/*
 * Copyright (c) 1997 - 2001, 2003 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.
 */

#include "krb5_locl.h"

/* this is an attempt at one of the most horrible `compression'
   schemes that has ever been invented; it's so amazingly brain-dead
   that words can not describe it, and all this just to save a few
   silly bytes */

struct tr_realm {
    char *realm;
    unsigned leading_space:1;
    unsigned leading_slash:1;
    unsigned trailing_dot:1;
    struct tr_realm *next;
};

static void
free_realms(struct tr_realm *r)
{
    struct tr_realm *p;
    while(r){
        p = r;
        r = r->next;
        free(p->realm);
        free(p);
    }
}

static int
make_path(krb5_context context, struct tr_realm *r,
          const char *from, const char *to)
{
    struct tr_realm *tmp;
    const char *p;

    if(strlen(from) < strlen(to)){
        const char *str;
        str = from;
        from = to;
        to = str;
    }

    if(strcmp(from + strlen(from) - strlen(to), to) == 0){
        p = from;
        while(1){
            p = strchr(p, '.');
            if(p == NULL) {
                krb5_clear_error_message (context);
                return KRB5KDC_ERR_POLICY;
            }
            p++;
            if(strcmp(p, to) == 0)
                break;
            tmp = calloc(1, sizeof(*tmp));
            if(tmp == NULL)
                return krb5_enomem(context);
            tmp->next = r->next;
            r->next = tmp;
            tmp->realm = strdup(p);
            if(tmp->realm == NULL){
                r->next = tmp->next;
                free(tmp);
                return krb5_enomem(context);
            }
        }
    }else if(strncmp(from, to, strlen(to)) == 0){
        p = from + strlen(from);
        while(1){
            while(p >= from && *p != '/') p--;
            if(p == from)
                return KRB5KDC_ERR_POLICY;

            if(strncmp(to, from, p - from) == 0)
                break;
            tmp = calloc(1, sizeof(*tmp));
            if(tmp == NULL)
                return krb5_enomem(context);
            tmp->next = r->next;
            r->next = tmp;
            tmp->realm = malloc(p - from + 1);
            if(tmp->realm == NULL){
                r->next = tmp->next;
                free(tmp);
                return krb5_enomem(context);
            }
            memcpy(tmp->realm, from, p - from);
            tmp->realm[p - from] = '\0';
            p--;
        }
    } else {
        krb5_clear_error_message (context);
        return KRB5KDC_ERR_POLICY;
    }

    return 0;
}

static int
make_paths(krb5_context context,
           struct tr_realm *realms, const char *client_realm,
           const char *server_realm)
{
    struct tr_realm *r;
    int ret;
    const char *prev_realm = client_realm;
    const char *next_realm = NULL;
    for(r = realms; r; r = r->next){
        /* it *might* be that you can have more than one empty
           component in a row, at least that's how I interpret the
           "," exception in 1510 */
        if(r->realm[0] == '\0'){
            while(r->next && r->next->realm[0] == '\0')
                r = r->next;
            if(r->next)
                next_realm = r->next->realm;
            else
                next_realm = server_realm;
            ret = make_path(context, r, prev_realm, next_realm);
            if(ret){
                free_realms(realms);
                return ret;
            }
        }
        prev_realm = r->realm;
    }
    return 0;
}

static int
expand_realms(krb5_context context,
              struct tr_realm *realms, const char *client_realm)
{
    struct tr_realm *r;
    const char *prev_realm = NULL;
    for(r = realms; r; r = r->next){
        if(r->trailing_dot){
            char *tmp;
            size_t len;

            if(prev_realm == NULL)
                prev_realm = client_realm;

            len = strlen(r->realm) + strlen(prev_realm) + 1;

