/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 *      context_establish.c
 *
 * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 */

#include <string.h>
#include "dh_gssapi.h"

/*
 * The following 2 routines convert a gss_channel_binding to a DH
 * channel_binding and vis versa.  We can no longer assume a simple
 * cast because a GSS buffer_t uses a size_t for the length field wich
 * is 64 bits in a 64 bit process. The xdr encoding always assumes the
 * length to be 32 bits :<.
 */

static dh_channel_binding_t
GSS2DH_channel_binding(dh_channel_binding_t dh_binding,
                    gss_channel_bindings_t gss_binding)
{
        if (gss_binding == GSS_C_NO_CHANNEL_BINDINGS)
                return (NULL);

        dh_binding->initiator_addrtype = gss_binding->initiator_addrtype;
        dh_binding->initiator_address.dh_buffer_desc_len =
                (uint32_t)gss_binding->initiator_address.length;
        if (gss_binding->initiator_address.length !=
                dh_binding->initiator_address.dh_buffer_desc_len)
                return (NULL);
        dh_binding->initiator_address.dh_buffer_desc_val =
                gss_binding->initiator_address.value;
        dh_binding->acceptor_addrtype = gss_binding->acceptor_addrtype;
        dh_binding->acceptor_address.dh_buffer_desc_len =
                (uint32_t)gss_binding->acceptor_address.length;
        dh_binding->acceptor_address.dh_buffer_desc_val =
                gss_binding->acceptor_address.value;
        dh_binding->application_data.dh_buffer_desc_len =
                (uint32_t)gss_binding->application_data.length;
        dh_binding->application_data.dh_buffer_desc_val =
                gss_binding->application_data.value;

        return (dh_binding);
}

static gss_channel_bindings_t
DH2GSS_channel_binding(gss_channel_bindings_t gss_binding,
                    dh_channel_binding_t dh_binding)
{
        if (dh_binding == NULL)
                return (GSS_C_NO_CHANNEL_BINDINGS);

        gss_binding->initiator_addrtype = dh_binding->initiator_addrtype;
        gss_binding->initiator_address.length =
                dh_binding->initiator_address.dh_buffer_desc_len;
        gss_binding->initiator_address.value =
                dh_binding->initiator_address.dh_buffer_desc_val;
        gss_binding->acceptor_addrtype = dh_binding->acceptor_addrtype;
        gss_binding->acceptor_address.length =
                dh_binding->acceptor_address.dh_buffer_desc_len;
        gss_binding->acceptor_address.value =
                dh_binding->acceptor_address.dh_buffer_desc_val;
        gss_binding->application_data.length =
                dh_binding->application_data.dh_buffer_desc_len;
        gss_binding->application_data.value =
                dh_binding->application_data.dh_buffer_desc_val;

        return (gss_binding);
}

/*
 * Routine to compare that two gss_buffers are the same.
 */
static bool_t
gss_buffer_cmp(gss_buffer_t b1, gss_buffer_t b2)
{
        if (b1->length != b2->length)
                return (FALSE);
        if (b1->length == 0)
                return (TRUE);
        if (b1->value == b2->value)
                return (TRUE);
        if (b1->value == 0 || b2->value == 0)
                return (FALSE);

        return (memcmp(b1->value, b2->value, b1->length) == 0);
}

/*
 * Compare if two channel bindings are the same. If the local binding is
 * NULL then we always return TRUE. This indicates that the local host
 * does not care about any bindings.
 */

static bool_t
gss_chanbind_cmp(gss_channel_bindings_t local, gss_channel_bindings_t remote)
{
        if (local == NULL)
                return (TRUE); /* local doesn't care so we won't either */

        if (remote == NULL)
                return (FALSE);

        if (local->initiator_addrtype != remote->initiator_addrtype)
                return (FALSE);

        if (local->initiator_addrtype != GSS_C_AF_NULLADDR)
                if (gss_buffer_cmp(&local->initiator_address,
                                    &remote->initiator_address) == FALSE)
                        return (FALSE);

        if (local->acceptor_addrtype != remote->acceptor_addrtype)
                return (FALSE);

        if (local->acceptor_addrtype != GSS_C_AF_NULLADDR)
                if (gss_buffer_cmp(&local->acceptor_address,
                                    &remote->acceptor_address) == FALSE)
                        return (FALSE);

        return (gss_buffer_cmp(&local->application_data,
                                &remote->application_data));
}

