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2f893044 LP |
1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
2 | ||
3 | #include "fd-util.h" | |
4 | #include "fileio.h" | |
5 | #include "format-util.h" | |
6 | #include "fs-util.h" | |
7 | #include "nspawn-bind-user.h" | |
8 | #include "nspawn.h" | |
9 | #include "path-util.h" | |
10 | #include "user-util.h" | |
11 | #include "userdb.h" | |
12 | ||
13 | #define MAP_UID_START 60514 | |
14 | #define MAP_UID_END 60577 | |
15 | ||
16 | static int check_etc_passwd_collisions( | |
17 | const char *directory, | |
18 | const char *name, | |
19 | uid_t uid) { | |
20 | ||
21 | _cleanup_fclose_ FILE *f = NULL; | |
22 | int r; | |
23 | ||
24 | assert(directory); | |
25 | assert(name || uid_is_valid(uid)); | |
26 | ||
27 | r = chase_symlinks_and_fopen_unlocked("/etc/passwd", directory, CHASE_PREFIX_ROOT, "re", &f, NULL); | |
28 | if (r == -ENOENT) | |
29 | return 0; /* no user database? then no user, hence no collision */ | |
30 | if (r < 0) | |
31 | return log_error_errno(r, "Failed to open /etc/passwd of container: %m"); | |
32 | ||
33 | for (;;) { | |
34 | struct passwd *pw; | |
35 | ||
36 | r = fgetpwent_sane(f, &pw); | |
37 | if (r < 0) | |
38 | return log_error_errno(r, "Failed to iterate through /etc/passwd of container: %m"); | |
39 | if (r == 0) /* EOF */ | |
40 | return 0; /* no collision */ | |
41 | ||
42 | if (name && streq_ptr(pw->pw_name, name)) | |
43 | return 1; /* name collision */ | |
44 | if (uid_is_valid(uid) && pw->pw_uid == uid) | |
45 | return 1; /* UID collision */ | |
46 | } | |
47 | } | |
48 | ||
49 | static int check_etc_group_collisions( | |
50 | const char *directory, | |
51 | const char *name, | |
52 | gid_t gid) { | |
53 | ||
54 | _cleanup_fclose_ FILE *f = NULL; | |
55 | int r; | |
56 | ||
57 | assert(directory); | |
58 | assert(name || gid_is_valid(gid)); | |
59 | ||
60 | r = chase_symlinks_and_fopen_unlocked("/etc/group", directory, CHASE_PREFIX_ROOT, "re", &f, NULL); | |
61 | if (r == -ENOENT) | |
62 | return 0; /* no group database? then no group, hence no collision */ | |
63 | if (r < 0) | |
64 | return log_error_errno(r, "Failed to open /etc/group of container: %m"); | |
65 | ||
66 | for (;;) { | |
67 | struct group *gr; | |
68 | ||
69 | r = fgetgrent_sane(f, &gr); | |
70 | if (r < 0) | |
71 | return log_error_errno(r, "Failed to iterate through /etc/group of container: %m"); | |
72 | if (r == 0) | |
73 | return 0; /* no collision */ | |
74 | ||
75 | if (name && streq_ptr(gr->gr_name, name)) | |
76 | return 1; /* name collision */ | |
77 | if (gid_is_valid(gid) && gr->gr_gid == gid) | |
78 | return 1; /* gid collision */ | |
79 | } | |
80 | } | |
81 | ||
82 | static int convert_user( | |
83 | const char *directory, | |
84 | UserRecord *u, | |
85 | GroupRecord *g, | |
86 | uid_t allocate_uid, | |
87 | UserRecord **ret_converted_user, | |
88 | GroupRecord **ret_converted_group) { | |
89 | ||
90 | _cleanup_(group_record_unrefp) GroupRecord *converted_group = NULL; | |
91 | _cleanup_(user_record_unrefp) UserRecord *converted_user = NULL; | |
92 | _cleanup_free_ char *h = NULL; | |
93 | JsonVariant *p, *hp = NULL; | |
94 | int r; | |
95 | ||
96 | assert(u); | |
97 | assert(g); | |
98 | assert(u->gid == g->gid); | |
99 | ||
100 | r = check_etc_passwd_collisions(directory, u->user_name, UID_INVALID); | |
101 | if (r < 0) | |
102 | return r; | |
103 | if (r > 0) | |
104 | return log_error_errno(SYNTHETIC_ERRNO(EBUSY), | |
105 | "Sorry, the user '%s' already exists in the container.", u->user_name); | |
106 | ||
107 | r = check_etc_group_collisions(directory, g->group_name, GID_INVALID); | |
108 | if (r < 0) | |
109 | return r; | |
110 | if (r > 0) | |
