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syscall_sandbox.cpp
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// Copyright (c) 2020-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#if defined(HAVE_CONFIG_H)
#include <config/bitcoin-config.h>
#endif // defined(HAVE_CONFIG_H)
#include <util/syscall_sandbox.h>
#if defined(USE_SYSCALL_SANDBOX)
#include <array>
#include <cassert>
#include <cstdint>
#include <exception>
#include <map>
#include <new>
#include <set>
#include <string>
#include <vector>
#include <logging.h>
#include <tinyformat.h>
#include <util/threadnames.h>
#include <linux/audit.h>
#include <linux/filter.h>
#include <linux/seccomp.h>
#include <linux/unistd.h>
#include <signal.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <unistd.h>
namespace {
bool g_syscall_sandbox_enabled{false};
bool g_syscall_sandbox_log_violation_before_terminating{false};
#if !defined(__x86_64__)
#error Syscall sandbox is an experimental feature currently available only under Linux x86-64.
#endif // defined(__x86_64__)
#ifndef SECCOMP_RET_KILL_PROCESS
#define SECCOMP_RET_KILL_PROCESS 0x80000000U
#endif
// Define system call numbers for x86_64 that are referenced in the system call profile
// but not provided by the kernel headers used in the GUIX build.
// Usually, they can be found via "grep name /usr/include/x86_64-linux-gnu/asm/unistd_64.h"
#ifndef __NR_clone3
#define __NR_clone3 435
#endif
#ifndef __NR_statx
#define __NR_statx 332
#endif
#ifndef __NR_getrandom
#define __NR_getrandom 318
#endif
#ifndef __NR_membarrier
#define __NR_membarrier 324
#endif
#ifndef __NR_copy_file_range
#define __NR_copy_file_range 326
#endif
#ifndef __NR_rseq
#define __NR_rseq 334
#endif
// This list of syscalls in LINUX_SYSCALLS is only used to map syscall numbers to syscall names in
// order to be able to print user friendly error messages which include the syscall name in addition
// to the syscall number.
//
// Example output in case of a syscall violation where the syscall is present in LINUX_SYSCALLS:
//
// ```
// 2021-06-09T12:34:56Z ERROR: The syscall "execve" (syscall number 59) is not allowed by the syscall sandbox in thread "msghand". Please report.
// ```
//
// Example output in case of a syscall violation where the syscall is not present in LINUX_SYSCALLS:
//
// ```
// 2021-06-09T12:34:56Z ERROR: The syscall "*unknown*" (syscall number 314) is not allowed by the syscall sandbox in thread "msghand". Please report.
// ``
//
// LINUX_SYSCALLS contains two types of syscalls:
// 1.) Syscalls that are present under all architectures or relevant Linux kernel versions for which
// we support the syscall sandbox feature (currently only Linux x86-64). Examples include read,
// write, open, close, etc.
// 2.) Syscalls that are present under a subset of architectures or relevant Linux kernel versions
// for which we support the syscall sandbox feature. This type of syscalls should be added to
// LINUX_SYSCALLS conditional on availability like in the following example:
// ...
// #if defined(__NR_arch_dependent_syscall)
// {__NR_arch_dependent_syscall, "arch_dependent_syscall"},
// #endif // defined(__NR_arch_dependent_syscall)
// ...
const std::map<uint32_t, std::string> LINUX_SYSCALLS{
{__NR_accept, "accept"},
{__NR_accept4, "accept4"},
{__NR_access, "access"},
{__NR_acct, "acct"},
{__NR_add_key, "add_key"},
{__NR_adjtimex, "adjtimex"},
{__NR_afs_syscall, "afs_syscall"},
{__NR_alarm, "alarm"},
{__NR_arch_prctl, "arch_prctl"},
{__NR_bind, "bind"},
{__NR_bpf, "bpf"},
{__NR_brk, "brk"},
{__NR_capget, "capget"},
{__NR_capset, "capset"},
{__NR_chdir, "chdir"},
{__NR_chmod, "chmod"},
{__NR_chown, "chown"},
