/*-
 * SPDX-License-Identifier: ISC
 *
 * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 *      $OpenBSD: pf_osfp.c,v 1.14 2008/06/12 18:17:01 henning Exp $
 */

#include <sys/cdefs.h>
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/socket.h>

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>

#include <net/if.h>
#include <net/vnet.h>
#include <net/pfvar.h>

#ifdef INET6
#include <netinet/ip6.h>
#endif

static MALLOC_DEFINE(M_PFOSFP, "pf_osfp", "pf(4) operating system fingerprints");

SLIST_HEAD(pf_osfp_list, pf_os_fingerprint);
VNET_DEFINE_STATIC(struct pf_osfp_list, pf_osfp_list) =
        SLIST_HEAD_INITIALIZER();
#define V_pf_osfp_list                  VNET(pf_osfp_list)

static struct pf_osfp_enlist    *pf_osfp_fingerprint_hdr(const struct ip *,
                                    const struct ip6_hdr *,
                                    const struct tcphdr *);
static struct pf_os_fingerprint *pf_osfp_find(struct pf_osfp_list *,
                                    struct pf_os_fingerprint *, u_int8_t);
static struct pf_os_fingerprint *pf_osfp_find_exact(struct pf_osfp_list *,
                                    struct pf_os_fingerprint *);
static void                      pf_osfp_insert(struct pf_osfp_list *,
                                    struct pf_os_fingerprint *);
#ifdef PFDEBUG
static struct pf_os_fingerprint *pf_osfp_validate(void);
#endif

/*
 * Passively fingerprint the OS of the host (IPv4 TCP SYN packets only)
 * Returns the list of possible OSes.
 */
struct pf_osfp_enlist *
pf_osfp_fingerprint(struct pf_pdesc *pd, const struct tcphdr *tcp)
{
        struct ip       *ip = NULL;
        struct ip6_hdr  *ip6 = NULL;
        char             hdr[60];

        if (pd->proto != IPPROTO_TCP || (tcp->th_off << 2) < sizeof(*tcp))
                return (NULL);

        switch (pd->af) {
        case AF_INET:
                ip = mtod(pd->m, struct ip *);
                ip6 = (struct ip6_hdr *)NULL;
                break;
        case AF_INET6:
                ip6 = mtod(pd->m, struct ip6_hdr *);
                break;
        }
        if (!pf_pull_hdr(pd->m, pd->off, hdr, tcp->th_off << 2, NULL,
            pd->af)) return (NULL);

        return (pf_osfp_fingerprint_hdr(ip, ip6, (struct tcphdr *)hdr));
}

static struct pf_osfp_enlist *
pf_osfp_fingerprint_hdr(const struct ip *ip, const struct ip6_hdr *ip6, const struct tcphdr *tcp)
{
        struct pf_os_fingerprint fp, *fpresult;
        int cnt, optlen = 0;
        const u_int8_t *optp;
#ifdef INET6
        char srcname[INET6_ADDRSTRLEN];
#else
        char srcname[INET_ADDRSTRLEN];
#endif

        if ((tcp_get_flags(tcp) & (TH_SYN|TH_ACK)) != TH_SYN)
                return (NULL);
        if (ip) {
                if ((ip->ip_off & htons(IP_OFFMASK)) != 0)
                        return (NULL);
        }

        memset(&fp, 0, sizeof(fp));

        if (ip) {
                fp.fp_psize = ntohs(ip->ip_len);
                fp.fp_ttl = ip->ip_ttl;
                if (ip->ip_off & htons(IP_DF))
                        fp.fp_flags |= PF_OSFP_DF;
                inet_ntoa_r(ip->ip_src, srcname);
        }
#ifdef INET6
        else if (ip6) {
                /* jumbo payload? */
                fp.fp_psize = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen);
                fp.fp_ttl = ip6->ip6_hlim;
                fp.fp_flags |= PF_OSFP_DF;
                fp.fp_flags |= PF_OSFP_INET6;
                ip6_sprintf(srcname, (const struct in6_addr *)&ip6->ip6_src);
        }
#endif
        else
                return (NULL);
        fp.fp_wsize = ntohs(tcp->th_win);

