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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
1988a9d1 DM |
2 | |
3 | #include <arpa/inet.h> | |
4 | #include <assert.h> | |
5 | #include <errno.h> | |
6 | #include <fcntl.h> | |
01234e1f | 7 | #include <linux/bpf_insn.h> |
1988a9d1 DM |
8 | #include <net/ethernet.h> |
9 | #include <net/if.h> | |
10 | #include <netinet/ip.h> | |
11 | #include <netinet/ip6.h> | |
12 | #include <stddef.h> | |
13 | #include <stdio.h> | |
14 | #include <stdlib.h> | |
15 | #include <string.h> | |
16 | #include <unistd.h> | |
17 | ||
18 | #include "alloc-util.h" | |
19 | #include "bpf-firewall.h" | |
20 | #include "bpf-program.h" | |
21 | #include "fd-util.h" | |
22 | #include "ip-address-access.h" | |
0a970718 | 23 | #include "memory-util.h" |
e93672ee | 24 | #include "missing_syscall.h" |
1988a9d1 | 25 | #include "unit.h" |
f140ed02 | 26 | #include "virt.h" |
1988a9d1 DM |
27 | |
28 | enum { | |
29 | MAP_KEY_PACKETS, | |
30 | MAP_KEY_BYTES, | |
31 | }; | |
32 | ||
33 | enum { | |
34 | ACCESS_ALLOWED = 1, | |
35 | ACCESS_DENIED = 2, | |
36 | }; | |
37 | ||
38 | /* Compile instructions for one list of addresses, one direction and one specific verdict on matches. */ | |
39 | ||
40 | static int add_lookup_instructions( | |
41 | BPFProgram *p, | |
42 | int map_fd, | |
43 | int protocol, | |
44 | bool is_ingress, | |
45 | int verdict) { | |
46 | ||
47 | int r, addr_offset, addr_size; | |
48 | ||
49 | assert(p); | |
50 | assert(map_fd >= 0); | |
51 | ||
52 | switch (protocol) { | |
53 | ||
54 | case ETH_P_IP: | |
55 | addr_size = sizeof(uint32_t); | |
56 | addr_offset = is_ingress ? | |
57 | offsetof(struct iphdr, saddr) : | |
58 | offsetof(struct iphdr, daddr); | |
59 | break; | |
60 | ||
61 | case ETH_P_IPV6: | |
62 | addr_size = 4 * sizeof(uint32_t); | |
63 | addr_offset = is_ingress ? | |
64 | offsetof(struct ip6_hdr, ip6_src.s6_addr) : | |
65 | offsetof(struct ip6_hdr, ip6_dst.s6_addr); | |
66 | break; | |
67 | ||
68 | default: | |
69 | return -EAFNOSUPPORT; | |
70 | } | |
71 | ||
72 | do { | |
73 | /* Compare IPv4 with one word instruction (32bit) */ | |
74 | struct bpf_insn insn[] = { | |
75 | /* If skb->protocol != ETH_P_IP, skip this whole block. The offset will be set later. */ | |
76 | BPF_JMP_IMM(BPF_JNE, BPF_REG_7, htobe16(protocol), 0), | |
77 | ||
78 | /* | |
79 | * Call into BPF_FUNC_skb_load_bytes to load the dst/src IP address | |
80 | * | |
81 | * R1: Pointer to the skb | |
82 | * R2: Data offset | |
83 | * R3: Destination buffer on the stack (r10 - 4) | |
84 | * R4: Number of bytes to read (4) | |
85 | */ | |
86 | ||
87 | BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), | |
88 | BPF_MOV32_IMM(BPF_REG_2, addr_offset), | |
89 | ||
90 | BPF_MOV64_REG(BPF_REG_3, BPF_REG_10), | |
91 | BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -addr_size), | |
92 | ||
93 | BPF_MOV32_IMM(BPF_REG_4, addr_size), | |
94 | BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_skb_load_bytes), | |
95 | ||
96 | /* | |
97 | * Call into BPF_FUNC_map_lookup_elem to see if the address matches any entry in the | |
98 | * LPM trie map. For this to work, the prefixlen field of 'struct bpf_lpm_trie_key' | |
99 | * has to be set to the maximum possible value. | |
100 | * | |
101 | * On success, the looked up value is stored in R0. For this application, the actual | |
102 | * value doesn't matter, however; we just set the bit in @verdict in R8 if we found any | |
103 | * matching value. | |
104 | */ | |
105 | ||
106 | BPF_LD_MAP_FD(BPF_REG_1, map_fd), | |
107 | BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), | |
108 | BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -addr_size - sizeof(uint32_t)), | |
109 | BPF_ST_MEM(BPF_W, BPF_REG_2, 0, addr_size * 8), | |
110 | ||
111 | BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), | |
112 | BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1), | |