{__NR_chroot, "chroot"},
{__NR_clock_adjtime, "clock_adjtime"},
{__NR_clock_getres, "clock_getres"},
{__NR_clock_gettime, "clock_gettime"},
{__NR_clock_nanosleep, "clock_nanosleep"},
{__NR_clock_settime, "clock_settime"},
{__NR_clone, "clone"},
{__NR_clone3, "clone3"},
{__NR_close, "close"},
{__NR_connect, "connect"},
{__NR_copy_file_range, "copy_file_range"},
{__NR_creat, "creat"},
{__NR_create_module, "create_module"},
{__NR_delete_module, "delete_module"},
{__NR_dup, "dup"},
{__NR_dup2, "dup2"},
{__NR_dup3, "dup3"},
{__NR_epoll_create, "epoll_create"},
{__NR_epoll_create1, "epoll_create1"},
{__NR_epoll_ctl, "epoll_ctl"},
{__NR_epoll_ctl_old, "epoll_ctl_old"},
{__NR_epoll_pwait, "epoll_pwait"},
{__NR_epoll_wait, "epoll_wait"},
{__NR_epoll_wait_old, "epoll_wait_old"},
{__NR_eventfd, "eventfd"},
{__NR_eventfd2, "eventfd2"},
{__NR_execve, "execve"},
{__NR_execveat, "execveat"},
{__NR_exit, "exit"},
{__NR_exit_group, "exit_group"},
{__NR_faccessat, "faccessat"},
{__NR_fadvise64, "fadvise64"},
{__NR_fallocate, "fallocate"},
{__NR_fanotify_init, "fanotify_init"},
{__NR_fanotify_mark, "fanotify_mark"},
{__NR_fchdir, "fchdir"},
{__NR_fchmod, "fchmod"},
{__NR_fchmodat, "fchmodat"},
{__NR_fchown, "fchown"},
{__NR_fchownat, "fchownat"},
{__NR_fcntl, "fcntl"},
{__NR_fdatasync, "fdatasync"},
{__NR_fgetxattr, "fgetxattr"},
{__NR_finit_module, "finit_module"},
{__NR_flistxattr, "flistxattr"},
{__NR_flock, "flock"},
{__NR_fork, "fork"},
{__NR_fremovexattr, "fremovexattr"},
{__NR_fsetxattr, "fsetxattr"},
{__NR_fstat, "fstat"},
{__NR_fstatfs, "fstatfs"},
{__NR_fsync, "fsync"},
{__NR_ftruncate, "ftruncate"},
{__NR_futex, "futex"},
{__NR_futimesat, "futimesat"},
{__NR_get_kernel_syms, "get_kernel_syms"},
{__NR_get_mempolicy, "get_mempolicy"},
{__NR_get_robust_list, "get_robust_list"},
{__NR_get_thread_area, "get_thread_area"},
{__NR_getcpu, "getcpu"},
{__NR_getcwd, "getcwd"},
{__NR_getdents, "getdents"},
{__NR_getdents64, "getdents64"},
{__NR_getegid, "getegid"},
{__NR_geteuid, "geteuid"},
{__NR_getgid, "getgid"},
{__NR_getgroups, "getgroups"},
{__NR_getitimer, "getitimer"},
{__NR_getpeername, "getpeername"},
{__NR_getpgid, "getpgid"},
{__NR_getpgrp, "getpgrp"},
{__NR_getpid, "getpid"},
{__NR_getpmsg, "getpmsg"},
{__NR_getppid, "getppid"},
{__NR_getpriority, "getpriority"},
{__NR_getrandom, "getrandom"},
{__NR_getresgid, "getresgid"},
{__NR_getresuid, "getresuid"},
{__NR_getrlimit, "getrlimit"},
{__NR_getrusage, "getrusage"},
{__NR_getsid, "getsid"},
{__NR_getsockname, "getsockname"},
{__NR_getsockopt, "getsockopt"},
{__NR_gettid, "gettid"},
{__NR_gettimeofday, "gettimeofday"},
{__NR_getuid, "getuid"},
{__NR_getxattr, "getxattr"},
{__NR_init_module, "init_module"},
{__NR_inotify_add_watch, "inotify_add_watch"},
{__NR_inotify_init, "inotify_init"},
{__NR_inotify_init1, "inotify_init1"},
{__NR_inotify_rm_watch, "inotify_rm_watch"},
{__NR_io_cancel, "io_cancel"},
{__NR_io_destroy, "io_destroy"},
{__NR_io_getevents, "io_getevents"},
{__NR_io_setup, "io_setup"},
{__NR_io_submit, "io_submit"},
{__NR_ioctl, "ioctl"},
{__NR_ioperm, "ioperm"},
{__NR_iopl, "iopl"},
{__NR_ioprio_get, "ioprio_get"},
{__NR_ioprio_set, "ioprio_set"},
{__NR_kcmp, "kcmp"},
{__NR_kexec_file_load, "kexec_file_load"},
{__NR_kexec_load, "kexec_load"},
{__NR_keyctl, "keyctl"},
{__NR_kill, "kill"},
{__NR_lchown, "lchown"},
{__NR_lgetxattr, "lgetxattr"},
{__NR_link, "link"},
{__NR_linkat, "linkat"},
{__NR_listen, "listen"},
{__NR_listxattr, "listxattr"},
{__NR_llistxattr, "llistxattr"},
{__NR_lookup_dcookie, "lookup_dcookie"},
{__NR_lremovexattr, "lremovexattr"},
{__NR_lseek, "lseek"},
{__NR_lsetxattr, "lsetxattr"},
{__NR_lstat, "lstat"},
{__NR_madvise, "madvise"},
