| /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
| |
| #include <arpa/inet.h> |
| #include <assert.h> |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <linux/bpf_insn.h> |
| #include <net/ethernet.h> |
| #include <net/if.h> |
| #include <netinet/ip.h> |
| #include <netinet/ip6.h> |
| #include <stddef.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <unistd.h> |
| |
| #include "alloc-util.h" |
| #include "bpf-firewall.h" |
| #include "bpf-program.h" |
| #include "fd-util.h" |
| #include "ip-address-access.h" |
| #include "memory-util.h" |
| #include "missing_syscall.h" |
| #include "unit.h" |
| #include "strv.h" |
| #include "virt.h" |
| |
| enum { |
| MAP_KEY_PACKETS, |
| MAP_KEY_BYTES, |
| }; |
| |
| enum { |
| ACCESS_ALLOWED = 1, |
| ACCESS_DENIED = 2, |
| }; |
| |
| /* Compile instructions for one list of addresses, one direction and one specific verdict on matches. */ |
| |
| static int add_lookup_instructions( |
| BPFProgram *p, |
| int map_fd, |
| int protocol, |
| bool is_ingress, |
| int verdict) { |
| |
| int r, addr_offset, addr_size; |
| |
| assert(p); |
| assert(map_fd >= 0); |
| |
| switch (protocol) { |
| |
| case ETH_P_IP: |
| addr_size = sizeof(uint32_t); |
| addr_offset = is_ingress ? |
| offsetof(struct iphdr, saddr) : |
| offsetof(struct iphdr, daddr); |
| break; |
| |
| case ETH_P_IPV6: |
| addr_size = 4 * sizeof(uint32_t); |
| addr_offset = is_ingress ? |
| offsetof(struct ip6_hdr, ip6_src.s6_addr) : |
| offsetof(struct ip6_hdr, ip6_dst.s6_addr); |
| break; |
| |
| default: |
| return -EAFNOSUPPORT; |
| } |
| |
| do { |
| /* Compare IPv4 with one word instruction (32bit) */ |
| struct bpf_insn insn[] = { |
| /* If skb->protocol != ETH_P_IP, skip this whole block. The offset will be set later. */ |
| BPF_JMP_IMM(BPF_JNE, BPF_REG_7, htobe16(protocol), 0), |
| |
| /* |
| * Call into BPF_FUNC_skb_load_bytes to load the dst/src IP address |
| * |
| * R1: Pointer to the skb |
| * R2: Data offset |
| * R3: Destination buffer on the stack (r10 - 4) |
| * R4: Number of bytes to read (4) |
| */ |
| |
| BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), |
| BPF_MOV32_IMM(BPF_REG_2, addr_offset), |
| |
| BPF_MOV64_REG(BPF_REG_3, BPF_REG_10), |
| BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -addr_size), |
| |
| BPF_MOV32_IMM(BPF_REG_4, addr_size), |
| BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_skb_load_bytes), |
| |
| /* |
| * Call into BPF_FUNC_map_lookup_elem to see if the address matches any entry in the |
| * LPM trie map. For this to work, the prefixlen field of 'struct bpf_lpm_trie_key' |
| * has to be set to the maximum possible value. |
| * |
| * On success, the looked up value is stored in R0. For this application, the actual |
| * value doesn't matter, however; we just set the bit in @verdict in R8 if we found any |
| * matching value. |
| */ |
| |
| BPF_LD_MAP_FD(BPF_REG_1, map_fd), |
| BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), |
| BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -addr_size - sizeof(uint32_t)), |
| BPF_ST_MEM(BPF_W, BPF_REG_2, 0, addr_size * 8), |
| |
| BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), |
| BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1), |
| BPF_ALU32_IMM(BPF_OR, BPF_REG_8, verdict), |
| }; |
| |
| /* Jump label fixup */ |
| insn[0].off = ELEMENTSOF(insn) - 1; |
| |
| r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn)); |
| if (r < 0) |
| return r; |
| |
| } while (false); |
| |
| return 0; |
| } |
| |
| static int add_instructions_for_ip_any( |
| BPFProgram *p, |
| int verdict) { |
| int r; |
| |
| assert(p); |
| |
| const struct bpf_insn insn[] = { |
| BPF_ALU32_IMM(BPF_OR, BPF_REG_8, verdict), |
| }; |
| |
| r = bpf_program_add_instructions(p, insn, 1); |
| if (r < 0) |
| return r; |
| |
| return 0; |
| } |
| |
| static int bpf_firewall_compile_bpf( |
| Unit *u, |
| bool is_ingress, |
