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/error-report.h"
  33 #include "qemu/log.h"
  34 #include "sysemu/runstate.h"
  35 #include "qemu/cutils.h"
  36
  37 #ifdef CONFIG_LINUX
  38 #include <sys/prctl.h>
  39 #endif
  40
  41
  42 void os_setup_early_signal_handling(void)
  43 {
  44     struct sigaction act;
  45     sigfillset(&act.sa_mask);
  46     act.sa_flags = 0;
  47     act.sa_handler = SIG_IGN;
  48     sigaction(SIGPIPE, &act, NULL);
  49 }
  50
  51 static void termsig_handler(int signal, siginfo_t *info, void *c)
  52 {
  53     qemu_system_killed(info->si_signo, info->si_pid);
  54 }
  55
  56 void os_setup_signal_handling(void)
  57 {
  58     struct sigaction act;
  59
  60     memset(&act, 0, sizeof(act));
  61     act.sa_sigaction = termsig_handler;
  62     act.sa_flags = SA_SIGINFO;
  63     sigaction(SIGINT,  &act, NULL);
  64     sigaction(SIGHUP,  &act, NULL);
  65     sigaction(SIGTERM, &act, NULL);
  66 }
  67
  68 void os_set_proc_name(const char *s)
  69 {
  70 #if defined(PR_SET_NAME)
  71     char name[16];
  72     if (!s)
  73         return;
  74     pstrcpy(name, sizeof(name), s);
  75     /* Could rewrite argv[0] too, but that's a bit more complicated.
  76        This simple way is enough for `top'. */
  77     if (prctl(PR_SET_NAME, name)) {
  78         error_report("unable to change process name: %s", strerror(errno));
  79         exit(1);
  80     }
  81 #else
  82     error_report("Change of process name not supported by your OS");
  83     exit(1);
  84 #endif
  85 }
  86
  87
  88 /*
  89  * Must set all three of these at once.
  90  * Legal combinations are              unset   by name   by uid
  91  */
  92 static struct passwd *user_pwd;    /*   NULL   non-NULL   NULL   */
  93 static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
  94 static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */
  95
  96 /*
  97  * Prepare to change user ID. user_id can be one of 3 forms:
  98  *   - a username, in which case user ID will be changed to its uid,
  99  *     with primary and supplementary groups set up too;
 100  *   - a numeric uid, in which case only the uid will be set;
 101  *   - a pair of numeric uid:gid.
 102  */
 103 bool os_set_runas(const char *user_id)
 104 {
 105     unsigned long lv;
 106     const char *ep;
 107     uid_t got_uid;
 108     gid_t got_gid;
 109     int rc;
 110
 111     user_pwd = getpwnam(user_id);
 112     if (user_pwd) {
 113         user_uid = -1;
 114         user_gid = -1;
 115         return true;
 116     }
 117
 118     rc = qemu_strtoul(user_id, &ep, 0, &lv);
 119     got_uid = lv; /* overflow here is ID in C99 */
 120     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
 121         return false;
 122     }
 123
 124     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
 125     got_gid = lv; /* overflow here is ID in C99 */
 126     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
 127         return false;
 128     }
 129
 130     user_pwd = NULL;
 131     user_uid = got_uid;
 132     user_gid = got_gid;
 133     return true;
 134 }
 135
 136 static void change_process_uid(void)
 137 {
 138     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
 139     assert((user_uid == (uid_t)-1) ==
 140            (user_gid == (gid_t)-1));
 141
 142     if (user_pwd || user_uid != (uid_t)-1) {
 143         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
 144         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
 145         if (setgid(intended_gid) < 0) {
 146             error_report("Failed to setgid(%d)", intended_gid);
 147             exit(1);
 148         }
 149         if (user_pwd) {
 150             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 151                 error_report("Failed to initgroups(\"%s\", %d)",
 152                         user_pwd->pw_name, user_pwd->pw_gid);
 153                 exit(1);
 154             }
 155         } else {