        cnt = (tcp->th_off << 2) - sizeof(*tcp);
        optp = (const u_int8_t *)((const char *)tcp + sizeof(*tcp));
        for (; cnt > 0; cnt -= optlen, optp += optlen) {
                if (*optp == TCPOPT_EOL)
                        break;

                fp.fp_optcnt++;
                if (*optp == TCPOPT_NOP) {
                        fp.fp_tcpopts = (fp.fp_tcpopts << PF_OSFP_TCPOPT_BITS) |
                            PF_OSFP_TCPOPT_NOP;
                        optlen = 1;
                } else {
                        if (cnt < 2)
                                return (NULL);
                        optlen = optp[1];
                        if (optlen > cnt || optlen < 2)
                                return (NULL);
                        switch (*optp) {
                        case TCPOPT_MAXSEG:
                                if (optlen >= TCPOLEN_MAXSEG)
                                        memcpy(&fp.fp_mss, &optp[2],
                                            sizeof(fp.fp_mss));
                                fp.fp_tcpopts = (fp.fp_tcpopts <<
                                    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_MSS;
                                fp.fp_mss = ntohs(fp.fp_mss);
                                break;
                        case TCPOPT_WINDOW:
                                if (optlen >= TCPOLEN_WINDOW)
                                        memcpy(&fp.fp_wscale, &optp[2],
                                            sizeof(fp.fp_wscale));
                                fp.fp_wscale = ntohs(fp.fp_wscale);
                                fp.fp_tcpopts = (fp.fp_tcpopts <<
                                    PF_OSFP_TCPOPT_BITS) |
                                    PF_OSFP_TCPOPT_WSCALE;
                                break;
                        case TCPOPT_SACK_PERMITTED:
                                fp.fp_tcpopts = (fp.fp_tcpopts <<
                                    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_SACK;
                                break;
                        case TCPOPT_TIMESTAMP:
                                if (optlen >= TCPOLEN_TIMESTAMP) {
                                        u_int32_t ts;
                                        memcpy(&ts, &optp[2], sizeof(ts));
                                        if (ts == 0)
                                                fp.fp_flags |= PF_OSFP_TS0;
                                }
                                fp.fp_tcpopts = (fp.fp_tcpopts <<
                                    PF_OSFP_TCPOPT_BITS) | PF_OSFP_TCPOPT_TS;
                                break;
                        default:
                                return (NULL);
                        }
                }
                optlen = MAX(optlen, 1);        /* paranoia */
        }

        DPFPRINTF(PF_DEBUG_NOISY, "fingerprinted %s:%d  %d:%d:%d:%d:%llx (%d) "
            "(TS=%s,M=%s%d,W=%s%d)",
            srcname, ntohs(tcp->th_sport),
            fp.fp_wsize, fp.fp_ttl, (fp.fp_flags & PF_OSFP_DF) != 0,
            fp.fp_psize, (long long int)fp.fp_tcpopts, fp.fp_optcnt,
            (fp.fp_flags & PF_OSFP_TS0) ? "0" : "",
            (fp.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
            (fp.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
            fp.fp_mss,
            (fp.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
            (fp.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
            fp.fp_wscale);

        if ((fpresult = pf_osfp_find(&V_pf_osfp_list, &fp,
            PF_OSFP_MAXTTL_OFFSET)))
                return (&fpresult->fp_oses);
        return (NULL);
}

/* Match a fingerprint ID against a list of OSes */
int
pf_osfp_match(struct pf_osfp_enlist *list, pf_osfp_t os)
{
        struct pf_osfp_entry *entry;
        int os_class, os_version, os_subtype;
        int en_class, en_version, en_subtype;

        if (os == PF_OSFP_ANY)
                return (1);
        if (list == NULL) {
                DPFPRINTF(PF_DEBUG_NOISY, "osfp no match against %x", os);
                return (os == PF_OSFP_UNKNOWN);
        }
        PF_OSFP_UNPACK(os, os_class, os_version, os_subtype);
        SLIST_FOREACH(entry, list, fp_entry) {
                PF_OSFP_UNPACK(entry->fp_os, en_class, en_version, en_subtype);
                if ((os_class == PF_OSFP_ANY || en_class == os_class) &&
                    (os_version == PF_OSFP_ANY || en_version == os_version) &&
                    (os_subtype == PF_OSFP_ANY || en_subtype == os_subtype)) {
                        DPFPRINTF(PF_DEBUG_NOISY, "osfp matched %s %s %s  %x==%x",
                            entry->fp_class_nm, entry->fp_version_nm,
                            entry->fp_subtype_nm, os, entry->fp_os);
                        return (1);
                }
        }
        DPFPRINTF(PF_DEBUG_NOISY, "fingerprint 0x%x didn't match", os);
        return (0);
}

