On Fri, 8 Mar 2019 12:34:18 +0100
Daniel Kiper <daniel.ki...@oracle.com> wrote:
> On Thu, Mar 07, 2019 at 03:14:09PM +0000, Andre Przywara wrote:
> > From: Andrei Borzenkov <arvidj...@gmail.com>
> >
> > DHCP specifies a special dummy option OVERLOAD, to allow DHCP options to
> > spill over into the (legacy) BOOTFILE and SNAME fields.
> >
> > Parse and handle this option properly.
> >
> > Signed-off-by: Andre Przywara <andre.przyw...@arm.com>
>
> In general Reviewed-by: Daniel Kiper <daniel.ki...@oracle.com> but one
> nitpick below...
>
> > ---
> > grub-core/net/bootp.c | 59 ++++++++++++++++++++++++++++++++++++++++++-
> > include/grub/net.h | 1 +
> > 2 files changed, 59 insertions(+), 1 deletion(-)
> >
> > diff --git a/grub-core/net/bootp.c b/grub-core/net/bootp.c
> > index 8d6763689..860d9c80d 100644
> > --- a/grub-core/net/bootp.c
> > +++ b/grub-core/net/bootp.c
> > @@ -25,11 +25,19 @@
> > #include <grub/net/udp.h>
> > #include <grub/datetime.h>
> >
> > +enum
> > +{
> > + GRUB_DHCP_OPT_OVERLOAD_FILE = 1,
> > + GRUB_DHCP_OPT_OVERLOAD_SNAME = 2,
> > +};
> > +
> > static const void *
> > find_dhcp_option (const struct grub_net_bootp_packet *bp, grub_size_t size,
> > grub_uint8_t opt_code, grub_uint8_t *opt_len)
> > {
> > const grub_uint8_t *ptr;
> > + grub_uint8_t overload = 0;
> > + int end = 0;
> > grub_size_t i;
> >
> > if (opt_len)
> > @@ -54,6 +62,7 @@ find_dhcp_option (const struct grub_net_bootp_packet *bp,
> > grub_size_t size,
> > size -= sizeof (*bp);
> > i = sizeof (grub_uint32_t);
> >
> > +again:
> > while (i < size)
> > {
> > grub_uint8_t tagtype;
> > @@ -67,7 +76,10 @@ find_dhcp_option (const struct grub_net_bootp_packet
> > *bp, grub_size_t size,
> >
> > /* End tag. */
> > if (tagtype == GRUB_NET_BOOTP_END)
> > - break;
> > + {
> > + end = 1;
> > + break;
> > + }
> >
> > if (i >= size)
> > return NULL;
> > @@ -84,9 +96,54 @@ find_dhcp_option (const struct grub_net_bootp_packet
> > *bp, grub_size_t size,
> > return &ptr[i];
> > }
> >
> > + if (tagtype == GRUB_NET_DHCP_OVERLOAD && taglength == 1)
> > + overload = ptr[i];
> > +
> > i += taglength;
> > }
> >
> > + if (!end)
> > + return NULL;
> > +
> > + /* RFC2131, 4.1, 23ff:
> > + * If the options in a DHCP message extend into the 'sname' and 'file'
> > + * fields, the 'option overload' option MUST appear in the 'options'
> > + * field, with value 1, 2 or 3, as specified in RFC 1533. If the
> > + * 'option overload' option is present in the 'options' field, the
> > + * options in the 'options' field MUST be terminated by an 'end' option,
> > + * and MAY contain one or more 'pad' options to fill the options field.
> > + * The options in the 'sname' and 'file' fields (if in use as indicated
> > + * by the 'options overload' option) MUST begin with the first octet of
> > + * the field, MUST be terminated by an 'end' option, and MUST be
> > + * followed by 'pad' options to fill the remainder of the field. Any
> > + * individual option in the 'options', 'sname' and 'file' fields MUST be
> > + * entirely contained in that field. The options in the 'options' field
> > + * MUST be interpreted first, so that any 'option overload' options may
> > + * be interpreted. The 'file' field MUST be interpreted next (if the
> > + * 'option overload' option indicates that the 'file' field contains
> > + * DHCP options), followed by the 'sname' field.
> > + *
> > + * FIXME: We do not explicitly check for trailing 'pad' options here.
> > + */
> > + end = 0;
>
> It seems to me that this line is not needed... I can drop it before
> committing the patch if you are OK with it.
I was eyeballing this line as well, but I think it *is* needed:
It resets end to 0, before possibly jumping back to the again label, inside the
if conditions below.
Does that make sense?
Cheers,
Andre.
>
> > + if (overload & GRUB_DHCP_OPT_OVERLOAD_FILE)
> > + {
> > + overload &= ~GRUB_DHCP_OPT_OVERLOAD_FILE;
> > + ptr = (grub_uint8_t *) &bp->boot_file[0];
> > + size = sizeof (bp->boot_file);
> > + i = 0;
> > + goto again;
> > + }
> > +
> > + if (overload & GRUB_DHCP_OPT_OVERLOAD_SNAME)
> > + {
> > + overload &= ~GRUB_DHCP_OPT_OVERLOAD_SNAME;
> > + ptr = (grub_uint8_t *) &bp->server_name[0];
> > + size = sizeof (bp->server_name);
> > + i = 0;
> > + goto again;
> > + }
> > +
> > return NULL;
> > }
>
> Daniel
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