113 | BPF_ALU32_IMM(BPF_OR, BPF_REG_8, verdict), | |
114 | }; | |
115 | ||
116 | /* Jump label fixup */ | |
117 | insn[0].off = ELEMENTSOF(insn) - 1; | |
118 | ||
119 | r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn)); | |
120 | if (r < 0) | |
121 | return r; | |
122 | ||
123 | } while (false); | |
124 | ||
125 | return 0; | |
126 | } | |
127 | ||
128 | static int bpf_firewall_compile_bpf( | |
129 | Unit *u, | |
130 | bool is_ingress, | |
131 | BPFProgram **ret) { | |
132 | ||
133 | struct bpf_insn pre_insn[] = { | |
134 | /* | |
135 | * When the eBPF program is entered, R1 contains the address of the skb. | |
136 | * However, R1-R5 are scratch registers that are not preserved when calling | |
137 | * into kernel functions, so we need to save anything that's supposed to | |
138 | * stay around to R6-R9. Save the skb to R6. | |
139 | */ | |
140 | BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), | |
141 | ||
142 | /* | |
143 | * Although we cannot access the skb data directly from eBPF programs used in this | |
144 | * scenario, the kernel has prepared some fields for us to access through struct __sk_buff. | |
145 | * Load the protocol (IPv4, IPv6) used by the packet in flight once and cache it in R7 | |
146 | * for later use. | |
147 | */ | |
148 | BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6, offsetof(struct __sk_buff, protocol)), | |
149 | ||
150 | /* | |
151 | * R8 is used to keep track of whether any address check has explicitly allowed or denied the packet | |
152 | * through ACCESS_DENIED or ACCESS_ALLOWED bits. Reset them both to 0 in the beginning. | |
153 | */ | |
154 | BPF_MOV32_IMM(BPF_REG_8, 0), | |
155 | }; | |
156 | ||
157 | /* | |
158 | * The access checkers compiled for the configured allowance and denial lists | |
159 | * write to R8 at runtime. The following code prepares for an early exit that | |
160 | * skip the accounting if the packet is denied. | |
161 | * | |
162 | * R0 = 1 | |
163 | * if (R8 == ACCESS_DENIED) | |
164 | * R0 = 0 | |
165 | * | |
166 | * This means that if both ACCESS_DENIED and ACCESS_ALLOWED are set, the packet | |
167 | * is allowed to pass. | |
168 | */ | |
169 | struct bpf_insn post_insn[] = { | |
170 | BPF_MOV64_IMM(BPF_REG_0, 1), | |
171 | BPF_JMP_IMM(BPF_JNE, BPF_REG_8, ACCESS_DENIED, 1), | |
172 | BPF_MOV64_IMM(BPF_REG_0, 0), | |
173 | }; | |
174 | ||
175 | _cleanup_(bpf_program_unrefp) BPFProgram *p = NULL; | |
176 | int accounting_map_fd, r; | |
177 | bool access_enabled; | |
178 | ||
179 | assert(u); | |
180 | assert(ret); | |
181 | ||
182 | accounting_map_fd = is_ingress ? | |
183 | u->ip_accounting_ingress_map_fd : | |
184 | u->ip_accounting_egress_map_fd; | |
185 | ||
186 | access_enabled = | |
187 | u->ipv4_allow_map_fd >= 0 || | |
188 | u->ipv6_allow_map_fd >= 0 || | |
189 | u->ipv4_deny_map_fd >= 0 || | |
190 | u->ipv6_deny_map_fd >= 0; | |
191 | ||
192 | if (accounting_map_fd < 0 && !access_enabled) { | |
193 | *ret = NULL; | |
194 | return 0; | |
195 | } | |
196 | ||
197 | r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &p); | |
198 | if (r < 0) | |
199 | return r; | |
200 | ||
201 | r = bpf_program_add_instructions(p, pre_insn, ELEMENTSOF(pre_insn)); | |
202 | if (r < 0) | |
203 | return r; | |
204 | ||
205 | if (access_enabled) { | |
206 | /* | |
207 | * The simple rule this function translates into eBPF instructions is: | |
208 | * | |
209 | * - Access will be granted when an address matches an entry in @list_allow | |
210 | * - Otherwise, access will be denied when an address matches an entry in @list_deny | |
211 | * - Otherwise, access will be granted | |
212 | */ | |
213 | ||
214 | if (u->ipv4_deny_map_fd >= 0) { | |
215 | r = add_lookup_instructions(p, u->ipv4_deny_map_fd, ETH_P_IP, is_ingress, ACCESS_DENIED); | |
216 | if (r < 0) | |
217 | return r; | |
218 | } | |
219 | ||
220 | if (u->ipv6_deny_map_fd >= 0) { | |
