qemu/qemu-seccomp.c
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   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
  34struct QemuSeccompSyscall {
  35    int32_t num;
  36    uint8_t set;
  37    uint8_t narg;
  38    const struct scmp_arg_cmp *arg_cmp;
  39};
  40
  41const struct scmp_arg_cmp sched_setscheduler_arg[] = {
  42    SCMP_A1(SCMP_CMP_NE, SCHED_IDLE)
  43};
  44
  45static const struct QemuSeccompSyscall blacklist[] = {
  46    /* default set of syscalls to blacklist */
  47    { SCMP_SYS(reboot),                 QEMU_SECCOMP_SET_DEFAULT },
  48    { SCMP_SYS(swapon),                 QEMU_SECCOMP_SET_DEFAULT },
  49    { SCMP_SYS(swapoff),                QEMU_SECCOMP_SET_DEFAULT },
  50    { SCMP_SYS(syslog),                 QEMU_SECCOMP_SET_DEFAULT },
  51    { SCMP_SYS(mount),                  QEMU_SECCOMP_SET_DEFAULT },
  52    { SCMP_SYS(umount),                 QEMU_SECCOMP_SET_DEFAULT },
  53    { SCMP_SYS(kexec_load),             QEMU_SECCOMP_SET_DEFAULT },
  54    { SCMP_SYS(afs_syscall),            QEMU_SECCOMP_SET_DEFAULT },
  55    { SCMP_SYS(break),                  QEMU_SECCOMP_SET_DEFAULT },
  56    { SCMP_SYS(ftime),                  QEMU_SECCOMP_SET_DEFAULT },
  57    { SCMP_SYS(getpmsg),                QEMU_SECCOMP_SET_DEFAULT },
  58    { SCMP_SYS(gtty),                   QEMU_SECCOMP_SET_DEFAULT },
  59    { SCMP_SYS(lock),                   QEMU_SECCOMP_SET_DEFAULT },
  60    { SCMP_SYS(mpx),                    QEMU_SECCOMP_SET_DEFAULT },
  61    { SCMP_SYS(prof),                   QEMU_SECCOMP_SET_DEFAULT },
  62    { SCMP_SYS(profil),                 QEMU_SECCOMP_SET_DEFAULT },
  63    { SCMP_SYS(putpmsg),                QEMU_SECCOMP_SET_DEFAULT },
  64    { SCMP_SYS(security),               QEMU_SECCOMP_SET_DEFAULT },
  65    { SCMP_SYS(stty),                   QEMU_SECCOMP_SET_DEFAULT },
  66    { SCMP_SYS(tuxcall),                QEMU_SECCOMP_SET_DEFAULT },
  67    { SCMP_SYS(ulimit),                 QEMU_SECCOMP_SET_DEFAULT },
  68    { SCMP_SYS(vserver),                QEMU_SECCOMP_SET_DEFAULT },
  69    /* obsolete */
  70    { SCMP_SYS(readdir),                QEMU_SECCOMP_SET_OBSOLETE },
  71    { SCMP_SYS(_sysctl),                QEMU_SECCOMP_SET_OBSOLETE },
  72    { SCMP_SYS(bdflush),                QEMU_SECCOMP_SET_OBSOLETE },
  73    { SCMP_SYS(create_module),          QEMU_SECCOMP_SET_OBSOLETE },
  74    { SCMP_SYS(get_kernel_syms),        QEMU_SECCOMP_SET_OBSOLETE },
  75    { SCMP_SYS(query_module),           QEMU_SECCOMP_SET_OBSOLETE },
  76    { SCMP_SYS(sgetmask),               QEMU_SECCOMP_SET_OBSOLETE },
  77    { SCMP_SYS(ssetmask),               QEMU_SECCOMP_SET_OBSOLETE },
  78    { SCMP_SYS(sysfs),                  QEMU_SECCOMP_SET_OBSOLETE },
  79    { SCMP_SYS(uselib),                 QEMU_SECCOMP_SET_OBSOLETE },
  80    { SCMP_SYS(ustat),                  QEMU_SECCOMP_SET_OBSOLETE },
  81    /* privileged */
  82    { SCMP_SYS(setuid),                 QEMU_SECCOMP_SET_PRIVILEGED },
  83    { SCMP_SYS(setgid),                 QEMU_SECCOMP_SET_PRIVILEGED },
  84    { SCMP_SYS(setpgid),                QEMU_SECCOMP_SET_PRIVILEGED },
