From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Mon, 11 Jan 2021 14:37:52 +0000 (+0100)
Subject: dnsdist: Fix a crash when a DoH responses map is updated at runtime
X-Git-Tag: rec-4.5.0-alpha1~8^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fpull%2F9934%2Fhead;p=thirdparty%2Fpdns.git

dnsdist: Fix a crash when a DoH responses map is updated at runtime
---

diff --git a/pdns/dnsdist-lua.cc b/pdns/dnsdist-lua.cc
index 97a748ac44..e8049beb34 100644
--- a/pdns/dnsdist-lua.cc
+++ b/pdns/dnsdist-lua.cc
@@ -2192,11 +2192,11 @@ static void setupLuaConfig(LuaContext& luaCtx, bool client, bool configCheck)
 
     luaCtx.registerFunction<void(std::shared_ptr<DOHFrontend>::*)(const std::map<int, std::shared_ptr<DOHResponseMapEntry>>&)>("setResponsesMap", [](std::shared_ptr<DOHFrontend> frontend, const std::map<int, std::shared_ptr<DOHResponseMapEntry>>& map) {
         if (frontend != nullptr) {
-          std::vector<std::shared_ptr<DOHResponseMapEntry>> newMap;
-          newMap.reserve(map.size());
+          auto newMap = std::make_shared<std::vector<std::shared_ptr<DOHResponseMapEntry>>>();
+          newMap->reserve(map.size());
 
           for (const auto& entry : map) {
-            newMap.push_back(entry.second);
+            newMap->push_back(entry.second);
           }
 
           frontend->d_responsesMap = std::move(newMap);
diff --git a/pdns/dnsdistdist/doh.cc b/pdns/dnsdistdist/doh.cc
index b1a0c4c027..919db49bcf 100644
--- a/pdns/dnsdistdist/doh.cc
+++ b/pdns/dnsdistdist/doh.cc
@@ -843,11 +843,16 @@ static int doh_handler(h2o_handler_t *self, h2o_req_t *req)
     // would be nice to be able to use a pdns_string_view there,
     // but regex (called by matches() internally) requires a null-terminated string
     string path(req->path.base, req->path.len);
-    for (const auto& entry : dsc->df->d_responsesMap) {
-      if (entry->matches(path)) {
-        const auto& customHeaders = entry->getHeaders();
-        handleResponse(*dsc->df, req, entry->getStatusCode(), entry->getContent(), customHeaders ? *customHeaders : dsc->df->d_customResponseHeaders, std::string(), false);
-        return 0;
+    /* the responses map can be updated at runtime, so we need to take a copy of
+       the shared pointer, increasing the reference counter */
+    auto responsesMap = dsc->df->d_responsesMap;
+    if (responsesMap) {
+      for (const auto& entry : *responsesMap) {
+        if (entry->matches(path)) {
+          const auto& customHeaders = entry->getHeaders();
+          handleResponse(*dsc->df, req, entry->getStatusCode(), entry->getContent(), customHeaders ? *customHeaders : dsc->df->d_customResponseHeaders, std::string(), false);
+          return 0;
+        }
       }
     }
 
diff --git a/pdns/doh.hh b/pdns/doh.hh
index 5327457d7f..10ed9a1b6d 100644
--- a/pdns/doh.hh
+++ b/pdns/doh.hh
@@ -71,7 +71,7 @@ struct DOHFrontend
   }
 
   std::shared_ptr<DOHServerConfig> d_dsc{nullptr};
-  std::vector<std::shared_ptr<DOHResponseMapEntry>> d_responsesMap;
+  std::shared_ptr<std::vector<std::shared_ptr<DOHResponseMapEntry>>> d_responsesMap;
   TLSConfig d_tlsConfig;
   TLSErrorCounters d_tlsCounters;
   std::string d_serverTokens{"h2o/dnsdist"};