fixed all pluto compiler warnings

[strongswan.git] / src / pluto / spdb.c

/* Security Policy Data Base (such as it is)
 * Copyright (C) 1998-2001  D. Hugh Redelmeier.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * 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.
 *
 * RCSID $Id$
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/queue.h>

#include <freeswan.h>
#include <ipsec_policy.h>

#include "constants.h"
#include "defs.h"
#include "id.h"
#include "connections.h"
#include "state.h"
#include "packet.h"
#include "keys.h"
#include "kernel.h"
#include "log.h"
#include "spdb.h"
#include "whack.h"
#include "sha1.h"
#include "md5.h"
#include "crypto.h" /* requires sha1.h and md5.h */
#include "alg_info.h"
#include "kernel_alg.h"
#include "ike_alg.h"
#include "db_ops.h"
#include "nat_traversal.h"

#define AD(x) x, elemsof(x)     /* Array Description */
#define AD_NULL NULL, 0

/**************** Oakely (main mode) SA database ****************/

/* array of proposals to be conjoined (can only be one for Oakley) */

static struct db_prop oakley_pc[] =
    { { PROTO_ISAKMP, AD_NULL } };

/* array of proposal conjuncts (can only be one) */

static struct db_prop_conj oakley_props[] = { { AD(oakley_pc) } };

/* the sadb entry */
struct db_sa oakley_sadb = { AD(oakley_props) };

/**************** IPsec (quick mode) SA database ****************/

/* arrays of attributes for transforms */

static struct db_attr espsha1_attr[] = {
    { AUTH_ALGORITHM, AUTH_ALGORITHM_HMAC_SHA1 },
    };

static struct db_attr ah_HMAC_SHA1_attr[] = {
    { AUTH_ALGORITHM, AUTH_ALGORITHM_HMAC_SHA1 },
    };

/* arrays of transforms, each in in preference order */

static struct db_trans espa_trans[] = {
    { ESP_3DES, AD(espsha1_attr) },
    };

static struct db_trans esp_trans[] = {
    { ESP_3DES, AD_NULL },
    };

#ifdef SUPPORT_ESP_NULL
static struct db_trans espnull_trans[] = {
    { ESP_NULL, AD(espsha1_attr) },
    };
#endif /* SUPPORT_ESP_NULL */

static struct db_trans ah_trans[] = {
    { AH_SHA, AD(ah_HMAC_SHA1_attr) },
    };

static struct db_trans ipcomp_trans[] = {
    { IPCOMP_DEFLATE, AD_NULL },
    };

/* arrays of proposals to be conjoined */

static struct db_prop ah_pc[] = {
    { PROTO_IPSEC_AH, AD(ah_trans) },
    };

#ifdef SUPPORT_ESP_NULL
static struct db_prop espnull_pc[] = {
    { PROTO_IPSEC_ESP, AD(espnull_trans) },
    };
#endif /* SUPPORT_ESP_NULL */

static struct db_prop esp_pc[] = {
    { PROTO_IPSEC_ESP, AD(espa_trans) },
    };

static struct db_prop ah_esp_pc[] = {
    { PROTO_IPSEC_AH, AD(ah_trans) },
    { PROTO_IPSEC_ESP, AD(esp_trans) },
    };

static struct db_prop compress_pc[] = {
    { PROTO_IPCOMP, AD(ipcomp_trans) },
    };

static struct db_prop ah_compress_pc[] = {
    { PROTO_IPSEC_AH, AD(ah_trans) },
    { PROTO_IPCOMP, AD(ipcomp_trans) },
    };

#ifdef SUPPORT_ESP_NULL
static struct db_prop espnull_compress_pc[] = {
    { PROTO_IPSEC_ESP, AD(espnull_trans) },
    { PROTO_IPCOMP, AD(ipcomp_trans) },
    };
#endif /* SUPPORT_ESP_NULL */

static struct db_prop esp_compress_pc[] = {
    { PROTO_IPSEC_ESP, AD(espa_trans) },
    { PROTO_IPCOMP, AD(ipcomp_trans) },
    };

static struct db_prop ah_esp_compress_pc[] = {
    { PROTO_IPSEC_AH, AD(ah_trans) },
    { PROTO_IPSEC_ESP, AD(esp_trans) },
    { PROTO_IPCOMP, AD(ipcomp_trans) },
    };

/* arrays of proposal alternatives (each element is a conjunction) */

static struct db_prop_conj ah_props[] = {
    { AD(ah_pc) },
#ifdef SUPPORT_ESP_NULL
    { AD(espnull_pc) }
#endif
    };

static struct db_prop_conj esp_props[] =
    { { AD(esp_pc) } };

static struct db_prop_conj ah_esp_props[] =
    { { AD(ah_esp_pc) } };

static struct db_prop_conj compress_props[] = {
    { AD(compress_pc) },
    };

static struct db_prop_conj ah_compress_props[] = {
    { AD(ah_compress_pc) },
#ifdef SUPPORT_ESP_NULL
    { AD(espnull_compress_pc) }
#endif
    };

static struct db_prop_conj esp_compress_props[] =
    { { AD(esp_compress_pc) } };

static struct db_prop_conj ah_esp_compress_props[] =
    { { AD(ah_esp_compress_pc) } };

/* The IPsec sadb is subscripted by a bitset (subset of policy)
 * with members from { POLICY_ENCRYPT, POLICY_AUTHENTICATE, POLICY_COMPRESS }
 * shifted right by POLICY_IPSEC_SHIFT.
 */
struct db_sa ipsec_sadb[1 << 3] = {
    { AD_NULL },        /* none */
    { AD(esp_props) },  /* POLICY_ENCRYPT */
    { AD(ah_props) },   /* POLICY_AUTHENTICATE */
    { AD(ah_esp_props) },       /* POLICY_ENCRYPT+POLICY_AUTHENTICATE */
    { AD(compress_props) },     /* POLICY_COMPRESS */
    { AD(esp_compress_props) }, /* POLICY_ENCRYPT+POLICY_COMPRESS */
    { AD(ah_compress_props) },  /* POLICY_AUTHENTICATE+POLICY_COMPRESS */
    { AD(ah_esp_compress_props) },      /* POLICY_ENCRYPT+POLICY_AUTHENTICATE+POLICY_COMPRESS */
    };

#undef AD
#undef AD_NULL

/* output an attribute (within an SA) */
static bool
out_attr(int type
, unsigned long val
, struct_desc *attr_desc
, enum_names **attr_val_descs USED_BY_DEBUG
, pb_stream *pbs)
{
    struct isakmp_attribute attr;

    if (val >> 16 == 0)
    {
        /* short value: use TV form */
        attr.isaat_af_type = type | ISAKMP_ATTR_AF_TV;
        attr.isaat_lv = val;
        if (!out_struct(&attr, attr_desc, pbs, NULL))
            return FALSE;
    }
    else
    {
        /* This is a real fudge!  Since we rarely use long attributes
         * and since this is the only place where we can cause an
         * ISAKMP message length to be other than a multiple of 4 octets,
         * we force the length of the value to be a multiple of 4 octets.
         * Furthermore, we only handle values up to 4 octets in length.
         * Voila: a fixed format!
         */
        pb_stream val_pbs;
        u_int32_t nval = htonl(val);

        attr.isaat_af_type = type | ISAKMP_ATTR_AF_TLV;
        if (!out_struct(&attr, attr_desc, pbs, &val_pbs)
        || !out_raw(&nval, sizeof(nval), &val_pbs, "long attribute value"))
            return FALSE;
        close_output_pbs(&val_pbs);
    }
    DBG(DBG_EMITTING,
        enum_names *d = attr_val_descs[type];

        if (d != NULL)
            DBG_log("    [%lu is %s]"
                , val, enum_show(d, val)));
    return TRUE;
}
#define return_on(var, val) do { var=val;goto return_out; } while(0);
/* Output an SA, as described by a db_sa.
 * This has the side-effect of allocating SPIs for us.
 */
bool
out_sa(pb_stream *outs
, struct db_sa *sadb
, struct state *st
, bool oakley_mode
, u_int8_t np)
{
    pb_stream sa_pbs;
    int pcn;
    bool ret = FALSE;
    bool ah_spi_generated = FALSE
        , esp_spi_generated = FALSE
        , ipcomp_cpi_generated = FALSE;
#if !defined NO_KERNEL_ALG || !defined NO_IKE_ALG
    struct db_context *db_ctx = NULL;
#endif

    /* SA header out */
    {
        struct isakmp_sa sa;

        sa.isasa_np = np;
        st->st_doi = sa.isasa_doi = ISAKMP_DOI_IPSEC;   /* all we know */
        if (!out_struct(&sa, &isakmp_sa_desc, outs, &sa_pbs))
            return_on(ret, FALSE);
    }

    /* within SA: situation out */
    st->st_situation = SIT_IDENTITY_ONLY;
    if (!out_struct(&st->st_situation, &ipsec_sit_desc, &sa_pbs, NULL))
        return_on(ret, FALSE);

    /* within SA: Proposal Payloads
     *
     * Multiple Proposals with the same number are simultaneous
     * (conjuncts) and must deal with different protocols (AH or ESP).
     * Proposals with different numbers are alternatives (disjuncts),
     * in preference order.
     * Proposal numbers must be monotonic.
     * See RFC 2408 "ISAKMP" 4.2
     */

    for (pcn = 0; pcn != sadb->prop_conj_cnt; pcn++)
    {
        struct db_prop_conj *pc = &sadb->prop_conjs[pcn];
        int pn;

        for (pn = 0; pn != pc->prop_cnt; pn++)
        {
            struct db_prop *p = &pc->props[pn];
            pb_stream proposal_pbs;
            struct isakmp_proposal proposal;
            struct_desc *trans_desc = NULL;
            struct_desc *attr_desc = NULL;
            enum_names **attr_val_descs = NULL;
            int tn;
            bool tunnel_mode;

            tunnel_mode = (pn == pc->prop_cnt-1)
                && (st->st_policy & POLICY_TUNNEL);

            /* Proposal header */
            proposal.isap_np = pcn == sadb->prop_conj_cnt-1 && pn == pc->prop_cnt-1
                ? ISAKMP_NEXT_NONE : ISAKMP_NEXT_P;
            proposal.isap_proposal = pcn;
            proposal.isap_protoid = p->protoid;
            proposal.isap_spisize = oakley_mode ? 0
                : p->protoid == PROTO_IPCOMP ? IPCOMP_CPI_SIZE
                : IPSEC_DOI_SPI_SIZE;

            /* In quick mode ONLY, create proposal for runtime kernel algos.
             *  Replace ESP proposals with runtime created one
             */
            if (!oakley_mode && p->protoid == PROTO_IPSEC_ESP)
            {
                DBG(DBG_CONTROL | DBG_CRYPT,
                    if (st->st_connection->alg_info_esp)
                    {
                        static char buf[256]="";

