[pbs-devel] [PATCH proxmox-backup] api: metrics: check permissions before reading any data from the cache

[Lukas Wagner]

Reading from the metric cache is somewhat expensive, so validate as many
of the required permissions as possible. For host metrics, we can
do the full check in advance. For datastores, we check if we have
audit permissions for *any* datastore. If we do not have privs for
either of those, we return early and avoid reading from the
cache altogether.

Signed-off-by: Lukas Wagner <l.wagner at proxmox.com>
Suggested-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
---
 src/api2/status/metrics.rs | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/api2/status/metrics.rs b/src/api2/status/metrics.rs
index b8aaceeb..a0004ef9 100644
--- a/src/api2/status/metrics.rs
+++ b/src/api2/status/metrics.rs
@@ -37,6 +37,25 @@ pub fn get_metrics(
     let auth_id: Authid = rpcenv.get_auth_id().unwrap().parse()?;
     let user_info = CachedUserInfo::new()?;
 
+    let has_any_datastore_audit_privs =
+        user_info.any_privs_below(&auth_id, &["datastore"], PRIV_DATASTORE_AUDIT)?;
+
+    let has_host_audit_privs =
+        (CachedUserInfo::lookup_privs(&user_info, &auth_id, &["system", "status"])
+            & PRIV_SYS_AUDIT)
+            != 0;
+
+    if !has_any_datastore_audit_privs && !has_host_audit_privs {
+        // The `pull_metrics::get_*` calls are expensive, so
+        // check early if the current user has sufficient privileges to read *any*
+        // metric data.
+        // For datastores, we do not yet know for which individual datastores
+        // we have metrics in the cache, so we just check if we have
+        // audit permissions for *any* datastore and filter after
+        // reading the data.
+        return Ok(Metrics { data: Vec::new() });
+    }
+
     let metrics = if history {
         pull_metrics::get_all_metrics(start_time)?
     } else {
@@ -46,11 +65,10 @@ pub fn get_metrics(
     let filter_by_privs = |point: &MetricDataPoint| {
         let id = point.id.as_str();
         if id == "host" {
-            let user_privs =
-                CachedUserInfo::lookup_privs(&user_info, &auth_id, &["system", "status"]);
-            return (user_privs & PRIV_SYS_AUDIT) != 0;
+            return has_host_audit_privs;
         } else if let Some(datastore_id) = id.strip_prefix("datastore/") {
             if !datastore_id.contains('/') {
+                // Now, check whether we have permissions for the individual datastore
                 let user_privs = CachedUserInfo::lookup_privs(
                     &user_info,
                     &auth_id,
-- 
2.39.5