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 30 FILE_RCSID("@(#)$File: seccomp.c,v 1.29 2024/09/29 16:49:25 christos Exp $") 31 #endif /* lint */ 32 33 #if HAVE_LIBSECCOMP 34 #include <seccomp.h> /* libseccomp */ 35 #include <sys/prctl.h> /* prctl */ 36 #include <sys/ioctl.h> 37 #include <sys/socket.h> 38 #include <termios.h> 39 #include <fcntl.h> 40 #include <stdlib.h> 41 #include <errno.h> 42 43 #define DENY_RULE(call) \ 44 do \ 45 if (seccomp_rule_add (ctx, SCMP_ACT_KILL, SCMP_SYS(call), 0) == -1) \ 46 goto out; \ 47 while (/*CONSTCOND*/0) 48 #define ALLOW_RULE(call) \ 49 do \ 50 if (seccomp_rule_add (ctx, SCMP_ACT_ALLOW, SCMP_SYS(call), 0) == -1) \ 51 goto out; \ 52 while (/*CONSTCOND*/0) 53 54 #define ALLOW_IOCTL_RULE(param) \ 55 do \ 56 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ioctl), 1, \ 57 SCMP_CMP(1, SCMP_CMP_EQ, (scmp_datum_t)param, \ 58 (scmp_datum_t)0)) == -1) \ 59 goto out; \ 60 while (/*CONSTCOND*/0) 61 62 static scmp_filter_ctx ctx; 63 64 int 65 enable_sandbox(void) 66 { 67 68 // prevent child processes from getting more priv e.g. via setuid, 69 // capabilities, ... 70 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) 71 return -1; 72 73 #if 0 74 if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) 75 return -1; 76 #endif 77 78 // initialize the filter 79 ctx = seccomp_init(SCMP_ACT_KILL); 80 if (ctx == NULL) 81 return -1; 82 83 ALLOW_RULE(access); 84 ALLOW_RULE(brk); 85 ALLOW_RULE(close); 86 ALLOW_RULE(dup2); 87 ALLOW_RULE(exit); 88 ALLOW_RULE(exit_group); 89 #ifdef __NR_faccessat 90 ALLOW_RULE(faccessat); 91 #endif 92 ALLOW_RULE(fcntl); 93 ALLOW_RULE(fcntl64); 94 #ifdef __NR_fstat 95 ALLOW_RULE(fstat); 96 #endif 97 ALLOW_RULE(fstat64); 98 #ifdef __NR_fstatat64 99 ALLOW_RULE(fstatat64); 100 #endif 101 ALLOW_RULE(futex); 102 ALLOW_RULE(getdents); 103 #ifdef __NR_getdents64 104 ALLOW_RULE(getdents64); 105 #endif 106 #ifdef FIONREAD 107 // called in src/compress.c under sread 108 ALLOW_IOCTL_RULE(FIONREAD); 109 #endif 110 #ifdef TIOCGWINSZ 111 // musl libc may call ioctl TIOCGWINSZ on stdout 112 ALLOW_IOCTL_RULE(TIOCGWINSZ); 113 #endif 114 #ifdef TCGETS 115 // glibc may call ioctl TCGETS on stdout on physical terminal 116 ALLOW_IOCTL_RULE(TCGETS); 117 #endif 118 ALLOW_RULE(lseek); 119 ALLOW_RULE(_llseek); 120 ALLOW_RULE(lstat); 121 ALLOW_RULE(lstat64); 122 ALLOW_RULE(madvise); 123 ALLOW_RULE(mmap); 124 ALLOW_RULE(mmap2); 125 ALLOW_RULE(mprotect); 126 ALLOW_RULE(mremap); 127 ALLOW_RULE(munmap); 128 #ifdef __NR_newfstatat 129 ALLOW_RULE(newfstatat); 130 #endif 131 ALLOW_RULE(open); 132 ALLOW_RULE(openat); 133 ALLOW_RULE(pread64); 134 ALLOW_RULE(read); 135 ALLOW_RULE(readlink); 136 #ifdef __NR_readlinkat 137 ALLOW_RULE(readlinkat); 138 #endif 139 ALLOW_RULE(rt_sigaction); 140 ALLOW_RULE(rt_sigprocmask); 141 ALLOW_RULE(rt_sigreturn); 142 ALLOW_RULE(select); 143 ALLOW_RULE(stat); 144 ALLOW_RULE(statx); 145 ALLOW_RULE(stat64); 146 ALLOW_RULE(sysinfo); 147 ALLOW_RULE(umask); // Used in file_pipe2file() 148 ALLOW_RULE(getpid); // Used by glibc in file_pipe2file() 149 ALLOW_RULE(getrandom); // Used by glibc in file_pipe2file() 150 ALLOW_RULE(unlink); 151 ALLOW_RULE(utimes); 152 ALLOW_RULE(write); 153 ALLOW_RULE(writev); 154 155 156 #if 0 157 // needed by valgrind 158 ALLOW_RULE(gettid); 159 ALLOW_RULE(rt_sigtimedwait); 160 #endif 161 162 #if 0 163 /* special restrictions for socket, only allow AF_UNIX/AF_LOCAL */ 164 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1, 165 SCMP_CMP(0, SCMP_CMP_EQ, AF_UNIX)) == -1) 166 goto out; 167 168 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 1, 169 SCMP_CMP(0, SCMP_CMP_EQ, AF_LOCAL)) == -1) 170 goto out; 171 172 173 /* special restrictions for open, prevent opening files for writing */ 174 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 1, 175 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY | O_RDWR, 0)) == -1) 176 goto out; 177 178 if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, 179 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_WRONLY, O_WRONLY)) == -1) 180 goto out; 181 182 if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, 183 SCMP_CMP(1, SCMP_CMP_MASKED_EQ, O_RDWR, O_RDWR)) == -1) 184 goto out; 185 186 187 /* allow stderr */ 188 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1, 189 SCMP_CMP(0, SCMP_CMP_EQ, 2)) == -1) 190 goto out; 191 #endif 192 193 #if defined(PR_SET_VMA) && defined(PR_SET_VMA_ANON_NAME) 194 /* allow glibc to name malloc areas */ 195 if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(prctl), 2, 196 SCMP_CMP32(0, SCMP_CMP_EQ, PR_SET_VMA), 197 SCMP_CMP64(1, SCMP_CMP_EQ, PR_SET_VMA_ANON_NAME)) == -1) 198 goto out; 199 #endif 200 201 // applying filter... 202 if (seccomp_load(ctx) == -1) 203 goto out; 204 // free ctx after the filter has been loaded into the kernel 205 seccomp_release(ctx); 206 return 0; 207 208 out: 209 // something went wrong 210 seccomp_release(ctx); 211 return -1; 212 } 213 #endif 214