/*
 * Copyright (c) 1998 - 2005 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifdef FTP_SERVER
#include "ftpd_locl.h"
#else
#include "ftp_locl.h"
#endif
#include <gssapi/gssapi.h>
#include <gssapi/gssapi_krb5.h>
#include <krb5_err.h>

RCSID("$Id$");

int ftp_do_gss_bindings = 0;
int ftp_do_gss_delegate = 1;

struct gssapi_data {
    gss_ctx_id_t context_hdl;
    gss_name_t client_name;
    gss_cred_id_t delegated_cred_handle;
    void *mech_data;
};

static int
gss_init(void *app_data)
{
    struct gssapi_data *d = app_data;
    d->context_hdl = GSS_C_NO_CONTEXT;
    d->delegated_cred_handle = GSS_C_NO_CREDENTIAL;
#if defined(FTP_SERVER)
    return 0;
#else
    /* XXX Check the gss mechanism; with  gss_indicate_mechs() ? */
#ifdef KRB5
    return !use_kerberos;
#else
    return 0;
#endif /* KRB5 */
#endif /* FTP_SERVER */
}

static int
gss_check_prot(void *app_data, int level)
{
    if(level == prot_confidential)
        return -1;
    return 0;
}

static int
gss_decode(void *app_data, void *buf, int len, int level)
{
    OM_uint32 maj_stat, min_stat;
    gss_buffer_desc input, output;
    gss_qop_t qop_state;
    int conf_state;
    struct gssapi_data *d = app_data;
    size_t ret_len;

    input.length = len;
    input.value = buf;
    maj_stat = gss_unwrap (&min_stat,
                           d->context_hdl,
                           &input,
                           &output,
                           &conf_state,
                           &qop_state);
    if(GSS_ERROR(maj_stat))
        return -1;
    memmove(buf, output.value, output.length);
    ret_len = output.length;
    gss_release_buffer(&min_stat, &output);
    return ret_len;
}

static int
gss_overhead(void *app_data, int level, int len)
{
    return 100; /* dunno? */
}


static int
gss_encode(void *app_data, void *from, int length, int level, void **to)
{
    OM_uint32 maj_stat, min_stat;
    gss_buffer_desc input, output;
    int conf_state;
    struct gssapi_data *d = app_data;

    input.length = length;
    input.value = from;
    maj_stat = gss_wrap (&min_stat,
                         d->context_hdl,
                         level == prot_private,
                         GSS_C_QOP_DEFAULT,
                         &input,
                         &conf_state,
                         &output);
    *to = output.value;
    return output.length;
}

static void
sockaddr_to_gss_address (struct sockaddr *sa,
                         OM_uint32 *addr_type,
                         gss_buffer_desc *gss_addr)
{
    switch (sa->sa_family) {
#ifdef HAVE_IPV6
    case AF_INET6 : {
        struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;

        gss_addr->length = 16;
        gss_addr->value  = &sin6->sin6_addr;
        *addr_type       = GSS_C_AF_INET6;
        break;
    }
#endif
    case AF_INET : {
        struct sockaddr_in *sin4 = (struct sockaddr_in *)sa;

        gss_addr->length = 4;
        gss_addr->value  = &sin4->sin_addr;
        *addr_type       = GSS_C_AF_INET;
        break;
    }
    default :
        errx (1, "unknown address family %d", sa->sa_family);

    }
}

/* end common stuff */

#ifdef FTP_SERVER

static int
gss_adat(void *app_data, void *buf, size_t len)
{
    char *p = NULL;
    gss_buffer_desc input_token, output_token;
    OM_uint32 maj_stat, min_stat;
    gss_name_t client_name;
    struct gssapi_data *d = app_data;
    gss_channel_bindings_t bindings;

    if (ftp_do_gss_bindings) {
        bindings = malloc(sizeof(*bindings));
        if (bindings == NULL)
            errx(1, "out of memory");

        sockaddr_to_gss_address (his_addr,
                                 &bindings->initiator_addrtype,
                                 &bindings->initiator_address);
        sockaddr_to_gss_address (ctrl_addr,
                                 &bindings->acceptor_addrtype,
                                 &bindings->acceptor_address);

        bindings->application_data.length = 0;
        bindings->application_data.value = NULL;
    } else
        bindings = GSS_C_NO_CHANNEL_BINDINGS;

    input_token.value = buf;
    input_token.length = len;

