/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */

/* lib/krad/packet.c - Packet functions for libkrad */

/*

 * Copyright 2013 Red Hat, Inc.  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.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER

 * 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.

 */

#include "internal.h"

#include <string.h>

#include <arpa/inet.h>

typedef unsigned char uchar;

/* RFC 2865 */

#define OFFSET_CODE 0

#define OFFSET_ID 1

#define OFFSET_LENGTH 2

#define OFFSET_AUTH 4

#define OFFSET_ATTR 20

#define AUTH_FIELD_SIZE (OFFSET_ATTR - OFFSET_AUTH)

#define offset(d, o) (&(d)->data[o])

#define pkt_code_get(p) (*(krad_code *)offset(&(p)->pkt, OFFSET_CODE))

#define pkt_code_set(p, v) (*(krad_code *)offset(&(p)->pkt, OFFSET_CODE)) = v

#define pkt_id_get(p) (*(uchar *)offset(&(p)->pkt, OFFSET_ID))

#define pkt_id_set(p, v) (*(uchar *)offset(&(p)->pkt, OFFSET_ID)) = v

#define pkt_len_get(p)  load_16_be(offset(&(p)->pkt, OFFSET_LENGTH))

#define pkt_len_set(p, v)  store_16_be(v, offset(&(p)->pkt, OFFSET_LENGTH))

#define pkt_auth(p) ((uchar *)offset(&(p)->pkt, OFFSET_AUTH))

#define pkt_attr(p) ((unsigned char *)offset(&(p)->pkt, OFFSET_ATTR))

struct krad_packet_st {

    char buffer[KRAD_PACKET_SIZE_MAX];

    krad_attrset *attrset;

    krb5_data pkt;

};

typedef struct {

    uchar x[(UCHAR_MAX + 1) / 8];

} idmap;

/* Ensure the map is empty. */

static inline void

idmap_init(idmap *map)

{

    memset(map, 0, sizeof(*map));

}

/* Set an id as already allocated. */

static inline void

idmap_set(idmap *map, uchar id)

{

    map->x[id / 8] |= 1 << (id % 8);

}

/* Determine whether or not an id is used. */

static inline krb5_boolean

idmap_isset(const idmap *map, uchar id)

{

    return (map->x[id / 8] & (1 << (id % 8))) != 0;

}

/* Find an unused id starting the search at the value specified in id.

 * NOTE: For optimal security, the initial value of id should be random. */

static inline krb5_error_code

idmap_find(const idmap *map, uchar *id)

{

    krb5_int16 i;

    for (i = *id; i >= 0 && i <= UCHAR_MAX; (*id % 2 == 0) ? i++ : i--) {

        if (!idmap_isset(map, i))

            goto success;

    }

    for (i = *id; i >= 0 && i <= UCHAR_MAX; (*id % 2 == 1) ? i++ : i--) {

        if (!idmap_isset(map, i))

            goto success;

    }

    return ERANGE;

success:

    *id = i;

    return 0;

}

/* Generate size bytes of random data into the buffer. */

static inline krb5_error_code

randomize(krb5_context ctx, void *buffer, unsigned int size)

{

    krb5_data rdata = make_data(buffer, size);

    return krb5_c_random_make_octets(ctx, &rdata);

}

/* Generate a radius packet id. */

static krb5_error_code

id_generate(krb5_context ctx, krad_packet_iter_cb cb, void *data, uchar *id)

{

    krb5_error_code retval;

    const krad_packet *tmp;

    idmap used;

    uchar i;

    retval = randomize(ctx, &i, sizeof(i));

    if (retval != 0) {

        if (cb != NULL)

            (*cb)(data, TRUE);

        return retval;

    }

    if (cb != NULL) {

        idmap_init(&used);

        for (tmp = (*cb)(data, FALSE); tmp != NULL; tmp = (*cb)(data, FALSE))

            idmap_set(&used, tmp->pkt.data[1]);

        retval = idmap_find(&used, &i);

        if (retval != 0)

            return retval;

    }

    *id = i;

    return 0;

}

/* Generate a random authenticator field. */

static krb5_error_code

auth_generate_random(krb5_context ctx, uchar *rauth)

{

    krb5_ui_4 trunctime;

    time_t currtime;

    /* Get the least-significant four bytes of the current time. */

    currtime = time(NULL);

    if (currtime == (time_t)-1)

        return errno;

    trunctime = (krb5_ui_4)currtime;

    memcpy(rauth, &trunctime, sizeof(trunctime));

