lint: Add a sysusers lint

Cargo.toml

@@ -8,7 +8,8 @@ members = [
     "blockdev",
     "xtask",
     "tests-integration",
-    "tmpfiles"
+    "tmpfiles",
+    "sysusers",
 ]
 resolver = "2"
 

hack/provision-derived.sh

@@ -37,3 +37,10 @@ d /var/roothome/buildinfo/content_manifests 0755 - - -
 f /var/roothome/buildinfo/content_manifests/content-sets.json 0644 - - -
 EOF
 fi
+
+# And add missing sysusers.d entries
+if ! grep -q -r sudo /usr/lib/sysusers.d; then
+  cat >/usr/lib/sysusers.d/bootc-sudo-workaround.conf <<'EOF'
+g sudo 16
+EOF
+fi

lib/Cargo.toml

@@ -19,6 +19,7 @@ anyhow = { workspace = true }
 bootc-utils = { path = "../utils" }
 bootc-blockdev = { path = "../blockdev" }
 bootc-tmpfiles = { path = "../tmpfiles" }
+bootc-sysusers = { path = "../sysusers" }
 camino = { workspace = true, features = ["serde1"] }
 ostree-ext = { path = "../ostree-ext", features = ["bootc"] }
 chrono = { workspace = true, features = ["serde"] }

lib/src/lints.rs

@@ -11,6 +11,7 @@ use std::fmt::Write as WriteFmt;
 use std::os::unix::ffi::OsStrExt;
 
 use anyhow::Result;
+use bootc_utils::PathQuotedDisplay;
 use camino::{Utf8Path, Utf8PathBuf};
 use cap_std::fs::Dir;
 use cap_std_ext::cap_std;
@@ -505,8 +506,58 @@ fn check_var_tmpfiles(_root: &Dir) -> LintResult {
         bootc_utils::iterator_split_nonempty_rest_count(r.unsupported.iter(), 5)
     {
         msg.push_str("Found non-directory/non-symlink files in /var:\n");
+        for elt in samples.map(PathQuotedDisplay::new) {
+            writeln!(msg, "  {elt}")?;
+        }
+        if rest > 0 {
+            writeln!(msg, "  ...and {} more", rest)?;
+        }
+    }
+    lint_err(msg)
+}
+
+#[distributed_slice(LINTS)]
+static LINT_SYSUSERS: Lint = Lint {
+    name: "sysusers",
+    ty: LintType::Warning,
+    description: indoc! { r#"
+Check for users in /etc/passwd and groups in /etc/group that do not have corresponding
+systemd sysusers.d entries in /usr/lib/sysusers.d.
+This can cause a problem across upgrades because if /etc is not transient and is locally
+modified (commonly due to local user additions), then the contents of /etc/passwd in the new container
+image may not be visible.
+
+Using systemd-sysusers to allocate users and groups will ensure that these are allocated
+on system startup alongside other users.
+
+More on this topic in <https://containers.github.io/bootc/building/users-and-groups.html>
+"#},
+    f: check_sysusers,
+    root_type: None,
+};
+fn check_sysusers(rootfs: &Dir) -> LintResult {
+    let r = bootc_sysusers::analyze(rootfs)?;
+    if r.is_empty() {
+        return lint_ok();
+    }
+    let mut msg = String::new();
+    if let Some((samples, rest)) =
+        bootc_utils::iterator_split_nonempty_rest_count(r.missing_users.iter(), 5)
+    {
+        msg.push_str("Found /etc/passwd entry without corresponding systemd sysusers.d:\n");
         for elt in samples {
-            writeln!(msg, "  {elt:?}")?;
+            writeln!(msg, "  {elt}")?;
+        }
+        if rest > 0 {
+            writeln!(msg, "  ...and {} more", rest)?;
+        }
+    }
+    if let Some((samples, rest)) =
+        bootc_utils::iterator_split_nonempty_rest_count(r.missing_groups.iter(), 5)
+    {
+        msg.push_str("Found /etc/group entry without corresponding systemd sysusers.d:\n");
+        for elt in samples {
+            writeln!(msg, "  {elt}")?;
         }
         if rest > 0 {
             writeln!(msg, "  ...and {} more", rest)?;

sysusers/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "bootc-sysusers"
+version = "0.1.0"
+license = "MIT OR Apache-2.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+anyhow = { workspace = true }
+camino = { workspace = true }
+fn-error-context = { workspace = true }
+cap-std-ext = { version = "4", features = ["fs_utf8"] }
+hex = "0.4"
+thiserror = { workspace = true }
+tempfile = { workspace = true }
+bootc-utils = { path = "../utils" }
+rustix = { workspace = true }
+uzers = "0.12"
+
+[dev-dependencies]
+indoc = { workspace = true }
+similar-asserts = { workspace = true }
+
+[lints]
+workspace = true