| // SPDX-License-Identifier: GPL-2.0-only |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| #include <linux/module.h> |
| #include <linux/kernel.h> |
| |
| #include <linux/capability.h> |
| #include <linux/if.h> |
| #include <linux/inetdevice.h> |
| #include <linux/ip.h> |
| #include <linux/list.h> |
| #include <linux/rculist.h> |
| #include <linux/skbuff.h> |
| #include <linux/slab.h> |
| #include <linux/tcp.h> |
| |
| #include <net/ip.h> |
| #include <net/tcp.h> |
| |
| #include <linux/netfilter/nfnetlink.h> |
| #include <linux/netfilter/x_tables.h> |
| #include <net/netfilter/nf_log.h> |
| #include <linux/netfilter/nfnetlink_osf.h> |
| |
| /* |
| * Indexed by dont-fragment bit. |
| * It is the only constant value in the fingerprint. |
| */ |
| struct list_head nf_osf_fingers[2]; |
| EXPORT_SYMBOL_GPL(nf_osf_fingers); |
| |
| static inline int nf_osf_ttl(const struct sk_buff *skb, |
| int ttl_check, unsigned char f_ttl) |
| { |
| struct in_device *in_dev = __in_dev_get_rcu(skb->dev); |
| const struct iphdr *ip = ip_hdr(skb); |
| const struct in_ifaddr *ifa; |
| int ret = 0; |
| |
| if (ttl_check == NF_OSF_TTL_TRUE) |
| return ip->ttl == f_ttl; |
| if (ttl_check == NF_OSF_TTL_NOCHECK) |
| return 1; |
| else if (ip->ttl <= f_ttl) |
| return 1; |
| |
| in_dev_for_each_ifa_rcu(ifa, in_dev) { |
| if (inet_ifa_match(ip->saddr, ifa)) { |
| ret = (ip->ttl == f_ttl); |
| break; |
| } |
| } |
| |
| return ret; |
| } |
| |
| struct nf_osf_hdr_ctx { |
| bool df; |
| u16 window; |
| u16 totlen; |
| const unsigned char *optp; |
| unsigned int optsize; |
| }; |
| |
| static bool nf_osf_match_one(const struct sk_buff *skb, |
| const struct nf_osf_user_finger *f, |
| int ttl_check, |
| struct nf_osf_hdr_ctx *ctx) |
| { |
| const __u8 *optpinit = ctx->optp; |
| unsigned int check_WSS = 0; |
| int fmatch = FMATCH_WRONG; |
| int foptsize, optnum; |
| u16 mss = 0; |
| |
| if (ctx->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) |
| return false; |
| |
| /* Check options */ |
| |
| foptsize = 0; |
| for (optnum = 0; optnum < f->opt_num; ++optnum) |
| foptsize += f->opt[optnum].length; |
| |
| if (foptsize > MAX_IPOPTLEN || |
| ctx->optsize > MAX_IPOPTLEN || |
| ctx->optsize != foptsize) |
| return false; |
| |
| check_WSS = f->wss.wc; |
| |
| for (optnum = 0; optnum < f->opt_num; ++optnum) { |
| if (f->opt[optnum].kind == *ctx->optp) { |
| __u32 len = f->opt[optnum].length; |
| const __u8 *optend = ctx->optp + len; |
| |
| fmatch = FMATCH_OK; |
| |
| switch (*ctx->optp) { |
| case OSFOPT_MSS: |
| mss = ctx->optp[3]; |
| mss <<= 8; |
| mss |= ctx->optp[2]; |
| |
| mss = ntohs((__force __be16)mss); |
| break; |
| case OSFOPT_TS: |
| break; |
| } |
| |
| ctx->optp = optend; |
| } else |
| fmatch = FMATCH_OPT_WRONG; |
| |
| if (fmatch != FMATCH_OK) |
| break; |
| } |
| |
| if (fmatch != FMATCH_OPT_WRONG) { |
| fmatch = FMATCH_WRONG; |
| |
| switch (check_WSS) { |
| case OSF_WSS_PLAIN: |
| if (f->wss.val == 0 || ctx->window == f->wss.val) |
| fmatch = FMATCH_OK; |
| break; |
| case OSF_WSS_MSS: |
| /* |
| * Some smart modems decrease mangle MSS to |
| * SMART_MSS_2, so we check standard, decreased |
| * and the one provided in the fingerprint MSS |
| * values. |
| */ |
| #define SMART_MSS_1 1460 |
| #define SMART_MSS_2 1448 |
| if (ctx->window == f->wss.val * mss || |
| ctx->window == f->wss.val * SMART_MSS_1 || |
| ctx->window == f->wss.val * SMART_MSS_2) |
| fmatch = FMATCH_OK; |
