Support supplemental GIDs

Author: bleggett

src/config.rs

@@ -68,6 +68,10 @@ pub struct ExecutableSpec {
     /// These GIDs are relative to the user namespace that is optionally set up.
     pub gid: Option<gid_t>,
 
+    /// Optional supplemental GIDs to assume, in addition to any primary GID.
+    /// These GIDs are relative to the user namespace that is optionally set up.
+    pub supplemental_gids: Option<Vec<gid_t>>,
+
     /// An optional set of process-specific resource limits.
     /// If this set is not provided, setrlimit(2) will not be called.
     pub process_limits: Option<ProcessResourceLimits>,

src/runner.rs

@@ -201,6 +201,11 @@ impl CreateRequestBuilder {
         self
     }
 
+    pub fn set_supplemental_gids(mut self, gids: Vec<gid_t>) -> CreateRequestBuilder {
+        self.config.exec.supplemental_gids = gids.into();
+        self
+    }
+
     pub fn set_no_new_privs(mut self, no_new_privs: bool) -> CreateRequestBuilder {
         self.config.exec.no_new_privs = no_new_privs;
         self

src/wrap.rs

@@ -645,7 +645,7 @@ impl Wrappable for CreateRequest {
         set_keep_caps()?;
         // Set these *first*, before we exec. Otherwise
         // we may not be able to switch after dropping caps.
-        apply_gid_uid(self.exec.gid, self.exec.uid)?;
+        apply_gid_uid(self.exec.gid, self.exec.uid, self.exec.supplemental_gids.as_ref())?;
         // Now, we can synchronize effective/inherited/permitted caps
         // as a final step.
         apply_capabilities(self.capabilities.as_ref())?;
@@ -856,7 +856,7 @@ impl Mutatable for CreateDirMutation {
     }
 }
 
-fn apply_gid_uid(gid: Option<u32>, uid: Option<u32>) -> Result<()> {
+fn apply_gid_uid(gid: Option<u32>, uid: Option<u32>, supplemental_gids: Option<&Vec<u32>>) -> Result<()> {
     // NOTE - order is important here - must change GID *before* changing UID, to avoid
     // locking oneself out of the GID change with an "operation not permitted" error
     if let Some(target_gid) = gid {
@@ -869,6 +869,16 @@ fn apply_gid_uid(gid: Option<u32>, uid: Option<u32>) -> Result<()> {
         }
     }
 
+    // Set supplemental gids, if any. As with changing the primary gid, this must happen before the UID shift.
+    if let Some(target_supplemental_gids) = supplemental_gids {
+        unsafe {
+            let gids_libc: Vec<libc::gid_t> = target_supplemental_gids.iter().map(|g| *g as libc::gid_t).collect();
+            if libc::setgroups(gids_libc.len(), gids_libc.as_ptr()) < 0 {
+                warn!("unable to set supplemental GIDs: {:?}", Error::last_os_error());
+            }
+        }
+    }
+
     if let Some(target_uid) = uid {
         unsafe {
             // Check this to avoid a spurious log if we don't need to change,