forked from ostreedev/ostree-rs-ext
/
export.rs
351 lines (314 loc) · 12.4 KB
/
export.rs
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//! APIs for creating container images from OSTree commits
use crate::objgv::*;
use anyhow::Context;
use anyhow::Result;
use camino::{Utf8Path, Utf8PathBuf};
use fn_error_context::context;
use gio::glib;
use gio::prelude::*;
use gvariant::aligned_bytes::TryAsAligned;
use gvariant::{Marker, Structure};
use ostree::gio;
use std::borrow::Cow;
use std::collections::HashSet;
use std::io::BufReader;
// This way the default ostree -> sysroot/ostree symlink works.
const OSTREEDIR: &str = "sysroot/ostree";
/// A decently large buffer, as used by e.g. coreutils `cat`.
/// System calls are expensive.
const BUF_CAPACITY: usize = 131072;
/// Convert /usr/etc back to /etc
fn map_path(p: &Utf8Path) -> std::borrow::Cow<Utf8Path> {
match p.strip_prefix("./usr/etc") {
Ok(r) => Cow::Owned(Utf8Path::new("./etc").join(r)),
_ => Cow::Borrowed(p),
}
}
struct OstreeTarWriter<'a, W: std::io::Write> {
repo: &'a ostree::Repo,
out: &'a mut tar::Builder<W>,
wrote_initdirs: bool,
wrote_dirtree: HashSet<String>,
wrote_dirmeta: HashSet<String>,
wrote_content: HashSet<String>,
wrote_xattrs: HashSet<String>,
}
fn object_path(objtype: ostree::ObjectType, checksum: &str) -> Utf8PathBuf {
let suffix = match objtype {
ostree::ObjectType::Commit => "commit",
ostree::ObjectType::CommitMeta => "commitmeta",
ostree::ObjectType::DirTree => "dirtree",
ostree::ObjectType::DirMeta => "dirmeta",
ostree::ObjectType::File => "file",
o => panic!("Unexpected object type: {:?}", o),
};
let (first, rest) = checksum.split_at(2);
format!("{}/repo/objects/{}/{}.{}", OSTREEDIR, first, rest, suffix).into()
}
fn xattrs_path(checksum: &str) -> Utf8PathBuf {
format!("{}/repo/xattrs/{}", OSTREEDIR, checksum).into()
}
impl<'a, W: std::io::Write> OstreeTarWriter<'a, W> {
fn new(repo: &'a ostree::Repo, out: &'a mut tar::Builder<W>) -> Self {
Self {
repo,
out,
wrote_initdirs: false,
wrote_dirmeta: HashSet::new(),
wrote_dirtree: HashSet::new(),
wrote_content: HashSet::new(),
wrote_xattrs: HashSet::new(),
}
}
/// Write the initial directory structure.
fn write_initial_directories(&mut self) -> Result<()> {
if self.wrote_initdirs {
return Ok(());
}
self.wrote_initdirs = true;
// Object subdirectories
for d in 0..0xFF {
let mut h = tar::Header::new_gnu();
h.set_entry_type(tar::EntryType::Directory);
h.set_uid(0);
h.set_gid(0);
h.set_mode(0o755);
h.set_size(0);
let path = format!("{}/repo/objects/{:#04x}", OSTREEDIR, d);
self.out.append_data(&mut h, &path, &mut std::io::empty())?;
}
// The special `repo/xattrs` directory used only in our tar serialization.
let mut h = tar::Header::new_gnu();
h.set_entry_type(tar::EntryType::Directory);
h.set_uid(0);
h.set_gid(0);
h.set_mode(0o755);
h.set_size(0);
let path = format!("{}/repo/xattrs", OSTREEDIR);
self.out.append_data(&mut h, &path, &mut std::io::empty())?;
Ok(())
}
/// Recursively serialize a commit object to the target tar stream.
fn write_commit(&mut self, checksum: &str) -> Result<()> {
let cancellable = gio::NONE_CANCELLABLE;
self.write_initial_directories()?;
let (commit_v, _) = self.repo.load_commit(checksum)?;
let commit_v = &commit_v;
self.append(ostree::ObjectType::Commit, checksum, commit_v)?;
if let Some(commitmeta) = self
.repo
.read_commit_detached_metadata(checksum, cancellable)?
