Add aliases to to SecurityAdvisory and add hex_advisory:group_for_display/1

proto/hex_pb_package.proto

@@ -27,7 +27,8 @@ message Release {
   optional bytes outer_checksum = 5;
   // Indexes into Package.advisories for advisories affecting this release
   repeated uint32 advisory_indexes = 6;
-  // Release published timestamp
+  // Release published timestamp. Optional for backwards compatibility —
+  // clients treat absence as "no information".
   optional Timestamp published_at = 7;
 }
 
@@ -57,6 +58,9 @@ message SecurityAdvisory {
   optional float cvss_score = 5;
   // OSV API URL for the advisory
   required string api_url = 6;
+  // Other identifiers for the same vulnerability (e.g. a CVE id when the
+  // primary id is a GHSA id, or vice versa).
+  repeated string aliases = 7;
 }
 
 enum AdvisorySeverity {

src/hex_advisory.erl

@@ -0,0 +1,111 @@
+%% @doc
+%% Display-time deduplication of security advisories.
+%%
+%% Multiple advisory sources (EEF, GHSA, NVD, ...) can publish the same
+%% vulnerability under different identifiers and cross-reference each other
+%% via the `aliases' field. `group_for_display/1' groups such advisories
+%% and picks a deterministic primary so callers can render one entry per
+%% vulnerability.
+-module(hex_advisory).
+-export([group_for_display/1]).
+
+-type advisory() :: map().
+-type group() :: map().
+
+-spec group_for_display([advisory()]) -> [group()].
+group_for_display(Advisories) ->
+    %% Preserve input order of first member per group.
+    {GroupOrder, GroupsByKey} =
+        lists:foldl(
+            fun(Adv, {Order, Map}) ->
+                Key = group_key(Adv),
+                case maps:is_key(Key, Map) of
+                    true ->
+                        Existing = maps:get(Key, Map),
+                        {Order, Map#{Key := Existing ++ [Adv]}};
+                    false ->
+                        {Order ++ [Key], Map#{Key => [Adv]}}
+                end
+            end,
+            {[], #{}},
+            Advisories
+        ),
+    [merge_group(maps:get(Key, GroupsByKey)) || Key <- GroupOrder].
+
+%%====================================================================
+%% Grouping
+%%====================================================================
+
+%% Key is the first CVE-prefixed identifier across {id, aliases}, else id.
+group_key(#{id := Id} = Adv) ->
+    Ids = [Id | maps:get(aliases, Adv, [])],
+    case lists:dropwhile(fun(I) -> not is_cve(I) end, Ids) of
+        [Cve | _] -> Cve;
+        [] -> Id
+    end.
+
+is_cve(<<"CVE-", _/binary>>) -> true;
+is_cve(_) -> false.
+
+%%====================================================================
+%% Merging
+%%====================================================================
+
+merge_group(Advisories) ->
+    Primary = pick_primary(Advisories),
+    Rest = [A || A <- Advisories, maps:get(id, A) =/= maps:get(id, Primary)],
+    Primary#{aliases => display_aliases(Primary, [Primary | Rest])}.
+
+pick_primary(Advisories) ->
+    [Primary | _] = lists:sort(
+        fun(A, B) -> source_key(A) =< source_key(B) end,
+        Advisories
+    ),
+    Primary.
+
+source_key(#{id := Id}) -> {source_priority(Id), Id}.
+
+source_priority(<<"EEF-", _/binary>>) -> 0;
+source_priority(<<"GHSA-", _/binary>>) -> 1;
+source_priority(<<"NVD-", _/binary>>) -> 2;
+source_priority(_) -> 3.
+
+%%====================================================================
+%% Aliases
+%%====================================================================
+
+display_aliases(Primary, Advisories) ->
+    PrimaryId = maps:get(id, Primary),
+    AdvisoryIds = sets:from_list([maps:get(id, A) || A <- Advisories]),
+    AllIds = lists:flatmap(fun identifiers/1, Advisories),
+    Unique = uniq(AllIds),
+    [
+        #{
+            id => Id,
+            url => alias_url(Id, AdvisoryIds)
+        }
+     || Id <- Unique, Id =/= PrimaryId
+    ].
+
+identifiers(Advisory) ->
+    [maps:get(id, Advisory) | maps:get(aliases, Advisory, [])].
+
+alias_url(Id, AdvisoryIds) ->
+    case sets:is_element(Id, AdvisoryIds) of
+        true -> <<"https://osv.dev/vulnerability/", Id/binary>>;
+        false -> undefined
+    end.
+
+uniq(List) ->
+    {_, Out} =
+        lists:foldl(
+            fun(X, {Seen, Acc}) ->
+                case sets:is_element(X, Seen) of
+                    true -> {Seen, Acc};
+                    false -> {sets:add_element(X, Seen), Acc ++ [X]}
+                end
+            end,
+            {sets:new(), []},
+            List
+        ),
+    Out.