qemu-seccomp.c

   1 /*
   2  * QEMU seccomp mode 2 support with libseccomp
   3  *
   4  * Copyright IBM, Corp. 2012
   5  *
   6  * Authors:
   7  *  Eduardo Otubo    <eotubo@br.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  * Contributions after 2012-01-13 are licensed under the terms of the
  13  * GNU GPL, version 2 or (at your option) any later version.
  14  */
  15 #include "qemu/osdep.h"
  16 #include "qemu/config-file.h"
  17 #include "qemu/option.h"
  18 #include "qemu/module.h"
  19 #include "qemu/error-report.h"
  20 #include <sys/prctl.h>
  21 #include <seccomp.h>
  22 #include "sysemu/seccomp.h"
  23
  24 /* For some architectures (notably ARM) cacheflush is not supported until
  25  * libseccomp 2.2.3, but configure enforces that we are using a more recent
  26  * version on those hosts, so it is OK for this check to be less strict.
  27  */
  28 #if SCMP_VER_MAJOR >= 3
  29   #define HAVE_CACHEFLUSH
  30 #elif SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR >= 2
  31   #define HAVE_CACHEFLUSH
  32 #endif
  33
  34 struct QemuSeccompSyscall {
  35     int32_t num;
  36     uint8_t set;
  37 };
  38
  39 static const struct QemuSeccompSyscall blacklist[] = {
  40     /* default set of syscalls to blacklist */
  41     { SCMP_SYS(reboot),                 QEMU_SECCOMP_SET_DEFAULT },
  42     { SCMP_SYS(swapon),                 QEMU_SECCOMP_SET_DEFAULT },
  43     { SCMP_SYS(swapoff),                QEMU_SECCOMP_SET_DEFAULT },
  44     { SCMP_SYS(syslog),                 QEMU_SECCOMP_SET_DEFAULT },
  45     { SCMP_SYS(mount),                  QEMU_SECCOMP_SET_DEFAULT },
  46     { SCMP_SYS(umount),                 QEMU_SECCOMP_SET_DEFAULT },
  47     { SCMP_SYS(kexec_load),             QEMU_SECCOMP_SET_DEFAULT },
  48     { SCMP_SYS(afs_syscall),            QEMU_SECCOMP_SET_DEFAULT },
  49     { SCMP_SYS(break),                  QEMU_SECCOMP_SET_DEFAULT },
  50     { SCMP_SYS(ftime),                  QEMU_SECCOMP_SET_DEFAULT },
  51     { SCMP_SYS(getpmsg),                QEMU_SECCOMP_SET_DEFAULT },
  52     { SCMP_SYS(gtty),                   QEMU_SECCOMP_SET_DEFAULT },
  53     { SCMP_SYS(lock),                   QEMU_SECCOMP_SET_DEFAULT },
  54     { SCMP_SYS(mpx),                    QEMU_SECCOMP_SET_DEFAULT },
  55     { SCMP_SYS(prof),                   QEMU_SECCOMP_SET_DEFAULT },
  56     { SCMP_SYS(profil),                 QEMU_SECCOMP_SET_DEFAULT },
  57     { SCMP_SYS(putpmsg),                QEMU_SECCOMP_SET_DEFAULT },
  58     { SCMP_SYS(security),               QEMU_SECCOMP_SET_DEFAULT },
  59     { SCMP_SYS(stty),                   QEMU_SECCOMP_SET_DEFAULT },
  60     { SCMP_SYS(tuxcall),                QEMU_SECCOMP_SET_DEFAULT },
  61     { SCMP_SYS(ulimit),                 QEMU_SECCOMP_SET_DEFAULT },
  62     { SCMP_SYS(vserver),                QEMU_SECCOMP_SET_DEFAULT },
  63     /* obsolete */
  64     { SCMP_SYS(readdir),                QEMU_SECCOMP_SET_OBSOLETE },
  65     { SCMP_SYS(_sysctl),                QEMU_SECCOMP_SET_OBSOLETE },
  66     { SCMP_SYS(bdflush),                QEMU_SECCOMP_SET_OBSOLETE },
  67     { SCMP_SYS(create_module),          QEMU_SECCOMP_SET_OBSOLETE },
  68     { SCMP_SYS(get_kernel_syms),        QEMU_SECCOMP_SET_OBSOLETE },
  69     { SCMP_SYS(query_module),           QEMU_SECCOMP_SET_OBSOLETE },
  70     { SCMP_SYS(sgetmask),               QEMU_SECCOMP_SET_OBSOLETE },
  71     { SCMP_SYS(ssetmask),               QEMU_SECCOMP_SET_OBSOLETE },