111 | return log_error_errno(SYNTHETIC_ERRNO(EBUSY), | |
112 | "Sorry, the group '%s' already exists in the container.", g->group_name); | |
113 | ||
114 | h = path_join("/run/host/home/", u->user_name); | |
115 | if (!h) | |
116 | return log_oom(); | |
117 | ||
118 | /* Acquire the source hashed password array as-is, so that it retains the JSON_VARIANT_SENSITIVE flag */ | |
119 | p = json_variant_by_key(u->json, "privileged"); | |
120 | if (p) | |
121 | hp = json_variant_by_key(p, "hashedPassword"); | |
122 | ||
123 | r = user_record_build( | |
124 | &converted_user, | |
125 | JSON_BUILD_OBJECT( | |
126 | JSON_BUILD_PAIR("userName", JSON_BUILD_STRING(u->user_name)), | |
127 | JSON_BUILD_PAIR("uid", JSON_BUILD_UNSIGNED(allocate_uid)), | |
128 | JSON_BUILD_PAIR("gid", JSON_BUILD_UNSIGNED(allocate_uid)), | |
129 | JSON_BUILD_PAIR_CONDITION(u->disposition >= 0, "disposition", JSON_BUILD_STRING(user_disposition_to_string(u->disposition))), | |
130 | JSON_BUILD_PAIR("homeDirectory", JSON_BUILD_STRING(h)), | |
131 | JSON_BUILD_PAIR("service", JSON_BUILD_STRING("io.systemd.NSpawn")), | |
132 | JSON_BUILD_PAIR_CONDITION(!strv_isempty(u->hashed_password), "privileged", JSON_BUILD_OBJECT( | |
133 | JSON_BUILD_PAIR("hashedPassword", JSON_BUILD_VARIANT(hp)))))); | |
134 | if (r < 0) | |
135 | return log_error_errno(r, "Failed to build container user record: %m"); | |
136 | ||
137 | r = group_record_build( | |
138 | &converted_group, | |
139 | JSON_BUILD_OBJECT( | |
140 | JSON_BUILD_PAIR("groupName", JSON_BUILD_STRING(g->group_name)), | |
141 | JSON_BUILD_PAIR("gid", JSON_BUILD_UNSIGNED(allocate_uid)), | |
142 | JSON_BUILD_PAIR_CONDITION(g->disposition >= 0, "disposition", JSON_BUILD_STRING(user_disposition_to_string(g->disposition))), | |
143 | JSON_BUILD_PAIR("service", JSON_BUILD_STRING("io.systemd.NSpawn")))); | |
144 | if (r < 0) | |
145 | return log_error_errno(r, "Failed to build container group record: %m"); | |
146 | ||
147 | *ret_converted_user = TAKE_PTR(converted_user); | |
148 | *ret_converted_group = TAKE_PTR(converted_group); | |
149 | ||
150 | return 0; | |
151 | } | |
152 | ||
153 | static int find_free_uid(const char *directory, uid_t max_uid, uid_t *current_uid) { | |
154 | int r; | |
155 | ||
156 | assert(directory); | |
157 | assert(current_uid); | |
158 | ||
159 | for (;; (*current_uid) ++) { | |
160 | if (*current_uid > MAP_UID_END || *current_uid > max_uid) | |
161 | return log_error_errno( | |
162 | SYNTHETIC_ERRNO(EBUSY), | |
163 | "No suitable available UID in range " UID_FMT "…" UID_FMT " in container detected, can't map user.", | |
164 | MAP_UID_START, MAP_UID_END); | |
165 | ||
166 | r = check_etc_passwd_collisions(directory, NULL, *current_uid); | |
167 | if (r < 0) | |
168 | return r; | |
169 | if (r > 0) /* already used */ | |
170 | continue; | |
171 | ||
172 | /* We want to use the UID also as GID, hence check for it in /etc/group too */ | |
173 | r = check_etc_group_collisions(directory, NULL, (gid_t) *current_uid); | |
174 | if (r < 0) | |
175 | return r; | |
176 | if (r == 0) /* free! yay! */ | |
177 | return 0; | |
178 | } | |
179 | } | |
180 | ||
181 | BindUserContext* bind_user_context_free(BindUserContext *c) { | |
182 | if (!c) | |
183 | return NULL; | |
184 | ||
185 | assert(c->n_data == 0 || c->data); | |
186 | ||
187 | for (size_t i = 0; i < c->n_data; i++) { | |
188 | user_record_unref(c->data[i].host_user); | |
189 | group_record_unref(c->data[i].host_group); | |
190 | user_record_unref(c->data[i].payload_user); | |
191 | group_record_unref(c->data[i].payload_group); | |
192 | } | |
193 | ||
194 | return mfree(c); | |
195 | } | |
196 | ||
197 | int bind_user_prepare( | |
198 | const char *directory, | |