/* Flush the fingerprint list */
void
pf_osfp_flush(void)
{
        struct pf_os_fingerprint *fp;
        struct pf_osfp_entry *entry;

        while ((fp = SLIST_FIRST(&V_pf_osfp_list))) {
                SLIST_REMOVE_HEAD(&V_pf_osfp_list, fp_next);
                while ((entry = SLIST_FIRST(&fp->fp_oses))) {
                        SLIST_REMOVE_HEAD(&fp->fp_oses, fp_entry);
                        free(entry, M_PFOSFP);
                }
                free(fp, M_PFOSFP);
        }
}

/* Add a fingerprint */
int
pf_osfp_add(struct pf_osfp_ioctl *fpioc)
{
        struct pf_os_fingerprint *fp, fpadd;
        struct pf_osfp_entry *entry;

        PF_RULES_WASSERT();

        memset(&fpadd, 0, sizeof(fpadd));
        fpadd.fp_tcpopts = fpioc->fp_tcpopts;
        fpadd.fp_wsize = fpioc->fp_wsize;
        fpadd.fp_psize = fpioc->fp_psize;
        fpadd.fp_mss = fpioc->fp_mss;
        fpadd.fp_flags = fpioc->fp_flags;
        fpadd.fp_optcnt = fpioc->fp_optcnt;
        fpadd.fp_wscale = fpioc->fp_wscale;
        fpadd.fp_ttl = fpioc->fp_ttl;

#if 0   /* XXX RYAN wants to fix logging */
        DPFPRINTF(PF_DEBUG_NOISY, "adding osfp %s %s %s ="
            " %s%d:%d:%d:%s%d:0x%llx %d (TS=%s,M=%s%d,W=%s%d) %x",
            fpioc->fp_os.fp_class_nm, fpioc->fp_os.fp_version_nm,
            fpioc->fp_os.fp_subtype_nm,
            (fpadd.fp_flags & PF_OSFP_WSIZE_MOD) ? "%" :
            (fpadd.fp_flags & PF_OSFP_WSIZE_MSS) ? "S" :
            (fpadd.fp_flags & PF_OSFP_WSIZE_MTU) ? "T" :
            (fpadd.fp_flags & PF_OSFP_WSIZE_DC) ? "*" : "",
            fpadd.fp_wsize,
            fpadd.fp_ttl,
            (fpadd.fp_flags & PF_OSFP_DF) ? 1 : 0,
            (fpadd.fp_flags & PF_OSFP_PSIZE_MOD) ? "%" :
            (fpadd.fp_flags & PF_OSFP_PSIZE_DC) ? "*" : "",
            fpadd.fp_psize,
            (long long int)fpadd.fp_tcpopts, fpadd.fp_optcnt,
            (fpadd.fp_flags & PF_OSFP_TS0) ? "0" : "",
            (fpadd.fp_flags & PF_OSFP_MSS_MOD) ? "%" :
            (fpadd.fp_flags & PF_OSFP_MSS_DC) ? "*" : "",
            fpadd.fp_mss,
            (fpadd.fp_flags & PF_OSFP_WSCALE_MOD) ? "%" :
            (fpadd.fp_flags & PF_OSFP_WSCALE_DC) ? "*" : "",
            fpadd.fp_wscale,
            fpioc->fp_os.fp_os);
#endif