    maj_stat = gss_accept_sec_context (&min_stat,
                                       &d->context_hdl,
                                       GSS_C_NO_CREDENTIAL,
                                       &input_token,
                                       bindings,
                                       &client_name,
                                       NULL,
                                       &output_token,
                                       NULL,
                                       NULL,
                                       &d->delegated_cred_handle);

    if (bindings != GSS_C_NO_CHANNEL_BINDINGS)
        free(bindings);

    if(output_token.length) {
        if(base64_encode(output_token.value, output_token.length, &p) < 0) {
            reply(535, "Out of memory base64-encoding.");
            return -1;
        }
        gss_release_buffer(&min_stat, &output_token);
    }
    if(maj_stat == GSS_S_COMPLETE){
        d->client_name = client_name;
        client_name = GSS_C_NO_NAME;
        if(p)
            reply(235, "ADAT=%s", p);
        else
            reply(235, "ADAT Complete");
        sec_complete = 1;

    } else if(maj_stat == GSS_S_CONTINUE_NEEDED) {
        if(p)
            reply(335, "ADAT=%s", p);
        else
            reply(335, "OK, need more data");
    } else {
        OM_uint32 new_stat;
        OM_uint32 msg_ctx = 0;
        gss_buffer_desc status_string;
        gss_display_status(&new_stat,
                           min_stat,
                           GSS_C_MECH_CODE,
                           GSS_C_NO_OID,
                           &msg_ctx,
                           &status_string);
        syslog(LOG_ERR, "gss_accept_sec_context: %.*s",
               (int)status_string.length,
               (char*)status_string.value);
        gss_release_buffer(&new_stat, &status_string);
        reply(431, "Security resource unavailable");
    }

    if (client_name)
        gss_release_name(&min_stat, &client_name);
    free(p);
    return 0;
}

int gssapi_userok(void*, char*);
int gssapi_session(void*, char*);

struct sec_server_mech gss_server_mech = {
    "GSSAPI",
    sizeof(struct gssapi_data),
    gss_init, /* init */
    NULL, /* end */
    gss_check_prot,
    gss_overhead,
    gss_encode,
    gss_decode,
    /* */
    NULL,
    gss_adat,
    NULL, /* pbsz */
    NULL, /* ccc */
    gssapi_userok,
    gssapi_session
};

#else /* FTP_SERVER */

extern struct sockaddr *hisctladdr, *myctladdr;

static int
import_name(const char *kname, const char *host, gss_name_t *target_name)
{
    OM_uint32 maj_stat, min_stat;
    gss_buffer_desc name;
    char *str;

    name.length = asprintf(&str, "%s@%s", kname, host);
    if (str == NULL) {
        printf("Out of memory\n");
        return AUTH_ERROR;
    }
    name.value = str;

    maj_stat = gss_import_name(&min_stat,
                               &name,
                               GSS_C_NT_HOSTBASED_SERVICE,
                               target_name);
    if (GSS_ERROR(maj_stat)) {
        OM_uint32 new_stat;
        OM_uint32 msg_ctx = 0;
        gss_buffer_desc status_string;

        gss_display_status(&new_stat,
                           min_stat,
                           GSS_C_MECH_CODE,
                           GSS_C_NO_OID,
                           &msg_ctx,
                           &status_string);
        printf("Error importing name %.*s: %.*s\n",
               (int)name.length,
               (char *)name.value,
               (int)status_string.length,
               (char *)status_string.value);
        free(name.value);
        gss_release_buffer(&new_stat, &status_string);
        return AUTH_ERROR;
    }
    free(name.value);
    return 0;
}

static int
gss_auth(void *app_data, char *host)
{

    OM_uint32 maj_stat, min_stat;
    gss_name_t target_name;
    gss_buffer_desc input, output_token;
    int context_established = 0;
    char *p;
    int n;
    gss_channel_bindings_t bindings;
    struct gssapi_data *d = app_data;
    OM_uint32 mech_flags = GSS_C_MUTUAL_FLAG | GSS_C_SEQUENCE_FLAG;

    const char *knames[] = { "ftp", "host", NULL }, **kname = knames;


    if(import_name(*kname++, host, &target_name))
        return AUTH_ERROR;

    input.length = 0;
    input.value = NULL;

    if (ftp_do_gss_bindings) {
        bindings = malloc(sizeof(*bindings));
        if (bindings == NULL)
            errx(1, "out of memory");