            tmp = realloc(r->realm, len);
            if(tmp == NULL){
                free_realms(realms);
                return krb5_enomem(context);
            }
            r->realm = tmp;
            strlcat(r->realm, prev_realm, len);
        }else if(r->leading_slash && !r->leading_space && prev_realm){
            /* yet another exception: if you use x500-names, the
               leading realm doesn't have to be "quoted" with a space */
            char *tmp;
            size_t len = strlen(r->realm) + strlen(prev_realm) + 1;

            tmp = malloc(len);
            if(tmp == NULL){
                free_realms(realms);
                return krb5_enomem(context);
            }
            strlcpy(tmp, prev_realm, len);
            strlcat(tmp, r->realm, len);
            free(r->realm);
            r->realm = tmp;
        }
        prev_realm = r->realm;
    }
    return 0;
}

static struct tr_realm *
make_realm(char *realm)
{
    struct tr_realm *r;
    char *p, *q;
    int quote = 0;
    r = calloc(1, sizeof(*r));
    if(r == NULL){
        free(realm);
        return NULL;
    }
    r->realm = realm;
    for(p = q = r->realm; *p; p++){
        if(p == r->realm && *p == ' '){
            r->leading_space = 1;
            continue;
        }
        if(q == r->realm && *p == '/')
            r->leading_slash = 1;
        if(quote){
            *q++ = *p;
            quote = 0;
            continue;
        }
        if(*p == '\\'){
            quote = 1;
            continue;
        }
        if(p[0] == '.' && p[1] == '\0')
            r->trailing_dot = 1;
        *q++ = *p;
    }
    *q = '\0';
    return r;
}

static struct tr_realm*
append_realm(struct tr_realm *head, struct tr_realm *r)
{
    struct tr_realm *p;
    if(head == NULL){
        r->next = NULL;
        return r;
    }
    p = head;
    while(p->next) p = p->next;
    p->next = r;
    return head;
}

static int
decode_realms(krb5_context context,
              const char *tr, int length, struct tr_realm **realms)
{
    struct tr_realm *r = NULL;

    char *tmp;
    int quote = 0;
    const char *start = tr;
    int i;

    for(i = 0; i < length; i++){
        if(quote){
            quote = 0;
            continue;
        }
        if(tr[i] == '\\'){
            quote = 1;
            continue;
        }
        if(tr[i] == ','){
            tmp = malloc(tr + i - start + 1);
            if(tmp == NULL)
                return krb5_enomem(context);
            memcpy(tmp, start, tr + i - start);
            tmp[tr + i - start] = '\0';
            r = make_realm(tmp);
            if(r == NULL){
                free_realms(*realms);
                *realms = NULL;
                return krb5_enomem(context);
            }
            *realms = append_realm(*realms, r);
            start = tr + i + 1;
        }
    }
    tmp = malloc(tr + i - start + 1);
    if(tmp == NULL){
        free_realms(*realms);
        *realms = NULL;
        return krb5_enomem(context);
    }
    memcpy(tmp, start, tr + i - start);
    tmp[tr + i - start] = '\0';
    r = make_realm(tmp);
    if(r == NULL){
        free_realms(*realms);
        *realms = NULL;
        return krb5_enomem(context);
    }
    *realms = append_realm(*realms, r);

    return 0;
}


KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_domain_x500_decode(krb5_context context,
                        krb5_data tr, char ***realms, unsigned int *num_realms,
                        const char *client_realm, const char *server_realm)
{
    struct tr_realm *r = NULL;
    struct tr_realm *p, **q;
    int ret;

    if(tr.length == 0) {
        *realms = NULL;
        *num_realms = 0;
        return 0;
    }

    /* split string in components */
    ret = decode_realms(context, tr.data, tr.length, &r);
    if(ret)
        return ret;

    /* apply prefix rule */
    ret = expand_realms(context, r, client_realm);
    if(ret)
        return ret;

    ret = make_paths(context, r, client_realm, server_realm);
    if(ret)
        return ret;

