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@netfilter.org>hifive-unleashed-5.1
Pablo Neira Ayuso
parent
06ff4aa252
commit
31a9c29210
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@ -51,18 +51,25 @@ static inline int nf_osf_ttl(const struct sk_buff *skb,
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return ip->ttl == f_ttl;
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}
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struct nf_osf_hdr_ctx {
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bool df;
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u16 window;
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u16 totlen;
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const unsigned char *optp;
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unsigned int optsize;
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};
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static bool nf_osf_match_one(const struct sk_buff *skb,
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const struct nf_osf_user_finger *f,
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int ttl_check, u16 totlen, u16 window,
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const unsigned char *optp,
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unsigned int optsize)
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int ttl_check,
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struct nf_osf_hdr_ctx *ctx)
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{
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unsigned int check_WSS = 0;
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int fmatch = FMATCH_WRONG;
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int foptsize, optnum;
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u16 mss = 0;
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if (totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))
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if (ctx->totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))
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return false;
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/*
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@ -78,24 +85,24 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
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foptsize += f->opt[optnum].length;
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if (foptsize > MAX_IPOPTLEN ||
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optsize > MAX_IPOPTLEN ||
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optsize != foptsize)
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ctx->optsize > MAX_IPOPTLEN ||
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ctx->optsize != foptsize)
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return false;
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check_WSS = f->wss.wc;
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for (optnum = 0; optnum < f->opt_num; ++optnum) {
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if (f->opt[optnum].kind == (*optp)) {
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if (f->opt[optnum].kind == *ctx->optp) {
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__u32 len = f->opt[optnum].length;
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const __u8 *optend = optp + len;
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const __u8 *optend = ctx->optp + len;
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fmatch = FMATCH_OK;
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switch (*optp) {
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switch (*ctx->optp) {
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case OSFOPT_MSS:
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mss = optp[3];
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mss = ctx->optp[3];
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mss <<= 8;
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mss |= optp[2];
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mss |= ctx->optp[2];
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mss = ntohs((__force __be16)mss);
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break;
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@ -103,7 +110,7 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
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break;
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}
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optp = optend;
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ctx->optp = optend;
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} else
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fmatch = FMATCH_OPT_WRONG;
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@ -116,7 +123,7 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
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switch (check_WSS) {
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case OSF_WSS_PLAIN:
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if (f->wss.val == 0 || window == f->wss.val)
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if (f->wss.val == 0 || ctx->window == f->wss.val)
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fmatch = FMATCH_OK;
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break;
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case OSF_WSS_MSS:
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@ -128,19 +135,19 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
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*/
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#define SMART_MSS_1 1460
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#define SMART_MSS_2 1448
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if (window == f->wss.val * mss ||
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window == f->wss.val * SMART_MSS_1 ||
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window == f->wss.val * SMART_MSS_2)
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if (ctx->window == f->wss.val * mss ||
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ctx->window == f->wss.val * SMART_MSS_1 ||
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ctx->window == f->wss.val * SMART_MSS_2)
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fmatch = FMATCH_OK;
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break;
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case OSF_WSS_MTU:
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if (window == f->wss.val * (mss + 40) ||
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window == f->wss.val * (SMART_MSS_1 + 40) ||
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window == f->wss.val * (SMART_MSS_2 + 40))
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if (ctx->window == f->wss.val * (mss + 40) ||
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ctx->window == f->wss.val * (SMART_MSS_1 + 40) ||
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ctx->window == f->wss.val * (SMART_MSS_2 + 40))
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fmatch = FMATCH_OK;
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break;
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case OSF_WSS_MODULO:
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if ((window % f->wss.val) == 0)
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if ((ctx->window % f->wss.val) == 0)
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fmatch = FMATCH_OK;
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break;
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}
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@ -149,54 +156,66 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
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return fmatch == FMATCH_OK;
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}
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static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx,
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const struct sk_buff *skb,
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const struct iphdr *ip,
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unsigned char *opts)
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{
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const struct tcphdr *tcp;
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struct tcphdr _tcph;
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tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
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if (!tcp)
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return NULL;
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if (!tcp->syn)
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return NULL;
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ctx->totlen = ntohs(ip->tot_len);
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ctx->df = ntohs(ip->frag_off) & IP_DF;
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ctx->window = ntohs(tcp->window);
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if (tcp->doff * 4 > sizeof(struct tcphdr)) {
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ctx->optsize = tcp->doff * 4 - sizeof(struct tcphdr);
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ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) +
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sizeof(struct tcphdr), ctx->optsize, opts);
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}
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return tcp;
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}
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bool
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nf_osf_match(const struct sk_buff *skb, u_int8_t family,
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int hooknum, struct net_device *in, struct net_device *out,
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const struct nf_osf_info *info, struct net *net,
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const struct list_head *nf_osf_fingers)
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{
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const unsigned char *optp = NULL, *_optp = NULL;
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const struct iphdr *ip = ip_hdr(skb);
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const struct nf_osf_user_finger *f;
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unsigned char opts[MAX_IPOPTLEN];
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const struct nf_osf_finger *kf;
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int fcount = 0, ttl_check;
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int fmatch = FMATCH_WRONG;
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unsigned int optsize = 0;
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struct nf_osf_hdr_ctx ctx;
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const struct tcphdr *tcp;
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struct tcphdr _tcph;
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u16 window, totlen;
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bool df;
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tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
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memset(&ctx, 0, sizeof(ctx));
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tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts);
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if (!tcp)
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return false;
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if (!tcp->syn)
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return false;
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totlen = ntohs(ip->tot_len);
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df = ntohs(ip->frag_off) & IP_DF;
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window = ntohs(tcp->window);
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if (tcp->doff * 4 > sizeof(struct tcphdr)) {
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optsize = tcp->doff * 4 - sizeof(struct tcphdr);
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_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
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sizeof(struct tcphdr), optsize, opts);
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}
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ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : -1;
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list_for_each_entry_rcu(kf, &nf_osf_fingers[df], finger_entry) {
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list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
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f = &kf->finger;
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if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))
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continue;
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if (!nf_osf_match_one(skb, f,
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ttl_check, totlen, window, optp, optsize))
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if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
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continue;
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fmatch = FMATCH_OK;
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