        sockaddr_to_gss_address (myctladdr,
                                 &bindings->initiator_addrtype,
                                 &bindings->initiator_address);
        sockaddr_to_gss_address (hisctladdr,
                                 &bindings->acceptor_addrtype,
                                 &bindings->acceptor_address);

        bindings->application_data.length = 0;
        bindings->application_data.value = NULL;
    } else
        bindings = GSS_C_NO_CHANNEL_BINDINGS;

    if (ftp_do_gss_delegate)
        mech_flags |= GSS_C_DELEG_FLAG;

    while(!context_established) {
        maj_stat = gss_init_sec_context(&min_stat,
                                        GSS_C_NO_CREDENTIAL,
                                        &d->context_hdl,
                                        target_name,
                                        GSS_C_NO_OID,
                                        mech_flags,
                                        0,
                                        bindings,
                                        &input,
                                        NULL,
                                        &output_token,
                                        NULL,
                                        NULL);
        if (GSS_ERROR(maj_stat)) {
            OM_uint32 new_stat;
            OM_uint32 msg_ctx = 0;
            gss_buffer_desc status_string;

            d->context_hdl = GSS_C_NO_CONTEXT;

            gss_release_name(&min_stat, &target_name);

            if(*kname != NULL) {

                if(import_name(*kname++, host, &target_name)) {
                    if (bindings != GSS_C_NO_CHANNEL_BINDINGS)
                        free(bindings);
                    return AUTH_ERROR;
                }
                continue;
            }

            if (bindings != GSS_C_NO_CHANNEL_BINDINGS)
                free(bindings);

            gss_display_status(&new_stat,
                               min_stat,
                               GSS_C_MECH_CODE,
                               GSS_C_NO_OID,
                               &msg_ctx,
                               &status_string);
            printf("Error initializing security context: %.*s\n",
                   (int)status_string.length,
                   (char*)status_string.value);
            gss_release_buffer(&new_stat, &status_string);
            return AUTH_CONTINUE;
        }

        if (input.value) {
            free(input.value);
            input.value = NULL;
            input.length = 0;
        }
        if (output_token.length != 0) {
            base64_encode(output_token.value, output_token.length, &p);
            gss_release_buffer(&min_stat, &output_token);
            n = command("ADAT %s", p);
            free(p);
        }
        if (GSS_ERROR(maj_stat)) {
            if (d->context_hdl != GSS_C_NO_CONTEXT)
                gss_delete_sec_context (&min_stat,
                                        &d->context_hdl,
                                        GSS_C_NO_BUFFER);
            break;
        }
        if (maj_stat & GSS_S_CONTINUE_NEEDED) {
            p = strstr(reply_string, "ADAT=");
            if(p == NULL){
                printf("Error: expected ADAT in reply. got: %s\n",
                       reply_string);
                if (bindings != GSS_C_NO_CHANNEL_BINDINGS)
                    free(bindings);
                return AUTH_ERROR;
            } else {
                p+=5;
                input.value = malloc(strlen(p));
                input.length = base64_decode(p, input.value);
            }
        } else {
            if(code != 235) {
                printf("Unrecognized response code: %d\n", code);
                if (bindings != GSS_C_NO_CHANNEL_BINDINGS)
                    free(bindings);
                return AUTH_ERROR;
            }
            context_established = 1;
        }
    }

    gss_release_name(&min_stat, &target_name);

    if (bindings != GSS_C_NO_CHANNEL_BINDINGS)
        free(bindings);
    if (input.value)
        free(input.value);

    {
        gss_name_t targ_name;

        maj_stat = gss_inquire_context(&min_stat,
                                       d->context_hdl,
                                       NULL,
                                       &targ_name,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL);
        if (GSS_ERROR(maj_stat) == 0) {
            gss_buffer_desc name;
            maj_stat = gss_display_name (&min_stat,
                                         targ_name,
                                         &name,
                                         NULL);
            if (GSS_ERROR(maj_stat) == 0) {
                printf("Authenticated to <%.*s>\n",
                        (int)name.length,
                        (char *)name.value);
                gss_release_buffer(&min_stat, &name);
            }
            gss_release_name(&min_stat, &targ_name);
        } else
            printf("Failed to get gss name of peer.\n");
    }


    return AUTH_OK;
}

struct sec_client_mech gss_client_mech = {
    "GSSAPI",
    sizeof(struct gssapi_data),
    gss_init,
    gss_auth,
    NULL, /* end */
    gss_check_prot,
    gss_overhead,
    gss_encode,
    gss_decode,
};

#endif /* FTP_SERVER */