internals: Add new bootc internals fsck

Split this out of the fsverity PR.

We obviously want a `fsck` command. This starts by doing
just two checks:

- A verification of `etc/resolv.conf`; this tests
  98995f6
- Just run `ostree fsck`

But obvious things we should be adding here are:

- Verifying kargs
- Verifying LBIs

etc.

Signed-off-by: Colin Walters <[email protected]>

docs/src/SUMMARY.md

@@ -55,6 +55,7 @@
 # Experimental features
 
 - [bootc image](experimental-bootc-image.md)
+- [fsck](experimental-fsck.md)
 - [--progress-fd](experimental-progress-fd.md)
 
 # More information

docs/src/experimental-fsck.md

@@ -0,0 +1,9 @@
+# bootc internals fsck
+
+Experimental features are subject to change or removal. Please
+do provide feedback on them.
+
+## Using `bootc internals fsck`
+
+This command expects a booted system, and performs consistency checks
+in a read-only fashion.

lib/src/cli.rs

@@ -423,6 +423,8 @@ pub(crate) enum InternalsOpts {
     },
     #[clap(subcommand)]
     Fsverity(FsverityOpts),
+    /// Perform consistency checking.
+    Fsck,
     /// Perform cleanup actions
     Cleanup,
     /// Proxy frontend for the `ostree-ext` CLI.
@@ -1173,6 +1175,11 @@ async fn run_from_opt(opt: Opt) -> Result<()> {
                     Ok(())
                 }
             },
+            InternalsOpts::Fsck => {
+                let sysroot = &get_storage().await?;
+                crate::fsck::fsck(&sysroot, std::io::stdout().lock())?;
+                Ok(())
+            }
             InternalsOpts::FixupEtcFstab => crate::deploy::fixup_etc_fstab(&root),
             InternalsOpts::PrintJsonSchema { of } => {
                 let schema = match of {

lib/src/fsck.rs

@@ -0,0 +1,128 @@
+//! # Write deployments merging image with configmap
+//!
+//! Create a merged filesystem tree with the image and mounted configmaps.
+
+// Unfortunately needed here to work with linkme
+#![allow(unsafe_code)]
+
+use std::process::Command;
+
+use cap_std_ext::cap_std;
+use cap_std_ext::cap_std::fs::{Dir, MetadataExt as _};
+use cap_std_ext::dirext::CapStdExtDirExt;
+use linkme::distributed_slice;
+
+use crate::store::Storage;
+
+/// A lint check has failed.
+#[derive(thiserror::Error, Debug)]
+struct FsckError(String);
+
+/// The outer error is for unexpected fatal runtime problems; the
+/// inner error is for the check failing in an expected way.
+type FsckResult = anyhow::Result<std::result::Result<(), FsckError>>;
+
+/// Everything is OK - we didn't encounter a runtime error, and
+/// the targeted check passed.
+fn fsck_ok() -> FsckResult {
+    Ok(Ok(()))
+}
+
+/// We successfully found a failure.
+fn fsck_err(msg: impl AsRef<str>) -> FsckResult {
+    Ok(Err(FsckError::new(msg)))
+}
+
+impl std::fmt::Display for FsckError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+impl FsckError {
+    fn new(msg: impl AsRef<str>) -> Self {
+        Self(msg.as_ref().to_owned())
+    }
+}
+
+#[derive(Debug)]
+struct FsckCheck {
+    name: &'static str,
+    ordering: u16,
+    f: FsckFn,
+}
+
+type FsckFn = fn(&Storage) -> FsckResult;
+#[distributed_slice]
+pub(crate) static FSCK_CHECKS: [FsckCheck];
+
+impl FsckCheck {
+    pub(crate) const fn new(name: &'static str, ordering: u16, f: FsckFn) -> Self {
+        FsckCheck { name, ordering, f }
+    }
+}
+
+#[distributed_slice(FSCK_CHECKS)]
+static CHECK_RESOLVCONF: FsckCheck = FsckCheck::new("etc-resolvconf", 5, check_resolvconf);
+/// See https://github.com/containers/bootc/pull/1096 and https://github.com/containers/bootc/pull/1167
+/// Basically verify that if /usr/etc/resolv.conf exists, it is not a zero-sized file that was
+/// probably injected by buildah and that bootc should have removed.
+///
+/// Note that this fsck check can fail for systems upgraded from old bootc right now, as
+/// we need the *new* bootc to fix it.
+///
+/// But at the current time fsck is an experimental feature that we should only be running
+/// in our CI.
+fn check_resolvconf(storage: &Storage) -> FsckResult {
+    // For now we only check the booted deployment.
+    if storage.booted_deployment().is_none() {
+        return fsck_ok();
+    }
+    // Read usr/etc/resolv.conf directly.
+    let usr = Dir::open_ambient_dir("/usr", cap_std::ambient_authority())?;
+    let Some(meta) = usr.symlink_metadata_optional("etc/resolv.conf")? else {
+        return fsck_ok();
+    };
+    if meta.is_file() && meta.size() == 0 {
+        return fsck_err("Found usr/etc/resolv.conf as zero-sized file");
+    }
+    fsck_ok()
+}
+
+pub(crate) fn fsck(storage: &Storage, mut output: impl std::io::Write) -> anyhow::Result<()> {
+    let mut checks = FSCK_CHECKS.static_slice().iter().collect::<Vec<_>>();
+    checks.sort_by(|a, b| a.ordering.cmp(&b.ordering));
+
+    let mut errors = false;
+    for check in checks.iter() {
+        let name = check.name;
+        // SAFETY: Shouldn't fail to join a thread
+        match (check.f)(&storage) {
+            Ok(Ok(())) => {}
+            Ok(Err(e)) => {
+                errors = true;
+                writeln!(output, "Failed check \"{name}\": {e}")?;
+            }
+            Err(e) => {
+                errors = true;
+                writeln!(output, "Unexpected runtime error in check \"{name}\": {e}")?;
+            }
+        }
+        println!("ok: {name}");
+    }
+    if errors {
+        anyhow::bail!("Encountered errors")
+    }
+
+    // Run an `ostree fsck` (yes, ostree exposes enough APIs
+    // that we could reimplement this in Rust, but eh)
+    let st = Command::new("ostree")
+        .arg("fsck")
+        .stdin(std::process::Stdio::inherit())
+        .status()?;
+    if !st.success() {
+        anyhow::bail!("ostree fsck failed");
+    }
+
+    Ok(())
+}

lib/src/lib.rs

@@ -7,6 +7,7 @@
 mod boundimage;
 pub mod cli;
 pub(crate) mod deploy;
+pub(crate) mod fsck;
 pub(crate) mod generator;
 mod glyph;
 mod image;

tests/booted/readonly/015-test-fsck.nu

@@ -0,0 +1,9 @@
+use std assert
+use tap.nu
+
+tap begin "Run fsck"
+
+# That's it, just ensure we've run a fsck on our basic install.
+bootc internals fsck
+
+tap ok