selinux/

lib.rs

// Copyright 2024 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

pub mod permission_check;
pub mod policy;
pub mod security_server;

pub use security_server::SecurityServer;

mod access_vector_cache;
mod sid_table;
mod sync;

use policy::arrays::FsUseType;

use std::num::NonZeroU32;

/// The Security ID (SID) used internally to refer to a security context.
#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
pub struct SecurityId(NonZeroU32);

impl SecurityId {
    /// Returns a `SecurityId` encoding the specified initial Security Context.
    /// These are used when labeling kernel resources created before policy
    /// load, allowing the policy to determine the Security Context to use.
    pub fn initial(initial_sid: InitialSid) -> Self {
        Self(NonZeroU32::new(initial_sid as u32).unwrap())
    }
}

/// A class that may appear in SELinux policy or an access vector cache query.
#[derive(Clone, Debug, PartialEq)]
pub enum AbstractObjectClass {
    Unspecified,
    /// A well-known class used in the SELinux system, such as `process` or `file`.
    System(ObjectClass),
    /// A custom class that only has meaning in policies that define class with the given string
    /// name.
    Custom(String),
}

impl Default for AbstractObjectClass {
    fn default() -> Self {
        Self::Unspecified
    }
}

/// Declares an `enum` and implements an `all_variants()` API for it.
macro_rules! enumerable_enum {
    ($(#[$meta:meta])* $name:ident $(extends $common_name:ident)? {
        $($(#[$variant_meta:meta])* $variant:ident,)*
    }) => {
        $(#[$meta])*
        pub enum $name {
            $($(#[$variant_meta])* $variant,)*
            $(Common($common_name),)?
        }

        impl $name {
            pub fn all_variants() -> Vec<Self> {
                let all_variants = vec![$($name::$variant),*];
                $(let mut all_variants = all_variants; all_variants.extend($common_name::all_variants().into_iter().map(Self::Common));)?
                all_variants
            }
        }
    }
}

enumerable_enum! {
    /// A well-known class in SELinux policy that has a particular meaning in policy enforcement
    /// hooks.
    #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
    ObjectClass {
        // keep-sorted start
        /// The SELinux "blk_file" object class.
        Block,
        /// The SELinux "chr_file" object class.
        Character,
        /// The SELinux "dir" object class.
        Dir,
        /// The SELinux "fd" object class.
        Fd,
        /// The SELinux "fifo_file" object class.
        Fifo,
        /// The SELinux "file" object class.
        File,
        /// The SELinux "filesystem" object class.
        FileSystem,
        /// The SELinux "lnk_file" object class.
        Link,
        /// The SELinux "process" object class.
        Process,
        /// The SELinux "security" object class.
        Security,
        /// The SELinux "sock_file" object class.
        Socket,
        // keep-sorted end
    }
}

impl ObjectClass {
    /// Returns the name used to refer to this object class in the SELinux binary policy.
    pub fn name(&self) -> &'static str {
        match self {
            // keep-sorted start
            Self::Block => "blk_file",
            Self::Character => "chr_file",
            Self::Dir => "dir",
            Self::Fd => "fd",
            Self::Fifo => "fifo_file",
            Self::File => "file",
            Self::FileSystem => "filesystem",
            Self::Link => "lnk_file",
            Self::Process => "process",
            Self::Security => "security",
            Self::Socket => "sock_file",
            // keep-sorted end
        }
    }
}

impl From<ObjectClass> for AbstractObjectClass {
    fn from(object_class: ObjectClass) -> Self {
        Self::System(object_class)
    }
}

impl From<String> for AbstractObjectClass {
    fn from(name: String) -> Self {
        Self::Custom(name)
    }
}

enumerable_enum! {
    /// A well-known file-like class in SELinux policy that has a particular meaning in policy
    /// enforcement hooks.
    #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
    FileClass {
        // keep-sorted start
        /// The SELinux "blk_file" object class.
        Block,
        /// The SELinux "chr_file" object class.
        Character,
        /// The SELinux "dir" object class.
        Dir,
        /// The SELinux "fifo_file" object class.
        Fifo,
        /// The SELinux "file" object class.
        File,
        /// The SELinux "lnk_file" object class.
        Link,
        /// The SELinux "sock_file" object class.
        Socket,
        // keep-sorted end
    }
}