| BPFProgram **ret, |
| bool ip_allow_any, |
| bool ip_deny_any) { |
| |
| const struct bpf_insn pre_insn[] = { |
| /* |
| * When the eBPF program is entered, R1 contains the address of the skb. |
| * However, R1-R5 are scratch registers that are not preserved when calling |
| * into kernel functions, so we need to save anything that's supposed to |
| * stay around to R6-R9. Save the skb to R6. |
| */ |
| BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), |
| |
| /* |
| * Although we cannot access the skb data directly from eBPF programs used in this |
| * scenario, the kernel has prepared some fields for us to access through struct __sk_buff. |
| * Load the protocol (IPv4, IPv6) used by the packet in flight once and cache it in R7 |
| * for later use. |
| */ |
| BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6, offsetof(struct __sk_buff, protocol)), |
| |
| /* |
| * R8 is used to keep track of whether any address check has explicitly allowed or denied the packet |
| * through ACCESS_DENIED or ACCESS_ALLOWED bits. Reset them both to 0 in the beginning. |
| */ |
| BPF_MOV32_IMM(BPF_REG_8, 0), |
| }; |
| |
| /* |
| * The access checkers compiled for the configured allowance and denial lists |
| * write to R8 at runtime. The following code prepares for an early exit that |
| * skip the accounting if the packet is denied. |
| * |
| * R0 = 1 |
| * if (R8 == ACCESS_DENIED) |
| * R0 = 0 |
| * |
| * This means that if both ACCESS_DENIED and ACCESS_ALLOWED are set, the packet |
| * is allowed to pass. |
| */ |
| const struct bpf_insn post_insn[] = { |
| BPF_MOV64_IMM(BPF_REG_0, 1), |
| BPF_JMP_IMM(BPF_JNE, BPF_REG_8, ACCESS_DENIED, 1), |
| BPF_MOV64_IMM(BPF_REG_0, 0), |
| }; |
| |
| _cleanup_(bpf_program_unrefp) BPFProgram *p = NULL; |
| int accounting_map_fd, r; |
| bool access_enabled; |
| |
| assert(u); |
| assert(ret); |
| |
| accounting_map_fd = is_ingress ? |
| u->ip_accounting_ingress_map_fd : |
| u->ip_accounting_egress_map_fd; |
| |
| access_enabled = |
| u->ipv4_allow_map_fd >= 0 || |
| u->ipv6_allow_map_fd >= 0 || |
| u->ipv4_deny_map_fd >= 0 || |
| u->ipv6_deny_map_fd >= 0 || |
| ip_allow_any || |
| ip_deny_any; |
| |
| if (accounting_map_fd < 0 && !access_enabled) { |
| *ret = NULL; |
| return 0; |
| } |
| |
| r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &p); |
| if (r < 0) |
| return r; |
| |
| r = bpf_program_add_instructions(p, pre_insn, ELEMENTSOF(pre_insn)); |
| if (r < 0) |
| return r; |
| |
| if (access_enabled) { |
| /* |
| * The simple rule this function translates into eBPF instructions is: |
| * |
| * - Access will be granted when an address matches an entry in @list_allow |
| * - Otherwise, access will be denied when an address matches an entry in @list_deny |
| * - Otherwise, access will be granted |
| */ |
| |
| if (u->ipv4_deny_map_fd >= 0) { |
| r = add_lookup_instructions(p, u->ipv4_deny_map_fd, ETH_P_IP, is_ingress, ACCESS_DENIED); |
| if (r < 0) |
| return r; |
| } |
| |
| if (u->ipv6_deny_map_fd >= 0) { |
| r = add_lookup_instructions(p, u->ipv6_deny_map_fd, ETH_P_IPV6, is_ingress, ACCESS_DENIED); |
| if (r < 0) |
| return r; |
| } |
| |
| if (u->ipv4_allow_map_fd >= 0) { |
| r = add_lookup_instructions(p, u->ipv4_allow_map_fd, ETH_P_IP, is_ingress, ACCESS_ALLOWED); |
| if (r < 0) |
| return r; |
| } |
| |
| if (u->ipv6_allow_map_fd >= 0) { |
| r = add_lookup_instructions(p, u->ipv6_allow_map_fd, ETH_P_IPV6, is_ingress, ACCESS_ALLOWED); |
| if (r < 0) |
| return r; |
| } |
| |
| if (ip_allow_any) { |
| r = add_instructions_for_ip_any(p, ACCESS_ALLOWED); |
| if (r < 0) |
| return r; |
| } |
| |
| if (ip_deny_any) { |
| r = add_instructions_for_ip_any(p, ACCESS_DENIED); |
| if (r < 0) |
| return r; |
| } |
| } |
| |
| r = bpf_program_add_instructions(p, post_insn, ELEMENTSOF(post_insn)); |
| if (r < 0) |
| return r; |
| |
| if (accounting_map_fd >= 0) { |
| struct bpf_insn insn[] = { |
