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Message-Id: <20180720130906.27687-35-pablo@netfilter.org>
Date: Fri, 20 Jul 2018 15:09:02 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 34/38] netfilter: nf_osf: add struct nf_osf_hdr_ctx
Wrap context that allow us to guess the OS into a structure.
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
net/netfilter/nf_osf.c | 105 +++++++++++++++++++++++++++++--------------------
1 file changed, 62 insertions(+), 43 deletions(-)
diff --git a/net/netfilter/nf_osf.c b/net/netfilter/nf_osf.c
index bd7b34dd7d87..b44d62d5d9a9 100644
--- a/net/netfilter/nf_osf.c
+++ b/net/netfilter/nf_osf.c
@@ -51,18 +51,25 @@ static inline int nf_osf_ttl(const struct sk_buff *skb,
return ip->ttl == f_ttl;
}
+struct nf_osf_hdr_ctx {
+ bool df;
+ u16 window;
+ u16 totlen;
+ const unsigned char *optp;
+ unsigned int optsize;
+};
+
static bool nf_osf_match_one(const struct sk_buff *skb,
const struct nf_osf_user_finger *f,
- int ttl_check, u16 totlen, u16 window,
- const unsigned char *optp,
- unsigned int optsize)
+ int ttl_check,
+ struct nf_osf_hdr_ctx *ctx)
{
unsigned int check_WSS = 0;
int fmatch = FMATCH_WRONG;
int foptsize, optnum;
u16 mss = 0;
- if (totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))
+ if (ctx->totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))
return false;
/*
@@ -78,24 +85,24 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
foptsize += f->opt[optnum].length;
if (foptsize > MAX_IPOPTLEN ||
- optsize > MAX_IPOPTLEN ||
- optsize != foptsize)
+ ctx->optsize > MAX_IPOPTLEN ||
+ ctx->optsize != foptsize)
return false;
check_WSS = f->wss.wc;
for (optnum = 0; optnum < f->opt_num; ++optnum) {
- if (f->opt[optnum].kind == (*optp)) {
+ if (f->opt[optnum].kind == *ctx->optp) {
__u32 len = f->opt[optnum].length;
- const __u8 *optend = optp + len;
+ const __u8 *optend = ctx->optp + len;
fmatch = FMATCH_OK;
- switch (*optp) {
+ switch (*ctx->optp) {
case OSFOPT_MSS:
- mss = optp[3];
+ mss = ctx->optp[3];
mss <<= 8;
- mss |= optp[2];
+ mss |= ctx->optp[2];
mss = ntohs((__force __be16)mss);
break;
@@ -103,7 +110,7 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
break;
}
- optp = optend;
+ ctx->optp = optend;
} else
fmatch = FMATCH_OPT_WRONG;
@@ -116,7 +123,7 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
switch (check_WSS) {
case OSF_WSS_PLAIN:
- if (f->wss.val == 0 || window == f->wss.val)
+ if (f->wss.val == 0 || ctx->window == f->wss.val)
fmatch = FMATCH_OK;
break;
case OSF_WSS_MSS:
@@ -128,19 +135,19 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
*/
#define SMART_MSS_1 1460
#define SMART_MSS_2 1448
- if (window == f->wss.val * mss ||
- window == f->wss.val * SMART_MSS_1 ||
- window == f->wss.val * SMART_MSS_2)
+ if (ctx->window == f->wss.val * mss ||
+ ctx->window == f->wss.val * SMART_MSS_1 ||
+ ctx->window == f->wss.val * SMART_MSS_2)
fmatch = FMATCH_OK;
break;
case OSF_WSS_MTU:
- if (window == f->wss.val * (mss + 40) ||
- window == f->wss.val * (SMART_MSS_1 + 40) ||
- window == f->wss.val * (SMART_MSS_2 + 40))
+ if (ctx->window == f->wss.val * (mss + 40) ||
+ ctx->window == f->wss.val * (SMART_MSS_1 + 40) ||
+ ctx->window == f->wss.val * (SMART_MSS_2 + 40))
fmatch = FMATCH_OK;
break;
case OSF_WSS_MODULO:
- if ((window % f->wss.val) == 0)
+ if ((ctx->window % f->wss.val) == 0)
fmatch = FMATCH_OK;
break;
}
@@ -149,54 +156,66 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
return fmatch == FMATCH_OK;
}
+static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx,
+ const struct sk_buff *skb,
+ const struct iphdr *ip,
+ unsigned char *opts)
+{
+ const struct tcphdr *tcp;
+ struct tcphdr _tcph;
+
+ tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
+ if (!tcp)
+ return NULL;
+
+ if (!tcp->syn)
+ return NULL;
+
+ ctx->totlen = ntohs(ip->tot_len);
+ ctx->df = ntohs(ip->frag_off) & IP_DF;
+ ctx->window = ntohs(tcp->window);
+
+ if (tcp->doff * 4 > sizeof(struct tcphdr)) {
+ ctx->optsize = tcp->doff * 4 - sizeof(struct tcphdr);
+
+ ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) +
+ sizeof(struct tcphdr), ctx->optsize, opts);
+ }
+
+ return tcp;
+}
+
bool
nf_osf_match(const struct sk_buff *skb, u_int8_t family,
int hooknum, struct net_device *in, struct net_device *out,
const struct nf_osf_info *info, struct net *net,
const struct list_head *nf_osf_fingers)
{
- const unsigned char *optp = NULL, *_optp = NULL;
const struct iphdr *ip = ip_hdr(skb);
const struct nf_osf_user_finger *f;
unsigned char opts[MAX_IPOPTLEN];
const struct nf_osf_finger *kf;
int fcount = 0, ttl_check;
int fmatch = FMATCH_WRONG;
- unsigned int optsize = 0;
+ struct nf_osf_hdr_ctx ctx;
const struct tcphdr *tcp;
- struct tcphdr _tcph;
- u16 window, totlen;
- bool df;
- tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
- if (!tcp)
- return false;
+ memset(&ctx, 0, sizeof(ctx));
- if (!tcp->syn)
+ tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts);
+ if (!tcp)
return false;
- totlen = ntohs(ip->tot_len);
- df = ntohs(ip->frag_off) & IP_DF;
- window = ntohs(tcp->window);
-
- if (tcp->doff * 4 > sizeof(struct tcphdr)) {
- optsize = tcp->doff * 4 - sizeof(struct tcphdr);
-
- _optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
- sizeof(struct tcphdr), optsize, opts);
- }
-
ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : -1;
- list_for_each_entry_rcu(kf, &nf_osf_fingers[df], finger_entry) {
+ list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
f = &kf->finger;
if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))
continue;
- if (!nf_osf_match_one(skb, f,
- ttl_check, totlen, window, optp, optsize))
+ if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
continue;
fmatch = FMATCH_OK;
--
2.11.0
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