/*
 * Generate an accept token for a context and channel binding puting the
 * generated token output.
 */

static
OM_uint32
gen_accept_token(dh_gss_context_t ctx, /* Diffie-Hellman context */
                gss_channel_bindings_t channel, /* channel bindings */
                gss_buffer_t output /* The accept token */)
{
        dh_token_desc token;
        /* Grap a pointer to the context_t part of the token */
        dh_cntx_t accept = &token.ver.dh_version_u.
                                body.dh_token_body_desc_u.accept_context.cntx;
        dh_key_set keys;
        dh_channel_binding_desc dh_binding;

        /* Set the version number from the context. */
        token.ver.verno = ctx->proto_version;
        /* Set the token type to be an ACCEPT token. */
        token.ver.dh_version_u.body.type = DH_ACCEPT_CNTX;
        /* Set our self as the remote for the other end. */
        accept->remote = ctx->local;
        /* The remote side to us is the local side at the other end. */
        accept->local = ctx->remote;
        /* Our context flags */
        accept->flags = ctx->flags;
        /* When we will expire */
        accept->expire = ctx->expire;
        /* Our channel bindings */
        accept->channel = GSS2DH_channel_binding(&dh_binding, channel);
        /* Package the context session keys into a key_set */
        keys.dh_key_set_len = ctx->no_keys;
        keys.dh_key_set_val = ctx->keys;

        /* Build the token */
        return (__make_token(output, NULL, &token, &keys));
}

/*
 * Check if a credential is valid for the requested usage. Note that
 * Diffie-Hellman only supports credentials based on the callers net
 * name. netname will point to the users rpc netname. It is up to the
 * caller to free the netname.
 */

static OM_uint32
validate_cred(dh_context_t cntx, /* Diffie-Hellman mechanism context */
            OM_uint32 *minor,    /* Mechanism status */
            dh_cred_id_t cred, /* Diffie-Hellman credential */
            gss_cred_usage_t usage, /* Cred usage */
            dh_principal *netname /* Cred owner */)
{
        /* Set minor status */
        *minor = DH_SUCCESS;
        *netname = NULL;

        /*
         * See if the users creditial is available, i.e.,
         * the user is "key logged" in.
         */
        if (!cntx->keyopts->key_secretkey_is_set()) {
                *minor = DH_NO_SECRET;
                return (GSS_S_NO_CRED);
        }


        /*
         * Get the netname.
         */

        if ((*netname = cntx->keyopts->get_principal()) == NULL) {
                *minor = DH_NO_PRINCIPAL;
                return (GSS_S_NO_CRED);
        }

        /*
         * Check if the supplied cred is valid for the requested usage.
         * The default cred never expires and has a usage of GSS_C_BOTH.
         */

        if ((gss_cred_id_t)cred != GSS_C_NO_CREDENTIAL) {
                if ((cred->usage != usage &&
                    cred->usage != GSS_C_BOTH) ||
                    strcmp(*netname, cred->principal) != 0) {
                        free(*netname);
                        return (GSS_S_NO_CRED);
                }

                /* See if the cred is still valid */
                if (cred->expire != GSS_C_INDEFINITE &&
                    time(0) > cred->expire) {
                        free(*netname);
                        return (GSS_S_CREDENTIALS_EXPIRED);
                }
        }
        return (GSS_S_COMPLETE);
}


/*
 * establish_session_keys: This routine decrypts the session keys supplied
 * and uses those keys to verifiy the signature over the input token
 * match the signature in the token.
 */
static OM_uint32
establish_session_keys(dh_context_t dhctx, const char *remote,
                    dh_key_set_t keys, dh_signature_t sig, dh_token_t token)
{
        OM_uint32 stat;
        int i, j;
        des_block *saved_keys;
        char *saved_sig;

        /*
         * The following variable is used by the keyopts key_decryptsessions
         * entry point. If this variable is non zero and the underling
         * mechanism uses a cache of public keys, then get the public key
         * for the remote out of that cache. When key_decrptsessions return
         * this variable will be set to non zero if the key did come
         * out of the cache, otherwise it will be set to zero.
         */
        int key_was_from_cache = 1;

