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List:       busybox
Subject:    Re: [PATCH] udhcpc: Prevent read of option length field beyond end of packet
From:       Denys Vlasenko <vda.linux () googlemail ! com>
Date:       2016-10-25 12:27:30
Message-ID: CAK1hOcPtuMtWOAvwPAO80HPdf3SqNeMKYNe3sDR5PYnB69Ky6g () mail ! gmail ! com
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Applied, thanks!

On Wed, Oct 12, 2016 at 10:53 PM, Brian Foley <bpfoley@google.com> wrote:
>
>
> Signed-off-by: Brian Foley <bpfoley@google.com>
> ---
>  networking/udhcp/common.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
> index 0cf4dab..b6feffd 100644
> --- a/networking/udhcp/common.c
> +++ b/networking/udhcp/common.c
> @@ -225,10 +225,13 @@ uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
>         optionptr = packet->options;
>         rem = sizeof(packet->options);
>         while (1) {
> +               /* Is there enough option payload left to read the option code? */
>                 if (rem <= 0) {
>                         bb_error_msg("bad packet, malformed option field");
>                         return NULL;
>                 }
> +
> +               /* DHCP_PADDING and DHCP_END have no extra option fields */
>                 if (optionptr[OPT_CODE] == DHCP_PADDING) {
>                         rem--;
>                         optionptr++;
> @@ -251,6 +254,12 @@ uint8_t* FAST_FUNC udhcp_get_option(struct dhcp_packet *packet, int code)
>                         }
>                         break;
>                 }
> +
> +               /* All other options must have at least a 1 byte len field */
> +               if (rem <= 1) {
> +                       bb_error_msg("bad packet, malformed option field");
> +                       return NULL;
> +               }
>                 len = 2 + optionptr[OPT_LEN];
>                 rem -= len;
>                 if (rem < 0)
> --
> 2.7.4
>
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