Jorge Lucangeli Obes | a6b034d | 2012-08-07 15:29:20 -0700 | [diff] [blame] | 1 | /* Copyright (c) 2012 The Chromium OS Authors. All rights reserved. |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 2 | * Use of this source code is governed by a BSD-style license that can be |
| 3 | * found in the LICENSE file. |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 4 | */ |
| 5 | |
Jorge Lucangeli Obes | 960b56b | 2017-11-17 11:49:58 -0500 | [diff] [blame] | 6 | #include <errno.h> |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 7 | #include <stdio.h> |
| 8 | #include <stdlib.h> |
| 9 | #include <string.h> |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 10 | |
| 11 | #include "syscall_filter.h" |
| 12 | |
Jorge Lucangeli Obes | a6b034d | 2012-08-07 15:29:20 -0700 | [diff] [blame] | 13 | #include "util.h" |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 14 | |
Jorge Lucangeli Obes | 3dc257c | 2016-11-01 12:25:04 -0400 | [diff] [blame] | 15 | /* clang-format off */ |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 16 | #define MAX_POLICY_LINE_LENGTH 1024 |
| 17 | |
Jorge Lucangeli Obes | a6b034d | 2012-08-07 15:29:20 -0700 | [diff] [blame] | 18 | #define ONE_INSTR 1 |
| 19 | #define TWO_INSTRS 2 |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 20 | |
| 21 | #define compiler_warn(_state, _msg, ...) \ |
| 22 | warn("%s: %s(%zd): " _msg, __func__, (_state)->filename, \ |
| 23 | (_state)->line_number, ## __VA_ARGS__) |
| 24 | |
| 25 | #define compiler_pwarn(_state, _msg, ...) \ |
| 26 | compiler_warn(_state, _msg ": %m", ## __VA_ARGS__) |
Jorge Lucangeli Obes | 3dc257c | 2016-11-01 12:25:04 -0400 | [diff] [blame] | 27 | /* clang-format on */ |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 28 | |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 29 | int seccomp_can_softfail(void) |
Jorge Lucangeli Obes | 7b2e29c | 2016-08-04 12:21:03 -0400 | [diff] [blame] | 30 | { |
Jorge Lucangeli Obes | 565e978 | 2016-08-05 11:03:19 -0400 | [diff] [blame] | 31 | #if defined(USE_SECCOMP_SOFTFAIL) |
Jeff Vander Stoep | 1022fc3 | 2016-08-28 12:24:55 -0700 | [diff] [blame] | 32 | return 1; |
Jorge Lucangeli Obes | 7b2e29c | 2016-08-04 12:21:03 -0400 | [diff] [blame] | 33 | #endif |
| 34 | return 0; |
| 35 | } |
| 36 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 37 | int str_to_op(const char *op_str) |
| 38 | { |
| 39 | if (!strcmp(op_str, "==")) { |
| 40 | return EQ; |
| 41 | } else if (!strcmp(op_str, "!=")) { |
| 42 | return NE; |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 43 | } else if (!strcmp(op_str, "&")) { |
| 44 | return SET; |
Jorge Lucangeli Obes | fd6f8e3 | 2016-10-12 11:19:28 -0400 | [diff] [blame] | 45 | } else if (!strcmp(op_str, "in")) { |
| 46 | return IN; |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 47 | } else { |
| 48 | return 0; |
| 49 | } |
| 50 | } |
| 51 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 52 | struct sock_filter *new_instr_buf(size_t count) |
| 53 | { |
| 54 | struct sock_filter *buf = calloc(count, sizeof(struct sock_filter)); |
| 55 | if (!buf) |
Jorge Lucangeli Obes | 224e427 | 2012-08-02 14:31:39 -0700 | [diff] [blame] | 56 | die("could not allocate BPF instruction buffer"); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 57 | |
| 58 | return buf; |
| 59 | } |
| 60 | |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 61 | struct filter_block *new_filter_block(void) |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 62 | { |
| 63 | struct filter_block *block = calloc(1, sizeof(struct filter_block)); |
| 64 | if (!block) |
| 65 | die("could not allocate BPF filter block"); |
| 66 | |
| 67 | block->instrs = NULL; |
| 68 | block->last = block->next = NULL; |
| 69 | |
| 70 | return block; |
| 71 | } |
| 72 | |
Jorge Lucangeli Obes | 565e978 | 2016-08-05 11:03:19 -0400 | [diff] [blame] | 73 | void append_filter_block(struct filter_block *head, struct sock_filter *instrs, |
| 74 | size_t len) |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 75 | { |
| 76 | struct filter_block *new_last; |
| 77 | |
| 78 | /* |
| 79 | * If |head| has no filter assigned yet, |
| 80 | * we don't create a new node. |
| 81 | */ |
| 82 | if (head->instrs == NULL) { |
| 83 | new_last = head; |
| 84 | } else { |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 85 | new_last = new_filter_block(); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 86 | if (head->next != NULL) { |
| 87 | head->last->next = new_last; |
| 88 | head->last = new_last; |
| 89 | } else { |
| 90 | head->last = head->next = new_last; |
| 91 | } |
| 92 | head->total_len += len; |
| 93 | } |
| 94 | |
| 95 | new_last->instrs = instrs; |
| 96 | new_last->total_len = new_last->len = len; |
| 97 | new_last->last = new_last->next = NULL; |
| 98 | } |
| 99 | |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 100 | void extend_filter_block_list(struct filter_block *list, |
Jorge Lucangeli Obes | 565e978 | 2016-08-05 11:03:19 -0400 | [diff] [blame] | 101 | struct filter_block *another) |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 102 | { |
| 103 | if (list->last != NULL) { |
| 104 | list->last->next = another; |