                        alg_info_snprint(buf, sizeof (buf),
                                (struct alg_info *)st->st_connection->alg_info_esp);
                        DBG_log(buf);
                    }
                )
                db_ctx = kernel_alg_db_new(st->st_connection->alg_info_esp, st->st_policy);
                p = db_prop_get(db_ctx);

                if (!p || p->trans_cnt == 0)
                {
                    loglog(RC_LOG_SERIOUS,
                        "empty IPSEC SA proposal to send "
                        "(no kernel algorithms for esp selection)");
                    return_on(ret, FALSE);
                }
            }

            if (oakley_mode && p->protoid == PROTO_ISAKMP)
            {
                DBG(DBG_CONTROL | DBG_CRYPT,
                    if (st->st_connection->alg_info_ike)
                    {
                        static char buf[256]="";

                        alg_info_snprint(buf, sizeof (buf),
                                (struct alg_info *)st->st_connection->alg_info_ike);
                        DBG_log(buf);
                    }
                )
                db_ctx = ike_alg_db_new(st->st_connection->alg_info_ike, st->st_policy);
                p = db_prop_get(db_ctx);

                if (!p || p->trans_cnt == 0)
                {
                    loglog(RC_LOG_SERIOUS,
                        "empty ISAKMP SA proposal to send "
                        "(no algorithms for ike selection?)");
                    return_on(ret, FALSE);
                }
            }

            proposal.isap_notrans = p->trans_cnt;
            if (!out_struct(&proposal, &isakmp_proposal_desc, &sa_pbs, &proposal_pbs))
                return_on(ret, FALSE);

            /* Per-protocols stuff:
             * Set trans_desc.
             * Set attr_desc.
             * Set attr_val_descs.
             * If not oakley_mode, emit SPI.
             * We allocate SPIs on demand.
             * All ESPs in an SA will share a single SPI.
             * All AHs in an SAwill share a single SPI.
             * AHs' SPI will be distinct from ESPs'.
             * This latter is needed because KLIPS doesn't
             * use the protocol when looking up a (dest, protocol, spi).
             * ??? If multiple ESPs are composed, how should their SPIs
             * be allocated?
             */
            {
                ipsec_spi_t *spi_ptr = NULL;
                int proto = 0;
                bool *spi_generated = NULL;

                switch (p->protoid)
                {
                case PROTO_ISAKMP:
                    passert(oakley_mode);
                    trans_desc = &isakmp_isakmp_transform_desc;
                    attr_desc = &isakmp_oakley_attribute_desc;
                    attr_val_descs = oakley_attr_val_descs;
                    /* no SPI needed */
                    break;
                case PROTO_IPSEC_AH:
                    passert(!oakley_mode);
                    trans_desc = &isakmp_ah_transform_desc;
                    attr_desc = &isakmp_ipsec_attribute_desc;
                    attr_val_descs = ipsec_attr_val_descs;
                    spi_ptr = &st->st_ah.our_spi;
                    spi_generated = &ah_spi_generated;
                    proto = IPPROTO_AH;
                    break;
                case PROTO_IPSEC_ESP:
                    passert(!oakley_mode);
                    trans_desc = &isakmp_esp_transform_desc;
                    attr_desc = &isakmp_ipsec_attribute_desc;
                    attr_val_descs = ipsec_attr_val_descs;
                    spi_ptr = &st->st_esp.our_spi;
                    spi_generated = &esp_spi_generated;
                    proto = IPPROTO_ESP;
                    break;
                case PROTO_IPCOMP:
                    passert(!oakley_mode);
                    trans_desc = &isakmp_ipcomp_transform_desc;
                    attr_desc = &isakmp_ipsec_attribute_desc;
                    attr_val_descs = ipsec_attr_val_descs;

                    /* a CPI isn't quite the same as an SPI
                     * so we use specialized code to emit it.
                     */
                    if (!ipcomp_cpi_generated)
                    {
                        st->st_ipcomp.our_spi = get_my_cpi(
                            &st->st_connection->spd, tunnel_mode);
                        if (st->st_ipcomp.our_spi == 0)
                            return_on(ret, FALSE);      /* problem generating CPI */

                        ipcomp_cpi_generated = TRUE;
                    }
                    /* CPI is stored in network low order end of an
                     * ipsec_spi_t.  So we start a couple of bytes in.
                     */
                    if (!out_raw((u_char *)&st->st_ipcomp.our_spi
                     + IPSEC_DOI_SPI_SIZE - IPCOMP_CPI_SIZE
                    , IPCOMP_CPI_SIZE
                    , &proposal_pbs, "CPI"))
                        return_on(ret, FALSE);
                    break;
                default:
                    bad_case(p->protoid);
                }
                if (spi_ptr != NULL)
                {
                    if (!*spi_generated)
                    {
                        *spi_ptr = get_ipsec_spi(0
                            , proto
                            , &st->st_connection->spd
                            , tunnel_mode);
                        if (*spi_ptr == 0)
                            return FALSE;
                        *spi_generated = TRUE;
                    }
                    if (!out_raw((u_char *)spi_ptr, IPSEC_DOI_SPI_SIZE
                    , &proposal_pbs, "SPI"))
                        return_on(ret, FALSE);
                }
            }

            /* within proposal: Transform Payloads */
            for (tn = 0; tn != p->trans_cnt; tn++)
            {
                struct db_trans *t = &p->trans[tn];
                pb_stream trans_pbs;
                struct isakmp_transform trans;
                int an;

                trans.isat_np = (tn == p->trans_cnt - 1)
                    ? ISAKMP_NEXT_NONE : ISAKMP_NEXT_T;
                trans.isat_transnum = tn;
                trans.isat_transid = t->transid;
                if (!out_struct(&trans, trans_desc, &proposal_pbs, &trans_pbs))
                    return_on(ret, FALSE);

                /* Within tranform: Attributes. */

                /* For Phase 2 / Quick Mode, GROUP_DESCRIPTION is
                 * automatically generated because it must be the same
                 * in every transform.  Except IPCOMP.
                 */
                if (p->protoid != PROTO_IPCOMP
                && st->st_pfs_group != NULL)
                {
                    passert(!oakley_mode);
                    passert(st->st_pfs_group != &unset_group);
                    out_attr(GROUP_DESCRIPTION, st->st_pfs_group->group
                        , attr_desc, attr_val_descs
                        , &trans_pbs);
                }

                /* automatically generate duration
                 * and, for Phase 2 / Quick Mode, encapsulation.
                 */
                if (oakley_mode)
                {
                    out_attr(OAKLEY_LIFE_TYPE, OAKLEY_LIFE_SECONDS
                        , attr_desc, attr_val_descs
                        , &trans_pbs);
                    out_attr(OAKLEY_LIFE_DURATION
                        , st->st_connection->sa_ike_life_seconds
                        , attr_desc, attr_val_descs
                        , &trans_pbs);
                }
                else
                {
                    /* RFC 2407 (IPSEC DOI) 4.5 specifies that
                     * the default is "unspecified (host-dependent)".
                     * This makes little sense, so we always specify it.
                     *
                     * Unlike other IPSEC transforms, IPCOMP defaults
                     * to Transport Mode, so we can exploit the default
                     * (draft-shacham-ippcp-rfc2393bis-05.txt 4.1).
                     */
                    if (p->protoid != PROTO_IPCOMP
                    || st->st_policy & POLICY_TUNNEL)
                    {
#ifndef I_KNOW_TRANSPORT_MODE_HAS_SECURITY_CONCERN_BUT_I_WANT_IT
                        if ((st->nat_traversal & NAT_T_DETECTED)
                        && !(st->st_policy & POLICY_TUNNEL))
                        {
                            /* Inform user that we will not respect policy and only
                             * propose Tunnel Mode
                             */
                            loglog(RC_LOG_SERIOUS, "NAT-Traversal: "
                                "Transport Mode not allowed due to security concerns -- "
                                "using Tunnel mode");
                        }
#endif
                        out_attr(ENCAPSULATION_MODE
#ifdef I_KNOW_TRANSPORT_MODE_HAS_SECURITY_CONCERN_BUT_I_WANT_IT
                            , NAT_T_ENCAPSULATION_MODE(st, st->st_policy)
#else
                                /* If NAT-T is detected, use UDP_TUNNEL as long as Transport
                                 * Mode has security concerns.
                                 *
                                 * User has been informed of that
                                 */
                            , NAT_T_ENCAPSULATION_MODE(st, POLICY_TUNNEL)
#endif
                            , attr_desc, attr_val_descs
                            , &trans_pbs);
                    }
                    out_attr(SA_LIFE_TYPE, SA_LIFE_TYPE_SECONDS
                        , attr_desc, attr_val_descs
                        , &trans_pbs);
                    out_attr(SA_LIFE_DURATION
                        , st->st_connection->sa_ipsec_life_seconds
                        , attr_desc, attr_val_descs
                        , &trans_pbs);
                }

                /* spit out attributes from table */
                for (an = 0; an != t->attr_cnt; an++)
                {
                    struct db_attr *a = &t->attrs[an];

                    out_attr(a->type, a->val
                        , attr_desc, attr_val_descs
                        , &trans_pbs);
                }

                close_output_pbs(&trans_pbs);
            }
            close_output_pbs(&proposal_pbs);
        }
        /* end of a conjunction of proposals */
    }
    close_output_pbs(&sa_pbs);
    ret = TRUE;

return_out:

#if !defined NO_KERNEL_ALG || !defined NO_IKE_ALG
    if (db_ctx)
            db_destroy(db_ctx);
#endif
    return ret;
}

/* Handle long form of duration attribute.
 * The code is can only handle values that can fit in unsigned long.
 * "Clamping" is probably an acceptable way to impose this limitation.
 */
static u_int32_t
decode_long_duration(pb_stream *pbs)
{
    u_int32_t val = 0;

    /* ignore leading zeros */
    while (pbs_left(pbs) != 0 && *pbs->cur == '\0')
        pbs->cur++;

    if (pbs_left(pbs) > sizeof(val))
    {
        /* "clamp" too large value to max representable value */
        val -= 1;       /* portable way to get to maximum value */
        DBG(DBG_PARSING, DBG_log("   too large duration clamped to: %lu"
            , (unsigned long)val));
    }
    else
    {
        /* decode number */
        while (pbs_left(pbs) != 0)
            val = (val << BITS_PER_BYTE) | *pbs->cur++;
        DBG(DBG_PARSING, DBG_log("   long duration: %lu", (unsigned long)val));
    }
    return val;
}