{
self.append(ostree::ObjectType::CommitMeta, checksum, &commitmeta)?;
}
let commit_v = commit_v.data_as_bytes();
let commit_v = commit_v.try_as_aligned()?;
let commit = gv_commit!().cast(commit_v);
let commit = commit.to_tuple();
let contents = &hex::encode(commit.6);
let metadata_checksum = &hex::encode(commit.7);
let metadata_v = self
.repo
.load_variant(ostree::ObjectType::DirMeta, metadata_checksum)?;
self.append(ostree::ObjectType::DirMeta, metadata_checksum, &metadata_v)?;
self.append_dirtree(Utf8Path::new("./"), contents, cancellable)?;
Ok(())
}
fn append(
&mut self,
objtype: ostree::ObjectType,
checksum: &str,
v: &glib::Variant,
) -> Result<()> {
let set = match objtype {
ostree::ObjectType::Commit | ostree::ObjectType::CommitMeta => None,
ostree::ObjectType::DirTree => Some(&mut self.wrote_dirtree),
ostree::ObjectType::DirMeta => Some(&mut self.wrote_dirmeta),
o => panic!("Unexpected object type: {:?}", o),
};
if let Some(set) = set {
if set.contains(checksum) {
return Ok(());
}
let inserted = set.insert(checksum.to_string());
debug_assert!(inserted);
}
let mut h = tar::Header::new_gnu();
h.set_uid(0);
h.set_gid(0);
h.set_mode(0o644);
let data = v.data_as_bytes();
let data = data.as_ref();
h.set_size(data.len() as u64);
self.out
.append_data(&mut h, &object_path(objtype, checksum), data)
.with_context(|| format!("Writing object {}", checksum))?;
Ok(())
}
#[context("Writing xattrs")]
fn append_xattrs(
&mut self,
xattrs: &glib::Variant,
) -> Result<Option<(Utf8PathBuf, tar::Header)>> {
let xattrs_data = xattrs.data_as_bytes();
let xattrs_data = xattrs_data.as_ref();
if xattrs_data.is_empty() {
return Ok(None);
}
let mut h = tar::Header::new_gnu();
h.set_mode(0o644);
h.set_size(0);
let digest = openssl::hash::hash(openssl::hash::MessageDigest::sha256(), xattrs_data)?;
let mut hexbuf = [0u8; 64];
hex::encode_to_slice(digest, &mut hexbuf)?;
let checksum = std::str::from_utf8(&hexbuf)?;
let path = xattrs_path(checksum);
if !self.wrote_xattrs.contains(checksum) {
let inserted = self.wrote_xattrs.insert(checksum.to_string());
debug_assert!(inserted);
let mut target_header = h.clone();
target_header.set_size(xattrs_data.len() as u64);
self.out
.append_data(&mut target_header, &path, xattrs_data)?;
}
Ok(Some((path, h)))
}
/// Write a content object, returning the path/header that should be used
/// as a hard link to it in the target path. This matches how ostree checkouts work.
fn append_content(&mut self, checksum: &str) -> Result<(Utf8PathBuf, tar::Header)> {
let path = object_path(ostree::ObjectType::File, checksum);
let (instream, meta, xattrs) = self.repo.load_file(checksum, gio::NONE_CANCELLABLE)?;
let meta = meta.unwrap();
let xattrs = xattrs.unwrap();
let mut h = tar::Header::new_gnu();
h.set_uid(meta.attribute_uint32("unix::uid") as u64);
h.set_gid(meta.attribute_uint32("unix::gid") as u64);
let mode = meta.attribute_uint32("unix::mode");
h.set_mode(mode);
let mut target_header = h.clone();
target_header.set_size(0);
if !self.wrote_content.contains(checksum) {
let inserted = self.wrote_content.insert(checksum.to_string());
debug_assert!(inserted);
if let Some((xattrspath, mut xattrsheader)) = self.append_xattrs(&xattrs)? {
xattrsheader.set_entry_type(tar::EntryType::Link);
xattrsheader.set_link_name(xattrspath)?;
let subpath = format!("{}.xattrs", path);
self.out
.append_data(&mut xattrsheader, subpath, &mut std::io::empty())?;
}
if let Some(instream) = instream {
h.set_entry_type(tar::EntryType::Regular);
h.set_size(meta.size() as u64);
let mut instream = BufReader::with_capacity(BUF_CAPACITY, instream.into_read());
self.out
.append_data(&mut h, &path, &mut instream)
.with_context(|| format!("Writing regfile {}", checksum))?;
} else {
let target = meta.symlink_target().unwrap();
let target = target.as_str();
let context = || format!("Writing content symlink: {}", checksum);
if target.contains("//") {
h.set_link_name_literal(meta.symlink_target().unwrap().as_str())
.with_context(context)?;
self.out
.append_data(&mut h, &path, &mut std::io::empty())
.with_context(context)?;
} else {
h.set_entry_type(tar::EntryType::Symlink);
h.set_size(0);
self.out
.append_link(&mut h, &path, target)
.with_context(context)?;
}
}
}
Ok((path, target_header))
}
/// Write a dirtree object.