| 105 | list->last = another->last; |
| 106 | } else { |
| 107 | list->next = another; |
| 108 | list->last = another->last; |
| 109 | } |
| 110 | list->total_len += another->total_len; |
| 111 | } |
| 112 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 113 | void append_ret_kill(struct filter_block *head) |
| 114 | { |
| 115 | struct sock_filter *filter = new_instr_buf(ONE_INSTR); |
| 116 | set_bpf_ret_kill(filter); |
| 117 | append_filter_block(head, filter, ONE_INSTR); |
| 118 | } |
| 119 | |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 120 | void append_ret_trap(struct filter_block *head) |
| 121 | { |
| 122 | struct sock_filter *filter = new_instr_buf(ONE_INSTR); |
| 123 | set_bpf_ret_trap(filter); |
| 124 | append_filter_block(head, filter, ONE_INSTR); |
| 125 | } |
| 126 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 127 | void append_ret_errno(struct filter_block *head, int errno_val) |
| 128 | { |
| 129 | struct sock_filter *filter = new_instr_buf(ONE_INSTR); |
| 130 | set_bpf_ret_errno(filter, errno_val); |
| 131 | append_filter_block(head, filter, ONE_INSTR); |
| 132 | } |
| 133 | |
Jorge Lucangeli Obes | c8b21e1 | 2014-06-13 14:26:16 -0700 | [diff] [blame] | 134 | void append_allow_syscall(struct filter_block *head, int nr) |
| 135 | { |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 136 | struct sock_filter *filter = new_instr_buf(ALLOW_SYSCALL_LEN); |
| 137 | size_t len = bpf_allow_syscall(filter, nr); |
| 138 | if (len != ALLOW_SYSCALL_LEN) |
| 139 | die("error building syscall number comparison"); |
| 140 | |
| 141 | append_filter_block(head, filter, len); |
| 142 | } |
| 143 | |
Jorge Lucangeli Obes | 713f6fb | 2016-10-03 13:03:25 -0400 | [diff] [blame] | 144 | void allow_logging_syscalls(struct filter_block *head) |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 145 | { |
| 146 | unsigned int i; |
Kees Cook | 03b2af2 | 2014-12-18 17:11:13 -0800 | [diff] [blame] | 147 | for (i = 0; i < log_syscalls_len; i++) { |
| 148 | warn("allowing syscall: %s", log_syscalls[i]); |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 149 | append_allow_syscall(head, lookup_syscall(log_syscalls[i])); |
Kees Cook | 03b2af2 | 2014-12-18 17:11:13 -0800 | [diff] [blame] | 150 | } |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 151 | } |
| 152 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 153 | unsigned int get_label_id(struct bpf_labels *labels, const char *label_str) |
| 154 | { |
| 155 | int label_id = bpf_label_id(labels, label_str); |
| 156 | if (label_id < 0) |
Jorge Lucangeli Obes | 224e427 | 2012-08-02 14:31:39 -0700 | [diff] [blame] | 157 | die("could not allocate BPF label string"); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 158 | return label_id; |
| 159 | } |
| 160 | |
| 161 | unsigned int group_end_lbl(struct bpf_labels *labels, int nr, int idx) |
| 162 | { |
| 163 | char lbl_str[MAX_BPF_LABEL_LEN]; |
| 164 | snprintf(lbl_str, MAX_BPF_LABEL_LEN, "%d_%d_end", nr, idx); |
| 165 | return get_label_id(labels, lbl_str); |
| 166 | } |
| 167 | |
| 168 | unsigned int success_lbl(struct bpf_labels *labels, int nr) |
| 169 | { |
| 170 | char lbl_str[MAX_BPF_LABEL_LEN]; |
| 171 | snprintf(lbl_str, MAX_BPF_LABEL_LEN, "%d_success", nr); |
| 172 | return get_label_id(labels, lbl_str); |
| 173 | } |
| 174 | |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 175 | int is_implicit_relative_path(const char *filename) |
| 176 | { |
| 177 | return filename[0] != '/' && (filename[0] != '.' || filename[1] != '/'); |
| 178 | } |
| 179 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 180 | int compile_atom(struct parser_state *state, struct filter_block *head, |
| 181 | char *atom, struct bpf_labels *labels, int nr, int grp_idx) |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 182 | { |
| 183 | /* Splits the atom. */ |
Luis Hector Chavez | 95582e7 | 2017-09-05 09:13:25 -0700 | [diff] [blame] | 184 | char *atom_ptr = NULL; |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 185 | char *argidx_str = strtok_r(atom, " ", &atom_ptr); |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 186 | if (argidx_str == NULL) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 187 | compiler_warn(state, "empty atom"); |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 188 | return -1; |
| 189 | } |
| 190 | |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 191 | char *operator_str = strtok_r(NULL, " ", &atom_ptr); |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 192 | if (operator_str == NULL) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 193 | compiler_warn(state, "invalid atom '%s'", argidx_str); |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 194 | return -1; |
| 195 | } |
| 196 | |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 197 | char *constant_str = strtok_r(NULL, " ", &atom_ptr); |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 198 | if (constant_str == NULL) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 199 | compiler_warn(state, "invalid atom '%s %s'", argidx_str, |
