55 lines
2.5 KiB
C
55 lines
2.5 KiB
C
#define _GNU_SOURCE
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#include <errno.h>
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#include <linux/sched.h>
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#include <seccomp.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/socket.h>
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#include <unistd.h>
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/* Layered on an empty mount tree, fresh PID/user/network namespaces, no caps,
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* no inherited descriptors and an immutable runtime closure. Deny kernel and
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* process escape surfaces; retain V8's ordinary memory/thread syscalls. */
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static void checked(int result) {
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if (result < 0) {
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fprintf(stderr, "seccomp rule: %d\n", result);
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exit(1);
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}
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}
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int main(void) {
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scmp_filter_ctx filter = seccomp_init(SCMP_ACT_ALLOW);
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if (!filter) return 1;
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const char *denied[] = {
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"fork", "vfork", "execveat", "ptrace", "process_vm_readv", "process_vm_writev",
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"pidfd_getfd", "kcmp", "bpf", "perf_event_open", "userfaultfd", "io_uring_setup",
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"mount", "umount2", "pivot_root", "chroot", "move_mount", "open_tree", "fsopen",
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"fsconfig", "fsmount", "fspick", "mount_setattr", "open_by_handle_at",
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"name_to_handle_at", "setns", "unshare", "keyctl", "add_key", "request_key",
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"reboot", "kexec_load", "kexec_file_load", "init_module", "finit_module",
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"delete_module", "swapon", "swapoff", "syslog", "acct", "sethostname",
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"setdomainname", "iopl", "ioperm", "lookup_dcookie", NULL
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};
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for (size_t i = 0; denied[i]; i++) {
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int syscall = seccomp_syscall_resolve_name(denied[i]);
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if (syscall != __NR_SCMP_ERROR)
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checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), syscall, 0));
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}
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/* glibc falls back to clone when clone3 is unavailable. Only thread creation
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* is admitted; subprocesses and new namespaces cannot be manufactured. */
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checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(ENOSYS), SCMP_SYS(clone3), 0));
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checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(clone), 1,
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SCMP_A0(SCMP_CMP_MASKED_EQ, CLONE_THREAD, 0)));
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const unsigned long namespaces[] = {CLONE_NEWUSER, CLONE_NEWNS, CLONE_NEWNET,
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CLONE_NEWPID, CLONE_NEWIPC, CLONE_NEWUTS, CLONE_NEWCGROUP};
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for (size_t i = 0; i < sizeof(namespaces) / sizeof(namespaces[0]); i++)
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checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(clone), 1,
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SCMP_A0(SCMP_CMP_MASKED_EQ, namespaces[i], namespaces[i])));
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checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(socket), 1,
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SCMP_A0(SCMP_CMP_NE, AF_UNIX)));
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checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(ioctl), 1,
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SCMP_A1(SCMP_CMP_EQ, 0x5412))); /* TIOCSTI */
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checked(seccomp_export_bpf(filter, STDOUT_FILENO));
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seccomp_release(filter);
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return 0;
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}
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