{__NR_mbind, "mbind"},
{__NR_membarrier, "membarrier"},
{__NR_memfd_create, "memfd_create"},
{__NR_migrate_pages, "migrate_pages"},
{__NR_mincore, "mincore"},
{__NR_mkdir, "mkdir"},
{__NR_mkdirat, "mkdirat"},
{__NR_mknod, "mknod"},
{__NR_mknodat, "mknodat"},
{__NR_mlock, "mlock"},
{__NR_mlock2, "mlock2"},
{__NR_mlockall, "mlockall"},
{__NR_mmap, "mmap"},
{__NR_modify_ldt, "modify_ldt"},
{__NR_mount, "mount"},
{__NR_move_pages, "move_pages"},
{__NR_mprotect, "mprotect"},
{__NR_mq_getsetattr, "mq_getsetattr"},
{__NR_mq_notify, "mq_notify"},
{__NR_mq_open, "mq_open"},
{__NR_mq_timedreceive, "mq_timedreceive"},
{__NR_mq_timedsend, "mq_timedsend"},
{__NR_mq_unlink, "mq_unlink"},
{__NR_mremap, "mremap"},
{__NR_msgctl, "msgctl"},
{__NR_msgget, "msgget"},
{__NR_msgrcv, "msgrcv"},
{__NR_msgsnd, "msgsnd"},
{__NR_msync, "msync"},
{__NR_munlock, "munlock"},
{__NR_munlockall, "munlockall"},
{__NR_munmap, "munmap"},
{__NR_name_to_handle_at, "name_to_handle_at"},
{__NR_nanosleep, "nanosleep"},
{__NR_newfstatat, "newfstatat"},
{__NR_nfsservctl, "nfsservctl"},
{__NR_open, "open"},
{__NR_open_by_handle_at, "open_by_handle_at"},
{__NR_openat, "openat"},
{__NR_pause, "pause"},
{__NR_perf_event_open, "perf_event_open"},
{__NR_personality, "personality"},
{__NR_pipe, "pipe"},
{__NR_pipe2, "pipe2"},
{__NR_pivot_root, "pivot_root"},
#ifdef __NR_pkey_alloc
{__NR_pkey_alloc, "pkey_alloc"},
#endif
#ifdef __NR_pkey_free
{__NR_pkey_free, "pkey_free"},
#endif
#ifdef __NR_pkey_mprotect
{__NR_pkey_mprotect, "pkey_mprotect"},
#endif
{__NR_poll, "poll"},
{__NR_ppoll, "ppoll"},
{__NR_prctl, "prctl"},
{__NR_pread64, "pread64"},
{__NR_preadv, "preadv"},
#ifdef __NR_preadv2
{__NR_preadv2, "preadv2"},
#endif
{__NR_prlimit64, "prlimit64"},
{__NR_process_vm_readv, "process_vm_readv"},
{__NR_process_vm_writev, "process_vm_writev"},
{__NR_pselect6, "pselect6"},
{__NR_ptrace, "ptrace"},
{__NR_putpmsg, "putpmsg"},
{__NR_pwrite64, "pwrite64"},
{__NR_pwritev, "pwritev"},
#ifdef __NR_pwritev2
{__NR_pwritev2, "pwritev2"},
#endif
{__NR__sysctl, "_sysctl"},
{__NR_query_module, "query_module"},
{__NR_quotactl, "quotactl"},
{__NR_read, "read"},
{__NR_readahead, "readahead"},
{__NR_readlink, "readlink"},
{__NR_readlinkat, "readlinkat"},
{__NR_readv, "readv"},
{__NR_reboot, "reboot"},
{__NR_recvfrom, "recvfrom"},
{__NR_recvmmsg, "recvmmsg"},
{__NR_recvmsg, "recvmsg"},
{__NR_remap_file_pages, "remap_file_pages"},
{__NR_removexattr, "removexattr"},
{__NR_rename, "rename"},
{__NR_renameat, "renameat"},
{__NR_renameat2, "renameat2"},
{__NR_request_key, "request_key"},
{__NR_restart_syscall, "restart_syscall"},
{__NR_rmdir, "rmdir"},
{__NR_rseq, "rseq"},
{__NR_rt_sigaction, "rt_sigaction"},
{__NR_rt_sigpending, "rt_sigpending"},
{__NR_rt_sigprocmask, "rt_sigprocmask"},
{__NR_rt_sigqueueinfo, "rt_sigqueueinfo"},
{__NR_rt_sigreturn, "rt_sigreturn"},
{__NR_rt_sigsuspend, "rt_sigsuspend"},
{__NR_rt_sigtimedwait, "rt_sigtimedwait"},
{__NR_rt_tgsigqueueinfo, "rt_tgsigqueueinfo"},
{__NR_sched_get_priority_max, "sched_get_priority_max"},
{__NR_sched_get_priority_min, "sched_get_priority_min"},
{__NR_sched_getaffinity, "sched_getaffinity"},
{__NR_sched_getattr, "sched_getattr"},
{__NR_sched_getparam, "sched_getparam"},
{__NR_sched_getscheduler, "sched_getscheduler"},
{__NR_sched_rr_get_interval, "sched_rr_get_interval"},
{__NR_sched_setaffinity, "sched_setaffinity"},
{__NR_sched_setattr, "sched_setattr"},
{__NR_sched_setparam, "sched_setparam"},
{__NR_sched_setscheduler, "sched_setscheduler"},
{__NR_sched_yield, "sched_yield"},
{__NR_seccomp, "seccomp"},
{__NR_security, "security"},
{__NR_select, "select"},
{__NR_semctl, "semctl"},
{__NR_semget, "semget"},
{__NR_semop, "semop"},
