oss-security - CVE Request: dhcpcd 3.2.3 remote stack overflow / denial of service

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120502160803.GH20471@suse.de>
Date: Wed, 2 May 2012 18:08:03 +0200
From: Marcus Meissner <meissner@...e.de>
To: OSS Security List <oss-security@...ts.openwall.com>
Subject: CVE Request: dhcpcd 3.2.3 remote stack overflow / denial of service

Hi,

I would like a CVE for following issue:

One of our customers reported a crash of dhcpcd (a DHCP client) version
3.2.3 as found in our products.

This was triggered by regular network traffic happening, so attackers
in the local network could inject such a packet.

The issue is apparently fixed in dhcpcd-4.0.2 (oldest GIT revision of
dhcpcd I can find), as it features the necessary checks on cursory review.

Problem is that the "to copyed" size of a packet is decoded from the network data
and not checked against the maximum size of the retrieved packet.

In dhcpcd 3.2.3 it is copied to a fixed size stackbuffer on some paths
and so overwrites stack.

On our SLE11 product this is caught by -fstack-protector, turning this
into a remote denial of service (crash).

Place to look for places like this:

                bytes = get_udp_data(&pp, packet);
                if ((size_t)bytes > sizeof(*dhcp)) {
                        syslog(LOG_ERR,
                            "%s: packet greater than DHCP size from %s",
                            iface->name, inet_ntoa(from));
                        continue;
                }

bytes is calculated from packet data and not bounded in get_udp_data().
So without the if() check, it would later copy over bytes into a fixed buffer
in some paths.

Also:
                bytes = packet.bh_caplen - ETHER_HDR_LEN;
                if (bytes > len)
                        bytes = len;
                memcpy(data, payload, bytes);

I have pasted the current patch we use against our quite heavily patches dhcpcd 3.2.3
on https://bugzilla.novell.com/show_bug.cgi?id=760334

Reference: https://bugzilla.novell.com/show_bug.cgi?id=760334

Ciao, Marcus

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.