/*      $NetBSD: accf_http.c,v 1.10 2020/03/16 21:20:11 pgoyette Exp $  */

/*-
 * Copyright (c) 2000 Paycounter, Inc.
 * Author: Alfred Perlstein <alfred@paycounter.com>, <alfred@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: accf_http.c,v 1.10 2020/03/16 21:20:11 pgoyette Exp $");

#define ACCEPT_FILTER_MOD

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/signalvar.h>
#include <sys/sysctl.h>
#include <sys/socket.h>
#include <sys/socketvar.h>

#include <netinet/accept_filter.h>

#include "ioconf.h"

MODULE(MODULE_CLASS_MISC, accf_httpready, NULL);

/* check for GET/HEAD */
static void sohashttpget(struct socket *so, void *arg, int events, int waitflag);
/* check for HTTP/1.0 or HTTP/1.1 */
static void soparsehttpvers(struct socket *so, void *arg, int events, int waitflag);
/* check for end of HTTP/1.x request */
static void soishttpconnected(struct socket *so, void *arg, int events, int waitflag);
/* strcmp on an mbuf chain */
static int mbufstrcmp(struct mbuf *m, struct mbuf *npkt, int offset, const char *cmp);
/* strncmp on an mbuf chain */
static int mbufstrncmp(struct mbuf *m, struct mbuf *npkt, int offset,
        int len, const char *cmp);
/* socketbuffer is full */
static int sbfull(struct sockbuf *sb);

static struct accept_filter accf_http_filter = {
        .accf_name = "httpready",
        .accf_callback = sohashttpget,
};

/*
 * Names of HTTP Accept filter sysctl objects
 */

#define ACCFCTL_PARSEVER        1       /* Parse HTTP version */

static int parse_http_version = 1;

void
accf_httpattach(int junk)
{

}

SYSCTL_SETUP(accf_sysctl_setup, "accf sysctl")
{

        sysctl_createv(clog, 0, NULL, NULL,
               CTLFLAG_PERMANENT,
               CTLTYPE_NODE, "inet", NULL,
               NULL, 0, NULL, 0,
               CTL_NET, PF_INET, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
               CTLFLAG_PERMANENT,
               CTLTYPE_NODE, "accf", NULL,
               NULL, 0, NULL, 0,
               CTL_NET, PF_INET, SO_ACCEPTFILTER, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
               CTLFLAG_PERMANENT,
               CTLTYPE_NODE, "http",
               SYSCTL_DESCR("HTTP accept filter"),
               NULL, 0, NULL, 0,
               CTL_NET, PF_INET, SO_ACCEPTFILTER, ACCF_HTTP, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
               CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
               CTLTYPE_INT, "parsehttpversion",
               SYSCTL_DESCR("Parse http version so that non "
                            "1.x requests work"),
               NULL, 0, &parse_http_version, 0,
               CTL_NET, PF_INET, SO_ACCEPTFILTER, ACCF_HTTP,
               ACCFCTL_PARSEVER, CTL_EOL);
}

static int
accf_httpready_modcmd(modcmd_t cmd, void *arg)
{
        int error;

        switch (cmd) {
        case MODULE_CMD_INIT:
                error = accept_filt_add(&accf_http_filter);
                return 0;

        case MODULE_CMD_FINI:
                error = accept_filt_del(&accf_http_filter);
                return error;

        default:
                return ENOTTY;
        }
}

#ifdef ACCF_HTTP_DEBUG
#define DPRINT(fmt, args...)                                            \
        do {                                                            \
                printf("%s:%d: " fmt "\n", __func__, __LINE__, ##args); \
        } while (0)
#else
#define DPRINT(fmt, args...)
#endif

static int
sbfull(struct sockbuf *sb)
{

        DPRINT("sbfull, cc(%ld) >= hiwat(%ld): %d, "
            "mbcnt(%ld) >= mbmax(%ld): %d",
            sb->sb_cc, sb->sb_hiwat, sb->sb_cc >= sb->sb_hiwat,
            sb->sb_mbcnt, sb->sb_mbmax, sb->sb_mbcnt >= sb->sb_mbmax);
        return (sb->sb_cc >= sb->sb_hiwat || sb->sb_mbcnt >= sb->sb_mbmax);
}

