/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* kdc/fast_util.c */
/*
 * Copyright (C) 2009 by the Massachusetts Institute of Technology.
 * All rights reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 */

#include <k5-int.h>

#include "kdc_util.h"
#include "extern.h"


/*
 * This function will find the fast and cookie padata and if fast is
 * successfully processed, will throw away (and free) the outer
 * request and update the pointer to point to the inner request.  The
 * checksummed_data points to the data that is in the
 * armored_fast_request checksum; either the pa-tgs-req or the
 * kdc-req-body.
 */

static krb5_error_code armor_ap_request
(struct kdc_request_state *state, krb5_fast_armor *armor)
{
    krb5_error_code retval = 0;
    krb5_auth_context authcontext = NULL;
    krb5_ticket *ticket = NULL;
    krb5_keyblock *subkey = NULL;

    assert(armor->armor_type == KRB5_FAST_ARMOR_AP_REQUEST);
    krb5_clear_error_message(kdc_context);
    retval = krb5_auth_con_init(kdc_context, &authcontext);
    if (retval == 0)
        retval = krb5_auth_con_setflags(kdc_context,
                                        authcontext, 0); /*disable replay cache*/
    retval = krb5_rd_req(kdc_context, &authcontext,
                         &armor->armor_value, NULL /*server*/,
                         kdc_active_realm->realm_keytab,  NULL, &ticket);
    if (retval != 0) {
        const char * errmsg = krb5_get_error_message(kdc_context, retval);
        krb5_set_error_message(kdc_context, retval,
                               _("%s while handling ap-request armor"),
                               errmsg);
        krb5_free_error_message(kdc_context, errmsg);
    }
    if (retval == 0) {
        if (!krb5_principal_compare_any_realm(kdc_context,
                                              tgs_server,
                                              ticket->server)) {
            krb5_set_error_message(kdc_context, KRB5KDC_ERR_SERVER_NOMATCH,
                                   _("ap-request armor for something other "
                                     "than the local TGS"));
            retval = KRB5KDC_ERR_SERVER_NOMATCH;
        }
    }
    if (retval == 0) {
        retval = krb5_auth_con_getrecvsubkey(kdc_context, authcontext, &subkey);
        if (retval != 0 || subkey == NULL) {
            krb5_set_error_message(kdc_context, KRB5KDC_ERR_POLICY,
                                   _("ap-request armor without subkey"));
            retval = KRB5KDC_ERR_POLICY;
        }
    }
    if (retval == 0)
        retval = krb5_c_fx_cf2_simple(kdc_context,
                                      subkey, "subkeyarmor",
                                      ticket->enc_part2->session, "ticketarmor",
                                      &state->armor_key);
    if (ticket)
        krb5_free_ticket(kdc_context, ticket);
    if (subkey)
        krb5_free_keyblock(kdc_context, subkey);
    if (authcontext)
        krb5_auth_con_free(kdc_context, authcontext);
    return retval;
}

static krb5_error_code
encrypt_fast_reply(struct kdc_request_state *state,
                   const krb5_fast_response *response,
                   krb5_data **fx_fast_reply)
{
    krb5_error_code retval = 0;
    krb5_enc_data encrypted_reply;
    krb5_data *encoded_response = NULL;
    assert(state->armor_key);
    retval = encode_krb5_fast_response(response, &encoded_response);
    if (retval== 0)
        retval = krb5_encrypt_helper(kdc_context, state->armor_key,
                                     KRB5_KEYUSAGE_FAST_REP,
                                     encoded_response, &encrypted_reply);
    if (encoded_response)
        krb5_free_data(kdc_context, encoded_response);
    encoded_response = NULL;
    if (retval == 0) {
        retval = encode_krb5_pa_fx_fast_reply(&encrypted_reply,
                                              fx_fast_reply);
        krb5_free_data_contents(kdc_context, &encrypted_reply.ciphertext);
    }
    return retval;
}


krb5_error_code
kdc_find_fast(krb5_kdc_req **requestptr,
              krb5_data *checksummed_data,
              krb5_keyblock *tgs_subkey,
              krb5_keyblock *tgs_session,
              struct kdc_request_state *state,
              krb5_data **inner_body_out)
{
    krb5_error_code retval = 0;
    krb5_pa_data *fast_padata, *cookie_padata = NULL;
    krb5_data scratch, *inner_body = NULL;
    krb5_fast_req * fast_req = NULL;
    krb5_kdc_req *request = *requestptr;
    krb5_fast_armored_req *fast_armored_req = NULL;
    krb5_checksum *cksum;
    krb5_boolean cksum_valid;
    krb5_keyblock empty_keyblock;

