suricata/src/decode-ppp.c

/* Copyright (C) 2007-2024 Open Information Security Foundation
 *
 * You can copy, redistribute or modify this Program under the terms of
 * the GNU General Public License version 2 as published by the Free
 * Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

/**
 * \ingroup decode
 *
 * @{
 */


/**
 * \file
 *
 * \author Breno Silva Pinto <breno.silva@gmail.com>
 *
 * Decode PPP
 */

#include "suricata-common.h"
#include "decode.h"
#include "decode-ppp.h"
#include "decode-events.h"

#include "flow.h"

#include "util-validate.h"
#include "util-unittest.h"
#include "util-debug.h"

static int DecodePPPCompressedProto(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
        const uint8_t *pkt, uint32_t len, uint16_t proto_offset)
{
    const uint32_t data_offset = proto_offset + 1;
    switch (*(pkt + proto_offset)) {
        case 0x21: { /* PPP_IP */
            if (unlikely(len < (data_offset + IPV4_HEADER_LEN))) {
                ENGINE_SET_INVALID_EVENT(p, PPPVJU_PKT_TOO_SMALL);
                return TM_ECODE_FAILED;
            }
            DEBUG_VALIDATE_BUG_ON(len < data_offset);
            uint16_t iplen = (uint16_t)MIN((uint32_t)USHRT_MAX, len - data_offset);
            return DecodeIPV4(tv, dtv, p, pkt + data_offset, iplen);
        }
        case 0x57: { /* PPP_IPV6 */
            if (unlikely(len < (data_offset + IPV6_HEADER_LEN))) {
                ENGINE_SET_INVALID_EVENT(p, PPPIPV6_PKT_TOO_SMALL);
                return TM_ECODE_FAILED;
            }
            DEBUG_VALIDATE_BUG_ON(len < data_offset);
            uint16_t iplen = (uint16_t)MIN((uint32_t)USHRT_MAX, len - data_offset);
            return DecodeIPV6(tv, dtv, p, pkt + data_offset, iplen);
        }
        case 0x2f: /* PPP_VJ_UCOMP */
            if (unlikely(len < (data_offset + IPV4_HEADER_LEN))) {
                ENGINE_SET_INVALID_EVENT(p, PPPVJU_PKT_TOO_SMALL);
                return TM_ECODE_FAILED;
            }

            if (unlikely(len > data_offset + USHRT_MAX)) {
                return TM_ECODE_FAILED;
            }

            if (likely(IPV4_GET_RAW_VER((IPV4Hdr *)(pkt + data_offset)) == 4)) {
                p->flags |= PKT_PPP_VJ_UCOMP;
                return DecodeIPV4(tv, dtv, p, pkt + data_offset, (uint16_t)(len - data_offset));
            } else
                return TM_ECODE_FAILED;
            break;

        default:
            ENGINE_SET_EVENT(p, PPP_UNSUP_PROTO);
            return TM_ECODE_OK;
    }
}

static int DecodePPPUncompressedProto(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
        const uint8_t *pkt, uint32_t len, const uint16_t proto, const uint32_t data_offset)
{
    switch (proto) {
        case PPP_VJ_UCOMP:
            if (unlikely(len < (data_offset + IPV4_HEADER_LEN))) {
                ENGINE_SET_INVALID_EVENT(p, PPPVJU_PKT_TOO_SMALL);
                return TM_ECODE_FAILED;
            }

            if (unlikely(len > data_offset + USHRT_MAX)) {
                return TM_ECODE_FAILED;
            }

            if (likely(IPV4_GET_RAW_VER((IPV4Hdr *)(pkt + data_offset)) == 4)) {
                return DecodeIPV4(tv, dtv, p, pkt + data_offset, (uint16_t)(len - data_offset));
            } else
                return TM_ECODE_FAILED;
            break;

        case PPP_IP:
            if (unlikely(len < (data_offset + IPV4_HEADER_LEN))) {
                ENGINE_SET_INVALID_EVENT(p, PPPIPV4_PKT_TOO_SMALL);
                return TM_ECODE_FAILED;
            }
            if (unlikely(len > data_offset + USHRT_MAX)) {
                return TM_ECODE_FAILED;
            }

            return DecodeIPV4(tv, dtv, p, pkt + data_offset, (uint16_t)(len - data_offset));