impl From<FileClass> for ObjectClass {
    fn from(file_class: FileClass) -> Self {
        match file_class {
            // keep-sorted start
            FileClass::Block => Self::Block,
            FileClass::Character => Self::Character,
            FileClass::Dir => Self::Dir,
            FileClass::Fifo => Self::Fifo,
            FileClass::File => Self::File,
            FileClass::Link => Self::Link,
            FileClass::Socket => Self::Socket,
            // keep-sorted end
        }
    }
}

/// A permission that may appear in SELinux policy or an access vector cache query.
#[derive(Clone, Debug, PartialEq)]
pub enum AbstractPermission {
    /// A permission that is interpreted directly by the system. These are kernel objects such as
    /// a "process", "file", etc.
    System(Permission),
    /// A permission with an arbitrary string identifier.
    Custom { class: AbstractObjectClass, permission: String },
}

impl AbstractPermission {
    pub fn new_custom(class: AbstractObjectClass, permission: String) -> Self {
        Self::Custom { class, permission }
    }
}

impl From<Permission> for AbstractPermission {
    fn from(permission: Permission) -> Self {
        Self::System(permission)
    }
}

pub trait ClassPermission {
    fn class(&self) -> ObjectClass;
}

macro_rules! permission_enum {
    ($(#[$meta:meta])* $name:ident {
        $($(#[$variant_meta:meta])* $variant:ident($inner:ident)),*,
    }) => {
        $(#[$meta])*
        pub enum $name {
            $($(#[$variant_meta])* $variant($inner)),*
        }

        $(impl From<$inner> for $name {
            fn from(v: $inner) -> Self {
                Self::$variant(v)
            }
        })*

        impl ClassPermission for $name {
            fn class(&self) -> ObjectClass {
                match self {
                    $($name::$variant(_) => ObjectClass::$variant),*
                }
            }
        }

        impl $name {
            pub fn name(&self) -> &'static str {
                match self {
                    $($name::$variant(v) => v.name()),*
                }
            }

            pub fn all_variants() -> Vec<Self> {
                let mut all_variants = vec![];
                $(all_variants.extend($inner::all_variants().into_iter().map($name::from));)*
                all_variants
            }
        }
    }
}

permission_enum! {
    /// A well-known `(class, permission)` pair in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    Permission {
        // keep-sorted start
        /// Permissions for the well-known SELinux "blk_file" file-like object class.
        Block(BlockFilePermission),
        /// Permissions for the well-known SELinux "chr_file" file-like object class.
        Character(CharacterFilePermission),
        /// Permissions for the well-known SELinux "dir" file-like object class.
        Dir(DirPermission),
        /// Permissions for the well-known SELinux "fd" object class.
        Fd(FdPermission),
        /// Permissions for the well-known SELinux "fifo_file" file-like object class.
        Fifo(FifoFilePermission),
        /// Permissions for the well-known SELinux "file" object class.
        File(FilePermission),
        /// Permissions for the well-known SELinux "filesystem" object class.
        FileSystem(FileSystemPermission),
        /// Permissions for the well-known SELinux "lnk_file" file-like object class.
        Link(LinkFilePermission),
        /// Permissions for the well-known SELinux "process" object class.
        Process(ProcessPermission),
        /// Permissions for access to parts of the "selinuxfs" used to administer and query SELinux.
        Security(SecurityPermission),
        /// Permissions for the well-known SELinux "sock_file" file-like object class.
        Socket(SocketPermission),
        // keep-sorted end
    }
}

