1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
|
From e8d5dfd1d8747b56077d02664a8838c71ced948e Mon Sep 17 00:00:00 2001
From: David Leadbeater <dgl@dgl.cx>
Date: Fri, 26 Aug 2022 14:56:57 +1000
Subject: [PATCH] netfilter: nf_conntrack_irc: Tighten matching on DCC message
CTCP messages should only be at the start of an IRC message, not
anywhere within it.
While the helper only decodes packes in the ORIGINAL direction, its
possible to make a client send a CTCP message back by empedding one into
a PING request. As-is, thats enough to make the helper believe that it
saw a CTCP message.
Fixes: 869f37d8e48f ("[NETFILTER]: nf_conntrack/nf_nat: add IRC helper port")
Signed-off-by: David Leadbeater <dgl@dgl.cx>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
net/netfilter/nf_conntrack_irc.c | 34 ++++++++++++++++++++++++++------
1 file changed, 28 insertions(+), 6 deletions(-)
diff --git a/net/netfilter/nf_conntrack_irc.c b/net/netfilter/nf_conntrack_irc.c
index 992decbcaa5c1e..5703846bea3b69 100644
--- a/net/netfilter/nf_conntrack_irc.c
+++ b/net/netfilter/nf_conntrack_irc.c
@@ -157,15 +157,37 @@ static int help(struct sk_buff *skb, unsigned int protoff,
data = ib_ptr;
data_limit = ib_ptr + datalen;
- /* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
- * 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
- while (data < data_limit - (19 + MINMATCHLEN)) {
- if (memcmp(data, "\1DCC ", 5)) {
+ /* Skip any whitespace */
+ while (data < data_limit - 10) {
+ if (*data == ' ' || *data == '\r' || *data == '\n')
+ data++;
+ else
+ break;
+ }
+
+ /* strlen("PRIVMSG x ")=10 */
+ if (data < data_limit - 10) {
+ if (strncasecmp("PRIVMSG ", data, 8))
+ goto out;
+ data += 8;
+ }
+
+ /* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26
+ * 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26
+ */
+ while (data < data_limit - (21 + MINMATCHLEN)) {
+ /* Find first " :", the start of message */
+ if (memcmp(data, " :", 2)) {
data++;
continue;
}
+ data += 2;
+
+ /* then check that place only for the DCC command */
+ if (memcmp(data, "\1DCC ", 5))
+ goto out;
data += 5;
- /* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
+ /* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */
iph = ip_hdr(skb);
pr_debug("DCC found in master %pI4:%u %pI4:%u\n",
@@ -181,7 +203,7 @@ static int help(struct sk_buff *skb, unsigned int protoff,
pr_debug("DCC %s detected\n", dccprotos[i]);
/* we have at least
- * (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
+ * (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid
* data left (== 14/13 bytes) */
if (parse_dcc(data, data_limit, &dcc_ip,
&dcc_port, &addr_beg_p, &addr_end_p)) {
|