            /* PPP IPv6 was not tested */
        case PPP_IPV6:
            if (unlikely(len < (data_offset + IPV6_HEADER_LEN))) {
                ENGINE_SET_INVALID_EVENT(p, PPPIPV6_PKT_TOO_SMALL);
                return TM_ECODE_FAILED;
            }
            if (unlikely(len > data_offset + USHRT_MAX)) {
                return TM_ECODE_FAILED;
            }

            return DecodeIPV6(tv, dtv, p, pkt + data_offset, (uint16_t)(len - data_offset));

        case PPP_VJ_COMP:
        case PPP_IPX:
        case PPP_OSI:
        case PPP_NS:
        case PPP_DECNET:
        case PPP_APPLE:
        case PPP_BRPDU:
        case PPP_STII:
        case PPP_VINES:
        case PPP_HELLO:
        case PPP_LUXCOM:
        case PPP_SNS:
        case PPP_MPLS_UCAST:
        case PPP_MPLS_MCAST:
        case PPP_IPCP:
        case PPP_OSICP:
        case PPP_NSCP:
        case PPP_DECNETCP:
        case PPP_APPLECP:
        case PPP_IPXCP:
        case PPP_STIICP:
        case PPP_VINESCP:
        case PPP_IPV6CP:
        case PPP_MPLSCP:
        case PPP_LCP:
        case PPP_PAP:
        case PPP_LQM:
        case PPP_CHAP:
        case PPP_CCP:
        case PPP_CBCP:
        case PPP_COMP_DGRAM:
            ENGINE_SET_EVENT(p,PPP_UNSUP_PROTO);
            return TM_ECODE_OK;

        default:
            SCLogDebug("unknown PPP protocol: %x", proto);
            ENGINE_SET_INVALID_EVENT(p, PPP_WRONG_TYPE);
            return TM_ECODE_OK;
    }
}

int DecodePPP(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p, const uint8_t *pkt, uint32_t len)
{
    DEBUG_VALIDATE_BUG_ON(pkt == NULL);

    StatsIncr(tv, dtv->counter_ppp);
    if (unlikely(len < 1)) {
        ENGINE_SET_INVALID_EVENT(p, PPP_PKT_TOO_SMALL);
        return TM_ECODE_FAILED;
    }

    uint16_t proto_offset = 0;
    /* 0xff means we have a HDLC header: proto will start at offset 2 */
    if (*pkt == 0xff) {
        proto_offset = 2;
        /* make sure the proto field at the offset fits */
        if (len < 3) {
            ENGINE_SET_INVALID_EVENT(p, PPP_PKT_TOO_SMALL);
            return TM_ECODE_FAILED;
        }
    }
    uint8_t proto_size = 0;
    uint8_t proto_byte = *(pkt + proto_offset);
    /* check if compressed protocol bit is set. */
    if (proto_byte & 0x01) {
        proto_size = 1;
    } else {
        proto_size = 2;
    }
    if (len < (proto_size + proto_offset)) {
        ENGINE_SET_INVALID_EVENT(p, PPP_PKT_TOO_SMALL);
        return TM_ECODE_FAILED;
    }
    if (!PacketIncreaseCheckLayers(p)) {
        return TM_ECODE_FAILED;
    }

    const uint32_t data_offset = proto_offset + proto_size;
    if (data_offset != 4) {
        if (proto_size == 1) {
            return DecodePPPCompressedProto(tv, dtv, p, pkt, len, proto_offset);
        } else {
            const uint16_t proto = SCNtohs(*(uint16_t *)(pkt + proto_offset));
            return DecodePPPUncompressedProto(tv, dtv, p, pkt, len, proto, data_offset);
        }
    }
    /* implied proto_offset + proto_size == 4, so continue below */

    const PPPHdr *ppph = (PPPHdr *)pkt;
    SCLogDebug(
            "p %p pkt %p PPP protocol %04x Len: %" PRIu32 "", p, pkt, SCNtohs(ppph->protocol), len);
    return DecodePPPUncompressedProto(tv, dtv, p, pkt, len, SCNtohs(ppph->protocol), data_offset);
}

/* TESTS BELOW */
#ifdef UNITTESTS

/*  DecodePPPtest01
 *  Decode malformed ip layer PPP packet
 *  Expected test value: 1
 */
static int DecodePPPtest01 (void)
{
    uint8_t raw_ppp[] = { 0xff, 0x03, 0x00, 0x21, 0x45, 0xc0, 0x00 };
    Packet *p = PacketGetFromAlloc();
    if (unlikely(p == NULL))
        return 0;
    ThreadVars tv;
    DecodeThreadVars dtv;

    memset(&tv, 0, sizeof(ThreadVars));
    memset(&dtv, 0, sizeof(DecodeThreadVars));

    DecodePPP(&tv, &dtv, p, raw_ppp, sizeof(raw_ppp));

    /* Function my returns here with expected value */

    if(ENGINE_ISSET_EVENT(p,PPPIPV4_PKT_TOO_SMALL))  {
        SCFree(p);
        return 1;
    }

