tools/virtiofsd/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 "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(fchmodat),
  45     SCMP_SYS(fchownat),
  46     SCMP_SYS(fcntl),
  47     SCMP_SYS(fdatasync),
  48     SCMP_SYS(fgetxattr),
  49     SCMP_SYS(flistxattr),
  50     SCMP_SYS(flock),
  51     SCMP_SYS(fremovexattr),
  52     SCMP_SYS(fsetxattr),
  53     SCMP_SYS(fstat),
  54     SCMP_SYS(fstatfs),
  55     SCMP_SYS(fsync),
  56     SCMP_SYS(ftruncate),
  57     SCMP_SYS(futex),
  58     SCMP_SYS(getdents),
  59     SCMP_SYS(getdents64),
  60     SCMP_SYS(getegid),
  61     SCMP_SYS(geteuid),
  62     SCMP_SYS(getpid),
  63     SCMP_SYS(gettid),
  64     SCMP_SYS(gettimeofday),
  65     SCMP_SYS(linkat),
  66     SCMP_SYS(lseek),
  67     SCMP_SYS(madvise),
  68     SCMP_SYS(mkdirat),
  69     SCMP_SYS(mknodat),
  70     SCMP_SYS(mmap),
  71     SCMP_SYS(mprotect),
  72     SCMP_SYS(mremap),
  73     SCMP_SYS(munmap),
  74     SCMP_SYS(newfstatat),
  75     SCMP_SYS(open),
  76     SCMP_SYS(openat),
  77     SCMP_SYS(ppoll),
  78     SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */
  79     SCMP_SYS(preadv),
  80     SCMP_SYS(pread64),
  81     SCMP_SYS(pwritev),
  82     SCMP_SYS(pwrite64),
  83     SCMP_SYS(read),
  84     SCMP_SYS(readlinkat),
  85     SCMP_SYS(recvmsg),
  86     SCMP_SYS(renameat),
  87     SCMP_SYS(renameat2),
  88     SCMP_SYS(rt_sigaction),
  89     SCMP_SYS(rt_sigprocmask),
  90     SCMP_SYS(rt_sigreturn),
  91     SCMP_SYS(sendmsg),
  92     SCMP_SYS(setresgid),
  93     SCMP_SYS(setresuid),
  94 #ifdef __NR_setresgid32
  95     SCMP_SYS(setresgid32),
  96 #endif
  97 #ifdef __NR_setresuid32
  98     SCMP_SYS(setresuid32),
  99 #endif
 100     SCMP_SYS(set_robust_list),
 101     SCMP_SYS(symlinkat),
 102     SCMP_SYS(time), /* Rarely needed, except on static builds */
 103     SCMP_SYS(tgkill),
 104     SCMP_SYS(unlinkat),
 105     SCMP_SYS(utimensat),
 106     SCMP_SYS(write),
 107     SCMP_SYS(writev),
 108 };
 109
 110 /* Syscalls used when --syslog is enabled */
 111 static const int syscall_whitelist_syslog[] = {
 112     SCMP_SYS(sendto),
 113 };
 114
 115 static void add_whitelist(scmp_filter_ctx ctx, const int syscalls[], size_t len)
 116 {
 117     size_t i;
 118
 119     for (i = 0; i < len; i++) {
 120         if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, syscalls[i], 0) != 0) {
 121             fuse_log(FUSE_LOG_ERR, "seccomp_rule_add syscall %d failed\n",
 122                      syscalls[i]);
 123             exit(1);
 124         }
 125     }
 126 }
 127
 128 void setup_seccomp(bool enable_syslog)
 129 {
 130     scmp_filter_ctx ctx;
 131
 132 #ifdef SCMP_ACT_KILL_PROCESS
 133     ctx = seccomp_init(SCMP_ACT_KILL_PROCESS);
 134     /* Handle a newer libseccomp but an older kernel */
 135     if (!ctx && errno == EOPNOTSUPP) {
 136         ctx = seccomp_init(SCMP_ACT_TRAP);
 137     }
 138 #else
 139     ctx = seccomp_init(SCMP_ACT_TRAP);
 140 #endif
 141     if (!ctx) {
 142         fuse_log(FUSE_LOG_ERR, "seccomp_init() failed\n");
 143         exit(1);
 144     }
 145
 146     add_whitelist(ctx, syscall_whitelist, G_N_ELEMENTS(syscall_whitelist));
 147     if (enable_syslog) {
 148         add_whitelist(ctx, syscall_whitelist_syslog,
 149                       G_N_ELEMENTS(syscall_whitelist_syslog));
 150     }
 151
 152     /* libvhost-user calls this for post-copy migration, we don't need it */
 153     if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOSYS),
 154                          SCMP_SYS(userfaultfd), 0) != 0) {
 155         fuse_log(FUSE_LOG_ERR, "seccomp_rule_add userfaultfd failed\n");
 156         exit(1);
 157     }
 158
 159     if (seccomp_load(ctx) < 0) {
 160         fuse_log(FUSE_LOG_ERR, "seccomp_load() failed\n");
 161         exit(1);
 162     }
 163
 164     seccomp_release(ctx);
 165 }