        /* Save the keyset so if we fail we can try again */
        if ((saved_keys = New(des_block, keys->dh_key_set_len)) == NULL)
                return (DH_NOMEM_FAILURE);

        for (i = 0; i < keys->dh_key_set_len; i++)
                saved_keys[i] = keys->dh_key_set_val[i];

        /* Save the unencrypted signature as well for retry attempt */
        if ((saved_sig = New(char, sig->dh_signature_len)) == NULL) {
                Free(saved_keys);
                return (DH_NOMEM_FAILURE);
        }
        memcpy(saved_sig, sig->dh_signature_val, sig->dh_signature_len);

        /*
         * We will try to decrypt the session keys up to two times.
         * The first time will let the underlying mechanism use a
         * public key cache, if the set of session keys fail to
         * validate the signature that is reported in the deserialized
         * token, and those session keys were decrypted by a key
         * derived from a public key cache, then we will try again but
         * this time will advise the underlying mechanism not to use
         * its cache.
         */

        for (i = 0; key_was_from_cache && i < 2; i++) {
                /*
                 * Decrypt the session keys using the mechanism specific
                 * routine and if this is the second time, don't use
                 * the cache.
                 */
                if (i == 1)
                        key_was_from_cache = 0;
                if (dhctx->keyopts->key_decryptsessions(remote,
                                                        keys->dh_key_set_val,
                                                        keys->dh_key_set_len,
                                                        &key_was_from_cache)) {
                        Free(saved_keys);
                        Free(saved_sig);
                        return (DH_SESSION_CIPHER_FAILURE);
                }

#ifdef DH_DEBUG
                fprintf(stderr, "Received session keys %s the cache:\n",
                        key_was_form_cache ? "using" : "not using");
                for (i = 0; i < keys->dh_key_set_len; i++)
                        fprintf(stderr, "%08.8x%08.8x ",
                                keys->dh_key_set_val[i].key.high,
                                keys->dh_key_set_val[i].key.low);
                fprintf(stderr, "\n");
#endif

                /*
                 * Now verify that the extracted signature from the
                 * deserialized token is the same as our calculation
                 * of the signature.
                 */
                if ((stat = __verify_sig(token, DH_MECH_QOP, keys, sig)) ==
                    DH_SUCCESS) {
                        Free(saved_keys);
                        Free(saved_sig);
                        return (DH_SUCCESS);

                }

                /* Restore the keys and signature for retry */
                for (j = 0; j < keys->dh_key_set_len; j++)
                        keys->dh_key_set_val[j] = saved_keys[j];

                memcpy(sig->dh_signature_val, saved_sig, sig->dh_signature_len);
        }

        Free(saved_keys);
        Free(saved_sig);
        return (stat);
}
/*
 * This is the Diffie-Hellman mechanism entry point for the
 * gss_accept_sec context. See RFC 2078 for details. This
 * routine accepts a context establish token from the initator
 * and optionally produces a token to send back to the initator to
 * establish a GSS security context. The established context will
 * be return via the *gss_ctx paramater.
 */

OM_uint32
__dh_gss_accept_sec_context(void *ctx, /* Per mechanism context */
                            OM_uint32 *minor, /* Mechanism status */
                            gss_ctx_id_t *gss_ctx, /* GSS context */
                            gss_cred_id_t cred, /* GSS credential */
                            gss_buffer_t input, /* Input from initiator */
                                /* Local channel bindings  */
                            gss_channel_bindings_t  channel,
                            gss_name_t *principal, /* Initiator name */
                            gss_OID* mech, /* Returned mechanism */
                            gss_buffer_t output, /* Token to send initiator */
                            OM_uint32 *flags, /* flags of context */
                            OM_uint32 *expire, /* Time left on context */
                            gss_cred_id_t *del_cred /* Delegated credential */)
{
        dh_token_desc token;
        /* ctx is a Diffie-Hellman mechanism context */
        dh_context_t dhctx = (dh_context_t)ctx;
        dh_gss_context_t g_cntx = NULL;
        dh_principal netname = NULL;
        dh_init_context_t clnt;
        OM_uint32 stat;
        int i;
        dh_signature sig;
        struct gss_channel_bindings_struct dh_binding_desc;
        gss_channel_bindings_t dh_binding;