{__NR_semtimedop, "semtimedop"},
{__NR_sendfile, "sendfile"},
{__NR_sendmmsg, "sendmmsg"},
{__NR_sendmsg, "sendmsg"},
{__NR_sendto, "sendto"},
{__NR_set_mempolicy, "set_mempolicy"},
{__NR_set_robust_list, "set_robust_list"},
{__NR_set_thread_area, "set_thread_area"},
{__NR_set_tid_address, "set_tid_address"},
{__NR_setdomainname, "setdomainname"},
{__NR_setfsgid, "setfsgid"},
{__NR_setfsuid, "setfsuid"},
{__NR_setgid, "setgid"},
{__NR_setgroups, "setgroups"},
{__NR_sethostname, "sethostname"},
{__NR_setitimer, "setitimer"},
{__NR_setns, "setns"},
{__NR_setpgid, "setpgid"},
{__NR_setpriority, "setpriority"},
{__NR_setregid, "setregid"},
{__NR_setresgid, "setresgid"},
{__NR_setresuid, "setresuid"},
{__NR_setreuid, "setreuid"},
{__NR_setrlimit, "setrlimit"},
{__NR_setsid, "setsid"},
{__NR_setsockopt, "setsockopt"},
{__NR_settimeofday, "settimeofday"},
{__NR_setuid, "setuid"},
{__NR_setxattr, "setxattr"},
{__NR_shmat, "shmat"},
{__NR_shmctl, "shmctl"},
{__NR_shmdt, "shmdt"},
{__NR_shmget, "shmget"},
{__NR_shutdown, "shutdown"},
{__NR_sigaltstack, "sigaltstack"},
{__NR_signalfd, "signalfd"},
{__NR_signalfd4, "signalfd4"},
{__NR_socket, "socket"},
{__NR_socketpair, "socketpair"},
{__NR_splice, "splice"},
{__NR_stat, "stat"},
{__NR_statfs, "statfs"},
{__NR_statx, "statx"},
{__NR_swapoff, "swapoff"},
{__NR_swapon, "swapon"},
{__NR_symlink, "symlink"},
{__NR_symlinkat, "symlinkat"},
{__NR_sync, "sync"},
{__NR_sync_file_range, "sync_file_range"},
{__NR_syncfs, "syncfs"},
{__NR_sysfs, "sysfs"},
{__NR_sysinfo, "sysinfo"},
{__NR_syslog, "syslog"},
{__NR_tee, "tee"},
{__NR_tgkill, "tgkill"},
{__NR_time, "time"},
{__NR_timer_create, "timer_create"},
{__NR_timer_delete, "timer_delete"},
{__NR_timer_getoverrun, "timer_getoverrun"},
{__NR_timer_gettime, "timer_gettime"},
{__NR_timer_settime, "timer_settime"},
{__NR_timerfd_create, "timerfd_create"},
{__NR_timerfd_gettime, "timerfd_gettime"},
{__NR_timerfd_settime, "timerfd_settime"},
{__NR_times, "times"},
{__NR_tkill, "tkill"},
{__NR_truncate, "truncate"},
{__NR_tuxcall, "tuxcall"},
{__NR_umask, "umask"},
{__NR_umount2, "umount2"},
{__NR_uname, "uname"},
{__NR_unlink, "unlink"},
{__NR_unlinkat, "unlinkat"},
{__NR_unshare, "unshare"},
{__NR_uselib, "uselib"},
{__NR_userfaultfd, "userfaultfd"},
{__NR_ustat, "ustat"},
{__NR_utime, "utime"},
{__NR_utimensat, "utimensat"},
{__NR_utimes, "utimes"},
{__NR_vfork, "vfork"},
{__NR_vhangup, "vhangup"},
{__NR_vmsplice, "vmsplice"},
{__NR_vserver, "vserver"},
{__NR_wait4, "wait4"},
{__NR_waitid, "waitid"},
{__NR_write, "write"},
{__NR_writev, "writev"},
};
std::string GetLinuxSyscallName(uint32_t syscall_number)
{
const auto element = LINUX_SYSCALLS.find(syscall_number);
if (element != LINUX_SYSCALLS.end()) {
return element->second;
}
return "*unknown*";
}
// See Linux kernel developer Kees Cook's seccomp guide at <https://outflux.net/teach-seccomp/> for
// an accessible introduction to using seccomp.
//
// This function largely follows <https://outflux.net/teach-seccomp/step-3/syscall-reporter.c> and
// <https://outflux.net/teach-seccomp/step-3/seccomp-bpf.h>.
//
// Seccomp BPF resources:
// * Seccomp BPF documentation: <https://www.kernel.org/doc/html/latest/userspace-api/seccomp_filter.html>
// * seccomp(2) manual page: <https://www.kernel.org/doc/man-pages/online/pages/man2/seccomp.2.html>
// * Seccomp BPF demo code samples: <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/seccomp>
void SyscallSandboxDebugSignalHandler(int, siginfo_t* signal_info, void* void_signal_context)
{
// The si_code field inside the siginfo_t argument that is passed to a SA_SIGINFO signal handler
// is a value indicating why the signal was sent.
