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On the first pass through the BOOTP options, check whether data exists 

before fetching it, so if an option is malformed, we don't throw an
exception before the second pass through the option, which is the pass
where they're dissected.

svn path=/trunk/; revision=4455
This commit is contained in:
Guy Harris 2001-12-27 22:49:02 +00:00
parent 2a5c22e024
commit e678fdece2
1 changed files with 34 additions and 10 deletions
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44
packet-bootp.c
View File

@ -2,10 +2,11 @@
* Routines for BOOTP/DHCP packet disassembly
* Gilbert Ramirez <gram@alumni.rice.edu>
*
* $Id: packet-bootp.c,v 1.59 2001/12/10 00:25:26 guy Exp $
* $Id: packet-bootp.c,v 1.60 2001/12/27 22:49:02 guy Exp $
*
* The information used comes from:
* RFC 951: Bootstrap Protocol
* RFC 1497: BOOTP extensions
* RFC 1542: Clarifications and Extensions for the Bootstrap Protocol
* RFC 2131: Dynamic Host Configuration Protocol
* RFC 2132: DHCP Options and BOOTP Vendor Extensions
@ -413,7 +414,24 @@ bootp_option(tvbuff_t *tvb, proto_tree *bp_tree, int voff, int eoff,
* Get the length of the option, and the number of bytes it
* consumes (the length doesn't include the option code or
* length bytes).
*
* On the first pass, check first whether we have the length
* byte, so that we don't throw an exception; if we throw an
* exception in the first pass, which is only checking for options
* whose values we need in order to properly dissect the packet
* on the second pass, we won't actually dissect the options, so
* you won't be able to see which option had the problem.
*/
if (first_pass) {
if (!tvb_bytes_exist(tvb, voff+1, 1)) {
/*
* We don't have the length byte; just return 1
* as the number of bytes we consumed, to count
* the code byte.
*/
return 1;
}
}
vlen = tvb_get_guint8(tvb, voff+1);
consumed = vlen + 2;
@ -426,19 +444,25 @@ bootp_option(tvbuff_t *tvb, proto_tree *bp_tree, int voff, int eoff,
*
* 60 (Vendor class identifier) - we need this in order to
* interpret the vendor-specific info
*
* We also check, before fetching anything, to make sure we
* have the entire item we're fetching, so that we don't throw
* an exception.
*/
if (first_pass) {
switch (code) {
if (tvb_bytes_exist(tvb, voff+2, consumed-2)) {
switch (code) {
case 53:
*dhcp_type_p =
get_dhcp_type(tvb_get_guint8(tvb, voff+2));
break;
case 53:
*dhcp_type_p =
get_dhcp_type(tvb_get_guint8(tvb, voff+2));
break;
case 60:
*vendor_class_id_p =
tvb_get_ptr(tvb, voff+2, consumed-2);
break;
case 60:
*vendor_class_id_p =
tvb_get_ptr(tvb, voff+2, consumed-2);
break;
}
}
/*