haematite-cli 0.21.1

//! Private runtime endpoints derived from the operating system and store name.

use std::fmt;
use std::fs::{self, DirBuilder, Metadata, OpenOptions};
use std::io;
use std::os::unix::ffi::OsStrExt;
use std::os::unix::fs::{DirBuilderExt, MetadataExt, OpenOptionsExt, PermissionsExt};
use std::os::unix::net::SocketAddr;
use std::path::{Component, Path, PathBuf};
use std::sync::atomic::{AtomicU64, Ordering};

use sha2::{Digest, Sha256};

static PROBES: AtomicU64 = AtomicU64::new(0);

#[derive(Debug)]
pub struct Refusal {
    pub code: &'static str,
    detail: String,
}

impl Refusal {
    fn new(code: &'static str, detail: impl fmt::Display) -> Self {
        Self {
            code,
            detail: detail.to_string(),
        }
    }
}

impl fmt::Display for Refusal {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(formatter, "{}: {}", self.code, self.detail)
    }
}

impl std::error::Error for Refusal {}

#[derive(Debug)]
pub struct Endpoint {
    pub name: String,
    pub socket: PathBuf,
    pub data_dir: PathBuf,
}

impl Endpoint {
    /// Refuses a created store whose canonical location changed during creation.
    ///
    /// # Errors
    /// Returns `data_dir_changed` if the created directory cannot be checked or changed location.
    pub fn check_created(&self) -> Result<(), Refusal> {
        let actual = fs::canonicalize(&self.data_dir)
            .map_err(|error| Refusal::new("data_dir_changed", error))?;
        let metadata =
            fs::metadata(&actual).map_err(|error| Refusal::new("data_dir_changed", error))?;
        if actual != self.data_dir || !metadata.is_dir() {
            return Err(Refusal::new(
                "data_dir_changed",
                "created store location changed",
            ));
        }
        Ok(())
    }
}

/// Resolves one endpoint without opening a store or binding a socket.
///
/// # Errors
/// Names invalid store names, data locations, runtime locations and endpoints,
/// unavailable OS queries, uid-probe failures and probe-cleanup failures.
pub fn resolve(
    data_dir: &Path,
    name: Option<&str>,
    socket: Option<&Path>,
    create: bool,
) -> Result<Endpoint, Refusal> {
    resolve_with(data_dir, name, socket, create, os_root, probe_uid)
}

fn resolve_with(
    data_dir: &Path,
    name: Option<&str>,
    socket: Option<&Path>,
    create: bool,
    root: impl FnOnce() -> Result<PathBuf, Refusal>,
    uid: impl FnOnce(&Path) -> Result<u32, Refusal>,
) -> Result<Endpoint, Refusal> {
    if let Some(name) = name {
        validate_name(name)?;
    }
    let data_dir = canonical_data(data_dir, create)?;
    let name = match name {
        Some(name) => name.to_owned(),
        None => data_dir
            .file_name()
            .and_then(|name| name.to_str())
            .ok_or_else(|| {
                Refusal::new(
                    "invalid_store_name",
                    "data directory needs a UTF-8 basename",
                )
            })?
            .to_owned(),
    };
    validate_name(&name)?;
    if let Some(socket) = socket {
        check_endpoint(socket)?;
        let parent = socket
            .parent()
            .ok_or_else(|| Refusal::new("invalid_socket", "endpoint needs a parent"))?;
        let metadata = private_directory(parent)?;
        let owner = uid(parent)?;
        check_identity(parent, &metadata, owner)?;
        return Ok(Endpoint {
            name,
            socket: socket.to_path_buf(),
            data_dir,
        });
    }
    let root = root()?;
    let metadata = private_directory(&root)?;
    let namespace = root.join("haem");
    let socket = namespace.join(filename(&name));
    check_endpoint(&socket)?;
    let owner = uid(&root)?;
    check_identity(&root, &metadata, owner)?;
    match DirBuilder::new().mode(0o700).create(&namespace) {
        Ok(()) => {}
        Err(error) if error.kind() == io::ErrorKind::AlreadyExists => {}
        Err(error) => return Err(Refusal::new("invalid_runtime_location", error)),
    }
    let namespace_metadata = private_directory(&namespace)?;
    check_identity(&namespace, &namespace_metadata, owner)?;
    check_identity(&root, &metadata, owner)?;
    Ok(Endpoint {
        name,
        socket,
        data_dir,
    })
}

