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-rw-r--r--src/nspawn/nspawn-seccomp.c240
1 files changed, 240 insertions, 0 deletions
diff --git a/src/nspawn/nspawn-seccomp.c b/src/nspawn/nspawn-seccomp.c
new file mode 100644
index 0000000..e7ef80f
--- /dev/null
+++ b/src/nspawn/nspawn-seccomp.c
@@ -0,0 +1,240 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <linux/netlink.h>
+#include <sys/capability.h>
+#include <sys/types.h>
+
+#if HAVE_SECCOMP
+#include <seccomp.h>
+#endif
+
+#include "alloc-util.h"
+#include "log.h"
+#include "nspawn-seccomp.h"
+#if HAVE_SECCOMP
+#include "seccomp-util.h"
+#endif
+#include "string-util.h"
+#include "strv.h"
+
+#if HAVE_SECCOMP
+
+static int seccomp_add_default_syscall_filter(
+ scmp_filter_ctx ctx,
+ uint32_t arch,
+ uint64_t cap_list_retain,
+ char **syscall_whitelist,
+ char **syscall_blacklist) {
+
+ static const struct {
+ uint64_t capability;
+ const char* name;
+ } whitelist[] = {
+ /* 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, in 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_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
+ * @swap
+ *
+ * bpf (NB: bpffs is not namespaced!)
+ * fanotify_init
+ * fanotify_mark
+ * kexec_file_load
+ * kexec_load
+ * lookup_dcookie
+ * nfsservctl
+ * open_by_handle_at
+ * perf_event_open
+ * pkey_alloc
+ * pkey_free
+ * pkey_mprotect
+ * quotactl
+ */
+ };
+
+ int r;
+ size_t i;
+ char **p;
+
+ for (i = 0; i < ELEMENTSOF(whitelist); i++) {
+ if (whitelist[i].capability != 0 && (cap_list_retain & (1ULL << whitelist[i].capability)) == 0)
+ continue;
+
+ r = seccomp_add_syscall_filter_item(ctx, whitelist[i].name, SCMP_ACT_ALLOW, syscall_blacklist, false);
+ if (r < 0)
+ return log_error_errno(r, "Failed to add syscall filter item %s: %m", whitelist[i].name);
+ }
+
+ STRV_FOREACH(p, syscall_whitelist) {
+ r = seccomp_add_syscall_filter_item(ctx, *p, SCMP_ACT_ALLOW, syscall_blacklist, false);
+ 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));
+ }
+
+ return 0;
+}
+
+int setup_seccomp(uint64_t cap_list_retain, char **syscall_whitelist, char **syscall_blacklist) {
+ uint32_t arch;
+ int r;
+
+ if (!is_seccomp_available()) {
+ log_debug("SECCOMP features not detected in the kernel, disabling SECCOMP filterering");
+ return 0;
+ }
+
+ SECCOMP_FOREACH_LOCAL_ARCH(arch) {
+ _cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
+
+ log_debug("Applying whitelist on architecture: %s", seccomp_arch_to_string(arch));
+
+ r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ERRNO(EPERM));
+ if (r < 0)
+ return log_error_errno(r, "Failed to allocate seccomp object: %m");
+
+ r = seccomp_add_default_syscall_filter(seccomp, arch, cap_list_retain, syscall_whitelist, syscall_blacklist);
+ if (r < 0)
+ return r;
+
+ r = seccomp_load(seccomp);
+ if (IN_SET(r, -EPERM, -EACCES))
+ 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 (IN_SET(r, -EPERM, -EACCES))
+ 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_whitelist, char **syscall_blacklist) {
+ return 0;
+}
+
+#endif
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