/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005 Doug Rabson
 * 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 AUTHOR 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 AUTHOR 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 <gssapi/gssapi.h>
#include <ctype.h>
#include <dlfcn.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "mech_switch.h"
#include "utils.h"

#ifndef _PATH_GSS_MECH
#define _PATH_GSS_MECH  "/etc/gss/mech"
#endif

struct _gss_mech_switch_list _gss_mechs =
        SLIST_HEAD_INITIALIZER(_gss_mechs);
gss_OID_set _gss_mech_oids;

/*
 * Convert a string containing an OID in 'dot' form
 * (e.g. 1.2.840.113554.1.2.2) to a gss_OID.
 */
static int
_gss_string_to_oid(const char* s, gss_OID oid)
{
        int                     number_count, i, j;
        int                     byte_count;
        const char              *p, *q;
        char                    *res;

        oid->length = 0;
        oid->elements = NULL;

        /*
         * First figure out how many numbers in the oid, then
         * calculate the compiled oid size.
         */
        number_count = 0;
        for (p = s; p; p = q) {
                q = strchr(p, '.');
                if (q) q = q + 1;
                number_count++;
        }

        /*
         * The first two numbers are in the first byte and each
         * subsequent number is encoded in a variable byte sequence.
         */
        if (number_count < 2)
                return (EINVAL);

        /*
         * We do this in two passes. The first pass, we just figure
         * out the size. Second time around, we actually encode the
         * number.
         */
        res = NULL;
        for (i = 0; i < 2; i++) {
                byte_count = 0;
                for (p = s, j = 0; p; p = q, j++) {
                        unsigned int number = 0;

                        /*
                         * Find the end of this number.
                         */
                        q = strchr(p, '.');
                        if (q) q = q + 1;

                        /*
                         * Read the number of of the string. Don't
                         * bother with anything except base ten.
                         */
                        while (*p && *p != '.') {
                                number = 10 * number + (*p - '0');
                                p++;
                        }

                        /*
                         * Encode the number. The first two numbers
                         * are packed into the first byte. Subsequent
                         * numbers are encoded in bytes seven bits at
                         * a time with the last byte having the high
                         * bit set.
                         */
                        if (j == 0) {
                                if (res)
                                        *res = number * 40;
                        } else if (j == 1) {
                                if (res) {
                                        *res += number;
                                        res++;
                                }
                                byte_count++;
                        } else if (j >= 2) {
                                /*
                                 * The number is encoded in seven bit chunks.
                                 */
                                unsigned int t;
                                int bytes;

                                bytes = 0;
                                for (t = number; t; t >>= 7)
                                        bytes++;
                                if (bytes == 0) bytes = 1;
                                while (bytes) {
                                        if (res) {
                                                int bit = 7*(bytes-1);

                                                *res = (number >> bit) & 0x7f;
                                                if (bytes != 1)
                                                        *res |= 0x80;
                                                res++;
                                        }
                                        byte_count++;
                                        bytes--;
                                }
                        }
                }
                if (!res) {
                        res = malloc(byte_count);
                        if (!res)
                                return (ENOMEM);
                        oid->length = byte_count;
                        oid->elements = res;
                }
        }

        return (0);
}


#define SYM(name)                                               \
do {                                                            \
        snprintf(buf, sizeof(buf), "%s_%s",                     \
            m->gm_name_prefix, #name);                          \
        m->gm_ ## name = dlsym(so, buf);                        \
        if (!m->gm_ ## name) {                                  \
                fprintf(stderr, "can't find symbol %s\n", buf); \
                goto bad;                                       \
        }                                                       \
} while (0)

#define OPTSYM(name)                            \
do {                                            \
        snprintf(buf, sizeof(buf), "%s_%s",     \
            m->gm_name_prefix, #name);          \
        m->gm_ ## name = dlsym(so, buf);        \
} while (0)