    if (inner_body_out != NULL)
        *inner_body_out = NULL;
    scratch.data = NULL;
    krb5_clear_error_message(kdc_context);
    memset(&empty_keyblock, 0, sizeof(krb5_keyblock));
    fast_padata = find_pa_data(request->padata,
                               KRB5_PADATA_FX_FAST);
    if (fast_padata !=  NULL){
        scratch.length = fast_padata->length;
        scratch.data = (char *) fast_padata->contents;
        retval = decode_krb5_pa_fx_fast_request(&scratch, &fast_armored_req);
        if (retval == 0 &&fast_armored_req->armor) {
            switch (fast_armored_req->armor->armor_type) {
            case KRB5_FAST_ARMOR_AP_REQUEST:
                if (tgs_subkey) {
                    retval = KRB5KDC_ERR_PREAUTH_FAILED;
                    krb5_set_error_message(kdc_context, retval,
                                           _("Ap-request armor not permitted "
                                             "with TGS"));
                    break;
                }
                retval = armor_ap_request(state, fast_armored_req->armor);
                break;
            default:
                krb5_set_error_message(kdc_context, KRB5KDC_ERR_PREAUTH_FAILED,
                                       _("Unknown FAST armor type %d"),
                                       fast_armored_req->armor->armor_type);
                retval = KRB5KDC_ERR_PREAUTH_FAILED;
            }
        }
        if (retval == 0 && !state->armor_key) {
            if (tgs_subkey)
                retval = krb5_c_fx_cf2_simple(kdc_context,
                                              tgs_subkey, "subkeyarmor",
                                              tgs_session, "ticketarmor",
                                              &state->armor_key);
            else {
                retval = KRB5KDC_ERR_PREAUTH_FAILED;
                krb5_set_error_message(kdc_context, retval,
                                       _("No armor key but FAST armored "
                                         "request present"));
            }
        }
        if (retval == 0) {
            krb5_data plaintext;
            plaintext.length = fast_armored_req->enc_part.ciphertext.length;
            plaintext.data = malloc(plaintext.length);
            if (plaintext.data == NULL)
                retval = ENOMEM;
            retval = krb5_c_decrypt(kdc_context,
                                    state->armor_key,
                                    KRB5_KEYUSAGE_FAST_ENC, NULL,
                                    &fast_armored_req->enc_part,
                                    &plaintext);
            if (retval == 0)
                retval = decode_krb5_fast_req(&plaintext, &fast_req);
            if (retval == 0 && inner_body_out != NULL) {
                retval = fetch_asn1_field((unsigned char *)plaintext.data,
                                          1, 2, &scratch);
                if (retval == 0) {
                    retval = krb5_copy_data(kdc_context, &scratch,
                                            &inner_body);
                }
            }
            if (plaintext.data)
                free(plaintext.data);
        }
        cksum = &fast_armored_req->req_checksum;
        if (retval == 0)
            retval = krb5_c_verify_checksum(kdc_context, state->armor_key,
                                            KRB5_KEYUSAGE_FAST_REQ_CHKSUM,
                                            checksummed_data, cksum,
                                            &cksum_valid);
        if (retval == 0 && !cksum_valid) {
            retval = KRB5KRB_AP_ERR_MODIFIED;
            krb5_set_error_message(kdc_context, retval,
                                   _("FAST req_checksum invalid; request "
                                     "modified"));
        }
        if (retval == 0) {
            if (!krb5_c_is_keyed_cksum(cksum->checksum_type)) {
                retval = KRB5KDC_ERR_POLICY;
                krb5_set_error_message(kdc_context, retval,
                                       _("Unkeyed checksum used in fast_req"));
            }
        }
        if (retval == 0) {
            if ((fast_req->fast_options & UNSUPPORTED_CRITICAL_FAST_OPTIONS) != 0)
                retval = KRB5KDC_ERR_UNKNOWN_CRITICAL_FAST_OPTION;
        }
        if (retval == 0)
            cookie_padata = find_pa_data(fast_req->req_body->padata,
                                         KRB5_PADATA_FX_COOKIE);
        if (retval == 0) {
            state->fast_options = fast_req->fast_options;
            krb5_free_kdc_req( kdc_context, request);
            *requestptr = fast_req->req_body;
            fast_req->req_body = NULL;
        }
    }
    else cookie_padata = find_pa_data(request->padata, KRB5_PADATA_FX_COOKIE);
    if (retval == 0 && cookie_padata != NULL) {
        krb5_pa_data *new_padata = malloc(sizeof (krb5_pa_data));
        if (new_padata == NULL) {
            retval = ENOMEM;
        } else {
            new_padata->pa_type = KRB5_PADATA_FX_COOKIE;
            new_padata->length = cookie_padata->length;
            new_padata->contents = malloc(new_padata->length);
            if (new_padata->contents == NULL) {
                retval = ENOMEM;
                free(new_padata);
            } else {
                memcpy(new_padata->contents, cookie_padata->contents,
                       new_padata->length);
                state->cookie = new_padata;
            }
        }
    }
    if (retval == 0 && inner_body_out != NULL) {
        *inner_body_out = inner_body;
        inner_body = NULL;
    }
    krb5_free_data(kdc_context, inner_body);
    if (fast_req)
        krb5_free_fast_req( kdc_context, fast_req);
    if (fast_armored_req)
        krb5_free_fast_armored_req(kdc_context, fast_armored_req);
    return retval;
}


