Add a BASE32_DIGEST_LEN define

Use this value instead of hardcoded values of 32 everywhere. This also
addresses the use of REND_DESC_ID_V2_LEN_BASE32 in
hs_lookup_last_hid_serv_request() for the HSDir encoded identity digest length
which is accurate but semantically wrong.

Fixes #23305.

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

src/common/crypto.h

@@ -73,6 +73,9 @@
 /** Length of our DH keys. */
 #define DH_BYTES (1024/8)
 
+/** Length of a sha1 message digest when encoded in base32 with trailing =
+ * signs removed. */
+#define BASE32_DIGEST_LEN 32
 /** Length of a sha1 message digest when encoded in base64 with trailing =
  * signs removed. */
 #define BASE64_DIGEST_LEN 27

src/or/hs_common.c

@@ -1453,7 +1453,7 @@ hs_lookup_last_hid_serv_request(routerstatus_t *hs_dir,
                                 const char *req_key_str,
                                 time_t now, int set)
 {
-  char hsdir_id_base32[REND_DESC_ID_V2_LEN_BASE32 + 1];
+  char hsdir_id_base32[BASE32_DIGEST_LEN + 1];
   char *hsdir_desc_comb_id = NULL;
   time_t *last_request_ptr;
   strmap_t *last_hid_serv_requests = get_last_hid_serv_requests();

src/or/or.h

@@ -747,15 +747,15 @@ typedef enum {
 #define REND_NUMBER_OF_CONSECUTIVE_REPLICAS 3
 
 /** Length of v2 descriptor ID (32 base32 chars = 160 bits). */
-#define REND_DESC_ID_V2_LEN_BASE32 32
+#define REND_DESC_ID_V2_LEN_BASE32 BASE32_DIGEST_LEN
 
 /** Length of the base32-encoded secret ID part of versioned hidden service
  * descriptors. */
-#define REND_SECRET_ID_PART_LEN_BASE32 32
+#define REND_SECRET_ID_PART_LEN_BASE32 BASE32_DIGEST_LEN
 
 /** Length of the base32-encoded hash of an introduction point's
  * identity key. */
-#define REND_INTRO_POINT_ID_LEN_BASE32 32
+#define REND_INTRO_POINT_ID_LEN_BASE32 BASE32_DIGEST_LEN
 
 /** Length of the descriptor cookie that is used for client authorization
  * to hidden services. */