From 3f5ec5467a1dc00e92bed98d15295c253676b72a Mon Sep 17 00:00:00 2001
From: Jon Shallow <supjps-libcoap@jpshallow.com>
Date: Sat, 4 Dec 2021 11:51:32 +0000
Subject: [PATCH] coap_cache.c: Correctly build cache key

Include actual session address in the hash, not first 8 bytes of session.

Include actual option number in the hash, not the delta which may vary
if there are different non-cachable option across the payloads of a body.
---
 src/coap_cache.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/coap_cache.c b/src/coap_cache.c
index 19839f5a..211d7ceb 100644
--- a/src/coap_cache.c
+++ b/src/coap_cache.c
@@ -92,17 +92,20 @@ coap_cache_derive_key_w_ignore(const coap_session_t *session,
 
   if (session_based == COAP_CACHE_IS_SESSION_BASED) {
     /* Include the session ptr */
-    if (!coap_digest_update(dctx, (const uint8_t*)session, sizeof(session))) {
-      coap_digest_free(dctx);
-      return NULL;
+    if (!coap_digest_update(dctx, (const uint8_t*)&session, sizeof(session))) {
+      goto update_fail;
     }
   }
   while ((option = coap_option_next(&opt_iter))) {
     if (is_cache_key(opt_iter.number, cache_ignore_count,
                      cache_ignore_options)) {
-      if (!coap_digest_update(dctx, option, coap_opt_size(option))) {
-        coap_digest_free(dctx);
-        return NULL;
+      if (!coap_digest_update(dctx, (const uint8_t *)&opt_iter.number,
+                              sizeof(opt_iter.number))) {
+        goto update_fail;
+      }
+      if (!coap_digest_update(dctx, coap_opt_value(option),
+                              coap_opt_length(option))) {
+        goto update_fail;
       }
     }
   }
@@ -114,8 +117,7 @@ coap_cache_derive_key_w_ignore(const coap_session_t *session,
     const uint8_t *data;
     if (coap_get_data(pdu, &len, &data)) {
       if (!coap_digest_update(dctx, data, len)) {
-        coap_digest_free(dctx);
-        return NULL;
+        goto update_fail;
       }
     }
   }
@@ -129,6 +131,9 @@ coap_cache_derive_key_w_ignore(const coap_session_t *session,
     memcpy(cache_key->key, digest.key, sizeof(cache_key->key));
   }
   return cache_key;
+update_fail:
+  coap_digest_free(dctx);
+  return NULL;
 }
 
 coap_cache_key_t *