fn canonical_data(data: &Path, create: bool) -> Result<PathBuf, Refusal> {
    if !data.is_absolute() {
        return Err(Refusal::new(
            "invalid_data_dir",
            "data directory must be absolute",
        ));
    }
    if create {
        let Some(Component::Normal(name)) = data.components().next_back() else {
            return Err(Refusal::new(
                "invalid_data_dir",
                "creation needs a normal final component",
            ));
        };
        if name.to_str().is_none() {
            return Err(Refusal::new(
                "invalid_store_name",
                "creation needs a UTF-8 final component",
            ));
        }
        let parent = data
            .parent()
            .ok_or_else(|| Refusal::new("invalid_data_dir", "creation needs an existing parent"))?;
        let parent =
            fs::canonicalize(parent).map_err(|error| Refusal::new("invalid_data_dir", error))?;
        let metadata =
            fs::metadata(&parent).map_err(|error| Refusal::new("invalid_data_dir", error))?;
        if !metadata.is_dir() {
            return Err(Refusal::new(
                "invalid_data_dir",
                "creation parent is not a directory",
            ));
        }
        Ok(parent.join(name))
    } else {
        let canonical =
            fs::canonicalize(data).map_err(|error| Refusal::new("invalid_data_dir", error))?;
        let metadata =
            fs::metadata(&canonical).map_err(|error| Refusal::new("invalid_data_dir", error))?;
        if !metadata.is_dir() {
            return Err(Refusal::new("invalid_data_dir", "store is not a directory"));
        }
        Ok(canonical)
    }
}

fn validate_name(name: &str) -> Result<(), Refusal> {
    if name.is_empty()
        || name.len() > 128
        || matches!(name, "." | "..")
        || name.contains(['/', '\\', '\0'])
    {
        return Err(Refusal::new(
            "invalid_store_name",
            "name must be 1 to 128 UTF-8 bytes without separators or NUL",
        ));
    }
    Ok(())
}

fn check_endpoint(socket: &Path) -> Result<(), Refusal> {
    if !socket.is_absolute() || socket.as_os_str().as_bytes().contains(&0) {
        return Err(Refusal::new(
            "invalid_socket",
            "endpoint must be an absolute path without NUL",
        ));
    }
    SocketAddr::from_pathname(socket).map_err(|error| Refusal::new("endpoint_too_long", error))?;
    Ok(())
}

fn private_directory(path: &Path) -> Result<Metadata, Refusal> {
    if !path.is_absolute() {
        return Err(Refusal::new(
            "invalid_runtime_location",
            "runtime directory must be absolute",
        ));
    }
    let metadata = fs::symlink_metadata(path)
        .map_err(|error| Refusal::new("invalid_runtime_location", error))?;
    if !metadata.is_dir() || metadata.permissions().mode() & 0o7777 != 0o700 {
        return Err(Refusal::new(
            "invalid_runtime_location",
            "runtime directory must be a non-symlink directory with mode 0700",
        ));
    }
    Ok(metadata)
}

fn check_identity(path: &Path, expected: &Metadata, owner: u32) -> Result<(), Refusal> {
    let actual = private_directory(path)?;
    if actual.uid() != owner || (actual.dev(), actual.ino()) != (expected.dev(), expected.ino()) {
        return Err(Refusal::new(
            "invalid_runtime_location",
            "runtime directory owner or identity changed",
        ));
    }
    Ok(())
}

fn probe_uid(root: &Path) -> Result<u32, Refusal> {
    let sequence = PROBES
        .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |value| {
            value.checked_add(1)
        })
        .map_err(|error| Refusal::new("runtime_uid_unavailable", error))?;
    let path = root.join(format!(".haem-uid-{}-{sequence}", std::process::id()));
    let file = OpenOptions::new()
        .write(true)
        .create_new(true)
        .mode(0o600)
        .open(&path)
        .map_err(|error| Refusal::new("runtime_uid_unavailable", error))?;
    let metadata = file.metadata();
    let cleanup = fs::remove_file(&path);
    drop(file);
    finish_probe(metadata, cleanup)
}