| 200 | operator_str); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 201 | return -1; |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 202 | } |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 203 | |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 204 | /* Checks that there are no extra tokens. */ |
| 205 | const char *extra = strtok_r(NULL, " ", &atom_ptr); |
| 206 | if (extra != NULL) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 207 | compiler_warn(state, "extra token '%s'", extra); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 208 | return -1; |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 209 | } |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 210 | |
| 211 | if (strncmp(argidx_str, "arg", 3)) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 212 | compiler_warn(state, "invalid argument token '%s'", argidx_str); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 213 | return -1; |
| 214 | } |
| 215 | |
| 216 | char *argidx_ptr; |
| 217 | long int argidx = strtol(argidx_str + 3, &argidx_ptr, 10); |
| 218 | /* |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 219 | * Checks that an actual argument index was parsed, |
| 220 | * and that there was nothing left after the index. |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 221 | */ |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 222 | if (argidx_ptr == argidx_str + 3 || *argidx_ptr != '\0') { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 223 | compiler_warn(state, "invalid argument index '%s'", |
| 224 | argidx_str + 3); |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 225 | return -1; |
| 226 | } |
| 227 | |
| 228 | int op = str_to_op(operator_str); |
| 229 | if (op < MIN_OPERATOR) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 230 | compiler_warn(state, "invalid operator '%s'", operator_str); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 231 | return -1; |
Jorge Lucangeli Obes | 5389540 | 2016-10-18 12:02:58 -0400 | [diff] [blame] | 232 | } |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 233 | |
Luis Hector Chavez | 40b2574 | 2013-09-22 19:44:06 -0700 | [diff] [blame] | 234 | char *constant_str_ptr; |
| 235 | long int c = parse_constant(constant_str, &constant_str_ptr); |
Jorge Lucangeli Obes | 5389540 | 2016-10-18 12:02:58 -0400 | [diff] [blame] | 236 | if (constant_str_ptr == constant_str) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 237 | compiler_warn(state, "invalid constant '%s'", constant_str); |
Luis Hector Chavez | 40b2574 | 2013-09-22 19:44:06 -0700 | [diff] [blame] | 238 | return -1; |
Jorge Lucangeli Obes | 5389540 | 2016-10-18 12:02:58 -0400 | [diff] [blame] | 239 | } |
Luis Hector Chavez | 40b2574 | 2013-09-22 19:44:06 -0700 | [diff] [blame] | 240 | |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 241 | /* |
| 242 | * Looks up the label for the end of the AND statement |
| 243 | * this atom belongs to. |
| 244 | */ |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 245 | unsigned int id = group_end_lbl(labels, nr, grp_idx); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 246 | |
| 247 | /* |
| 248 | * Builds a BPF comparison between a syscall argument |
| 249 | * and a constant. |
| 250 | * The comparison lives inside an AND statement. |
| 251 | * If the comparison succeeds, we continue |
| 252 | * to the next comparison. |
| 253 | * If this comparison fails, the whole AND statement |
| 254 | * will fail, so we jump to the end of this AND statement. |
| 255 | */ |
| 256 | struct sock_filter *comp_block; |
| 257 | size_t len = bpf_arg_comp(&comp_block, op, argidx, c, id); |
| 258 | if (len == 0) |
| 259 | return -1; |
| 260 | |
| 261 | append_filter_block(head, comp_block, len); |
| 262 | return 0; |
| 263 | } |
| 264 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 265 | int compile_errno(struct parser_state *state, struct filter_block *head, |
| 266 | char *ret_errno, int use_ret_trap) |
Jorge Lucangeli Obes | c8b21e1 | 2014-06-13 14:26:16 -0700 | [diff] [blame] | 267 | { |
Kees Cook | ddb7970 | 2017-04-12 16:36:45 -0700 | [diff] [blame] | 268 | char *errno_ptr = NULL; |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 269 | |
| 270 | /* Splits the 'return' keyword and the actual errno value. */ |
| 271 | char *ret_str = strtok_r(ret_errno, " ", &errno_ptr); |
Luis Hector Chavez | 52f3dd7 | 2017-09-01 19:14:22 -0700 | [diff] [blame] | 272 | if (!ret_str || strncmp(ret_str, "return", strlen("return"))) |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 273 | return -1; |
| 274 | |
| 275 | char *errno_val_str = strtok_r(NULL, " ", &errno_ptr); |
| 276 | |
| 277 | if (errno_val_str) { |
| 278 | char *errno_val_ptr; |
Luis Hector Chavez | 40b2574 | 2013-09-22 19:44:06 -0700 | [diff] [blame] | 279 | int errno_val = parse_constant(errno_val_str, &errno_val_ptr); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 280 | /* Checks to see if we parsed an actual errno. */ |
Jorge Lucangeli Obes | 5389540 | 2016-10-18 12:02:58 -0400 | [diff] [blame] | 281 | if (errno_val_ptr == errno_val_str || errno_val == -1) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 282 | compiler_warn(state, "invalid errno value '%s'", |