        if ((fp = pf_osfp_find_exact(&V_pf_osfp_list, &fpadd))) {
                 SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
                        if (PF_OSFP_ENTRY_EQ(entry, &fpioc->fp_os))
                                return (EEXIST);
                }
                if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
                    == NULL)
                        return (ENOMEM);
        } else {
                if ((fp = malloc(sizeof(*fp), M_PFOSFP, M_ZERO | M_NOWAIT))
                    == NULL)
                        return (ENOMEM);
                fp->fp_tcpopts = fpioc->fp_tcpopts;
                fp->fp_wsize = fpioc->fp_wsize;
                fp->fp_psize = fpioc->fp_psize;
                fp->fp_mss = fpioc->fp_mss;
                fp->fp_flags = fpioc->fp_flags;
                fp->fp_optcnt = fpioc->fp_optcnt;
                fp->fp_wscale = fpioc->fp_wscale;
                fp->fp_ttl = fpioc->fp_ttl;
                SLIST_INIT(&fp->fp_oses);
                if ((entry = malloc(sizeof(*entry), M_PFOSFP, M_NOWAIT))
                    == NULL) {
                        free(fp, M_PFOSFP);
                        return (ENOMEM);
                }
                pf_osfp_insert(&V_pf_osfp_list, fp);
        }
        memcpy(entry, &fpioc->fp_os, sizeof(*entry));

        /* Make sure the strings are NUL terminated */
        entry->fp_class_nm[sizeof(entry->fp_class_nm)-1] = '\0';
        entry->fp_version_nm[sizeof(entry->fp_version_nm)-1] = '\0';
        entry->fp_subtype_nm[sizeof(entry->fp_subtype_nm)-1] = '\0';

        SLIST_INSERT_HEAD(&fp->fp_oses, entry, fp_entry);

#ifdef PFDEBUG
        if ((fp = pf_osfp_validate()))
                printf("Invalid fingerprint list\n");
#endif /* PFDEBUG */
        return (0);
}

/* Find a fingerprint in the list */
static struct pf_os_fingerprint *
pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find,
    u_int8_t ttldiff)
{
        struct pf_os_fingerprint *f;

#define MATCH_INT(_MOD, _DC, _field)                                    \
        if ((f->fp_flags & _DC) == 0) {                                 \
                if ((f->fp_flags & _MOD) == 0) {                        \
                        if (f->_field != find->_field)                  \
                                continue;                               \
                } else {                                                \
                        if (f->_field == 0 || find->_field % f->_field) \
                                continue;                               \
                }                                                       \
        }

        SLIST_FOREACH(f, list, fp_next) {
                if (f->fp_tcpopts != find->fp_tcpopts ||
                    f->fp_optcnt != find->fp_optcnt ||
                    f->fp_ttl < find->fp_ttl ||
                    f->fp_ttl - find->fp_ttl > ttldiff ||
                    (f->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)) !=
                    (find->fp_flags & (PF_OSFP_DF|PF_OSFP_TS0)))
                        continue;

                MATCH_INT(PF_OSFP_PSIZE_MOD, PF_OSFP_PSIZE_DC, fp_psize)
                MATCH_INT(PF_OSFP_MSS_MOD, PF_OSFP_MSS_DC, fp_mss)
                MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale)
                if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) {
                        if (f->fp_flags & PF_OSFP_WSIZE_MSS) {
                                if (find->fp_mss == 0)
                                        continue;

/*
 * Some "smart" NAT devices and DSL routers will tweak the MSS size and
 * will set it to whatever is suitable for the link type.
 */
#define SMART_MSS       1460
                                if ((find->fp_wsize % find->fp_mss ||
                                    find->fp_wsize / find->fp_mss !=
                                    f->fp_wsize) &&
                                    (find->fp_wsize % SMART_MSS ||
                                    find->fp_wsize / SMART_MSS !=
                                    f->fp_wsize))
                                        continue;
                        } else if (f->fp_flags & PF_OSFP_WSIZE_MTU) {
                                if (find->fp_mss == 0)
                                        continue;

#define MTUOFF          (sizeof(struct ip) + sizeof(struct tcphdr))
#define SMART_MTU       (SMART_MSS + MTUOFF)
                                if ((find->fp_wsize % (find->fp_mss + MTUOFF) ||
                                    find->fp_wsize / (find->fp_mss + MTUOFF) !=
                                    f->fp_wsize) &&
                                    (find->fp_wsize % SMART_MTU ||
                                    find->fp_wsize / SMART_MTU !=
                                    f->fp_wsize))
                                        continue;
                        } else if (f->fp_flags & PF_OSFP_WSIZE_MOD) {
                                if (f->fp_wsize == 0 || find->fp_wsize %
                                    f->fp_wsize)
                                        continue;
                        } else {
                                if (f->fp_wsize != find->fp_wsize)
                                        continue;
                        }
                }
                return (f);
        }

        return (NULL);
}

/* Find an exact fingerprint in the list */
static struct pf_os_fingerprint *
pf_osfp_find_exact(struct pf_osfp_list *list, struct pf_os_fingerprint *find)
{
        struct pf_os_fingerprint *f;

