composefs/selinux: Add tests

Tests added by Claude Code

Assisted-by: Claude Code (Sonnet 4)
Signed-off-by: Pragyan Poudyal <pragyanpoudyal41999@gmail.com>

Author: Johan-Liebert1

crates/lib/src/bootc_composefs/selinux.rs

@@ -13,6 +13,57 @@ const SELINUX_CONFIG_PATH: &str = "etc/selinux/config";
 const SELINUX_TYPE: &str = "SELINUXTYPE=";
 const POLICY_FILE_PREFIX: &str = "policy.";
 
+/// Find the highest versioned policy file in the given directory
+fn find_latest_policy_file(policy_dir: &Dir) -> Result<String> {
+    let mut highest_policy_version = -1;
+    let mut latest_policy_name = None;
+
+    for entry in policy_dir
+        .entries_utf8()
+        .context("Getting policy dir entries")?
+    {
+        let entry = entry?;
+
+        if !entry.file_type()?.is_file() {
+            // We don't want symlinks, another directory etc
+            continue;
+        }
+
+        let filename = entry.file_name()?;
+
+        match filename.strip_prefix(POLICY_FILE_PREFIX) {
+            Some(version) => {
+                let v_int = version
+                    .parse::<i32>()
+                    .with_context(|| anyhow::anyhow!("Parsing {version} as int"))?;
+
+                if v_int < highest_policy_version {
+                    continue;
+                }
+
+                highest_policy_version = v_int;
+                latest_policy_name = Some(filename.to_string());
+            }
+
+            None => continue,
+        };
+    }
+
+    latest_policy_name.ok_or_else(|| anyhow::anyhow!("Failed to get latest SELinux policy"))
+}
+
+/// Compute SHA256 hash of a policy file
+fn compute_policy_file_hash(deployment_root: &Dir, full_path: &str) -> Result<String> {
+    let mut file = deployment_root
+        .open(full_path)
+        .context("Opening policy file")?;
+    let mut hasher = openssl::hash::Hasher::new(openssl::hash::MessageDigest::sha256())?;
+    std::io::copy(&mut file, &mut hasher)?;
+
+    let hash = hex::encode(hasher.finish().context("Computing hash")?);
+    Ok(hash)
+}
+
 #[context("Getting SELinux policy for deployment {depl_id}")]
 fn get_selinux_policy_for_deployment(
     storage: &Storage,
@@ -50,56 +101,15 @@ fn get_selinux_policy_for_deployment(
 
     let policy_dir_path = format!("etc/selinux/{type_}/policy");
 
-    let mut highest_policy_version = -1;
-    let mut latest_policy_name = None;
-
     let policy_dir = deployment_root
         .open_dir(&policy_dir_path)
         .context("Opening selinux policy dir")?;
 
-    for entry in policy_dir
-        .entries_utf8()
-        .context("Getting policy dir entries")?
-    {
-        let entry = entry?;
-
-        if !entry.file_type()?.is_file() {
-            // We don't want symlinks, another directory etc
-            continue;
-        }
-
-        let filename = entry.file_name()?;
-
-        match filename.strip_prefix(POLICY_FILE_PREFIX) {
-            Some(version) => {
-                let v_int = version
-                    .parse::<i32>()
-                    .with_context(|| anyhow::anyhow!("Parsing {version} as int"))?;
-
-                if v_int < highest_policy_version {
-                    continue;
-                }
-
-                highest_policy_version = v_int;
-                latest_policy_name = Some(filename.to_string());
-            }
-
-            None => continue,
-        };
-    }
-
-    let policy_name =
-        latest_policy_name.ok_or_else(|| anyhow::anyhow!("Failed to get latest SELinux policy"))?;
+    let policy_name = find_latest_policy_file(&policy_dir)?;
 
     let full_path = format!("{policy_dir_path}/{policy_name}");
 
-    let mut file = deployment_root
-        .open(full_path)
-        .context("Opening policy file")?;
-    let mut hasher = openssl::hash::Hasher::new(openssl::hash::MessageDigest::sha256())?;
-    std::io::copy(&mut file, &mut hasher)?;
-
-    let hash = hex::encode(hasher.finish().context("Computing hash")?);
+    let hash = compute_policy_file_hash(&deployment_root, &full_path)?;
 
     Ok(Some(hash))
 }
@@ -134,3 +144,150 @@ pub(crate) fn are_selinux_policies_compatible(
 