/* Preparse the body of an ISAKMP SA Payload and
 * return body of ISAKMP Proposal Payload 
 *
 * Only IPsec DOI is accepted (what is the ISAKMP DOI?).
 * Error response is rudimentary.
 */
notification_t
preparse_isakmp_sa_body(const struct isakmp_sa *sa
                      , pb_stream *sa_pbs
                      , u_int32_t *ipsecdoisit
                      , pb_stream *proposal_pbs
                      , struct isakmp_proposal *proposal)
{
    /* DOI */
    if (sa->isasa_doi != ISAKMP_DOI_IPSEC)
    {
        loglog(RC_LOG_SERIOUS, "Unknown/unsupported DOI %s", enum_show(&doi_names, sa->isasa_doi));
        /* XXX Could send notification back */
        return DOI_NOT_SUPPORTED;
    }

    /* Situation */
    if (!in_struct(ipsecdoisit, &ipsec_sit_desc, sa_pbs, NULL))
        return SITUATION_NOT_SUPPORTED;

    if (*ipsecdoisit != SIT_IDENTITY_ONLY)
    {
        loglog(RC_LOG_SERIOUS, "unsupported IPsec DOI situation (%s)"
            , bitnamesof(sit_bit_names, *ipsecdoisit));
        /* XXX Could send notification back */
        return SITUATION_NOT_SUPPORTED;
    }

    /* The rules for ISAKMP SAs are scattered.
     * RFC 2409 "IKE" section 5 says that there
     * can only be one SA, and it can have only one proposal in it.
     * There may well be multiple transforms.
     */
    if (!in_struct(proposal, &isakmp_proposal_desc, sa_pbs, proposal_pbs))
        return PAYLOAD_MALFORMED;

    if (proposal->isap_np != ISAKMP_NEXT_NONE)
    {
        loglog(RC_LOG_SERIOUS, "Proposal Payload must be alone in Oakley SA; found %s following Proposal"
            , enum_show(&payload_names, proposal->isap_np));
        return PAYLOAD_MALFORMED;
    }

    if (proposal->isap_protoid != PROTO_ISAKMP)
    {
        loglog(RC_LOG_SERIOUS, "unexpected Protocol ID (%s) found in Oakley Proposal"
            , enum_show(&protocol_names, proposal->isap_protoid));
        return INVALID_PROTOCOL_ID;
    }

    /* Just what should we accept for the SPI field?
     * The RFC is sort of contradictory.  We will ignore the SPI
     * as long as it is of the proper size.
     *
     * From RFC2408 2.4 Identifying Security Associations:
     *   During phase 1 negotiations, the initiator and responder cookies
     *   determine the ISAKMP SA. Therefore, the SPI field in the Proposal
     *   payload is redundant and MAY be set to 0 or it MAY contain the
     *   transmitting entity's cookie.
     *
     * From RFC2408 3.5 Proposal Payload:
     *    o  SPI Size (1 octet) - Length in octets of the SPI as defined by
     *       the Protocol-Id.  In the case of ISAKMP, the Initiator and
     *       Responder cookie pair from the ISAKMP Header is the ISAKMP SPI,
     *       therefore, the SPI Size is irrelevant and MAY be from zero (0) to
     *       sixteen (16).  If the SPI Size is non-zero, the content of the
     *       SPI field MUST be ignored.  If the SPI Size is not a multiple of
     *       4 octets it will have some impact on the SPI field and the
     *       alignment of all payloads in the message.  The Domain of
     *       Interpretation (DOI) will dictate the SPI Size for other
     *       protocols.
     */
    if (proposal->isap_spisize == 0)
    {
        /* empty (0) SPI -- fine */
    }
    else if (proposal->isap_spisize <= MAX_ISAKMP_SPI_SIZE)
    {
        u_char junk_spi[MAX_ISAKMP_SPI_SIZE];

        if (!in_raw(junk_spi, proposal->isap_spisize, proposal_pbs, "Oakley SPI"))
            return PAYLOAD_MALFORMED;
    }
    else
    {
        loglog(RC_LOG_SERIOUS, "invalid SPI size (%u) in Oakley Proposal"
            , (unsigned)proposal->isap_spisize);
        return INVALID_SPI;
    }
    return NOTHING_WRONG;
}

static struct {
    u_int8_t *start;
    u_int8_t *cur;
    u_int8_t *roof;
} backup;

/*
 * backup the pointer into a pb_stream
 */
void
backup_pbs(pb_stream *pbs)
{
    backup.start = pbs->start;
    backup.cur   = pbs->cur;
    backup.roof  = pbs->roof;
}

/*
 * restore the pointer into a pb_stream
 */
void
restore_pbs(pb_stream *pbs)
{
    pbs->start = backup.start;
    pbs->cur   = backup.cur;
    pbs->roof  = backup.roof;
}

/*
 * Parse an ISAKMP Proposal Payload for RSA and PSK authentication policies
 */
notification_t
parse_isakmp_policy(pb_stream *proposal_pbs
                  , u_int notrans
                  , lset_t *policy)
{
    int last_transnum = -1;

    *policy = LEMPTY;

    while (notrans--)
    {
        pb_stream trans_pbs;
        u_char *attr_start;
        size_t attr_len;
        struct isakmp_transform trans;

        if (!in_struct(&trans, &isakmp_isakmp_transform_desc, proposal_pbs, &trans_pbs))
            return BAD_PROPOSAL_SYNTAX;

        if (trans.isat_transnum <= last_transnum)
        {
            /* picky, picky, picky */
            loglog(RC_LOG_SERIOUS, "Transform Numbers are not monotonically increasing"
                " in Oakley Proposal");
            return BAD_PROPOSAL_SYNTAX;
        }
        last_transnum = trans.isat_transnum;

        if (trans.isat_transid != KEY_IKE)
        {
            loglog(RC_LOG_SERIOUS, "expected KEY_IKE but found %s in Oakley Transform"
                , enum_show(&isakmp_transformid_names, trans.isat_transid));
            return INVALID_TRANSFORM_ID;
        }

        attr_start = trans_pbs.cur;
        attr_len = pbs_left(&trans_pbs);

        /* preprocess authentication attributes only */
        while (pbs_left(&trans_pbs) != 0)
        {
            struct isakmp_attribute a;
            pb_stream attr_pbs;

            if (!in_struct(&a, &isakmp_oakley_attribute_desc, &trans_pbs, &attr_pbs))
                return BAD_PROPOSAL_SYNTAX;

            passert((a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK) < 32);

            switch (a.isaat_af_type)
            {
            case OAKLEY_AUTHENTICATION_METHOD | ISAKMP_ATTR_AF_TV:
                switch (a.isaat_lv)
                {
                case OAKLEY_PRESHARED_KEY:
                    *policy |= POLICY_PSK;
                    break;
                case OAKLEY_RSA_SIG:
                    *policy |= POLICY_RSASIG;
                    break;
                case XAUTHInitPreShared:
                    *policy |= POLICY_XAUTH_SERVER;
                    /* fall through */
                case XAUTHRespPreShared:
                    *policy |= POLICY_XAUTH_PSK;
                    break;
                case XAUTHInitRSA:
                    *policy |= POLICY_XAUTH_SERVER;
                    /* fall through */
                case XAUTHRespRSA:
                    *policy |= POLICY_XAUTH_RSASIG;
                    break;
                default:
                    break;
                }
                break;
            default:
                break;
            }
        }
    }
    DBG(DBG_CONTROL|DBG_PARSING,
        DBG_log("preparse_isakmp_policy: peer requests %s authentication"
                , prettypolicy(*policy))
    )
    return NOTHING_WRONG;
}

/* 
 * check that we can find a preshared secret
 */
static err_t
find_preshared_key(struct state* st)
{
    err_t ugh = NULL;
    struct connection *c = st->st_connection;

    if (get_preshared_secret(c) == NULL)
    {
        char my_id[BUF_LEN], his_id[BUF_LEN];

        idtoa(&c->spd.this.id, my_id, sizeof(my_id));
        if (his_id_was_instantiated(c))
            strcpy(his_id, "%any");
        else
            idtoa(&c->spd.that.id, his_id, sizeof(his_id));
        ugh = builddiag("Can't authenticate: no preshared key found for `%s' and `%s'"
                        , my_id, his_id);
    }
    return ugh;
}

/* Parse the body of an ISAKMP SA Payload (i.e. Phase 1 / Main Mode).
 * Various shortcuts are taken.  In particular, the policy, such as
 * it is, is hardwired.
 *
 * If r_sa is non-NULL, the body of an SA representing the selected
 * proposal is emitted.
 *
 * This routine is used by main_inI1_outR1() and main_inR1_outI2().
 */
notification_t
parse_isakmp_sa_body(u_int32_t ipsecdoisit
                   , pb_stream *proposal_pbs
                   , struct isakmp_proposal *proposal
                   , pb_stream *r_sa_pbs
                   , struct state *st
                   , bool initiator)
{
    struct connection *c = st->st_connection;
    unsigned no_trans_left;

    /* for each transform payload... */
    no_trans_left = proposal->isap_notrans;

    for (;;)
    {
        pb_stream trans_pbs;
        u_char *attr_start;
        size_t attr_len;
        struct isakmp_transform trans;
        lset_t seen_attrs = 0;
        lset_t seen_durations = 0;
        u_int16_t life_type = 0;
        struct oakley_trans_attrs ta;
        err_t ugh = NULL;       /* set to diagnostic when problem detected */

        /* initialize only optional field in ta */
        ta.life_seconds = OAKLEY_ISAKMP_SA_LIFETIME_DEFAULT;    /* When this SA expires (seconds) */

        if (no_trans_left == 0)
        {
            loglog(RC_LOG_SERIOUS, "number of Transform Payloads disagrees with Oakley Proposal Payload");
            return BAD_PROPOSAL_SYNTAX;
        }

        in_struct(&trans, &isakmp_isakmp_transform_desc, proposal_pbs, &trans_pbs);
        attr_start = trans_pbs.cur;
        attr_len = pbs_left(&trans_pbs);

        /* process all the attributes that make up the transform */

        while (pbs_left(&trans_pbs) != 0)
        {
            struct isakmp_attribute a;
            pb_stream attr_pbs;
            u_int32_t val;      /* room for larger values */

            if (!in_struct(&a, &isakmp_oakley_attribute_desc, &trans_pbs, &attr_pbs))
                return BAD_PROPOSAL_SYNTAX;

            passert((a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK) < 32);

            if (LHAS(seen_attrs, a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK))
            {
                loglog(RC_LOG_SERIOUS, "repeated %s attribute in Oakley Transform %u"
                    , enum_show(&oakley_attr_names, a.isaat_af_type)
                    , trans.isat_transnum);
                return BAD_PROPOSAL_SYNTAX;
            }

            seen_attrs |= LELEM(a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK);

            val = a.isaat_lv;

