helper/seccomp: separate seccomp package

Signed-off-by: Ophestra <cat@gensokyo.uk>

4 files changed, 15 insertions, 443 deletions

diff --git a/helper/bwrap/seccomp-export.c b/helper/bwrap/seccomp-export.c
deleted file mode 100644
index 78d27e0b..00000000
--- a/helper/bwrap/seccomp-export.c
+++ /dev/null
@@ -1,308 +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 {                                                                      \
-  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)
-
-
-int f_tmpfile_fd() {
-  FILE *f = tmpfile();
-  if (f == NULL)
-    return -1;
-  return fileno(f);
-}
-
-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;
-}
diff --git a/helper/bwrap/seccomp-export.h b/helper/bwrap/seccomp-export.h
deleted file mode 100644
index 90640d8f..00000000
--- a/helper/bwrap/seccomp-export.h
+++ /dev/null
@@ -1,23 +0,0 @@
-#include <stdint.h>
-#include <seccomp.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
-
-typedef enum {
-  F_EXT        = 1 << 0,
-  F_DENY_NS    = 1 << 1,
-  F_DENY_TTY   = 1 << 2,
-  F_DENY_DEVEL = 1 << 3,
-  F_MULTIARCH  = 1 << 4,
-  F_LINUX32    = 1 << 5,
-  F_CAN        = 1 << 6,
-  F_BLUETOOTH  = 1 << 7,
-} f_syscall_opts;
-
-extern void F_println(char *v);
-int f_tmpfile_fd();
-int32_t f_export_bpf(int fd, uint32_t arch, uint32_t multiarch, f_syscall_opts opts);
\ No newline at end of file
diff --git a/helper/bwrap/seccomp-resolve.go b/helper/bwrap/seccomp-resolve.go
index 01df4dcc..860d720b 100644
--- a/helper/bwrap/seccomp-resolve.go
+++ b/helper/bwrap/seccomp-resolve.go
@@ -2,9 +2,9 @@ package bwrap
 
 import (
 	"fmt"
-	"io"
 	"os"
 
+	"git.gensokyo.uk/security/fortify/helper/seccomp"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
 )
 
@@ -53,24 +53,24 @@ func (c *Config) resolveSeccomp() (*os.File, error) {
 
 	// resolve seccomp filter opts
 	var (
-		opts    syscallOpts
+		opts    seccomp.SyscallOpts
 		optd    []string
 		optCond = [...]struct {
 			v bool
-			o syscallOpts
+			o seccomp.SyscallOpts
 			d string
 		}{
-			{!c.Syscall.Compat, flagExt, "fortify"},
-			{!c.UserNS, flagDenyNS, "denyns"},
-			{c.NewSession, flagDenyTTY, "denytty"},
-			{c.Syscall.DenyDevel, flagDenyDevel, "denydevel"},
-			{c.Syscall.Multiarch, flagMultiarch, "multiarch"},
-			{c.Syscall.Linux32, flagLinux32, "linux32"},
-			{c.Syscall.Can, flagCan, "can"},
-			{c.Syscall.Bluetooth, flagBluetooth, "bluetooth"},
+			{!c.Syscall.Compat, seccomp.FlagExt, "fortify"},
+			{!c.UserNS, seccomp.FlagDenyNS, "denyns"},
+			{c.NewSession, seccomp.FlagDenyTTY, "denytty"},
+			{c.Syscall.DenyDevel, seccomp.FlagDenyDevel, "denydevel"},
+			{c.Syscall.Multiarch, seccomp.FlagMultiarch, "multiarch"},
+			{c.Syscall.Linux32, seccomp.FlagLinux32, "linux32"},
+			{c.Syscall.Can, seccomp.FlagCan, "can"},
+			{c.Syscall.Bluetooth, seccomp.FlagBluetooth, "bluetooth"},
 		}
 	)
-	if CPrintln != nil {
+	if seccomp.CPrintln != nil {
 		optd = make([]string, 1, len(optCond)+1)
 		optd[0] = "common"
 	}
@@ -82,22 +82,9 @@ func (c *Config) resolveSeccomp() (*os.File, error) {
 			}
 		}
 	}
-	if CPrintln != nil {
-		CPrintln(fmt.Sprintf("seccomp flags: %s", optd))
+	if seccomp.CPrintln != nil {
+		seccomp.CPrintln(fmt.Sprintf("seccomp flags: %s", optd))
 	}
 