fn append_dirtree<C: IsA<gio::Cancellable>>(
&mut self,
dirpath: &Utf8Path,
checksum: &str,
cancellable: Option<&C>,
) -> Result<()> {
let v = &self
.repo
.load_variant(ostree::ObjectType::DirTree, checksum)?;
self.append(ostree::ObjectType::DirTree, checksum, v)?;
let v = v.data_as_bytes();
let v = v.try_as_aligned()?;
let v = gv_dirtree!().cast(v);
let (files, dirs) = v.to_tuple();
if let Some(c) = cancellable {
c.set_error_if_cancelled()?;
}
// A reusable buffer to avoid heap allocating these
let mut hexbuf = [0u8; 64];
for file in files {
let (name, csum) = file.to_tuple();
let name = name.to_str();
hex::encode_to_slice(csum, &mut hexbuf)?;
let checksum = std::str::from_utf8(&hexbuf)?;
let (objpath, mut h) = self.append_content(checksum)?;
h.set_entry_type(tar::EntryType::Link);
h.set_link_name(&objpath)?;
let subpath = &dirpath.join(name);
let subpath = map_path(subpath);
self.out
.append_data(&mut h, &*subpath, &mut std::io::empty())?;
}
for item in dirs {
let (name, contents_csum, meta_csum) = item.to_tuple();
let name = name.to_str();
{
hex::encode_to_slice(meta_csum, &mut hexbuf)?;
let meta_csum = std::str::from_utf8(&hexbuf)?;
let meta_v = &self
.repo
.load_variant(ostree::ObjectType::DirMeta, meta_csum)?;
self.append(ostree::ObjectType::DirMeta, meta_csum, meta_v)?;
}
hex::encode_to_slice(contents_csum, &mut hexbuf)?;
let dirtree_csum = std::str::from_utf8(&hexbuf)?;
let subpath = &dirpath.join(name);
let subpath = map_path(subpath);
self.append_dirtree(&*subpath, dirtree_csum, cancellable)?;
}
Ok(())
}
}
/// Recursively walk an OSTree commit and generate data into a `[tar::Builder]`
/// which contains all of the metadata objects, as well as a hardlinked
/// stream that looks like a checkout. Extended attributes are stored specially out
/// of band of tar so that they can be reliably retrieved.
fn impl_export<W: std::io::Write>(
repo: &ostree::Repo,
commit_checksum: &str,
out: &mut tar::Builder<W>,
) -> Result<()> {
let writer = &mut OstreeTarWriter::new(repo, out);
writer.write_commit(commit_checksum)?;
Ok(())
}
/// Export an ostree commit to an (uncompressed) tar archive stream.
#[context("Exporting commit")]
pub fn export_commit(repo: &ostree::Repo, rev: &str, out: impl std::io::Write) -> Result<()> {
let commit = repo.resolve_rev(rev, false)?;
let mut tar = tar::Builder::new(out);
impl_export(repo, commit.unwrap().as_str(), &mut tar)?;
tar.finish()?;
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_map_path() {
assert_eq!(map_path("/".into()), Utf8Path::new("/"));
assert_eq!(
map_path("./usr/etc/blah".into()),
Utf8Path::new("./etc/blah")
);
}
}