rust/protover: use .and_not_in() instead of .retain() in all_supported()

.retain() would allocating a Vec of billions of integers and check them
one at a time to separate the supported versions from the unsupported.
This leads to a memory DoS.

Closes ticket 27206. Bugfix on e6625113c98c281b0a649598d7daa347c28915e9.

changes/bug27206

@@ -0,0 +1,4 @@
+  o Minor bugfixes (rust):
+    - protover_all_supported() would attempt to allocate up to 16GB on some
+      inputs, leading to a potential memory DoS. Fixes bug 27206; bugfix on
+      0.3.3.5-rc.

src/rust/protover/protover.rs

@@ -365,7 +365,6 @@ impl UnvalidatedProtoEntry {
 
             let maybe_supported_versions: Option<&ProtoSet> = supported.get(&supported_protocol);
             let supported_versions: &ProtoSet;
-            let mut unsupported_versions: ProtoSet;
 
             // If the protocol wasn't in the map, then we don't know about it
             // and don't support any of its versions.  Add its versions to the
@@ -378,8 +377,7 @@ impl UnvalidatedProtoEntry {
             } else {
                 supported_versions = maybe_supported_versions.unwrap();
             }
-            unsupported_versions = versions.clone();
-            unsupported_versions.retain(|x| !supported_versions.contains(x));
+            let unsupported_versions = versions.and_not_in(supported_versions);
 
             if !unsupported_versions.is_empty() {
                 unsupported.insert(protocol.clone(), unsupported_versions);

src/rust/protover/tests/protover.rs

@@ -354,18 +354,18 @@ fn protover_all_supported_should_exclude_some_versions_and_entire_protocols() {
 
 #[test]
 fn protover_all_supported_should_not_dos_anyones_computer() {
-    let proto: UnvalidatedProtoEntry = "Sleen=1-2147483648".parse().unwrap();
+    let proto: UnvalidatedProtoEntry = "Link=1-2147483648".parse().unwrap();
     let result: String = proto.all_supported().unwrap().to_string();
 
-    assert_eq!(result, "Sleen=1-2147483648".to_string());
+    assert_eq!(result, "Link=6-2147483648".to_string());
 }
 
 #[test]
 fn protover_all_supported_should_not_dos_anyones_computer_max_versions() {
-    let proto: UnvalidatedProtoEntry = "Sleen=1-4294967294".parse().unwrap();
+    let proto: UnvalidatedProtoEntry = "Link=1-4294967294".parse().unwrap();
     let result: String = proto.all_supported().unwrap().to_string();
 
-    assert_eq!(result, "Sleen=1-4294967294".to_string());
+    assert_eq!(result, "Link=6-4294967294".to_string());
 }
 
 #[test]