  85    { SCMP_SYS(setsid),                 QEMU_SECCOMP_SET_PRIVILEGED },
  86    { SCMP_SYS(setreuid),               QEMU_SECCOMP_SET_PRIVILEGED },
  87    { SCMP_SYS(setregid),               QEMU_SECCOMP_SET_PRIVILEGED },
  88    { SCMP_SYS(setresuid),              QEMU_SECCOMP_SET_PRIVILEGED },
  89    { SCMP_SYS(setresgid),              QEMU_SECCOMP_SET_PRIVILEGED },
  90    { SCMP_SYS(setfsuid),               QEMU_SECCOMP_SET_PRIVILEGED },
  91    { SCMP_SYS(setfsgid),               QEMU_SECCOMP_SET_PRIVILEGED },
  92    /* spawn */
  93    { SCMP_SYS(fork),                   QEMU_SECCOMP_SET_SPAWN },
  94    { SCMP_SYS(vfork),                  QEMU_SECCOMP_SET_SPAWN },
  95    { SCMP_SYS(execve),                 QEMU_SECCOMP_SET_SPAWN },
  96    /* resource control */
  97    { SCMP_SYS(getpriority),            QEMU_SECCOMP_SET_RESOURCECTL },
  98    { SCMP_SYS(setpriority),            QEMU_SECCOMP_SET_RESOURCECTL },
  99    { SCMP_SYS(sched_setparam),         QEMU_SECCOMP_SET_RESOURCECTL },
 100    { SCMP_SYS(sched_getparam),         QEMU_SECCOMP_SET_RESOURCECTL },
 101    { SCMP_SYS(sched_setscheduler),     QEMU_SECCOMP_SET_RESOURCECTL,
 102      ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg },
 103    { SCMP_SYS(sched_getscheduler),     QEMU_SECCOMP_SET_RESOURCECTL },
 104    { SCMP_SYS(sched_setaffinity),      QEMU_SECCOMP_SET_RESOURCECTL },
 105    { SCMP_SYS(sched_getaffinity),      QEMU_SECCOMP_SET_RESOURCECTL },
 106    { SCMP_SYS(sched_get_priority_max), QEMU_SECCOMP_SET_RESOURCECTL },
 107    { SCMP_SYS(sched_get_priority_min), QEMU_SECCOMP_SET_RESOURCECTL },
 108};
 109
 110
 111static int seccomp_start(uint32_t seccomp_opts)
 112{
 113    int rc = 0;
 114    unsigned int i = 0;
 115    scmp_filter_ctx ctx;
 116
 117    ctx = seccomp_init(SCMP_ACT_ALLOW);
 118    if (ctx == NULL) {
 119        rc = -1;
 120        goto seccomp_return;
 121    }
 122
 123    for (i = 0; i < ARRAY_SIZE(blacklist); i++) {
 124        if (!(seccomp_opts & blacklist[i].set)) {
 125            continue;
 126        }
 127
 128        rc = seccomp_rule_add_array(ctx, SCMP_ACT_KILL, blacklist[i].num,
 129                                    blacklist[i].narg, blacklist[i].arg_cmp);
 130        if (rc < 0) {
 131            goto seccomp_return;
 132        }
 133    }
 134
 135    rc = seccomp_load(ctx);
 136
 137  seccomp_return:
 138    seccomp_release(ctx);
 139    return rc;
 140}
 141
 142#ifdef CONFIG_SECCOMP
 143int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp)
 144{
 145    if (qemu_opt_get_bool(opts, "enable", false)) {
 146        uint32_t seccomp_opts = QEMU_SECCOMP_SET_DEFAULT
 147                | QEMU_SECCOMP_SET_OBSOLETE;
 148        const char *value = NULL;
 149
 150        value = qemu_opt_get(opts, "obsolete");
 151        if (value) {
 152            if (g_str_equal(value, "allow")) {
 153                seccomp_opts &= ~QEMU_SECCOMP_SET_OBSOLETE;
 154            } else if (g_str_equal(value, "deny")) {
 155                /* this is the default option, this if is here
 156                 * to provide a little bit of consistency for
 157                 * the command line */
 158            } else {