221 | r = add_lookup_instructions(p, u->ipv6_deny_map_fd, ETH_P_IPV6, is_ingress, ACCESS_DENIED); | |
222 | if (r < 0) | |
223 | return r; | |
224 | } | |
225 | ||
226 | if (u->ipv4_allow_map_fd >= 0) { | |
227 | r = add_lookup_instructions(p, u->ipv4_allow_map_fd, ETH_P_IP, is_ingress, ACCESS_ALLOWED); | |
228 | if (r < 0) | |
229 | return r; | |
230 | } | |
231 | ||
232 | if (u->ipv6_allow_map_fd >= 0) { | |
233 | r = add_lookup_instructions(p, u->ipv6_allow_map_fd, ETH_P_IPV6, is_ingress, ACCESS_ALLOWED); | |
234 | if (r < 0) | |
235 | return r; | |
236 | } | |
237 | } | |
238 | ||
239 | r = bpf_program_add_instructions(p, post_insn, ELEMENTSOF(post_insn)); | |
240 | if (r < 0) | |
241 | return r; | |
242 | ||
243 | if (accounting_map_fd >= 0) { | |
244 | struct bpf_insn insn[] = { | |
245 | /* | |
246 | * If R0 == 0, the packet will be denied; skip the accounting instructions in this case. | |
247 | * The jump label will be fixed up later. | |
248 | */ | |
249 | BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 0), | |
250 | ||
251 | /* Count packets */ | |
252 | BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */ | |
253 | BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ | |
254 | BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), | |
255 | BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ | |
256 | BPF_LD_MAP_FD(BPF_REG_1, accounting_map_fd), /* load map fd to r1 */ | |
257 | BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), | |
258 | BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), | |
259 | BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */ | |
260 | BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ | |
261 | ||
262 | /* Count bytes */ | |
263 | BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */ | |
264 | BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ | |
265 | BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), | |
266 | BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ | |
267 | BPF_LD_MAP_FD(BPF_REG_1, accounting_map_fd), | |
268 | BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), | |
269 | BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), | |
270 | BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */ | |
271 | BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ | |
272 | ||
273 | /* Allow the packet to pass */ | |
274 | BPF_MOV64_IMM(BPF_REG_0, 1), | |
275 | }; | |
276 | ||
277 | /* Jump label fixup */ | |
278 | insn[0].off = ELEMENTSOF(insn) - 1; | |
279 | ||
280 | r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn)); | |
281 | if (r < 0) | |
282 | return r; | |
283 | } | |
284 | ||
285 | do { | |
286 | /* | |
287 | * Exit from the eBPF program, R0 contains the verdict. | |
288 | * 0 means the packet is denied, 1 means the packet may pass. | |
289 | */ | |
290 | struct bpf_insn insn[] = { | |
291 | BPF_EXIT_INSN() | |
292 | }; | |
293 | ||
294 | r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn)); | |
295 | if (r < 0) | |
296 | return r; | |
297 | } while (false); | |
298 | ||
1cc6c93a | 299 | *ret = TAKE_PTR(p); |
1988a9d1 DM |
300 | |
301 | return 0; | |
302 | } | |
303 | ||
304 | static int bpf_firewall_count_access_items(IPAddressAccessItem *list, size_t *n_ipv4, size_t *n_ipv6) { | |
305 | IPAddressAccessItem *a; | |
306 | ||
307 | assert(n_ipv4); | |
308 | assert(n_ipv6); | |
309 | ||
310 | LIST_FOREACH(items, a, list) { | |
311 | switch (a->family) { | |
312 | ||
313 | case AF_INET: | |
314 | (*n_ipv4)++; | |
315 | break; | |
316 | ||
317 | case AF_INET6: | |
318 | (*n_ipv6)++; | |
319 | break; | |
320 | ||
321 | default: | |
322 | return -EAFNOSUPPORT; | |
323 | } | |
324 | } | |
325 | ||
326 | return 0; | |
327 | } | |
328 | ||
329 | static int bpf_firewall_add_access_items( | |
330 | IPAddressAccessItem *list, | |
331 | int ipv4_map_fd, | |
332 | int ipv6_map_fd, | |
333 | int verdict) { | |
334 | ||