| /* |
| * If R0 == 0, the packet will be denied; skip the accounting instructions in this case. |
| * The jump label will be fixed up later. |
| */ |
| BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 0), |
| |
| /* Count packets */ |
| BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */ |
| BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ |
| BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), |
| BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ |
| BPF_LD_MAP_FD(BPF_REG_1, accounting_map_fd), /* load map fd to r1 */ |
| BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), |
| BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), |
| BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */ |
| BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ |
| |
| /* Count bytes */ |
| BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */ |
| BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */ |
| BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), |
| BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */ |
| BPF_LD_MAP_FD(BPF_REG_1, accounting_map_fd), |
| BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), |
| BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), |
| BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */ |
| BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ |
| |
| /* Allow the packet to pass */ |
| BPF_MOV64_IMM(BPF_REG_0, 1), |
| }; |
| |
| /* Jump label fixup */ |
| insn[0].off = ELEMENTSOF(insn) - 1; |
| |
| r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn)); |
| if (r < 0) |
| return r; |
| } |
| |
| do { |
| /* |
| * Exit from the eBPF program, R0 contains the verdict. |
| * 0 means the packet is denied, 1 means the packet may pass. |
| */ |
| const struct bpf_insn insn[] = { |
| BPF_EXIT_INSN() |
| }; |
| |
| r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn)); |
| if (r < 0) |
| return r; |
| } while (false); |
| |
| *ret = TAKE_PTR(p); |
| |
| return 0; |
| } |
| |
| static int bpf_firewall_count_access_items(IPAddressAccessItem *list, size_t *n_ipv4, size_t *n_ipv6) { |
| IPAddressAccessItem *a; |
| |
| assert(n_ipv4); |
| assert(n_ipv6); |
| |
| LIST_FOREACH(items, a, list) { |
| switch (a->family) { |
| |
| case AF_INET: |
| (*n_ipv4)++; |
| break; |
| |
| case AF_INET6: |
| (*n_ipv6)++; |
| break; |
| |
| default: |
| return -EAFNOSUPPORT; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static int bpf_firewall_add_access_items( |
| IPAddressAccessItem *list, |
| int ipv4_map_fd, |
| int ipv6_map_fd, |
| int verdict) { |
| |
| struct bpf_lpm_trie_key *key_ipv4, *key_ipv6; |
| uint64_t value = verdict; |
| IPAddressAccessItem *a; |
| int r; |
| |
| key_ipv4 = alloca0(offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)); |
| key_ipv6 = alloca0(offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t) * 4); |
| |
| LIST_FOREACH(items, a, list) { |
| switch (a->family) { |
| |
| case AF_INET: |
| key_ipv4->prefixlen = a->prefixlen; |
| memcpy(key_ipv4->data, &a->address, sizeof(uint32_t)); |
| |
| r = bpf_map_update_element(ipv4_map_fd, key_ipv4, &value); |
| if (r < 0) |
| return r; |
| |
| break; |
| |
| case AF_INET6: |
| key_ipv6->prefixlen = a->prefixlen; |
| memcpy(key_ipv6->data, &a->address, 4 * sizeof(uint32_t)); |
| |
| r = bpf_map_update_element(ipv6_map_fd, key_ipv6, &value); |
| if (r < 0) |
| return r; |
| |
| break; |
| |
| default: |
| return -EAFNOSUPPORT; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static int bpf_firewall_prepare_access_maps( |
| Unit *u, |
| int verdict, |
| int *ret_ipv4_map_fd, |
| int *ret_ipv6_map_fd, |
| bool *ret_has_any) { |
| |
| _cleanup_close_ int ipv4_map_fd = -1, ipv6_map_fd = -1; |
| size_t n_ipv4 = 0, n_ipv6 = 0; |
| IPAddressAccessItem *list; |
| Unit *p; |
| int r; |
| |
| assert(ret_ipv4_map_fd); |
| assert(ret_ipv6_map_fd); |
| assert(ret_has_any); |