        /* Check for required parameters */
        if (input == NULL)
                return (GSS_S_CALL_INACCESSIBLE_READ);
        if (minor == NULL || output == NULL || gss_ctx == NULL)
                return (GSS_S_CALL_INACCESSIBLE_WRITE);

        /* Give outputs sane values if present */
        *minor = 0;
        if (principal)
                *principal = NULL;
        if (mech)
                *mech = GSS_C_NO_OID;
        if (flags)
                *flags  = 0;
        if (expire)
                *expire = 0;
        if (del_cred)
                *del_cred = GSS_C_NO_CREDENTIAL;

        output->length = 0;
        output->value = 0;

        /*
         * Diffie-Hellman never returns GSS_S_CONTINUE_NEEDED from a
         * gss_accept_sec_context so the only context read should be
         * GSS_C_NO_CONTEXT.
         */
        if (*gss_ctx != GSS_C_NO_CONTEXT)
                return (GSS_S_NO_CONTEXT);

        /* Valdidate the local credentinal and retrieve then principal name */
        stat = validate_cred(dhctx, minor,
                            (dh_cred_id_t)cred, GSS_C_ACCEPT, &netname);
        if (stat != GSS_S_COMPLETE)
                return (stat);

        /*
         * Deserialize the input into token, extracting the signature
         * into sig. Where sig is our calculation of the MD5 check sum
         * over the input token up to the signature.
         */
        memset(&sig, 0, sizeof (sig));
        if (*minor = __get_ap_token(input, dhctx->mech, &token, &sig)) {
                free(netname);
                __free_signature(&sig);
                return (GSS_S_DEFECTIVE_TOKEN);
        }

        /* set clnt to point to the init context part of token */
        clnt = &token.ver.dh_version_u.body.dh_token_body_desc_u.init_context;

        /* Check that this context is really for us */
        if (strcmp(clnt->cntx.local, netname) != 0) {
                free(netname);
                *minor = DH_NOT_LOCAL;
                stat = GSS_S_DEFECTIVE_TOKEN;
                goto cleanup;
        }
        free(netname);

        /*
         * See if this is a DH protocol version that we can handle.
         * Currently we can handle the one and only DH_PROTO_VERSION.
         */

        if (token.ver.verno != DH_PROTO_VERSION) {
                *minor = DH_PROTO_MISMATCH;
                stat = GSS_S_DEFECTIVE_TOKEN;
                goto cleanup;
        }

        /* Decrypt the session keys and verify the signature */
        if ((*minor = establish_session_keys(dhctx, clnt->cntx.remote,
                                            &clnt->keys,
                                            &sig, &token)) != DH_SUCCESS) {
                stat = GSS_S_BAD_SIG;
                goto cleanup;
        }

        /* Check that the channel bindings are the same */
        dh_binding = DH2GSS_channel_binding(&dh_binding_desc,
                                            clnt->cntx.channel);
        if (!gss_chanbind_cmp(channel, dh_binding)) {
                stat = GSS_S_BAD_BINDINGS;
                goto cleanup;
        }

        /* Everything is OK, so allocate the context */
        if ((g_cntx = New(dh_gss_context_desc, 1)) == NULL) {
                *minor = DH_NOMEM_FAILURE;
                stat = GSS_S_FAILURE;
                goto cleanup;
        }

        /*
         * The context is now established for us, though we may still
         * need to send a token if the initiator requested mutual
         * authentications.
         */
        g_cntx->state = ESTABLISHED;
        /* We're not the initiator */
        g_cntx->initiate = 0;
        /* Set the protocol version from the token */
        g_cntx->proto_version = token.ver.verno;
        /* Initialize the sequence history */
        __dh_init_seq_hist(g_cntx);
        /* Set debug to false */
        g_cntx->debug = 0;

        /* Set who the initiator is */
        if ((g_cntx->remote = strdup(clnt->cntx.remote)) == NULL) {
                *minor = DH_NOMEM_FAILURE;
                stat = GSS_S_FAILURE;
                goto cleanup;
        }

        /* Set who we are */
        if ((g_cntx->local = strdup(clnt->cntx.local)) == NULL) {
                *minor = DH_NOMEM_FAILURE;
                stat = GSS_S_FAILURE;
                goto cleanup;
        }