 159                error_report("invalid argument for obsolete");
 160                return -1;
 161            }
 162        }
 163
 164        value = qemu_opt_get(opts, "elevateprivileges");
 165        if (value) {
 166            if (g_str_equal(value, "deny")) {
 167                seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
 168            } else if (g_str_equal(value, "children")) {
 169                seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
 170
 171                /* calling prctl directly because we're
 172                 * not sure if host has CAP_SYS_ADMIN set*/
 173                if (prctl(PR_SET_NO_NEW_PRIVS, 1)) {
 174                    error_report("failed to set no_new_privs "
 175                                 "aborting");
 176                    return -1;
 177                }
 178            } else if (g_str_equal(value, "allow")) {
 179                /* default value */
 180            } else {
 181                error_report("invalid argument for elevateprivileges");
 182                return -1;
 183            }
 184        }
 185
 186        value = qemu_opt_get(opts, "spawn");
 187        if (value) {
 188            if (g_str_equal(value, "deny")) {
 189                seccomp_opts |= QEMU_SECCOMP_SET_SPAWN;
 190            } else if (g_str_equal(value, "allow")) {
 191                /* default value */
 192            } else {
 193                error_report("invalid argument for spawn");
 194                return -1;
 195            }
 196        }
 197
 198        value = qemu_opt_get(opts, "resourcecontrol");
 199        if (value) {
 200            if (g_str_equal(value, "deny")) {
 201                seccomp_opts |= QEMU_SECCOMP_SET_RESOURCECTL;
 202            } else if (g_str_equal(value, "allow")) {
 203                /* default value */
 204            } else {
 205                error_report("invalid argument for resourcecontrol");
 206                return -1;
 207            }
 208        }
 209
 210        if (seccomp_start(seccomp_opts) < 0) {
 211            error_report("failed to install seccomp syscall filter "
 212                         "in the kernel");
 213            return -1;
 214        }
 215    }
 216
 217    return 0;
 218}
 219
 220static QemuOptsList qemu_sandbox_opts = {
 221    .name = "sandbox",
 222    .implied_opt_name = "enable",
 223    .head = QTAILQ_HEAD_INITIALIZER(qemu_sandbox_opts.head),
 224    .desc = {
 225        {
 226            .name = "enable",
 227            .type = QEMU_OPT_BOOL,
 228        },
 229        {
 230            .name = "obsolete",
 231            .type = QEMU_OPT_STRING,
 232        },
 233        {
 234            .name = "elevateprivileges",
 235            .type = QEMU_OPT_STRING,
 236        },
 237        {
 238            .name = "spawn",
 239            .type = QEMU_OPT_STRING,
 240        },
 241        {
 242            .name = "resourcecontrol",
 243            .type = QEMU_OPT_STRING,
 244        },
 245        { /* end of list */ }
 246    },
 247};
 248
 249static void seccomp_register(void)
 250{
 251    qemu_add_opts(&qemu_sandbox_opts);
 252}
 253opts_init(seccomp_register);
 254#endif
 255