krb5_error_code
kdc_make_rstate(struct kdc_request_state **out)
{
    struct kdc_request_state *state = malloc( sizeof(struct kdc_request_state));
    if (state == NULL)
        return ENOMEM;
    memset( state, 0, sizeof(struct kdc_request_state));
    *out = state;
    return 0;
}

void
kdc_free_rstate (struct kdc_request_state *s)
{
    if (s == NULL)
        return;
    if (s->armor_key)
        krb5_free_keyblock(kdc_context, s->armor_key);
    if (s->strengthen_key)
        krb5_free_keyblock(kdc_context, s->strengthen_key);
    if (s->cookie) {
        free(s->cookie->contents);
        free(s->cookie);
    }
    free(s);
}

krb5_error_code
kdc_fast_response_handle_padata(struct kdc_request_state *state,
                                krb5_kdc_req *request,
                                krb5_kdc_rep *rep, krb5_enctype enctype)
{
    krb5_error_code retval = 0;
    krb5_fast_finished finish;
    krb5_fast_response fast_response;
    krb5_data *encoded_ticket = NULL;
    krb5_data *encrypted_reply = NULL;
    krb5_pa_data *pa = NULL, **pa_array = NULL;
    krb5_cksumtype cksumtype = CKSUMTYPE_RSA_MD5;
    krb5_pa_data *empty_padata[] = {NULL};
    krb5_keyblock *strengthen_key = NULL;

    if (!state->armor_key)
        return 0;
    memset(&finish, 0, sizeof(finish));
    retval = krb5_init_keyblock(kdc_context, enctype, 0, &strengthen_key);
    if (retval == 0)
        retval = krb5_c_make_random_key(kdc_context, enctype, strengthen_key);
    if (retval == 0) {
        state->strengthen_key = strengthen_key;
        strengthen_key = NULL;
    }

    fast_response.padata = rep->padata;
    if (fast_response.padata == NULL)
        fast_response.padata = &empty_padata[0];
    fast_response.strengthen_key = state->strengthen_key;
    fast_response.nonce = request->nonce;
    fast_response.finished = &finish;
    finish.client = rep->client;
    pa_array = calloc(3, sizeof(*pa_array));
    if (pa_array == NULL)
        retval = ENOMEM;
    pa = calloc(1, sizeof(krb5_pa_data));
    if (retval == 0 && pa == NULL)
        retval = ENOMEM;
    if (retval == 0)
        retval = krb5_us_timeofday(kdc_context, &finish.timestamp, &finish.usec);
    if (retval == 0)
        retval = encode_krb5_ticket(rep->ticket, &encoded_ticket);
    if (retval == 0)
        retval = krb5int_c_mandatory_cksumtype(kdc_context,
                                               state->armor_key->enctype,
                                               &cksumtype);
    if (retval == 0)
        retval = krb5_c_make_checksum(kdc_context, cksumtype,
                                      state->armor_key,
                                      KRB5_KEYUSAGE_FAST_FINISHED,
                                      encoded_ticket, &finish.ticket_checksum);
    if (retval == 0)
        retval = encrypt_fast_reply(state, &fast_response, &encrypted_reply);
    if (retval == 0) {
        pa[0].pa_type = KRB5_PADATA_FX_FAST;
        pa[0].length = encrypted_reply->length;
        pa[0].contents = (unsigned char *)  encrypted_reply->data;
        pa_array[0] = &pa[0];
        krb5_free_pa_data(kdc_context, rep->padata);
        rep->padata = pa_array;
        pa_array = NULL;
        free(encrypted_reply);
        encrypted_reply = NULL;
        pa = NULL;
    }
    if (pa)
        free(pa);
    if (pa_array)
        free(pa_array);
    if (encrypted_reply)
        krb5_free_data(kdc_context, encrypted_reply);
    if (encoded_ticket)
        krb5_free_data(kdc_context, encoded_ticket);
    if (strengthen_key != NULL)
        krb5_free_keyblock(kdc_context, strengthen_key);
    if (finish.ticket_checksum.contents)
        krb5_free_checksum_contents(kdc_context, &finish.ticket_checksum);
    return retval;
}


