hs-v3: Add an encoded descriptor client cache lookup function

This commit adds hs_cache_lookup_encoded_as_client() function that returns the
encoded descriptor for a given service public key. This will be needed by the
"GETINFO hs/client/desc/id/<ADDR>" control port command.

Signed-off-by: David Goulet <dgoulet@torproject.org>

src/or/hs_cache.c

@@ -705,6 +705,24 @@ cache_clean_v3_as_client(time_t now)
   return bytes_removed;
 }
 
+/** Public API: Given the HS ed25519 identity public key in <b>key</b>, return
+ *  its HS encoded descriptor if it's stored in our cache, or NULL if not. */
+const char *
+hs_cache_lookup_encoded_as_client(const ed25519_public_key_t *key)
+{
+  hs_cache_client_descriptor_t *cached_desc = NULL;
+
+  tor_assert(key);
+
+  cached_desc = lookup_v3_desc_as_client(key->pubkey);
+  if (cached_desc) {
+    tor_assert(cached_desc->encoded_desc);
+    return cached_desc->encoded_desc;
+  }
+
+  return NULL;
+}
+
 /** Public API: Given the HS ed25519 identity public key in <b>key</b>, return
  *  its HS descriptor if it's stored in our cache, or NULL if not. */
 const hs_descriptor_t *

src/or/hs_cache.h

@@ -81,6 +81,8 @@ int hs_cache_lookup_as_dir(uint32_t version, const char *query,
 
 const hs_descriptor_t *
 hs_cache_lookup_as_client(const ed25519_public_key_t *key);
+const char *
+hs_cache_lookup_encoded_as_client(const ed25519_public_key_t *key);
 int hs_cache_store_as_client(const char *desc_str,
                              const ed25519_public_key_t *identity_pk);
 void hs_cache_clean_as_client(time_t now);