summaryrefslogtreecommitdiffstats
path: root/src/libsystemd/sd-id128/sd-id128.c
blob: fc1107b4e8139d500c68b0e5d26d816408e3064b (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
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include "sd-id128.h"

#include "alloc-util.h"
#include "chase.h"
#include "fd-util.h"
#include "hexdecoct.h"
#include "hmac.h"
#include "id128-util.h"
#include "io-util.h"
#include "keyring-util.h"
#include "macro.h"
#include "missing_syscall.h"
#include "missing_threads.h"
#include "path-util.h"
#include "random-util.h"
#include "stat-util.h"
#include "user-util.h"

_public_ char *sd_id128_to_string(sd_id128_t id, char s[_SD_ARRAY_STATIC SD_ID128_STRING_MAX]) {
        size_t k = 0;

        assert_return(s, NULL);

        for (size_t n = 0; n < sizeof(sd_id128_t); n++) {
                s[k++] = hexchar(id.bytes[n] >> 4);
                s[k++] = hexchar(id.bytes[n] & 0xF);
        }

        assert(k == SD_ID128_STRING_MAX - 1);
        s[k] = 0;

        return s;
}

_public_ char *sd_id128_to_uuid_string(sd_id128_t id, char s[_SD_ARRAY_STATIC SD_ID128_UUID_STRING_MAX]) {
        size_t k = 0;

        assert_return(s, NULL);

        /* Similar to sd_id128_to_string() but formats the result as UUID instead of plain hex chars */

        for (size_t n = 0; n < sizeof(sd_id128_t); n++) {

                if (IN_SET(n, 4, 6, 8, 10))
                        s[k++] = '-';

                s[k++] = hexchar(id.bytes[n] >> 4);
                s[k++] = hexchar(id.bytes[n] & 0xF);
        }

        assert(k == SD_ID128_UUID_STRING_MAX - 1);
        s[k] = 0;

        return s;
}

_public_ int sd_id128_from_string(const char *s, sd_id128_t *ret) {
        size_t n, i;
        sd_id128_t t;
        bool is_guid = false;

        assert_return(s, -EINVAL);

        for (n = 0, i = 0; n < sizeof(sd_id128_t);) {
                int a, b;

                if (s[i] == '-') {
                        /* Is this a GUID? Then be nice, and skip over
                         * the dashes */

                        if (i == 8)
                                is_guid = true;
                        else if (IN_SET(i, 13, 18, 23)) {
                                if (!is_guid)
                                        return -EINVAL;
                        } else
                                return -EINVAL;

                        i++;
                        continue;
                }

                a = unhexchar(s[i++]);
                if (a < 0)
                        return -EINVAL;

                b = unhexchar(s[i++]);
                if (b < 0)
                        return -EINVAL;

                t.bytes[n++] = (a << 4) | b;
        }

        if (i != (is_guid ? SD_ID128_UUID_STRING_MAX : SD_ID128_STRING_MAX) - 1)
                return -EINVAL;

        if (s[i] != 0)
                return -EINVAL;

        if (ret)
                *ret = t;
        return 0;
}

_public_ int sd_id128_string_equal(const char *s, sd_id128_t id) {
        sd_id128_t parsed;
        int r;

        if (!s)
                return false;

        /* Checks if the specified string matches a valid string representation of the specified 128 bit ID/uuid */

        r = sd_id128_from_string(s, &parsed);
        if (r < 0)
                return r;

        return sd_id128_equal(parsed, id);
}

_public_ int sd_id128_get_machine(sd_id128_t *ret) {
        static thread_local sd_id128_t saved_machine_id = {};
        int r;

        if (sd_id128_is_null(saved_machine_id)) {
                r = id128_read("/etc/machine-id", ID128_FORMAT_PLAIN | ID128_REFUSE_NULL, &saved_machine_id);
                if (r < 0)
                        return r;
        }

        if (ret)
                *ret = saved_machine_id;
        return 0;
}

int id128_get_machine_at(int rfd, sd_id128_t *ret) {
        _cleanup_close_ int fd = -EBADF;
        int r;

        assert(rfd >= 0 || rfd == AT_FDCWD);

        r = dir_fd_is_root_or_cwd(rfd);
        if (r < 0)
                return r;
        if (r > 0)
                return sd_id128_get_machine(ret);

        fd = chase_and_openat(rfd, "/etc/machine-id", CHASE_AT_RESOLVE_IN_ROOT, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
        if (fd < 0)
                return fd;

        return id128_read_fd(fd, ID128_FORMAT_PLAIN | ID128_REFUSE_NULL, ret);
}

int id128_get_machine(const char *root, sd_id128_t *ret) {
        _cleanup_close_ int fd = -EBADF;

        if (empty_or_root(root))
                return sd_id128_get_machine(ret);

        fd = chase_and_open("/etc/machine-id", root, CHASE_PREFIX_ROOT, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
        if (fd < 0)
                return fd;

        return id128_read_fd(fd, ID128_FORMAT_PLAIN | ID128_REFUSE_NULL, ret);
}

int id128_get_boot(sd_id128_t *ret) {
        int r;

        assert(ret);

        r = id128_read("/proc/sys/kernel/random/boot_id", ID128_FORMAT_UUID | ID128_REFUSE_NULL, ret);
        if (r == -ENOENT && proc_mounted() == 0)
                return -ENOSYS;

        return r;
}

_public_ int sd_id128_get_boot(sd_id128_t *ret) {
        static thread_local sd_id128_t saved_boot_id = {};
        int r;

        if (sd_id128_is_null(saved_boot_id)) {
                r = id128_get_boot(&saved_boot_id);
                if (r < 0)
                        return r;
        }

        if (ret)
                *ret = saved_boot_id;
        return 0;
}

static int get_invocation_from_keyring(sd_id128_t *ret) {
        _cleanup_free_ char *description = NULL;
        char *d, *p, *g, *u, *e;
        unsigned long perms;
        key_serial_t key;
        uid_t uid;
        gid_t gid;
        int r, c;