199 | char **bind_user, | |
200 | uid_t uid_shift, | |
201 | uid_t uid_range, | |
202 | CustomMount **custom_mounts, | |
203 | size_t *n_custom_mounts, | |
204 | BindUserContext **ret) { | |
205 | ||
206 | _cleanup_(bind_user_context_freep) BindUserContext *c = NULL; | |
207 | uid_t current_uid = MAP_UID_START; | |
2f893044 LP |
208 | char **n; |
209 | int r; | |
210 | ||
211 | assert(custom_mounts); | |
212 | assert(n_custom_mounts); | |
213 | assert(ret); | |
214 | ||
215 | /* This resolves the users specified in 'bind_user', generates a minimalized JSON user + group record | |
216 | * for it to stick in the container, allocates a UID/GID for it, and updates the custom mount table, | |
217 | * to include an appropriate bind mount mapping. | |
218 | * | |
219 | * This extends the passed custom_mounts/n_custom_mounts with the home directories, and allocates a | |
220 | * new BindUserContext for the user records */ | |
221 | ||
222 | if (strv_isempty(bind_user)) { | |
223 | *ret = NULL; | |
224 | return 0; | |
225 | } | |
226 | ||
227 | c = new0(BindUserContext, 1); | |
228 | if (!c) | |
229 | return log_oom(); | |
230 | ||
231 | STRV_FOREACH(n, bind_user) { | |
232 | _cleanup_(user_record_unrefp) UserRecord *u = NULL, *cu = NULL; | |
233 | _cleanup_(group_record_unrefp) GroupRecord *g = NULL, *cg = NULL; | |
234 | _cleanup_free_ char *sm = NULL, *sd = NULL; | |
235 | CustomMount *cm; | |
236 | ||
237 | r = userdb_by_name(*n, USERDB_DONT_SYNTHESIZE, &u); | |
238 | if (r < 0) | |
239 | return log_error_errno(r, "Failed to resolve user '%s': %m", *n); | |
240 | ||
241 | /* For now, let's refuse mapping the root/nobody users explicitly. The records we generate | |
242 | * are strictly additive, nss-systemd is typically placed last in /etc/nsswitch.conf. Thus | |
243 | * even if we wanted, we couldn't override the root or nobody user records. Note we also | |
244 | * check for name conflicts in /etc/passwd + /etc/group later on, which would usually filter | |
245 | * out root/nobody too, hence these checks might appear redundant — but they actually are | |
246 | * not, as we want to support environments where /etc/passwd and /etc/group are non-existent, | |
247 | * and the user/group databases fully synthesized at runtime. Moreover, the name of the | |
248 | * user/group name of the "nobody" account differs between distros, hence a check by numeric | |
249 | * UID is safer. */ | |
250 | if (u->uid == 0 || streq(u->user_name, "root")) | |
251 | return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Mapping 'root' user not supported, sorry."); | |
252 | if (u->uid == UID_NOBODY || STR_IN_SET(u->user_name, NOBODY_USER_NAME, "nobody")) | |
253 | return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Mapping 'nobody' user not supported, sorry."); | |
254 | ||
255 | if (u->uid >= uid_shift && u->uid < uid_shift + uid_range) | |
256 | return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "UID of user '%s' to map is already in container UID range, refusing.", u->user_name); | |
257 | ||
258 | r = groupdb_by_gid(u->gid, USERDB_DONT_SYNTHESIZE, &g); | |
259 | if (r < 0) | |
260 | return log_error_errno(r, "Failed to resolve group of user '%s': %m", u->user_name); | |
261 | ||
262 | if (g->gid >= uid_shift && g->gid < uid_shift + uid_range) | |
263 | return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "GID of group '%s' to map is already in container GID range, refusing.", g->group_name); | |
264 | ||
265 | /* We want to synthesize exactly one user + group from the host into the container. This only | |
266 | * makes sense if the user on the host has its own private group. We can't reasonably check | |
