bugfix in parsePacket(): accept short artnet packets

[DedeHai]

fixes #5584

Summary by CodeRabbit

• Bug Fixes
  • Enhanced protocol detection to properly validate Art-Net packets during network communication processing.

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[softhack007]

looks correct for me 👍 (not tested, as I don't have art-net equipment)

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

wled00/src/dependencies/e131/ESPAsyncE131.cpp (1)

102-117: ⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Add minimum-length guards before Art-Net field reads

After defaulting to P_ARTNET, undersized UDP packets can reach Line 114/Line 116 and dereference fields beyond the received buffer. Please gate the Art-Net branch with a minimum packet length (at least enough for art_id + opcode) before memcmp/opcode checks.

Proposed fix

 void ESPAsyncE131::parsePacket(AsyncUDPPacket _packet) {
   bool error = false;
   uint8_t protocol = P_ARTNET;
   const size_t pktLen = _packet.length();

   e131_packet_t *sbuff = reinterpret_cast<e131_packet_t *>(_packet.data());

   // E1.31 packet identifier (ACN_ID = "ASC-E1.17"), need at least 16 bytes to safely read acn_id (offset 4, length 12).
   if (pktLen >= 16) {
     if (!memcmp(sbuff->acn_id, ESPAsyncE131::ACN_ID, sizeof(sbuff->acn_id)))
       protocol = P_E131;
   }

   if (protocol == P_ARTNET) {
+    // Need at least Art-Net ID (8) + opcode (2)
+    if (pktLen < 10) {
+      error = true;
+    } else {
       if (memcmp(sbuff->art_id, ESPAsyncE131::ART_ID, sizeof(sbuff->art_id)))
         error = true; //not "Art-Net"
       if (sbuff->art_opcode != ARTNET_OPCODE_OPDMX && sbuff->art_opcode != ARTNET_OPCODE_OPPOLL)
         error = true; //not a DMX or poll packet
+    }
   } else { //E1.31 error handling

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@wled00/src/dependencies/e131/ESPAsyncE131.cpp` around lines 102 - 117, The
Art‑Net branch currently assumes the buffer is large enough and can read
sbuff->art_id and sbuff->art_opcode even for undersized packets; before the
protocol == P_ARTNET checks, add a minimum-length guard using pktLen to ensure
the packet is at least large enough to contain art_id and art_opcode (compare
against the sum of sizes used by art_id and opcode) and only then perform
memcmp(sbuff->art_id, ESPAsyncE131::ART_ID, ...) and the sbuff->art_opcode
checks; update the logic around protocol/P_ARTNET and error setting so
undersized packets are treated as error/ignored rather than dereferencing
out-of-bounds data.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@wled00/src/dependencies/e131/ESPAsyncE131.cpp`:
- Around line 102-117: The Art‑Net branch currently assumes the buffer is large
enough and can read sbuff->art_id and sbuff->art_opcode even for undersized
packets; before the protocol == P_ARTNET checks, add a minimum-length guard
using pktLen to ensure the packet is at least large enough to contain art_id and
art_opcode (compare against the sum of sizes used by art_id and opcode) and only
then perform memcmp(sbuff->art_id, ESPAsyncE131::ART_ID, ...) and the
sbuff->art_opcode checks; update the logic around protocol/P_ARTNET and error
setting so undersized packets are treated as error/ignored rather than
dereferencing out-of-bounds data.

---

ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 3a28eba and 0eeb010.

📒 Files selected for processing (1)

• wled00/src/dependencies/e131/ESPAsyncE131.cpp

[softhack007]

@DedeHai found this in the rabbit's "out-of-range comments" - might be worth to check.

⚠️ Outside diff range comments (1)

wled00/src/dependencies/e131/ESPAsyncE131.cpp (1)> 102-117: ⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Add minimum-length guards before Art-Net field reads
After defaulting to P_ARTNET, undersized UDP packets can reach Line 114/Line 116 and dereference fields beyond the received buffer. Please gate the Art-Net branch with a minimum packet length (at least enough for art_id + opcode) before memcmp/opcode checks.

Proposed fix

 void ESPAsyncE131::parsePacket(AsyncUDPPacket _packet) {
   bool error = false;
   uint8_t protocol = P_ARTNET;
   const size_t pktLen = _packet.length();

   e131_packet_t *sbuff = reinterpret_cast<e131_packet_t *>(_packet.data());

   // E1.31 packet identifier (ACN_ID = "ASC-E1.17"), need at least 16 bytes to safely read acn_id (offset 4, length 12).
   if (pktLen >= 16) {
     if (!memcmp(sbuff->acn_id, ESPAsyncE131::ACN_ID, sizeof(sbuff->acn_id)))
       protocol = P_E131;
   }

   if (protocol == P_ARTNET) {
+    // Need at least Art-Net ID (8) + opcode (2)
+    if (pktLen < 10) {
+      error = true;
+    } else {
       if (memcmp(sbuff->art_id, ESPAsyncE131::ART_ID, sizeof(sbuff->art_id)))
         error = true; //not "Art-Net"
       if (sbuff->art_opcode != ARTNET_OPCODE_OPDMX && sbuff->art_opcode != ARTNET_OPCODE_OPPOLL)
         error = true; //not a DMX or poll packet
+    }
   } else { //E1.31 error handling