     Ok(sl_policy_match)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use cap_std_ext::cap_std::ambient_authority;
+    use cap_std_ext::dirext::CapStdExtDirExt;
+
+    #[test]
+    fn test_find_latest_policy_file() -> Result<()> {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority())?;
+
+        // Create policy files with different versions
+        tempdir.atomic_write("policy.30", "policy content 30")?;
+        tempdir.atomic_write("policy.31", "policy content 31")?;
+        tempdir.atomic_write("policy.29", "policy content 29")?;
+        tempdir.atomic_write("not_policy.32", "not a policy file")?;
+        tempdir.atomic_write("other_policy.txt", "invalid policy file")?;
+
+        let result = find_latest_policy_file(&tempdir)?;
+        assert_eq!(result, "policy.31");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_find_latest_policy_file_with_single_file() -> Result<()> {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority())?;
+
+        tempdir.atomic_write("policy.25", "single policy file")?;
+
+        let result = find_latest_policy_file(&tempdir)?;
+        assert_eq!(result, "policy.25");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_find_latest_policy_file_no_policy_files() {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority()).unwrap();
+
+        tempdir.atomic_write("not_policy.txt", "not a policy file").unwrap();
+        tempdir.atomic_write("other.txt", "invalid format").unwrap();
+
+        let result = find_latest_policy_file(&tempdir);
+        assert!(result.is_err());
+        assert!(result.unwrap_err().to_string().contains("Failed to get latest SELinux policy"));
+    }
+
+    #[test]
+    fn test_find_latest_policy_file_invalid_version() {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority()).unwrap();
+
+        tempdir.atomic_write("policy.abc", "invalid version").unwrap();
+
+        let result = find_latest_policy_file(&tempdir);
+        assert!(result.is_err());
+        assert!(result.unwrap_err().to_string().contains("Parsing abc as int"));
+    }
+
+    #[test]
+    fn test_find_latest_policy_file_negative_version() -> Result<()> {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority())?;
+
+        tempdir.atomic_write("policy.5", "positive version")?;
+        tempdir.atomic_write("policy.-1", "negative version")?;
+
+        let result = find_latest_policy_file(&tempdir)?;
+        assert_eq!(result, "policy.5");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_find_latest_policy_file_skips_directories() -> Result<()> {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority())?;
+
+        tempdir.create_dir("policy.99")?; // This should be skipped
+        tempdir.atomic_write("policy.5", "actual policy file")?;
+
+        let result = find_latest_policy_file(&tempdir)?;
+        assert_eq!(result, "policy.5");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_compute_policy_file_hash() -> Result<()> {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority())?;
+
+        let test_content = "test policy content for hashing";
+        tempdir.atomic_write("test_policy.30", test_content)?;
+
+        let hash = compute_policy_file_hash(&tempdir, "test_policy.30")?;
+
+        // Verify the hash is a valid SHA256 hash (64 hex characters)
+        assert_eq!(hash.len(), 64);
+        assert!(hash.chars().all(|c| c.is_ascii_hexdigit()));
+
+        // Verify consistent hashing
+        let hash2 = compute_policy_file_hash(&tempdir, "test_policy.30")?;
+        assert_eq!(hash, hash2);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_compute_policy_file_hash_different_content() -> Result<()> {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority())?;
+
+        tempdir.atomic_write("policy1.30", "content 1")?;
+        tempdir.atomic_write("policy2.30", "content 2")?;
+
+        let hash1 = compute_policy_file_hash(&tempdir, "policy1.30")?;
+        let hash2 = compute_policy_file_hash(&tempdir, "policy2.30")?;
+
+        assert_ne!(hash1, hash2);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_compute_policy_file_hash_nonexistent_file() {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority()).unwrap();
+
+        let result = compute_policy_file_hash(&tempdir, "nonexistent.30");
+        assert!(result.is_err());
+        assert!(result.unwrap_err().to_string().contains("Opening policy file"));
+    }
+
+    #[test]
+    fn test_compute_policy_file_hash_empty_file() -> Result<()> {
+        let tempdir = cap_std_ext::cap_tempfile::tempdir(ambient_authority())?;
+
+        tempdir.atomic_write("empty_policy.30", "")?;
+
+        let hash = compute_policy_file_hash(&tempdir, "empty_policy.30")?;
+
+        // Should produce a valid hash even for empty file
+        assert_eq!(hash.len(), 64);
+        assert!(hash.chars().all(|c| c.is_ascii_hexdigit()));
+        
+        // SHA256 of empty string
+        assert_eq!(hash, "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");
+
+        Ok(())
+    }
+}