aboutsummaryrefslogtreecommitdiff
path: root/os-posix.c
blob: 321fc4bd13b84e882a60bb8d9a839798b67a5da1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
/*
 * os-posix.c
 *
 * Copyright (c) 2003-2008 Fabrice Bellard
 * Copyright (c) 2010 Red Hat, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include <sys/wait.h>
#include <pwd.h>
#include <grp.h>
#include <libgen.h>

/* Needed early for CONFIG_BSD etc. */
#include "net/slirp.h"
#include "qemu/qemu-options.h"
#include "qemu/error-report.h"
#include "qemu/log.h"
#include "sysemu/runstate.h"
#include "qemu/cutils.h"

#ifdef CONFIG_LINUX
#include <sys/prctl.h>
#endif

/*
 * Must set all three of these at once.
 * Legal combinations are              unset   by name   by uid
 */
static struct passwd *user_pwd;    /*   NULL   non-NULL   NULL   */
static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */

static const char *chroot_dir;
static int daemonize;
static int daemon_pipe;

void os_setup_early_signal_handling(void)
{
    struct sigaction act;
    sigfillset(&act.sa_mask);
    act.sa_flags = 0;
    act.sa_handler = SIG_IGN;
    sigaction(SIGPIPE, &act, NULL);
}

static void termsig_handler(int signal, siginfo_t *info, void *c)
{
    qemu_system_killed(info->si_signo, info->si_pid);
}

void os_setup_signal_handling(void)
{
    struct sigaction act;

    memset(&act, 0, sizeof(act));
    act.sa_sigaction = termsig_handler;
    act.sa_flags = SA_SIGINFO;
    sigaction(SIGINT,  &act, NULL);
    sigaction(SIGHUP,  &act, NULL);
    sigaction(SIGTERM, &act, NULL);
}

void os_set_proc_name(const char *s)
{
#if defined(PR_SET_NAME)
    char name[16];
    if (!s)
        return;
    pstrcpy(name, sizeof(name), s);
    /* Could rewrite argv[0] too, but that's a bit more complicated.
       This simple way is enough for `top'. */
    if (prctl(PR_SET_NAME, name)) {
        error_report("unable to change process name: %s", strerror(errno));
        exit(1);
    }
#else
    error_report("Change of process name not supported by your OS");
    exit(1);
#endif
}


static bool os_parse_runas_uid_gid(const char *optarg)
{
    unsigned long lv;
    const char *ep;
    uid_t got_uid;
    gid_t got_gid;
    int rc;

    rc = qemu_strtoul(optarg, &ep, 0, &lv);
    got_uid = lv; /* overflow here is ID in C99 */
    if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
        return false;
    }

    rc = qemu_strtoul(ep + 1, 0, 0, &lv);
    got_gid = lv; /* overflow here is ID in C99 */
    if (rc || got_gid != lv || got_gid == (gid_t)-1) {
        return false;
    }

    user_pwd = NULL;
    user_uid = got_uid;
    user_gid = got_gid;
    return true;
}

/*
 * Parse OS specific command line options.
 * return 0 if option handled, -1 otherwise
 */
int os_parse_cmd_args(int index, const char *optarg)
{
    switch (index) {
    case QEMU_OPTION_runas:
        user_pwd = getpwnam(optarg);
        if (user_pwd) {
            user_uid = -1;
            user_gid = -1;
        } else if (!os_parse_runas_uid_gid(optarg)) {
            error_report("User \"%s\" doesn't exist"
                         " (and is not <uid>:<gid>)",
                         optarg);
            exit(1);
        }
        break;
    case QEMU_OPTION_chroot:
        chroot_dir = optarg;
        break;
    case QEMU_OPTION_daemonize:
        daemonize = 1;
        break;
    default:
        return -1;
    }

    return 0;
}

static void change_process_uid(void)
{
    assert((user_uid == (uid_t)-1) || user_pwd == NULL);
    assert((user_uid == (uid_t)-1) ==
           (user_gid == (gid_t)-1));

    if (user_pwd || user_uid != (uid_t)-1) {
        gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
        uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
        if (setgid(intended_gid) < 0) {
            error_report("Failed to setgid(%d)", intended_gid);
            exit(1);
        }
        if (user_pwd) {
            if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
                error_report("Failed to initgroups(\"%s\", %d)",
                        user_pwd->pw_name, user_pwd->pw_gid);
                exit(1);
            }
        } else {
            if (setgroups(1, &user_gid) < 0) {
                error_report("Failed to setgroups(1, [%d])",
                        user_gid);
                exit(1);
            }
        }
        if (setuid(intended_uid) < 0) {
            error_report("Failed to setuid(%d)", intended_uid);
            exit(1);
        }
        if (setuid(0) != -1) {
            error_report("Dropping privileges failed");
            exit(1);
        }
    }
}

static void change_root(void)
{
    if (chroot_dir) {
        if (chroot(chroot_dir) < 0) {
            error_report("chroot failed");
            exit(1);
        }
        if (chdir("/")) {
            error_report("not able to chdir to /: %s", strerror(errno));
            exit(1);
        }
    }

}

void os_daemonize(void)
{
    if (daemonize) {
        pid_t pid;
        int fds[2];

        if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
            exit(1);
        }

        pid = fork();
        if (pid > 0) {
            uint8_t status;
            ssize_t len;

            close(fds[1]);

            do {
                len = read(fds[0], &status, 1);
            } while (len < 0 && errno == EINTR);

            /* only exit successfully if our child actually wrote
             * a one-byte zero to our pipe, upon successful init */
            exit(len == 1 && status == 0 ? 0 : 1);

        } else if (pid < 0) {
            exit(1);
        }

        close(fds[0]);
        daemon_pipe = fds[1];

        setsid();

        pid = fork();
        if (pid > 0) {
            exit(0);
        } else if (pid < 0) {
            exit(1);
        }
        umask(027);

        signal(SIGTSTP, SIG_IGN);
        signal(SIGTTOU, SIG_IGN);
        signal(SIGTTIN, SIG_IGN);
    }
}

void os_setup_post(void)
{
    int fd = 0;

    if (daemonize) {
        if (chdir("/")) {
            error_report("not able to chdir to /: %s", strerror(errno));
            exit(1);
        }
        TFR(fd = qemu_open_old("/dev/null", O_RDWR));
        if (fd == -1) {
            exit(1);
        }
    }

    change_root();
    change_process_uid();

    if (daemonize) {
        uint8_t status = 0;
        ssize_t len;

        dup2(fd, 0);
        dup2(fd, 1);
        /* In case -D is given do not redirect stderr to /dev/null */
        if (!qemu_log_enabled()) {
            dup2(fd, 2);
        }

        close(fd);

        do {        
            len = write(daemon_pipe, &status, 1);
        } while (len < 0 && errno == EINTR);
        if (len != 1) {
            exit(1);
        }
    }
}

void os_set_line_buffering(void)
{
    setvbuf(stdout, NULL, _IOLBF, 0);
}

bool is_daemonized(void)
{
    return daemonize;
}

int os_set_daemonize(bool d)
{
    daemonize = d;
    return 0;
}

int os_mlock(void)
{
#ifdef HAVE_MLOCKALL
    int ret = 0;

    ret = mlockall(MCL_CURRENT | MCL_FUTURE);
    if (ret < 0) {
        error_report("mlockall: %s", strerror(errno));
    }

    return ret;
#else
    return -ENOSYS;
#endif
}