| break; |
| case OSF_WSS_MTU: |
| if (ctx->window == f->wss.val * (mss + 40) || |
| ctx->window == f->wss.val * (SMART_MSS_1 + 40) || |
| ctx->window == f->wss.val * (SMART_MSS_2 + 40)) |
| fmatch = FMATCH_OK; |
| break; |
| case OSF_WSS_MODULO: |
| if ((ctx->window % f->wss.val) == 0) |
| fmatch = FMATCH_OK; |
| break; |
| } |
| } |
| |
| if (fmatch != FMATCH_OK) |
| ctx->optp = optpinit; |
| |
| return fmatch == FMATCH_OK; |
| } |
| |
| static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx, |
| const struct sk_buff *skb, |
| const struct iphdr *ip, |
| unsigned char *opts, |
| struct tcphdr *_tcph) |
| { |
| const struct tcphdr *tcp; |
| |
| tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), _tcph); |
| if (!tcp) |
| return NULL; |
| |
| if (!tcp->syn) |
| return NULL; |
| |
| ctx->totlen = ntohs(ip->tot_len); |
| ctx->df = ntohs(ip->frag_off) & IP_DF; |
| ctx->window = ntohs(tcp->window); |
| |
| if (tcp->doff * 4 > sizeof(struct tcphdr)) { |
| ctx->optsize = tcp->doff * 4 - sizeof(struct tcphdr); |
| |
| ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) + |
| sizeof(struct tcphdr), ctx->optsize, opts); |
| if (!ctx->optp) |
| return NULL; |
| } |
| |
| return tcp; |
| } |
| |
| 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 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; |
| struct nf_osf_hdr_ctx ctx; |
| const struct tcphdr *tcp; |
| struct tcphdr _tcph; |
| |
| memset(&ctx, 0, sizeof(ctx)); |
| |
| tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph); |
| if (!tcp) |
| return false; |
| |
| ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : 0; |
| |
| list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.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, &ctx)) |
| continue; |
| |
| fmatch = FMATCH_OK; |
| |
| fcount++; |
| |
| if (info->flags & NF_OSF_LOG) |
| nf_log_packet(net, family, hooknum, skb, |
| in, out, NULL, |
| "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n", |
| f->genre, f->version, f->subtype, |
| &ip->saddr, ntohs(tcp->source), |
| &ip->daddr, ntohs(tcp->dest), |
| f->ttl - ip->ttl); |
| |
| if ((info->flags & NF_OSF_LOG) && |
| info->loglevel == NF_OSF_LOGLEVEL_FIRST) |
| break; |
| } |
| |
| if (!fcount && (info->flags & NF_OSF_LOG)) |
| nf_log_packet(net, family, hooknum, skb, in, out, NULL, |
| "Remote OS is not known: %pI4:%u -> %pI4:%u\n", |
| &ip->saddr, ntohs(tcp->source), |
| &ip->daddr, ntohs(tcp->dest)); |
| |
| if (fcount) |
| fmatch = FMATCH_OK; |
| |
| return fmatch == FMATCH_OK; |
| } |
| EXPORT_SYMBOL_GPL(nf_osf_match); |
| |
| bool nf_osf_find(const struct sk_buff *skb, |
| const struct list_head *nf_osf_fingers, |
| const int ttl_check, struct nf_osf_data *data) |
| { |
| 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; |
| struct nf_osf_hdr_ctx ctx; |
| const struct tcphdr *tcp; |
| struct tcphdr _tcph; |
| bool found = false; |
| |
| memset(&ctx, 0, sizeof(ctx)); |
| |
| tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph); |
| if (!tcp) |
| return false; |
| |
| list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) { |
| f = &kf->finger; |
| if (!nf_osf_match_one(skb, f, ttl_check, &ctx)) |
| continue; |
| |
| data->genre = f->genre; |
| data->version = f->version; |
| found = true; |
| break; |
| } |
| |
| return found; |
| } |
| EXPORT_SYMBOL_GPL(nf_osf_find); |
| |
| static const struct nla_policy nfnl_osf_policy[OSF_ATTR_MAX + 1] = { |