| |
| for (p = u; p; p = UNIT_GET_SLICE(p)) { |
| CGroupContext *cc; |
| |
| cc = unit_get_cgroup_context(p); |
| if (!cc) |
| continue; |
| |
| list = verdict == ACCESS_ALLOWED ? cc->ip_address_allow : cc->ip_address_deny; |
| |
| bpf_firewall_count_access_items(list, &n_ipv4, &n_ipv6); |
| |
| /* Skip making the LPM trie map in cases where we are using "any" in order to hack around |
| * needing CAP_SYS_ADMIN for allocating LPM trie map. */ |
| if (ip_address_access_item_is_any(list)) { |
| *ret_has_any = true; |
| return 0; |
| } |
| } |
| |
| if (n_ipv4 > 0) { |
| ipv4_map_fd = bpf_map_new( |
| BPF_MAP_TYPE_LPM_TRIE, |
| offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t), |
| sizeof(uint64_t), |
| n_ipv4, |
| BPF_F_NO_PREALLOC); |
| if (ipv4_map_fd < 0) |
| return ipv4_map_fd; |
| } |
| |
| if (n_ipv6 > 0) { |
| ipv6_map_fd = bpf_map_new( |
| BPF_MAP_TYPE_LPM_TRIE, |
| offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4, |
| sizeof(uint64_t), |
| n_ipv6, |
| BPF_F_NO_PREALLOC); |
| if (ipv6_map_fd < 0) |
| return ipv6_map_fd; |
| } |
| |
| for (p = u; p; p = UNIT_GET_SLICE(p)) { |
| CGroupContext *cc; |
| |
| cc = unit_get_cgroup_context(p); |
| if (!cc) |
| continue; |
| |
| r = bpf_firewall_add_access_items(verdict == ACCESS_ALLOWED ? cc->ip_address_allow : cc->ip_address_deny, |
| ipv4_map_fd, ipv6_map_fd, verdict); |
| if (r < 0) |
| return r; |
| } |
| |
| *ret_ipv4_map_fd = TAKE_FD(ipv4_map_fd); |
| *ret_ipv6_map_fd = TAKE_FD(ipv6_map_fd); |
| *ret_has_any = false; |
| return 0; |
| } |
| |
| static int bpf_firewall_prepare_accounting_maps(Unit *u, bool enabled, int *fd_ingress, int *fd_egress) { |
| int r; |
| |
| assert(u); |
| assert(fd_ingress); |
| assert(fd_egress); |
| |
| if (enabled) { |
| if (*fd_ingress < 0) { |
| r = bpf_map_new(BPF_MAP_TYPE_ARRAY, sizeof(int), sizeof(uint64_t), 2, 0); |
| if (r < 0) |
| return r; |
| |
| *fd_ingress = r; |
| } |
| |
| if (*fd_egress < 0) { |
| |
| r = bpf_map_new(BPF_MAP_TYPE_ARRAY, sizeof(int), sizeof(uint64_t), 2, 0); |
| if (r < 0) |
| return r; |
| |
| *fd_egress = r; |
| } |
| |
| } else { |
| *fd_ingress = safe_close(*fd_ingress); |
| *fd_egress = safe_close(*fd_egress); |
| |
| zero(u->ip_accounting_extra); |
| } |
| |
| return 0; |
| } |
| |
| int bpf_firewall_compile(Unit *u) { |
| CGroupContext *cc; |
| int r, supported; |
| bool ip_allow_any = false, ip_deny_any = false; |
| |
| assert(u); |
| |
| cc = unit_get_cgroup_context(u); |
| if (!cc) |
| return -EINVAL; |
| |
| supported = bpf_firewall_supported(); |
| if (supported < 0) |
| return supported; |
| if (supported == BPF_FIREWALL_UNSUPPORTED) |
| return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), |
| "BPF firewalling not supported on this manager, proceeding without."); |
| if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI && u->type == UNIT_SLICE) |
| /* If BPF_F_ALLOW_MULTI is not supported we don't support any BPF magic on inner nodes (i.e. on slice |
| * units), since that would mean leaf nodes couldn't do any BPF anymore at all. Under the assumption |
| * that BPF is more interesting on leaf nodes we hence avoid it on inner nodes in that case. This is |
| * consistent with old systemd behaviour from before v238, where BPF wasn't supported in inner nodes at |
| * all, either. */ |
| return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), |
| "BPF_F_ALLOW_MULTI is not supported on this manager, not doing BPF firewall on slice units."); |
| |
| /* Note that when we compile a new firewall we first flush out the access maps and the BPF programs themselves, |
| * but we reuse the accounting maps. That way the firewall in effect always maps to the actual |
| * configuration, but we don't flush out the accounting unnecessarily */ |
| |
| u->ip_bpf_ingress = bpf_program_unref(u->ip_bpf_ingress); |
| u->ip_bpf_egress = bpf_program_unref(u->ip_bpf_egress); |
| |