335 | struct bpf_lpm_trie_key *key_ipv4, *key_ipv6; | |
336 | uint64_t value = verdict; | |
337 | IPAddressAccessItem *a; | |
338 | int r; | |
339 | ||
340 | key_ipv4 = alloca0(offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)); | |
341 | key_ipv6 = alloca0(offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t) * 4); | |
342 | ||
343 | LIST_FOREACH(items, a, list) { | |
344 | switch (a->family) { | |
345 | ||
346 | case AF_INET: | |
347 | key_ipv4->prefixlen = a->prefixlen; | |
348 | memcpy(key_ipv4->data, &a->address, sizeof(uint32_t)); | |
349 | ||
350 | r = bpf_map_update_element(ipv4_map_fd, key_ipv4, &value); | |
351 | if (r < 0) | |
352 | return r; | |
353 | ||
354 | break; | |
355 | ||
356 | case AF_INET6: | |
357 | key_ipv6->prefixlen = a->prefixlen; | |
358 | memcpy(key_ipv6->data, &a->address, 4 * sizeof(uint32_t)); | |
359 | ||
360 | r = bpf_map_update_element(ipv6_map_fd, key_ipv6, &value); | |
361 | if (r < 0) | |
362 | return r; | |
363 | ||
364 | break; | |
365 | ||
366 | default: | |
367 | return -EAFNOSUPPORT; | |
368 | } | |
369 | } | |
370 | ||
371 | return 0; | |
372 | } | |
373 | ||
374 | static int bpf_firewall_prepare_access_maps( | |
375 | Unit *u, | |
376 | int verdict, | |
377 | int *ret_ipv4_map_fd, | |
378 | int *ret_ipv6_map_fd) { | |
379 | ||
380 | _cleanup_close_ int ipv4_map_fd = -1, ipv6_map_fd = -1; | |
381 | size_t n_ipv4 = 0, n_ipv6 = 0; | |
382 | Unit *p; | |
383 | int r; | |
384 | ||
385 | assert(ret_ipv4_map_fd); | |
386 | assert(ret_ipv6_map_fd); | |
387 | ||
388 | for (p = u; p; p = UNIT_DEREF(p->slice)) { | |
389 | CGroupContext *cc; | |
390 | ||
391 | cc = unit_get_cgroup_context(p); | |
392 | if (!cc) | |
393 | continue; | |
394 | ||
395 | bpf_firewall_count_access_items(verdict == ACCESS_ALLOWED ? cc->ip_address_allow : cc->ip_address_deny, &n_ipv4, &n_ipv6); | |
396 | } | |
397 | ||
398 | if (n_ipv4 > 0) { | |
399 | ipv4_map_fd = bpf_map_new( | |
400 | BPF_MAP_TYPE_LPM_TRIE, | |
401 | offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t), | |
402 | sizeof(uint64_t), | |
403 | n_ipv4, | |
404 | BPF_F_NO_PREALLOC); | |
405 | if (ipv4_map_fd < 0) | |
406 | return ipv4_map_fd; | |
407 | } | |
408 | ||
409 | if (n_ipv6 > 0) { | |
410 | ipv6_map_fd = bpf_map_new( | |
411 | BPF_MAP_TYPE_LPM_TRIE, | |
412 | offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4, | |
413 | sizeof(uint64_t), | |
414 | n_ipv6, | |
415 | BPF_F_NO_PREALLOC); | |
416 | if (ipv6_map_fd < 0) | |
417 | return ipv6_map_fd; | |
418 | } | |
419 | ||
420 | for (p = u; p; p = UNIT_DEREF(p->slice)) { | |
421 | CGroupContext *cc; | |
422 | ||
423 | cc = unit_get_cgroup_context(p); | |
424 | if (!cc) | |
425 | continue; | |
426 | ||
427 | r = bpf_firewall_add_access_items(verdict == ACCESS_ALLOWED ? cc->ip_address_allow : cc->ip_address_deny, | |
428 | ipv4_map_fd, ipv6_map_fd, verdict); | |
429 | if (r < 0) | |
430 | return r; | |
431 | } | |
432 | ||
433 | *ret_ipv4_map_fd = ipv4_map_fd; | |
434 | *ret_ipv6_map_fd = ipv6_map_fd; | |
435 | ||
436 | ipv4_map_fd = ipv6_map_fd = -1; | |
437 | return 0; | |
438 | } | |
439 | ||
51283461 | 440 | static int bpf_firewall_prepare_accounting_maps(Unit *u, bool enabled, int *fd_ingress, int *fd_egress) { |
1988a9d1 DM |
441 | int r; |
442 | ||
51283461 | 443 | assert(u); |
1988a9d1 DM |
444 | assert(fd_ingress); |
445 | assert(fd_egress); | |
446 | ||
447 | if (enabled) { | |
448 | if (*fd_ingress < 0) { | |
449 | r = bpf_map_new(BPF_MAP_TYPE_ARRAY, sizeof(int), sizeof(uint64_t), 2, 0); | |
450 | if (r < 0) | |
451 | return r; | |
452 | ||
453 | *fd_ingress = r; | |
454 | } | |
455 | ||
456 | if (*fd_egress < 0) { | |
457 | ||
458 | r = bpf_map_new(BPF_MAP_TYPE_ARRAY, sizeof(int), sizeof(uint64_t), 2, 0); | |
459 | if (r < 0) | |
460 | return r; | |
461 | ||
462 | *fd_egress = r; | |
463 | } | |
51283461 | 464 | |
1988a9d1 DM |
465 | } else { |
466 | *fd_ingress = safe_close(*fd_ingress); | |