        /* Stash a copy of the session keys for the context */
        g_cntx->no_keys = clnt->keys.dh_key_set_len;
        if ((g_cntx->keys = New(des_block, g_cntx->no_keys)) == NULL) {
                *minor = DH_NOMEM_FAILURE;
                stat = GSS_S_FAILURE;
                goto cleanup;
        }

        for (i = 0; i < g_cntx->no_keys; i++)
                g_cntx->keys[i] = clnt->keys.dh_key_set_val[i];

        /* Set the flags and expire time */
        g_cntx->flags = clnt->cntx.flags;
        g_cntx->expire = clnt->cntx.expire;

        /* Create output token if needed */
        if (g_cntx->flags & GSS_C_MUTUAL_FLAG) {
                if (*minor = gen_accept_token(g_cntx, channel, output)) {
                        stat = GSS_S_FAILURE;
                        goto cleanup;
                }
        }

        /* This is now a valid context */
        if ((*minor = __dh_install_context(g_cntx)) != DH_SUCCESS) {
                stat = GSS_S_FAILURE;
                goto cleanup;
        }

        /* Return the GSS context to the caller */
        *gss_ctx = (gss_ctx_id_t)g_cntx;

        /* Return the remote principal if requested */
        if (principal)
                *principal = (gss_name_t)strdup(g_cntx->remote);
        /* Return the flags if requested */
        if (flags)
                *flags = g_cntx->flags;
        /* Return the expire time if requested */
        if (expire)
                *expire = g_cntx->expire;
        /* Return the mechanism if requested */
        if (mech)
                *mech = dhctx->mech;

        /* Release storage of the signature */
        __free_signature(&sig);

        /* Tear down the deserialize token */
        xdr_free(xdr_dh_token_desc, (char *)&token);

        /* We're done */
        return (GSS_S_COMPLETE);

cleanup:
        /* Destroy incomplete context */
        if (g_cntx) {
                __dh_destroy_seq_hist(g_cntx);
                (void) __dh_remove_context(g_cntx);
                free(g_cntx->remote);
                free(g_cntx->local);
                Free(g_cntx->keys);
                Free(g_cntx);
        }

        /* Release the signature and the deserialized token. */
        __free_signature(&sig);
        xdr_free(xdr_dh_token_desc, (char *)&token);

        return (stat);
}


/*
 * gen_init_token: create a token to pass to the other side
 * to create a GSS context.
 */
static
OM_uint32
gen_init_token(dh_gss_context_t cntx, /* Diffie-Hellman GSS context */
            dh_context_t dhctx,    /* Diffie-Hellman mechanism context */
            gss_channel_bindings_t channel, /* local channel bindings */
            gss_buffer_t result /* The serialized token to send */)
{
        dh_token_desc token;    /* Unserialed token */
        dh_init_context_t remote;  /* init_context in token */
        dh_key_set keys, ukeys; /* encrypted and unencrypted keys */
        int i, stat;
        dh_channel_binding_desc dh_binding;

        /* Create key_set for session keys */
        if ((keys.dh_key_set_val = New(des_block, cntx->no_keys)) == NULL)
                return (DH_NOMEM_FAILURE);

        keys.dh_key_set_len = cntx->no_keys;
        for (i = 0; i < cntx->no_keys; i++)
                keys.dh_key_set_val[i] = cntx->keys[i];

        /* Initialize token from GSS context */
        memset(&token, 0, sizeof (token));
        token.ver.verno = cntx->proto_version;
        token.ver.dh_version_u.body.type = DH_INIT_CNTX;

        /* Set remote to init_context part of token */
        remote = &token.ver.dh_version_u.body.dh_token_body_desc_u.init_context;
        /* We're the remote to the other side */
        remote->cntx.remote = cntx->local;
        /* And they are the local */
        remote->cntx.local = cntx->remote;
        /* Set our flags */
        remote->cntx.flags = cntx->flags;
        /* Set the expire time */
        remote->cntx.expire = cntx->expire;
        /* hand of our channel bindings */
        remote->cntx.channel = GSS2DH_channel_binding(&dh_binding, channel);
        /* set the tokens keys */
        remote->keys = keys;


        /* Encrypt the keys for the other side */

        if (dhctx->keyopts->key_encryptsessions(cntx->remote,
                                                keys.dh_key_set_val,
                                                cntx->no_keys)) {
                Free(keys.dh_key_set_val);
                return (DH_SESSION_CIPHER_FAILURE);
        }