  72     { SCMP_SYS(sysfs),                  QEMU_SECCOMP_SET_OBSOLETE },
  73     { SCMP_SYS(uselib),                 QEMU_SECCOMP_SET_OBSOLETE },
  74     { SCMP_SYS(ustat),                  QEMU_SECCOMP_SET_OBSOLETE },
  75     /* privileged */
  76     { SCMP_SYS(setuid),                 QEMU_SECCOMP_SET_PRIVILEGED },
  77     { SCMP_SYS(setgid),                 QEMU_SECCOMP_SET_PRIVILEGED },
  78     { SCMP_SYS(setpgid),                QEMU_SECCOMP_SET_PRIVILEGED },
  79     { SCMP_SYS(setsid),                 QEMU_SECCOMP_SET_PRIVILEGED },
  80     { SCMP_SYS(setreuid),               QEMU_SECCOMP_SET_PRIVILEGED },
  81     { SCMP_SYS(setregid),               QEMU_SECCOMP_SET_PRIVILEGED },
  82     { SCMP_SYS(setresuid),              QEMU_SECCOMP_SET_PRIVILEGED },
  83     { SCMP_SYS(setresgid),              QEMU_SECCOMP_SET_PRIVILEGED },
  84     { SCMP_SYS(setfsuid),               QEMU_SECCOMP_SET_PRIVILEGED },
  85     { SCMP_SYS(setfsgid),               QEMU_SECCOMP_SET_PRIVILEGED },
  86     /* spawn */
  87     { SCMP_SYS(fork),                   QEMU_SECCOMP_SET_SPAWN },
  88     { SCMP_SYS(vfork),                  QEMU_SECCOMP_SET_SPAWN },
  89     { SCMP_SYS(execve),                 QEMU_SECCOMP_SET_SPAWN },
  90     /* resource control */
  91     { SCMP_SYS(getpriority),            QEMU_SECCOMP_SET_RESOURCECTL },
  92     { SCMP_SYS(setpriority),            QEMU_SECCOMP_SET_RESOURCECTL },
  93     { SCMP_SYS(sched_setparam),         QEMU_SECCOMP_SET_RESOURCECTL },
  94     { SCMP_SYS(sched_getparam),         QEMU_SECCOMP_SET_RESOURCECTL },
  95     { SCMP_SYS(sched_setscheduler),     QEMU_SECCOMP_SET_RESOURCECTL },
  96     { SCMP_SYS(sched_getscheduler),     QEMU_SECCOMP_SET_RESOURCECTL },
  97     { SCMP_SYS(sched_setaffinity),      QEMU_SECCOMP_SET_RESOURCECTL },
  98     { SCMP_SYS(sched_getaffinity),      QEMU_SECCOMP_SET_RESOURCECTL },
  99     { SCMP_SYS(sched_get_priority_max), QEMU_SECCOMP_SET_RESOURCECTL },
 100     { SCMP_SYS(sched_get_priority_min), QEMU_SECCOMP_SET_RESOURCECTL },
 101 };
 102
 103
 104 static int seccomp_start(uint32_t seccomp_opts)
 105 {
 106     int rc = 0;
 107     unsigned int i = 0;
 108     scmp_filter_ctx ctx;
 109
 110     ctx = seccomp_init(SCMP_ACT_ALLOW);
 111     if (ctx == NULL) {
 112         rc = -1;
 113         goto seccomp_return;
 114     }
 115
 116     for (i = 0; i < ARRAY_SIZE(blacklist); i++) {
 117         if (!(seccomp_opts & blacklist[i].set)) {
 118             continue;
 119         }
 120
 121         rc = seccomp_rule_add(ctx, SCMP_ACT_KILL, blacklist[i].num, 0);
 122         if (rc < 0) {
 123             goto seccomp_return;
 124         }
 125     }
 126
 127     rc = seccomp_load(ctx);
 128
 129   seccomp_return:
 130     seccomp_release(ctx);
 131     return rc;
 132 }
 133
 134 #ifdef CONFIG_SECCOMP
 135 int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp)
 136 {
 137     if (qemu_opt_get_bool(opts, "enable", false)) {
 138         uint32_t seccomp_opts = QEMU_SECCOMP_SET_DEFAULT
 139                 | QEMU_SECCOMP_SET_OBSOLETE;
 140         const char *value = NULL;
 141
 142         value = qemu_opt_get(opts, "obsolete");
 143         if (value) {
 144             if (g_str_equal(value, "allow")) {
 145                 seccomp_opts &= ~QEMU_SECCOMP_SET_OBSOLETE;
 146             } else if (g_str_equal(value, "deny")) {
 147                 /* this is the default option, this if is here
