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use std::collections::BTreeMap;
use std::fs::{self, File, OpenOptions};
use std::os::unix::fs::MetadataExt;
use std::path::{Path, PathBuf};
use anyhow::{bail, Context, Result};
use tar::{Builder, EntryType, Header};
/// Writes a deterministic rootfs tar archive using numeric ownership metadata.
///
/// Extended ACLs and xattrs are intentionally not represented by this initial
/// portable archive format. Callers that require them must use a future archive
/// policy which can verify their availability before packaging.
#[derive(Debug, Default, Clone, Copy)]
pub struct NativeTarWriter;
impl NativeTarWriter {
pub fn new() -> Self {
Self
}
pub fn write(&self, rootfs: impl AsRef<Path>, output: impl AsRef<Path>) -> Result<()> {
let rootfs = rootfs.as_ref();
if !rootfs.is_dir() {
bail!("rootfs is not a directory: {}", rootfs.display());
}
let output = output.as_ref();
reject_output_inside_rootfs(rootfs, output)?;
let temporary = temporary_output_path(output)?;
let result = (|| {
let file = OpenOptions::new()
.write(true)
.create_new(true)
.open(&temporary)
.with_context(|| format!("create temporary archive {}", temporary.display()))?;
let mut archive = Builder::new(file);
append_tree(&mut archive, rootfs, Path::new(""), &mut BTreeMap::new())?;
archive
.finish()
.with_context(|| format!("finish archive {}", temporary.display()))?;
fs::rename(&temporary, output).with_context(|| {
format!(
"publish completed archive {} as {}",
temporary.display(),
output.display()
)
})
})();
if result.is_err() {
let _ = fs::remove_file(&temporary);
}
result
}
}
fn reject_output_inside_rootfs(rootfs: &Path, output: &Path) -> Result<()> {
let rootfs = rootfs
.canonicalize()
.with_context(|| format!("canonicalize rootfs {}", rootfs.display()))?;
let output_parent = output.parent().unwrap_or_else(|| Path::new("."));
let output_parent = output_parent
.canonicalize()
.with_context(|| format!("canonicalize archive output parent {}", output_parent.display()))?;
if output_parent.starts_with(&rootfs) {
bail!(
"archive output must not be inside rootfs: {} is below {}",
output.display(),
rootfs.display()
);
}
Ok(())
}
fn temporary_output_path(output: &Path) -> Result<PathBuf> {
let name = output
.file_name()
.ok_or_else(|| anyhow::anyhow!("archive output path has no filename: {}", output.display()))?;
let mut temporary_name = name.to_os_string();
temporary_name.push(".partial");
Ok(output.with_file_name(temporary_name))
}
fn append_tree(
archive: &mut Builder<File>,
rootfs: &Path,
relative: &Path,
hardlink_targets: &mut BTreeMap<(u64, u64), std::path::PathBuf>,
) -> Result<()> {
let directory = rootfs.join(relative);
let mut entries = fs::read_dir(&directory)
.with_context(|| format!("read rootfs directory {}", directory.display()))?
.collect::<std::result::Result<Vec<_>, _>>()?;
entries.sort_by_key(|entry| entry.file_name());
for entry in entries {
let name = entry.file_name();
if name == ".host" || name == ".fakedata" {
continue;
}
let path = entry.path();
let archive_path = relative.join(&name);
let metadata = fs::symlink_metadata(&path)
.with_context(|| format!("inspect rootfs entry {}", path.display()))?;
let file_type = metadata.file_type();
if file_type.is_dir() {
append_directory(archive, &archive_path, &metadata)?;
append_tree(archive, rootfs, &archive_path, hardlink_targets)?;
} else if file_type.is_file() {
append_file(archive, &path, &archive_path, &metadata, hardlink_targets)?;
} else if file_type.is_symlink() {
append_symlink(archive, &path, &archive_path, &metadata)?;
} else {
bail!("unsupported rootfs entry type: {}", path.display());
}
}
Ok(())
}
fn deterministic_header(metadata: &fs::Metadata, entry_type: EntryType, size: u64) -> Header {
use std::os::unix::fs::PermissionsExt;
let mut header = Header::new_gnu();
header.set_entry_type(entry_type);
header.set_mode(metadata.permissions().mode());
header.set_uid(0);
header.set_gid(0);
header.set_mtime(0);
header.set_size(size);
header
}
fn append_directory(archive: &mut Builder<File>, path: &Path, metadata: &fs::Metadata) -> Result<()> {
let mut header = deterministic_header(metadata, EntryType::Directory, 0);
archive
.append_data(&mut header, path, std::io::empty())
.with_context(|| format!("append directory {}", path.display()))
}
fn append_file(
archive: &mut Builder<File>,
source: &Path,
path: &Path,
metadata: &fs::Metadata,
hardlink_targets: &mut BTreeMap<(u64, u64), std::path::PathBuf>,
) -> Result<()> {
let key = (metadata.dev(), metadata.ino());
if let Some(target) = hardlink_targets.get(&key) {
return append_hardlink(archive, path, target, metadata);
}
let mut header = deterministic_header(metadata, EntryType::Regular, metadata.len());
let input = File::open(source).with_context(|| format!("open rootfs file {}", source.display()))?;
archive
.append_data(&mut header, path, input)
.with_context(|| format!("append file {}", path.display()))?;
hardlink_targets.insert(key, path.to_path_buf());
Ok(())
}
fn append_hardlink(
archive: &mut Builder<File>,
path: &Path,
target: &Path,
metadata: &fs::Metadata,
) -> Result<()> {
let mut header = deterministic_header(metadata, EntryType::Link, 0);
archive
.append_link(&mut header, path, target)
.with_context(|| format!("append hardlink {}", path.display()))
}
fn append_symlink(
archive: &mut Builder<File>,
source: &Path,
path: &Path,
metadata: &fs::Metadata,
) -> Result<()> {
let target = fs::read_link(source).with_context(|| format!("read rootfs symlink {}", source.display()))?;
let mut header = deterministic_header(metadata, EntryType::Symlink, 0);
archive
.append_link(&mut header, path, target)
.with_context(|| format!("append symlink {}", path.display()))
}
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