diff options
Diffstat (limited to 'helper/seccomp/seccomp-export.c')
| -rw-r--r-- | helper/seccomp/seccomp-export.c | 300 |
1 files changed, 0 insertions, 300 deletions
diff --git a/helper/seccomp/seccomp-export.c b/helper/seccomp/seccomp-export.c deleted file mode 100644 index 5a3a56be..00000000 --- a/helper/seccomp/seccomp-export.c +++ /dev/null @@ -1,300 +0,0 @@ -#ifndef _GNU_SOURCE -#define _GNU_SOURCE // CLONE_NEWUSER -#endif - -#include "seccomp-export.h" -#include <stdlib.h> -#include <stdio.h> -#include <assert.h> -#include <errno.h> -#include <sys/syscall.h> -#include <sys/socket.h> -#include <sys/ioctl.h> -#include <sys/personality.h> -#include <sched.h> - -#if (SCMP_VER_MAJOR < 2) || \ - (SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR < 5) || \ - (SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR == 5 && SCMP_VER_MICRO < 1) -#error This package requires libseccomp >= v2.5.1 -#endif - -struct f_syscall_act { - int syscall; - int m_errno; - struct scmp_arg_cmp *arg; -}; - -#define LEN(arr) (sizeof(arr) / sizeof((arr)[0])) - -#define SECCOMP_RULESET_ADD(ruleset) do { \ - if (opts & F_VERBOSE) F_println("adding seccomp ruleset \"" #ruleset "\""); \ - for (int i = 0; i < LEN(ruleset); i++) { \ - assert(ruleset[i].m_errno == EPERM || ruleset[i].m_errno == ENOSYS); \ - \ - if (ruleset[i].arg) \ - ret = seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ruleset[i].m_errno), ruleset[i].syscall, 1, *ruleset[i].arg); \ - else \ - ret = seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ruleset[i].m_errno), ruleset[i].syscall, 0); \ - \ - if (ret == -EFAULT) { \ - res = 4; \ - goto out; \ - } else if (ret < 0) { \ - res = 5; \ - errno = -ret; \ - goto out; \ - } \ - } \ -} while (0) - -int32_t f_export_bpf(int fd, uint32_t arch, uint32_t multiarch, f_syscall_opts opts) { - int32_t res = 0; // refer to resErr for meaning - int allow_multiarch = opts & F_MULTIARCH; - int allowed_personality = PER_LINUX; - - if (opts & F_LINUX32) - allowed_personality = PER_LINUX32; - - // flatpak commit 4c3bf179e2e4a2a298cd1db1d045adaf3f564532 - - struct f_syscall_act deny_common[] = { - // Block dmesg - {SCMP_SYS(syslog), EPERM}, - // Useless old syscall - {SCMP_SYS(uselib), EPERM}, - // Don't allow disabling accounting - {SCMP_SYS(acct), EPERM}, - // Don't allow reading current quota use - {SCMP_SYS(quotactl), EPERM}, - - // Don't allow access to the kernel keyring - {SCMP_SYS(add_key), EPERM}, - {SCMP_SYS(keyctl), EPERM}, - {SCMP_SYS(request_key), EPERM}, - - // Scary VM/NUMA ops - {SCMP_SYS(move_pages), EPERM}, - {SCMP_SYS(mbind), EPERM}, - {SCMP_SYS(get_mempolicy), EPERM}, - {SCMP_SYS(set_mempolicy), EPERM}, - {SCMP_SYS(migrate_pages), EPERM}, - }; - - // fortify: project-specific extensions - struct f_syscall_act deny_common_ext[] = { - // system calls for changing the system clock - {SCMP_SYS(adjtimex), EPERM}, - {SCMP_SYS(clock_adjtime), EPERM}, - {SCMP_SYS(clock_adjtime64), EPERM}, - {SCMP_SYS(clock_settime), EPERM}, - {SCMP_SYS(clock_settime64), EPERM}, - {SCMP_SYS(settimeofday), EPERM}, - - // loading and unloading of kernel modules - {SCMP_SYS(delete_module), EPERM}, - {SCMP_SYS(finit_module), EPERM}, - {SCMP_SYS(init_module), EPERM}, - - // system calls for rebooting and reboot preparation - {SCMP_SYS(kexec_file_load), EPERM}, - {SCMP_SYS(kexec_load), EPERM}, - {SCMP_SYS(reboot), EPERM}, - - // system calls for enabling/disabling swap devices - {SCMP_SYS(swapoff), EPERM}, - {SCMP_SYS(swapon), EPERM}, - }; - - struct f_syscall_act deny_ns[] = { - // Don't allow subnamespace setups: - {SCMP_SYS(unshare), EPERM}, - {SCMP_SYS(setns), EPERM}, - {SCMP_SYS(mount), EPERM}, - {SCMP_SYS(umount), EPERM}, - {SCMP_SYS(umount2), EPERM}, - {SCMP_SYS(pivot_root), EPERM}, - {SCMP_SYS(chroot), EPERM}, -#if defined(__s390__) || defined(__s390x__) || defined(__CRIS__) - // Architectures with CONFIG_CLONE_BACKWARDS2: the child stack - // and flags arguments are reversed so the flags come second - {SCMP_SYS(clone), EPERM, &SCMP_A1(SCMP_CMP_MASKED_EQ, CLONE_NEWUSER, CLONE_NEWUSER)}, -#else - // Normally the flags come first - {SCMP_SYS(clone), EPERM, &SCMP_A0(SCMP_CMP_MASKED_EQ, CLONE_NEWUSER, CLONE_NEWUSER)}, -#endif - - // seccomp can't look into clone3()'s struct clone_args to check whether - // the flags are OK, so we have no choice but to block clone3(). - // Return ENOSYS so user-space will fall back to clone(). - // (CVE-2021-41133; see also https://github.com/moby/moby/commit/9f6b562d) - {SCMP_SYS(clone3), ENOSYS}, - - // New mount manipulation APIs can also change our VFS. There's no - // legitimate reason to do these in the sandbox, so block all of them - // rather than thinking about which ones might be dangerous. - // (CVE-2021-41133) - {SCMP_SYS(open_tree), ENOSYS}, - {SCMP_SYS(move_mount), ENOSYS}, - {SCMP_SYS(fsopen), ENOSYS}, - {SCMP_SYS(fsconfig), ENOSYS}, - {SCMP_SYS(fsmount), ENOSYS}, - {SCMP_SYS(fspick), ENOSYS}, - {SCMP_SYS(mount_setattr), ENOSYS}, - }; - - // fortify: project-specific extensions - struct f_syscall_act deny_ns_ext[] = { - // changing file ownership - {SCMP_SYS(chown), EPERM}, - {SCMP_SYS(chown32), EPERM}, - {SCMP_SYS(fchown), EPERM}, - {SCMP_SYS(fchown32), EPERM}, - {SCMP_SYS(fchownat), EPERM}, - {SCMP_SYS(lchown), EPERM}, - {SCMP_SYS(lchown32), EPERM}, - - // system calls for changing user ID and group ID credentials - {SCMP_SYS(setgid), EPERM}, - {SCMP_SYS(setgid32), EPERM}, - {SCMP_SYS(setgroups), EPERM}, - {SCMP_SYS(setgroups32), EPERM}, - {SCMP_SYS(setregid), EPERM}, - {SCMP_SYS(setregid32), EPERM}, - {SCMP_SYS(setresgid), EPERM}, - {SCMP_SYS(setresgid32), EPERM}, - {SCMP_SYS(setresuid), EPERM}, - {SCMP_SYS(setresuid32), EPERM}, - {SCMP_SYS(setreuid), EPERM}, - {SCMP_SYS(setreuid32), EPERM}, - {SCMP_SYS(setuid), EPERM}, - {SCMP_SYS(setuid32), EPERM}, - }; - - struct f_syscall_act deny_tty[] = { - // Don't allow faking input to the controlling tty (CVE-2017-5226) - {SCMP_SYS(ioctl), EPERM, &SCMP_A1(SCMP_CMP_MASKED_EQ, 0xFFFFFFFFu, (int)TIOCSTI)}, - // In the unlikely event that the controlling tty is a Linux virtual - // console (/dev/tty2 or similar), copy/paste operations have an effect - // similar to TIOCSTI (CVE-2023-28100) - {SCMP_SYS(ioctl), EPERM, &SCMP_A1(SCMP_CMP_MASKED_EQ, 0xFFFFFFFFu, (int)TIOCLINUX)}, - }; - - struct f_syscall_act deny_devel[] = { - // Profiling operations; we expect these to be done by tools from outside - // the sandbox. In particular perf has been the source of many CVEs. - {SCMP_SYS(perf_event_open), EPERM}, - // Don't allow you to switch to bsd emulation or whatnot - {SCMP_SYS(personality), EPERM, &SCMP_A0(SCMP_CMP_NE, allowed_personality)}, - - {SCMP_SYS(ptrace), EPERM} - }; - - struct