 148                  * to provide a little bit of consistency for
 149                  * the command line */
 150             } else {
 151                 error_report("invalid argument for obsolete");
 152                 return -1;
 153             }
 154         }
 155
 156         value = qemu_opt_get(opts, "elevateprivileges");
 157         if (value) {
 158             if (g_str_equal(value, "deny")) {
 159                 seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
 160             } else if (g_str_equal(value, "children")) {
 161                 seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
 162
 163                 /* calling prctl directly because we're
 164                  * not sure if host has CAP_SYS_ADMIN set*/
 165                 if (prctl(PR_SET_NO_NEW_PRIVS, 1)) {
 166                     error_report("failed to set no_new_privs "
 167                                  "aborting");
 168                     return -1;
 169                 }
 170             } else if (g_str_equal(value, "allow")) {
 171                 /* default value */
 172             } else {
 173                 error_report("invalid argument for elevateprivileges");
 174                 return -1;
 175             }
 176         }
 177
 178         value = qemu_opt_get(opts, "spawn");
 179         if (value) {
 180             if (g_str_equal(value, "deny")) {
 181                 seccomp_opts |= QEMU_SECCOMP_SET_SPAWN;
 182             } else if (g_str_equal(value, "allow")) {
 183                 /* default value */
 184             } else {
 185                 error_report("invalid argument for spawn");
 186                 return -1;
 187             }
 188         }
 189
 190         value = qemu_opt_get(opts, "resourcecontrol");
 191         if (value) {
 192             if (g_str_equal(value, "deny")) {
 193                 seccomp_opts |= QEMU_SECCOMP_SET_RESOURCECTL;
 194             } else if (g_str_equal(value, "allow")) {
 195                 /* default value */
 196             } else {
 197                 error_report("invalid argument for resourcecontrol");
 198                 return -1;
 199             }
 200         }
 201
 202         if (seccomp_start(seccomp_opts) < 0) {
 203             error_report("failed to install seccomp syscall filter "
 204                          "in the kernel");
 205             return -1;
 206         }
 207     }
 208
 209     return 0;
 210 }
 211
 212 static QemuOptsList qemu_sandbox_opts = {
 213     .name = "sandbox",
 214     .implied_opt_name = "enable",
 215     .head = QTAILQ_HEAD_INITIALIZER(qemu_sandbox_opts.head),
 216     .desc = {
 217         {
 218             .name = "enable",
 219             .type = QEMU_OPT_BOOL,
 220         },
 221         {
 222             .name = "obsolete",
 223             .type = QEMU_OPT_STRING,
 224         },
 225         {
 226             .name = "elevateprivileges",
 227             .type = QEMU_OPT_STRING,
 228         },
 229         {
 230             .name = "spawn",
 231             .type = QEMU_OPT_STRING,
 232         },
 233         {
 234             .name = "resourcecontrol",
 235             .type = QEMU_OPT_STRING,
 236         },
 237         { /* end of list */ }
 238     },
 239 };
 240
 241 static void seccomp_register(void)
 242 {
 243     qemu_add_opts(&qemu_sandbox_opts);
 244 }
 245 opts_init(seccomp_register);
 246 #endif