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 #ifdef CONFIG_SLIRP
 172     case QEMU_OPTION_smb:
 173         error_report("The -smb option is deprecated. "
 174                      "Please use '-netdev user,smb=...' instead.");
 175         if (net_slirp_smb(optarg) < 0)
 176             exit(1);
 177         break;
 178 #endif
 179     case QEMU_OPTION_runas:
 180         user_pwd = getpwnam(optarg);
 181         if (user_pwd) {
 182             user_uid = -1;
 183             user_gid = -1;
 184         } else if (!os_parse_runas_uid_gid(optarg)) {
 185             error_report("User \"%s\" doesn't exist"
 186                          " (and is not <uid>:<gid>)",
 187                          optarg);
 188             exit(1);
 189         }
 190         break;
 191     case QEMU_OPTION_chroot:
 192         chroot_dir = optarg;
 193         break;
 194     case QEMU_OPTION_daemonize:
 195         daemonize = 1;
 196         break;
 197 #if defined(CONFIG_LINUX)
 198     case QEMU_OPTION_enablefips:
 199         fips_set_state(true);
 200         break;
 201 #endif
 202     default:
 203         return -1;
 204     }
 205
 206     return 0;
 207 }
 208
 209 static void change_process_uid(void)
 210 {
 211     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 212     assert((user_uid == (uid_t)-1) ==
 213            (user_gid == (gid_t)-1));
 214
 215     if (user_pwd || user_uid != (uid_t)-1) {
 216         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 217         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 218         if (setgid(intended_gid) < 0) {
 219             error_report("Failed to setgid(%d)", intended_gid);
 220             exit(1);
 221         }
 222         if (user_pwd) {
 223             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 224                 error_report("Failed to initgroups(\"%s\", %d)",
 225                         user_pwd->pw_name, user_pwd->pw_gid);
 226                 exit(1);
 227             }
 228         } else {
 229             if (setgroups(1, &user_gid) < 0) {
 230                 error_report("Failed to setgroups(1, [%d])",
 231                         user_gid);
 232                 exit(1);
 233             }
 234         }
 235         if (setuid(intended_uid) < 0) {
 236             error_report("Failed to setuid(%d)", intended_uid);
 237             exit(1);
 238         }
 239         if (setuid(0) != -1) {
 240             error_report("Dropping privileges failed");
 241             exit(1);
 242         }
 243     }
 244 }
 245
 246 static void change_root(void)
 247 {
 248     if (chroot_dir) {
 249         if (chroot(chroot_dir) < 0) {
 250             error_report("chroot failed");
 251             exit(1);
 252         }
 253         if (chdir("/")) {
 254             error_report("not able to chdir to /: %s", strerror(errno));
 255             exit(1);
 256         }
 257     }
 258
 259 }
 260
 261 void os_daemonize(void)
 262 {
 263     if (daemonize) {
 264         pid_t pid;
 265         int fds[2];
 266
 267         if (pipe(fds) == -1) {
 268             exit(1);
 269         }
 270
 271         pid = fork();
 272         if (pid > 0) {
 273             uint8_t status;
 274             ssize_t len;
 275
 276             close(fds[1]);
 277
 278             do {
 279                 len = read(fds[0], &status, 1);
 280             } while (len < 0 && errno == EINTR);
 281
 282             /* only exit successfully if our child actually wrote
 283              * a one-byte zero to our pipe, upon successful init */
 284             exit(len == 1 && status == 0 ? 0 : 1);
 285
 286         } else if (pid < 0) {
 287             exit(1);
 288         }
 289
 290         close(fds[0]);
 291         daemon_pipe = fds[1];
 292         qemu_set_cloexec(daemon_pipe);
 293
 294         setsid();
 295
 296         pid = fork();
 297         if (pid > 0) {
 298             exit(0);
 299         } else if (pid < 0) {
 300             exit(1);
 301         }
 302         umask(027);
 303
 304         signal(SIGTSTP, SIG_IGN);
 305         signal(SIGTTOU, SIG_IGN);
 306         signal(SIGTTIN, SIG_IGN);
 307     }
 308 }
 309
 310 void os_setup_post(void)
 311 {
 312     int fd = 0;
 313
 314     if (daemonize) {
 315         if (chdir("/")) {
 316             error_report("not able to chdir to /: %s", strerror(errno));
 317             exit(1);
 318         }
 319         TFR(fd = qemu_open("/dev/null", O_RDWR));
 320         if (fd == -1) {
 321             exit(1);
 322         }
 323     }
 324
 325     change_root();
 326     change_process_uid();
 327
 328     if (daemonize) {
 329         uint8_t status = 0;
 330         ssize_t len;
 331
 332         dup2(fd, 0);
 333         dup2(fd, 1);
 334         /* In case -D is given do not redirect stderr to /dev/null */
 335         if (!qemu_logfile) {
 336             dup2(fd, 2);
 337         }
 338
 339         close(fd);
 340
 341         do {
 342             len = write(daemon_pipe, &status, 1);
 343         } while (len < 0 && errno == EINTR);
 344         if (len != 1) {
 345             exit(1);
 346         }
 347     }
 348 }
 349
 350 void os_set_line_buffering(void)
 351 {
 352     setvbuf(stdout, NULL, _IOLBF, 0);
 353 }
 354
 355 int qemu_create_pidfile(const char *filename)
 356 {
 357     char buffer[128];
 358     int len;
 359     int fd;
 360
 361     fd = qemu_open(filename, O_RDWR | O_CREAT, 0600);
 362     if (fd == -1) {
 363         return -1;
 364     }
 365     if (lockf(fd, F_TLOCK, 0) == -1) {
 366         close(fd);
 367         return -1;
 368     }
 369     len = snprintf(buffer, sizeof(buffer), FMT_pid "\n", getpid());
 370     if (write(fd, buffer, len) != len) {
 371         close(fd);
 372         return -1;
 373     }
 374
 375     /* keep pidfile open & locked forever */
 376     return 0;
 377 }
 378
 379 bool is_daemonized(void)
 380 {
 381     return daemonize;
 382 }
 383
 384 int os_mlock(void)
 385 {
 386     int ret = 0;
 387
 388     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 389     if (ret < 0) {
 390         error_report("mlockall: %s", strerror(errno));
 391     }
 392
 393     return ret;
 394 }