            DBG(DBG_PARSING,
            {
                enum_names *vdesc = oakley_attr_val_descs
                    [a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK];

                if (vdesc != NULL)
                {
                    const char *nm = enum_name(vdesc, val);

                    if (nm != NULL)
                        DBG_log("   [%u is %s]", (unsigned)val, nm);
                }
            });

            switch (a.isaat_af_type)
            {
            case OAKLEY_ENCRYPTION_ALGORITHM | ISAKMP_ATTR_AF_TV:
                if (ike_alg_enc_present(val))
                {
                    ta.encrypt = val;
                    ta.encrypter = ike_alg_get_encrypter(val);
                    ta.enckeylen = ta.encrypter->keydeflen;
                }
                else
                {
                    ugh = builddiag("%s is not supported"
                            , enum_show(&oakley_enc_names, val));
                }
                break;

            case OAKLEY_HASH_ALGORITHM | ISAKMP_ATTR_AF_TV:
                if (ike_alg_hash_present(val))
                {
                    ta.hash = val;
                    ta.hasher = ike_alg_get_hasher(val);
                }
                else
                {
                    ugh = builddiag("%s is not supported"
                            , enum_show(&oakley_hash_names, val));
                }
                break;

            case OAKLEY_AUTHENTICATION_METHOD | ISAKMP_ATTR_AF_TV:
                {
                    /* check that authentication method is acceptable */
                    lset_t iap = st->st_policy & POLICY_ID_AUTH_MASK;

                    /* is the initiator the XAUTH client? */
                    bool xauth_init = ( initiator && (st->st_policy & POLICY_XAUTH_SERVER) == LEMPTY)
                                   || (!initiator && (st->st_policy & POLICY_XAUTH_SERVER) != LEMPTY);

                    switch (val)
                    {
                    case OAKLEY_PRESHARED_KEY:
                        if ((iap & POLICY_PSK) == LEMPTY)
                        {
                            ugh = "policy does not allow OAKLEY_PRESHARED_KEY authentication";
                        }
                        else
                        {
                            ugh = find_preshared_key(st);
                            ta.auth = OAKLEY_PRESHARED_KEY;
                        }
                        break;
                    case XAUTHInitPreShared:
                        if ((iap & POLICY_XAUTH_PSK) == LEMPTY || !xauth_init)
                        {
                            ugh = "policy does not allow XAUTHInitPreShared authentication";
                        }
                        else
                        {
                            ugh = find_preshared_key(st);
                            ta.auth = XAUTHInitPreShared;
                        }
                        break;
                    case XAUTHRespPreShared:
                        if ((iap & POLICY_XAUTH_PSK) == LEMPTY || xauth_init)
                        {
                            ugh = "policy does not allow XAUTHRespPreShared authentication";
                        }
                        else
                        {
                            ugh = find_preshared_key(st);
                            ta.auth = XAUTHRespPreShared;
                        }
                        break;
                    case OAKLEY_RSA_SIG:
                        /* Accept if policy specifies RSASIG or is default */
                        if ((iap & POLICY_RSASIG) == LEMPTY)
                        {
                            ugh = "policy does not allow OAKLEY_RSA_SIG authentication";
                        }
                        else
                        {
                            ta.auth = OAKLEY_RSA_SIG;
                        }
                        break;
                    case XAUTHInitRSA:
                        if ((iap & POLICY_XAUTH_RSASIG) == LEMPTY || !xauth_init)
                        {
                            ugh = "policy does not allow XAUTHInitRSA authentication";
                        }
                        else
                        {
                            ta.auth = XAUTHInitRSA;
                        }
                        break;
                    case XAUTHRespRSA:
                        if ((iap & POLICY_XAUTH_RSASIG) == LEMPTY || xauth_init)
                        {
                            ugh = "policy does not allow XAUTHRespRSA authentication";
                        }
                        else
                        {
                            ta.auth = XAUTHRespRSA;
                        }
                        break;
                    default:
                        ugh = builddiag("Pluto does not support %s authentication"
                            , enum_show(&oakley_auth_names, val));
                        break;
                    }
                }
                break;

            case OAKLEY_GROUP_DESCRIPTION | ISAKMP_ATTR_AF_TV:
                ta.group = lookup_group(val);
                if (ta.group == NULL)
                {
                    ugh = "only OAKLEY_GROUP_MODP1024 and OAKLEY_GROUP_MODP1536 supported";
                }
                break;

            case OAKLEY_LIFE_TYPE | ISAKMP_ATTR_AF_TV:
                switch (val)
                {
                case OAKLEY_LIFE_SECONDS:
                case OAKLEY_LIFE_KILOBYTES:
                    if (LHAS(seen_durations, val))
                    {
                        loglog(RC_LOG_SERIOUS
                                , "attribute OAKLEY_LIFE_TYPE value %s repeated"
                                , enum_show(&oakley_lifetime_names, val));
                        return BAD_PROPOSAL_SYNTAX;
                    }
                    seen_durations |= LELEM(val);
                    life_type = val;
                    break;
                default:
                    ugh = builddiag("unknown value %s"
                            , enum_show(&oakley_lifetime_names, val));
                    break;
                }
                break;

            case OAKLEY_LIFE_DURATION | ISAKMP_ATTR_AF_TLV:
                val = decode_long_duration(&attr_pbs);
                /* fall through */
            case OAKLEY_LIFE_DURATION | ISAKMP_ATTR_AF_TV:
                if (!LHAS(seen_attrs, OAKLEY_LIFE_TYPE))
                {
                    ugh = "OAKLEY_LIFE_DURATION attribute not preceded by OAKLEY_LIFE_TYPE attribute";
                    break;
                }
                seen_attrs &= ~(LELEM(OAKLEY_LIFE_DURATION) | LELEM(OAKLEY_LIFE_TYPE));

                switch (life_type)
                {
                case OAKLEY_LIFE_SECONDS:
                    if (val > OAKLEY_ISAKMP_SA_LIFETIME_MAXIMUM)
                    {
#ifdef CISCO_QUIRKS
                        plog("peer requested %lu seconds"
                                        " which exceeds our limit %d seconds"
                                        , (long) val
                                        , OAKLEY_ISAKMP_SA_LIFETIME_MAXIMUM);
                        plog("lifetime reduced to %d seconds "
                                        "(todo: IPSEC_RESPONDER_LIFETIME notification)"
                                        , OAKLEY_ISAKMP_SA_LIFETIME_MAXIMUM);
                        val = OAKLEY_ISAKMP_SA_LIFETIME_MAXIMUM;
#else
                        ugh = builddiag("peer requested %lu seconds"
                                        " which exceeds our limit %d seconds"
                                        , (long) val
                                        , OAKLEY_ISAKMP_SA_LIFETIME_MAXIMUM);
#endif
                    }   
                    ta.life_seconds = val;
                    break;
                case OAKLEY_LIFE_KILOBYTES:
                    ta.life_kilobytes = val;
                    break;
                default:
                    bad_case(life_type);
                }
                break;

            case OAKLEY_KEY_LENGTH | ISAKMP_ATTR_AF_TV:
                if ((seen_attrs & LELEM(OAKLEY_ENCRYPTION_ALGORITHM)) == 0)
                {
                    ugh = "OAKLEY_KEY_LENGTH attribute not preceded by "
                          "OAKLEY_ENCRYPTION_ALGORITHM attribute";
                    break;
                }
                if (ta.encrypter == NULL)
                {
                    ugh = "NULL encrypter with seen OAKLEY_ENCRYPTION_ALGORITHM";
                    break;
                }
                /*
                 * check if this keylen is compatible with specified algorithm
                 */
                if (val
                && (val < ta.encrypter->keyminlen || val > ta.encrypter->keymaxlen))
                {
                    ugh = "peer proposed key length not valid for "
                          "encryption algorithm specified";
                }
                ta.enckeylen = val;
                break;
#if 0 /* not yet supported */
            case OAKLEY_GROUP_TYPE | ISAKMP_ATTR_AF_TV:
            case OAKLEY_PRF | ISAKMP_ATTR_AF_TV:
            case OAKLEY_FIELD_SIZE | ISAKMP_ATTR_AF_TV:

            case OAKLEY_GROUP_PRIME | ISAKMP_ATTR_AF_TV:
            case OAKLEY_GROUP_PRIME | ISAKMP_ATTR_AF_TLV:
            case OAKLEY_GROUP_GENERATOR_ONE | ISAKMP_ATTR_AF_TV:
            case OAKLEY_GROUP_GENERATOR_ONE | ISAKMP_ATTR_AF_TLV:
            case OAKLEY_GROUP_GENERATOR_TWO | ISAKMP_ATTR_AF_TV:
            case OAKLEY_GROUP_GENERATOR_TWO | ISAKMP_ATTR_AF_TLV:
            case OAKLEY_GROUP_CURVE_A | ISAKMP_ATTR_AF_TV:
            case OAKLEY_GROUP_CURVE_A | ISAKMP_ATTR_AF_TLV:
            case OAKLEY_GROUP_CURVE_B | ISAKMP_ATTR_AF_TV:
            case OAKLEY_GROUP_CURVE_B | ISAKMP_ATTR_AF_TLV:
            case OAKLEY_GROUP_ORDER | ISAKMP_ATTR_AF_TV:
            case OAKLEY_GROUP_ORDER | ISAKMP_ATTR_AF_TLV:
#endif
            default:
                /* fix compiler warning */
                memset(&ta, 0, sizeof(ta));
                ugh = "unsupported OAKLEY attribute";
                break;
            }

            if (ugh != NULL)
            {
                loglog(RC_LOG_SERIOUS, "%s.  Attribute %s"
                    , ugh, enum_show(&oakley_attr_names, a.isaat_af_type));
                break;
            }
        }

        /*
         * ML: at last check for allowed transforms in alg_info_ike
         *     (ALG_INFO_F_STRICT flag)
         */
        if (ugh == NULL)
        {
            if (!ike_alg_ok_final(ta.encrypt, ta.enckeylen, ta.hash,
                ta.group ? ta.group->group : -1, c->alg_info_ike))
            {
                ugh = "OAKLEY proposal refused";
            }
        }

        if (ugh == NULL)
        {
            /* a little more checking is in order */
            {
                lset_t missing
                    = ~seen_attrs
                    & (LELEM(OAKLEY_ENCRYPTION_ALGORITHM)
                      | LELEM(OAKLEY_HASH_ALGORITHM)
                      | LELEM(OAKLEY_AUTHENTICATION_METHOD)
                      | LELEM(OAKLEY_GROUP_DESCRIPTION));

                if (missing)
                {
                    loglog(RC_LOG_SERIOUS, "missing mandatory attribute(s) %s in Oakley Transform %u"
                        , bitnamesof(oakley_attr_bit_names, missing)
                        , trans.isat_transnum);
                    return BAD_PROPOSAL_SYNTAX;
                }
            }
            /* We must have liked this transform.
             * Lets finish early and leave.
             */