        SLIST_FOREACH(f, list, fp_next) {
                if (f->fp_tcpopts == find->fp_tcpopts &&
                    f->fp_wsize == find->fp_wsize &&
                    f->fp_psize == find->fp_psize &&
                    f->fp_mss == find->fp_mss &&
                    f->fp_flags == find->fp_flags &&
                    f->fp_optcnt == find->fp_optcnt &&
                    f->fp_wscale == find->fp_wscale &&
                    f->fp_ttl == find->fp_ttl)
                        return (f);
        }

        return (NULL);
}

/* Insert a fingerprint into the list */
static void
pf_osfp_insert(struct pf_osfp_list *list, struct pf_os_fingerprint *ins)
{
        struct pf_os_fingerprint *f, *prev = NULL;

        /* XXX need to go semi tree based.  can key on tcp options */

        SLIST_FOREACH(f, list, fp_next)
                prev = f;
        if (prev)
                SLIST_INSERT_AFTER(prev, ins, fp_next);
        else
                SLIST_INSERT_HEAD(list, ins, fp_next);
}

/* Fill a fingerprint by its number (from an ioctl) */
int
pf_osfp_get(struct pf_osfp_ioctl *fpioc)
{
        struct pf_os_fingerprint *fp;
        struct pf_osfp_entry *entry;
        int num = fpioc->fp_getnum;
        int i = 0;

        memset(fpioc, 0, sizeof(*fpioc));
        SLIST_FOREACH(fp, &V_pf_osfp_list, fp_next) {
                SLIST_FOREACH(entry, &fp->fp_oses, fp_entry) {
                        if (i++ == num) {
                                fpioc->fp_mss = fp->fp_mss;
                                fpioc->fp_wsize = fp->fp_wsize;
                                fpioc->fp_flags = fp->fp_flags;
                                fpioc->fp_psize = fp->fp_psize;
                                fpioc->fp_ttl = fp->fp_ttl;
                                fpioc->fp_wscale = fp->fp_wscale;
                                fpioc->fp_getnum = num;
                                memcpy(&fpioc->fp_os, entry,
                                    sizeof(fpioc->fp_os));
                                return (0);
                        }
                }
        }

        return (EBUSY);
}

#ifdef PFDEBUG
/* Validate that each signature is reachable */
static struct pf_os_fingerprint *
pf_osfp_validate(void)
{
        struct pf_os_fingerprint *f, *f2, find;

        SLIST_FOREACH(f, &V_pf_osfp_list, fp_next) {
                memcpy(&find, f, sizeof(find));

                /* We do a few MSS/th_win percolations to make things unique */
                if (find.fp_mss == 0)
                        find.fp_mss = 128;
                if (f->fp_flags & PF_OSFP_WSIZE_MSS)
                        find.fp_wsize *= find.fp_mss;
                else if (f->fp_flags & PF_OSFP_WSIZE_MTU)
                        find.fp_wsize *= (find.fp_mss + 40);
                else if (f->fp_flags & PF_OSFP_WSIZE_MOD)
                        find.fp_wsize *= 2;
                if (f != (f2 = pf_osfp_find(&V_pf_osfp_list, &find, 0))) {
                        if (f2)
                                printf("Found \"%s %s %s\" instead of "
                                    "\"%s %s %s\"\n",
                                    SLIST_FIRST(&f2->fp_oses)->fp_class_nm,
                                    SLIST_FIRST(&f2->fp_oses)->fp_version_nm,
                                    SLIST_FIRST(&f2->fp_oses)->fp_subtype_nm,
                                    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
                                    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
                                    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
                        else
                                printf("Couldn't find \"%s %s %s\"\n",
                                    SLIST_FIRST(&f->fp_oses)->fp_class_nm,
                                    SLIST_FIRST(&f->fp_oses)->fp_version_nm,
                                    SLIST_FIRST(&f->fp_oses)->fp_subtype_nm);
                        return (f);
                }
        }
        return (NULL);
}
#endif /* PFDEBUG */