267 | * this, so we just check of the name of user and group match. | |
268 | * | |
269 | * One of these days we might want to support users in a shared/common group too, but it's | |
270 | * not clear to me how this would have to be mapped, precisely given that the common group | |
271 | * probably already exists in the container. */ | |
272 | if (!streq(u->user_name, g->group_name)) | |
273 | return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), | |
274 | "Sorry, mapping users without private groups is currently not supported."); | |
275 | ||
276 | r = find_free_uid(directory, uid_range, ¤t_uid); | |
277 | if (r < 0) | |
278 | return r; | |
279 | ||
280 | r = convert_user(directory, u, g, current_uid, &cu, &cg); | |
281 | if (r < 0) | |
282 | return r; | |
283 | ||
354dadb3 | 284 | if (!GREEDY_REALLOC(c->data, c->n_data + 1)) |
2f893044 LP |
285 | return log_oom(); |
286 | ||
287 | sm = strdup(u->home_directory); | |
288 | if (!sm) | |
289 | return log_oom(); | |
290 | ||
291 | sd = strdup(cu->home_directory); | |
292 | if (!sd) | |
293 | return log_oom(); | |
294 | ||
295 | cm = reallocarray(*custom_mounts, sizeof(CustomMount), *n_custom_mounts + 1); | |
296 | if (!cm) | |
297 | return log_oom(); | |
298 | ||
299 | *custom_mounts = cm; | |
300 | ||
301 | (*custom_mounts)[(*n_custom_mounts)++] = (CustomMount) { | |
302 | .type = CUSTOM_MOUNT_BIND, | |
303 | .source = TAKE_PTR(sm), | |
304 | .destination = TAKE_PTR(sd), | |
305 | }; | |
306 | ||
307 | c->data[c->n_data++] = (BindUserData) { | |
308 | .host_user = TAKE_PTR(u), | |
309 | .host_group = TAKE_PTR(g), | |
310 | .payload_user = TAKE_PTR(cu), | |
311 | .payload_group = TAKE_PTR(cg), | |
312 | }; | |
313 | ||
314 | current_uid++; | |
315 | } | |
316 | ||
317 | *ret = TAKE_PTR(c); | |
318 | return 1; | |
319 | } | |
320 | ||
321 | static int write_and_symlink( | |
322 | const char *root, | |
323 | JsonVariant *v, | |
324 | const char *name, | |
325 | uid_t uid, | |
326 | const char *suffix, | |
327 | WriteStringFileFlags extra_flags) { | |
328 | ||
329 | _cleanup_free_ char *j = NULL, *f = NULL, *p = NULL, *q = NULL; | |
330 | int r; | |
331 | ||
332 | assert(root); | |
333 | assert(v); | |
334 | assert(name); | |
335 | assert(uid_is_valid(uid)); | |
336 | assert(suffix); | |
337 | ||
338 | r = json_variant_format(v, JSON_FORMAT_NEWLINE, &j); | |
339 | if (r < 0) | |
340 | return log_error_errno(r, "Failed to format user record JSON: %m"); | |
341 | ||
342 | f = strjoin(name, suffix); | |
343 | if (!f) | |
344 | return log_oom(); | |
345 | ||
346 | p = path_join(root, "/run/host/userdb/", f); | |
347 | if (!p) | |
348 | return log_oom(); | |
349 | ||
350 | if (asprintf(&q, "%s/run/host/userdb/" UID_FMT "%s", root, uid, suffix) < 0) | |
351 | return log_oom(); | |
352 | ||
353 | if (symlink(f, q) < 0) | |
354 | return log_error_errno(errno, "Failed to create symlink '%s': %m", q); | |
355 | ||
356 | r = userns_lchown(q, 0, 0); | |
357 | if (r < 0) | |
358 | return log_error_errno(r, "Failed to adjust access mode of '%s': %m", q); | |
359 | ||
360 | r = write_string_file(p, j, WRITE_STRING_FILE_CREATE|extra_flags); | |
361 | if (r < 0) | |
362 | return log_error_errno(r, "Failed to write %s: %m", p); | |
363 | ||
364 | r = userns_lchown(p, 0, 0); | |
365 | if (r < 0) | |
366 | return log_error_errno(r, "Failed to adjust access mode of '%s': %m", p); | |
367 | ||
368 | return 0; | |
369 | } | |
370 | ||
371 | int bind_user_setup( | |
372 | const BindUserContext *c, | |
373 | const char *root) { | |
374 | ||
375 | static const UserRecordLoadFlags strip_flags = /* Removes privileged info */ | |
376 | USER_RECORD_REQUIRE_REGULAR| | |
377 | USER_RECORD_STRIP_PRIVILEGED| | |
