// SPDX-License-Identifier: GPL-2.0-only
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#include <net/ip.h>
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#include <net/tcp.h>
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#include <net/netfilter/nf_tables.h>
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#include <linux/netfilter/nfnetlink_osf.h>
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struct nft_osf {
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u8 dreg;
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u8 ttl;
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u32 flags;
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};
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static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
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[NFTA_OSF_DREG] = { .type = NLA_U32 },
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[NFTA_OSF_TTL] = { .type = NLA_U8 },
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[NFTA_OSF_FLAGS] = { .type = NLA_U32 },
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};
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static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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struct nft_osf *priv = nft_expr_priv(expr);
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u32 *dest = ®s->data[priv->dreg];
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struct sk_buff *skb = pkt->skb;
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char os_match[NFT_OSF_MAXGENRELEN + 1];
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const struct tcphdr *tcp;
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struct nf_osf_data data;
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struct tcphdr _tcph;
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if (pkt->tprot != IPPROTO_TCP) {
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regs->verdict.code = NFT_BREAK;
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return;
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}
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tcp = skb_header_pointer(skb, ip_hdrlen(skb),
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sizeof(struct tcphdr), &_tcph);
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if (!tcp) {
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regs->verdict.code = NFT_BREAK;
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return;
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}
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if (!tcp->syn) {
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regs->verdict.code = NFT_BREAK;
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return;
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}
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if (!nf_osf_find(skb, nf_osf_fingers, priv->ttl, &data)) {
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strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
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} else {
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if (priv->flags & NFT_OSF_F_VERSION)
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snprintf(os_match, NFT_OSF_MAXGENRELEN, "%s:%s",
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data.genre, data.version);
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else
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strlcpy(os_match, data.genre, NFT_OSF_MAXGENRELEN);
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strncpy((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
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}
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}
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static int nft_osf_init(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nlattr * const tb[])
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{
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struct nft_osf *priv = nft_expr_priv(expr);
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u32 flags;
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int err;
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u8 ttl;
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if (!tb[NFTA_OSF_DREG])
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return -EINVAL;
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if (tb[NFTA_OSF_TTL]) {
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ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
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if (ttl > 2)
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return -EINVAL;
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priv->ttl = ttl;
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}
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if (tb[NFTA_OSF_FLAGS]) {
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flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
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if (flags != NFT_OSF_F_VERSION)
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return -EINVAL;
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priv->flags = flags;
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}
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err = nft_parse_register_store(ctx, tb[NFTA_OSF_DREG], &priv->dreg,
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NULL, NFT_DATA_VALUE,
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NFT_OSF_MAXGENRELEN);
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if (err < 0)
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return err;
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return 0;
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}
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static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)
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{
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const struct nft_osf *priv = nft_expr_priv(expr);
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if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl))
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goto nla_put_failure;
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if (nla_put_be32(skb, NFTA_OSF_FLAGS, ntohl(priv->flags)))
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goto nla_put_failure;
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if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -1;
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}
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static int nft_osf_validate(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nft_data **data)
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{
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unsigned int hooks;
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switch (ctx->family) {
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case NFPROTO_IPV4:
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case NFPROTO_IPV6:
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case NFPROTO_INET:
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hooks = (1 << NF_INET_LOCAL_IN) |
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(1 << NF_INET_PRE_ROUTING) |
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(1 << NF_INET_FORWARD);
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break;
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default:
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return -EOPNOTSUPP;
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}
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return nft_chain_validate_hooks(ctx->chain, hooks);
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}
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static struct nft_expr_type nft_osf_type;
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static const struct nft_expr_ops nft_osf_op = {
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.eval = nft_osf_eval,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_osf)),
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.init = nft_osf_init,
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.dump = nft_osf_dump,
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.type = &nft_osf_type,
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.validate = nft_osf_validate,
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};
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static struct nft_expr_type nft_osf_type __read_mostly = {
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.ops = &nft_osf_op,
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.name = "osf",
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.owner = THIS_MODULE,
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.policy = nft_osf_policy,
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.maxattr = NFTA_OSF_MAX,
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};
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static int __init nft_osf_module_init(void)
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{
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return nft_register_expr(&nft_osf_type);
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}
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static void __exit nft_osf_module_exit(void)
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{
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return nft_unregister_expr(&nft_osf_type);
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}
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module_init(nft_osf_module_init);
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module_exit(nft_osf_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
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MODULE_ALIAS_NFT_EXPR("osf");
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MODULE_DESCRIPTION("nftables passive OS fingerprint support");
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