| u->ipv4_allow_map_fd = safe_close(u->ipv4_allow_map_fd); |
| u->ipv4_deny_map_fd = safe_close(u->ipv4_deny_map_fd); |
| |
| u->ipv6_allow_map_fd = safe_close(u->ipv6_allow_map_fd); |
| u->ipv6_deny_map_fd = safe_close(u->ipv6_deny_map_fd); |
| |
| if (u->type != UNIT_SLICE) { |
| /* In inner nodes we only do accounting, we do not actually bother with access control. However, leaf |
| * nodes will incorporate all IP access rules set on all their parent nodes. This has the benefit that |
| * they can optionally cancel out system-wide rules. Since inner nodes can't contain processes this |
| * means that all configure IP access rules *will* take effect on processes, even though we never |
| * compile them for inner nodes. */ |
| |
| r = bpf_firewall_prepare_access_maps(u, ACCESS_ALLOWED, &u->ipv4_allow_map_fd, &u->ipv6_allow_map_fd, &ip_allow_any); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Preparation of eBPF allow maps failed: %m"); |
| |
| r = bpf_firewall_prepare_access_maps(u, ACCESS_DENIED, &u->ipv4_deny_map_fd, &u->ipv6_deny_map_fd, &ip_deny_any); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Preparation of eBPF deny maps failed: %m"); |
| } |
| |
| r = bpf_firewall_prepare_accounting_maps(u, cc->ip_accounting, &u->ip_accounting_ingress_map_fd, &u->ip_accounting_egress_map_fd); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Preparation of eBPF accounting maps failed: %m"); |
| |
| r = bpf_firewall_compile_bpf(u, true, &u->ip_bpf_ingress, ip_allow_any, ip_deny_any); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Compilation for ingress BPF program failed: %m"); |
| |
| r = bpf_firewall_compile_bpf(u, false, &u->ip_bpf_egress, ip_allow_any, ip_deny_any); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Compilation for egress BPF program failed: %m"); |
| |
| return 0; |
| } |
| |
| static int load_bpf_progs_from_fs_to_set(Unit *u, char **filter_paths, Set **set) { |
| char **bpf_fs_path; |
| |
| set_clear(*set); |
| |
| STRV_FOREACH(bpf_fs_path, filter_paths) { |
| _cleanup_(bpf_program_unrefp) BPFProgram *prog = NULL; |
| int r; |
| |
| r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &prog); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Can't allocate CGROUP SKB BPF program: %m"); |
| |
| r = bpf_program_load_from_bpf_fs(prog, *bpf_fs_path); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Loading of ingress BPF program %s failed: %m", *bpf_fs_path); |
| |
| r = set_ensure_consume(set, &bpf_program_hash_ops, TAKE_PTR(prog)); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Can't add program to BPF program set: %m"); |
| } |
| |
| return 0; |
| } |
| |
| int bpf_firewall_load_custom(Unit *u) { |
| CGroupContext *cc; |
| int r, supported; |
| |
| assert(u); |
| |
| cc = unit_get_cgroup_context(u); |
| if (!cc) |
| return 0; |
| |
| if (!(cc->ip_filters_ingress || cc->ip_filters_egress)) |
| return 0; |
| |
| supported = bpf_firewall_supported(); |
| if (supported < 0) |
| return supported; |
| |
| if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI) |
| return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), "BPF_F_ALLOW_MULTI not supported on this manager, cannot attach custom BPF programs."); |
| |
| r = load_bpf_progs_from_fs_to_set(u, cc->ip_filters_ingress, &u->ip_bpf_custom_ingress); |
| if (r < 0) |
| return r; |
| r = load_bpf_progs_from_fs_to_set(u, cc->ip_filters_egress, &u->ip_bpf_custom_egress); |
| if (r < 0) |
| return r; |
| |
| return 0; |
| } |
| |
| static int attach_custom_bpf_progs(Unit *u, const char *path, int attach_type, Set **set, Set **set_installed) { |
| BPFProgram *prog; |
| int r; |
| |
| assert(u); |
| |
| set_clear(*set_installed); |
| |
| SET_FOREACH(prog, *set) { |
| r = bpf_program_cgroup_attach(prog, attach_type, path, BPF_F_ALLOW_MULTI); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Attaching custom egress BPF program to cgroup %s failed: %m", path); |