    /* Randomize the rest of the buffer. */

    return randomize(ctx, rauth + sizeof(trunctime),

                     AUTH_FIELD_SIZE - sizeof(trunctime));

}

/* Generate a response authenticator field. */

static krb5_error_code

auth_generate_response(krb5_context ctx, const char *secret,

                       const krad_packet *response, const uchar *auth,

                       uchar *rauth)

{

    krb5_error_code retval;

    krb5_checksum hash;

    krb5_data data;

    /* Allocate the temporary buffer. */

    retval = alloc_data(&data, response->pkt.length + strlen(secret));

    if (retval != 0)

        return retval;

    /* Encoded RADIUS packet with the request's

     * authenticator and the secret at the end. */

    memcpy(data.data, response->pkt.data, response->pkt.length);

    memcpy(data.data + OFFSET_AUTH, auth, AUTH_FIELD_SIZE);

    memcpy(data.data + response->pkt.length, secret, strlen(secret));

    /* Hash it. */

    retval = krb5_c_make_checksum(ctx, CKSUMTYPE_RSA_MD5, NULL, 0, &data,

                                  &hash);

    free(data.data);

    if (retval != 0)

        return retval;

    memcpy(rauth, hash.contents, AUTH_FIELD_SIZE);

    krb5_free_checksum_contents(ctx, &hash);

    return 0;

}

/* Create a new packet. */

static krad_packet *

packet_new()

{

    krad_packet *pkt;

    pkt = calloc(1, sizeof(krad_packet));

    if (pkt == NULL)

        return NULL;

    pkt->pkt = make_data(pkt->buffer, sizeof(pkt->buffer));

    return pkt;

}

/* Set the attrset object by decoding the packet. */

static krb5_error_code

packet_set_attrset(krb5_context ctx, const char *secret, krad_packet *pkt)

{

    krb5_data tmp;

    tmp = make_data(pkt_attr(pkt), pkt->pkt.length - OFFSET_ATTR);

    return kr_attrset_decode(ctx, &tmp, secret, pkt_auth(pkt), &pkt->attrset);

}

ssize_t

krad_packet_bytes_needed(const krb5_data *buffer)

{

    size_t len;

    if (buffer->length < OFFSET_AUTH)

        return OFFSET_AUTH - buffer->length;

    len = load_16_be(offset(buffer, OFFSET_LENGTH));

    if (len > KRAD_PACKET_SIZE_MAX)

        return -1;

    return (buffer->length > len) ? 0 : len - buffer->length;

}

void

krad_packet_free(krad_packet *pkt)

{

    if (pkt)

        krad_attrset_free(pkt->attrset);

    free(pkt);

}

/* Create a new request packet. */

krb5_error_code

krad_packet_new_request(krb5_context ctx, const char *secret, krad_code code,

                        const krad_attrset *set, krad_packet_iter_cb cb,

                        void *data, krad_packet **request)

{

    krb5_error_code retval;

    krad_packet *pkt;

    uchar id;

    size_t attrset_len;

    pkt = packet_new();

    if (pkt == NULL) {

        if (cb != NULL)

            (*cb)(data, TRUE);

        return ENOMEM;

    }

    /* Generate the ID. */

    retval = id_generate(ctx, cb, data, &id;;

    if (retval != 0)

        goto error;

    pkt_id_set(pkt, id);

    /* Generate the authenticator. */

    retval = auth_generate_random(ctx, pkt_auth(pkt));

    if (retval != 0)

        goto error;

    /* Encode the attributes. */

    retval = kr_attrset_encode(set, secret, pkt_auth(pkt), pkt_attr(pkt),

                               &attrset_len);

    if (retval != 0)

        goto error;

    /* Set the code, ID and length. */

    pkt->pkt.length = attrset_len + OFFSET_ATTR;

    pkt_code_set(pkt, code);

    pkt_len_set(pkt, pkt->pkt.length);

    /* Copy the attrset for future use. */

    retval = packet_set_attrset(ctx, secret, pkt);

    if (retval != 0)

        goto error;

    *request = pkt;

    return 0;

error:

    free(pkt);

    return retval;

}

/* Create a new request packet. */

krb5_error_code

krad_packet_new_response(krb5_context ctx, const char *secret, krad_code code,

                         const krad_attrset *set, const krad_packet *request,

                         krad_packet **response)

{

    krb5_error_code retval;

    krad_packet *pkt;

    size_t attrset_len;

    pkt = packet_new();

    if (pkt == NULL)

        return ENOMEM;

    /* Encode the attributes. */

    retval = kr_attrset_encode(set, secret, pkt_auth(request), pkt_attr(pkt),

                               &attrset_len);

    if (retval != 0)

        goto error;