fn finish_probe(metadata: io::Result<Metadata>, cleanup: io::Result<()>) -> Result<u32, Refusal> {
    match (metadata, cleanup) {
        (Ok(metadata), Ok(())) => {
            if !metadata.is_file() || metadata.permissions().mode() & 0o7777 != 0o600 {
                return Err(Refusal::new(
                    "runtime_uid_unavailable",
                    "uid probe must be a regular mode-0600 file",
                ));
            }
            Ok(metadata.uid())
        }
        (Err(error), Ok(())) => Err(Refusal::new("runtime_uid_unavailable", error)),
        (Ok(_), Err(error)) => Err(Refusal::new("runtime_cleanup_failed", error)),
        (Err(read), Err(cleanup)) => Err(Refusal::new(
            "runtime_cleanup_failed",
            format!("uid read: {read}; probe removal: {cleanup}"),
        )),
    }
}

fn filename(name: &str) -> String {
    const ALPHABET: &[u8; 64] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
    let mut encoded = String::with_capacity(43);
    let mut pending = 0_u16;
    let mut bits = 0_u32;
    for byte in Sha256::digest(name.as_bytes()) {
        pending = ((pending & ((1 << bits) - 1)) << 8) | u16::from(byte);
        bits += 8;
        while bits >= 6 {
            bits -= 6;
            encoded.push(char::from(ALPHABET[usize::from((pending >> bits) & 63)]));
        }
    }
    if bits != 0 {
        encoded.push(char::from(
            ALPHABET[usize::from((pending << (6 - bits)) & 63)],
        ));
    }
    encoded
}

#[cfg(target_os = "linux")]
fn os_root() -> Result<PathBuf, Refusal> {
    linux_root(std::env::var_os("XDG_RUNTIME_DIR"))
}

#[cfg(target_os = "macos")]
fn os_root() -> Result<PathBuf, Refusal> {
    getconf_root(
        std::process::Command::new("/usr/bin/getconf")
            .arg("DARWIN_USER_TEMP_DIR")
            .output(),
    )
}

#[cfg(not(any(target_os = "linux", target_os = "macos")))]
fn os_root() -> Result<PathBuf, Refusal> {
    Err(Refusal::new(
        "runtime_location_unavailable",
        "platform has no supported OS runtime query",
    ))
}

#[cfg(any(target_os = "linux", test))]
fn linux_root(input: Option<std::ffi::OsString>) -> Result<PathBuf, Refusal> {
    let input = input.filter(|value| !value.is_empty()).ok_or_else(|| {
        Refusal::new(
            "runtime_location_unavailable",
            "XDG_RUNTIME_DIR is unavailable",
        )
    })?;
    let path = PathBuf::from(input);
    if !path.is_absolute() || path.to_str().is_none() || path.as_os_str().as_bytes().contains(&0) {
        return Err(Refusal::new(
            "invalid_runtime_location",
            "XDG_RUNTIME_DIR is not an absolute runtime path",
        ));
    }
    Ok(path)
}

#[cfg(any(target_os = "macos", test))]
fn getconf_root(input: io::Result<std::process::Output>) -> Result<PathBuf, Refusal> {
    let output = input.map_err(|error| Refusal::new("runtime_location_unavailable", error))?;
    if !output.status.success() {
        return Err(Refusal::new(
            "runtime_location_unavailable",
            format!("OS runtime query exited {}", output.status),
        ));
    }
    let output = std::str::from_utf8(&output.stdout)
        .map_err(|error| Refusal::new("invalid_runtime_location", error))?;
    let output = output.strip_suffix('\n').map_or(output, |path| path);
    if output.is_empty() {
        return Err(Refusal::new(
            "runtime_location_unavailable",
            "OS runtime query returned no path",
        ));
    }
    if output.contains(['\n', '\r', '\0']) || !Path::new(output).is_absolute() {
        return Err(Refusal::new(
            "invalid_runtime_location",
            "OS runtime query needs one absolute UTF-8 path",
        ));
    }
    Ok(PathBuf::from(output))
}