/// Helper used to define an enum of permission values, with specified names.
/// Uses of this macro should not rely on "extends", which is solely for use to express permission
/// inheritance in `class_permission_enum`.
macro_rules! common_permission_enum {
    ($(#[$meta:meta])* $name:ident $(extends $common_name:ident)? {
        $($(#[$variant_meta:meta])* $variant:ident ($variant_name:literal),)*
    }) => {
        enumerable_enum! {
            $(#[$meta])* $name $(extends $common_name)? {
                $($(#[$variant_meta])* $variant,)*
            }
        }

        impl $name {
            fn name(&self) -> &'static str {
                match self {
                    $($name::$variant => $variant_name,)*
                    $(Self::Common(v) => {let v:$common_name = v.clone(); v.name()},)?
                }
            }
        }
    }
}

/// Helper used to declare the set of named permissions associated with an SELinux class.
/// The `ClassType` trait is implemented on the declared `enum`, enabling values to be wrapped into
/// the generic `Permission` container.
/// If an "extends" type is specified then a `Common` enum case is added, encapsulating the values
/// of that underlying permission type. This is used to represent e.g. SELinux "dir" class deriving
/// a basic set of permissions from the common "file" symbol.
macro_rules! class_permission_enum {
    ($(#[$meta:meta])* $name:ident $(extends $common_name:ident)? {
        $($(#[$variant_meta:meta])* $variant:ident ($variant_name:literal),)*
    }) => {
        common_permission_enum! {
            $(#[$meta])* $name $(extends $common_name)? {
                $($(#[$variant_meta])* $variant ($variant_name),)*
            }
        }

        impl ClassPermission for $name {
            fn class(&self) -> ObjectClass {
                Permission::from(self.clone()).class()
            }
        }
    }
}

common_permission_enum! {
    /// Permissions common to all file-like object classes (e.g. "lnk_file", "dir"). These are
    /// combined with a specific `FileClass` by policy enforcement hooks, to obtain class-affine
    /// permission values to check.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    CommonFilePermission {
        // keep-sorted start
        /// Permission to append to a file.
        Append("append"),
        /// Permission to create a file.
        Create("create"),
        /// Permission to execute a file with domain transition.
        Execute("execute"),
        /// Permission to query attributes, including uid, gid and extended attributes.
        GetAttr("getattr"),
        /// Permission to execute ioctls on the file.
        Ioctl("ioctl"),
        /// Permissions to create hard link.
        Link("link"),
        /// Permission to use as mount point; only useful for directories and files.
        MountOn("mounton"),
        /// Permission to open a file.
        Open("open"),
        /// Permission to read file contents. Note this applies to reading more than regular file's
        /// data.
        Read("read"),
        /// Permission checked against the existing label when updating a file's security label.
        RelabelFrom("relabelfrom"),
        /// Permission checked against the new label when updating a file's security label.
        RelabelTo("relabelto"),
        /// Permission to rename a file.
        Rename("rename"),
        /// Permission to modify attributes, including uid, gid and extended attributes.
        SetAttr("setattr"),
        /// Permission to delete a file or remove a hard link.
        Unlink("unlink"),
        /// Permission to write or append file contents.
        Write("write"),
        // keep-sorted end
    }
}

impl CommonFilePermission {
    /// Returns the `class`-affine `Permission` value corresponding to this common permission.
    /// This is used to allow hooks to resolve e.g. common "read" permission access based on the
    /// "allow" rules for the correct target object class.
    pub fn for_class(&self, class: FileClass) -> Permission {
        match class {
            FileClass::Block => BlockFilePermission::Common(self.clone()).into(),
            FileClass::Character => CharacterFilePermission::Common(self.clone()).into(),
            FileClass::Dir => DirPermission::Common(self.clone()).into(),
            FileClass::Fifo => FifoFilePermission::Common(self.clone()).into(),
            FileClass::File => FilePermission::Common(self.clone()).into(),
            FileClass::Link => LinkFilePermission::Common(self.clone()).into(),
            FileClass::Socket => SocketPermission::Common(self.clone()).into(),
        }
    }
}

class_permission_enum! {
    /// A well-known "blk_file" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    BlockFilePermission extends CommonFilePermission {
    }
}