            DBG(DBG_PARSING | DBG_CRYPT
                , DBG_log("Oakley Transform %u accepted", trans.isat_transnum));

            if (r_sa_pbs != NULL)
            {
                struct isakmp_proposal r_proposal = *proposal;
                pb_stream r_proposal_pbs;
                struct isakmp_transform r_trans = trans;
                pb_stream r_trans_pbs;

                /* Situation */
                if (!out_struct(&ipsecdoisit, &ipsec_sit_desc, r_sa_pbs, NULL))
                    impossible();

                /* Proposal */
#ifdef EMIT_ISAKMP_SPI
                r_proposal.isap_spisize = COOKIE_SIZE;
#else
                r_proposal.isap_spisize = 0;
#endif
                r_proposal.isap_notrans = 1;
                if (!out_struct(&r_proposal, &isakmp_proposal_desc, r_sa_pbs, &r_proposal_pbs))
                    impossible();

                /* SPI */
#ifdef EMIT_ISAKMP_SPI
                if (!out_raw(my_cookie, COOKIE_SIZE, &r_proposal_pbs, "SPI"))
                    impossible();
                r_proposal.isap_spisize = COOKIE_SIZE;
#else
                /* none (0) */
#endif

                /* Transform */
                r_trans.isat_np = ISAKMP_NEXT_NONE;
                if (!out_struct(&r_trans, &isakmp_isakmp_transform_desc, &r_proposal_pbs, &r_trans_pbs))
                    impossible();

                if (!out_raw(attr_start, attr_len, &r_trans_pbs, "attributes"))
                    impossible();
                close_output_pbs(&r_trans_pbs);
                close_output_pbs(&r_proposal_pbs);
                close_output_pbs(r_sa_pbs);
            }

            /* copy over the results */
            st->st_oakley = ta;
            return NOTHING_WRONG;
        }

        /* on to next transform */
        no_trans_left--;

        if (trans.isat_np == ISAKMP_NEXT_NONE)
        {
            if (no_trans_left != 0)
            {
                loglog(RC_LOG_SERIOUS, "number of Transform Payloads disagrees with Oakley Proposal Payload");
                return BAD_PROPOSAL_SYNTAX;
            }
            break;
        }
        if (trans.isat_np != ISAKMP_NEXT_T)
        {
            loglog(RC_LOG_SERIOUS, "unexpected %s payload in Oakley Proposal"
                , enum_show(&payload_names, proposal->isap_np));
            return BAD_PROPOSAL_SYNTAX;
        }
    }
    loglog(RC_LOG_SERIOUS, "no acceptable Oakley Transform");
    return NO_PROPOSAL_CHOSEN;
}

/* Parse the body of an IPsec SA Payload (i.e. Phase 2 / Quick Mode).
 *
 * The main routine is parse_ipsec_sa_body; other functions defined
 * between here and there are just helpers.
 *
 * Various shortcuts are taken.  In particular, the policy, such as
 * it is, is hardwired.
 *
 * If r_sa is non-NULL, the body of an SA representing the selected
 * proposal is emitted into it.
 *
 * If "selection" is true, the SA is supposed to represent the
 * single tranform that the peer has accepted.
 * ??? We only check that it is acceptable, not that it is one that we offered!
 *
 * Only IPsec DOI is accepted (what is the ISAKMP DOI?).
 * Error response is rudimentary.
 *
 * Since all ISAKMP groups in all SA Payloads must match, st->st_pfs_group
 * holds this across multiple payloads.
 * &unset_group signifies not yet "set"; NULL signifies NONE.
 *
 * This routine is used by quick_inI1_outR1() and quick_inR1_outI2().
 */

static const struct ipsec_trans_attrs null_ipsec_trans_attrs = {
    0,                                  /* transid (NULL, for now) */
    0,                                  /* spi */
    SA_LIFE_DURATION_DEFAULT,           /* life_seconds */
    SA_LIFE_DURATION_K_DEFAULT,         /* life_kilobytes */
    ENCAPSULATION_MODE_UNSPECIFIED,     /* encapsulation */
    AUTH_ALGORITHM_NONE,                /* auth */
    0,                                  /* key_len */
    0,                                  /* key_rounds */
};

static bool
parse_ipsec_transform(struct isakmp_transform *trans
, struct ipsec_trans_attrs *attrs
, pb_stream *prop_pbs
, pb_stream *trans_pbs
, struct_desc *trans_desc
, int previous_transnum /* or -1 if none */
, bool selection
, bool is_last
, bool is_ipcomp
, struct state *st)     /* current state object */
{
    lset_t seen_attrs = 0;
    lset_t seen_durations = 0;
    u_int16_t life_type = 0;
    const struct oakley_group_desc *pfs_group = NULL;

    if (!in_struct(trans, trans_desc, prop_pbs, trans_pbs))
        return FALSE;

    if (trans->isat_transnum <= previous_transnum)
    {
        loglog(RC_LOG_SERIOUS, "Transform Numbers in Proposal are not monotonically increasing");
        return FALSE;
    }

    switch (trans->isat_np)
    {
        case ISAKMP_NEXT_T:
            if (is_last)
            {
                loglog(RC_LOG_SERIOUS, "Proposal Payload has more Transforms than specified");
                return FALSE;
            }
            break;
        case ISAKMP_NEXT_NONE:
            if (!is_last)
            {
                loglog(RC_LOG_SERIOUS, "Proposal Payload has fewer Transforms than specified");
                return FALSE;
            }
            break;
        default:
            loglog(RC_LOG_SERIOUS, "expecting Transform Payload, but found %s in Proposal"
                , enum_show(&payload_names, trans->isat_np));
            return FALSE;
    }

    *attrs = null_ipsec_trans_attrs;
    attrs->transid = trans->isat_transid;

    while (pbs_left(trans_pbs) != 0)
    {
        struct isakmp_attribute a;
        pb_stream attr_pbs;
        enum_names *vdesc;
        u_int32_t val;  /* room for larger value */
        bool ipcomp_inappropriate = is_ipcomp;  /* will get reset if OK */

        if (!in_struct(&a, &isakmp_ipsec_attribute_desc, trans_pbs, &attr_pbs))
            return FALSE;

        passert((a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK) < 32);

        if (LHAS(seen_attrs, a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK))
        {
            loglog(RC_LOG_SERIOUS, "repeated %s attribute in IPsec Transform %u"
                , enum_show(&ipsec_attr_names, a.isaat_af_type)
                , trans->isat_transnum);
            return FALSE;
        }

        seen_attrs |= LELEM(a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK);

        val = a.isaat_lv;

        vdesc  = ipsec_attr_val_descs[a.isaat_af_type & ISAKMP_ATTR_RTYPE_MASK];
        if (vdesc != NULL)
        {
            if (enum_name(vdesc, val) == NULL)
            {
                loglog(RC_LOG_SERIOUS, "invalid value %u for attribute %s in IPsec Transform"
                    , (unsigned)val, enum_show(&ipsec_attr_names, a.isaat_af_type));
                return FALSE;
            }
            DBG(DBG_PARSING
                , if ((a.isaat_af_type & ISAKMP_ATTR_AF_MASK) == ISAKMP_ATTR_AF_TV)
                    DBG_log("   [%u is %s]"
                        , (unsigned)val, enum_show(vdesc, val)));
        }

        switch (a.isaat_af_type)
        {
            case SA_LIFE_TYPE | ISAKMP_ATTR_AF_TV:
                ipcomp_inappropriate = FALSE;
                if (LHAS(seen_durations, val))
                {
                    loglog(RC_LOG_SERIOUS, "attribute SA_LIFE_TYPE value %s repeated in message"
                        , enum_show(&sa_lifetime_names, val));
                    return FALSE;
                }
                seen_durations |= LELEM(val);
                life_type = val;
                break;
            case SA_LIFE_DURATION | ISAKMP_ATTR_AF_TLV:
                val = decode_long_duration(&attr_pbs);
                /* fall through */
            case SA_LIFE_DURATION | ISAKMP_ATTR_AF_TV:
                ipcomp_inappropriate = FALSE;
                if (!LHAS(seen_attrs, SA_LIFE_DURATION))
                {
                    loglog(RC_LOG_SERIOUS, "SA_LIFE_DURATION IPsec attribute not preceded by SA_LIFE_TYPE attribute");
                    return FALSE;
                }
                seen_attrs &= ~(LELEM(SA_LIFE_DURATION) | LELEM(SA_LIFE_TYPE));