#[cfg(test)]
pub(crate) fn resolve_input(
    data_dir: &Path,
    name: Option<&str>,
    socket: Option<&Path>,
    create: bool,
    root: &Path,
    uid: u32,
) -> Result<Endpoint, Refusal> {
    resolve_with(
        data_dir,
        name,
        socket,
        create,
        || Ok(root.to_path_buf()),
        |_| Ok(uid),
    )
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::os::unix::process::ExitStatusExt;

    type TestResult = Result<(), Box<dyn std::error::Error>>;

    fn fixture() -> Result<tempfile::TempDir, std::io::Error> {
        // A short, owned root keeps valid-endpoint fixtures below the socket-path bound.
        let directory = tempfile::Builder::new().prefix("r").tempdir_in("/tmp")?;
        fs::set_permissions(directory.path(), fs::Permissions::from_mode(0o700))?;
        Ok(directory)
    }

    fn query(bytes: &[u8], status: i32) -> std::process::Output {
        std::process::Output {
            status: std::process::ExitStatus::from_raw(status),
            stdout: bytes.to_vec(),
            stderr: Vec::new(),
        }
    }

    fn injected(
        root: &Path,
        uid: u32,
        data: &Path,
        name: Option<&str>,
        socket: Option<&Path>,
        create: bool,
    ) -> Result<Endpoint, Refusal> {
        resolve_with(
            data,
            name,
            socket,
            create,
            || Ok(root.to_path_buf()),
            |_| Ok(uid),
        )
    }

    #[test]
    fn unavailable_os_queries_are_named() -> TestResult {
        assert_eq!(
            linux_root(None).err().ok_or("accepted missing root")?.code,
            "runtime_location_unavailable"
        );
        let missing = io::Error::new(io::ErrorKind::NotFound, "missing query");
        assert_eq!(
            getconf_root(Err(missing))
                .err()
                .ok_or("accepted missing query")?
                .code,
            "runtime_location_unavailable"
        );
        assert_eq!(
            getconf_root(Ok(query(b"ignored\n", 256)))
                .err()
                .ok_or("accepted failed query")?
                .code,
            "runtime_location_unavailable"
        );
        for bytes in [b"".as_slice(), b"\n"] {
            assert_eq!(
                getconf_root(Ok(query(bytes, 0)))
                    .err()
                    .ok_or("accepted empty query")?
                    .code,
                "runtime_location_unavailable"
            );
        }
        Ok(())
    }

    #[test]
    fn query_output_requires_one_absolute_utf8_path() -> TestResult {
        for bytes in [
            b"relative\n".as_slice(),
            b"\xff\n",
            b"/one\n/two\n",
            b"/one\0\n",
        ] {
            assert_eq!(
                getconf_root(Ok(query(bytes, 0)))
                    .err()
                    .ok_or("accepted invalid query output")?
                    .code,
                "invalid_runtime_location"
            );
        }
        assert_eq!(
            getconf_root(Ok(query(b"/private/runtime/\n", 0)))?,
            PathBuf::from("/private/runtime/")
        );
        Ok(())
    }

    #[test]
    fn root_refusals_leave_no_namespace() -> TestResult {
        let directory = fixture()?;
        let root = directory.path();
        let uid = fs::metadata(root)?.uid();
        let data = root.join("store");
        fs::create_dir(&data)?;
        for candidate in [PathBuf::from("relative"), root.join("missing")] {
            assert_eq!(
                injected(&candidate, uid, &data, None, None, false)
                    .err()
                    .ok_or("accepted invalid root")?
                    .code,
                "invalid_runtime_location"
            );
        }
        let wrong_uid = uid.checked_add(1).ok_or("uid overflow")?;
        assert_eq!(
            injected(root, wrong_uid, &data, None, None, false)
                .err()
                .ok_or("accepted foreign owner")?
                .code,
            "invalid_runtime_location"
        );
        for mode in [0o720, 0o702, 0o755] {
            fs::set_permissions(root, fs::Permissions::from_mode(mode))?;
            assert_eq!(
                injected(root, uid, &data, None, None, false)
                    .err()
                    .ok_or("accepted nonprivate root")?
                    .code,
                "invalid_runtime_location"
            );
            assert!(!root.join("haem").try_exists()?);
        }
        fs::set_permissions(root, fs::Permissions::from_mode(0o700))?;
        let link = root.join("substituted");
        std::os::unix::fs::symlink(root, &link)?;
        assert_eq!(
            injected(&link, uid, &data, None, None, false)
                .err()
                .ok_or("accepted root symlink")?
                .code,
            "invalid_runtime_location"
        );
        assert!(!root.join("haem").try_exists()?);
        directory.close()?;
        Ok(())
    }

