1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Landlock test helpers 4 * 5 * Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net> 6 * Copyright © 2019-2020 ANSSI 7 * Copyright © 2021 Microsoft Corporation 8 */ 9 10 #include <errno.h> 11 #include <linux/landlock.h> 12 #include <linux/securebits.h> 13 #include <sys/capability.h> 14 #include <sys/socket.h> 15 #include <sys/syscall.h> 16 #include <sys/types.h> 17 #include <sys/wait.h> 18 #include <unistd.h> 19 20 #include "../kselftest_harness.h" 21 22 #ifndef __maybe_unused 23 #define __maybe_unused __attribute__((__unused__)) 24 #endif 25 26 /* 27 * TEST_F_FORK() is useful when a test drop privileges but the corresponding 28 * FIXTURE_TEARDOWN() requires them (e.g. to remove files from a directory 29 * where write actions are denied). For convenience, FIXTURE_TEARDOWN() is 30 * also called when the test failed, but not when FIXTURE_SETUP() failed. For 31 * this to be possible, we must not call abort() but instead exit smoothly 32 * (hence the step print). 33 */ 34 /* clang-format off */ 35 #define TEST_F_FORK(fixture_name, test_name) \ 36 static void fixture_name##_##test_name##_child( \ 37 struct __test_metadata *_metadata, \ 38 FIXTURE_DATA(fixture_name) *self, \ 39 const FIXTURE_VARIANT(fixture_name) *variant); \ 40 TEST_F(fixture_name, test_name) \ 41 { \ 42 int status; \ 43 const pid_t child = fork(); \ 44 if (child < 0) \ 45 abort(); \ 46 if (child == 0) { \ 47 _metadata->no_print = 1; \ 48 fixture_name##_##test_name##_child(_metadata, self, variant); \ 49 if (_metadata->skip) \ 50 _exit(255); \ 51 if (_metadata->passed) \ 52 _exit(0); \ 53 _exit(_metadata->step); \ 54 } \ 55 if (child != waitpid(child, &status, 0)) \ 56 abort(); \ 57 if (WIFSIGNALED(status) || !WIFEXITED(status)) { \ 58 _metadata->passed = 0; \ 59 _metadata->step = 1; \ 60 return; \ 61 } \ 62 switch (WEXITSTATUS(status)) { \ 63 case 0: \ 64 _metadata->passed = 1; \ 65 break; \ 66 case 255: \ 67 _metadata->passed = 1; \ 68 _metadata->skip = 1; \ 69 break; \ 70 default: \ 71 _metadata->passed = 0; \ 72 _metadata->step = WEXITSTATUS(status); \ 73 break; \ 74 } \ 75 } \ 76 static void fixture_name##_##test_name##_child( \ 77 struct __test_metadata __attribute__((unused)) *_metadata, \ 78 FIXTURE_DATA(fixture_name) __attribute__((unused)) *self, \ 79 const FIXTURE_VARIANT(fixture_name) \ 80 __attribute__((unused)) *variant) 81 /* clang-format on */ 82 83 #ifndef landlock_create_ruleset 84 static inline int 85 landlock_create_ruleset(const struct landlock_ruleset_attr *const attr, 86 const size_t size, const __u32 flags) 87 { 88 return syscall(__NR_landlock_create_ruleset, attr, size, flags); 89 } 90 #endif 91 92 #ifndef landlock_add_rule 93 static inline int landlock_add_rule(const int ruleset_fd, 94 const enum landlock_rule_type rule_type, 95 const void *const rule_attr, 96 const __u32 flags) 97 { 98 return syscall(__NR_landlock_add_rule, ruleset_fd, rule_type, rule_attr, 99 flags); 100 } 101 #endif 102 103 #ifndef landlock_restrict_self 104 static inline int landlock_restrict_self(const int ruleset_fd, 105 const __u32 flags) 106 { 107 return syscall(__NR_landlock_restrict_self, ruleset_fd, flags); 108 } 109 #endif 110 111 static void _init_caps(struct __test_metadata *const _metadata, bool drop_all) 112 { 113 cap_t cap_p; 114 /* Only these three capabilities are useful for the tests. */ 115 const cap_value_t caps[] = { 116 /* clang-format off */ 117 CAP_DAC_OVERRIDE, 118 CAP_MKNOD, 119 CAP_NET_ADMIN, 120 CAP_NET_BIND_SERVICE, 121 CAP_SYS_ADMIN, 122 CAP_SYS_CHROOT, 123 /* clang-format on */ 124 }; 125 const unsigned int noroot = SECBIT_NOROOT | SECBIT_NOROOT_LOCKED; 126 127 if ((cap_get_secbits() & noroot) != noroot) 128 EXPECT_EQ(0, cap_set_secbits(noroot)); 129 130 cap_p = cap_get_proc(); 131 EXPECT_NE(NULL, cap_p); 132 EXPECT_NE(-1, cap_clear(cap_p)); 133 if (!drop_all) { 134 EXPECT_NE(-1, cap_set_flag(cap_p, CAP_PERMITTED, 135 ARRAY_SIZE(caps), caps, CAP_SET)); 136 } 137 138 /* Automatically resets ambient capabilities. */ 139 EXPECT_NE(-1, cap_set_proc(cap_p)) 