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 <seccomp.h>
  14
  15 /* Bodge for libseccomp 2.4.2 which broke ppoll */
  16 #if !defined(__SNR_ppoll) && defined(__SNR_brk)
  17 #ifdef __NR_ppoll
  18 #define __SNR_ppoll __NR_ppoll
  19 #else
  20 #define __SNR_ppoll __PNR_ppoll
  21 #endif
  22 #endif
  23
  24 static const int syscall_allowlist[] = {
  25     /* TODO ireg sem*() syscalls */
  26     SCMP_SYS(brk),
  27     SCMP_SYS(capget), /* For CAP_FSETID */
  28     SCMP_SYS(capset),
  29     SCMP_SYS(clock_gettime),
  30     SCMP_SYS(clone),
  31 #ifdef __NR_clone3
  32     SCMP_SYS(clone3),
  33 #endif
  34     SCMP_SYS(close),
  35     SCMP_SYS(copy_file_range),
  36     SCMP_SYS(dup),
  37     SCMP_SYS(eventfd2),
  38     SCMP_SYS(exit),
  39     SCMP_SYS(exit_group),
  40     SCMP_SYS(fallocate),
  41     SCMP_SYS(fchdir),
  42     SCMP_SYS(fchmod),
  43     SCMP_SYS(fchmodat),
  44     SCMP_SYS(fchownat),
  45     SCMP_SYS(fcntl),
  46     SCMP_SYS(fdatasync),
  47     SCMP_SYS(fgetxattr),
  48     SCMP_SYS(flistxattr),
  49     SCMP_SYS(flock),
  50     SCMP_SYS(fremovexattr),
  51     SCMP_SYS(fsetxattr),
  52     SCMP_SYS(fstat),
  53     SCMP_SYS(fstatfs),
  54     SCMP_SYS(fsync),
  55     SCMP_SYS(ftruncate),
  56     SCMP_SYS(futex),
  57     SCMP_SYS(getdents),
  58     SCMP_SYS(getdents64),
  59     SCMP_SYS(getegid),
  60     SCMP_SYS(geteuid),
  61     SCMP_SYS(getpid),
  62     SCMP_SYS(gettid),
  63     SCMP_SYS(gettimeofday),
  64     SCMP_SYS(getxattr),
  65     SCMP_SYS(linkat),
  66     SCMP_SYS(listxattr),
  67     SCMP_SYS(lseek),
  68     SCMP_SYS(_llseek), /* For POWER */
  69     SCMP_SYS(madvise),
  70     SCMP_SYS(mkdirat),
  71     SCMP_SYS(mknodat),
  72     SCMP_SYS(mmap),
  73     SCMP_SYS(mprotect),
  74     SCMP_SYS(mremap),
  75     SCMP_SYS(munmap),
  76     SCMP_SYS(newfstatat),
  77     SCMP_SYS(statx),
  78     SCMP_SYS(open),
  79     SCMP_SYS(openat),
  80     SCMP_SYS(ppoll),
  81     SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */
  82     SCMP_SYS(preadv),
  83     SCMP_SYS(pread64),
  84     SCMP_SYS(pwritev),
  85     SCMP_SYS(pwrite64),
  86     SCMP_SYS(read),
  87     SCMP_SYS(readlinkat),
  88     SCMP_SYS(recvmsg),
  89     SCMP_SYS(renameat),
  90     SCMP_SYS(renameat2),
  91     SCMP_SYS(removexattr),
  92     SCMP_SYS(restart_syscall),
  93     SCMP_SYS(rt_sigaction),
  94     SCMP_SYS(rt_sigprocmask),
  95     SCMP_SYS(rt_sigreturn),
  96     SCMP_SYS(sched_getattr),
  97     SCMP_SYS(sched_setattr),
  98     SCMP_SYS(sendmsg),
  99     SCMP_SYS(setresgid),
 100     SCMP_SYS(setresuid),
 101 #ifdef __NR_setresgid32
 102     SCMP_SYS(setresgid32),
 103 #endif
 104 #ifdef __NR_setresuid32
 105     SCMP_SYS(setresuid32),
 106 #endif
 107     SCMP_SYS(set_robust_list),
 108     SCMP_SYS(setxattr),
 109     SCMP_SYS(symlinkat),
 110     SCMP_SYS(time), /* Rarely needed, except on static builds */
 111     SCMP_SYS(tgkill),
 112     SCMP_SYS(unlinkat),
 113     SCMP_SYS(unshare),
 114     SCMP_SYS(utimensat),
 115     SCMP_SYS(write),
 116     SCMP_SYS(writev),
 117 };
 118
 119 /* Syscalls used when --syslog is enabled */
 120 static const int syscall_allowlist_syslog[] = {
 121     SCMP_SYS(send),
 122     SCMP_SYS(sendto),
 123 };
 124
 125 static void add_allowlist(scmp_filter_ctx ctx, const int syscalls[], size_t len)
 126 {
 127     size_t i;
 128
 129     for (i = 0; i < len; i++) {
 130         if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, syscalls[i], 0) != 0) {
 131             fuse_log(FUSE_LOG_ERR, "seccomp_rule_add syscall %d failed\n",
 132                      syscalls[i]);
 133             exit(1);
 134         }
 135     }
 136 }
 137
 138 void setup_seccomp(bool enable_syslog)
 139 {
 140     scmp_filter_ctx ctx;
 141
 142 #ifdef SCMP_ACT_KILL_PROCESS
 143     ctx = seccomp_init(SCMP_ACT_KILL_PROCESS);
 144     /* Handle a newer libseccomp but an older kernel */
 145     if (!ctx && errno == EOPNOTSUPP) {
 146         ctx = seccomp_init(SCMP_ACT_TRAP);
 147     }
 148 #else
 149     ctx = seccomp_init(SCMP_ACT_TRAP);
 150 #endif
 151     if (!ctx) {
 152         fuse_log(FUSE_LOG_ERR, "seccomp_init() failed\n");
 153         exit(1);
 154     }
 155
 156     add_allowlist(ctx, syscall_allowlist, G_N_ELEMENTS(syscall_allowlist));
 157     if (enable_syslog) {
 158         add_allowlist(ctx, syscall_allowlist_syslog,
 159                       G_N_ELEMENTS(syscall_allowlist_syslog));
 160     }
 161
 162     /* libvhost-user calls this for post-copy migration, we don't need it */
 163     if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOSYS),
 164                          SCMP_SYS(userfaultfd), 0) != 0) {
 165         fuse_log(FUSE_LOG_ERR, "seccomp_rule_add userfaultfd failed\n");
 166         exit(1);
 167     }
 168
 169     if (seccomp_load(ctx) < 0) {
 170         fuse_log(FUSE_LOG_ERR, "seccomp_load() failed\n");
 171         exit(1);
 172     }
 173
 174     seccomp_release(ctx);
 175 }