| [OSF_ATTR_FINGER] = { .len = sizeof(struct nf_osf_user_finger) }, |
| }; |
| |
| static int nfnl_osf_add_callback(struct sk_buff *skb, |
| const struct nfnl_info *info, |
| const struct nlattr * const osf_attrs[]) |
| { |
| struct nf_osf_user_finger *f; |
| struct nf_osf_finger *kf = NULL, *sf; |
| int err = 0; |
| |
| if (!capable(CAP_NET_ADMIN)) |
| return -EPERM; |
| |
| if (!osf_attrs[OSF_ATTR_FINGER]) |
| return -EINVAL; |
| |
| if (!(info->nlh->nlmsg_flags & NLM_F_CREATE)) |
| return -EINVAL; |
| |
| f = nla_data(osf_attrs[OSF_ATTR_FINGER]); |
| |
| kf = kmalloc(sizeof(struct nf_osf_finger), GFP_KERNEL); |
| if (!kf) |
| return -ENOMEM; |
| |
| memcpy(&kf->finger, f, sizeof(struct nf_osf_user_finger)); |
| |
| list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) { |
| if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger))) |
| continue; |
| |
| kfree(kf); |
| kf = NULL; |
| |
| if (info->nlh->nlmsg_flags & NLM_F_EXCL) |
| err = -EEXIST; |
| break; |
| } |
| |
| /* |
| * We are protected by nfnl mutex. |
| */ |
| if (kf) |
| list_add_tail_rcu(&kf->finger_entry, &nf_osf_fingers[!!f->df]); |
| |
| return err; |
| } |
| |
| static int nfnl_osf_remove_callback(struct sk_buff *skb, |
| const struct nfnl_info *info, |
| const struct nlattr * const osf_attrs[]) |
| { |
| struct nf_osf_user_finger *f; |
| struct nf_osf_finger *sf; |
| int err = -ENOENT; |
| |
| if (!capable(CAP_NET_ADMIN)) |
| return -EPERM; |
| |
| if (!osf_attrs[OSF_ATTR_FINGER]) |
| return -EINVAL; |
| |
| f = nla_data(osf_attrs[OSF_ATTR_FINGER]); |
| |
| list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) { |
| if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger))) |
| continue; |
| |
| /* |
| * We are protected by nfnl mutex. |
| */ |
| list_del_rcu(&sf->finger_entry); |
| kfree_rcu(sf, rcu_head); |
| |
| err = 0; |
| break; |
| } |
| |
| return err; |
| } |
| |
| static const struct nfnl_callback nfnl_osf_callbacks[OSF_MSG_MAX] = { |
| [OSF_MSG_ADD] = { |
| .call = nfnl_osf_add_callback, |
| .type = NFNL_CB_MUTEX, |
| .attr_count = OSF_ATTR_MAX, |
| .policy = nfnl_osf_policy, |
| }, |
| [OSF_MSG_REMOVE] = { |
| .call = nfnl_osf_remove_callback, |
| .type = NFNL_CB_MUTEX, |
| .attr_count = OSF_ATTR_MAX, |
| .policy = nfnl_osf_policy, |
| }, |
| }; |
| |
| static const struct nfnetlink_subsystem nfnl_osf_subsys = { |
| .name = "osf", |
| .subsys_id = NFNL_SUBSYS_OSF, |
| .cb_count = OSF_MSG_MAX, |
| .cb = nfnl_osf_callbacks, |
| }; |
| |
| static int __init nfnl_osf_init(void) |
| { |
| int err = -EINVAL; |
| int i; |
| |
| for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i) |
| INIT_LIST_HEAD(&nf_osf_fingers[i]); |
| |
| err = nfnetlink_subsys_register(&nfnl_osf_subsys); |
| if (err < 0) { |
| pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err); |
| goto err_out_exit; |
| } |
| return 0; |
| |
| err_out_exit: |
| return err; |
| } |
| |
| static void __exit nfnl_osf_fini(void) |
| { |
| struct nf_osf_finger *f; |
| int i; |
| |
| nfnetlink_subsys_unregister(&nfnl_osf_subsys); |
| |
| rcu_read_lock(); |
| for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i) { |
| list_for_each_entry_rcu(f, &nf_osf_fingers[i], finger_entry) { |
| list_del_rcu(&f->finger_entry); |
| kfree_rcu(f, rcu_head); |
| } |
| } |
| rcu_read_unlock(); |
| |
| rcu_barrier(); |
| } |
| |
| module_init(nfnl_osf_init); |
| module_exit(nfnl_osf_fini); |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF); |