        /* Package up our session keys */
        ukeys.dh_key_set_len = cntx->no_keys;
        ukeys.dh_key_set_val = cntx->keys;
        /*
         * Make an APPLICATION 0 token and place it in result.
         * Note that the unecrypted ukeys key_set is used to sign
         * the token.
         */
        stat =  __make_ap_token(result, dhctx->mech, &token, &ukeys);

        /* We're don with the encrypted session keys */
        Free(keys.dh_key_set_val);

        /* Return our status */
        return (stat);
}

/*
 * create_context: Builds the initial Diffie-Hellman GSS context.
 * It should always be the case that *gss_ctx == GSS_C_NO_CONTEXT
 * on entering this routine. Given the inputs we created a Diffie-Hellman
 * context from them. This routine will call gen_init_token above to
 * generate the output token to pass to the other side.
 */
static
OM_uint32
create_context(OM_uint32 *minor, /* Diffie-Hellman specific status */
            dh_context_t cntx, /* Diffie-Hellman mech context */
            dh_gss_context_t *gss_ctx, /* DH GSS context */
            dh_principal netname, /* Local principal */
            dh_principal target, /* Remote principal */
            gss_channel_bindings_t channel, /* Channel bindings */
            OM_uint32 flags_req, /* Flags to set on context */
            OM_uint32 time_req, /* Time to live for context */
            OM_uint32 *flags_rec, /* Flags that were actually set */
            OM_uint32 *time_rec, /* Time actually received */
            gss_buffer_t results /* Output token for the other side */)
{
        dh_gss_context_t dh_gss_ctx; /* The Diffie-Hellman context to create */
        time_t now = time(0);   /* Used to set the expire time */
        OM_uint32 expire;       /* Time left on the context */

        /* Create the Diffie-Hellman context */
        if ((*gss_ctx = dh_gss_ctx = New(dh_gss_context_desc, 1)) == NULL) {
                *minor = DH_NOMEM_FAILURE;
                return (GSS_S_FAILURE);
        }

        /* We're not established yet */
        dh_gss_ctx->state = INCOMPLETE;
        /* We're the initiator */
        dh_gss_ctx->initiate = 1;
        /* Set the protocol version for the context */
        dh_gss_ctx->proto_version = DH_PROTO_VERSION;
        /* Initialize the sequence and replay history */
        __dh_init_seq_hist(dh_gss_ctx);
        /* Turn off debugging */
        dh_gss_ctx->debug = 0;

        dh_gss_ctx->local = NULL;

        /* Remember who we want to talk to. */
        if ((dh_gss_ctx->remote = strdup(target)) == NULL) {
                *minor = DH_NOMEM_FAILURE;
                goto cleanup;
        }

        /* Rember who we are. */
        if ((dh_gss_ctx->local = strdup(netname)) == NULL) {
                *minor = DH_NOMEM_FAILURE;
                goto cleanup;
        }

        /* Set up the session key */
        dh_gss_ctx->no_keys = 3;
        dh_gss_ctx->keys = New(des_block, 3);
        if (dh_gss_ctx->keys == NULL) {
                *minor = DH_NOMEM_FAILURE;
                goto cleanup;
        }

        /* Call the mechanism specific key generator */
        if (cntx->keyopts->key_gendeskeys(dh_gss_ctx->keys, 3)) {
                *minor = DH_NOMEM_FAILURE;
                goto cleanup;
        }

#ifdef DH_DEBUG
        {
                int i;

                fprintf(stderr, "Generated session keys:\n");
                for (i = 0; i < dh_gss_ctx->no_keys; i++)
                        fprintf(stderr, "%08.8x%08.8x ",
                                dh_gss_ctx->keys[i].key.high,
                                dh_gss_ctx->keys[i].key.low);
                fprintf(stderr, "\n");
        }
#endif

        /*
         *  We don't support currently support
         *  GSS_C_ANON_FLAG and GSS_C_DELEG_FLAG and GSS_C_CONF_FLAG
         */

        dh_gss_ctx->flags = (flags_req &
            (GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG |
                    GSS_C_SEQUENCE_FLAG | GSS_C_REPLAY_FLAG));