-	// export seccomp filter to tmpfile
-	if f, err := tmpfile(); err != nil {
-		return nil, err
-	} else {
-		return f, exportAndSeek(f, opts)
-	}
-}
-
-func exportAndSeek(f *os.File, opts syscallOpts) error {
-	if err := exportFilter(f.Fd(), opts); err != nil {
-		return err
-	}
-	_, err := f.Seek(0, io.SeekStart)
-	return err
+	return seccomp.Export(opts)
 }
diff --git a/helper/bwrap/seccomp.go b/helper/bwrap/seccomp.go
deleted file mode 100644
index f77abc66..00000000
--- a/helper/bwrap/seccomp.go
+++ /dev/null
@@ -1,84 +0,0 @@
-package bwrap
-
-/*
-#cgo linux pkg-config: --static libseccomp
-
-#include "seccomp-export.h"
-*/
-import "C"
-import (
-	"errors"
-	"fmt"
-	"os"
-	"runtime"
-)
-
-var CPrintln func(v ...any)
-
-var resErr = [...]error{
-	0: nil,
-	1: errors.New("seccomp_init failed"),
-	2: errors.New("seccomp_arch_add failed"),
-	3: errors.New("seccomp_arch_add failed (multiarch)"),
-	4: errors.New("internal libseccomp failure"),
-	5: errors.New("seccomp_rule_add failed"),
-	6: errors.New("seccomp_export_bpf failed"),
-}
-
-type (
-	syscallOpts = C.f_syscall_opts
-)
-
-const (
-	flagExt       syscallOpts = C.F_EXT
-	flagDenyNS    syscallOpts = C.F_DENY_NS
-	flagDenyTTY   syscallOpts = C.F_DENY_TTY
-	flagDenyDevel syscallOpts = C.F_DENY_DEVEL
-	flagMultiarch syscallOpts = C.F_MULTIARCH
-	flagLinux32   syscallOpts = C.F_LINUX32
-	flagCan       syscallOpts = C.F_CAN
-	flagBluetooth syscallOpts = C.F_BLUETOOTH
-)
-
-func tmpfile() (*os.File, error) {
-	fd, err := C.f_tmpfile_fd()
-	if err != nil {
-		return nil, err
-	}
-	return os.NewFile(uintptr(fd), "tmpfile"), err
-}
-
-func exportFilter(fd uintptr, opts syscallOpts) error {
-	var (
-		arch      C.uint32_t = 0
-		multiarch C.uint32_t = 0
-	)
-	switch runtime.GOARCH {
-	case "386":
-		arch = C.SCMP_ARCH_X86
-	case "amd64":
-		arch = C.SCMP_ARCH_X86_64
-		multiarch = C.SCMP_ARCH_X86
-	case "arm":
-		arch = C.SCMP_ARCH_ARM
-	case "arm64":
-		arch = C.SCMP_ARCH_AARCH64
-		multiarch = C.SCMP_ARCH_ARM
-	}
-
-	res, err := C.f_export_bpf(C.int(fd), arch, multiarch, opts)
-	if re := resErr[res]; re != nil {
-		if err == nil {
-			return re
-		}
-		return fmt.Errorf("%s: %v", re.Error(), err)
-	}
-	return err
-}
-
-//export F_println
-func F_println(v *C.char) {
-	if CPrintln != nil {
-		CPrintln(C.GoString(v))
-	}
-}