| 283 | errno_val_ptr); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 284 | return -1; |
Jorge Lucangeli Obes | 5389540 | 2016-10-18 12:02:58 -0400 | [diff] [blame] | 285 | } |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 286 | |
| 287 | append_ret_errno(head, errno_val); |
| 288 | } else { |
Jorge Lucangeli Obes | 713f6fb | 2016-10-03 13:03:25 -0400 | [diff] [blame] | 289 | if (!use_ret_trap) |
Jennifer Pullman | c0bfae0 | 2016-05-26 17:00:36 -0700 | [diff] [blame] | 290 | append_ret_kill(head); |
| 291 | else |
| 292 | append_ret_trap(head); |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 293 | } |
| 294 | return 0; |
| 295 | } |
| 296 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 297 | struct filter_block *compile_policy_line(struct parser_state *state, int nr, |
| 298 | const char *policy_line, |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 299 | unsigned int entry_lbl_id, |
| 300 | struct bpf_labels *labels, |
| 301 | int use_ret_trap) |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 302 | { |
| 303 | /* |
| 304 | * |policy_line| should be an expression of the form: |
| 305 | * "arg0 == 3 && arg1 == 5 || arg0 == 0x8" |
| 306 | * |
| 307 | * This is, an expression in DNF (disjunctive normal form); |
| 308 | * a disjunction ('||') of one or more conjunctions ('&&') |
| 309 | * of one or more atoms. |
| 310 | * |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 311 | * Atoms are of the form "arg{DNUM} {OP} {NUM}" |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 312 | * where: |
| 313 | * - DNUM is a decimal number. |
Jorge Lucangeli Obes | 21c3ab1 | 2016-10-12 18:37:37 -0400 | [diff] [blame] | 314 | * - OP is an operator: ==, !=, & (flags set), or 'in' (inclusion). |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 315 | * - NUM is an octal, decimal, or hexadecimal number. |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 316 | * |
| 317 | * When the syscall arguments make the expression true, |
| 318 | * the syscall is allowed. If not, the process is killed. |
| 319 | * |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 320 | * To block a syscall without killing the process, |
| 321 | * |policy_line| can be of the form: |
| 322 | * "return <errno>" |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 323 | * |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 324 | * This "return {NUM}" policy line will block the syscall, |
| 325 | * make it return -1 and set |errno| to NUM. |
| 326 | * |
| 327 | * A regular policy line can also include a "return <errno>" clause, |
| 328 | * separated by a semicolon (';'): |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 329 | * "arg0 == 3 && arg1 == 5 || arg0 == 0x8; return {NUM}" |
| 330 | * |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 331 | * If the syscall arguments don't make the expression true, |
| 332 | * the syscall will be blocked as above instead of killing the process. |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 333 | */ |
| 334 | |
| 335 | size_t len = 0; |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 336 | int grp_idx = 0; |
| 337 | |
| 338 | /* Checks for empty policy lines. */ |
| 339 | if (strlen(policy_line) == 0) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 340 | compiler_warn(state, "empty policy line"); |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 341 | return NULL; |
| 342 | } |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 343 | |
| 344 | /* Checks for overly long policy lines. */ |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 345 | if (strlen(policy_line) >= MAX_POLICY_LINE_LENGTH) |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 346 | return NULL; |
| 347 | |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 348 | /* We will modify |policy_line|, so let's make a copy. */ |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 349 | char *line = strndup(policy_line, MAX_POLICY_LINE_LENGTH); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 350 | if (!line) |
| 351 | return NULL; |
| 352 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 353 | /* |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 354 | * We build the filter section as a collection of smaller |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 355 | * "filter blocks" linked together in a singly-linked list. |
| 356 | */ |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 357 | struct filter_block *head = new_filter_block(); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 358 | |
| 359 | /* |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 360 | * Filter sections begin with a label where the main filter |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 361 | * will jump after checking the syscall number. |
| 362 | */ |
| 363 | struct sock_filter *entry_label = new_instr_buf(ONE_INSTR); |
| 364 | set_bpf_lbl(entry_label, entry_lbl_id); |
| 365 | append_filter_block(head, entry_label, ONE_INSTR); |
| 366 | |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 367 | /* Checks whether we're unconditionally blocking this syscall. */ |
