Prepare for #40373: Re-introduce parsing for v2 onion addresses.

Welcome back ONION_V2_HOSTNAME! :)

src/core/or/connection_edge.c

@@ -1612,6 +1612,23 @@ consider_plaintext_ports(entry_connection_t *conn, uint16_t port)
   return 0;
 }
 
+/** Return true iff <b>query</b> is a syntactically valid service ID (as
+ * generated by rend_get_service_id).  */
+static int
+rend_valid_v2_service_id(const char *query)
+{
+  /** Length of 'y' portion of 'y.onion' URL. */
+#define REND_SERVICE_ID_LEN_BASE32 16
+
+  if (strlen(query) != REND_SERVICE_ID_LEN_BASE32)
+    return 0;
+
+  if (strspn(query, BASE32_CHARS) != REND_SERVICE_ID_LEN_BASE32)
+    return 0;
+
+  return 1;
+}
+
 /** Parse the given hostname in address. Returns true if the parsing was
  * successful and type_out contains the type of the hostname. Else, false is
  * returned which means it was not recognized and type_out is set to
@@ -1675,6 +1692,14 @@ parse_extended_hostname(char *address, hostname_type_t *type_out)
   if (q != address) {
     memmove(address, q, strlen(q) + 1 /* also get \0 */);
   }
+  /* v2 onion address check. */
+  if (strlen(query) == REND_SERVICE_ID_LEN_BASE32) {
+    *type_out = ONION_V2_HOSTNAME;
+    if (rend_valid_v2_service_id(query)) {
+      goto success;
+    }
+    goto failed;
+  }
 
   /* v3 onion address check. */
   if (strlen(query) == HS_SERVICE_ADDR_LEN_BASE32) {
@@ -1694,7 +1719,8 @@ parse_extended_hostname(char *address, hostname_type_t *type_out)
  failed:
   /* otherwise, return to previous state and return 0 */
   *s = '.';
-  const bool is_onion = (*type_out == ONION_V3_HOSTNAME);
+  const bool is_onion = (*type_out == ONION_V2_HOSTNAME) ||
+    (*type_out == ONION_V3_HOSTNAME);
   log_warn(LD_APP, "Invalid %shostname %s; rejecting",
            is_onion ? "onion " : "",
            safe_str_client(address));

src/core/or/connection_edge.h

@@ -80,6 +80,7 @@ typedef enum hostname_type_t {
   BAD_HOSTNAME,
   EXIT_HOSTNAME,
   NORMAL_HOSTNAME,
+  ONION_V2_HOSTNAME,
   ONION_V3_HOSTNAME,
 } hostname_type_t;
 

src/test/test_hs_common.c

@@ -789,6 +789,8 @@ test_parse_extended_hostname(void *arg)
   char address1[] = "fooaddress.onion";
   char address3[] = "fooaddress.exit";
   char address4[] = "www.torproject.org";
+  char address5[] = "foo.abcdefghijklmnop.onion";
+  char address6[] = "foo.bar.abcdefghijklmnop.onion";
   char address7[] = ".abcdefghijklmnop.onion";
   char address8[] =
     "www.25njqamcweflpvkl73j4szahhihoc4xt3ktcgjnpaingr5yhkenl5sid.onion";
@@ -806,6 +808,14 @@ test_parse_extended_hostname(void *arg)
   tt_assert(parse_extended_hostname(address4, &type));
   tt_int_op(type, OP_EQ, NORMAL_HOSTNAME);
 
+  tt_assert(parse_extended_hostname(address5, &type));
+  tt_int_op(type, OP_EQ, ONION_V2_HOSTNAME);
+  tt_str_op(address5, OP_EQ, "abcdefghijklmnop");
+
+  tt_assert(parse_extended_hostname(address6, &type));
+  tt_int_op(type, OP_EQ, ONION_V2_HOSTNAME);
+  tt_str_op(address6, OP_EQ, "abcdefghijklmnop");
+
   tt_assert(!parse_extended_hostname(address7, &type));
   tt_int_op(type, OP_EQ, BAD_HOSTNAME);