20260715 add configurable max CA depth

src/validation/tree.rs

@@ -10,6 +10,8 @@ use crate::validation::publication_point::PublicationPointSnapshot;
 use std::borrow::Cow;
 use std::sync::{Arc, OnceLock};
 
+pub const DEFAULT_MAX_CA_DEPTH: usize = 32;
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct TreeRunConfig {
     /// Max CA instance depth to process (0 = root only).
@@ -37,7 +39,7 @@ pub struct TreeRunConfig {
 impl Default for TreeRunConfig {
     fn default() -> Self {
         Self {
-            max_depth: None,
+            max_depth: Some(DEFAULT_MAX_CA_DEPTH),
             max_instances: None,
             compact_audit: false,
             persist_vcir: true,
@@ -51,6 +53,15 @@ impl Default for TreeRunConfig {
     }
 }
 
+pub(crate) fn ca_depth_is_allowed(config: &TreeRunConfig, depth: usize) -> bool {
+    config.max_depth.is_none_or(|max_depth| depth <= max_depth)
+}
+
+pub(crate) fn next_allowed_ca_depth(config: &TreeRunConfig, parent_depth: usize) -> Option<usize> {
+    let child_depth = parent_depth.checked_add(1)?;
+    ca_depth_is_allowed(config, child_depth).then_some(child_depth)
+}
+
 #[derive(Clone, Debug)]
 pub enum CaCertificateRef {
     InlineDer(Vec<u8>),
@@ -347,10 +358,8 @@ pub fn run_tree_serial_audit_multi_root(
             }
         }
 
-        if let Some(max_depth) = config.max_depth {
-            if ca.depth > max_depth {
-                continue;
-            }
+        if !ca_depth_is_allowed(config, ca.depth) {
+            continue;
         }
 
         let res = match runner.run_publication_point(ca) {
@@ -393,6 +402,9 @@ pub fn run_tree_serial_audit_multi_root(
         }
         publication_points.push(audit);
 
+        let Some(child_depth) = next_allowed_ca_depth(config, ca.depth) else {
+            continue;
+        };
         let mut children = res.discovered_children;
         children.sort_by(|a, b| {
             a.handle
@@ -413,7 +425,7 @@ pub fn run_tree_serial_audit_multi_root(
         for child in children {
             queue.push_back(QueuedCaInstance {
                 id: next_id,
-                handle: child.handle.with_depth(ca.depth + 1),
+                handle: child.handle.with_depth(child_depth),
                 parent_id: Some(node.id),
                 discovered_from: Some(child.discovered_from),
             });