                switch (life_type)
                {
                    case SA_LIFE_TYPE_SECONDS:
                        /* silently limit duration to our maximum */
                        attrs->life_seconds = val <= SA_LIFE_DURATION_MAXIMUM
                            ? val : SA_LIFE_DURATION_MAXIMUM;
                        break;
                    case SA_LIFE_TYPE_KBYTES:
                        attrs->life_kilobytes = val;
                        break;
                    default:
                        bad_case(life_type);
                }
                break;
            case GROUP_DESCRIPTION | ISAKMP_ATTR_AF_TV:
                if (is_ipcomp)
                {
                    /* Accept reluctantly.  Should not happen, according to
                     * draft-shacham-ippcp-rfc2393bis-05.txt 4.1.
                     */
                    ipcomp_inappropriate = FALSE;
                    loglog(RC_COMMENT
                        , "IPCA (IPcomp SA) contains GROUP_DESCRIPTION."
                        "  Ignoring inapproprate attribute.");
                }
                pfs_group = lookup_group(val);
                if (pfs_group == NULL)
                {
                    loglog(RC_LOG_SERIOUS, "only OAKLEY_GROUP_MODP1024 and OAKLEY_GROUP_MODP1536 supported for PFS");
                    return FALSE;
                }
                break;
            case ENCAPSULATION_MODE | ISAKMP_ATTR_AF_TV:
                ipcomp_inappropriate = FALSE;
                switch (val)
                {
                case ENCAPSULATION_MODE_TUNNEL:
                case ENCAPSULATION_MODE_TRANSPORT:
                    if (st->nat_traversal & NAT_T_DETECTED)
                    {
                        loglog(RC_LOG_SERIOUS
                            , "%s must only be used if NAT-Traversal is not detected"
                            , enum_name(&enc_mode_names, val));
                        /*
                         * Accept it anyway because SSH-Sentinel does not
                         * use UDP_TUNNEL or UDP_TRANSPORT for the diagnostic.
                         *
                         * remove when SSH-Sentinel is fixed
                         */
#ifdef I_DONT_CARE_OF_SSH_SENTINEL
                        return FALSE;
#endif
                    }
                    attrs->encapsulation = val;
                    break;
                case ENCAPSULATION_MODE_UDP_TRANSPORT_DRAFTS:
#ifndef I_KNOW_TRANSPORT_MODE_HAS_SECURITY_CONCERN_BUT_I_WANT_IT
                    loglog(RC_LOG_SERIOUS
                        , "NAT-Traversal: Transport mode disabled due to security concerns");
                    return FALSE;
#endif
                case ENCAPSULATION_MODE_UDP_TUNNEL_DRAFTS:
                    if (st->nat_traversal & NAT_T_WITH_RFC_VALUES)
                    {
                        loglog(RC_LOG_SERIOUS
                            , "%s must only be used with old IETF drafts"
                            , enum_name(&enc_mode_names, val));
                        return FALSE;
                    }
                    else if (st->nat_traversal & NAT_T_DETECTED)
                    {
                        attrs->encapsulation = val
                                - ENCAPSULATION_MODE_UDP_TUNNEL_DRAFTS
                                + ENCAPSULATION_MODE_TUNNEL;
                    }
                    else
                    {
                        loglog(RC_LOG_SERIOUS
                            , "%s must only be used if NAT-Traversal is detected"
                            , enum_name(&enc_mode_names, val));
                        return FALSE;
                    }
                    break;
                    case ENCAPSULATION_MODE_UDP_TRANSPORT_RFC:
#ifndef I_KNOW_TRANSPORT_MODE_HAS_SECURITY_CONCERN_BUT_I_WANT_IT
                        loglog(RC_LOG_SERIOUS
                            , "NAT-Traversal: Transport mode disabled due "
                              "to security concerns");
                        return FALSE;
#endif
                    case ENCAPSULATION_MODE_UDP_TUNNEL_RFC:
                        if ((st->nat_traversal & NAT_T_DETECTED)
                        && (st->nat_traversal & NAT_T_WITH_RFC_VALUES))
                        {
                            attrs->encapsulation = val
                                        - ENCAPSULATION_MODE_UDP_TUNNEL_RFC
                                        + ENCAPSULATION_MODE_TUNNEL;
                        }
                        else if (st->nat_traversal & NAT_T_DETECTED)
                        {
                            loglog(RC_LOG_SERIOUS
                                , "%s must only be used with NAT-T RFC"
                                , enum_name(&enc_mode_names, val));
                            return FALSE;
                        }
                        else
                        {
                            loglog(RC_LOG_SERIOUS
                                , "%s must only be used if NAT-Traversal is detected"
                                , enum_name(&enc_mode_names, val));
                            return FALSE;
                        }
                        break;
                    default:
                        loglog(RC_LOG_SERIOUS
                            , "unknown ENCAPSULATION_MODE %d in IPSec SA", val);
                        return FALSE;
                }
                break;
            case AUTH_ALGORITHM | ISAKMP_ATTR_AF_TV:
                attrs->auth = val;
                break;
            case KEY_LENGTH | ISAKMP_ATTR_AF_TV:
                attrs->key_len = val;
                break;
            case KEY_ROUNDS | ISAKMP_ATTR_AF_TV:
                attrs->key_rounds = val;
                break;
#if 0 /* not yet implemented */
            case COMPRESS_DICT_SIZE | ISAKMP_ATTR_AF_TV:
                break;
            case COMPRESS_PRIVATE_ALG | ISAKMP_ATTR_AF_TV:
                break;

            case SA_LIFE_DURATION | ISAKMP_ATTR_AF_TLV:
                break;
            case COMPRESS_PRIVATE_ALG | ISAKMP_ATTR_AF_TLV:
                break;
#endif
            default:
                loglog(RC_LOG_SERIOUS, "unsupported IPsec attribute %s"
                    , enum_show(&ipsec_attr_names, a.isaat_af_type));
                return FALSE;
        }
        if (ipcomp_inappropriate)
        {
            loglog(RC_LOG_SERIOUS, "IPsec attribute %s inappropriate for IPCOMP"
                , enum_show(&ipsec_attr_names, a.isaat_af_type));
            return FALSE;
        }
    }

    /* Although an IPCOMP SA (IPCA) ought not to have a pfs_group,
     * if it does, demand that it be consistent.
     * See draft-shacham-ippcp-rfc2393bis-05.txt 4.1.
     */
    if (!is_ipcomp || pfs_group != NULL)
    {
        if (st->st_pfs_group == &unset_group)
            st->st_pfs_group = pfs_group;

        if (st->st_pfs_group != pfs_group)
        {
            loglog(RC_LOG_SERIOUS, "GROUP_DESCRIPTION inconsistent with that of %s in IPsec SA"
                , selection? "the Proposal" : "a previous Transform");
            return FALSE;
        }
    }

    if (LHAS(seen_attrs, SA_LIFE_DURATION))
    {
        loglog(RC_LOG_SERIOUS, "SA_LIFE_TYPE IPsec attribute not followed by SA_LIFE_DURATION attribute in message");
        return FALSE;
    }

    if (!LHAS(seen_attrs, ENCAPSULATION_MODE))
    {
        if (is_ipcomp)
        {
            /* draft-shacham-ippcp-rfc2393bis-05.txt 4.1:
             * "If the Encapsulation Mode is unspecified,
             * the default value of Transport Mode is assumed."
             * This contradicts/overrides the DOI (quuoted below).
             */
            attrs->encapsulation = ENCAPSULATION_MODE_TRANSPORT;
        }
        else
        {
            /* ??? Technically, RFC 2407 (IPSEC DOI) 4.5 specifies that
             * the default is "unspecified (host-dependent)".
             * This makes little sense, so we demand that it be specified.
             */
            loglog(RC_LOG_SERIOUS, "IPsec Transform must specify ENCAPSULATION_MODE");
            return FALSE;
        }
    }

    /* ??? should check for key_len and/or key_rounds if required */

    return TRUE;
}

static void
echo_proposal(
    struct isakmp_proposal r_proposal,  /* proposal to emit */
    struct isakmp_transform r_trans,    /* winning transformation within it */
    u_int8_t np,                        /* Next Payload for proposal */
    pb_stream *r_sa_pbs,                /* SA PBS into which to emit */
    struct ipsec_proto_info *pi,        /* info about this protocol instance */
    struct_desc *trans_desc,            /* descriptor for this transformation */
    pb_stream *trans_pbs,               /* PBS for incoming transform */
    struct spd_route *sr,               /* host details for the association */
    bool tunnel_mode)                   /* true for inner most tunnel SA */
{
    pb_stream r_proposal_pbs;
    pb_stream r_trans_pbs;

    /* Proposal */
    r_proposal.isap_np = np;
    r_proposal.isap_notrans = 1;
    if (!out_struct(&r_proposal, &isakmp_proposal_desc, r_sa_pbs, &r_proposal_pbs))
        impossible();

    /* allocate and emit our CPI/SPI */
    if (r_proposal.isap_protoid == PROTO_IPCOMP)
    {
        /* CPI is stored in network low order end of an
         * ipsec_spi_t.  So we start a couple of bytes in.
         * Note: we may fail to generate a satisfactory CPI,
         * but we'll ignore that.
         */
        pi->our_spi = get_my_cpi(sr, tunnel_mode);
        out_raw((u_char *) &pi->our_spi
             + IPSEC_DOI_SPI_SIZE - IPCOMP_CPI_SIZE
            , IPCOMP_CPI_SIZE
            , &r_proposal_pbs, "CPI");
    }
    else
    {
        pi->our_spi = get_ipsec_spi(pi->attrs.spi
            , r_proposal.isap_protoid == PROTO_IPSEC_AH ?
                IPPROTO_AH : IPPROTO_ESP
            , sr
            , tunnel_mode);
        /* XXX should check for errors */
        out_raw((u_char *) &pi->our_spi, IPSEC_DOI_SPI_SIZE
            , &r_proposal_pbs, "SPI");
    }

    /* Transform */
    r_trans.isat_np = ISAKMP_NEXT_NONE;
    if (!out_struct(&r_trans, trans_desc, &r_proposal_pbs, &r_trans_pbs))
        impossible();

    /* Transform Attributes: pure echo */
    trans_pbs->cur = trans_pbs->start + sizeof(struct isakmp_transform);
    if (!out_raw(trans_pbs->cur, pbs_left(trans_pbs)
    , &r_trans_pbs, "attributes"))
        impossible();

    close_output_pbs(&r_trans_pbs);
    close_output_pbs(&r_proposal_pbs);
}

notification_t
parse_ipsec_sa_body(
    pb_stream *sa_pbs,          /* body of input SA Payload */
    const struct isakmp_sa *sa, /* header of input SA Payload */
    pb_stream *r_sa_pbs,        /* if non-NULL, where to emit body of winning SA */
    bool selection,             /* if this SA is a selection, only one transform may appear */
    struct state *st)           /* current state object */
{
    const struct connection *c = st->st_connection;
    u_int32_t ipsecdoisit;
    pb_stream next_proposal_pbs;

    struct isakmp_proposal next_proposal;
    ipsec_spi_t next_spi;

    bool next_full = TRUE;

    /* DOI */
    if (sa->isasa_doi != ISAKMP_DOI_IPSEC)
    {
        loglog(RC_LOG_SERIOUS, "Unknown or unsupported DOI %s", enum_show(&doi_names, sa->isasa_doi));
        /* XXX Could send notification back */
        return DOI_NOT_SUPPORTED;
    }

    /* Situation */
    if (!in_struct(&ipsecdoisit, &ipsec_sit_desc, sa_pbs, NULL))
        return SITUATION_NOT_SUPPORTED;

    if (ipsecdoisit != SIT_IDENTITY_ONLY)
    {
        loglog(RC_LOG_SERIOUS, "unsupported IPsec DOI situation (%s)"
            , bitnamesof(sit_bit_names, ipsecdoisit));
        /* XXX Could send notification back */
        return SITUATION_NOT_SUPPORTED;
    }

    /* The rules for IPsec SAs are scattered.
     * RFC 2408 "ISAKMP" section 4.2 gives some info.
     * There may be multiple proposals.  Those with identical proposal
     * numbers must be considered as conjuncts.  Those with different
     * numbers are disjuncts.
     * Each proposal may have several transforms, each considered
     * an alternative.
     * Each transform may have several attributes, all applying.
     *
     * To handle the way proposals are combined, we need to do a
     * look-ahead.
     */

    if (!in_struct(&next_proposal, &isakmp_proposal_desc, sa_pbs, &next_proposal_pbs))
        return BAD_PROPOSAL_SYNTAX;