        /* This mechanism does integrity */
        dh_gss_ctx->flags |=  GSS_C_INTEG_FLAG;

        /* Return flags to the caller if they care */
        if (flags_rec)
                *flags_rec = dh_gss_ctx->flags;

        /* Set expire, 0 is the default, which means indefinite */
        expire = time_req ? time_req : GSS_C_INDEFINITE;
        /* Actually set the expire time for the context */
        dh_gss_ctx->expire = expire == GSS_C_INDEFINITE ?
                expire : expire + now;
        /* Tell the call the time given to the context if they care */
        if (time_rec)
                *time_rec = expire;

        /* Gennerate the output token to send to the other side */
        *minor = gen_init_token(dh_gss_ctx, cntx,
                                channel, results);
        if (*minor != DH_SUCCESS)
                goto cleanup;

        /* Recored this context as valid */
        if ((*minor = __dh_install_context(dh_gss_ctx)) != DH_SUCCESS)
                goto cleanup;

        /* If we ask for mutal authentication return continue needed */
        dh_gss_ctx->state = dh_gss_ctx->flags & GSS_C_MUTUAL_FLAG ?
                INCOMPLETE : ESTABLISHED;

        return (dh_gss_ctx->state == ESTABLISHED ?
                GSS_S_COMPLETE : GSS_S_CONTINUE_NEEDED);
cleanup:

        __dh_destroy_seq_hist(dh_gss_ctx);
        free(dh_gss_ctx->remote);
        free(dh_gss_ctx->local);
        Free(dh_gss_ctx->keys);
        Free(dh_gss_ctx);

        /*
         * Let the caller of gss_init_sec_context know that they don't
         * have a context.
         */
        *gss_ctx = (dh_gss_context_t)GSS_C_NO_CONTEXT;

        return (GSS_S_FAILURE);
}

/*
 * continue_context: Proccess the token from the otherside in the case
 * of mutual authentication.
 */
static
OM_uint32
continue_context(OM_uint32 *minor, gss_buffer_t token,
    dh_gss_context_t dh_gss_ctx, gss_channel_bindings_t channel)
{
        dh_key_set keys;
        dh_token_desc tok;
        dh_cntx_t remote_ctx;
        struct gss_channel_bindings_struct remote_chan_desc;
        gss_channel_bindings_t remote_chan;

        /* Set minor to sane state */
        *minor = DH_SUCCESS;

        /* This should never happen */
        if (token == NULL || token->length == 0)
                return (GSS_S_DEFECTIVE_TOKEN);

        /* Package the session keys for __get_token) */
        keys.dh_key_set_len = dh_gss_ctx->no_keys;
        keys.dh_key_set_val = dh_gss_ctx->keys;

        /* Deserialize the input token into tok using the session keys */
        if (*minor = __get_token(token, NULL, &tok, &keys))
                return (*minor == DH_VERIFIER_MISMATCH ?
                        GSS_S_BAD_SIG : GSS_S_DEFECTIVE_TOKEN);

        /*
         * See if this is a Diffie-Hellman protocol version that we
         * can handle. Currently we can only handle the protocol version that
         * we initiated.
         */
        if (tok.ver.verno != dh_gss_ctx->proto_version) {
                *minor = DH_PROTO_MISMATCH;
                xdr_free(xdr_dh_token_desc, (char *)&tok);
                return (GSS_S_DEFECTIVE_TOKEN);
        }

        /* Make sure this is the right type of token */
        if (tok.ver.dh_version_u.body.type != DH_ACCEPT_CNTX) {
                xdr_free(xdr_dh_token_desc, (char *)&tok);
                return (GSS_S_DEFECTIVE_TOKEN);
        }

        /* Grab a pointer to the context part of the token */
        remote_ctx = &tok.ver.dh_version_u.
                        body.dh_token_body_desc_u.accept_context.cntx;

        /* Make sure this is from the remote and for us */
        if (strcmp(remote_ctx->remote, dh_gss_ctx->remote) ||
            strcmp(remote_ctx->local, dh_gss_ctx->local)) {
                xdr_free(xdr_dh_token_desc, (char *)&tok);
                return (GSS_S_DEFECTIVE_TOKEN);
        }

