[systemd-devel] [PATCH 1/2] dhcp-network: add check for DHCP.chaddr
Michal Sekletar
msekleta at redhat.com
Mon Jul 7 05:06:53 PDT 2014
On Tue, Jun 24, 2014 at 03:54:54PM +0200, Tom Gundersen wrote:
> On Tue, Jun 24, 2014 at 12:58 PM, Michal Sekletar <msekleta at redhat.com> wrote:
> > On Thu, Jun 19, 2014 at 12:02:39PM -0500, Dan Williams wrote:
> >> On Thu, 2014-06-19 at 18:59 +0200, Michal Sekletar wrote:
> >> > Check that received DHCP packets actually include our MAC address in
> >> > chaddr field. BPF interpreter has 32 bit wide registers but MAC address
> >> > is 48 bits long so we have to do check in two steps.
> >>
> >> And if the MAC address is not 48 bits (Infiniband) or the interface type
> >> doesn't really have a MAC address (PPP/PPPoE)? DHCP can be used in both
> >> cases... If anything, the code that uses the MAC address should be
> >> if-ed so it only executes when a MAC address is provided.
> >
> > I reconsidered. In filter code I can very easily find out type of device to which
> > filter is attached and skip ethernet specific bits or fallback to something
> > else. However filter already assumes ethernet data-link type moreover there is a ton of
> > code in networkd which does likewise.
> >
> > I think we should merge patch as is right now. If somebody will hack up patches
> > for supporting various data-link types I will be happy to patch filter
> > accordingly.
>
> Ok. I'm fine with that. Please push.
Applied!
>
> Just to make clear: I'd be happy if anyone wanted to turn all our libs
> to work also on non-ethernet (and test it!), and would merge such
> patches.
>
> Cheers,
>
> Tom
>
> >> > src/libsystemd-network/dhcp-internal.h | 3 ++-
> >> > src/libsystemd-network/dhcp-network.c | 15 +++++++++++++--
> >> > src/libsystemd-network/sd-dhcp-client.c | 4 ++--
> >> > src/libsystemd-network/test-dhcp-client.c | 2 +-
> >> > 4 files changed, 18 insertions(+), 6 deletions(-)
> >> >
> >> > diff --git a/src/libsystemd-network/dhcp-internal.h b/src/libsystemd-network/dhcp-internal.h
> >> > index 03cc824..fd86a70 100644
> >> > --- a/src/libsystemd-network/dhcp-internal.h
> >> > +++ b/src/libsystemd-network/dhcp-internal.h
> >> > @@ -24,12 +24,13 @@
> >> >
> >> > #include <stdint.h>
> >> > #include <linux/if_packet.h>
> >> > +#include <net/ethernet.h>
> >> >
> >> > #include "socket-util.h"
> >> >
> >> > #include "dhcp-protocol.h"
> >> >
> >> > -int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t xid);
> >> > +int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t xid, struct ether_addr mac_addr);
> >> > int dhcp_network_bind_udp_socket(be32_t address, uint16_t port);
> >> > int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
> >> > const void *packet, size_t len);
> >> > diff --git a/src/libsystemd-network/dhcp-network.c b/src/libsystemd-network/dhcp-network.c
> >> > index d7ba0ef..e5fd6a8 100644
> >> > --- a/src/libsystemd-network/dhcp-network.c
> >> > +++ b/src/libsystemd-network/dhcp-network.c
> >> > @@ -33,7 +33,7 @@
> >> > #include "dhcp-internal.h"
> >> >
> >> > int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
> >> > - uint32_t xid) {
> >> > + uint32_t xid, struct ether_addr mac_addr) {
> >> > struct sock_filter filter[] = {
> >> > BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0), /* A <- packet length */
> >> > BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0), /* packet >= DHCPPacket ? */
> >> > @@ -56,7 +56,18 @@ int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
> >> > BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)), /* A <- client identifier */
> >> > BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0), /* client identifier == xid ? */
> >> > BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
> >> > - /* TODO: match chaddr */
> >> > + BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((unsigned int *) &mac_addr))), /* A <- 4 bytes of client's MAC */
> >> > + BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
> >> > + BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)), /* A <- 4 bytes of MAC from dhcp.chaddr */
> >> > + BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
> >> > + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0), /* A == 0 ? */
> >> > + BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
> >> > + BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((unsigned short *) (((char *) &mac_addr) + 4)))), /* A <- remainder of client's MAC */
> >> > + BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
> >> > + BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4), /* A <- remainder of MAC from dhcp.chaddr */
> >> > + BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
> >> > + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0), /* A == 0 ? */
> >> > + BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
> >> > BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)), /* A <- DHCP magic cookie */
> >> > BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0), /* cookie == DHCP magic cookie ? */
> >> > BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
> >> > diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
> >> > index c1af6df..d44cad2 100644
> >> > --- a/src/libsystemd-network/sd-dhcp-client.c
> >> > +++ b/src/libsystemd-network/sd-dhcp-client.c
> >> > @@ -719,7 +719,7 @@ static int client_start(sd_dhcp_client *client) {
> >> >
> >> > client->xid = random_u32();
> >> >
> >> > - r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid);
> >> > + r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid, client->client_id.mac_addr);
> >> > if (r < 0) {
> >> > client_stop(client, r);
> >> > return r;
> >> > @@ -761,7 +761,7 @@ static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata)
> >> > client->state = DHCP_STATE_REBINDING;
> >> > client->attempt = 1;
> >> >
> >> > - r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid);
> >> > + r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid, client->client_id.mac_addr);
> >> > if (r < 0) {
> >> > client_stop(client, r);
> >> > return 0;
> >> > diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
> >> > index 450b6d4..7cbe10d 100644
> >> > --- a/src/libsystemd-network/test-dhcp-client.c
> >> > +++ b/src/libsystemd-network/test-dhcp-client.c
> >> > @@ -196,7 +196,7 @@ int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
> >> > return 575;
> >> > }
> >> >
> >> > -int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t id)
> >> > +int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t id, struct ether_addr mac)
> >> > {
> >> > if (socketpair(AF_UNIX, SOCK_STREAM, 0, test_fd) < 0)
> >> > return -errno;
> >>
> >>
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