    /* Set the code, ID and length. */

    pkt->pkt.length = attrset_len + OFFSET_ATTR;

    pkt_code_set(pkt, code);

    pkt_id_set(pkt, pkt_id_get(request));

    pkt_len_set(pkt, pkt->pkt.length);

    /* Generate the authenticator. */

    retval = auth_generate_response(ctx, secret, pkt, pkt_auth(request),

                                    pkt_auth(pkt));

    if (retval != 0)

        goto error;

    /* Copy the attrset for future use. */

    retval = packet_set_attrset(ctx, secret, pkt);

    if (retval != 0)

        goto error;

    *response = pkt;

    return 0;

error:

    free(pkt);

    return retval;

}

/* Decode a packet. */

static krb5_error_code

decode_packet(krb5_context ctx, const char *secret, const krb5_data *buffer,

              krad_packet **pkt)

{

    krb5_error_code retval;

    krad_packet *tmp;

    krb5_ui_2 len;

    tmp = packet_new();

    if (tmp == NULL) {

        retval = ENOMEM;

        goto error;

    }

    /* Ensure a proper message length. */

    retval = (buffer->length < OFFSET_ATTR) ? EMSGSIZE : 0;

    if (retval != 0)

        goto error;

    len = load_16_be(offset(buffer, OFFSET_LENGTH));

    retval = (len < OFFSET_ATTR) ? EBADMSG : 0;

    if (retval != 0)

        goto error;

    retval = (len > buffer->length || len > tmp->pkt.length) ? EBADMSG : 0;

    if (retval != 0)

        goto error;

    /* Copy over the buffer. */

    tmp->pkt.length = len;

    memcpy(tmp->pkt.data, buffer->data, len);

    /* Parse the packet to ensure it is well-formed. */

    retval = packet_set_attrset(ctx, secret, tmp);

    if (retval != 0)

        goto error;

    *pkt = tmp;

    return 0;

error:

    krad_packet_free(tmp);

    return retval;

}

krb5_error_code

krad_packet_decode_request(krb5_context ctx, const char *secret,

                           const krb5_data *buffer, krad_packet_iter_cb cb,

                           void *data, const krad_packet **duppkt,

                           krad_packet **reqpkt)

{

    const krad_packet *tmp = NULL;

    krb5_error_code retval;

    retval = decode_packet(ctx, secret, buffer, reqpkt);

    if (cb != NULL && retval == 0) {

        for (tmp = (*cb)(data, FALSE); tmp != NULL; tmp = (*cb)(data, FALSE)) {

            if (pkt_id_get(*reqpkt) == pkt_id_get(tmp))

                break;

        }

    }

    if (cb != NULL && (retval != 0 || tmp != NULL))

        (*cb)(data, TRUE);

    *duppkt = tmp;

    return retval;

}

krb5_error_code

krad_packet_decode_response(krb5_context ctx, const char *secret,

                            const krb5_data *buffer, krad_packet_iter_cb cb,

                            void *data, const krad_packet **reqpkt,

                            krad_packet **rsppkt)

{

    uchar auth[AUTH_FIELD_SIZE];

    const krad_packet *tmp = NULL;

    krb5_error_code retval;

    retval = decode_packet(ctx, secret, buffer, rsppkt);

    if (cb != NULL && retval == 0) {

        for (tmp = (*cb)(data, FALSE); tmp != NULL; tmp = (*cb)(data, FALSE)) {

            if (pkt_id_get(*rsppkt) != pkt_id_get(tmp))

                continue;

            /* Response */

            retval = auth_generate_response(ctx, secret, *rsppkt,

                                            pkt_auth(tmp), auth);

            if (retval != 0) {

                krad_packet_free(*rsppkt);

                break;

            }

            /* If the authenticator matches, then the response is valid. */

            if (memcmp(pkt_auth(*rsppkt), auth, sizeof(auth)) == 0)

                break;

        }

    }

    if (cb != NULL && (retval != 0 || tmp != NULL))

        (*cb)(data, TRUE);

    *reqpkt = tmp;

    return retval;

}

const krb5_data *

krad_packet_encode(const krad_packet *pkt)

{

    return &pkt->pkt;

}

krad_code

krad_packet_get_code(const krad_packet *pkt)

{

    if (pkt == NULL)

        return 0;

    return pkt_code_get(pkt);

}

const krb5_data *

krad_packet_get_attr(const krad_packet *pkt, krad_attr type, size_t indx)

{

    return krad_attrset_get(pkt->attrset, type, indx);

}