/*
 * start at mbuf m, (must provide npkt if exists)
 * starting at offset in m compare characters in mbuf chain for 'cmp'
 */
static int
mbufstrcmp(struct mbuf *m, struct mbuf *npkt, int offset, const char *cmp)
{
        struct mbuf *n;

        for (; m != NULL; m = n) {
                n = npkt;
                if (npkt)
                        npkt = npkt->m_nextpkt;
                for (; m; m = m->m_next) {
                        for (; offset < m->m_len; offset++, cmp++) {
                                if (*cmp == '\0')
                                        return (1);
                                else if (*cmp != *(mtod(m, char *) + offset))
                                        return (0);
                        }
                        if (*cmp == '\0')
                                return (1);
                        offset = 0;
                }
        }
        return (0);
}

/*
 * start at mbuf m, (must provide npkt if exists)
 * starting at offset in m compare characters in mbuf chain for 'cmp'
 * stop at 'max' characters
 */
static int
mbufstrncmp(struct mbuf *m, struct mbuf *npkt, int offset, int len, const char *cmp)
{
        struct mbuf *n;

        for (; m != NULL; m = n) {
                n = npkt;
                if (npkt)
                        npkt = npkt->m_nextpkt;
                for (; m; m = m->m_next) {
                        for (; offset < m->m_len; offset++, cmp++, len--) {
                                if (len == 0 || *cmp == '\0')
                                        return (1);
                                else if (*cmp != *(mtod(m, char *) + offset))
                                        return (0);
                        }
                        if (len == 0 || *cmp == '\0')
                                return (1);
                        offset = 0;
                }
        }
        return (0);
}

#define STRSETUP(sptr, slen, str)                                       \
        do {                                                            \
                sptr = str;                                             \
                slen = sizeof(str) - 1;                                 \
        } while(0)

static void
sohashttpget(struct socket *so, void *arg, int events, int waitflag)
{

        if ((so->so_state & SS_CANTRCVMORE) == 0 && !sbfull(&so->so_rcv)) {
                struct mbuf *m;
                const char *cmp;
                int     cmplen, cc;

                m = so->so_rcv.sb_mb;
                cc = so->so_rcv.sb_cc - 1;
                if (cc < 1)
                        return;
                switch (*mtod(m, char *)) {
                case 'G':
                        STRSETUP(cmp, cmplen, "ET ");
                        break;
                case 'H':
                        STRSETUP(cmp, cmplen, "EAD ");
                        break;
                default:
                        goto fallout;
                }
                if (cc < cmplen) {
                        if (mbufstrncmp(m, m->m_nextpkt, 1, cc, cmp) == 1) {
                                DPRINT("short cc (%d) but mbufstrncmp ok", cc);
                                return;
                        } else {
                                DPRINT("short cc (%d) mbufstrncmp failed", cc);
                                goto fallout;
                        }
                }
                if (mbufstrcmp(m, m->m_nextpkt, 1, cmp) == 1) {
                        DPRINT("mbufstrcmp ok");
                        if (parse_http_version == 0)
                                soishttpconnected(so, arg, events, waitflag);
                        else
                                soparsehttpvers(so, arg, events, waitflag);
                        return;
                }
                DPRINT("mbufstrcmp bad");
        }

fallout:
        DPRINT("fallout");
        so->so_upcall = NULL;
        so->so_rcv.sb_flags &= ~SB_UPCALL;
        soisconnected(so);
        return;
}

static void
soparsehttpvers(struct socket *so, void *arg, int events, int waitflag)
{
        struct mbuf *m, *n;
        int     i, cc, spaces, inspaces;

        if ((so->so_state & SS_CANTRCVMORE) != 0 || sbfull(&so->so_rcv))
                goto fallout;

