/*
 *  ircd-ratbox: A slightly useful ircd.
 *  m_challenge.c: Allows an IRC Operator to securely authenticate.
 *
 *  Copyright (C) 1990 Jarkko Oikarinen and University of Oulu, Co Center
 *  Copyright (C) 1996-2002 Hybrid Development Team
 *  Copyright (C) 2002-2005 ircd-ratbox development team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 *  USA
 *
 */

#include "stdinc.h"

#ifdef HAVE_LIBCRYPTO
#include <openssl/pem.h>
#include <openssl/rand.h>
#include <openssl/rsa.h>
#include <openssl/md5.h>
#include <openssl/bn.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#endif

#include "client.h"
#include "ircd.h"
#include "modules.h"
#include "numeric.h"
#include "send.h"
#include "s_conf.h"
#include "msg.h"
#include "parse.h"
#include "match.h"
#include "logger.h"
#include "s_user.h"
#include "cache.h"
#include "s_newconf.h"

#define CHALLENGE_WIDTH BUFSIZE - (NICKLEN + HOSTLEN + 12)
#define CHALLENGE_EXPIRES	180	/* 180 seconds should be more than long enough */
#define CHALLENGE_SECRET_LENGTH	128	/* how long our challenge secret should be */

#ifndef HAVE_LIBCRYPTO
/* Maybe this should be an error or something?-davidt */
/* now it is	-larne	*/
static int	challenge_load(void)
{
#ifndef STATIC_MODULES
    sendto_realops_snomask(SNO_GENERAL, L_ALL,
                           "Challenge module not loaded because OpenSSL is not available.");
    ilog(L_MAIN, "Challenge module not loaded because OpenSSL is not available.");
    return -1;
#else
    return 0;
#endif
}

DECLARE_MODULE_AV1(challenge, challenge_load, NULL, NULL, NULL, NULL, "$Revision: 3161 $");
#else

static int m_challenge(struct Client *, struct Client *, int, const char **);

/* We have openssl support, so include /CHALLENGE */
struct Message challenge_msgtab = {
    "CHALLENGE", 0, 0, 0, MFLG_SLOW,
    {mg_unreg, {m_challenge, 2}, mg_ignore, mg_ignore, mg_ignore, {m_challenge, 2}}
};

mapi_clist_av1 challenge_clist[] = { &challenge_msgtab, NULL };
DECLARE_MODULE_AV1(challenge, NULL, NULL, challenge_clist, NULL, NULL, "$Revision: 3161 $");

static int generate_challenge(char **r_challenge, char **r_response, RSA * key);

static void
cleanup_challenge(struct Client *target_p)
{
    if(target_p->localClient == NULL)
        return;

    rb_free(target_p->localClient->challenge);
    rb_free(target_p->localClient->opername);
    target_p->localClient->challenge = NULL;
    target_p->localClient->opername = NULL;
    target_p->localClient->chal_time = 0;
}

/*
 * m_challenge - generate RSA challenge for wouldbe oper
 * parv[1] = operator to challenge for, or +response
 *
 */
static int
m_challenge(struct Client *client_p, struct Client *source_p, int parc, const char *parv[])
{
    struct oper_conf *oper_p;
    char *challenge = NULL; /* to placate gcc */
    char chal_line[CHALLENGE_WIDTH];
    unsigned char *b_response;
    size_t cnt;
    int len = 0;

    /* if theyre an oper, reprint oper motd and ignore */
    if(IsOper(source_p)) {
        sendto_one(source_p, form_str(RPL_YOUREOPER), me.name, source_p->name);
        send_oper_motd(source_p);
        return 0;
    }

    if(*parv[1] == '+') {
        /* Ignore it if we aren't expecting this... -A1kmm */
        if(!source_p->localClient->challenge)
            return 0;

        if((rb_current_time() - source_p->localClient->chal_time) > CHALLENGE_EXPIRES) {
            sendto_one(source_p, form_str(ERR_PASSWDMISMATCH), me.name, source_p->name);
            ilog(L_FOPER, "EXPIRED CHALLENGE (%s) by (%s!%s@%s) (%s)",
                 source_p->localClient->opername, source_p->name,
                 source_p->username, source_p->host, source_p->sockhost);

            if(ConfigFileEntry.failed_oper_notice)
                sendto_realops_snomask(SNO_GENERAL, L_NETWIDE,
                                       "Expired CHALLENGE attempt by %s (%s@%s)",
                                       source_p->name, source_p->username,
                                       source_p->host);
            cleanup_challenge(source_p);
            return 0;
        }

        parv[1]++;
        b_response = rb_base64_decode((const unsigned char *)parv[1], strlen(parv[1]), &len);

        if(len != SHA_DIGEST_LENGTH ||
           memcmp(source_p->localClient->challenge, b_response, SHA_DIGEST_LENGTH)) {
            sendto_one(source_p, form_str(ERR_PASSWDMISMATCH), me.name, source_p->name);
            ilog(L_FOPER, "FAILED CHALLENGE (%s) by (%s!%s@%s) (%s)",
                 source_p->localClient->opername, source_p->name,
                 source_p->username, source_p->host, source_p->sockhost);