| |
| /* Remember that these BPF programs are installed now. */ |
| r = set_ensure_put(set_installed, &bpf_program_hash_ops, prog); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Can't add program to BPF program set: %m"); |
| |
| bpf_program_ref(prog); |
| } |
| |
| return 0; |
| } |
| |
| int bpf_firewall_install(Unit *u) { |
| _cleanup_(bpf_program_unrefp) BPFProgram *ip_bpf_ingress_uninstall = NULL, *ip_bpf_egress_uninstall = NULL; |
| _cleanup_free_ char *path = NULL; |
| CGroupContext *cc; |
| int r, supported; |
| uint32_t flags; |
| |
| assert(u); |
| |
| cc = unit_get_cgroup_context(u); |
| if (!cc) |
| return -EINVAL; |
| if (!u->cgroup_path) |
| return -EINVAL; |
| if (!u->cgroup_realized) |
| return -EINVAL; |
| |
| supported = bpf_firewall_supported(); |
| if (supported < 0) |
| return supported; |
| if (supported == BPF_FIREWALL_UNSUPPORTED) |
| return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), "BPF firewalling not supported on this manager, proceeding without."); |
| if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI && u->type == UNIT_SLICE) |
| return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), "BPF_F_ALLOW_MULTI is not supported on this manager, not doing BPF firewall on slice units."); |
| if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI && |
| (!set_isempty(u->ip_bpf_custom_ingress) || !set_isempty(u->ip_bpf_custom_egress))) |
| return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), "BPF_F_ALLOW_MULTI not supported on this manager, cannot attach custom BPF programs."); |
| |
| r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, NULL, &path); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Failed to determine cgroup path: %m"); |
| |
| flags = supported == BPF_FIREWALL_SUPPORTED_WITH_MULTI ? BPF_F_ALLOW_MULTI : 0; |
| |
| if (FLAGS_SET(flags, BPF_F_ALLOW_MULTI)) { |
| /* If we have BPF_F_ALLOW_MULTI, then let's clear the fields, but destroy the programs only |
| * after attaching the new programs, so that there's no time window where neither program is |
| * attached. (There will be a program where both are attached, but that's OK, since this is a |
| * security feature where we rather want to lock down too much than too little */ |
| ip_bpf_egress_uninstall = TAKE_PTR(u->ip_bpf_egress_installed); |
| ip_bpf_ingress_uninstall = TAKE_PTR(u->ip_bpf_ingress_installed); |
| } else { |
| /* If we don't have BPF_F_ALLOW_MULTI then unref the old BPF programs (which will implicitly |
| * detach them) right before attaching the new program, to minimize the time window when we |
| * don't account for IP traffic. */ |
| u->ip_bpf_egress_installed = bpf_program_unref(u->ip_bpf_egress_installed); |
| u->ip_bpf_ingress_installed = bpf_program_unref(u->ip_bpf_ingress_installed); |
| } |
| |
| if (u->ip_bpf_egress) { |
| r = bpf_program_cgroup_attach(u->ip_bpf_egress, BPF_CGROUP_INET_EGRESS, path, flags); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Attaching egress BPF program to cgroup %s failed: %m", path); |
| |
| /* Remember that this BPF program is installed now. */ |
| u->ip_bpf_egress_installed = bpf_program_ref(u->ip_bpf_egress); |
| } |
| |
| if (u->ip_bpf_ingress) { |
| r = bpf_program_cgroup_attach(u->ip_bpf_ingress, BPF_CGROUP_INET_INGRESS, path, flags); |
| if (r < 0) |
| return log_unit_error_errno(u, r, "Attaching ingress BPF program to cgroup %s failed: %m", path); |
| |
| u->ip_bpf_ingress_installed = bpf_program_ref(u->ip_bpf_ingress); |
| } |
| |
| /* And now, definitely get rid of the old programs, and detach them */ |
| ip_bpf_egress_uninstall = bpf_program_unref(ip_bpf_egress_uninstall); |
| ip_bpf_ingress_uninstall = bpf_program_unref(ip_bpf_ingress_uninstall); |
| |
| r = attach_custom_bpf_progs(u, path, BPF_CGROUP_INET_EGRESS, &u->ip_bpf_custom_egress, &u->ip_bpf_custom_egress_installed); |
| if (r < 0) |
| return r; |