        /* Make sure if the optional channel_bindings are the same */
        remote_chan = DH2GSS_channel_binding(&remote_chan_desc,
                                            remote_ctx->channel);
        if (!gss_chanbind_cmp(channel, remote_chan)) {
                xdr_free(xdr_dh_token_desc, (char *)&tok);
                return (GSS_S_BAD_BINDINGS);
        }

        /* Update the context flags with what the remote will accept */
        dh_gss_ctx->flags = remote_ctx->flags;

        /* We now have an established context */
        dh_gss_ctx->state = ESTABLISHED;

        /* Release the deserialized token, tok */
        xdr_free(xdr_dh_token_desc, (char *)&tok);

        return (GSS_S_COMPLETE);
}

/*
 * This is the Diffie-Hellman mechanism entry point for the
 * gss_int_sec context. See RFC 2078 for details. This
 * routine creates a new context or continues a previously created
 * context if mutual authentication had been requested on the orignal
 * context. The first call to this routine should set *context to
 * GSS_C_NO_CONTEXT and input_token to GSS_C_NO_BUFFER or input_token->length
 * to zero. To continue a context in the case of mutual authentication
 * gss_ctx should point to the initial context and input_token should point
 * to the token received from the remote. The established context will
 * be return via the *context paramater in all cases.
 */


OM_uint32
__dh_gss_init_sec_context(void *ctx, /* Per Mechananism context */
                        OM_uint32 *minor, /* Mech status */
                        gss_cred_id_t cred, /* Local credentials */
                        gss_ctx_id_t *context, /* The context to create */
                        gss_name_t target, /* The server to talk to */
                        gss_OID mech, /* The mechanism to use */
                        OM_uint32 req_flags, /* Requested context flags */
                        OM_uint32 time_req, /* Requested life time */
                        gss_channel_bindings_t channel, /* Local bindings */
                        gss_buffer_t input_token, /* Token from remote */
                        gss_OID *mech_rec, /* Optional mech to return */
                        gss_buffer_t output_token, /* Token for remote */
                        OM_uint32 *flags_rec, /* Actual flags received */
                        OM_uint32 *time_rec /* Actual life time received */)
{
        dh_context_t cntx = (dh_context_t)ctx;
        dh_gss_context_t dh_gss_ctx = (dh_gss_context_t)*context;
        dh_principal netname;
        dh_cred_id_t dh_cred = (dh_cred_id_t)cred;
        OM_uint32 stat;

        /* We need these */
        if (minor == 0 || output_token == 0)
                return (GSS_S_CALL_INACCESSIBLE_WRITE);

        /* Set to sane state */
        *minor = DH_SUCCESS;
        output_token->length = 0;
        output_token->value = NULL;
        if (mech_rec)
                *mech_rec = cntx->mech;   /* Note this should not be duped. */

        /* Check that were the right mechanism */
        if ((mech != GSS_C_NULL_OID) &&
            (!__OID_equal(mech, cntx->mech))) {
                return (GSS_S_BAD_MECH);
        }

        /* Validate the cred and obtain our netname in the process. */
        stat = validate_cred(cntx, minor, dh_cred, GSS_C_INITIATE, &netname);
        if (stat != GSS_S_COMPLETE)
                return (stat);

        /* validate target name */
        /*
         * we could check that the target is in the proper form and
         * possibly do a lookup up on the host part.
         */

        /* checks for new context */
        if (dh_gss_ctx == (dh_gss_context_t)GSS_C_NO_CONTEXT) {

                if (input_token != GSS_C_NO_BUFFER &&
                        input_token->length != 0)
                        return (GSS_S_DEFECTIVE_TOKEN);

                /* Create a new context */
                stat =  create_context(minor, cntx, &dh_gss_ctx, netname,
                                    (dh_principal)target, channel, req_flags,
                                    time_req, flags_rec, time_rec,
                                    output_token);

                /* Set the GSS context to the Diffie-Hellman context */
                *context = (gss_ctx_id_t)dh_gss_ctx;

        } else {

                /* Validate the context */
                if ((*minor = __dh_validate_context(dh_gss_ctx)) != DH_SUCCESS)
                        return (GSS_S_NO_CONTEXT);

                /* Authenticate the server */
                stat = continue_context(minor,
                                        input_token, dh_gss_ctx, channel);

        }

        free(netname);
        return (stat);
}