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 "net/slirp.h"
  34 #include "qemu/qemu-options.h"
  35 #include "qemu/error-report.h"
  36 #include "qemu/log.h"
  37 #include "sysemu/runstate.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 void os_set_proc_name(const char *s)
  83 {
  84 #if defined(PR_SET_NAME)
  85     char name[16];
  86     if (!s)
  87         return;
  88     pstrcpy(name, sizeof(name), s);
  89     /* Could rewrite argv[0] too, but that's a bit more complicated.
  90        This simple way is enough for `top'. */
  91     if (prctl(PR_SET_NAME, name)) {
  92         error_report("unable to change process name: %s", strerror(errno));
  93         exit(1);
  94     }
  95 #else
  96     error_report("Change of process name not supported by your OS");
  97     exit(1);
  98 #endif
  99 }
 100
 101
 102 static bool os_parse_runas_uid_gid(const char *optarg)
 103 {
 104     unsigned long lv;
 105     const char *ep;
 106     uid_t got_uid;
 107     gid_t got_gid;
 108     int rc;
 109
 110     rc = qemu_strtoul(optarg, &ep, 0, &lv);
 111     got_uid = lv; /* overflow here is ID in C99 */
 112     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 113         return false;
 114     }
 115
 116     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 117     got_gid = lv; /* overflow here is ID in C99 */
 118     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 119         return false;
 120     }
 121
 122     user_pwd = NULL;
 123     user_uid = got_uid;
 124     user_gid = got_gid;
 125     return true;
 126 }
 127
 128 /*
 129  * Parse OS specific command line options.
 130  * return 0 if option handled, -1 otherwise
 131  */
 132 int os_parse_cmd_args(int index, const char *optarg)
 133 {
 134     switch (index) {
 135     case QEMU_OPTION_runas:
 136         user_pwd = getpwnam(optarg);
 137         if (user_pwd) {
 138             user_uid = -1;
 139             user_gid = -1;
 140         } else if (!os_parse_runas_uid_gid(optarg)) {
 141             error_report("User \"%s\" doesn't exist"
 142                          " (and is not <uid>:<gid>)",
 143                          optarg);
 144             exit(1);
 145         }
 146         break;
 147     case QEMU_OPTION_chroot:
 148         chroot_dir = optarg;
 149         break;
 150     case QEMU_OPTION_daemonize:
 151         daemonize = 1;
 152         break;
 153     default:
 154         return -1;
 155     }
 156
 157     return 0;
 158 }
 159
 160 static void change_process_uid(void)
 161 {
 162     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 163     assert((user_uid == (uid_t)-1) ==
 164            (user_gid == (gid_t)-1));
 165
 166     if (user_pwd || user_uid != (uid_t)-1) {
 167         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 168         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 169         if (setgid(intended_gid) < 0) {
 170             error_report("Failed to setgid(%d)", intended_gid);
 171             exit(1);
 172         }
 173         if (user_pwd) {
 174             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 175                 error_report("Failed to initgroups(\"%s\", %d)",
 176                         user_pwd->pw_name, user_pwd->pw_gid);
 177                 exit(1);
 178             }
 179         } else {
 180             if (setgroups(1, &user_gid) < 0) {
 181                 error_report("Failed to setgroups(1, [%d])",
 182                         user_gid);
 183                 exit(1);
 184             }
 185         }
 186         if (setuid(intended_uid) < 0) {
 187             error_report("Failed to setuid(%d)", intended_uid);
 188             exit(1);
 189         }
 190         if (setuid(0) != -1) {
 191             error_report("Dropping privileges failed");
 192             exit(1);
 193         }
 194     }
 195 }
 196
 197 static void change_root(void)
 198 {
 199     if (chroot_dir) {
 200         if (chroot(chroot_dir) < 0) {
 201             error_report("chroot failed");
 202             exit(1);
 203         }
 204         if (chdir("/")) {
 205             error_report("not able to chdir to /: %s", strerror(errno));
 206             exit(1);
 207         }
 208     }
 209
 210 }
 211
 212 void os_daemonize(void)
 213 {
 214     if (daemonize) {
 215         pid_t pid;
 216         int fds[2];
 217
 218         if (pipe(fds) == -1) {
 219             exit(1);
 220         }
 221
 222         pid = fork();
 223         if (pid > 0) {
 224             uint8_t status;
 225             ssize_t len;
 226
 227             close(fds[1]);
 228
 229             do {
 230                 len = read(fds[0], &status, 1);
 231             } while (len < 0 && errno == EINTR);
 232
 233             /* only exit successfully if our child actually wrote
 234              * a one-byte zero to our pipe, upon successful init */
 235             exit(len == 1 && status == 0 ? 0 : 1);
 236
 237         } else if (pid < 0) {
 238             exit(1);
 239         }
 240
 241         close(fds[0]);
 242         daemon_pipe = fds[1];
 243         qemu_set_cloexec(daemon_pipe);
 244
 245         setsid();
 246
 247         pid = fork();
 248         if (pid > 0) {
 249             exit(0);
 250         } else if (pid < 0) {
 251             exit(1);
 252         }
 253         umask(027);
 254
 255         signal(SIGTSTP, SIG_IGN);
 256         signal(SIGTTOU, SIG_IGN);
 257         signal(SIGTTIN, SIG_IGN);
 258     }
 259 }
 260
 261 void os_setup_post(void)
 262 {
 263     int fd = 0;
 264
 265     if (daemonize) {
 266         if (chdir("/")) {
 267             error_report("not able to chdir to /: %s", strerror(errno));
 268             exit(1);
 269         }
 270         TFR(fd = qemu_open_old("/dev/null", O_RDWR));
 271         if (fd == -1) {
 272             exit(1);
 273         }
 274     }
 275
 276     change_root();
 277     change_process_uid();
 278
 279     if (daemonize) {
 280         uint8_t status = 0;
 281         ssize_t len;
 282
 283         dup2(fd, 0);
 284         dup2(fd, 1);
 285         /* In case -D is given do not redirect stderr to /dev/null */
 286         if (!qemu_log_enabled()) {
 287             dup2(fd, 2);
 288         }
 289
 290         close(fd);
 291
 292         do {
 293             len = write(daemon_pipe, &status, 1);
 294         } while (len < 0 && errno == EINTR);
 295         if (len != 1) {
 296             exit(1);
 297         }
 298     }
 299 }
 300
 301 void os_set_line_buffering(void)
 302 {
 303     setvbuf(stdout, NULL, _IOLBF, 0);
 304 }
 305
 306 bool is_daemonized(void)
 307 {
 308     return daemonize;
 309 }
 310
 311 int os_set_daemonize(bool d)
 312 {
 313     daemonize = d;
 314     return 0;
 315 }
 316
 317 int os_mlock(void)
 318 {
 319 #ifdef HAVE_MLOCKALL
 320     int ret = 0;
 321
 322     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 323     if (ret < 0) {
 324         error_report("mlockall: %s", strerror(errno));
 325     }
 326
 327     return ret;
 328 #else
 329     return -ENOSYS;
 330 #endif
 331 }