    /* for each conjunction of proposals... */
    while (next_full)
    {
        int propno = next_proposal.isap_proposal;
        pb_stream ah_prop_pbs, esp_prop_pbs, ipcomp_prop_pbs;
        struct isakmp_proposal ah_proposal = {0, 0, 0, 0, 0, 0, 0};
        struct isakmp_proposal esp_proposal = {0, 0, 0, 0, 0, 0, 0};
        struct isakmp_proposal ipcomp_proposal = {0, 0, 0, 0, 0, 0, 0};
        ipsec_spi_t ah_spi = 0;
        ipsec_spi_t esp_spi = 0;
        ipsec_spi_t ipcomp_cpi = 0;
        bool ah_seen = FALSE;
        bool esp_seen = FALSE;
        bool ipcomp_seen = FALSE;
        bool tunnel_mode = FALSE;
        int inner_proto = 0;
        u_int16_t well_known_cpi = 0;

        pb_stream ah_trans_pbs, esp_trans_pbs, ipcomp_trans_pbs;
        struct isakmp_transform ah_trans, esp_trans, ipcomp_trans;
        struct ipsec_trans_attrs ah_attrs, esp_attrs, ipcomp_attrs;

        /* for each proposal in the conjunction */
        do {

            if (next_proposal.isap_protoid == PROTO_IPCOMP)
            {
                /* IPCOMP CPI */
                if (next_proposal.isap_spisize == IPSEC_DOI_SPI_SIZE)
                {
                    /* This code is to accommodate those peculiar
                     * implementations that send a CPI in the bottom of an
                     * SPI-sized field.
                     * See draft-shacham-ippcp-rfc2393bis-05.txt 4.1
                     */
                    u_int8_t filler[IPSEC_DOI_SPI_SIZE - IPCOMP_CPI_SIZE];

                    if (!in_raw(filler, sizeof(filler)
                     , &next_proposal_pbs, "CPI filler")
                    || !all_zero(filler, sizeof(filler)))
                        return INVALID_SPI;
                }
                else if (next_proposal.isap_spisize != IPCOMP_CPI_SIZE)
                {
                    loglog(RC_LOG_SERIOUS, "IPsec Proposal with improper CPI size (%u)"
                        , next_proposal.isap_spisize);
                    return INVALID_SPI;
                }

                /* We store CPI in the low order of a network order
                 * ipsec_spi_t.  So we start a couple of bytes in.
                 */
                zero(&next_spi);
                if (!in_raw((u_char *)&next_spi
                  + IPSEC_DOI_SPI_SIZE - IPCOMP_CPI_SIZE
                , IPCOMP_CPI_SIZE, &next_proposal_pbs, "CPI"))
                    return INVALID_SPI;

                /* If sanity ruled, CPIs would have to be such that
                 * the SAID (the triple (CPI, IPCOM, destination IP))
                 * would be unique, just like for SPIs.  But there is a
                 * perversion where CPIs can be well-known and consequently
                 * the triple is not unique.  We hide this fact from
                 * ourselves by fudging the top 16 bits to make
                 * the property true internally!
                 */
                switch (ntohl(next_spi))
                {
                case IPCOMP_DEFLATE:
                    well_known_cpi = ntohl(next_spi);
                    next_spi = uniquify_his_cpi(next_spi, st);
                    if (next_spi == 0)
                    {
                        loglog(RC_LOG_SERIOUS
                            , "IPsec Proposal contains well-known CPI that I cannot uniquify");
                        return INVALID_SPI;
                    }
                    break;
                default:
                    if (ntohl(next_spi) < IPCOMP_FIRST_NEGOTIATED
                    || ntohl(next_spi) > IPCOMP_LAST_NEGOTIATED)
                    {
                        loglog(RC_LOG_SERIOUS, "IPsec Proposal contains CPI from non-negotiated range (0x%lx)"
                            , (unsigned long) ntohl(next_spi));
                        return INVALID_SPI;
                    }
                    break;
                }
            }
            else
            {
                /* AH or ESP SPI */
                if (next_proposal.isap_spisize != IPSEC_DOI_SPI_SIZE)
                {
                    loglog(RC_LOG_SERIOUS, "IPsec Proposal with improper SPI size (%u)"
                        , next_proposal.isap_spisize);
                    return INVALID_SPI;
                }

                if (!in_raw((u_char *)&next_spi, sizeof(next_spi), &next_proposal_pbs, "SPI"))
                    return INVALID_SPI;

                /* SPI value 0 is invalid and values 1-255 are reserved to IANA.
                 * RFC 2402 (ESP) 2.4, RFC 2406 (AH) 2.1
                 * IPCOMP???
                 */
                if (ntohl(next_spi) < IPSEC_DOI_SPI_MIN)
                {
                    loglog(RC_LOG_SERIOUS, "IPsec Proposal contains invalid SPI (0x%lx)"
                        , (unsigned long) ntohl(next_spi));
                    return INVALID_SPI;
                }
            }

            if (next_proposal.isap_notrans == 0)
            {
                loglog(RC_LOG_SERIOUS, "IPsec Proposal contains no Transforms");
                return BAD_PROPOSAL_SYNTAX;
            }

            switch (next_proposal.isap_protoid)
            {
            case PROTO_IPSEC_AH:
                if (ah_seen)
                {
                    loglog(RC_LOG_SERIOUS, "IPsec SA contains two simultaneous AH Proposals");
                    return BAD_PROPOSAL_SYNTAX;
                }
                ah_seen = TRUE;
                ah_prop_pbs = next_proposal_pbs;
                ah_proposal = next_proposal;
                ah_spi = next_spi;
                break;

            case PROTO_IPSEC_ESP:
                if (esp_seen)
                {
                    loglog(RC_LOG_SERIOUS, "IPsec SA contains two simultaneous ESP Proposals");
                    return BAD_PROPOSAL_SYNTAX;
                }
                esp_seen = TRUE;
                esp_prop_pbs = next_proposal_pbs;
                esp_proposal = next_proposal;
                esp_spi = next_spi;
                break;

            case PROTO_IPCOMP:
                if (ipcomp_seen)
                {
                    loglog(RC_LOG_SERIOUS, "IPsec SA contains two simultaneous IPCOMP Proposals");
                    return BAD_PROPOSAL_SYNTAX;
                }
                ipcomp_seen = TRUE;
                ipcomp_prop_pbs = next_proposal_pbs;
                ipcomp_proposal = next_proposal;
                ipcomp_cpi = next_spi;
                break;

            default:
                loglog(RC_LOG_SERIOUS, "unexpected Protocol ID (%s) in IPsec Proposal"
                    , enum_show(&protocol_names, next_proposal.isap_protoid));
                return INVALID_PROTOCOL_ID;
            }

            /* refill next_proposal */
            if (next_proposal.isap_np == ISAKMP_NEXT_NONE)
            {
                next_full = FALSE;
                break;
            }
            else if (next_proposal.isap_np != ISAKMP_NEXT_P)
            {
                loglog(RC_LOG_SERIOUS, "unexpected in Proposal: %s"
                    , enum_show(&payload_names, next_proposal.isap_np));
                return BAD_PROPOSAL_SYNTAX;
            }

            if (!in_struct(&next_proposal, &isakmp_proposal_desc, sa_pbs, &next_proposal_pbs))
                return BAD_PROPOSAL_SYNTAX;
        } while (next_proposal.isap_proposal == propno);

        /* Now that we have all conjuncts, we should try
         * the Cartesian product of eachs tranforms!
         * At the moment, we take short-cuts on account of
         * our rudimentary hard-wired policy.
         * For now, we find an acceptable AH (if any)
         * and then an acceptable ESP.  The only interaction
         * is that the ESP acceptance can know whether there
         * was an acceptable AH and hence not require an AUTH.
         */

        if (ah_seen)
        {
            int previous_transnum = -1;
            int tn;

            for (tn = 0; tn != ah_proposal.isap_notrans; tn++)
            {
                int ok_transid = 0;
                bool ok_auth = FALSE;

                if (!parse_ipsec_transform(&ah_trans
                , &ah_attrs
                , &ah_prop_pbs
                , &ah_trans_pbs
                , &isakmp_ah_transform_desc
                , previous_transnum
                , selection
                , tn == ah_proposal.isap_notrans - 1
                , FALSE
                , st))
                    return BAD_PROPOSAL_SYNTAX;

                previous_transnum = ah_trans.isat_transnum;

                /* we must understand ah_attrs.transid
                 * COMBINED with ah_attrs.auth.
                 * See RFC 2407 "IPsec DOI" section 4.4.3
                 * The following combinations are legal,
                 * but we don't implement all of them:
                 * It seems as if each auth algorithm
                 * only applies to one ah transid.
                 * AH_MD5, AUTH_ALGORITHM_HMAC_MD5
                 * AH_MD5, AUTH_ALGORITHM_KPDK (unimplemented)
                 * AH_SHA, AUTH_ALGORITHM_HMAC_SHA1
                 * AH_DES, AUTH_ALGORITHM_DES_MAC (unimplemented)
                 */
                switch (ah_attrs.auth)
                {
                    case AUTH_ALGORITHM_NONE:
                        loglog(RC_LOG_SERIOUS, "AUTH_ALGORITHM attribute missing in AH Transform");
                        return BAD_PROPOSAL_SYNTAX;

                    case AUTH_ALGORITHM_HMAC_MD5:
                        ok_auth = TRUE;
                        /* fall through */
                    case AUTH_ALGORITHM_KPDK:
                        ok_transid = AH_MD5;
                        break;

                    case AUTH_ALGORITHM_HMAC_SHA1:
                        ok_auth = TRUE;
                        ok_transid = AH_SHA;
                        break;

                    case AUTH_ALGORITHM_DES_MAC:
                        ok_transid = AH_DES;
                        break;
                }
                if (ah_attrs.transid != ok_transid)
                {
                    loglog(RC_LOG_SERIOUS, "%s attribute inappropriate in %s Transform"
                        , enum_name(&auth_alg_names, ah_attrs.auth)
                        , enum_show(&ah_transformid_names, ah_attrs.transid));
                    return BAD_PROPOSAL_SYNTAX;
                }
                if (!ok_auth)
                {
                    DBG(DBG_CONTROL | DBG_CRYPT
                        , DBG_log("%s attribute unsupported"
                            " in %s Transform from %s"
                            , enum_name(&auth_alg_names, ah_attrs.auth)
                            , enum_show(&ah_transformid_names, ah_attrs.transid)
                            , ip_str(&c->spd.that.host_addr)));
                    continue;   /* try another */
                }
                break;  /* we seem to be happy */
            }
            if (tn == ah_proposal.isap_notrans)
                continue;       /* we didn't find a nice one */
            ah_attrs.spi = ah_spi;
            inner_proto = IPPROTO_AH;
            if (ah_attrs.encapsulation == ENCAPSULATION_MODE_TUNNEL)
                tunnel_mode = TRUE;
        }

        if (esp_seen)
        {
            int previous_transnum = -1;
            int tn;

            for (tn = 0; tn != esp_proposal.isap_notrans; tn++)
            {
                if (!parse_ipsec_transform(&esp_trans
                , &esp_attrs
                , &esp_prop_pbs
                , &esp_trans_pbs
                , &isakmp_esp_transform_desc
                , previous_transnum
                , selection
                , tn == esp_proposal.isap_notrans - 1
                , FALSE
                , st))
                    return BAD_PROPOSAL_SYNTAX;

                previous_transnum = esp_trans.isat_transnum;

