1 /* $NetBSD: seccomp.c,v 1.1.1.1 2018/04/15 19:32:48 christos Exp $ */ 2 3 /* 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice immediately at the beginning of the file, without modification, 9 * this list of conditions, and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 18 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 /* 27 * libseccomp hooks. 28 */ 29 #include "file.h" 30 31 #ifndef lint 32 #if 0 33 FILE_RCSID("@(#)$File: seccomp.c,v 1.2 2017/11/04 01:14:25 christos Exp $") 34 #else 35 __RCSID("$NetBSD: seccomp.c,v 1.1.1.1 2018/04/15 19:32:48 christos Exp $"); 36 #endif 37 #endif /* lint */ 38 39 #if HAVE_LIBSECCOMP 40 #include <seccomp.h> /* libseccomp */ 41 #include <sys/prctl.h> /* prctl */ 42 #include <sys/socket.h> 43 #include <fcntl.h> 44 #include <stdlib.h> 45 #include <errno.h> 46 47 #define DENY_RULE(call) \ 48 do \ 49 if (seccomp_rule_add (ctx, SCMP_ACT_KILL, SCMP_SYS(call), 0) == -1) \ 50 goto out; \ 51 while (/*CONSTCOND*/0) 52 #define ALLOW_RULE(call) \ 53 do \ 54 if (seccomp_rule_add (ctx, SCMP_ACT_ALLOW, SCMP_SYS(call), 0) == -1) \ 55 goto out; \ 56 while (/*CONSTCOND*/0) 57 58 static scmp_filter_ctx ctx; 59 60 61 int 62 enable_sandbox_basic(void) 63 { 64 65 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) 66 return -1; 67 68 #if 0 69 // prevent escape via ptrace 70 prctl(PR_SET_DUMPABLE, 0); 71 #endif 72 73 if (prctl (PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) 74 return -1; 75 76 // initialize the filter 77 ctx = seccomp_init(SCMP_ACT_ALLOW); 78 if (ctx == NULL) 79 return 1; 80 81 DENY_RULE(_sysctl); 82 DENY_RULE(acct); 83 DENY_RULE(add_key); 84 DENY_RULE(adjtimex); 85 DENY_RULE(chroot); 86 DENY_RULE(clock_adjtime); 87 DENY_RULE(create_module); 88 DENY_RULE(delete_module); 89 DENY_RULE(fanotify_init); 90 DENY_RULE(finit_module); 91 DENY_RULE(get_kernel_syms); 92 DENY_RULE(get_mempolicy); 93 DENY_RULE(init_module); 94 DENY_RULE(io_cancel); 95 DENY_RULE(io_destroy); 96 DENY_RULE(io_getevents); 97 DENY_RULE(io_setup); 98 DENY_RULE(io_submit); 99 DENY_RULE(ioperm); 100 DENY_RULE(iopl); 101 DENY_RULE(ioprio_set); 102 DENY_RULE(kcmp); 103 #ifdef __NR_kexec_file_load 104 DENY_RULE(kexec_file_load); 105 #endif 106 DENY_RULE(kexec_load); 107 DENY_RULE(keyctl); 108 DENY_RULE(lookup_dcookie); 109 DENY_RULE(mbind); 110 DENY_RULE(nfsservctl); 111 DENY_RULE(migrate_pages); 112 DENY_RULE(modify_ldt); 113 DENY_RULE(mount); 114 DENY_RULE(move_pages); 115 DENY_RULE(name_to_handle_at); 116 DENY_RULE(open_by_handle_at); 117 DENY_RULE(perf_event_open); 118 DENY_RULE(pivot_root); 119 DENY_RULE(process_vm_readv); 120 DENY_RULE(process_vm_writev); 121 DENY_RULE(ptrace); 122 DENY_RULE(reboot); 123 DENY_RULE(remap_file_pages); 124 DENY_RULE(request_key); 125 DENY_RULE(set_mempolicy); 126 DENY_RULE(swapoff); 127 DENY_RULE(swapon); 128 DENY_RULE(sysfs); 129 DENY_RULE(syslog); 130 DENY_RULE(tuxcall); 131 DENY_RULE(umount2); 132 DENY_RULE(uselib); 133 DENY_RULE(vmsplice); 134 135 // blocking dangerous syscalls that file should not need 136 DENY_RULE (execve); 137 DENY_RULE (socket); 138 // ... 