    SCFree(p);
    return 0;
}

/*  DecodePPPtest02
 *  Decode malformed ppp layer packet
 *  Expected test value: 1
 */
static int DecodePPPtest02 (void)
{
    uint8_t raw_ppp[] = { 0xff, 0x03, 0x00, 0xff, 0x45, 0xc0, 0x00, 0x2c, 0x4d,
                           0xed, 0x00, 0x00, 0xff, 0x06, 0xd5, 0x17, 0xbf, 0x01,
                           0x0d, 0x01, 0xbf, 0x01, 0x0d, 0x03, 0xea, 0x37, 0x00,
                           0x17, 0x6d, 0x0b, 0xba, 0xc3, 0x00, 0x00, 0x00, 0x00,
                           0x60, 0x02, 0x10, 0x20, 0xdd, 0xe1, 0x00, 0x00 };
    Packet *p = PacketGetFromAlloc();
    if (unlikely(p == NULL))
        return 0;
    ThreadVars tv;
    DecodeThreadVars dtv;

    memset(&tv, 0, sizeof(ThreadVars));
    memset(&dtv, 0, sizeof(DecodeThreadVars));

    DecodePPP(&tv, &dtv, p, raw_ppp, sizeof(raw_ppp));

    /* Function must returns here */

    if(ENGINE_ISSET_EVENT(p,PPP_WRONG_TYPE))  {
        SCFree(p);
        return 1;
    }

    SCFree(p);
    return 0;
}

/** DecodePPPtest03
 *  \brief Decode good PPP packet, additionally the IPv4 packet inside is
 *         4 bytes short.
 *  \retval 0 Test failed
 *  \retval 1 Test succeeded
 */
static int DecodePPPtest03 (void)
{
    uint8_t raw_ppp[] = { 0xff, 0x03, 0x00, 0x21, 0x45, 0xc0, 0x00, 0x2c, 0x4d,
                           0xed, 0x00, 0x00, 0xff, 0x06, 0xd5, 0x17, 0xbf, 0x01,
                           0x0d, 0x01, 0xbf, 0x01, 0x0d, 0x03, 0xea, 0x37, 0x00,
                           0x17, 0x6d, 0x0b, 0xba, 0xc3, 0x00, 0x00, 0x00, 0x00,
                           0x60, 0x02, 0x10, 0x20, 0xdd, 0xe1, 0x00, 0x00 };
    Packet *p = PacketGetFromAlloc();
    if (unlikely(p == NULL))
        return 0;
    ThreadVars tv;
    DecodeThreadVars dtv;

    memset(&tv, 0, sizeof(ThreadVars));
    memset(&dtv, 0, sizeof(DecodeThreadVars));

    FlowInitConfig(FLOW_QUIET);

    DecodePPP(&tv, &dtv, p, raw_ppp, sizeof(raw_ppp));

    FlowShutdown();

    if(ENGINE_ISSET_EVENT(p,PPP_PKT_TOO_SMALL))  {
        SCFree(p);
        return 0;
    }

    if(ENGINE_ISSET_EVENT(p,PPPIPV4_PKT_TOO_SMALL))  {
        SCFree(p);
        return 0;
    }

    if(ENGINE_ISSET_EVENT(p,PPP_WRONG_TYPE))  {
        SCFree(p);
        return 0;
    }

    if (!(ENGINE_ISSET_EVENT(p,IPV4_TRUNC_PKT))) {
        SCFree(p);
        return 0;
    }
    /* Function must return here */

    SCFree(p);
    return 1;
}


/*  DecodePPPtest04
 *  Check if ppp header is null
 *  Expected test value: 1
 */

static int DecodePPPtest04 (void)
{
    uint8_t raw_ppp[] = { 0xff, 0x03, 0x00, 0x21, 0x45, 0xc0, 0x00, 0x2c, 0x4d,
                           0xed, 0x00, 0x00, 0xff, 0x06, 0xd5, 0x17, 0xbf, 0x01,
                           0x0d, 0x01, 0xbf, 0x01, 0x0d, 0x03, 0xea, 0x37, 0x00,
                           0x17, 0x6d, 0x0b, 0xba, 0xc3, 0x00, 0x00, 0x00, 0x00,
                           0x60, 0x02, 0x10, 0x20, 0xdd, 0xe1, 0x00, 0x00 };
    Packet *p = PacketGetFromAlloc();
    if (unlikely(p == NULL))
        return 0;
    ThreadVars tv;
    DecodeThreadVars dtv;

    memset(&tv, 0, sizeof(ThreadVars));
    memset(&dtv, 0, sizeof(DecodeThreadVars));

    FlowInitConfig(FLOW_QUIET);

    DecodePPP(&tv, &dtv, p, raw_ppp, sizeof(raw_ppp));

    FlowShutdown();

    if (!(ENGINE_ISSET_EVENT(p,IPV4_TRUNC_PKT))) {
        SCFree(p);
        return 0;
    }

    /* Function must returns here */

    SCFree(p);
    return 1;
}
#endif /* UNITTESTS */

void DecodePPPRegisterTests(void)
{
#ifdef UNITTESTS
    UtRegisterTest("DecodePPPtest01", DecodePPPtest01);
    UtRegisterTest("DecodePPPtest02", DecodePPPtest02);
    UtRegisterTest("DecodePPPtest03", DecodePPPtest03);
    UtRegisterTest("DecodePPPtest04", DecodePPPtest04);
#endif /* UNITTESTS */
}

/**
 * @}
 */