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- // SPDX-License-Identifier: GPL-2.0-only
- #include <net/ip.h>
- #include <net/tcp.h>
- #include <net/netfilter/nf_tables.h>
- #include <linux/netfilter/nfnetlink_osf.h>
- struct nft_osf {
- enum nft_registers dreg:8;
- u8 ttl;
- u32 flags;
- };
- static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
- [NFTA_OSF_DREG] = { .type = NLA_U32 },
- [NFTA_OSF_TTL] = { .type = NLA_U8 },
- [NFTA_OSF_FLAGS] = { .type = NLA_U32 },
- };
- static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
- const struct nft_pktinfo *pkt)
- {
- struct nft_osf *priv = nft_expr_priv(expr);
- u32 *dest = ®s->data[priv->dreg];
- struct sk_buff *skb = pkt->skb;
- char os_match[NFT_OSF_MAXGENRELEN + 1];
- const struct tcphdr *tcp;
- struct nf_osf_data data;
- struct tcphdr _tcph;
- if (pkt->tprot != IPPROTO_TCP) {
- regs->verdict.code = NFT_BREAK;
- return;
- }
- tcp = skb_header_pointer(skb, ip_hdrlen(skb),
- sizeof(struct tcphdr), &_tcph);
- if (!tcp) {
- regs->verdict.code = NFT_BREAK;
- return;
- }
- if (!tcp->syn) {
- regs->verdict.code = NFT_BREAK;
- return;
- }
- if (!nf_osf_find(skb, nf_osf_fingers, priv->ttl, &data)) {
- strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
- } else {
- if (priv->flags & NFT_OSF_F_VERSION)
- snprintf(os_match, NFT_OSF_MAXGENRELEN, "%s:%s",
- data.genre, data.version);
- else
- strlcpy(os_match, data.genre, NFT_OSF_MAXGENRELEN);
- strncpy((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
- }
- }
- static int nft_osf_init(const struct nft_ctx *ctx,
- const struct nft_expr *expr,
- const struct nlattr * const tb[])
- {
- struct nft_osf *priv = nft_expr_priv(expr);
- u32 flags;
- int err;
- u8 ttl;
- if (!tb[NFTA_OSF_DREG])
- return -EINVAL;
- if (tb[NFTA_OSF_TTL]) {
- ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
- if (ttl > 2)
- return -EINVAL;
- priv->ttl = ttl;
- }
- if (tb[NFTA_OSF_FLAGS]) {
- flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
- if (flags != NFT_OSF_F_VERSION)
- return -EINVAL;
- priv->flags = flags;
- }
- priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
- err = nft_validate_register_store(ctx, priv->dreg, NULL,
- NFT_DATA_VALUE, NFT_OSF_MAXGENRELEN);
- if (err < 0)
- return err;
- return 0;
- }
- static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)
- {
- const struct nft_osf *priv = nft_expr_priv(expr);
- if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl))
- goto nla_put_failure;
- if (nla_put_be32(skb, NFTA_OSF_FLAGS, ntohl(priv->flags)))
- goto nla_put_failure;
- if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
- goto nla_put_failure;
- return 0;
- nla_put_failure:
- return -1;
- }
- static int nft_osf_validate(const struct nft_ctx *ctx,
- const struct nft_expr *expr,
- const struct nft_data **data)
- {
- return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
- (1 << NF_INET_PRE_ROUTING) |
- (1 << NF_INET_FORWARD));
- }
- static struct nft_expr_type nft_osf_type;
- static const struct nft_expr_ops nft_osf_op = {
- .eval = nft_osf_eval,
- .size = NFT_EXPR_SIZE(sizeof(struct nft_osf)),
- .init = nft_osf_init,
- .dump = nft_osf_dump,
- .type = &nft_osf_type,
- .validate = nft_osf_validate,
- };
- static struct nft_expr_type nft_osf_type __read_mostly = {
- .ops = &nft_osf_op,
- .name = "osf",
- .owner = THIS_MODULE,
- .policy = nft_osf_policy,
- .maxattr = NFTA_OSF_MAX,
- };
- static int __init nft_osf_module_init(void)
- {
- return nft_register_expr(&nft_osf_type);
- }
- static void __exit nft_osf_module_exit(void)
- {
- return nft_unregister_expr(&nft_osf_type);
- }
- module_init(nft_osf_module_init);
- module_exit(nft_osf_module_exit);
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
- MODULE_ALIAS_NFT_EXPR("osf");
- MODULE_DESCRIPTION("nftables passive OS fingerprint support");
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