vendor/github.com/moby/buildkit/util/entitlements/security/security_linux.go

package security

import (
	"context"
	"fmt"
	"os"

	"github.com/containerd/containerd/containers"
	"github.com/containerd/containerd/oci"
	"github.com/containerd/containerd/sys"
	specs "github.com/opencontainers/runtime-spec/specs-go"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
	"golang.org/x/sys/unix"
)

// WithInsecureSpec sets spec with All capability.
func WithInsecureSpec() oci.SpecOpts {
	return func(_ context.Context, _ oci.Client, _ *containers.Container, s *specs.Spec) error {
		addCaps := []string{
			"CAP_FSETID",
			"CAP_KILL",
			"CAP_FOWNER",
			"CAP_MKNOD",
			"CAP_CHOWN",
			"CAP_DAC_OVERRIDE",
			"CAP_NET_RAW",
			"CAP_SETGID",
			"CAP_SETUID",
			"CAP_SETPCAP",
			"CAP_SETFCAP",
			"CAP_NET_BIND_SERVICE",
			"CAP_SYS_CHROOT",
			"CAP_AUDIT_WRITE",
			"CAP_MAC_ADMIN",
			"CAP_MAC_OVERRIDE",
			"CAP_DAC_READ_SEARCH",
			"CAP_SYS_PTRACE",
			"CAP_SYS_MODULE",
			"CAP_SYSLOG",
			"CAP_SYS_RAWIO",
			"CAP_SYS_ADMIN",
			"CAP_LINUX_IMMUTABLE",
			"CAP_SYS_BOOT",
			"CAP_SYS_NICE",
			"CAP_SYS_PACCT",
			"CAP_SYS_TTY_CONFIG",
			"CAP_SYS_TIME",
			"CAP_WAKE_ALARM",
			"CAP_AUDIT_READ",
			"CAP_AUDIT_CONTROL",
			"CAP_SYS_RESOURCE",
			"CAP_BLOCK_SUSPEND",
			"CAP_IPC_LOCK",
			"CAP_IPC_OWNER",
			"CAP_LEASE",
			"CAP_NET_ADMIN",
			"CAP_NET_BROADCAST",
		}
		for _, cap := range addCaps {
			s.Process.Capabilities.Bounding = append(s.Process.Capabilities.Bounding, cap)
			s.Process.Capabilities.Ambient = append(s.Process.Capabilities.Ambient, cap)
			s.Process.Capabilities.Effective = append(s.Process.Capabilities.Effective, cap)
			s.Process.Capabilities.Inheritable = append(s.Process.Capabilities.Inheritable, cap)
			s.Process.Capabilities.Permitted = append(s.Process.Capabilities.Permitted, cap)
		}
		s.Linux.ReadonlyPaths = []string{}
		s.Linux.MaskedPaths = []string{}
		s.Process.ApparmorProfile = ""

		s.Linux.Resources.Devices = []specs.LinuxDeviceCgroup{
			{
				Allow:  true,
				Type:   "c",
				Access: "rwm",
			},
			{
				Allow:  true,
				Type:   "b",
				Access: "rwm",
			},
		}

		if !sys.RunningInUserNS() {
			// Devices automatically mounted on insecure mode
			s.Linux.Devices = append(s.Linux.Devices, []specs.LinuxDevice{
				// Writes to this come out as printk's, reads export the buffered printk records. (dmesg)
				{
					Path:  "/dev/kmsg",
					Type:  "c",
					Major: 1,
					Minor: 11,
				},
				// Cuse (character device in user-space)
				{
					Path:  "/dev/cuse",
					Type:  "c",
					Major: 10,
					Minor: 203,
				},
				// Fuse (virtual filesystem in user-space)
				{
					Path:  "/dev/fuse",
					Type:  "c",
					Major: 10,
					Minor: 229,
				},
				// Kernel-based virtual machine (hardware virtualization extensions)
				{
					Path:  "/dev/kvm",
					Type:  "c",
					Major: 10,
					Minor: 232,
				},
				// TAP/TUN network device
				{
					Path:  "/dev/net/tun",
					Type:  "c",
					Major: 10,
					Minor: 200,
				},
				// Loopback control device
				{
					Path:  "/dev/loop-control",
					Type:  "c",
					Major: 10,
					Minor: 237,
				},
			}...)

			loopID, err := getFreeLoopID()
			if err != nil {
				logrus.Debugf("failed to get next free loop device: %v", err)
			}

			for i := 0; i <= loopID+7; i++ {
				s.Linux.Devices = append(s.Linux.Devices, specs.LinuxDevice{
					Path:  fmt.Sprintf("/dev/loop%d", i),
					Type:  "b",
					Major: 7,
					Minor: int64(i),
				})
			}
		}

		return nil
	}
}

func getFreeLoopID() (int, error) {
	fd, err := os.OpenFile("/dev/loop-control", os.O_RDWR, 0644)
	if err != nil {
		return 0, err
	}
	defer fd.Close()

	const _LOOP_CTL_GET_FREE = 0x4C82
	r1, _, uerr := unix.Syscall(unix.SYS_IOCTL, fd.Fd(), _LOOP_CTL_GET_FREE, 0)
	if uerr == 0 {
		return int(r1), nil
	}
	return 0, errors.Errorf("error getting free loop device: %v", uerr)
}