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netfilter: nf_osf: add nf_osf_match_one() 

This new function allows us to check if there is TCP syn packet matching
with a given fingerprint that can be reused from the upcoming new
nf_osf_find() function.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2018-07-13 14:54:43 +02:00
parent f102d66b33
commit 06ff4aa252
1 changed files with 111 additions and 96 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

123
net/netfilter/nf_osf.c
View File

@ -21,15 +21,14 @@
#include <linux/netfilter/nf_osf.h>
static inline int nf_osf_ttl(const struct sk_buff *skb,
const struct nf_osf_info *info,
unsigned char f_ttl)
int ttl_check, unsigned char f_ttl)
{
const struct iphdr *ip = ip_hdr(skb);
if (info->flags & NF_OSF_TTL) {
if (info->ttl == NF_OSF_TTL_TRUE)
if (ttl_check != -1) {
if (ttl_check == NF_OSF_TTL_TRUE)
return ip->ttl == f_ttl;
if (info->ttl == NF_OSF_TTL_NOCHECK)
if (ttl_check == NF_OSF_TTL_NOCHECK)
return 1;
else if (ip->ttl <= f_ttl)
return 1;
@ -52,61 +51,25 @@ static inline int nf_osf_ttl(const struct sk_buff *skb,
return ip->ttl == f_ttl;
}
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)
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)
{
const unsigned char *optp = NULL, *_optp = NULL;
unsigned int optsize = 0, check_WSS = 0;
int fmatch = FMATCH_WRONG, fcount = 0;
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;
u16 window, totlen, mss = 0;
const struct tcphdr *tcp;
struct tcphdr _tcph;
bool df;
tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
if (!tcp)
return false;
if (!tcp->syn)
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);
}
list_for_each_entry_rcu(kf, &nf_osf_fingers[df], finger_entry) {
unsigned int check_WSS = 0;
int fmatch = FMATCH_WRONG;
int foptsize, optnum;
u16 mss = 0;
f = &kf->finger;
if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))
continue;
optp = _optp;
fmatch = FMATCH_WRONG;
if (totlen != f->ss || !nf_osf_ttl(skb, info, f->ttl))
continue;
if (totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))
return false;
/*
* Should not happen if userspace parser was written correctly.
*/
if (f->wss.wc >= OSF_WSS_MAX)
continue;
return false;
/* Check options */
@ -117,7 +80,7 @@ nf_osf_match(const struct sk_buff *skb, u_int8_t family,
if (foptsize > MAX_IPOPTLEN ||
optsize > MAX_IPOPTLEN ||
optsize != foptsize)
continue;
return false;
check_WSS = f->wss.wc;
@ -183,9 +146,61 @@ nf_osf_match(const struct sk_buff *skb, u_int8_t family,
}
}
if (fmatch != FMATCH_OK)
return fmatch == FMATCH_OK;
}
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;
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;
if (!tcp->syn)
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) {
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))
continue;
fmatch = FMATCH_OK;
fcount++;
if (info->flags & NF_OSF_LOG)