buglwIP - A Lightweight TCP/IP stack - Bugs: bug #61479, MQTT: DoS caused by unsigned...

 
 

You are not allowed to post comments on this tracker with your current authentication level.

bug #61479: MQTT: DoS caused by unsigned integer overflow

Submitter:  Hyeonsu Kim <icekrim>
Submitted:  Sun 14 Nov 2021 06:31:19 AM UTC
   
 
Category:  Security-related Severity:  3 - Normal
Item Group:  Crash Error Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open Planned Release:  None
lwIP version:  git head

Sun 14 Nov 2021 06:31:19 AM UTC, original submission:  

Summary:
Integer overflow in mqtt_parse_incoming of src/apps/mqtt/mqtt.c allows attackers to perform a Denial of Service via MQTT packet with fixed header length of 256 bytes or more

Description:

mqtt.c 866

while (p->tot_len > in_offset) {
if ((fixed_hdr_len < 2) || ((b & 0x80) != 0)) {
  if (fixed_hdr_len < client->msg_idx) {
    b = client->rx_buffer[fixed_hdr_len];
  } else {
    b = pbuf_get_at(p, in_offset++);
    client->rx_buffer[client->msg_idx++] = b;
  }
  fixed_hdr_len++;
  if (fixed_hdr_len >= 2) {
    msg_rem_len |= (u32_t)(b & 0x7f) << ((fixed_hdr_len - 2) * 7);
    if ((b & 0x80) == 0) {

....

If it receives a packet of 256 bytes with b & 80 == 1, it goes into an infinite loop and the device stops. (like [0x80]*256)

This is because fixed_hdr_len, which is a u8 type, can never be larger than client->msg_idx (in this case 256), so in_offset cannot be increased.

I have completed the POC on the stm32 board I have personally, and I will prepare linux porting if necessary. Thank you.

Hyeonsu Kim <icekrim>

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

No files currently attached

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -email is unavailable- added by icekrim (Submitted the item)
  •  

    There are 0 votes so far. Votes easily highlight which items people would like to see resolved in priority, independently of the priority of the item set by tracker managers.

     

    No changes have been made to this item

    Back to the top

    Powered by Savane 3.13-4448.
    Corresponding source code