/*
 * Load the mechanisms file (/etc/gss/mech).
 */
void
_gss_load_mech(void)
{
        OM_uint32       major_status, minor_status;
        FILE            *fp;
        char            buf[256];
        char            *p;
        char            *name, *oid, *lib, *kobj;
        struct _gss_mech_switch *m;
        void            *so;
        const char      *(*prefix_fn)(void);

        if (SLIST_FIRST(&_gss_mechs))
                return;

        major_status = gss_create_empty_oid_set(&minor_status,
            &_gss_mech_oids);
        if (major_status)
                return;

        fp = fopen(_PATH_GSS_MECH, "r");
        if (!fp) {
                perror(_PATH_GSS_MECH);
                return;
        }

        while (fgets(buf, sizeof(buf), fp)) {
                if (*buf == '#')
                        continue;
                p = buf;
                name = strsep(&p, "\t\n ");
                if (p) while (isspace(*p)) p++;
                oid = strsep(&p, "\t\n ");
                if (p) while (isspace(*p)) p++;
                lib = strsep(&p, "\t\n ");
                if (p) while (isspace(*p)) p++;
                kobj = strsep(&p, "\t\n ");
                if (!name || !oid || !lib || !kobj)
                        continue;

                so = dlopen(lib, RTLD_LOCAL);
                if (!so) {
                        fprintf(stderr, "dlopen: %s\n", dlerror());
                        continue;
                }

                m = malloc(sizeof(struct _gss_mech_switch));
                if (!m)
                        break;
                m->gm_so = so;
                if (_gss_string_to_oid(oid, &m->gm_mech_oid)) {
                        free(m);
                        continue;
                }

                prefix_fn = (const char *(*)(void))
                        dlsym(so, "_gss_name_prefix");
                if (prefix_fn)
                        m->gm_name_prefix = prefix_fn();
                else
                        m->gm_name_prefix = "gss";

                major_status = gss_add_oid_set_member(&minor_status,
                    &m->gm_mech_oid, &_gss_mech_oids);
                if (major_status) {
                        free(m->gm_mech_oid.elements);
                        free(m);
                        continue;
                }

                SYM(acquire_cred);
                SYM(release_cred);
                SYM(init_sec_context);
                SYM(accept_sec_context);
                SYM(process_context_token);
                SYM(delete_sec_context);
                SYM(context_time);
                SYM(get_mic);
                SYM(verify_mic);
                SYM(wrap);
                SYM(unwrap);
                SYM(display_status);
                OPTSYM(indicate_mechs);
                SYM(compare_name);
                SYM(display_name);
                SYM(import_name);
                SYM(export_name);
                SYM(release_name);
                SYM(inquire_cred);
                SYM(inquire_context);
                SYM(wrap_size_limit);
                SYM(add_cred);
                SYM(inquire_cred_by_mech);
                SYM(export_sec_context);
                SYM(import_sec_context);
                SYM(inquire_names_for_mech);
                SYM(inquire_mechs_for_name);
                SYM(canonicalize_name);
                SYM(duplicate_name);
                OPTSYM(inquire_sec_context_by_oid);
                OPTSYM(inquire_cred_by_oid);
                OPTSYM(set_sec_context_option);
                OPTSYM(set_cred_option);
                OPTSYM(pseudo_random);
                OPTSYM(pname_to_uid);

                SLIST_INSERT_HEAD(&_gss_mechs, m, gm_link);
                continue;

        bad:
                free(m->gm_mech_oid.elements);
                free(m);
                dlclose(so);
                continue;
        }
        fclose(fp);
}

struct _gss_mech_switch *
_gss_find_mech_switch(gss_OID mech)
{
        struct _gss_mech_switch *m;

        _gss_load_mech();
        SLIST_FOREACH(m, &_gss_mechs, gm_link) {
                if (gss_oid_equal(&m->gm_mech_oid, mech))
                        return m;
        }
        return (0);
}