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Hauke Mehrtens
63c0767f3d
handle_send_a() computed the SRP "A" parameter length as
len = ntohl(msg->len) - sizeof(struct ead_msg_number);
sizeof(struct ead_msg_number) is 1, and the subtraction is evaluated in
unsigned arithmetic. A packet with msg->len == 0 therefore wraps the
result to a huge value which, assigned to the signed int len, becomes -1.
The following bounds check is signed:
if (len > MAXPARAMLEN + 1)
return false;
so -1 passes, and memcpy(A.data, number->data, len) runs with len cast to
size_t (~SIZE_MAX) against the 257-byte abuf, crashing the daemon.
Neither parse_message() nor handle_packet() validate msg->len (only the
captured packet length), so an unauthenticated attacker on the local
segment can reach this path and crash ead with a single crafted packet.
Validate the claimed length in unsigned arithmetic before the subtraction
and bound it on both sides. Doing the upper-bound check unsigned as well
also closes a 32-bit-only variant where sizeof(ead_packet) + msg->len
overflows in handle_packet(), letting a large msg->len reach the same
negative-len path.
Link: https://github.com/openwrt/openwrt/security/advisories/GHSA-9558-77jp-g3fw
Reported-by: @Vasco0x4
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>