NULL   */
  49 static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
  50 static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */
  51
  52 static const char *chroot_dir;
  53 static int daemonize;
  54 static int daemon_pipe;
  55
  56 void os_setup_early_signal_handling(void)
  57 {
  58     struct sigaction act;
  59     sigfillset(&act.sa_mask);
  60     act.sa_flags = 0;
  61     act.sa_handler = SIG_IGN;
  62     sigaction(SIGPIPE, &act, NULL);
  63 }
  64
  65 static void termsig_handler(int signal, siginfo_t *info, void *c)
  66 {
  67     qemu_system_killed(info->si_signo, info->si_pid);
  68 }
  69
  70 void os_setup_signal_handling(void)
  71 {
  72     struct sigaction act;
  73
  74     memset(&act, 0, sizeof(act));
  75     act.sa_sigaction = termsig_handler;
  76     act.sa_flags = SA_SIGINFO;
  77     sigaction(SIGINT,  &act, NULL);
  78     sigaction(SIGHUP,  &act, NULL);
  79     sigaction(SIGTERM, &act, NULL);
  80 }
  81
  82 /* Find a likely location for support files using the location of the binary.
  83    For installed binaries this will be "$bindir/../share/qemu".  When
  84    running from the build tree this will be "$bindir/../pc-bios".  */
  85 #define SHARE_SUFFIX "/share/qemu"
  86 #define BUILD_SUFFIX "/pc-bios"
  87 char *os_find_datadir(void)
  88 {
  89     char *dir, *exec_dir;
  90     char *res;
  91     size_t max_len;
  92
  93     exec_dir = qemu_get_exec_dir();
  94     if (exec_dir == NULL) {
  95         return NULL;
  96     }
  97     dir = g_path_get_dirname(exec_dir);
  98
  99     max_len = strlen(dir) +
 100         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
 101     res = g_malloc0(max_len);
 102     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
 103     if (access(res, R_OK)) {
 104         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
 105         if (access(res, R_OK)) {
 106             g_free(res);
 107             res = NULL;
 108         }
 109     }
 110
 111     g_free(dir);
 112     g_free(exec_dir);
 113     return res;
 114 }
 115 #undef SHARE_SUFFIX
 116 #undef BUILD_SUFFIX
 117
 118 void os_set_proc_name(const char *s)
 119 {
 120 #if defined(PR_SET_NAME)
 121     char name[16];
 122     if (!s)
 123         return;
 124     pstrcpy(name, sizeof(name), s);
 125     /* Could rewrite argv[0] too, but that's a bit more complicated.
 126        This simple way is enough for `top'. */
 127     if (prctl(PR_SET_NAME, name)) {
 128         error_report("unable to change process name: %s", strerror(errno));
 129         exit(1);
 130     }
 131 #else
 132     error_report("Change of process name not supported by your OS");
 133     exit(1);
 134 #endif
 135 }
 136
 137
 138 static bool os_parse_runas_uid_gid(const char *optarg)
 139 {
 140     unsigned long lv;
 141     const char *ep;
 142     uid_t got_uid;
 143     gid_t got_gid;
 144     int rc;
 145
 146     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 147     got_uid = lv; /* overflow here is ID in C99 */
 148     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 149         return false;
 150     }
 151
 152     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 153     got_gid = lv; /* overflow here is ID in C99 */
 154     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 155         return false;
 156     }
 157
 158     user_pwd = NULL;
 159     user_uid = got_uid;
 160     user_gid = got_gid;
 161     return true;
 162 }
 163
 164 /*
 165  * Parse OS specific command line options.