//
// The following value can be placed in si_code for a SIGSYS signal:
// * SYS_SECCOMP (since Linux 3.5): Triggered by a seccomp(2) filter rule.
constexpr int32_t SYS_SECCOMP_SI_CODE{1};
assert(signal_info->si_code == SYS_SECCOMP_SI_CODE);
// The ucontext_t structure contains signal context information that was saved on the user-space
// stack by the kernel.
const ucontext_t* signal_context = static_cast<ucontext_t*>(void_signal_context);
assert(signal_context != nullptr);
std::set_new_handler(std::terminate);
// Portability note: REG_RAX is Linux x86_64 specific.
const uint32_t syscall_number = static_cast<uint32_t>(signal_context->uc_mcontext.gregs[REG_RAX]);
const std::string syscall_name = GetLinuxSyscallName(syscall_number);
const std::string thread_name = !util::ThreadGetInternalName().empty() ? util::ThreadGetInternalName() : "*unnamed*";
const std::string error_message = strprintf("ERROR: The syscall \"%s\" (syscall number %d) is not allowed by the syscall sandbox in thread \"%s\". Please report.", syscall_name, syscall_number, thread_name);
tfm::format(std::cerr, "%s\n", error_message);
LogPrintf("%s\n", error_message);
std::terminate();
}
// This function largely follows install_syscall_reporter from Kees Cook's seccomp guide:
// <https://outflux.net/teach-seccomp/step-3/syscall-reporter.c>
bool SetupSyscallSandboxDebugHandler()
{
struct sigaction action = {};
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, SIGSYS);
action.sa_sigaction = &SyscallSandboxDebugSignalHandler;
action.sa_flags = SA_SIGINFO;
if (sigaction(SIGSYS, &action, nullptr) < 0) {
return false;
}
if (sigprocmask(SIG_UNBLOCK, &mask, nullptr)) {
return false;
}
return true;
}
enum class SyscallSandboxAction {
KILL_PROCESS,
INVOKE_SIGNAL_HANDLER,
};
class SeccompPolicyBuilder
{
std::set<uint32_t> allowed_syscalls;
public:
SeccompPolicyBuilder()
{
// Allowed by default.
AllowAddressSpaceAccess();
AllowEpoll();
AllowEventFd();
AllowFutex();
AllowGeneralIo();
AllowGetRandom();
AllowGetSimpleId();
AllowGetTime();
AllowGlobalProcessEnvironment();
AllowGlobalSystemStatus();
AllowKernelInternalApi();
AllowNetworkSocketInformation();
AllowOperationOnExistingFileDescriptor();
AllowPipe();
AllowPrctl();
AllowProcessStartOrDeath();
AllowScheduling();
AllowSignalHandling();
AllowSleep();
AllowUmask();
}
void AllowAddressSpaceAccess()
{
allowed_syscalls.insert(__NR_brk); // change data segment size
allowed_syscalls.insert(__NR_madvise); // give advice about use of memory
allowed_syscalls.insert(__NR_membarrier); // issue memory barriers on a set of threads
allowed_syscalls.insert(__NR_mincore); // check if virtual memory is in RAM
allowed_syscalls.insert(__NR_mlock); // lock memory
allowed_syscalls.insert(__NR_mmap); // map files or devices into memory
allowed_syscalls.insert(__NR_mprotect); // set protection on a region of memory
allowed_syscalls.insert(__NR_mremap); // remap a file in memory
allowed_syscalls.insert(__NR_munlock); // unlock memory
allowed_syscalls.insert(__NR_munmap); // unmap files or devices into memory
}
void AllowEpoll()
{
allowed_syscalls.insert(__NR_epoll_create1); // open an epoll file descriptor
allowed_syscalls.insert(__NR_epoll_ctl); // control interface for an epoll file descriptor
allowed_syscalls.insert(__NR_epoll_pwait); // wait for an I/O event on an epoll file descriptor
allowed_syscalls.insert(__NR_epoll_wait); // wait for an I/O event on an epoll file descriptor
}
void AllowEventFd()
{
allowed_syscalls.insert(__NR_eventfd2); // create a file descriptor for event notification
}
void AllowFileSystem()
{
allowed_syscalls.insert(__NR_access); // check user's permissions for a file
allowed_syscalls.insert(__NR_chdir); // change working directory
allowed_syscalls.insert(__NR_chmod); // change permissions of a file
allowed_syscalls.insert(__NR_copy_file_range); // copy a range of data from one file to another
allowed_syscalls.insert(__NR_fallocate); // manipulate file space
allowed_syscalls.insert(__NR_fchmod); // change permissions of a file
allowed_syscalls.insert(__NR_fchown); // change ownership of a file
allowed_syscalls.insert(__NR_fdatasync); // synchronize a file's in-core state with storage device
allowed_syscalls.insert(__NR_flock); // apply or remove an advisory lock on an open file
allowed_syscalls.insert(__NR_fstat); // get file status
allowed_syscalls.insert(__NR_fstatfs); // get file system status
allowed_syscalls.insert(__NR_fsync); // synchronize a file's in-core state with storage device
allowed_syscalls.insert(__NR_ftruncate); // truncate a file to a specified length