378 | USER_RECORD_ALLOW_PER_MACHINE| | |
379 | USER_RECORD_ALLOW_BINDING| | |
380 | USER_RECORD_ALLOW_SIGNATURE; | |
381 | static const UserRecordLoadFlags shadow_flags = /* Extracts privileged info */ | |
382 | USER_RECORD_STRIP_REGULAR| | |
383 | USER_RECORD_ALLOW_PRIVILEGED| | |
384 | USER_RECORD_STRIP_PER_MACHINE| | |
385 | USER_RECORD_STRIP_BINDING| | |
386 | USER_RECORD_STRIP_SIGNATURE| | |
387 | USER_RECORD_EMPTY_OK; | |
388 | int r; | |
389 | ||
390 | assert(root); | |
391 | ||
392 | if (!c || c->n_data == 0) | |
393 | return 0; | |
394 | ||
395 | r = userns_mkdir(root, "/run/host", 0755, 0, 0); | |
396 | if (r < 0) | |
397 | return log_error_errno(r, "Failed to create /run/host: %m"); | |
398 | ||
399 | r = userns_mkdir(root, "/run/host/home", 0755, 0, 0); | |
400 | if (r < 0) | |
401 | return log_error_errno(r, "Failed to create /run/host/userdb: %m"); | |
402 | ||
403 | r = userns_mkdir(root, "/run/host/userdb", 0755, 0, 0); | |
404 | if (r < 0) | |
405 | return log_error_errno(r, "Failed to create /run/host/userdb: %m"); | |
406 | ||
407 | for (size_t i = 0; i < c->n_data; i++) { | |
408 | _cleanup_(group_record_unrefp) GroupRecord *stripped_group = NULL, *shadow_group = NULL; | |
409 | _cleanup_(user_record_unrefp) UserRecord *stripped_user = NULL, *shadow_user = NULL; | |
410 | const BindUserData *d = c->data + i; | |
411 | ||
412 | /* First, write shadow (i.e. privileged) data for group record */ | |
413 | r = group_record_clone(d->payload_group, shadow_flags, &shadow_group); | |
414 | if (r < 0) | |
415 | return log_error_errno(r, "Failed to extract privileged information from group record: %m"); | |
416 | ||
417 | if (!json_variant_is_blank_object(shadow_group->json)) { | |
418 | r = write_and_symlink( | |
419 | root, | |
420 | shadow_group->json, | |
421 | d->payload_group->group_name, | |
422 | d->payload_group->gid, | |
423 | ".group-privileged", | |
424 | WRITE_STRING_FILE_MODE_0600); | |
425 | if (r < 0) | |
426 | return r; | |
427 | } | |
428 | ||
429 | /* Second, write main part of group record. */ | |
430 | r = group_record_clone(d->payload_group, strip_flags, &stripped_group); | |
431 | if (r < 0) | |
432 | return log_error_errno(r, "Failed to strip privileged information from group record: %m"); | |
433 | ||
434 | r = write_and_symlink( | |
435 | root, | |
436 | stripped_group->json, | |
437 | d->payload_group->group_name, | |
438 | d->payload_group->gid, | |
439 | ".group", | |
440 | 0); | |
441 | if (r < 0) | |
442 | return r; | |
443 | ||
444 | /* Third, write out user shadow data. i.e. extract privileged info from user record */ | |
445 | r = user_record_clone(d->payload_user, shadow_flags, &shadow_user); | |
446 | if (r < 0) | |
447 | return log_error_errno(r, "Failed to extract privileged information from user record: %m"); | |
448 | ||
449 | if (!json_variant_is_blank_object(shadow_user->json)) { | |
450 | r = write_and_symlink( | |
451 | root, | |
452 | shadow_user->json, | |
453 | d->payload_user->user_name, | |
454 | d->payload_user->uid, | |
455 | ".user-privileged", | |
456 | WRITE_STRING_FILE_MODE_0600); | |
457 | if (r < 0) | |
458 | return r; | |
459 | } | |
460 | ||
461 | /* Finally write out the main part of the user record */ | |
462 | r = user_record_clone(d->payload_user, strip_flags, &stripped_user); | |
463 | if (r < 0) | |
464 | return log_error_errno(r, "Failed to strip privileged information from user record: %m"); | |
465 | ||
466 | r = write_and_symlink( | |
467 | root, | |
468 | stripped_user->json, | |
469 | d->payload_user->user_name, | |
470 | d->payload_user->uid, | |
471 | ".user", | |
472 | 0); | |
473 | if (r < 0) | |
474 | return r; | |
475 | } | |
476 | ||
477 | return 1; | |
478 | } |