seccomp.c revision 354939
1/* 2 * Redistribution and use in source and binary forms, with or without 3 * modification, are permitted provided that the following conditions 4 * are met: 5 * 1. Redistributions of source code must retain the above copyright 6 * notice immediately at the beginning of the file, without modification, 7 * this list of conditions, and the following disclaimer. 8 * 2. Redistributions in binary form must reproduce the above copyright 9 * notice, this list of conditions and the following disclaimer in the 10 * documentation and/or other materials provided with the distribution. 11 * 12 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 13 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 14 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 15 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 16 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 17 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 18 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 19 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 20 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 21 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 22 * SUCH DAMAGE. 23 */ 24/* 25 * libseccomp hooks. 26 */ 27#include "file.h" 28 29#ifndef lint 30FILE_RCSID("@(#)$File: seccomp.c,v 1.8 2019/02/24 18:12:04 christos Exp $") 31#endif /* lint */ 32 33#if HAVE_LIBSECCOMP 34#include <seccomp.h> /* libseccomp */ 35#include <sys/prctl.h> /* prctl */ 36#include <sys/socket.h> 37#include <fcntl.h> 38#include <stdlib.h> 39#include <errno.h> 40 41#define DENY_RULE(call) \ 42 do \ 43 if (seccomp_rule_add (ctx, SCMP_ACT_KILL, SCMP_SYS(call), 0) == -1) \ 44 goto out; \ 45 while (/*CONSTCOND*/0) 46#define ALLOW_RULE(call) \ 47 do \ 48 if (seccomp_rule_add (ctx, SCMP_ACT_ALLOW, SCMP_SYS(call), 0) == -1) \ 49 goto out; \ 50 while (/*CONSTCOND*/0) 51 52static scmp_filter_ctx ctx; 53 54 55int 56enable_sandbox_basic(void) 57{ 58 59 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) 60 return -1; 61 62 if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) 63 return -1; 64 65 // initialize the filter 66 ctx = seccomp_init(SCMP_ACT_ALLOW); 67 if (ctx == NULL) 68 return 1; 69 70 DENY_RULE(_sysctl); 71 DENY_RULE(acct); 72 DENY_RULE(add_key); 73 DENY_RULE(adjtimex); 74 DENY_RULE(chroot); 75 DENY_RULE(clock_adjtime); 76 DENY_RULE(create_module); 77 DENY_RULE(delete_module); 78 DENY_RULE(fanotify_init); 79 DENY_RULE(finit_module); 80 DENY_RULE(get_kernel_syms); 81 DENY_RULE(get_mempolicy); 82 DENY_RULE(init_module); 83 DENY_RULE(io_cancel); 84 DENY_RULE(io_destroy); 85 DENY_RULE(io_getevents); 86 DENY_RULE(io_setup); 87 DENY_RULE(io_submit); 88 DENY_RULE(ioperm); 89 DENY_RULE(iopl); 90 DENY_RULE(ioprio_set); 91 DENY_RULE(kcmp); 92#ifdef __NR_kexec_file_load 93 DENY_RULE(kexec_file_load); 94#endif 95 DENY_RULE(kexec_load); 96 DENY_RULE(keyctl); 97 DENY_RULE(lookup_dcookie); 98 DENY_RULE(mbind); 99 DENY_RULE(nfsservctl); 100 DENY_RULE(migrate_pages); 101 DENY_RULE(modify_ldt); 102 DENY_RULE(mount); 103 DENY_RULE(move_pages); 104 DENY_RULE(name_to_handle_at); 105 DENY_RULE(open_by_handle_at); 106 DENY_RULE(perf_event_open); 107 DENY_RULE(pivot_root); 108 DENY_RULE(process_vm_readv); 109 DENY_RULE(process_vm_writev); 110 DENY_RULE(ptrace); 111 DENY_RULE(reboot); 112 DENY_RULE(remap_file_pages); 113 DENY_RULE(request_key); 114 DENY_RULE(set_mempolicy); 115 DENY_RULE(swapoff); 116 DENY_RULE(swapon); 117 DENY_RULE(sysfs); 118 DENY_RULE(syslog); 119 DENY_RULE(tuxcall); 120 DENY_RULE(umount2); 121 DENY_RULE(uselib); 122 DENY_RULE(vmsplice); 123 124 // blocking dangerous syscalls that file should not need 125 DENY_RULE (execve); 126 DENY_RULE (socket); 127 // ... 