Add a function to get an ed25519 ID from a routerinfo.

src/feature/nodelist/routerinfo.c

@@ -13,6 +13,7 @@
 
 #include "feature/nodelist/nodelist.h"
 #include "feature/nodelist/routerinfo.h"
+#include "feature/nodelist/torcert.h"
 
 #include "feature/nodelist/node_st.h"
 #include "feature/nodelist/routerinfo_st.h"
@@ -75,6 +76,21 @@ router_get_all_orports(const routerinfo_t *ri)
   return node_get_all_orports(&fake_node);
 }
 
+/** Return the Ed25519 identity key for this routerinfo, or NULL if it
+ * doesn't have one. */
+const ed25519_public_key_t *
+routerinfo_get_ed25519_id(const routerinfo_t *ri)
+{
+  if (BUG(! ri))
+    return NULL;
+
+  const tor_cert_t *cert = ri->cache_info.signing_key_cert;
+  if (cert && ! ed25519_public_key_is_zero(&cert->signing_key))
+    return &cert->signing_key;
+  else
+    return NULL;
+}
+
 /** Given a router purpose, convert it to a string.  Don't call this on
  * ROUTER_PURPOSE_UNKNOWN: The whole point of that value is that we don't
  * know its string representation. */

src/feature/nodelist/routerinfo.h

@@ -18,6 +18,10 @@ int router_get_orport(const routerinfo_t *router,
 int router_has_orport(const routerinfo_t *router,
                       const tor_addr_port_t *orport);
 
+struct ed25519_public_key_t;
+const struct ed25519_public_key_t *routerinfo_get_ed25519_id(
+                      const routerinfo_t *ri);
+
 smartlist_t *router_get_all_orports(const routerinfo_t *ri);
 
 const char *router_purpose_to_string(uint8_t p);