                /* set default key length for AES encryption */
                if (!esp_attrs.key_len && esp_attrs.transid == ESP_AES)
                {
                    esp_attrs.key_len = 128 / BITS_PER_BYTE;
                }

                if (!kernel_alg_esp_enc_ok(esp_attrs.transid, esp_attrs.key_len
                    ,c->alg_info_esp))
                {
                    switch (esp_attrs.transid)
                    {
                    case ESP_3DES:
                        break;
#ifdef SUPPORT_ESP_NULL /* should be about as secure as AH-only */
                    case ESP_NULL:
                        if (esp_attrs.auth == AUTH_ALGORITHM_NONE)
                        {
                            loglog(RC_LOG_SERIOUS, "ESP_NULL requires auth algorithm");
                            return BAD_PROPOSAL_SYNTAX;
                        }
                        if (st->st_policy & POLICY_ENCRYPT)
                        {
                            DBG(DBG_CONTROL | DBG_CRYPT
                                    , DBG_log("ESP_NULL Transform Proposal from %s"
                                        " does not satisfy POLICY_ENCRYPT"
                                        , ip_str(&c->spd.that.host_addr)));
                            continue;   /* try another */
                        }
                        break;
#endif
                    default:
                        DBG(DBG_CONTROL | DBG_CRYPT
                            , DBG_log("unsupported ESP Transform %s from %s"
                                , enum_show(&esp_transformid_names, esp_attrs.transid)
                                , ip_str(&c->spd.that.host_addr)));
                        continue;   /* try another */
                    }
                }

                if (!kernel_alg_esp_auth_ok(esp_attrs.auth, c->alg_info_esp))
                {
                    switch (esp_attrs.auth)
                    {
                    case AUTH_ALGORITHM_NONE:
                        if (!ah_seen)
                        {
                            DBG(DBG_CONTROL | DBG_CRYPT
                                , DBG_log("ESP from %s must either have AUTH or be combined with AH"
                                    , ip_str(&c->spd.that.host_addr)));
                            continue;   /* try another */
                        }
                        break;
                    case AUTH_ALGORITHM_HMAC_MD5:
                    case AUTH_ALGORITHM_HMAC_SHA1:
                        break;
                    default:
                        DBG(DBG_CONTROL | DBG_CRYPT
                            , DBG_log("unsupported ESP auth alg %s from %s"
                                , enum_show(&auth_alg_names, esp_attrs.auth)
                                , ip_str(&c->spd.that.host_addr)));
                        continue;   /* try another */
                    }
                }

                /* A last check for allowed transforms in alg_info_esp
                 * (ALG_INFO_F_STRICT flag)
                 */
                if (!kernel_alg_esp_ok_final(esp_attrs.transid, esp_attrs.key_len
                    ,esp_attrs.auth, c->alg_info_esp))
                {
                    continue;
                }

                if (ah_seen && ah_attrs.encapsulation != esp_attrs.encapsulation)
                {
                    /* ??? This should be an error, but is it? */
                    DBG(DBG_CONTROL | DBG_CRYPT
                        , DBG_log("AH and ESP transforms disagree about encapsulation; TUNNEL presumed"));
                }

                break;  /* we seem to be happy */
            }
            if (tn == esp_proposal.isap_notrans)
                continue;       /* we didn't find a nice one */
            
            esp_attrs.spi = esp_spi;
            inner_proto = IPPROTO_ESP;
            if (esp_attrs.encapsulation == ENCAPSULATION_MODE_TUNNEL)
                tunnel_mode = TRUE;
        }
        else if (st->st_policy & POLICY_ENCRYPT)
        {
            DBG(DBG_CONTROL | DBG_CRYPT
                , DBG_log("policy for \"%s\" requires encryption but ESP not in Proposal from %s"
                    , c->name, ip_str(&c->spd.that.host_addr)));
            continue;   /* we needed encryption, but didn't find ESP */
        }
        else if ((st->st_policy & POLICY_AUTHENTICATE) && !ah_seen)
        {
            DBG(DBG_CONTROL | DBG_CRYPT
                , DBG_log("policy for \"%s\" requires authentication"
                    " but none in Proposal from %s"
                    , c->name, ip_str(&c->spd.that.host_addr)));
            continue;   /* we need authentication, but we found neither ESP nor AH */
        }

        if (ipcomp_seen)
        {
            int previous_transnum = -1;
            int tn;

#ifdef NEVER    /* we think IPcomp is working now */
            /**** FUDGE TO PREVENT UNREQUESTED IPCOMP:
             **** NEEDED BECAUSE OUR IPCOMP IS EXPERIMENTAL (UNSTABLE).
             ****/
            if (!(st->st_policy & POLICY_COMPRESS))
            {
                plog("compression proposed by %s, but policy for \"%s\" forbids it"
                    , ip_str(&c->spd.that.host_addr), c->name);
                continue;       /* unwanted compression proposal */
            }
#endif
            if (!can_do_IPcomp)
            {
                plog("compression proposed by %s, but KLIPS is not configured with IPCOMP"
                    , ip_str(&c->spd.that.host_addr));
                continue;
            }

            if (well_known_cpi != 0 && !ah_seen && !esp_seen)
            {
                plog("illegal proposal: bare IPCOMP used with well-known CPI");
                return BAD_PROPOSAL_SYNTAX;
            }

            for (tn = 0; tn != ipcomp_proposal.isap_notrans; tn++)
            {
                if (!parse_ipsec_transform(&ipcomp_trans
                , &ipcomp_attrs
                , &ipcomp_prop_pbs
                , &ipcomp_trans_pbs
                , &isakmp_ipcomp_transform_desc
                , previous_transnum
                , selection
                , tn == ipcomp_proposal.isap_notrans - 1
                , TRUE
                , st))
                    return BAD_PROPOSAL_SYNTAX;

                previous_transnum = ipcomp_trans.isat_transnum;

                if (well_known_cpi != 0 && ipcomp_attrs.transid != well_known_cpi)
                {
                    plog("illegal proposal: IPCOMP well-known CPI disagrees with transform");
                    return BAD_PROPOSAL_SYNTAX;
                }

                switch (ipcomp_attrs.transid)
                {
                    case IPCOMP_DEFLATE:    /* all we can handle! */
                        break;

                    default:
                        DBG(DBG_CONTROL | DBG_CRYPT
                            , DBG_log("unsupported IPCOMP Transform %s from %s"
                                , enum_show(&ipcomp_transformid_names, ipcomp_attrs.transid)
                                , ip_str(&c->spd.that.host_addr)));
                        continue;   /* try another */
                }

                if (ah_seen && ah_attrs.encapsulation != ipcomp_attrs.encapsulation)
                {
                    /* ??? This should be an error, but is it? */
                    DBG(DBG_CONTROL | DBG_CRYPT
                        , DBG_log("AH and IPCOMP transforms disagree about encapsulation; TUNNEL presumed"));
                } else if (esp_seen && esp_attrs.encapsulation != ipcomp_attrs.encapsulation)
                {
                    /* ??? This should be an error, but is it? */
                    DBG(DBG_CONTROL | DBG_CRYPT
                        , DBG_log("ESP and IPCOMP transforms disagree about encapsulation; TUNNEL presumed"));
                }

                break;  /* we seem to be happy */
            }
            if (tn == ipcomp_proposal.isap_notrans)
                continue;       /* we didn't find a nice one */
            ipcomp_attrs.spi = ipcomp_cpi;
            inner_proto = IPPROTO_COMP;
            if (ipcomp_attrs.encapsulation == ENCAPSULATION_MODE_TUNNEL)
                tunnel_mode = TRUE;
        }

        /* Eureka: we liked what we saw -- accept it. */

        if (r_sa_pbs != NULL)
        {
            /* emit what we've accepted */

            /* Situation */
            if (!out_struct(&ipsecdoisit, &ipsec_sit_desc, r_sa_pbs, NULL))
                impossible();

            /* AH proposal */
            if (ah_seen)
                echo_proposal(ah_proposal
                    , ah_trans
                    , esp_seen || ipcomp_seen? ISAKMP_NEXT_P : ISAKMP_NEXT_NONE
                    , r_sa_pbs
                    , &st->st_ah
                    , &isakmp_ah_transform_desc
                    , &ah_trans_pbs
                    , &st->st_connection->spd
                    , tunnel_mode && inner_proto == IPPROTO_AH);

            /* ESP proposal */
            if (esp_seen)
                echo_proposal(esp_proposal
                    , esp_trans
                    , ipcomp_seen? ISAKMP_NEXT_P : ISAKMP_NEXT_NONE
                    , r_sa_pbs
                    , &st->st_esp
                    , &isakmp_esp_transform_desc
                    , &esp_trans_pbs
                    , &st->st_connection->spd
                    , tunnel_mode && inner_proto == IPPROTO_ESP);

            /* IPCOMP proposal */
            if (ipcomp_seen)
                echo_proposal(ipcomp_proposal
                    , ipcomp_trans
                    , ISAKMP_NEXT_NONE
                    , r_sa_pbs
                    , &st->st_ipcomp
                    , &isakmp_ipcomp_transform_desc
                    , &ipcomp_trans_pbs
                    , &st->st_connection->spd
                    , tunnel_mode && inner_proto == IPPROTO_COMP);

            close_output_pbs(r_sa_pbs);
        }

        /* save decoded version of winning SA in state */

        st->st_ah.present = ah_seen;
        if (ah_seen)
            st->st_ah.attrs = ah_attrs;

        st->st_esp.present = esp_seen;
        if (esp_seen)
            st->st_esp.attrs = esp_attrs;

        st->st_ipcomp.present = ipcomp_seen;
        if (ipcomp_seen)
            st->st_ipcomp.attrs = ipcomp_attrs;

        return NOTHING_WRONG;
    }

    loglog(RC_LOG_SERIOUS, "no acceptable Proposal in IPsec SA");
    return NO_PROPOSAL_CHOSEN;
}