467 | *fd_egress = safe_close(*fd_egress); | |
51283461 LP |
468 | |
469 | zero(u->ip_accounting_extra); | |
1988a9d1 DM |
470 | } |
471 | ||
472 | return 0; | |
473 | } | |
474 | ||
475 | int bpf_firewall_compile(Unit *u) { | |
476 | CGroupContext *cc; | |
acf7f253 | 477 | int r, supported; |
1988a9d1 DM |
478 | |
479 | assert(u); | |
480 | ||
51283461 LP |
481 | cc = unit_get_cgroup_context(u); |
482 | if (!cc) | |
483 | return -EINVAL; | |
484 | ||
acf7f253 LP |
485 | supported = bpf_firewall_supported(); |
486 | if (supported < 0) | |
487 | return supported; | |
84d2744b ZJS |
488 | if (supported == BPF_FIREWALL_UNSUPPORTED) |
489 | return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), | |
490 | "BPF firewalling not supported on this manager, proceeding without."); | |
491 | if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI && u->type == UNIT_SLICE) | |
acf7f253 LP |
492 | /* If BPF_F_ALLOW_MULTI is not supported we don't support any BPF magic on inner nodes (i.e. on slice |
493 | * units), since that would mean leaf nodes couldn't do any BPF anymore at all. Under the assumption | |
494 | * that BPF is more interesting on leaf nodes we hence avoid it on inner nodes in that case. This is | |
495 | * consistent with old systemd behaviour from before v238, where BPF wasn't supported in inner nodes at | |
496 | * all, either. */ | |
84d2744b ZJS |
497 | return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), |
498 | "BPF_F_ALLOW_MULTI is not supported on this manager, not doing BPF firewall on slice units."); | |
1988a9d1 DM |
499 | |
500 | /* Note that when we compile a new firewall we first flush out the access maps and the BPF programs themselves, | |
501 | * but we reuse the the accounting maps. That way the firewall in effect always maps to the actual | |
502 | * configuration, but we don't flush out the accounting unnecessarily */ | |
503 | ||
504 | u->ip_bpf_ingress = bpf_program_unref(u->ip_bpf_ingress); | |
505 | u->ip_bpf_egress = bpf_program_unref(u->ip_bpf_egress); | |
506 | ||
507 | u->ipv4_allow_map_fd = safe_close(u->ipv4_allow_map_fd); | |
508 | u->ipv4_deny_map_fd = safe_close(u->ipv4_deny_map_fd); | |
509 | ||
510 | u->ipv6_allow_map_fd = safe_close(u->ipv6_allow_map_fd); | |
511 | u->ipv6_deny_map_fd = safe_close(u->ipv6_deny_map_fd); | |
512 | ||
acf7f253 LP |
513 | if (u->type != UNIT_SLICE) { |
514 | /* In inner nodes we only do accounting, we do not actually bother with access control. However, leaf | |
515 | * nodes will incorporate all IP access rules set on all their parent nodes. This has the benefit that | |
516 | * they can optionally cancel out system-wide rules. Since inner nodes can't contain processes this | |
517 | * means that all configure IP access rules *will* take effect on processes, even though we never | |
518 | * compile them for inner nodes. */ | |
1988a9d1 | 519 | |
acf7f253 LP |
520 | r = bpf_firewall_prepare_access_maps(u, ACCESS_ALLOWED, &u->ipv4_allow_map_fd, &u->ipv6_allow_map_fd); |
521 | if (r < 0) | |
13711093 | 522 | return log_unit_error_errno(u, r, "Preparation of eBPF allow maps failed: %m"); |
acf7f253 LP |
523 | |
524 | r = bpf_firewall_prepare_access_maps(u, ACCESS_DENIED, &u->ipv4_deny_map_fd, &u->ipv6_deny_map_fd); | |
525 | if (r < 0) | |
13711093 | 526 | return log_unit_error_errno(u, r, "Preparation of eBPF deny maps failed: %m"); |
acf7f253 | 527 | } |
1988a9d1 | 528 | |
51283461 | 529 | r = bpf_firewall_prepare_accounting_maps(u, cc->ip_accounting, &u->ip_accounting_ingress_map_fd, &u->ip_accounting_egress_map_fd); |
1988a9d1 | 530 | if (r < 0) |
13711093 | 531 | return log_unit_error_errno(u, r, "Preparation of eBPF accounting maps failed: %m"); |
1988a9d1 DM |
532 | |
533 | r = bpf_firewall_compile_bpf(u, true, &u->ip_bpf_ingress); | |
534 | if (r < 0) | |
13711093 | 535 | return log_unit_error_errno(u, r, "Compilation for ingress BPF program failed: %m"); |