    #[test]
    fn names_are_validated_before_runtime_entries() -> TestResult {
        let directory = fixture()?;
        let root = directory.path();
        let data = root.join("store");
        fs::create_dir(&data)?;
        let uid = fs::metadata(root)?.uid();
        let long = "x".repeat(129);
        for name in [
            "",
            ".",
            "..",
            "../store",
            "back\\slash",
            "nul\0name",
            long.as_str(),
        ] {
            assert_eq!(
                injected(root, uid, &data, Some(name), None, false)
                    .err()
                    .ok_or("accepted invalid name")?
                    .code,
                "invalid_store_name"
            );
            assert_eq!(fs::read_dir(root)?.collect::<Result<Vec<_>, _>>()?.len(), 1);
        }
        directory.close()?;
        Ok(())
    }

    #[test]
    fn directory_names_and_explicit_names_choose_deterministic_private_endpoints() -> TestResult {
        let directory = fixture()?;
        let root = directory.path();
        let uid = fs::metadata(root)?.uid();
        let first = root.join("first");
        let second = root.join("second");
        fs::create_dir(&first)?;
        fs::create_dir(&second)?;
        let a = injected(root, uid, &first, None, None, false)?;
        let b = injected(root, uid, &second, None, None, false)?;
        assert_eq!(a.name, "first");
        assert_eq!(b.name, "second");
        assert_ne!(a.socket, b.socket);
        assert_eq!(a.socket.parent(), Some(root.join("haem").as_path()));
        assert_eq!(
            fs::symlink_metadata(root.join("haem"))?
                .permissions()
                .mode()
                & 0o7777,
            0o700
        );
        assert_eq!(
            injected(root, uid, &first, None, None, false)?.socket,
            a.socket
        );
        let named = injected(root, uid, &first, Some("chosen"), None, false)?;
        assert_eq!(named.name, "chosen");
        assert_ne!(named.socket, a.socket);
        SocketAddr::from_pathname(&named.socket)?;
        let left = first.join("same");
        let right = second.join("same");
        fs::create_dir(&left)?;
        fs::create_dir(&right)?;
        assert_eq!(
            injected(root, uid, &left, None, None, false)?.socket,
            injected(root, uid, &right, None, None, false)?.socket
        );
        assert_ne!(
            injected(root, uid, &left, Some("left"), None, false)?.socket,
            injected(root, uid, &right, Some("right"), None, false)?.socket
        );
        directory.close()?;
        Ok(())
    }

    #[test]
    fn explicit_socket_is_preserved_without_querying_the_os() -> TestResult {
        let directory = fixture()?;
        let data = directory.path().join("store");
        fs::create_dir(&data)?;
        let socket = directory.path().join("legacy.sock");
        let uid = fs::metadata(directory.path())?.uid();
        let endpoint = resolve_with(
            &data,
            None,
            Some(&socket),
            false,
            || {
                Err(Refusal::new(
                    "runtime_location_unavailable",
                    "must not query",
                ))
            },
            |_| Ok(uid),
        )?;
        assert_eq!(endpoint.socket, socket);
        assert_eq!(endpoint.name, "store");
        assert!(!directory.path().join("haem").try_exists()?);
        directory.close()?;
        Ok(())
    }

    #[test]
    fn namespace_permission_and_symlink_substitution_are_refused() -> TestResult {
        let directory = fixture()?;
        let root = directory.path();
        let uid = fs::metadata(root)?.uid();
        let data = root.join("store");
        fs::create_dir(&data)?;
        let namespace = root.join("haem");
        fs::create_dir(&namespace)?;
        fs::set_permissions(&namespace, fs::Permissions::from_mode(0o755))?;
        assert_eq!(
            injected(root, uid, &data, None, None, false)
                .err()
                .ok_or("accepted wrong namespace mode")?
                .code,
            "invalid_runtime_location"
        );
        assert_eq!(
            fs::metadata(&namespace)?.permissions().mode() & 0o777,
            0o755
        );
        fs::remove_dir(&namespace)?;
        std::os::unix::fs::symlink(&data, &namespace)?;
        assert_eq!(
            injected(root, uid, &data, None, None, false)
                .err()
                .ok_or("accepted namespace symlink")?
                .code,
            "invalid_runtime_location"
        );
        assert!(fs::symlink_metadata(&namespace)?.file_type().is_symlink());
        directory.close()?;
        Ok(())
    }

