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o IPFW incorrectly handled filtering in the presence of previously

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reserved and now allocated TCP flags in incoming packets.  This patch
  stops overloading those bits in the IP firewall rules, and moves
  colliding flags to a seperate field, ipflg.  The IPFW userland
  management tool, ipfw(8), is updated to reflect this change.  New TCP
  flags related to ECN are now included in tcp.h for reference, although
  we don't currently implement TCP+ECN.

o To use this fix without completely rebuilding, it is sufficient to copy
  ip_fw.h and tcp.h into your appropriate include directory, then rebuild
  the ipfw kernel module, and ipfw tool, and install both.  Note that a
  mismatch between module and userland tool will result in incorrect
  installation of firewall rules that may have unexpected effects.  This
  is an MFC candidate, following shakedown.  This bug does not appear
  to affect ipfilter.

Reviewed by:	security-officer, billf
Reported by:	Aragon Gouveia <aragon@phat.za.net>
This commit is contained in:
Robert Watson 2001-01-09 03:10:30 +00:00
parent 3fc3cadde6
commit 65450f2f77
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=70826
4 changed files with 20 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
sbin/ipfw/ipfw.c
View File

@ -453,7 +453,7 @@ show_ipfw(struct ip_fw *chain, int pcwidth, int bcwidth)
if (chain->fw_ipflg & IP_FW_IF_IPVER)
printf(" ipversion %u", chain->fw_ipver);
if (chain->fw_tcpf & IP_FW_TCPF_ESTAB)
if (chain->fw_ipflg & IP_FW_IF_TCPEST)
printf(" established");
else if (chain->fw_tcpf == IP_FW_TCPF_SYN &&
chain->fw_tcpnf == IP_FW_TCPF_ACK)
@ -2025,8 +2025,7 @@ add(ac,av)
}
if (rule.fw_prot == IPPROTO_TCP) {
if (!strncmp(*av,"established",strlen(*av))) {
rule.fw_tcpf |= IP_FW_TCPF_ESTAB;
rule.fw_ipflg |= IP_FW_IF_TCPFLG;
rule.fw_ipflg |= IP_FW_IF_TCPEST;
av++; ac--; continue;
}
if (!strncmp(*av,"setup",strlen(*av))) {

18
sys/netinet/ip_fw.c
View File

@ -244,10 +244,16 @@ static int
tcpflg_match(struct tcphdr *tcp, struct ip_fw *f)
{
u_char flg_set, flg_clr;
if ((f->fw_tcpf & IP_FW_TCPF_ESTAB) &&
(tcp->th_flags & (IP_FW_TCPF_RST | IP_FW_TCPF_ACK)))
return 1;
/*
* If an established connection is required, reject packets that
* have only SYN of RST|ACK|SYN set. Otherwise, fall through to
* other flag requirements.
*/
if ((f->fw_ipflg & IP_FW_IF_TCPEST) &&
((tcp->th_flags & (IP_FW_TCPF_RST | IP_FW_TCPF_ACK |
IP_FW_TCPF_SYN)) == IP_FW_TCPF_SYN))
return 0;
flg_set = tcp->th_flags & f->fw_tcpf;
flg_clr = tcp->th_flags & f->fw_tcpnf;
@ -1243,7 +1249,9 @@ ip_fw_chk(struct ip **pip, int hlen,
if (f->fw_ipflg & IP_FW_IF_TCPOPT && !tcpopts_match(tcp, f))
continue;
if (f->fw_ipflg & IP_FW_IF_TCPFLG && !tcpflg_match(tcp, f))
if (((f->fw_ipflg & IP_FW_IF_TCPFLG) ||
(f->fw_ipflg & IP_FW_IF_TCPEST)) &&
!tcpflg_match(tcp, f))
continue;
if (f->fw_ipflg & IP_FW_IF_TCPSEQ && tcp->th_seq != f->fw_tcpseq)
continue;

4
sys/netinet/ip_fw.h
View File

@ -222,7 +222,8 @@ struct ipfw_dyn_rule {
#define IP_FW_IF_TCPSEQ 0x00000004 /* tcp sequence number */
#define IP_FW_IF_TCPACK 0x00000008 /* tcp acknowledgement number */
#define IP_FW_IF_TCPWIN 0x00000010 /* tcp window size */
#define IP_FW_IF_TCPMSK 0x0000001f /* mask of all tcp values */
#define IP_FW_IF_TCPEST 0x00000020 /* established TCP connection */
#define IP_FW_IF_TCPMSK 0x0000003f /* mask of all tcp values */
#define IP_FW_IF_IPOPT 0x00000100 /* ip options */
#define IP_FW_IF_IPLEN 0x00000200 /* ip length */
@ -274,7 +275,6 @@ struct ipfw_dyn_rule {
#define IP_FW_TCPF_PSH TH_PUSH
#define IP_FW_TCPF_ACK TH_ACK
#define IP_FW_TCPF_URG TH_URG
#define IP_FW_TCPF_ESTAB 0x40
/*
* Main firewall chains definitions and global var's definitions.

4
sys/netinet/tcp.h
View File

@ -67,7 +67,9 @@ struct tcphdr {
#define TH_PUSH 0x08
#define TH_ACK 0x10
#define TH_URG 0x20
#define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG)
#define TH_ECE 0x40
#define TH_CWR 0x80
#define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR)
u_short th_win; /* window */
u_short th_sum; /* checksum */