1988a9d1 DM |
536 | |
537 | r = bpf_firewall_compile_bpf(u, false, &u->ip_bpf_egress); | |
538 | if (r < 0) | |
13711093 | 539 | return log_unit_error_errno(u, r, "Compilation for egress BPF program failed: %m"); |
1988a9d1 DM |
540 | |
541 | return 0; | |
542 | } | |
543 | ||
544 | int bpf_firewall_install(Unit *u) { | |
545 | _cleanup_free_ char *path = NULL; | |
9f2e6892 | 546 | CGroupContext *cc; |
acf7f253 | 547 | int r, supported; |
aa2b6f1d | 548 | uint32_t flags; |
1988a9d1 DM |
549 | |
550 | assert(u); | |
551 | ||
9f2e6892 LP |
552 | cc = unit_get_cgroup_context(u); |
553 | if (!cc) | |
554 | return -EINVAL; | |
aa2b6f1d LP |
555 | if (!u->cgroup_path) |
556 | return -EINVAL; | |
557 | if (!u->cgroup_realized) | |
558 | return -EINVAL; | |
9f2e6892 | 559 | |
acf7f253 LP |
560 | supported = bpf_firewall_supported(); |
561 | if (supported < 0) | |
562 | return supported; | |
563 | if (supported == BPF_FIREWALL_UNSUPPORTED) { | |
13711093 | 564 | log_unit_debug(u, "BPF firewalling not supported on this manager, proceeding without."); |
1988a9d1 DM |
565 | return -EOPNOTSUPP; |
566 | } | |
acf7f253 | 567 | if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI && u->type == UNIT_SLICE) { |
13711093 | 568 | log_unit_debug(u, "BPF_F_ALLOW_MULTI is not supported on this manager, not doing BPF firewall on slice units."); |
acf7f253 LP |
569 | return -EOPNOTSUPP; |
570 | } | |
1988a9d1 DM |
571 | |
572 | r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, NULL, &path); | |
573 | if (r < 0) | |
13711093 | 574 | return log_unit_error_errno(u, r, "Failed to determine cgroup path: %m"); |
1988a9d1 | 575 | |
acf7f253 LP |
576 | flags = (supported == BPF_FIREWALL_SUPPORTED_WITH_MULTI && |
577 | (u->type == UNIT_SLICE || unit_cgroup_delegate(u))) ? BPF_F_ALLOW_MULTI : 0; | |
578 | ||
aa2b6f1d LP |
579 | /* Unref the old BPF program (which will implicitly detach it) right before attaching the new program, to |
580 | * minimize the time window when we don't account for IP traffic. */ | |
581 | u->ip_bpf_egress_installed = bpf_program_unref(u->ip_bpf_egress_installed); | |
582 | u->ip_bpf_ingress_installed = bpf_program_unref(u->ip_bpf_ingress_installed); | |
1988a9d1 | 583 | |
aa2b6f1d | 584 | if (u->ip_bpf_egress) { |
acf7f253 | 585 | r = bpf_program_cgroup_attach(u->ip_bpf_egress, BPF_CGROUP_INET_EGRESS, path, flags); |
1988a9d1 | 586 | if (r < 0) |
13711093 | 587 | return log_unit_error_errno(u, r, "Attaching egress BPF program to cgroup %s failed: %m", path); |
aa2b6f1d LP |
588 | |
589 | /* Remember that this BPF program is installed now. */ | |
590 | u->ip_bpf_egress_installed = bpf_program_ref(u->ip_bpf_egress); | |
1988a9d1 DM |
591 | } |
592 | ||
593 | if (u->ip_bpf_ingress) { | |
acf7f253 | 594 | r = bpf_program_cgroup_attach(u->ip_bpf_ingress, BPF_CGROUP_INET_INGRESS, path, flags); |
1988a9d1 | 595 | if (r < 0) |
13711093 | 596 | return log_unit_error_errno(u, r, "Attaching ingress BPF program to cgroup %s failed: %m", path); |
aa2b6f1d LP |
597 | |
598 | u->ip_bpf_ingress_installed = bpf_program_ref(u->ip_bpf_ingress); | |
1988a9d1 DM |
599 | } |
600 | ||
601 | return 0; | |
602 | } | |
603 | ||
604 | int bpf_firewall_read_accounting(int map_fd, uint64_t *ret_bytes, uint64_t *ret_packets) { | |
605 | uint64_t key, packets; | |
606 | int r; | |
607 | ||
608 | if (map_fd < 0) | |
609 | return -EBADF; | |
610 | ||
611 | if (ret_packets) { | |
612 | key = MAP_KEY_PACKETS; | |
613 | r = bpf_map_lookup_element(map_fd, &key, &packets); | |
614 | if (r < 0) | |
615 | return r; | |
616 | } | |
617 | ||
618 | if (ret_bytes) { | |
619 | key = MAP_KEY_BYTES; | |
620 | r = bpf_map_lookup_element(map_fd, &key, ret_bytes); | |
621 | if (r < 0) | |
622 | return r; | |
623 | } | |
624 | ||
625 | if (ret_packets) | |
626 | *ret_packets = packets; | |
627 | ||
628 | return 0; | |
629 | } | |
630 | ||
631 | int bpf_firewall_reset_accounting(int map_fd) { | |
