tools/virtiofsd/passthrough_seccomp.c

   1 /*
   2  * Seccomp sandboxing for virtiofsd
   3  *
   4  * Copyright (C) 2019 Red Hat, Inc.
   5  *
   6  * SPDX-License-Identifier: GPL-2.0-or-later
   7  */
   8
   9 #include "qemu/osdep.h"
  10 #include "passthrough_seccomp.h"
  11 #include "fuse_i.h"
  12 #include "fuse_log.h"
  13 #include <errno.h>
  14 #include <glib.h>
  15 #include <seccomp.h>
  16 #include <stdlib.h>
  17
  18 /* Bodge for libseccomp 2.4.2 which broke ppoll */
  19 #if !defined(__SNR_ppoll) && defined(__SNR_brk)
  20 #ifdef __NR_ppoll
  21 #define __SNR_ppoll __NR_ppoll
  22 #else
  23 #define __SNR_ppoll __PNR_ppoll
  24 #endif
  25 #endif
  26
  27 static const int syscall_whitelist[] = {
  28     /* TODO ireg sem*() syscalls */
  29     SCMP_SYS(brk),
  30     SCMP_SYS(capget), /* For CAP_FSETID */
  31     SCMP_SYS(capset),
  32     SCMP_SYS(clock_gettime),
  33     SCMP_SYS(clone),
  34 #ifdef __NR_clone3
  35     SCMP_SYS(clone3),
  36 #endif
  37     SCMP_SYS(close),
  38     SCMP_SYS(copy_file_range),
  39     SCMP_SYS(dup),
  40     SCMP_SYS(eventfd2),
  41     SCMP_SYS(exit),
  42     SCMP_SYS(exit_group),
  43     SCMP_SYS(fallocate),
  44     SCMP_SYS(fchdir),
  45     SCMP_SYS(fchmod),
  46     SCMP_SYS(fchmodat),
  47     SCMP_SYS(fchownat),
  48     SCMP_SYS(fcntl),
  49     SCMP_SYS(fdatasync),
  50     SCMP_SYS(fgetxattr),
  51     SCMP_SYS(flistxattr),
  52     SCMP_SYS(flock),
  53     SCMP_SYS(fremovexattr),
  54     SCMP_SYS(fsetxattr),
  55     SCMP_SYS(fstat),
  56     SCMP_SYS(fstatfs),
  57     SCMP_SYS(fsync),
  58     SCMP_SYS(ftruncate),
  59     SCMP_SYS(futex),
  60     SCMP_SYS(getdents),
  61     SCMP_SYS(getdents64),
  62     SCMP_SYS(getegid),
  63     SCMP_SYS(geteuid),
  64     SCMP_SYS(getpid),
  65     SCMP_SYS(gettid),
  66     SCMP_SYS(gettimeofday),
  67     SCMP_SYS(getxattr),
  68     SCMP_SYS(linkat),
  69     SCMP_SYS(listxattr),
  70     SCMP_SYS(lseek),
  71     SCMP_SYS(madvise),
  72     SCMP_SYS(mkdirat),
  73     SCMP_SYS(mknodat),
  74     SCMP_SYS(mmap),
  75     SCMP_SYS(mprotect),
  76     SCMP_SYS(mremap),
  77     SCMP_SYS(munmap),
  78     SCMP_SYS(newfstatat),
  79     SCMP_SYS(open),
  80     SCMP_SYS(openat),
  81     SCMP_SYS(ppoll),
  82     SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */
  83     SCMP_SYS(preadv),
  84     SCMP_SYS(pread64),
  85     SCMP_SYS(pwritev),
  86     SCMP_SYS(pwrite64),
  87     SCMP_SYS(read),
  88     SCMP_SYS(readlinkat),
  89     SCMP_SYS(recvmsg),
  90     SCMP_SYS(renameat),
  91     SCMP_SYS(renameat2),
  92     SCMP_SYS(removexattr),
  93     SCMP_SYS(rt_sigaction),
  94     SCMP_SYS(rt_sigprocmask),
  95     SCMP_SYS(rt_sigreturn),
  96     SCMP_SYS(sendmsg),
  97     SCMP_SYS(setresgid),
  98     SCMP_SYS(setresuid),
  99 #ifdef __NR_setresgid32
 100     SCMP_SYS(setresgid32),
 101 #endif
 102 #ifdef __NR_setresuid32
 103     SCMP_SYS(setresuid32),
 104 #endif
 105     SCMP_SYS(set_robust_list),
 106     SCMP_SYS(setxattr),
 107     SCMP_SYS(symlinkat),
 108     SCMP_SYS(time), /* Rarely needed, except on static builds */
 109     SCMP_SYS(tgkill),
 110     SCMP_SYS(unlinkat),
 111     SCMP_SYS(unshare),
 112     SCMP_SYS(utimensat),
 113     SCMP_SYS(write),
 114     SCMP_SYS(writev),
 115 };
 116
 117 /* Syscalls used when --syslog is enabled */
 118 static const int syscall_whitelist_syslog[] = {
 119     SCMP_SYS(sendto),
 120 };
 121
 122 static void add_whitelist(scmp_filter_ctx ctx, const int syscalls[], size_t len)
 123 {
 124     size_t i;
 125
 126     for (i = 0; i < len; i++) {
 127         if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, syscalls[i], 0) != 0) {
 128             fuse_log(FUSE_LOG_ERR, "seccomp_rule_add syscall %d failed\n",
 129                      syscalls[i]);
 130             exit(1);
 131         }
 132     }
 133 }
 134
 135 void setup_seccomp(bool enable_syslog)
 136 {
 137     scmp_filter_ctx ctx;
 138
 139 #ifdef SCMP_ACT_KILL_PROCESS
 140     ctx = seccomp_init(SCMP_ACT_KILL_PROCESS);
 141     /* Handle a newer libseccomp but an older kernel */
 142     if (!ctx && errno == EOPNOTSUPP) {
 143         ctx = seccomp_init(SCMP_ACT_TRAP);
 144     }
 145 #else
 146     ctx = seccomp_init(SCMP_ACT_TRAP);
 147 #endif
 148     if (!ctx) {
 149         fuse_log(FUSE_LOG_ERR, "seccomp_init() failed\n");
 150         exit(1);
 151     }
 152
 153     add_whitelist(ctx, syscall_whitelist, G_N_ELEMENTS(syscall_whitelist));
 154     if (enable_syslog) {
 155         add_whitelist(ctx, syscall_whitelist_syslog,
 156                       G_N_ELEMENTS(syscall_whitelist_syslog));
 157     }
 158
 159     /* libvhost-user calls this for post-copy migration, we don't need it */
 160     if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOSYS),
 161                          SCMP_SYS(userfaultfd), 0) != 0) {
 162         fuse_log(FUSE_LOG_ERR, "seccomp_rule_add userfaultfd failed\n");
 163         exit(1);
 164     }
 165
 166     if (seccomp_load(ctx) < 0) {
 167         fuse_log(FUSE_LOG_ERR, "seccomp_load() failed\n");
 168         exit(1);
 169     }
 170
 171     seccomp_release(ctx);
 172 }