#define MAX_PERMS ((unsigned long) (KEY_POS_VIEW|KEY_POS_READ|KEY_POS_SEARCH| \
                                    KEY_USR_VIEW|KEY_USR_READ|KEY_USR_SEARCH))

        assert(ret);

        key = request_key("user", "invocation_id", NULL, 0);
        if (key == -1) {
                /* Keyring support not available? No invocation key stored? */
                if (IN_SET(errno, ENOSYS, ENOKEY))
                        return -ENXIO;

                return -errno;
        }

        r = keyring_describe(key, &description);
        if (r < 0)
                return r;

        /* Chop off the final description string */
        d = strrchr(description, ';');
        if (!d)
                return -EUCLEAN;
        *d = 0;

        /* Look for the permissions */
        p = strrchr(description, ';');
        if (!p)
                return -EUCLEAN;

        errno = 0;
        perms = strtoul(p + 1, &e, 16);
        if (errno > 0)
                return -errno;
        if (e == p + 1) /* Read at least one character */
                return -EUCLEAN;
        if (e != d) /* Must reached the end */
                return -EUCLEAN;

        if ((perms & ~MAX_PERMS) != 0)
                return -EPERM;

        *p = 0;

        /* Look for the group ID */
        g = strrchr(description, ';');
        if (!g)
                return -EUCLEAN;
        r = parse_gid(g + 1, &gid);
        if (r < 0)
                return r;
        if (gid != 0)
                return -EPERM;
        *g = 0;

        /* Look for the user ID */
        u = strrchr(description, ';');
        if (!u)
                return -EUCLEAN;
        r = parse_uid(u + 1, &uid);
        if (r < 0)
                return r;
        if (uid != 0)
                return -EPERM;

        c = keyctl(KEYCTL_READ, key, (unsigned long) ret, sizeof(sd_id128_t), 0);
        if (c < 0)
                return -errno;
        if (c != sizeof(sd_id128_t))
                return -EUCLEAN;

        return 0;
}

static int get_invocation_from_environment(sd_id128_t *ret) {
        const char *e;
        int r;

        assert(ret);

        e = secure_getenv("INVOCATION_ID");
        if (!e)
                return -ENXIO;

        r = sd_id128_from_string(e, ret);
        return r == -EINVAL ? -EUCLEAN : r;
}

_public_ int sd_id128_get_invocation(sd_id128_t *ret) {
        static thread_local sd_id128_t saved_invocation_id = {};
        int r;

        if (sd_id128_is_null(saved_invocation_id)) {
                /* We first check the environment. The environment variable is primarily relevant for user
                 * services, and sufficiently safe as long as no privilege boundary is involved. */
                r = get_invocation_from_environment(&saved_invocation_id);
                if (r == -ENXIO)
                        /* The kernel keyring is relevant for system services (as for user services we don't
                         * store the invocation ID in the keyring, as there'd be no trust benefit in that). */
                        r = get_invocation_from_keyring(&saved_invocation_id);
                if (r < 0)
                        return r;

                if (sd_id128_is_null(saved_invocation_id))
                        return -ENOMEDIUM;
        }

        if (ret)
                *ret = saved_invocation_id;
        return 0;
}

_public_ int sd_id128_randomize(sd_id128_t *ret) {
        sd_id128_t t;

        assert_return(ret, -EINVAL);

        random_bytes(&t, sizeof(t));

        /* Turn this into a valid v4 UUID, to be nice. Note that we
         * only guarantee this for newly generated UUIDs, not for
         * pre-existing ones. */

        *ret = id128_make_v4_uuid(t);
        return 0;
}

_public_ int sd_id128_get_app_specific(sd_id128_t base, sd_id128_t app_id, sd_id128_t *ret) {
        assert_cc(sizeof(sd_id128_t) < SHA256_DIGEST_SIZE); /* Check that we don't need to pad with zeros. */
        union {
                uint8_t hmac[SHA256_DIGEST_SIZE];
                sd_id128_t result;
        } buf;

        assert_return(ret, -EINVAL);
        assert_return(!sd_id128_is_null(app_id), -ENXIO);

        hmac_sha256(&base, sizeof(base), &app_id, sizeof(app_id), buf.hmac);

        /* Take only the first half. */
        *ret = id128_make_v4_uuid(buf.result);
        return 0;
}

_public_ int sd_id128_get_machine_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
        sd_id128_t id;
        int r;

        assert_return(ret, -EINVAL);

        r = sd_id128_get_machine(&id);
        if (r < 0)
                return r;

        return sd_id128_get_app_specific(id, app_id, ret);
}

_public_ int sd_id128_get_boot_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
        sd_id128_t id;
        int r;

        assert_return(ret, -EINVAL);

        r = sd_id128_get_boot(&id);
        if (r < 0)
                return r;

        return sd_id128_get_app_specific(id, app_id, ret);
}

_public_ int sd_id128_get_invocation_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
        sd_id128_t id;
        int r;

        assert_return(ret, -EINVAL);

        r = sd_id128_get_invocation(&id);
        if (r < 0)
                return r;

        return sd_id128_get_app_specific(id, app_id, ret);
}