[lwip-devel] [bug #58553] Memory disclosure for icmp6 in git master branch

[Wenqiang Li]

URL:
  <https://savannah.nongnu.org/bugs/?58553>

                 Summary: Memory disclosure for icmp6 in git master branch
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: silentdawn
            Submitted on: Fri 12 Jun 2020 05:22:10 PM UTC
                Category: Security-related
                Severity: 3 - Normal
              Item Group: Crash Error
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: git head

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Details:

Type:
Buffer overflow

Description:
his bug is related to bug #58552. We have observed the changes made to the
same place in the master branch. However, the bug still exists. The function
pbuf_take_at() replaces the function SMEMCPY() in the master branch. However,
it is still vulnerable.
The function pbuf_take_at() tries to copy fields from the original packet as
shown in line 409 of icmp6.c. The parameter len of the function pbuf_take_at()
is the length of another parameter dataptr. However, the function
icmp6_send_response_with_addrs_and_netif() passes the parameters p->payload
and p->tot_len to the function pbuf_take_at(), which are the total length of
the p->payload plus all payloads length of its following pbuf . If p->tot_len
is larger than the length of p->payload, the memory will leak to remote
attackers through the network. To fix this, the datalen should be p->len, not
p->tot_len.

        
385
static void icmp6_send_response_with_addrs_and_netif(struct pbuf *p, u8_t
code, u32_t data, u8_t type, const ip6_addr_t *reply_src, const ip6_addr_t
*reply_dest, struct netif *netif)
387
{

...
409
pbuf_take_at(q, p->payload, datalen, sizeof(struct icmp6_hdr));

...
423
}

Result:
Memory disclosure.





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