From a7cfc694bd086d13f608f534774e921d9d501246 Mon Sep 17 00:00:00 2001
From: Michal R <vad.sol@proton.me>
Date: Thu, 23 Oct 2025 15:46:05 +0200
Subject: [PATCH] xtask: Allow to run VM integration tests without dpkg

Debian packages are just nested archives, where the outer one is ar
and the inner one is lzma2 tarball. Use Rust crates to unpack them.

Co-authored-by: Tamir Duberstein <tamird@gmail.com>
---
 Cargo.toml       |  1 +
 xtask/Cargo.toml |  2 ++
 xtask/src/run.rs | 52 ++++++++++++++++++++++++++++--------------------
 3 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 81409567..048494b9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -62,6 +62,7 @@ rust-version = "1.85.0"
 # them to do that, but in the meantime we need to be careful.
 [workspace.dependencies]
 anyhow = { version = "1", default-features = false }
+ar = { version = "0.9", default-features = false }
 assert_matches = { version = "1.5.0", default-features = false }
 base64 = { version = "0.22.1", default-features = false }
 bindgen = { version = "0.72", default-features = false }
diff --git a/xtask/Cargo.toml b/xtask/Cargo.toml
index 04df81f6..d615859f 100644
--- a/xtask/Cargo.toml
+++ b/xtask/Cargo.toml
@@ -15,6 +15,7 @@ workspace = true
 
 [dependencies]
 anyhow = { workspace = true, features = ["std"] }
+ar = { workspace = true }
 aya-tool = { path = "../aya-tool", version = "0.1.0", default-features = false }
 cargo_metadata = { workspace = true }
 clap = { workspace = true, features = ["derive"] }
@@ -30,3 +31,4 @@ syn = { workspace = true }
 tar = { workspace = true }
 tempfile = { workspace = true }
 walkdir = { workspace = true }
+xz2 = { workspace = true }
diff --git a/xtask/src/run.rs b/xtask/src/run.rs
index b52e8890..efa79b54 100644
--- a/xtask/src/run.rs
+++ b/xtask/src/run.rs
@@ -1,7 +1,7 @@
 use std::{
     ffi::{OsStr, OsString},
     fmt::Write as _,
-    fs::{self, OpenOptions},
+    fs::{self, File, OpenOptions},
     io::{BufRead as _, BufReader, Write as _},
     ops::Deref as _,
     path::{self, Path, PathBuf},
@@ -300,29 +300,37 @@ pub(crate) fn run(opts: Options) -> Result<()> {
                 fs::create_dir_all(&archive_dir)
                     .with_context(|| format!("failed to create {}", archive_dir.display()))?;
 
-                let mut dpkg = Command::new("dpkg-deb");
-                dpkg.arg("--fsys-tarfile")
-                    .arg(archive)
-                    .stdout(Stdio::piped());
-                let mut dpkg_child = dpkg
-                    .spawn()
-                    .with_context(|| format!("failed to spawn {dpkg:?}"))?;
-                let Child { stdout, .. } = &mut dpkg_child;
-                let stdout = stdout.take().unwrap();
-                let mut archive_reader = tar::Archive::new(stdout);
-                archive_reader.unpack(&archive_dir).with_context(|| {
-                    format!(
-                        "failed to unpack archive {} to {}",
-                        archive.display(),
-                        archive_dir.display()
-                    )
+                let archive_reader = File::open(archive).with_context(|| {
+                    format!("failed to open the deb package {}", archive.display())
                 })?;
-                let status = dpkg_child
-                    .wait()
-                    .with_context(|| format!("failed to wait for {dpkg:?}"))?;
-                if !status.success() {
-                    bail!("{dpkg:?} exited with {status}");
+                let mut archive_reader = ar::Archive::new(archive_reader);
+                // `ar` entries are borrowed from the reader, so the reader
+                // cannot implement `Iterator` (because `Iterator::Item` is not
+                // a GAT).
+                //
+                // https://github.com/mdsteele/rust-ar/issues/15
+                let mut entries = 0;
+                while let Some(entry) = archive_reader.next_entry() {
+                    let entry = entry.with_context(|| {
+                        format!(
+                            "failed to read an entry of the deb package {}",
+                            archive.display()
+                        )
+                    })?;
+                    if entry.header().identifier() == b"data.tar.xz" {
+                        let entry_reader = xz2::read::XzDecoder::new(entry);
+                        let mut entry_reader = tar::Archive::new(entry_reader);
+                        entry_reader.unpack(&archive_dir).with_context(|| {
+                            format!(
+                                "failed to unpack archive {} to {}",
+                                archive.display(),
+                                archive_dir.display()
+                            )
+                        })?;
+                        entries += 1;
+                    }
                 }
+                assert_eq!(entries, 1);
 
                 let mut kernel_images = Vec::new();
                 let mut configs = Vec::new();