class_permission_enum! {
    /// A well-known "chr_file" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    CharacterFilePermission extends CommonFilePermission {
    }
}

class_permission_enum! {
    /// A well-known "dir" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    DirPermission extends CommonFilePermission {
        // keep-sorted start
        /// Permission to add a file to the directory.
        AddName("add_name"),
        /// Permission to remove a directory.
        RemoveDir("rmdir"),
        /// Permission to remove an entry from a directory.
        RemoveName("remove_name"),
        /// Permission to change parent directory.
        Reparent("reparent"),
        /// Search access to the directory.
        Search("search"),
        // keep-sorted end
    }
}

class_permission_enum! {
    /// A well-known "fd" class permission in SELinux policy that has a particular meaning in policy
    /// enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    FdPermission {
        // keep-sorted start
        /// Permission to use file descriptors copied/retained/inherited from another security
        /// context. This permission is generally used to control whether an `exec*()` call from a
        /// cloned process that retained a copy of the file descriptor table should succeed.
        Use("use"),
        // keep-sorted end
    }
}

class_permission_enum! {
    /// A well-known "fifo_file" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    FifoFilePermission extends CommonFilePermission {
    }
}

class_permission_enum! {
    /// A well-known "file" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    FilePermission extends CommonFilePermission {
        // keep-sorted start
        /// Permission to use a file as an entry point into the new domain on transition.
        Entrypoint("entrypoint"),
        /// Permission to use a file as an entry point to the calling domain without performing a
        /// transition.
        ExecuteNoTrans("execute_no_trans"),
        // keep-sorted end
    }
}

class_permission_enum! {
    /// A well-known "filesystem" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    FileSystemPermission {
        // keep-sorted start
        /// Permission to associate a file to the filesystem.
        Associate("associate"),
        /// Permission to get filesystem attributes.
        GetAttr("getattr"),
        /// Permission to remount a filesystem with different flags.
        Remount("remount"),
        /// Permission to unmount a filesystem.
        Unmount("unmount"),
        // keep-sorted end
    }
}

class_permission_enum! {
    /// A well-known "lnk_file" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    LinkFilePermission extends CommonFilePermission {
    }
}

class_permission_enum! {
    /// A well-known "process" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    ProcessPermission {
        // keep-sorted start
        /// Permission to dynamically transition a process to a different security domain.
        DynTransition("dyntransition"),
        /// Permission to fork the current running process.
        Fork("fork"),
        /// Permission to get the process group ID.
        GetPgid("getpgid"),
        /// Permission to get the resource limits on a process.
        GetRlimit("getrlimit"),
        /// Permission to get scheduling policy currently applied to a process.
        GetSched("getsched"),
        /// Permission to get the session ID.
        GetSession("getsession"),
        /// Permission to trace a process.
        Ptrace("ptrace"),
        /// Permission to set the calling task's current Security Context.
        /// The "dyntransition" permission separately limits which Contexts "setcurrent" may be used to transition to.
        SetCurrent("setcurrent"),
        /// Permission to set the Security Context used by `exec()`.
        SetExec("setexec"),
        /// Permission to set the Security Context used when creating filesystem objects.
        SetFsCreate("setfscreate"),
        /// Permission to set the Security Context used when creating kernel keyrings.
        SetKeyCreate("setkeycreate"),
        /// Permission to set the process group ID.
        SetPgid("setpgid"),
        /// Permission to set the resource limits on a process.
        SetRlimit("setrlimit"),
        /// Permission to set scheduling policy for a process.
        SetSched("setsched"),
        /// Permission to set the Security Context used when creating new labeled sockets.
        SetSockCreate("setsockcreate"),
        /// Permission to send SIGCHLD to a process.
        SigChld("sigchld"),
        /// Permission to send SIGKILL to a process.
        SigKill("sigkill"),
        /// Permission to send SIGSTOP to a process.
        SigStop("sigstop"),
        /// Permission to send a signal other than SIGKILL, SIGSTOP, or SIGCHLD to a process.
        Signal("signal"),
        /// Permission to transition to a different security domain.
        Transition("transition"),
        // keep-sorted end
    }
}