| |
| r = attach_custom_bpf_progs(u, path, BPF_CGROUP_INET_INGRESS, &u->ip_bpf_custom_ingress, &u->ip_bpf_custom_ingress_installed); |
| if (r < 0) |
| return r; |
| |
| return 0; |
| } |
| |
| int bpf_firewall_read_accounting(int map_fd, uint64_t *ret_bytes, uint64_t *ret_packets) { |
| uint64_t key, packets; |
| int r; |
| |
| if (map_fd < 0) |
| return -EBADF; |
| |
| if (ret_packets) { |
| key = MAP_KEY_PACKETS; |
| r = bpf_map_lookup_element(map_fd, &key, &packets); |
| if (r < 0) |
| return r; |
| } |
| |
| if (ret_bytes) { |
| key = MAP_KEY_BYTES; |
| r = bpf_map_lookup_element(map_fd, &key, ret_bytes); |
| if (r < 0) |
| return r; |
| } |
| |
| if (ret_packets) |
| *ret_packets = packets; |
| |
| return 0; |
| } |
| |
| int bpf_firewall_reset_accounting(int map_fd) { |
| uint64_t key, value = 0; |
| int r; |
| |
| if (map_fd < 0) |
| return -EBADF; |
| |
| key = MAP_KEY_PACKETS; |
| r = bpf_map_update_element(map_fd, &key, &value); |
| if (r < 0) |
| return r; |
| |
| key = MAP_KEY_BYTES; |
| return bpf_map_update_element(map_fd, &key, &value); |
| } |
| |
| static int bpf_firewall_unsupported_reason = 0; |
| |
| int bpf_firewall_supported(void) { |
| const struct bpf_insn trivial[] = { |
| BPF_MOV64_IMM(BPF_REG_0, 1), |
| BPF_EXIT_INSN() |
| }; |
| |
| _cleanup_(bpf_program_unrefp) BPFProgram *program = NULL; |
| static int supported = -1; |
| union bpf_attr attr; |
| int r; |
| |
| /* Checks whether BPF firewalling is supported. For this, we check the following things: |
| * |
| * - whether the unified hierarchy is being used |
| * - the BPF implementation in the kernel supports BPF_PROG_TYPE_CGROUP_SKB programs, which we require |
| * - the BPF implementation in the kernel supports the BPF_PROG_DETACH call, which we require |
| */ |
| if (supported >= 0) |
| return supported; |
| |
| r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER); |
| if (r < 0) |
| return log_error_errno(r, "Can't determine whether the unified hierarchy is used: %m"); |
| if (r == 0) { |
| bpf_firewall_unsupported_reason = |
| log_debug_errno(SYNTHETIC_ERRNO(EUCLEAN), |
| "Not running with unified cgroups, BPF firewalling is not supported."); |
| return supported = BPF_FIREWALL_UNSUPPORTED; |
| } |
| |
| r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &program); |
| if (r < 0) { |
| bpf_firewall_unsupported_reason = |
| log_debug_errno(r, "Can't allocate CGROUP SKB BPF program, BPF firewalling is not supported: %m"); |
| return supported = BPF_FIREWALL_UNSUPPORTED; |
| } |
| |
| r = bpf_program_add_instructions(program, trivial, ELEMENTSOF(trivial)); |
| if (r < 0) { |
| bpf_firewall_unsupported_reason = |
| log_debug_errno(r, "Can't add trivial instructions to CGROUP SKB BPF program, BPF firewalling is not supported: %m"); |
| return supported = BPF_FIREWALL_UNSUPPORTED; |
| } |
| |
| r = bpf_program_load_kernel(program, NULL, 0); |
| if (r < 0) { |
| bpf_firewall_unsupported_reason = |
| log_debug_errno(r, "Can't load kernel CGROUP SKB BPF program, BPF firewalling is not supported: %m"); |
| return supported = BPF_FIREWALL_UNSUPPORTED; |
| } |
| |
| /* Unfortunately the kernel allows us to create BPF_PROG_TYPE_CGROUP_SKB programs even when CONFIG_CGROUP_BPF |
| * is turned off at kernel compilation time. This sucks of course: why does it allow us to create a cgroup BPF |
| * program if we can't do a thing with it later? |
| * |
| * We detect this case by issuing the BPF_PROG_DETACH bpf() call with invalid file descriptors: if |
| * CONFIG_CGROUP_BPF is turned off, then the call will fail early with EINVAL. If it is turned on the |
| * parameters are validated however, and that'll fail with EBADF then. */ |
| |
| // FIXME: Clang doesn't 0-pad with structured initialization, causing |
| // the kernel to reject the bpf_attr as invalid. See: |
| // https://github.com/torvalds/linux/blob/v5.9/kernel/bpf/syscall.c#L65 |