| 368 | if (strncmp(line, "return", strlen("return")) == 0) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 369 | if (compile_errno(state, head, line, use_ret_trap) < 0) { |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 370 | free_block_list(head); |
| 371 | free(line); |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 372 | return NULL; |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 373 | } |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 374 | free(line); |
| 375 | return head; |
| 376 | } |
| 377 | |
| 378 | /* Splits the optional "return <errno>" part. */ |
| 379 | char *line_ptr; |
| 380 | char *arg_filter = strtok_r(line, ";", &line_ptr); |
| 381 | char *ret_errno = strtok_r(NULL, ";", &line_ptr); |
| 382 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 383 | /* |
| 384 | * Splits the policy line by '||' into conjunctions and each conjunction |
| 385 | * by '&&' into atoms. |
| 386 | */ |
Jorge Lucangeli Obes | 66cfc14 | 2012-11-30 15:42:52 -0800 | [diff] [blame] | 387 | char *arg_filter_str = arg_filter; |
| 388 | char *group; |
| 389 | while ((group = tokenize(&arg_filter_str, "||")) != NULL) { |
| 390 | char *group_str = group; |
| 391 | char *comp; |
| 392 | while ((comp = tokenize(&group_str, "&&")) != NULL) { |
| 393 | /* Compiles each atom into a BPF block. */ |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 394 | if (compile_atom(state, head, comp, labels, nr, |
| 395 | grp_idx) < 0) { |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 396 | free_block_list(head); |
| 397 | free(line); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 398 | return NULL; |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 399 | } |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 400 | } |
| 401 | /* |
| 402 | * If the AND statement succeeds, we're done, |
| 403 | * so jump to SUCCESS line. |
| 404 | */ |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 405 | unsigned int id = success_lbl(labels, nr); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 406 | struct sock_filter *group_end_block = new_instr_buf(TWO_INSTRS); |
| 407 | len = set_bpf_jump_lbl(group_end_block, id); |
| 408 | /* |
| 409 | * The end of each AND statement falls after the |
| 410 | * jump to SUCCESS. |
| 411 | */ |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 412 | id = group_end_lbl(labels, nr, grp_idx++); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 413 | len += set_bpf_lbl(group_end_block + len, id); |
| 414 | append_filter_block(head, group_end_block, len); |
| 415 | } |
| 416 | |
| 417 | /* |
| 418 | * If no AND statements succeed, we end up here, |
| 419 | * because we never jumped to SUCCESS. |
| 420 | * If we have to return an errno, do it, |
| 421 | * otherwise just kill the task. |
| 422 | */ |
| 423 | if (ret_errno) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 424 | if (compile_errno(state, head, ret_errno, use_ret_trap) < 0) { |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 425 | free_block_list(head); |
| 426 | free(line); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 427 | return NULL; |
Jorge Lucangeli Obes | 1a122b8 | 2016-11-01 11:59:33 -0400 | [diff] [blame] | 428 | } |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 429 | } else { |
Jorge Lucangeli Obes | 713f6fb | 2016-10-03 13:03:25 -0400 | [diff] [blame] | 430 | if (!use_ret_trap) |
Jennifer Pullman | c0bfae0 | 2016-05-26 17:00:36 -0700 | [diff] [blame] | 431 | append_ret_kill(head); |
| 432 | else |
| 433 | append_ret_trap(head); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 434 | } |
| 435 | |
| 436 | /* |
| 437 | * Every time the filter succeeds we jump to a predefined SUCCESS |
| 438 | * label. Add that label and BPF RET_ALLOW code now. |
| 439 | */ |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 440 | unsigned int id = success_lbl(labels, nr); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 441 | struct sock_filter *success_block = new_instr_buf(TWO_INSTRS); |
| 442 | len = set_bpf_lbl(success_block, id); |
| 443 | len += set_bpf_ret_allow(success_block + len); |
| 444 | append_filter_block(head, success_block, len); |
| 445 | |
| 446 | free(line); |
| 447 | return head; |
| 448 | } |
| 449 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 450 | int parse_include_statement(struct parser_state *state, char *policy_line, |
| 451 | unsigned int include_level, |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 452 | const char **ret_filename) |
| 453 | { |
| 454 | if (strncmp("@include", policy_line, strlen("@include")) != 0) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 455 | compiler_warn(state, "invalid statement '%s'", policy_line); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 456 | return -1; |
| 457 | } |
| 458 | |
| 459 | if (policy_line[strlen("@include")] != ' ') { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 460 | compiler_warn(state, "invalid include statement '%s'", |
| 461 | policy_line); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 462 | return -1; |
| 463 | } |
| 464 | |
| 465 | /* |
| 466 | * Disallow nested includes: only the initial policy file can have |
| 467 | * @include statements. |
