diff options
Diffstat (limited to 'net/netfilter/nft_osf.c')
| -rw-r--r-- | net/netfilter/nft_osf.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/net/netfilter/nft_osf.c b/net/netfilter/nft_osf.c new file mode 100644 index 000000000..adacf95b6 --- /dev/null +++ b/net/netfilter/nft_osf.c @@ -0,0 +1,194 @@ +// 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 { + u8 dreg; + 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 + strscpy(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; + } + + err = nft_parse_register_store(ctx, tb[NFTA_OSF_DREG], &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_u32(skb, NFTA_OSF_FLAGS, ntohl((__force __be32)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) +{ + unsigned int hooks; + + switch (ctx->family) { + case NFPROTO_IPV4: + case NFPROTO_IPV6: + case NFPROTO_INET: + hooks = (1 << NF_INET_LOCAL_IN) | + (1 << NF_INET_PRE_ROUTING) | + (1 << NF_INET_FORWARD); + break; + default: + return -EOPNOTSUPP; + } + + return nft_chain_validate_hooks(ctx->chain, hooks); +} + +static bool nft_osf_reduce(struct nft_regs_track *track, + const struct nft_expr *expr) +{ + struct nft_osf *priv = nft_expr_priv(expr); + struct nft_osf *osf; + + if (!nft_reg_track_cmp(track, expr, priv->dreg)) { + nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN); + return false; + } + + osf = nft_expr_priv(track->regs[priv->dreg].selector); + if (priv->flags != osf->flags || + priv->ttl != osf->ttl) { + nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN); + return false; + } + + if (!track->regs[priv->dreg].bitwise) + return true; + + return false; +} + +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, + .reduce = nft_osf_reduce, +}; + +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"); |