139 140 141 // applying filter... 142 if (seccomp_load (ctx) == -1) 143 goto out; 144 // free ctx after the filter has been loaded into the kernel 145 seccomp_release(ctx); 146 return 0; 147 148 out: 149 seccomp_release(ctx); 150 return -1; 151 } 152 153 154 int 155 enable_sandbox_full(void) 156 { 157 158 // prevent child processes from getting more priv e.g. via setuid, 159 // capabilities, ... 160 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) 161 return -1; 162 163 if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) 164 return -1; 165 166 // initialize the filter 167 ctx = seccomp_init(SCMP_ACT_KILL); 168 if (ctx == NULL) 169 return -1; 170 171 ALLOW_RULE(access); 172 ALLOW_RULE(brk); 173 ALLOW_RULE(close); 174 ALLOW_RULE(dup2); 175 ALLOW_RULE(exit); 176 ALLOW_RULE(exit_group); 177 ALLOW_RULE(fcntl); 178 ALLOW_RULE(fstat); 179 ALLOW_RULE(getdents); 180 ALLOW_RULE(ioctl); 181 ALLOW_RULE(lseek); 182 ALLOW_RULE(lstat); 183 ALLOW_RULE(mmap); 184 ALLOW_RULE(mprotect); 185 ALLOW_RULE(mremap); 186 ALLOW_RULE(munmap); 187 ALLOW_RULE(open); 188 ALLOW_RULE(openat); 189 ALLOW_RULE(pread64); 190 ALLOW_RULE(read); 191 ALLOW_RULE(readlink); 192 ALLOW_RULE(rt_sigaction); 193 ALLOW_RULE(rt_sigprocmask); 194 ALLOW_RULE(rt_sigreturn); 195 ALLOW_RULE(select); 196 ALLOW_RULE(stat); 197 ALLOW_RULE(sysinfo); 198 ALLOW_RULE(unlink); 199 ALLOW_RULE(write); 200 201 202 #if 0 203 // needed by valgrind 204 ALLOW_RULE(gettid); 205 ALLOW_RULE(getpid); 206 ALLOW_RULE(rt_sigtimedwait); 207 #endif 208 209 #if 0 210 /* special restrictions for socket, only allow AF_UNIX/AF_LOCAL */ 211 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1, 212 SCMP_CMP(0, SCMP_CMP_EQ, AF_UNIX)) == -1) 213 goto out; 214 215 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1, 216 SCMP_CMP(0, SCMP_CMP_EQ, AF_LOCAL)) == -1) 217 goto out; 218 219 220 /* special restrictions for open, prevent opening files for writing */ 221 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 1, 222 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY | O_RDWR, 0)) == -1) 223 goto out; 224 225 if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, 226 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY, O_WRONLY)) == -1) 227 goto out; 228 229 if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, 230 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_RDWR, O_RDWR)) == -1) 231 goto out; 232 233 234 /* allow stderr */ 235 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1, 236 SCMP_CMP(0, SCMP_CMP_EQ, 2)) == -1) 237 goto out; 238 #endif 239 240 // applying filter... 241 if (seccomp_load(ctx) == -1) 242 goto out; 243 // free ctx after the filter has been loaded into the kernel 244 seccomp_release(ctx); 245 return 0; 246 247 out: 248 // something went wrong 249 seccomp_release(ctx); 250 return -1; 251 } 252 #endif 253