class_permission_enum! {
    /// A well-known "security" class permission in SELinux policy, used to control access to
    /// sensitive administrative and query API surfaces in the "selinuxfs".
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    SecurityPermission {
        // keep-sorted start
        /// Permission to validate Security Context using the "context" API.
        CheckContext("check_context"),
        /// Permission to compute access vectors via the "access" API.
        ComputeAv("compute_av"),
        /// Permission to compute security contexts for newly created objects via "create".
        ComputeCreate("compute_create"),
        /// Permission to load a new binary policy into the kernel via the "load" API.
        LoadPolicy("load_policy"),
        /// Permission to commit booleans to control conditional elements of the policy.
        SetBool("setbool"),
        /// Permission to change the way permissions are validated for `mmap()` operations.
        SetCheckReqProt("setcheckreqprot"),
        /// Permission to switch the system between permissive and enforcing modes, via "enforce".
        SetEnforce("setenforce"),
        // keep-sorted end
     }
}

class_permission_enum! {
    /// A well-known "sock_file" class permission in SELinux policy that has a particular meaning in
    /// policy enforcement hooks.
    #[derive(Clone, Debug, Eq, Hash, PartialEq)]
    SocketPermission extends CommonFilePermission {
    }
}

/// Initial Security Identifier (SID) values defined by the SELinux Reference Policy.
/// Where the SELinux Reference Policy retains definitions for some deprecated initial SIDs, this
/// enum omits deprecated entries for clarity.
#[repr(u64)]
enum ReferenceInitialSid {
    Kernel = 1,
    Security = 2,
    Unlabeled = 3,
    _Fs = 4,
    File = 5,
    _AnySocket = 6,
    _Port = 7,
    _Netif = 8,
    _Netmsg = 9,
    _Node = 10,
    _Sysctl = 15,
    _Devnull = 25,

    FirstUnused,
}

/// Lowest Security Identifier value guaranteed not to be used by this
/// implementation to refer to an initial Security Context.
pub const FIRST_UNUSED_SID: u32 = ReferenceInitialSid::FirstUnused as u32;

macro_rules! initial_sid_enum {
    ($(#[$meta:meta])* $name:ident {
        $($(#[$variant_meta:meta])* $variant:ident ($variant_name: literal)),*,
    }) => {
        $(#[$meta])*
        pub enum $name {
            $($(#[$variant_meta])* $variant = ReferenceInitialSid::$variant as isize),*
        }

        impl $name {
            pub fn all_variants() -> Vec<Self> {
                vec![
                    $($name::$variant),*
                ]
            }

            pub fn name(&self) -> &'static str {
                match self {
                    $($name::$variant => $variant_name),*
                }
            }
        }
    }
}

initial_sid_enum! {
/// Initial Security Identifier (SID) values actually used by this implementation.
/// These must be present in the policy, for it to be valid.
#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
    InitialSid {
        // keep-sorted start
        File("file"),
        Kernel("kernel"),
        Security("security"),
        Unlabeled("unlabeled"),
        // keep-sorted end
    }
}

/// A borrowed byte slice that contains no `NUL` characters by truncating the input slice at the
/// first `NUL` (if any) upon construction.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct NullessByteStr<'a>(&'a [u8]);

impl<'a> NullessByteStr<'a> {
    /// Returns a non-null-terminated representation of the security context string.
    pub fn as_bytes(&self) -> &[u8] {
        &self.0
    }
}

impl<'a, S: AsRef<[u8]> + ?Sized> From<&'a S> for NullessByteStr<'a> {
    /// Any `AsRef<[u8]>` can be processed into a [`NullessByteStr`]. The [`NullessByteStr`] will
    /// retain everything up to (but not including) a null character, or else the complete byte
    /// string.
    fn from(s: &'a S) -> Self {
        let value = s.as_ref();
        match value.iter().position(|c| *c == 0) {
            Some(end) => Self(&value[..end]),
            None => Self(value),
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct FileSystemLabel {
    pub sid: SecurityId,
    pub scheme: FileSystemLabelingScheme,
}