/*
 * We assume the caller is responsible for passing us an in_padata
 * sufficient to include in a FAST error.  In the FAST case we will
 * set *fast_edata_out to the edata to be included in the error; in
 * the non-FAST case we will set it to NULL.
 */
krb5_error_code
kdc_fast_handle_error(krb5_context context,
                      struct kdc_request_state *state,
                      krb5_kdc_req *request,
                      krb5_pa_data  **in_padata, krb5_error *err,
                      krb5_data **fast_edata_out)
{
    krb5_error_code retval = 0;
    krb5_fast_response resp;
    krb5_error fx_error;
    krb5_data *encoded_fx_error = NULL, *encrypted_reply = NULL;
    krb5_pa_data pa[1];
    krb5_pa_data *outer_pa[3], *cookie = NULL;
    krb5_pa_data **inner_pa = NULL;
    size_t size = 0;

    *fast_edata_out = NULL;
    memset(outer_pa, 0, sizeof(outer_pa));
    if (!state || !state->armor_key)
        return 0;
    fx_error = *err;
    fx_error.e_data.data = NULL;
    fx_error.e_data.length = 0;
    for (size = 0; in_padata&&in_padata[size]; size++);
    size +=3;
    inner_pa = calloc(size, sizeof(krb5_pa_data *));
    if (inner_pa == NULL)
        retval = ENOMEM;
    if (retval == 0)
        for (size=0; in_padata&&in_padata[size]; size++)
            inner_pa[size] = in_padata[size];
    if (retval == 0)
        retval = encode_krb5_error(&fx_error, &encoded_fx_error);
    if (retval == 0) {
        pa[0].pa_type = KRB5_PADATA_FX_ERROR;
        pa[0].length = encoded_fx_error->length;
        pa[0].contents = (unsigned char *) encoded_fx_error->data;
        inner_pa[size++] = &pa[0];
        if (find_pa_data(inner_pa, KRB5_PADATA_FX_COOKIE) == NULL)
            retval = kdc_preauth_get_cookie(state, &cookie);
    }
    if (cookie != NULL)
        inner_pa[size++] = cookie;
    if (retval == 0) {
        resp.padata = inner_pa;
        resp.nonce = request->nonce;
        resp.strengthen_key = NULL;
        resp.finished = NULL;
    }
    if (retval == 0)
        retval = encrypt_fast_reply(state, &resp, &encrypted_reply);
    if (inner_pa)
        free(inner_pa); /*contained storage from caller and our stack*/
    if (cookie) {
        free(cookie->contents);
        free(cookie);
        cookie = NULL;
    }
    if (retval == 0) {
        pa[0].pa_type = KRB5_PADATA_FX_FAST;
        pa[0].length = encrypted_reply->length;
        pa[0].contents = (unsigned char *) encrypted_reply->data;
        outer_pa[0] = &pa[0];
    }
    retval = encode_krb5_padata_sequence(outer_pa, fast_edata_out);
    if (encrypted_reply)
        krb5_free_data(kdc_context, encrypted_reply);
    if (encoded_fx_error)
        krb5_free_data(kdc_context, encoded_fx_error);
    return retval;
}

krb5_error_code
kdc_fast_handle_reply_key(struct kdc_request_state *state,
                          krb5_keyblock *existing_key,
                          krb5_keyblock **out_key)
{
    krb5_error_code retval = 0;
    if (state->armor_key)
        retval = krb5_c_fx_cf2_simple(kdc_context,
                                      state->strengthen_key, "strengthenkey",
                                      existing_key,
                                      "replykey", out_key);
    else
        retval = krb5_copy_keyblock(kdc_context, existing_key, out_key);
    return retval;
}


krb5_error_code
kdc_preauth_get_cookie(struct kdc_request_state *state,
                       krb5_pa_data **cookie)
{
    char *contents;
    krb5_pa_data *pa = NULL;
    /* In our current implementation, the only purpose served by
     * returning a cookie is to indicate that a conversation should
     * continue on error.  Thus, the cookie can have a constant
     * string.  If cookies are used for real, versioning so that KDCs
     * can be upgraded, keying, expiration and many other issues need
     * to be considered.
     */
    contents = strdup("MIT");
    if (contents == NULL)
        return ENOMEM;
    pa = calloc(1, sizeof(krb5_pa_data));
    if (pa == NULL) {
        free(contents);
        return ENOMEM;
    }
    pa->pa_type = KRB5_PADATA_FX_COOKIE;
    pa->length = strlen(contents);
    pa->contents = (unsigned char *) contents;
    *cookie = pa;
    return 0;
}
