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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <linux/netlink.h>
#include <sys/capability.h>
#include <sys/socket.h>
#include <sys/types.h>
#include "alloc-util.h"
#include "log.h"
#include "nspawn-seccomp.h"
#include "seccomp-util.h"
#include "string-util.h"
#include "strv.h"
#if HAVE_SECCOMP
static int add_syscall_filters(
scmp_filter_ctx ctx,
uint32_t arch,
uint64_t cap_list_retain,
char **syscall_allow_list,
char **syscall_deny_list) {
static const struct {
uint64_t capability;
const char* name;
} allow_list[] = {
/* Let's use set names where we can */
{ 0, "@aio" },
{ 0, "@basic-io" },
{ 0, "@chown" },
{ 0, "@default" },
{ 0, "@file-system" },
{ 0, "@io-event" },
{ 0, "@ipc" },
{ 0, "@mount" },
{ 0, "@network-io" },
{ 0, "@process" },
{ 0, "@resources" },
{ 0, "@setuid" },
{ 0, "@signal" },
{ 0, "@sync" },
{ 0, "@timer" },
/* The following four are sets we optionally enable, n case the caps have been configured for it */
{ CAP_SYS_TIME, "@clock" },
{ CAP_SYS_MODULE, "@module" },
{ CAP_SYS_RAWIO, "@raw-io" },
{ CAP_IPC_LOCK, "@memlock" },
/* Plus a good set of additional syscalls which are not part of any of the groups above */
{ 0, "brk" },
{ 0, "capget" },
{ 0, "capset" },
{ 0, "copy_file_range" },
{ 0, "fadvise64" },
{ 0, "fadvise64_64" },
{ 0, "flock" },
{ 0, "get_mempolicy" },
{ 0, "getcpu" },
{ 0, "getpriority" },
{ 0, "getrandom" },
{ 0, "ioctl" },
{ 0, "ioprio_get" },
{ 0, "kcmp" },
{ 0, "madvise" },
{ 0, "mincore" },
{ 0, "mprotect" },
{ 0, "mremap" },
{ 0, "name_to_handle_at" },
{ 0, "oldolduname" },
{ 0, "olduname" },
{ 0, "personality" },
{ 0, "readahead" },
{ 0, "readdir" },
{ 0, "remap_file_pages" },
{ 0, "sched_get_priority_max" },
{ 0, "sched_get_priority_min" },
{ 0, "sched_getaffinity" },
{ 0, "sched_getattr" },
{ 0, "sched_getparam" },
{ 0, "sched_getscheduler" },
{ 0, "sched_rr_get_interval" },
{ 0, "sched_rr_get_interval_time64" },
{ 0, "sched_yield" },
{ 0, "seccomp" },
{ 0, "sendfile" },
{ 0, "sendfile64" },
{ 0, "setdomainname" },
{ 0, "setfsgid" },
{ 0, "setfsgid32" },
{ 0, "setfsuid" },
{ 0, "setfsuid32" },
{ 0, "sethostname" },
{ 0, "setpgid" },
{ 0, "setsid" },
{ 0, "splice" },
{ 0, "sysinfo" },
{ 0, "tee" },
{ 0, "umask" },
{ 0, "uname" },
{ 0, "userfaultfd" },
{ 0, "vmsplice" },
/* The following individual syscalls are added depending on specified caps */
{ CAP_SYS_PACCT, "acct" },
{ CAP_SYS_PTRACE, "process_vm_readv" },
{ CAP_SYS_PTRACE, "process_vm_writev" },
{ CAP_SYS_PTRACE, "ptrace" },
{ CAP_SYS_BOOT, "reboot" },
{ CAP_SYSLOG, "syslog" },
{ CAP_SYS_TTY_CONFIG, "vhangup" },
/*
* The following syscalls and groups are knowingly excluded:
*
* @cpu-emulation
* @keyring (NB: keyring is not namespaced!)