| 468 | * Nested includes are not currently necessary and make the policy |
| 469 | * harder to understand. |
| 470 | */ |
| 471 | if (include_level > 0) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 472 | compiler_warn(state, "@include statement nested too deep"); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 473 | return -1; |
| 474 | } |
| 475 | |
| 476 | char *statement = policy_line; |
| 477 | /* Discard "@include" token. */ |
| 478 | (void)strsep(&statement, " "); |
| 479 | |
| 480 | /* |
| 481 | * compile_filter() below receives a FILE*, so it's not trivial to open |
| 482 | * included files relative to the initial policy filename. |
| 483 | * To avoid mistakes, force the included file path to be absolute |
| 484 | * (start with '/'), or to explicitly load the file relative to CWD by |
| 485 | * using './'. |
| 486 | */ |
| 487 | const char *filename = statement; |
| 488 | if (is_implicit_relative_path(filename)) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 489 | compiler_warn( |
| 490 | state, |
| 491 | "implicit relative path '%s' not supported, use './%s'", |
| 492 | filename, filename); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 493 | return -1; |
| 494 | } |
| 495 | |
| 496 | *ret_filename = filename; |
| 497 | return 0; |
| 498 | } |
| 499 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 500 | int compile_file(const char *filename, FILE *policy_file, |
| 501 | struct filter_block *head, struct filter_block **arg_blocks, |
| 502 | struct bpf_labels *labels, int use_ret_trap, int allow_logging, |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 503 | unsigned int include_level) |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 504 | { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 505 | /* clang-format off */ |
| 506 | struct parser_state state = { |
| 507 | .filename = filename, |
| 508 | .line_number = 0, |
| 509 | }; |
| 510 | /* clang-format on */ |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 511 | /* |
| 512 | * Loop through all the lines in the policy file. |
| 513 | * Build a jump table for the syscall number. |
| 514 | * If the policy line has an arg filter, build the arg filter |
| 515 | * as well. |
| 516 | * Chain the filter sections together and dump them into |
| 517 | * the final buffer at the end. |
| 518 | */ |
| 519 | char *line = NULL; |
| 520 | size_t len = 0; |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 521 | int ret = 0; |
| 522 | |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 523 | while (getline(&line, &len, policy_file) != -1) { |
| 524 | char *policy_line = line; |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 525 | policy_line = strip(policy_line); |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 526 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 527 | state.line_number++; |
| 528 | |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 529 | /* Allow comments and empty lines. */ |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 530 | if (*policy_line == '#' || *policy_line == '\0') { |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 531 | /* Reuse |line| in the next getline() call. */ |
| 532 | continue; |
| 533 | } |
| 534 | |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 535 | /* Allow @include statements. */ |
| 536 | if (*policy_line == '@') { |
| 537 | const char *filename = NULL; |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 538 | if (parse_include_statement(&state, policy_line, |
| 539 | include_level, |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 540 | &filename) != 0) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 541 | compiler_warn( |
| 542 | &state, |
| 543 | "failed to parse include statement"); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 544 | ret = -1; |
| 545 | goto free_line; |
| 546 | } |
| 547 | |
| 548 | FILE *included_file = fopen(filename, "re"); |
| 549 | if (included_file == NULL) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 550 | compiler_pwarn(&state, "fopen('%s') failed", |
| 551 | filename); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 552 | ret = -1; |
| 553 | goto free_line; |
| 554 | } |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 555 | if (compile_file(filename, included_file, head, |
| 556 | arg_blocks, labels, use_ret_trap, |
| 557 | allow_logging, |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 558 | ++include_level) == -1) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 559 | compiler_warn(&state, "'@include %s' failed", |
| 560 | filename); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 561 | fclose(included_file); |
| 562 | ret = -1; |
| 563 | goto free_line; |
| 564 | } |
| 565 | fclose(included_file); |
| 566 | continue; |
| 567 | } |
| 568 | |
| 569 | /* |
| 570 | * If it's not a comment, or an empty line, or an @include |
| 571 | * statement, treat |policy_line| as a regular policy line. |
| 572 | */ |
| 573 | char *syscall_name = strsep(&policy_line, ":"); |
lhchavez | d0b4070 | 2017-09-01 04:17:41 +0000 | [diff] [blame] | 574 | if (policy_line == NULL) { |
| 575 | warn("compile_file: malformed policy line, missing " |