    #[test]
    fn endpoint_length_is_refused_before_namespace_creation() -> TestResult {
        let directory = fixture()?;
        let root = directory.path().join("x".repeat(110));
        fs::create_dir(&root)?;
        fs::set_permissions(&root, fs::Permissions::from_mode(0o700))?;
        let data = directory.path().join("store");
        fs::create_dir(&data)?;
        assert_eq!(
            injected(&root, fs::metadata(&root)?.uid(), &data, None, None, false)
                .err()
                .ok_or("accepted oversized endpoint")?
                .code,
            "endpoint_too_long"
        );
        assert!(!root.join("haem").try_exists()?);
        directory.close()?;
        Ok(())
    }

    #[test]
    fn creation_canonicalizes_parent_and_checks_the_created_path() -> TestResult {
        let directory = fixture()?;
        let root = directory.path();
        let uid = fs::metadata(root)?.uid();
        let data = root.join("new-store");
        let endpoint = injected(root, uid, &data, None, None, true)?;
        assert_eq!(endpoint.name, "new-store");
        assert_eq!(endpoint.data_dir, fs::canonicalize(root)?.join("new-store"));
        fs::create_dir(&data)?;
        endpoint.check_created()?;
        fs::remove_dir(&data)?;
        let other = root.join("other");
        fs::create_dir(&other)?;
        std::os::unix::fs::symlink(&other, &data)?;
        assert_eq!(
            endpoint
                .check_created()
                .err()
                .ok_or("accepted changed created path")?
                .code,
            "data_dir_changed"
        );
        directory.close()?;
        Ok(())
    }

    #[test]
    fn uid_probe_is_removed_and_matches_the_created_file_owner() -> TestResult {
        let directory = fixture()?;
        assert_eq!(
            probe_uid(directory.path())?,
            fs::metadata(directory.path())?.uid()
        );
        assert_eq!(
            fs::read_dir(directory.path())?
                .collect::<Result<Vec<_>, _>>()?
                .len(),
            0
        );
        directory.close()?;
        Ok(())
    }

    #[test]
    fn uid_read_and_cleanup_failures_are_preserved() -> TestResult {
        let directory = fixture()?;
        assert_eq!(
            finish_probe(fs::metadata(directory.path()), Ok(()))
                .err()
                .ok_or("accepted invalid probe shape")?
                .code,
            "runtime_uid_unavailable"
        );
        let read = io::Error::other("read failed");
        assert_eq!(
            finish_probe(Err(read), Ok(()))
                .err()
                .ok_or("accepted failed uid read")?
                .code,
            "runtime_uid_unavailable"
        );
        let cleanup = io::Error::other("cleanup failed");
        assert_eq!(
            finish_probe(fs::metadata(directory.path()), Err(cleanup))
                .err()
                .ok_or("accepted failed cleanup")?
                .code,
            "runtime_cleanup_failed"
        );
        let both = finish_probe(
            Err(io::Error::other("read failed")),
            Err(io::Error::other("cleanup failed")),
        )
        .err()
        .ok_or("accepted both failures")?;
        assert_eq!(both.code, "runtime_cleanup_failed");
        assert!(both.to_string().contains("read failed"));
        assert!(both.to_string().contains("cleanup failed"));
        directory.close()?;
        Ok(())
    }

    #[test]
    fn byte_limits_and_full_digest_encoding_preserve_names() -> TestResult {
        validate_name(&"é".repeat(64))?;
        assert_eq!(
            validate_name(&"é".repeat(65))
                .err()
                .ok_or("accepted 130-byte name")?
                .code,
            "invalid_store_name"
        );
        let a = filename("store");
        let b = filename("other");
        assert_eq!(a.len(), 43);
        assert_eq!(a, "gk2A1xmF8IKiaZeo24i10d1Ft3fXNYXQPSNjA-Ib3pc");
        assert!(
            a.bytes()
                .all(|byte| byte.is_ascii_alphanumeric() || matches!(byte, b'-' | b'_'))
        );
        assert_ne!(a, b);
        assert_eq!(a, filename("store"));
        Ok(())
    }
}