 166  * return 0 if option handled, -1 otherwise
 167  */
 168 int os_parse_cmd_args(int index, const char *optarg)
 169 {
 170     switch (index) {
 171     case QEMU_OPTION_runas:
 172         user_pwd = getpwnam(optarg);
 173         if (user_pwd) {
 174             user_uid = -1;
 175             user_gid = -1;
 176         } else if (!os_parse_runas_uid_gid(optarg)) {
 177             error_report("User \"%s\" doesn't exist"
 178                          " (and is not <uid>:<gid>)",
 179                          optarg);
 180             exit(1);
 181         }
 182         break;
 183     case QEMU_OPTION_chroot:
 184         chroot_dir = optarg;
 185         break;
 186     case QEMU_OPTION_daemonize:
 187         daemonize = 1;
 188         break;
 189 #if defined(CONFIG_LINUX)
 190     case QEMU_OPTION_enablefips:
 191         fips_set_state(true);
 192         break;
 193 #endif
 194     default:
 195         return -1;
 196     }
 197
 198     return 0;
 199 }
 200
 201 static void change_process_uid(void)
 202 {
 203     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 204     assert((user_uid == (uid_t)-1) ==
 205            (user_gid == (gid_t)-1));
 206
 207     if (user_pwd || user_uid != (uid_t)-1) {
 208         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 209         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 210         if (setgid(intended_gid) < 0) {
 211             error_report("Failed to setgid(%d)", intended_gid);
 212             exit(1);
 213         }
 214         if (user_pwd) {
 215             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 216                 error_report("Failed to initgroups(\"%s\", %d)",
 217                         user_pwd->pw_name, user_pwd->pw_gid);
 218                 exit(1);
 219             }
 220         } else {
 221             if (setgroups(1, &user_gid) < 0) {
 222                 error_report("Failed to setgroups(1, [%d])",
 223                         user_gid);
 224                 exit(1);
 225             }
 226         }
 227         if (setuid(intended_uid) < 0) {
 228             error_report("Failed to setuid(%d)", intended_uid);
 229             exit(1);
 230         }
 231         if (setuid(0) != -1) {
 232             error_report("Dropping privileges failed");
 233             exit(1);
 234         }
 235     }
 236 }
 237
 238 static void change_root(void)
 239 {
 240     if (chroot_dir) {
 241         if (chroot(chroot_dir) < 0) {
 242             error_report("chroot failed");
 243             exit(1);
 244         }
 245         if (chdir("/")) {
 246             error_report("not able to chdir to /: %s", strerror(errno));
 247             exit(1);
 248         }
 249     }
 250
 251 }
 252
 253 void os_daemonize(void)
 254 {
 255     if (daemonize) {
 256         pid_t pid;
 257         int fds[2];
 258
 259         if (pipe(fds) == -1) {
 260             exit(1);
 261         }
 262
 263         pid = fork();
 264         if (pid > 0) {
 265             uint8_t status;
 266             ssize_t len;
 267
 268             close(fds[1]);
 269
 270             do {
 271                 len = read(fds[0], &status, 1);
 272             } while (len < 0 && errno == EINTR);
 273
 274             /* only exit successfully if our child actually wrote
 275              * a one-byte zero to our pipe, upon successful init */
 276             exit(len == 1 && status == 0 ? 0 : 1);
 277
 278         } else if (pid < 0) {
 279             exit(1);
 280         }
 281
 282         close(fds[0]);
 283         daemon_pipe = fds[1];
 284         qemu_set_cloexec(daemon_pipe);
 285
 286         setsid();
 287
 288         pid = fork();
 289         if (pid > 0) {
 290             exit(0);
 291         } else if (pid < 0) {
 292             exit(1);
 293         }
 294         umask(027);
 295
 296         signal(SIGTSTP, SIG_IGN);
 297         signal(SIGTTOU, SIG_IGN);
 298         signal(SIGTTIN, SIG_IGN);
 299     }
 300 }
 301
 302 void os_setup_post(void)
 303 {
 304     int fd = 0;
 305
 306     if (daemonize) {
 307         if (chdir("/")) {
 308             error_report("not able to chdir to /: %s", strerror(errno));
 309             exit(1);
 310         }
 311         TFR(fd = qemu_open("/dev/null", O_RDWR));
 312         if (fd == -1) {
 313             exit(1);
 314         }
 315     }
 316
 317     change_root();
 318     change_process_uid();
 319
 320     if (daemonize) {
 321         uint8_t status = 0;
 322         ssize_t len;
 323
 324         dup2(fd, 0);
 325         dup2(fd, 1);
 326         /* In case -D is given do not redirect stderr to /dev/null */
 327         if (!qemu_logfile) {
 328             dup2(fd, 2);
 329         }
 330
 331         close(fd);
 332
 333         do {
 334             len = write(daemon_pipe, &status, 1);
 335         } while (len < 0 && errno == EINTR);
 336         if (len != 1) {
 337             exit(1);
 338         }
 339     }
 340 }
 341
 342 void os_set_line_buffering(void)
 343 {
 344     setvbuf(stdout, NULL, _IOLBF, 0);
 345 }
 346
 347 bool is_daemonized(void)
 348 {
 349     return daemonize;
 350 }
 351
 352 int os_mlock(void)
 353 {
 354     int ret = 0;
 355
 356     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 357     if (ret < 0) {
 358         error_report("mlockall: %s", strerror(errno));
 359     }
 360
 361     return ret;
 362 }