From 1f2b14bb66390f8ec3cf40d95cb57d5da40b23a1 Mon Sep 17 00:00:00 2001
From: jnnrgd <bacem.b.achour@gmail.com>
Date: Wed, 30 Sep 2026 10:51:00 +0200
Subject: [PATCH] mqtt: parse properties in MQTT 5.0 CONNACK packets

Under MQTT 5.0, decode the property length and set props_start and
props_size for MQTT_CMD_CONNACK. Add unit test coverage.
---
 mongoose.c       | 10 ++++++++++
 src/mqtt.c       | 10 ++++++++++
 test/unit_test.c |  7 +++++++
 3 files changed, 27 insertions(+)

diff --git a/mongoose.c b/mongoose.c
index 2c25a143..aa7f4291 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -7779,6 +7779,16 @@ int mg_mqtt_parse(const uint8_t *buf, size_t len, uint8_t version,
     case MQTT_CMD_CONNACK:
       if (end - p < 2) return MQTT_MALFORMED;
       m->ack = p[1];
+      p += 2;
+      if (version == 5) {
+        if (p >= end) return MQTT_MALFORMED;
+        len_len = (uint32_t) decode_varint(p, (size_t) (end - p), &tmp);
+        if (!len_len) return MQTT_MALFORMED;
+        m->props_size = (size_t) tmp;
+        m->props_start = (size_t) (p + len_len - buf);
+        p += len_len + m->props_size;
+        if (p > end) return MQTT_MALFORMED;
+      }
       break;
     case MQTT_CMD_PUBACK:
     case MQTT_CMD_PUBREC:
diff --git a/src/mqtt.c b/src/mqtt.c
index 54ae5f40..8f85040e 100644
--- a/src/mqtt.c
+++ b/src/mqtt.c
@@ -438,6 +438,16 @@ int mg_mqtt_parse(const uint8_t *buf, size_t len, uint8_t version,
     case MQTT_CMD_CONNACK:
       if (end - p < 2) return MQTT_MALFORMED;
       m->ack = p[1];
+      p += 2;
+      if (version == 5) {
+        if (p >= end) return MQTT_MALFORMED;
+        len_len = (uint32_t) decode_varint(p, (size_t) (end - p), &tmp);
+        if (!len_len) return MQTT_MALFORMED;
+        m->props_size = (size_t) tmp;
+        m->props_start = (size_t) (p + len_len - buf);
+        p += len_len + m->props_size;
+        if (p > end) return MQTT_MALFORMED;
+      }
       break;
     case MQTT_CMD_PUBACK:
     case MQTT_CMD_PUBREC:
diff --git a/test/unit_test.c b/test/unit_test.c
index b5de3da6..f4b44e78 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -803,11 +803,18 @@ static void test_mqtt_parse(void) {
   struct mg_mqtt_prop prop;
   // MQTT5 PUBLISH with Subscription Identifier = 5
   const uint8_t sub_id_pkt[] = {0x30, 0x06, 0x00, 0x01, 'x', 0x02, 0x0B, 0x05};
+  // MQTT5 CONNACK with Server Keep Alive = 60
+  const uint8_t connack_pkt[] = {0x20, 0x06, 0x00, 0x00, 0x03, 0x13, 0x00, 0x3C};
 
   memset(&mm, 0, sizeof(struct mg_mqtt_message));
   memset(&prop, 0, sizeof(struct mg_mqtt_prop));
   ASSERT(mg_mqtt_parse(sub_id_pkt, sizeof(sub_id_pkt), 5, &mm) == MQTT_OK);
   mg_mqtt_next_prop(&mm, &prop, 0);
+
+  ASSERT(mg_mqtt_parse(connack_pkt, sizeof(connack_pkt), 5, &mm) == MQTT_OK);
+  ASSERT(mm.ack == 0);
+  ASSERT(mg_mqtt_next_prop(&mm, &prop, 0) > 0);
+  ASSERT(prop.id == MQTT_PROP_SERVER_KEEP_ALIVE && prop.iv == 60);
 }
 
 static void test_mqtt(void) {