| // Ideally it should behave like GCC, so that we can remove these workarounds. |
| zero(attr); |
| attr.attach_type = BPF_CGROUP_INET_EGRESS; |
| attr.target_fd = -1; |
| attr.attach_bpf_fd = -1; |
| |
| if (bpf(BPF_PROG_DETACH, &attr, sizeof(attr)) < 0) { |
| if (errno != EBADF) { |
| bpf_firewall_unsupported_reason = |
| log_debug_errno(errno, "Didn't get EBADF from BPF_PROG_DETACH, BPF firewalling is not supported: %m"); |
| return supported = BPF_FIREWALL_UNSUPPORTED; |
| } |
| |
| /* YAY! */ |
| } else { |
| bpf_firewall_unsupported_reason = |
| log_debug_errno(SYNTHETIC_ERRNO(EBADE), |
| "Wut? Kernel accepted our invalid BPF_PROG_DETACH call? " |
| "Something is weird, assuming BPF firewalling is broken and hence not supported."); |
| return supported = BPF_FIREWALL_UNSUPPORTED; |
| } |
| |
| /* So now we know that the BPF program is generally available, let's see if BPF_F_ALLOW_MULTI is also supported |
| * (which was added in kernel 4.15). We use a similar logic as before, but this time we use the BPF_PROG_ATTACH |
| * bpf() call and the BPF_F_ALLOW_MULTI flags value. Since the flags are checked early in the system call we'll |
| * get EINVAL if it's not supported, and EBADF as before if it is available. */ |
| |
| zero(attr); |
| attr.attach_type = BPF_CGROUP_INET_EGRESS; |
| attr.target_fd = -1; |
| attr.attach_bpf_fd = -1; |
| attr.attach_flags = BPF_F_ALLOW_MULTI; |
| |
| if (bpf(BPF_PROG_ATTACH, &attr, sizeof(attr)) < 0) { |
| if (errno == EBADF) { |
| log_debug_errno(errno, "Got EBADF when using BPF_F_ALLOW_MULTI, which indicates it is supported. Yay!"); |
| return supported = BPF_FIREWALL_SUPPORTED_WITH_MULTI; |
| } |
| |
| if (errno == EINVAL) |
| log_debug_errno(errno, "Got EINVAL error when using BPF_F_ALLOW_MULTI, which indicates it's not supported."); |
| else |
| log_debug_errno(errno, "Got unexpected error when using BPF_F_ALLOW_MULTI, assuming it's not supported: %m"); |
| |
| return supported = BPF_FIREWALL_SUPPORTED; |
| } else { |
| bpf_firewall_unsupported_reason = |
| log_debug_errno(SYNTHETIC_ERRNO(EBADE), |
| "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."); |
| return supported = BPF_FIREWALL_UNSUPPORTED; |
| } |
| } |
| |
| void emit_bpf_firewall_warning(Unit *u) { |
| static bool warned = false; |
| |
| assert(u); |
| assert(u->manager); |
| |
| if (!warned && !MANAGER_IS_TEST_RUN(u->manager)) { |
| bool quiet = bpf_firewall_unsupported_reason == -EPERM && detect_container() > 0; |
| |
| log_unit_full_errno(u, quiet ? LOG_DEBUG : LOG_WARNING, bpf_firewall_unsupported_reason, |
| "unit configures an IP firewall, but %s.\n" |
| "(This warning is only shown for the first unit using IP firewalling.)", |
| getuid() != 0 ? "not running as root" : |
| "the local system does not support BPF/cgroup firewalling"); |
| warned = true; |
| } |
| } |
| |
| void bpf_firewall_close(Unit *u) { |
| assert(u); |
| |
| u->ip_accounting_ingress_map_fd = safe_close(u->ip_accounting_ingress_map_fd); |
| u->ip_accounting_egress_map_fd = safe_close(u->ip_accounting_egress_map_fd); |
| |
| u->ipv4_allow_map_fd = safe_close(u->ipv4_allow_map_fd); |
| u->ipv6_allow_map_fd = safe_close(u->ipv6_allow_map_fd); |
| u->ipv4_deny_map_fd = safe_close(u->ipv4_deny_map_fd); |
| u->ipv6_deny_map_fd = safe_close(u->ipv6_deny_map_fd); |
| |
| u->ip_bpf_ingress = bpf_program_unref(u->ip_bpf_ingress); |
| u->ip_bpf_ingress_installed = bpf_program_unref(u->ip_bpf_ingress_installed); |
| u->ip_bpf_egress = bpf_program_unref(u->ip_bpf_egress); |
| u->ip_bpf_egress_installed = bpf_program_unref(u->ip_bpf_egress_installed); |
| |
| u->ip_bpf_custom_ingress = set_free(u->ip_bpf_custom_ingress); |
| u->ip_bpf_custom_egress = set_free(u->ip_bpf_custom_egress); |
| u->ip_bpf_custom_ingress_installed = set_free(u->ip_bpf_custom_ingress_installed); |
| u->ip_bpf_custom_egress_installed = set_free(u->ip_bpf_custom_egress_installed); |
| } |