allowed_syscalls.insert(__NR_getcwd); // get current working directory
allowed_syscalls.insert(__NR_getdents); // get directory entries
allowed_syscalls.insert(__NR_getdents64); // get directory entries
allowed_syscalls.insert(__NR_lstat); // get file status
allowed_syscalls.insert(__NR_mkdir); // create a directory
allowed_syscalls.insert(__NR_newfstatat); // get file status
allowed_syscalls.insert(__NR_open); // open and possibly create a file
allowed_syscalls.insert(__NR_openat); // open and possibly create a file
allowed_syscalls.insert(__NR_readlink); // read value of a symbolic link
allowed_syscalls.insert(__NR_rename); // change the name or location of a file
allowed_syscalls.insert(__NR_rmdir); // delete a directory
allowed_syscalls.insert(__NR_sendfile); // transfer data between file descriptors
allowed_syscalls.insert(__NR_stat); // get file status
allowed_syscalls.insert(__NR_statfs); // get filesystem statistics
allowed_syscalls.insert(__NR_statx); // get file status (extended)
allowed_syscalls.insert(__NR_unlink); // delete a name and possibly the file it refers to
allowed_syscalls.insert(__NR_unlinkat); // delete relative to a directory file descriptor
}
void AllowFutex()
{
allowed_syscalls.insert(__NR_futex); // fast user-space locking
allowed_syscalls.insert(__NR_set_robust_list); // set list of robust futexes
}
void AllowGeneralIo()
{
allowed_syscalls.insert(__NR_ioctl); // control device
allowed_syscalls.insert(__NR_lseek); // reposition read/write file offset
allowed_syscalls.insert(__NR_poll); // wait for some event on a file descriptor
allowed_syscalls.insert(__NR_ppoll); // wait for some event on a file descriptor
allowed_syscalls.insert(__NR_pread64); // read from a file descriptor at a given offset
allowed_syscalls.insert(__NR_pwrite64); // write to a file descriptor at a given offset
allowed_syscalls.insert(__NR_read); // read from a file descriptor
allowed_syscalls.insert(__NR_readv); // read data into multiple buffers
allowed_syscalls.insert(__NR_recvfrom); // receive a message from a socket
allowed_syscalls.insert(__NR_recvmsg); // receive a message from a socket
allowed_syscalls.insert(__NR_select); // synchronous I/O multiplexing
allowed_syscalls.insert(__NR_sendmmsg); // send multiple messages on a socket
allowed_syscalls.insert(__NR_sendmsg); // send a message on a socket
allowed_syscalls.insert(__NR_sendto); // send a message on a socket
allowed_syscalls.insert(__NR_write); // write to a file descriptor
allowed_syscalls.insert(__NR_writev); // write data into multiple buffers
}
void AllowGetRandom()
{
allowed_syscalls.insert(__NR_getrandom); // obtain a series of random bytes
}
void AllowGetSimpleId()
{
allowed_syscalls.insert(__NR_getegid); // get group identity
allowed_syscalls.insert(__NR_geteuid); // get user identity
allowed_syscalls.insert(__NR_getgid); // get group identity
allowed_syscalls.insert(__NR_getpgid); // get process group
allowed_syscalls.insert(__NR_getpid); // get process identification
allowed_syscalls.insert(__NR_getppid); // get process identification
allowed_syscalls.insert(__NR_getresgid); // get real, effective and saved group IDs
allowed_syscalls.insert(__NR_getresuid); // get real, effective and saved user IDs
allowed_syscalls.insert(__NR_getsid); // get session ID
allowed_syscalls.insert(__NR_gettid); // get thread identification
allowed_syscalls.insert(__NR_getuid); // get user identity
}
void AllowGetTime()
{
allowed_syscalls.insert(__NR_clock_getres); // find the resolution (precision) of the specified clock
allowed_syscalls.insert(__NR_clock_gettime); // retrieve the time of the specified clock
allowed_syscalls.insert(__NR_gettimeofday); // get timeval
}
void AllowGlobalProcessEnvironment()
{
allowed_syscalls.insert(__NR_getrlimit); // get resource limits
allowed_syscalls.insert(__NR_getrusage); // get resource usage
allowed_syscalls.insert(__NR_prlimit64); // get/set resource limits
}
void AllowGlobalSystemStatus()
{
allowed_syscalls.insert(__NR_sysinfo); // return system information
allowed_syscalls.insert(__NR_uname); // get name and information about current kernel
}
void AllowKernelInternalApi()
{
allowed_syscalls.insert(__NR_restart_syscall); // restart a system call after interruption by a stop signal
}
void AllowNetwork()
{
allowed_syscalls.insert(__NR_accept); // accept a connection on a socket
allowed_syscalls.insert(__NR_accept4); // accept a connection on a socket
allowed_syscalls.insert(__NR_bind); // bind a name to a socket
allowed_syscalls.insert(__NR_connect); // initiate a connection on a socket
allowed_syscalls.insert(__NR_listen); // listen for connections on a socket