| 576 | "':'"); |
| 577 | ret = -1; |
| 578 | goto free_line; |
| 579 | } |
| 580 | |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 581 | policy_line = strip(policy_line); |
| 582 | if (*policy_line == '\0') { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 583 | compiler_warn(&state, "empty policy line"); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 584 | ret = -1; |
| 585 | goto free_line; |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 586 | } |
| 587 | |
Jorge Lucangeli Obes | c499257 | 2017-04-28 10:49:01 -0400 | [diff] [blame] | 588 | syscall_name = strip(syscall_name); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 589 | int nr = lookup_syscall(syscall_name); |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 590 | if (nr < 0) { |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 591 | compiler_warn(&state, "nonexistent syscall '%s'", |
| 592 | syscall_name); |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 593 | if (allow_logging) { |
| 594 | /* |
| 595 | * If we're logging failures, assume we're in a |
| 596 | * debugging case and continue. |
| 597 | * This is not super risky because an invalid |
| 598 | * syscall name is likely caused by a typo or by |
| 599 | * leftover lines from a different architecture. |
| 600 | * In either case, not including a policy line |
| 601 | * is equivalent to killing the process if the |
| 602 | * syscall is made, so there's no added attack |
| 603 | * surface. |
| 604 | */ |
| 605 | /* Reuse |line| in the next getline() call. */ |
| 606 | continue; |
| 607 | } |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 608 | ret = -1; |
| 609 | goto free_line; |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 610 | } |
| 611 | |
| 612 | /* |
| 613 | * For each syscall, add either a simple ALLOW, |
| 614 | * or an arg filter block. |
| 615 | */ |
| 616 | if (strcmp(policy_line, "1") == 0) { |
| 617 | /* Add simple ALLOW. */ |
| 618 | append_allow_syscall(head, nr); |
| 619 | } else { |
| 620 | /* |
| 621 | * Create and jump to the label that will hold |
| 622 | * the arg filter block. |
| 623 | */ |
| 624 | unsigned int id = bpf_label_id(labels, syscall_name); |
| 625 | struct sock_filter *nr_comp = |
| 626 | new_instr_buf(ALLOW_SYSCALL_LEN); |
| 627 | bpf_allow_syscall_args(nr_comp, nr, id); |
| 628 | append_filter_block(head, nr_comp, ALLOW_SYSCALL_LEN); |
| 629 | |
| 630 | /* Build the arg filter block. */ |
| 631 | struct filter_block *block = compile_policy_line( |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 632 | &state, nr, policy_line, id, labels, use_ret_trap); |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 633 | |
| 634 | if (!block) { |
| 635 | if (*arg_blocks) { |
| 636 | free_block_list(*arg_blocks); |
lhchavez | d38280c | 2017-09-01 14:00:05 +0000 | [diff] [blame] | 637 | *arg_blocks = NULL; |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 638 | } |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 639 | ret = -1; |
| 640 | goto free_line; |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 641 | } |
| 642 | |
| 643 | if (*arg_blocks) { |
| 644 | extend_filter_block_list(*arg_blocks, block); |
| 645 | } else { |
| 646 | *arg_blocks = block; |
| 647 | } |
| 648 | } |
| 649 | /* Reuse |line| in the next getline() call. */ |
| 650 | } |
Jorge Lucangeli Obes | 960b56b | 2017-11-17 11:49:58 -0500 | [diff] [blame] | 651 | /* getline(3) returned -1. This can mean EOF or the below errors. */ |
| 652 | if (errno == EINVAL || errno == ENOMEM) { |
| 653 | if (*arg_blocks) { |
| 654 | free_block_list(*arg_blocks); |
| 655 | *arg_blocks = NULL; |
| 656 | } |
| 657 | ret = -1; |
| 658 | } |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 659 | |
| 660 | free_line: |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 661 | free(line); |
Jorge Lucangeli Obes | bce4ccb | 2017-03-20 13:38:43 -0400 | [diff] [blame] | 662 | return ret; |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 663 | } |
| 664 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 665 | int compile_filter(const char *filename, FILE *initial_file, |
| 666 | struct sock_fprog *prog, int use_ret_trap, int allow_logging) |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 667 | { |
Luis Hector Chavez | 1a87c8a | 2017-09-02 13:18:31 -0700 | [diff] [blame] | 668 | int ret = 0; |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 669 | struct bpf_labels labels; |
| 670 | labels.count = 0; |
| 671 | |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 672 | if (!initial_file) { |
| 673 | warn("compile_filter: |initial_file| is NULL"); |
Jorge Lucangeli Obes | 6135db9 | 2012-07-27 13:37:30 -0700 | [diff] [blame] | 674 | return -1; |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 675 | } |
Jorge Lucangeli Obes | 6135db9 | 2012-07-27 13:37:30 -0700 | [diff] [blame] | 676 | |
Jorge Lucangeli Obes | d96baf4 | 2013-03-26 15:11:30 -0700 | [diff] [blame] | 677 | struct filter_block *head = new_filter_block(); |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 678 | struct filter_block *arg_blocks = NULL; |
| 679 | |
| 680 | /* Start filter by validating arch. */ |