* @obsolete
* @pkey
* @swap
*
* bpf
* fanotify_init
* fanotify_mark
* kexec_file_load
* kexec_load
* lookup_dcookie
* nfsservctl
* open_by_handle_at
* perf_event_open
* quotactl
*/
};
_cleanup_strv_free_ char **added = NULL;
int r;
for (size_t i = 0; i < ELEMENTSOF(allow_list); i++) {
if (allow_list[i].capability != 0 && (cap_list_retain & (1ULL << allow_list[i].capability)) == 0)
continue;
r = seccomp_add_syscall_filter_item(ctx,
allow_list[i].name,
SCMP_ACT_ALLOW,
syscall_deny_list,
false,
&added);
if (r < 0)
return log_error_errno(r, "Failed to add syscall filter item %s: %m", allow_list[i].name);
}
STRV_FOREACH(p, syscall_allow_list) {
r = seccomp_add_syscall_filter_item(ctx, *p, SCMP_ACT_ALLOW, syscall_deny_list, true, &added);
if (r < 0)
log_warning_errno(r, "Failed to add rule for system call %s on %s, ignoring: %m",
*p, seccomp_arch_to_string(arch));
}
/* The default action is ENOSYS. Respond with EPERM to all other "known" but not allow-listed
* syscalls. */
r = seccomp_add_syscall_filter_item(ctx, "@known", SCMP_ACT_ERRNO(EPERM), added, true, NULL);
if (r < 0)
log_warning_errno(r, "Failed to add rule for @known set on %s, ignoring: %m",
seccomp_arch_to_string(arch));
#if (SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR >= 5) || SCMP_VER_MAJOR > 2
/* We have a large filter here, so let's turn on the binary tree mode if possible. */
r = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_OPTIMIZE, 2);
if (r < 0)
log_warning_errno(r, "Failed to set SCMP_FLTATR_CTL_OPTIMIZE, ignoring: %m");
#endif
return 0;
}
int setup_seccomp(uint64_t cap_list_retain, char **syscall_allow_list, char **syscall_deny_list) {
uint32_t arch;
int r;
if (!is_seccomp_available()) {
log_debug("SECCOMP features not detected in the kernel or disabled at runtime, disabling SECCOMP filtering");
return 0;
}
SECCOMP_FOREACH_LOCAL_ARCH(arch) {
_cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
log_debug("Applying allow list on architecture: %s", seccomp_arch_to_string(arch));
/* We install ENOSYS as the default action, but it will only apply to syscalls which are not
* in the @known set, see above. */
r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ERRNO(ENOSYS));
if (r < 0)
return log_error_errno(r, "Failed to allocate seccomp object: %m");
r = add_syscall_filters(seccomp, arch, cap_list_retain, syscall_allow_list, syscall_deny_list);
if (r < 0)
return r;
r = seccomp_load(seccomp);
if (ERRNO_IS_NEG_SECCOMP_FATAL(r))
return log_error_errno(r, "Failed to install seccomp filter: %m");
if (r < 0)
log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m",
seccomp_arch_to_string(arch));
}
SECCOMP_FOREACH_LOCAL_ARCH(arch) {
_cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
log_debug("Applying NETLINK_AUDIT mask on architecture: %s", seccomp_arch_to_string(arch));
r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
if (r < 0)
return log_error_errno(r, "Failed to allocate seccomp object: %m");
/*
Audit is broken in containers, much of the userspace audit hookup will fail if running inside a
container. We don't care and just turn off creation of audit sockets.
This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail with EAFNOSUPPORT which audit userspace uses
as indication that audit is disabled in the kernel.
*/
r = seccomp_rule_add_exact(
seccomp,
SCMP_ACT_ERRNO(EAFNOSUPPORT),
SCMP_SYS(socket),
2,
SCMP_A0(SCMP_CMP_EQ, AF_NETLINK),
SCMP_A2(SCMP_CMP_EQ, NETLINK_AUDIT));
if (r < 0) {
log_debug_errno(r, "Failed to add audit seccomp rule, ignoring: %m");
continue;
}
r = seccomp_load(seccomp);
if (ERRNO_IS_NEG_SECCOMP_FATAL(r))
return log_error_errno(r, "Failed to install seccomp audit filter: %m");
if (r < 0)
log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m",
seccomp_arch_to_string(arch));
}
return 0;
}
#else
int setup_seccomp(uint64_t cap_list_retain, char **syscall_allow_list, char **syscall_deny_list) {
return 0;
}
#endif
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