632 | uint64_t key, value = 0; | |
633 | int r; | |
634 | ||
635 | if (map_fd < 0) | |
636 | return -EBADF; | |
637 | ||
638 | key = MAP_KEY_PACKETS; | |
639 | r = bpf_map_update_element(map_fd, &key, &value); | |
640 | if (r < 0) | |
641 | return r; | |
642 | ||
643 | key = MAP_KEY_BYTES; | |
644 | return bpf_map_update_element(map_fd, &key, &value); | |
645 | } | |
646 | ||
f140ed02 ZJS |
647 | static int bpf_firewall_unsupported_reason = 0; |
648 | ||
1988a9d1 | 649 | int bpf_firewall_supported(void) { |
93e93da5 LP |
650 | struct bpf_insn trivial[] = { |
651 | BPF_MOV64_IMM(BPF_REG_0, 1), | |
652 | BPF_EXIT_INSN() | |
653 | }; | |
654 | ||
655 | _cleanup_(bpf_program_unrefp) BPFProgram *program = NULL; | |
1988a9d1 | 656 | static int supported = -1; |
e583759b | 657 | union bpf_attr attr; |
1988a9d1 DM |
658 | int fd, r; |
659 | ||
e583759b | 660 | /* Checks whether BPF firewalling is supported. For this, we check five things: |
1988a9d1 DM |
661 | * |
662 | * a) whether we are privileged | |
663 | * b) whether the unified hierarchy is being used | |
664 | * c) the BPF implementation in the kernel supports BPF LPM TRIE maps, which we require | |
e583759b | 665 | * d) the BPF implementation in the kernel supports BPF_PROG_TYPE_CGROUP_SKB programs, which we require |
047de7e1 | 666 | * e) the BPF implementation in the kernel supports the BPF_PROG_DETACH call, which we require |
1988a9d1 DM |
667 | */ |
668 | ||
669 | if (supported >= 0) | |
670 | return supported; | |
671 | ||
93e93da5 | 672 | if (geteuid() != 0) { |
f140ed02 ZJS |
673 | bpf_firewall_unsupported_reason = |
674 | log_debug_errno(SYNTHETIC_ERRNO(EACCES), | |
675 | "Not enough privileges, BPF firewalling is not supported."); | |
2ae7ee58 | 676 | return supported = BPF_FIREWALL_UNSUPPORTED; |
93e93da5 | 677 | } |
1988a9d1 DM |
678 | |
679 | r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER); | |
680 | if (r < 0) | |
681 | return log_error_errno(r, "Can't determine whether the unified hierarchy is used: %m"); | |
e583759b | 682 | if (r == 0) { |
f140ed02 ZJS |
683 | bpf_firewall_unsupported_reason = |
684 | log_debug_errno(SYNTHETIC_ERRNO(EUCLEAN), | |
685 | "Not running with unified cgroups, BPF firewalling is not supported."); | |
2ae7ee58 | 686 | return supported = BPF_FIREWALL_UNSUPPORTED; |
e583759b | 687 | } |
1988a9d1 DM |
688 | |
689 | fd = bpf_map_new(BPF_MAP_TYPE_LPM_TRIE, | |
690 | offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint64_t), | |
691 | sizeof(uint64_t), | |
692 | 1, | |
693 | BPF_F_NO_PREALLOC); | |
694 | if (fd < 0) { | |
f140ed02 ZJS |
695 | bpf_firewall_unsupported_reason = |
696 | log_debug_errno(fd, "Can't allocate BPF LPM TRIE map, BPF firewalling is not supported: %m"); | |
2ae7ee58 | 697 | return supported = BPF_FIREWALL_UNSUPPORTED; |
1988a9d1 DM |
698 | } |
699 | ||
700 | safe_close(fd); | |
701 | ||
4355f1c9 ZJS |
702 | r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &program); |
703 | if (r < 0) { | |
f140ed02 ZJS |
704 | bpf_firewall_unsupported_reason = |
705 | log_debug_errno(r, "Can't allocate CGROUP SKB BPF program, BPF firewalling is not supported: %m"); | |
2ae7ee58 | 706 | return supported = BPF_FIREWALL_UNSUPPORTED; |
93e93da5 LP |
707 | } |
708 | ||
709 | r = bpf_program_add_instructions(program, trivial, ELEMENTSOF(trivial)); | |
710 | if (r < 0) { | |
f140ed02 ZJS |
711 | bpf_firewall_unsupported_reason = |
712 | log_debug_errno(r, "Can't add trivial instructions to CGROUP SKB BPF program, BPF firewalling is not supported: %m"); | |
2ae7ee58 | 713 | return supported = BPF_FIREWALL_UNSUPPORTED; |
93e93da5 LP |
714 | } |
715 | ||
716 | r = bpf_program_load_kernel(program, NULL, 0); | |
717 | if (r < 0) { | |
f140ed02 ZJS |
718 | bpf_firewall_unsupported_reason = |
719 | log_debug_errno(r, "Can't load kernel CGROUP SKB BPF program, BPF firewalling is not supported: %m"); | |