#[derive(Clone, Debug, PartialEq)]
pub enum FileSystemLabelingScheme {
    /// This filesystem was mounted with "context=".
    Mountpoint { sid: SecurityId },
    /// This filesystem has an "fs_use_xattr", "fs_use_task", or "fs_use_trans" entry in the
    /// policy. `root_sid` identifies the context for the root of the filesystem and `def_sid`
    /// identifies the context to use for unlabeled files in the filesystem (the "default
    /// context").
    FsUse { fs_use_type: FsUseType, def_sid: SecurityId, root_sid: SecurityId },
    /// This filesystem has one or more "genfscon" statements associated with it in the policy.
    GenFsCon,
}

/// SELinux security context-related filesystem mount options. These options are documented in the
/// `context=context, fscontext=context, defcontext=context, and rootcontext=context` section of
/// the `mount(8)` manpage.
#[derive(Clone, Debug, PartialEq)]
pub struct FileSystemMountOptions {
    /// Specifies the effective security context to use for all nodes in the filesystem, and the
    /// filesystem itself. If the filesystem already contains security attributes then these are
    /// ignored. May not be combined with any of the other options.
    pub context: Option<Vec<u8>>,
    /// Specifies an effective security context to use for un-labeled nodes in the filesystem,
    /// rather than falling-back to the policy-defined "file" context.
    pub def_context: Option<Vec<u8>>,
    /// The value of the `fscontext=[security-context]` mount option. This option is used to
    /// label the filesystem (superblock) itself.
    pub fs_context: Option<Vec<u8>>,
    /// The value of the `rootcontext=[security-context]` mount option. This option is used to
    /// (re)label the inode located at the filesystem mountpoint.
    pub root_context: Option<Vec<u8>>,
}

/// Status information parameter for the [`SeLinuxStatusPublisher`] interface.
pub struct SeLinuxStatus {
    /// SELinux-wide enforcing vs. permissive mode  bit.
    pub is_enforcing: bool,
    /// Number of times the policy has been changed since SELinux started.
    pub change_count: u32,
    /// Bit indicating whether operations unknown SELinux abstractions will be denied.
    pub deny_unknown: bool,
}

/// Interface for security server to interact with selinuxfs status file.
pub trait SeLinuxStatusPublisher: Send {
    /// Sets the value part of the associated selinuxfs status file.
    fn set_status(&mut self, policy_status: SeLinuxStatus);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn object_class_permissions() {
        assert_eq!(AbstractObjectClass::Unspecified, AbstractObjectClass::default());
        assert_eq!(
            AbstractObjectClass::Custom(String::from("my_class")),
            String::from("my_class").into()
        );
        for variant in ProcessPermission::all_variants().into_iter() {
            assert_eq!(ObjectClass::Process, variant.class());
            assert_eq!("process", variant.class().name());
            let permission: Permission = variant.clone().into();
            assert_eq!(Permission::Process(variant.clone()), permission);
            assert_eq!(
                AbstractPermission::System(Permission::Process(variant.clone())),
                permission.into()
            );
            assert_eq!(AbstractObjectClass::System(ObjectClass::Process), variant.class().into());
        }
    }

    #[test]
    fn nulless_byte_str_equivalence() {
        let unterminated: NullessByteStr<'_> = b"u:object_r:test_valid_t:s0".into();
        let nul_terminated: NullessByteStr<'_> = b"u:object_r:test_valid_t:s0\0".into();
        let nul_containing: NullessByteStr<'_> =
            b"u:object_r:test_valid_t:s0\0IGNORE THIS\0!\0".into();

        for context in [nul_terminated, nul_containing] {
            assert_eq!(unterminated, context);
            assert_eq!(unterminated.as_bytes(), context.as_bytes());
        }
    }
}