        m = so->so_rcv.sb_mb;
        cc = so->so_rcv.sb_cc;
        inspaces = spaces = 0;
        for (m = so->so_rcv.sb_mb; m; m = n) {
                n = m->m_nextpkt;
                for (; m; m = m->m_next) {
                        for (i = 0; i < m->m_len; i++, cc--) {
                                switch (*(mtod(m, char *) + i)) {
                                case ' ':
                                        /* tabs? '\t' */
                                        if (!inspaces) {
                                                spaces++;
                                                inspaces = 1;
                                        }
                                        break;
                                case '\r':
                                case '\n':
                                        DPRINT("newline");
                                        goto fallout;
                                default:
                                        if (spaces != 2) {
                                                inspaces = 0;
                                                break;
                                        }

                                        /*
                                         * if we don't have enough characters
                                         * left (cc < sizeof("HTTP/1.0") - 1)
                                         * then see if the remaining ones
                                         * are a request we can parse.
                                         */
                                        if (cc < sizeof("HTTP/1.0") - 1) {
                                                if (mbufstrncmp(m, n, i, cc,
                                                        "HTTP/1.") == 1) {
                                                        DPRINT("ok");
                                                        goto readmore;
                                                } else {
                                                        DPRINT("bad");
                                                        goto fallout;
                                                }
                                        } else if (
                                            mbufstrcmp(m, n, i, "HTTP/1.0") ||
                                            mbufstrcmp(m, n, i, "HTTP/1.1")) {
                                                DPRINT("ok");
                                                soishttpconnected(so,
                                                    arg, events, waitflag);
                                                return;
                                        } else {
                                                DPRINT("bad");
                                                goto fallout;
                                        }
                                }
                        }
                }
        }
readmore:
        DPRINT("readmore");
        /*
         * if we hit here we haven't hit something
         * we don't understand or a newline, so try again
         */
        so->so_upcall = soparsehttpvers;
        so->so_rcv.sb_flags |= SB_UPCALL;
        return;

fallout:
        DPRINT("fallout");
        so->so_upcall = NULL;
        so->so_rcv.sb_flags &= ~SB_UPCALL;
        soisconnected(so);
        return;
}


#define NCHRS 3

static void
soishttpconnected(struct socket *so, void *arg, int events, int waitflag)
{
        char a, b, c;
        struct mbuf *m, *n;
        int ccleft, copied;

        DPRINT("start");
        if ((so->so_state & SS_CANTRCVMORE) != 0 || sbfull(&so->so_rcv))
                goto gotit;

        /*
         * Walk the socketbuffer and copy the last NCHRS (3) into a, b, and c
         * copied - how much we've copied so far
         * ccleft - how many bytes remaining in the socketbuffer
         * just loop over the mbufs subtracting from 'ccleft' until we only
         * have NCHRS left
         */
        copied = 0;
        ccleft = so->so_rcv.sb_cc;
        if (ccleft < NCHRS)
                goto readmore;
        a = b = c = '\0';
        for (m = so->so_rcv.sb_mb; m; m = n) {
                n = m->m_nextpkt;
                for (; m; m = m->m_next) {
                        ccleft -= m->m_len;
                        if (ccleft <= NCHRS) {
                                char *src;
                                int tocopy;

                                tocopy = (NCHRS - ccleft) - copied;
                                src = mtod(m, char *) + (m->m_len - tocopy);

                                while (tocopy--) {
                                        switch (copied++) {
                                        case 0:
                                                a = *src++;
                                                break;
                                        case 1:
                                                b = *src++;
                                                break;
                                        case 2:
                                                c = *src++;
                                                break;
                                        }
                                }
                        }
                }
        }
        if (c == '\n' && (b == '\n' || (b == '\r' && a == '\n'))) {
                /* we have all request headers */
                goto gotit;
        }

readmore:
        so->so_upcall = soishttpconnected;
        so->so_rcv.sb_flags |= SB_UPCALL;
        return;

gotit:
        so->so_upcall = NULL;
        so->so_rcv.sb_flags &= ~SB_UPCALL;
        soisconnected(so);
        return;
}