f_syscall_act deny_emu[] = { - // modify_ldt is a historic source of interesting information leaks, - // so it's disabled as a hardening measure. - // However, it is required to run old 16-bit applications - // as well as some Wine patches, so it's allowed in multiarch. - {SCMP_SYS(modify_ldt), EPERM}, - }; - - // fortify: project-specific extensions - struct f_syscall_act deny_emu_ext[] = { - {SCMP_SYS(subpage_prot), ENOSYS}, - {SCMP_SYS(switch_endian), ENOSYS}, - {SCMP_SYS(vm86), ENOSYS}, - {SCMP_SYS(vm86old), ENOSYS}, - }; - - // Blocklist all but unix, inet, inet6 and netlink - struct - { - int family; - f_syscall_opts flags_mask; - } socket_family_allowlist[] = { - // NOTE: Keep in numerical order - { AF_UNSPEC, 0 }, - { AF_LOCAL, 0 }, - { AF_INET, 0 }, - { AF_INET6, 0 }, - { AF_NETLINK, 0 }, - { AF_CAN, F_CAN }, - { AF_BLUETOOTH, F_BLUETOOTH }, - }; - - scmp_filter_ctx ctx = seccomp_init(SCMP_ACT_ALLOW); - if (ctx == NULL) { - res = 1; - goto out; - } else - errno = 0; - - int ret; - - // We only really need to handle arches on multiarch systems. - // If only one arch is supported the default is fine - if (arch != 0) { - // This *adds* the target arch, instead of replacing the - // native one. This is not ideal, because we'd like to only - // allow the target arch, but we can't really disallow the - // native arch at this point, because then bubblewrap - // couldn't continue running. - ret = seccomp_arch_add(ctx, arch); - if (ret < 0 && ret != -EEXIST) { - res = 2; - errno = -ret; - goto out; - } - - if (allow_multiarch && multiarch != 0) { - ret = seccomp_arch_add(ctx, multiarch); - if (ret < 0 && ret != -EEXIST) { - res = 3; - errno = -ret; - goto out; - } - } - } - - SECCOMP_RULESET_ADD(deny_common); - if (opts & F_DENY_NS) SECCOMP_RULESET_ADD(deny_ns); - if (opts & F_DENY_TTY) SECCOMP_RULESET_ADD(deny_tty); - if (opts & F_DENY_DEVEL) SECCOMP_RULESET_ADD(deny_devel); - if (!allow_multiarch) SECCOMP_RULESET_ADD(deny_emu); - if (opts & F_EXT) { - SECCOMP_RULESET_ADD(deny_common_ext); - if (opts & F_DENY_NS) SECCOMP_RULESET_ADD(deny_ns_ext); - if (!allow_multiarch) SECCOMP_RULESET_ADD(deny_emu_ext); - } - - // Socket filtering doesn't work on e.g. i386, so ignore failures here - // However, we need to user seccomp_rule_add_exact to avoid libseccomp doing - // something else: https://github.com/seccomp/libseccomp/issues/8 - int last_allowed_family = -1; - for (int i = 0; i < LEN(socket_family_allowlist); i++) { - if (socket_family_allowlist[i].flags_mask != 0 && - (socket_family_allowlist[i].flags_mask & opts) != socket_family_allowlist[i].flags_mask) - continue; - - for (int disallowed = last_allowed_family + 1; disallowed < socket_family_allowlist[i].family; disallowed++) { - // Blocklist the in-between valid families - seccomp_rule_add_exact(ctx, SCMP_ACT_ERRNO(EAFNOSUPPORT), SCMP_SYS(socket), 1, SCMP_A0(SCMP_CMP_EQ, disallowed)); - } - last_allowed_family = socket_family_allowlist[i].family; - } - // Blocklist the rest - seccomp_rule_add_exact(ctx, SCMP_ACT_ERRNO(EAFNOSUPPORT), SCMP_SYS(socket), 1, SCMP_A0(SCMP_CMP_GE, last_allowed_family + 1)); - - ret = seccomp_export_bpf(ctx, fd); - if (ret != 0) { - res = 6; - errno = -ret; - goto out; - } - -out: - if (ctx) - seccomp_release(ctx); - - return res; -} |