2ae7ee58 | 720 | return supported = BPF_FIREWALL_UNSUPPORTED; |
93e93da5 LP |
721 | } |
722 | ||
e583759b LP |
723 | /* Unfortunately the kernel allows us to create BPF_PROG_TYPE_CGROUP_SKB programs even when CONFIG_CGROUP_BPF |
724 | * is turned off at kernel compilation time. This sucks of course: why does it allow us to create a cgroup BPF | |
725 | * program if we can't do a thing with it later? | |
726 | * | |
047de7e1 | 727 | * We detect this case by issuing the BPF_PROG_DETACH bpf() call with invalid file descriptors: if |
e583759b LP |
728 | * CONFIG_CGROUP_BPF is turned off, then the call will fail early with EINVAL. If it is turned on the |
729 | * parameters are validated however, and that'll fail with EBADF then. */ | |
730 | ||
731 | attr = (union bpf_attr) { | |
732 | .attach_type = BPF_CGROUP_INET_EGRESS, | |
733 | .target_fd = -1, | |
734 | .attach_bpf_fd = -1, | |
735 | }; | |
736 | ||
047de7e1 | 737 | if (bpf(BPF_PROG_DETACH, &attr, sizeof(attr)) < 0) { |
2ae7ee58 | 738 | if (errno != EBADF) { |
f140ed02 ZJS |
739 | bpf_firewall_unsupported_reason = |
740 | log_debug_errno(errno, "Didn't get EBADF from BPF_PROG_DETACH, BPF firewalling is not supported: %m"); | |
2ae7ee58 LP |
741 | return supported = BPF_FIREWALL_UNSUPPORTED; |
742 | } | |
743 | ||
744 | /* YAY! */ | |
745 | } else { | |
047de7e1 | 746 | log_debug("Wut? Kernel accepted our invalid BPF_PROG_DETACH call? Something is weird, assuming BPF firewalling is broken and hence not supported."); |
2ae7ee58 LP |
747 | return supported = BPF_FIREWALL_UNSUPPORTED; |
748 | } | |
e583759b | 749 | |
2ae7ee58 | 750 | /* So now we know that the BPF program is generally available, let's see if BPF_F_ALLOW_MULTI is also supported |
047de7e1 AF |
751 | * (which was added in kernel 4.15). We use a similar logic as before, but this time we use the BPF_PROG_ATTACH |
752 | * bpf() call and the BPF_F_ALLOW_MULTI flags value. Since the flags are checked early in the system call we'll | |
753 | * get EINVAL if it's not supported, and EBADF as before if it is available. */ | |
e583759b | 754 | |
2ae7ee58 LP |
755 | attr = (union bpf_attr) { |
756 | .attach_type = BPF_CGROUP_INET_EGRESS, | |
757 | .target_fd = -1, | |
758 | .attach_bpf_fd = -1, | |
759 | .attach_flags = BPF_F_ALLOW_MULTI, | |
760 | }; | |
761 | ||
b1c05b98 | 762 | if (bpf(BPF_PROG_ATTACH, &attr, sizeof(attr)) < 0) { |
2ae7ee58 LP |
763 | if (errno == EBADF) { |
764 | log_debug_errno(errno, "Got EBADF when using BPF_F_ALLOW_MULTI, which indicates it is supported. Yay!"); | |
765 | return supported = BPF_FIREWALL_SUPPORTED_WITH_MULTI; | |
766 | } | |
767 | ||
768 | if (errno == EINVAL) | |
769 | log_debug_errno(errno, "Got EINVAL error when using BPF_F_ALLOW_MULTI, which indicates it's not supported."); | |
770 | else | |
771 | log_debug_errno(errno, "Got unexpected error when using BPF_F_ALLOW_MULTI, assuming it's not supported: %m"); | |
772 | ||
773 | return supported = BPF_FIREWALL_SUPPORTED; | |
774 | } else { | |
775 | log_debug("Wut? Kernel accepted our invalid BPF_PROG_ATTACH+BPF_F_ALLOW_MULTI call? Something is weird, assuming BPF firewalling is broken and hence not supported."); | |
776 | return supported = BPF_FIREWALL_UNSUPPORTED; | |
777 | } | |
1988a9d1 | 778 | } |
84d2744b ZJS |
779 | |
780 | void emit_bpf_firewall_warning(Unit *u) { | |
781 | static bool warned = false; | |
782 | ||
783 | if (!warned) { | |
f140ed02 ZJS |
784 | bool quiet = bpf_firewall_unsupported_reason == -EPERM && detect_container(); |
785 | ||
786 | log_unit_full(u, quiet ? LOG_DEBUG : LOG_WARNING, bpf_firewall_unsupported_reason, | |
787 | "unit configures an IP firewall, but %s.\n" | |
788 | "(This warning is only shown for the first unit using IP firewalling.)", | |
789 | getuid() != 0 ? "not running as root" : | |
790 | "the local system does not support BPF/cgroup firewalling"); | |
84d2744b ZJS |
791 | warned = true; |
792 | } | |
793 | } |