allowed_syscalls.insert(__NR_setsockopt); // set options on sockets
allowed_syscalls.insert(__NR_socket); // create an endpoint for communication
allowed_syscalls.insert(__NR_socketpair); // create a pair of connected sockets
}
void AllowNetworkSocketInformation()
{
allowed_syscalls.insert(__NR_getpeername); // get name of connected peer socket
allowed_syscalls.insert(__NR_getsockname); // get socket name
allowed_syscalls.insert(__NR_getsockopt); // get options on sockets
}
void AllowOperationOnExistingFileDescriptor()
{
allowed_syscalls.insert(__NR_close); // close a file descriptor
allowed_syscalls.insert(__NR_dup); // duplicate a file descriptor
allowed_syscalls.insert(__NR_dup2); // duplicate a file descriptor
allowed_syscalls.insert(__NR_fcntl); // manipulate file descriptor
allowed_syscalls.insert(__NR_shutdown); // shut down part of a full-duplex connection
}
void AllowPipe()
{
allowed_syscalls.insert(__NR_pipe); // create pipe
allowed_syscalls.insert(__NR_pipe2); // create pipe
}
void AllowPrctl()
{
allowed_syscalls.insert(__NR_arch_prctl); // set architecture-specific thread state
allowed_syscalls.insert(__NR_prctl); // operations on a process
}
void AllowProcessStartOrDeath()
{
allowed_syscalls.insert(__NR_clone); // create a child process
allowed_syscalls.insert(__NR_clone3); // create a child process
allowed_syscalls.insert(__NR_exit); // terminate the calling process
allowed_syscalls.insert(__NR_exit_group); // exit all threads in a process
allowed_syscalls.insert(__NR_fork); // create a child process
allowed_syscalls.insert(__NR_tgkill); // send a signal to a thread
allowed_syscalls.insert(__NR_wait4); // wait for process to change state, BSD style
allowed_syscalls.insert(__NR_rseq); // register restartable sequence for thread
}
void AllowScheduling()
{
allowed_syscalls.insert(__NR_sched_getaffinity); // set a thread's CPU affinity mask
allowed_syscalls.insert(__NR_sched_getparam); // get scheduling parameters
allowed_syscalls.insert(__NR_sched_getscheduler); // get scheduling policy/parameters
allowed_syscalls.insert(__NR_sched_setscheduler); // set scheduling policy/parameters
allowed_syscalls.insert(__NR_sched_yield); // yield the processor
}
void AllowSignalHandling()
{
allowed_syscalls.insert(__NR_rt_sigaction); // examine and change a signal action
allowed_syscalls.insert(__NR_rt_sigprocmask); // examine and change blocked signals
allowed_syscalls.insert(__NR_rt_sigreturn); // return from signal handler and cleanup stack frame
allowed_syscalls.insert(__NR_sigaltstack); // set and/or get signal stack context
}
void AllowSleep()
{
allowed_syscalls.insert(__NR_clock_nanosleep); // high-resolution sleep with specifiable clock
allowed_syscalls.insert(__NR_nanosleep); // high-resolution sleep
}
void AllowUmask()
{
allowed_syscalls.insert(__NR_umask); // set file mode creation mask
}
// See Linux kernel developer Kees Cook's seccomp guide at <https://outflux.net/teach-seccomp/>
// for an accessible introduction to using seccomp.
//
// This function largely follows <https://outflux.net/teach-seccomp/step-3/seccomp-bpf.h>.
std::vector<sock_filter> BuildFilter(SyscallSandboxAction default_action)
{
std::vector<sock_filter> bpf_policy;
// See VALIDATE_ARCHITECTURE in seccomp-bpf.h referenced above.
bpf_policy.push_back(BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct seccomp_data, arch)));
// Portability note: AUDIT_ARCH_X86_64 is Linux x86_64 specific.
bpf_policy.push_back(BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, AUDIT_ARCH_X86_64, 1, 0));
bpf_policy.push_back(BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_KILL_PROCESS));
// See EXAMINE_SYSCALL in seccomp-bpf.h referenced above.
bpf_policy.push_back(BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct seccomp_data, nr)));
for (const uint32_t allowed_syscall : allowed_syscalls) {
// See ALLOW_SYSCALL in seccomp-bpf.h referenced above.
bpf_policy.push_back(BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, allowed_syscall, 0, 1));
bpf_policy.push_back(BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_ALLOW));
}
switch (default_action) {
case SyscallSandboxAction::KILL_PROCESS:
// Disallow syscall and kill the process.
//
// See KILL_PROCESS in seccomp-bpf.h referenced above.
//
// Note that we're using SECCOMP_RET_KILL_PROCESS (kill the process) instead
// of SECCOMP_RET_KILL_THREAD (kill the thread). The SECCOMP_RET_KILL_PROCESS
// action was introduced in Linux 4.14.
//
// SECCOMP_RET_KILL_PROCESS: Results in the entire process exiting immediately without
// executing the system call.