128 129 130 // applying filter... 131 if (seccomp_load (ctx) == -1) 132 goto out; 133 // free ctx after the filter has been loaded into the kernel 134 seccomp_release(ctx); 135 return 0; 136 137out: 138 seccomp_release(ctx); 139 return -1; 140} 141 142 143int 144enable_sandbox_full(void) 145{ 146 147 // prevent child processes from getting more priv e.g. via setuid, 148 // capabilities, ... 149 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) 150 return -1; 151 152 if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) 153 return -1; 154 155 // initialize the filter 156 ctx = seccomp_init(SCMP_ACT_KILL); 157 if (ctx == NULL) 158 return -1; 159 160 ALLOW_RULE(access); 161 ALLOW_RULE(brk); 162 ALLOW_RULE(close); 163 ALLOW_RULE(dup2); 164 ALLOW_RULE(exit); 165 ALLOW_RULE(exit_group); 166 ALLOW_RULE(fcntl); 167 ALLOW_RULE(fcntl64); 168 ALLOW_RULE(fstat); 169 ALLOW_RULE(fstat64); 170 ALLOW_RULE(getdents); 171#ifdef __NR_getdents64 172 ALLOW_RULE(getdents64); 173#endif 174 ALLOW_RULE(ioctl); 175 ALLOW_RULE(lseek); 176 ALLOW_RULE(_llseek); 177 ALLOW_RULE(lstat); 178 ALLOW_RULE(lstat64); 179 ALLOW_RULE(madvise); 180 ALLOW_RULE(mmap); 181 ALLOW_RULE(mmap2); 182 ALLOW_RULE(mprotect); 183 ALLOW_RULE(mremap); 184 ALLOW_RULE(munmap); 185#ifdef __NR_newfstatat 186 ALLOW_RULE(newfstatat); 187#endif 188 ALLOW_RULE(open); 189 ALLOW_RULE(openat); 190 ALLOW_RULE(pread64); 191 ALLOW_RULE(read); 192 ALLOW_RULE(readlink); 193 ALLOW_RULE(rt_sigaction); 194 ALLOW_RULE(rt_sigprocmask); 195 ALLOW_RULE(rt_sigreturn); 196 ALLOW_RULE(select); 197 ALLOW_RULE(stat); 198 ALLOW_RULE(stat64); 199 ALLOW_RULE(sysinfo); 200 ALLOW_RULE(unlink); 201 ALLOW_RULE(write); 202 203 204#if 0 205 // needed by valgrind 206 ALLOW_RULE(gettid); 207 ALLOW_RULE(getpid); 208 ALLOW_RULE(rt_sigtimedwait); 209#endif 210 211#if 0 212 /* special restrictions for socket, only allow AF_UNIX/AF_LOCAL */ 213 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1, 214 SCMP_CMP(0, SCMP_CMP_EQ, AF_UNIX)) == -1) 215 goto out; 216 217 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1, 218 SCMP_CMP(0, SCMP_CMP_EQ, AF_LOCAL)) == -1) 219 goto out; 220 221 222 /* special restrictions for open, prevent opening files for writing */ 223 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 1, 224 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY | O_RDWR, 0)) == -1) 225 goto out; 226 227 if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, 228 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY, O_WRONLY)) == -1) 229 goto out; 230 231 if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, 232 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_RDWR, O_RDWR)) == -1) 233 goto out; 234 235 236 /* allow stderr */ 237 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1, 238 SCMP_CMP(0, SCMP_CMP_EQ, 2)) == -1) 239 goto out; 240#endif 241 242 // applying filter... 243 if (seccomp_load(ctx) == -1) 244 goto out; 245 // free ctx after the filter has been loaded into the kernel 246 seccomp_release(ctx); 247 return 0; 248 249out: 250 // something went wrong 251 seccomp_release(ctx); 252 return -1; 253} 254#endif 255