| 681 | struct sock_filter *valid_arch = new_instr_buf(ARCH_VALIDATION_LEN); |
| 682 | size_t len = bpf_validate_arch(valid_arch); |
| 683 | append_filter_block(head, valid_arch, len); |
| 684 | |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 685 | /* Load syscall number. */ |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 686 | struct sock_filter *load_nr = new_instr_buf(ONE_INSTR); |
| 687 | len = bpf_load_syscall_nr(load_nr); |
| 688 | append_filter_block(head, load_nr, len); |
| 689 | |
Jorge Lucangeli Obes | 713f6fb | 2016-10-03 13:03:25 -0400 | [diff] [blame] | 690 | /* If logging failures, allow the necessary syscalls first. */ |
| 691 | if (allow_logging) |
| 692 | allow_logging_syscalls(head); |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 693 | |
Luis Hector Chavez | 7624e71 | 2017-08-28 19:30:59 -0700 | [diff] [blame] | 694 | if (compile_file(filename, initial_file, head, &arg_blocks, &labels, |
| 695 | use_ret_trap, allow_logging, |
| 696 | 0 /* include_level */) != 0) { |
Jorge Lucangeli Obes | 45932a5 | 2017-03-15 17:02:58 -0400 | [diff] [blame] | 697 | warn("compile_filter: compile_file() failed"); |
Luis Hector Chavez | 1a87c8a | 2017-09-02 13:18:31 -0700 | [diff] [blame] | 698 | ret = -1; |
| 699 | goto free_filter; |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 700 | } |
| 701 | |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 702 | /* |
Jorge Lucangeli Obes | 713f6fb | 2016-10-03 13:03:25 -0400 | [diff] [blame] | 703 | * If none of the syscalls match, either fall through to KILL, |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 704 | * or return TRAP. |
| 705 | */ |
Jorge Lucangeli Obes | 713f6fb | 2016-10-03 13:03:25 -0400 | [diff] [blame] | 706 | if (!use_ret_trap) |
Jorge Lucangeli Obes | bda833c | 2012-07-31 16:25:56 -0700 | [diff] [blame] | 707 | append_ret_kill(head); |
| 708 | else |
| 709 | append_ret_trap(head); |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 710 | |
| 711 | /* Allocate the final buffer, now that we know its size. */ |
Jorge Lucangeli Obes | 565e978 | 2016-08-05 11:03:19 -0400 | [diff] [blame] | 712 | size_t final_filter_len = |
| 713 | head->total_len + (arg_blocks ? arg_blocks->total_len : 0); |
Luis Hector Chavez | 1a87c8a | 2017-09-02 13:18:31 -0700 | [diff] [blame] | 714 | if (final_filter_len > BPF_MAXINSNS) { |
| 715 | ret = -1; |
| 716 | goto free_filter; |
| 717 | } |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 718 | |
| 719 | struct sock_filter *final_filter = |
Jorge Lucangeli Obes | 565e978 | 2016-08-05 11:03:19 -0400 | [diff] [blame] | 720 | calloc(final_filter_len, sizeof(struct sock_filter)); |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 721 | |
Luis Hector Chavez | 1a87c8a | 2017-09-02 13:18:31 -0700 | [diff] [blame] | 722 | if (flatten_block_list(head, final_filter, 0, final_filter_len) < 0) { |
| 723 | free(final_filter); |
| 724 | ret = -1; |
| 725 | goto free_filter; |
| 726 | } |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 727 | |
Jorge Lucangeli Obes | 565e978 | 2016-08-05 11:03:19 -0400 | [diff] [blame] | 728 | if (flatten_block_list(arg_blocks, final_filter, head->total_len, |
Luis Hector Chavez | 1a87c8a | 2017-09-02 13:18:31 -0700 | [diff] [blame] | 729 | final_filter_len) < 0) { |
| 730 | free(final_filter); |
| 731 | ret = -1; |
| 732 | goto free_filter; |
| 733 | } |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 734 | |
Luis Hector Chavez | 1a87c8a | 2017-09-02 13:18:31 -0700 | [diff] [blame] | 735 | if (bpf_resolve_jumps(&labels, final_filter, final_filter_len) < 0) { |
| 736 | free(final_filter); |
| 737 | ret = -1; |
| 738 | goto free_filter; |
| 739 | } |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 740 | |
| 741 | prog->filter = final_filter; |
| 742 | prog->len = final_filter_len; |
Luis Hector Chavez | 1a87c8a | 2017-09-02 13:18:31 -0700 | [diff] [blame] | 743 | |
| 744 | free_filter: |
| 745 | free_block_list(head); |
| 746 | free_block_list(arg_blocks); |
| 747 | free_label_strings(&labels); |
| 748 | return ret; |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 749 | } |
| 750 | |
| 751 | int flatten_block_list(struct filter_block *head, struct sock_filter *filter, |
Jorge Lucangeli Obes | 565e978 | 2016-08-05 11:03:19 -0400 | [diff] [blame] | 752 | size_t index, size_t cap) |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 753 | { |
| 754 | size_t _index = index; |
| 755 | |
| 756 | struct filter_block *curr; |
| 757 | size_t i; |
| 758 | |
| 759 | for (curr = head; curr; curr = curr->next) { |
| 760 | for (i = 0; i < curr->len; i++) { |
| 761 | if (_index >= cap) |
| 762 | return -1; |
| 763 | filter[_index++] = curr->instrs[i]; |
| 764 | } |
| 765 | } |
| 766 | return 0; |
| 767 | } |
| 768 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 769 | void free_block_list(struct filter_block *head) |
| 770 | { |
| 771 | struct filter_block *current, *prev; |
| 772 | |
| 773 | current = head; |
| 774 | while (current) { |
| 775 | free(current->instrs); |
| 776 | prev = current; |
| 777 | current = current->next; |
| 778 | free(prev); |
| 779 | } |
| 780 | } |