140 { 141 TH_LOG("Failed to set capabilities: %s", strerror(errno)); 142 } 143 EXPECT_NE(-1, cap_free(cap_p)); 144 145 /* Quickly checks that ambient capabilities are cleared. */ 146 EXPECT_NE(-1, cap_get_ambient(caps[0])); 147 } 148 149 /* We cannot put such helpers in a library because of kselftest_harness.h . */ 150 static void __maybe_unused disable_caps(struct __test_metadata *const _metadata) 151 { 152 _init_caps(_metadata, false); 153 } 154 155 static void __maybe_unused drop_caps(struct __test_metadata *const _metadata) 156 { 157 _init_caps(_metadata, true); 158 } 159 160 static void _change_cap(struct __test_metadata *const _metadata, 161 const cap_flag_t flag, const cap_value_t cap, 162 const cap_flag_value_t value) 163 { 164 cap_t cap_p; 165 166 cap_p = cap_get_proc(); 167 EXPECT_NE(NULL, cap_p); 168 EXPECT_NE(-1, cap_set_flag(cap_p, flag, 1, &cap, value)); 169 EXPECT_NE(-1, cap_set_proc(cap_p)) 170 { 171 TH_LOG("Failed to set capability %d: %s", cap, strerror(errno)); 172 } 173 EXPECT_NE(-1, cap_free(cap_p)); 174 } 175 176 static void __maybe_unused set_cap(struct __test_metadata *const _metadata, 177 const cap_value_t cap) 178 { 179 _change_cap(_metadata, CAP_EFFECTIVE, cap, CAP_SET); 180 } 181 182 static void __maybe_unused clear_cap(struct __test_metadata *const _metadata, 183 const cap_value_t cap) 184 { 185 _change_cap(_metadata, CAP_EFFECTIVE, cap, CAP_CLEAR); 186 } 187 188 static void __maybe_unused 189 set_ambient_cap(struct __test_metadata *const _metadata, const cap_value_t cap) 190 { 191 _change_cap(_metadata, CAP_INHERITABLE, cap, CAP_SET); 192 193 EXPECT_NE(-1, cap_set_ambient(cap, CAP_SET)) 194 { 195 TH_LOG("Failed to set ambient capability %d: %s", cap, 196 strerror(errno)); 197 } 198 } 199 200 static void __maybe_unused clear_ambient_cap( 201 struct __test_metadata *const _metadata, const cap_value_t cap) 202 { 203 EXPECT_EQ(1, cap_get_ambient(cap)); 204 _change_cap(_metadata, CAP_INHERITABLE, cap, CAP_CLEAR); 205 EXPECT_EQ(0, cap_get_ambient(cap)); 206 } 207 208 /* Receives an FD from a UNIX socket. Returns the received FD, or -errno. */ 209 static int __maybe_unused recv_fd(int usock) 210 { 211 int fd_rx; 212 union { 213 /* Aligned ancillary data buffer. */ 214 char buf[CMSG_SPACE(sizeof(fd_rx))]; 215 struct cmsghdr _align; 216 } cmsg_rx = {}; 217 char data = '\0'; 218 struct iovec io = { 219 .iov_base = &data, 220 .iov_len = sizeof(data), 221 }; 222 struct msghdr msg = { 223 .msg_iov = &io, 224 .msg_iovlen = 1, 225 .msg_control = &cmsg_rx.buf, 226 .msg_controllen = sizeof(cmsg_rx.buf), 227 }; 228 struct cmsghdr *cmsg; 229 int res; 230 231 res = recvmsg(usock, &msg, MSG_CMSG_CLOEXEC); 232 if (res < 0) 233 return -errno; 234 235 cmsg = CMSG_FIRSTHDR(&msg); 236 if (cmsg->cmsg_len != CMSG_LEN(sizeof(fd_rx))) 237 return -EIO; 238 239 memcpy(&fd_rx, CMSG_DATA(cmsg), sizeof(fd_rx)); 240 return fd_rx; 241 } 242 243 /* Sends an FD on a UNIX socket. Returns 0 on success or -errno. */ 244 static int __maybe_unused send_fd(int usock, int fd_tx) 245 { 246 union { 247 /* Aligned ancillary data buffer. */ 248 char buf[CMSG_SPACE(sizeof(fd_tx))]; 249 struct cmsghdr _align; 250 } cmsg_tx = {}; 251 char data_tx = '.'; 252 struct iovec io = { 253 .iov_base = &data_tx, 254 .iov_len = sizeof(data_tx), 255 }; 256 struct msghdr msg = { 257 .msg_iov = &io, 258 .msg_iovlen = 1, 259 .msg_control = &cmsg_tx.buf, 260 .msg_controllen = sizeof(cmsg_tx.buf), 261 }; 262 struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); 263 264 cmsg->cmsg_len = CMSG_LEN(sizeof(fd_tx)); 265 cmsg->cmsg_level = SOL_SOCKET; 266 cmsg->cmsg_type = SCM_RIGHTS; 267 memcpy(CMSG_DATA(cmsg), &fd_tx, sizeof(fd_tx)); 268 269 if (sendmsg(usock, &msg, 0) < 0) 270 return -errno; 271 return 0; 272 } 273 274 static void __maybe_unused 275 enforce_ruleset(struct __test_metadata *const _metadata, const int ruleset_fd) 276 { 277 ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); 278 ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0)) 279 { 280 TH_LOG("Failed to enforce ruleset: %s", strerror(errno)); 281 } 282 } 283