//
// SECCOMP_RET_KILL_PROCESS documentation:
// <https://www.kernel.org/doc/html/latest/userspace-api/seccomp_filter.html>
bpf_policy.push_back(BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_KILL_PROCESS));
break;
case SyscallSandboxAction::INVOKE_SIGNAL_HANDLER:
// Disallow syscall and force a SIGSYS to trigger syscall debug reporter.
//
// SECCOMP_RET_TRAP: Results in the kernel sending a SIGSYS signal to the triggering
// task without executing the system call.
//
// SECCOMP_RET_TRAP documentation:
// <https://www.kernel.org/doc/html/latest/userspace-api/seccomp_filter.html>
bpf_policy.push_back(BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_TRAP));
break;
}
return bpf_policy;
}
};
} // namespace
bool SetupSyscallSandbox(bool log_syscall_violation_before_terminating)
{
assert(!g_syscall_sandbox_enabled && "SetupSyscallSandbox(...) should only be called once.");
g_syscall_sandbox_enabled = true;
g_syscall_sandbox_log_violation_before_terminating = log_syscall_violation_before_terminating;
if (log_syscall_violation_before_terminating) {
if (!SetupSyscallSandboxDebugHandler()) {
return false;
}
}
return true;
}
void TestDisallowedSandboxCall()
{
// The getgroups syscall is assumed NOT to be allowed by the syscall sandbox policy.
std::array<gid_t, 1> groups;
[[maybe_unused]] int32_t ignored = getgroups(groups.size(), groups.data());
}
#endif // defined(USE_SYSCALL_SANDBOX)
void SetSyscallSandboxPolicy(SyscallSandboxPolicy syscall_policy)
{
#if defined(USE_SYSCALL_SANDBOX)
if (!g_syscall_sandbox_enabled) {
return;
}
SeccompPolicyBuilder seccomp_policy_builder;
switch (syscall_policy) {
case SyscallSandboxPolicy::INITIALIZATION: // Thread: main thread (state: init)
// SyscallSandboxPolicy::INITIALIZATION is the first policy loaded.
//
// Subsequently loaded policies can reduce the abilities further, but
// abilities can never be regained.
//
// SyscallSandboxPolicy::INITIALIZATION must thus be a superset of all
// other policies.
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::INITIALIZATION_DNS_SEED: // Thread: dnsseed
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::INITIALIZATION_LOAD_BLOCKS: // Thread: loadblk
seccomp_policy_builder.AllowFileSystem();
break;
case SyscallSandboxPolicy::INITIALIZATION_MAP_PORT: // Thread: mapport
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::MESSAGE_HANDLER: // Thread: msghand
seccomp_policy_builder.AllowFileSystem();
break;
case SyscallSandboxPolicy::NET: // Thread: net
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::NET_ADD_CONNECTION: // Thread: addcon
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::NET_HTTP_SERVER: // Thread: http
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::NET_HTTP_SERVER_WORKER: // Thread: httpworker.<N>
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::NET_OPEN_CONNECTION: // Thread: opencon
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::SCHEDULER: // Thread: scheduler
seccomp_policy_builder.AllowFileSystem();
break;
case SyscallSandboxPolicy::TOR_CONTROL: // Thread: torcontrol
seccomp_policy_builder.AllowFileSystem();
seccomp_policy_builder.AllowNetwork();
break;
case SyscallSandboxPolicy::TX_INDEX: // Thread: txindex
seccomp_policy_builder.AllowFileSystem();
break;
case SyscallSandboxPolicy::VALIDATION_SCRIPT_CHECK: // Thread: scriptch.<N>
break;
case SyscallSandboxPolicy::SHUTOFF: // Thread: main thread (state: shutoff)
seccomp_policy_builder.AllowFileSystem();
break;
}
const SyscallSandboxAction default_action = g_syscall_sandbox_log_violation_before_terminating ? SyscallSandboxAction::INVOKE_SIGNAL_HANDLER : SyscallSandboxAction::KILL_PROCESS;
std::vector<sock_filter> filter = seccomp_policy_builder.BuildFilter(default_action);
const sock_fprog prog = {
.len = static_cast<uint16_t>(filter.size()),
.filter = filter.data(),
};
// Do not allow abilities to be regained after being dropped.
//
// PR_SET_NO_NEW_PRIVS documentation: <https://www.kernel.org/doc/html/latest/userspace-api/no_new_privs.html>
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) != 0) {
throw std::runtime_error("Syscall sandbox enforcement failed: prctl(PR_SET_NO_NEW_PRIVS)");
}
// Install seccomp-bpf syscall filter.
//
// PR_SET_SECCOMP documentation: <https://www.kernel.org/doc/html/latest/userspace-api/seccomp_filter.html>
if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog) != 0) {
throw std::runtime_error("Syscall sandbox enforcement failed: prctl(PR_SET_SECCOMP)");
}
const std::string thread_name = !util::ThreadGetInternalName().empty() ? util::ThreadGetInternalName() : "*unnamed*";
LogPrint(BCLog::UTIL, "Syscall filter installed for thread \"%s\"\n", thread_name);
#endif // defined(USE_SYSCALL_SANDBOX)
}