 156             if (setgroups(1, &user_gid) < 0) {
 157                 error_report("Failed to setgroups(1, [%d])",
 158                         user_gid);
 159                 exit(1);
 160             }
 161         }
 162         if (setuid(intended_uid) < 0) {
 163             error_report("Failed to setuid(%d)", intended_uid);
 164             exit(1);
 165         }
 166         if (setuid(0) != -1) {
 167             error_report("Dropping privileges failed");
 168             exit(1);
 169         }
 170     }
 171 }
 172
 173
 174 static const char *chroot_dir;
 175
 176 void os_set_chroot(const char *path)
 177 {
 178     chroot_dir = path;
 179 }
 180
 181 static void change_root(void)
 182 {
 183     if (chroot_dir) {
 184         if (chroot(chroot_dir) < 0) {
 185             error_report("chroot failed");
 186             exit(1);
 187         }
 188         if (chdir("/")) {
 189             error_report("not able to chdir to /: %s", strerror(errno));
 190             exit(1);
 191         }
 192     }
 193
 194 }
 195
 196
 197 static int daemonize;
 198 static int daemon_pipe;
 199
 200 bool is_daemonized(void)
 201 {
 202     return daemonize;
 203 }
 204
 205 int os_set_daemonize(bool d)
 206 {
 207     daemonize = d;
 208     return 0;
 209 }
 210
 211 void os_daemonize(void)
 212 {
 213     if (daemonize) {
 214         pid_t pid;
 215         int fds[2];
 216
 217         if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
 218             exit(1);
 219         }
 220
 221         pid = fork();
 222         if (pid > 0) {
 223             uint8_t status;
 224             ssize_t len;
 225
 226             close(fds[1]);
 227
 228             do {
 229                 len = read(fds[0], &status, 1);
 230             } while (len < 0 && errno == EINTR);
 231
 232             /* only exit successfully if our child actually wrote
 233              * a one-byte zero to our pipe, upon successful init */
 234             exit(len == 1 && status == 0 ? 0 : 1);
 235
 236         } else if (pid < 0) {
 237             exit(1);
 238         }
 239
 240         close(fds[0]);
 241         daemon_pipe = fds[1];
 242
 243         setsid();
 244
 245         pid = fork();
 246         if (pid > 0) {
 247             exit(0);
 248         } else if (pid < 0) {
 249             exit(1);
 250         }
 251         umask(027);
 252
 253         signal(SIGTSTP, SIG_IGN);
 254         signal(SIGTTOU, SIG_IGN);
 255         signal(SIGTTIN, SIG_IGN);
 256     }
 257 }
 258
 259 void os_setup_post(void)
 260 {
 261     int fd = 0;
 262
 263     if (daemonize) {
 264         if (chdir("/")) {
 265             error_report("not able to chdir to /: %s", strerror(errno));
 266             exit(1);
 267         }
 268         fd = RETRY_ON_EINTR(qemu_open_old("/dev/null", O_RDWR));
 269         if (fd == -1) {
 270             exit(1);
 271         }
 272     }
 273
 274     change_root();
 275     change_process_uid();
 276
 277     if (daemonize) {
 278         uint8_t status = 0;
 279         ssize_t len;
 280
 281         dup2(fd, 0);
 282         dup2(fd, 1);
 283         /* In case -D is given do not redirect stderr to /dev/null */
 284         if (!qemu_log_enabled()) {
 285             dup2(fd, 2);
 286         }
 287
 288         close(fd);
 289
 290         do {
 291             len = write(daemon_pipe, &status, 1);
 292         } while (len < 0 && errno == EINTR);
 293         if (len != 1) {
 294             exit(1);
 295         }
 296     }
 297 }
 298
 299 void os_set_line_buffering(void)
 300 {
 301     setvbuf(stdout, NULL, _IOLBF, 0);
 302 }
 303
 304 int os_mlock(void)
 305 {
 306 #ifdef HAVE_MLOCKALL
 307     int ret = 0;
 308
 309     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
 310     if (ret < 0) {
 311         error_report("mlockall: %s", strerror(errno));
 312     }
 313
 314     return ret;
 315 #else
 316     return -ENOSYS;
 317 #endif
 318 }