    /* remove empty components and count realms */
    *num_realms = 0;
    for(q = &r; *q; ){
        if((*q)->realm[0] == '\0'){
            p = *q;
            *q = (*q)->next;
            free(p->realm);
            free(p);
        }else{
            q = &(*q)->next;
            (*num_realms)++;
        }
    }
    if (*num_realms + 1 > UINT_MAX/sizeof(**realms))
        return ERANGE;

    {
        char **R;
        R = malloc((*num_realms + 1) * sizeof(*R));
        if (R == NULL)
            return krb5_enomem(context);
        *realms = R;
        while(r){
            *R++ = r->realm;
            p = r->next;
            free(r);
            r = p;
        }
    }
    return 0;
}

KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_domain_x500_encode(char **realms, unsigned int num_realms,
                        krb5_data *encoding)
{
    char *s = NULL;
    int len = 0;
    unsigned int i;
    krb5_data_zero(encoding);
    if (num_realms == 0)
        return 0;
    for(i = 0; i < num_realms; i++){
        len += strlen(realms[i]);
        if(realms[i][0] == '/')
            len++;
    }
    len += num_realms - 1;
    s = malloc(len + 1);
    if (s == NULL)
        return ENOMEM;
    *s = '\0';
    for(i = 0; i < num_realms; i++){
        if(i)
            strlcat(s, ",", len + 1);
        if(realms[i][0] == '/')
            strlcat(s, " ", len + 1);
        strlcat(s, realms[i], len + 1);
    }
    encoding->data = s;
    encoding->length = strlen(s);
    return 0;
}

KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_check_transited(krb5_context context,
                     krb5_const_realm client_realm,
                     krb5_const_realm server_realm,
                     krb5_realm *realms,
                     unsigned int num_realms,
                     int *bad_realm)
{
    char **tr_realms;
    char **p;
    size_t i;

    if(num_realms == 0)
        return 0;

    tr_realms = krb5_config_get_strings(context, NULL,
                                        "capaths",
                                        client_realm,
                                        server_realm,
                                        NULL);
    for(i = 0; i < num_realms; i++) {
        for(p = tr_realms; p && *p; p++) {
            if(strcmp(*p, realms[i]) == 0)
                break;
        }
        if(p == NULL || *p == NULL) {
            krb5_config_free_strings(tr_realms);
            krb5_set_error_message (context, KRB5KRB_AP_ERR_ILL_CR_TKT,
                                    N_("no transit allowed "
                                       "through realm %s", ""),
                                    realms[i]);
            if(bad_realm)
                *bad_realm = i;
            return KRB5KRB_AP_ERR_ILL_CR_TKT;
        }
    }
    krb5_config_free_strings(tr_realms);
    return 0;
}

KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_check_transited_realms(krb5_context context,
                            const char *const *realms,
                            unsigned int num_realms,
                            int *bad_realm)
{
    size_t i;
    int ret = 0;
    char **bad_realms = krb5_config_get_strings(context, NULL,
                                                "libdefaults",
                                                "transited_realms_reject",
                                                NULL);
    if(bad_realms == NULL)
        return 0;

    for(i = 0; i < num_realms; i++) {
        char **p;
        for(p = bad_realms; *p; p++)
            if(strcmp(*p, realms[i]) == 0) {
                ret = KRB5KRB_AP_ERR_ILL_CR_TKT;
                krb5_set_error_message (context, ret,
                                        N_("no transit allowed "
                                           "through realm %s", ""),
                                        *p);
                if(bad_realm)
                    *bad_realm = i;
                break;
            }
    }
    krb5_config_free_strings(bad_realms);
    return ret;
}

#if 0
int
main(int argc, char **argv)
{
    krb5_data x;
    char **r;
    int num, i;
    x.data = argv[1];
    x.length = strlen(x.data);
    if(domain_expand(x, &r, &num, argv[2], argv[3]))
        exit(1);
    for(i = 0; i < num; i++)
        printf("%s\n", r[i]);
    return 0;
}
#endif