            if(ConfigFileEntry.failed_oper_notice)
                sendto_realops_snomask(SNO_GENERAL, L_NETWIDE,
                                       "Failed CHALLENGE attempt by %s (%s@%s)",
                                       source_p->name, source_p->username,
                                       source_p->host);

            rb_free(b_response);
            cleanup_challenge(source_p);
            return 0;
        }

        rb_free(b_response);

        oper_p = find_oper_conf(source_p->username, source_p->orighost,
                                source_p->sockhost,
                                source_p->localClient->opername);

        if(oper_p == NULL) {
            sendto_one_numeric(source_p, ERR_NOOPERHOST, form_str(ERR_NOOPERHOST));
            ilog(L_FOPER, "FAILED OPER (%s) by (%s!%s@%s) (%s)",
                 source_p->localClient->opername, source_p->name,
                 source_p->username, source_p->host,
                 source_p->sockhost);

            if(ConfigFileEntry.failed_oper_notice)
                sendto_realops_snomask(SNO_GENERAL, L_NETWIDE,
                                       "Failed CHALLENGE attempt - host mismatch by %s (%s@%s)",
                                       source_p->name, source_p->username,
                                       source_p->host);
            return 0;
        }

        cleanup_challenge(source_p);

        oper_up(source_p, oper_p);

        ilog(L_OPERED, "OPER %s by %s!%s@%s (%s)",
             source_p->localClient->opername, source_p->name,
             source_p->username, source_p->host, source_p->sockhost);
        return 0;
    }

    cleanup_challenge(source_p);

    oper_p = find_oper_conf(source_p->username, source_p->orighost,
                            source_p->sockhost, parv[1]);

    if(oper_p == NULL) {
        sendto_one_numeric(source_p, ERR_NOOPERHOST, form_str(ERR_NOOPERHOST));
        ilog(L_FOPER, "FAILED OPER (%s) by (%s!%s@%s) (%s)",
             parv[1], source_p->name,
             source_p->username, source_p->host, source_p->sockhost);

        if(ConfigFileEntry.failed_oper_notice)
            sendto_realops_snomask(SNO_GENERAL, L_NETWIDE,
                                   "Failed CHALLENGE attempt - host mismatch by %s (%s@%s)",
                                   source_p->name, source_p->username, source_p->host);
        return 0;
    }

    if(!oper_p->rsa_pubkey) {
        sendto_one_notice(source_p, ":I'm sorry, PK authentication is not enabled for your oper{} block.");
        return 0;
    }

    if(IsOperConfNeedSSL(oper_p) && !IsSSLClient(source_p)) {
        sendto_one_numeric(source_p, ERR_NOOPERHOST, form_str(ERR_NOOPERHOST));
        ilog(L_FOPER, "FAILED CHALLENGE (%s) by (%s!%s@%s) (%s) -- requires SSL/TLS",
             parv[1], source_p->name, source_p->username, source_p->host,
             source_p->sockhost);

        if(ConfigFileEntry.failed_oper_notice) {
            sendto_realops_snomask(SNO_GENERAL, L_ALL,
                                   "Failed CHALLENGE attempt - missing SSL/TLS by %s (%s@%s)",
                                   source_p->name, source_p->username, source_p->host);
        }
        return 0;
    }

    if (oper_p->certfp != NULL) {
        if (source_p->certfp == NULL || strcasecmp(source_p->certfp, oper_p->certfp)) {
            sendto_one_numeric(source_p, ERR_NOOPERHOST, form_str(ERR_NOOPERHOST));
            ilog(L_FOPER, "FAILED OPER (%s) by (%s!%s@%s) (%s) -- client certificate fingerprint mismatch",
                 parv[1], source_p->name,
                 source_p->username, source_p->host, source_p->sockhost);

            if(ConfigFileEntry.failed_oper_notice) {
                sendto_realops_snomask(SNO_GENERAL, L_ALL,
                                       "Failed OPER attempt - client certificate fingerprint mismatch by %s (%s@%s)",
                                       source_p->name, source_p->username, source_p->host);
            }
            return 0;
        }
    }

    if(!generate_challenge(&challenge, &(source_p->localClient->challenge), oper_p->rsa_pubkey)) {
        char *chal = challenge;
        source_p->localClient->chal_time = rb_current_time();
        for(;;) {
            cnt = rb_strlcpy(chal_line, chal, CHALLENGE_WIDTH);
            sendto_one(source_p, form_str(RPL_RSACHALLENGE2), me.name, source_p->name, chal_line);
            if(cnt > CHALLENGE_WIDTH)
                chal += CHALLENGE_WIDTH - 1;
            else
                break;

        }
        sendto_one(source_p, form_str(RPL_ENDOFRSACHALLENGE2),
                   me.name, source_p->name);
        rb_free(challenge);
        source_p->localClient->opername = rb_strdup(oper_p->name);
    } else
        sendto_one_notice(source_p, ":Failed to generate challenge.");

    return 0;
}

static int
generate_challenge(char **r_challenge, char **r_response, RSA * rsa)
{
    SHA_CTX ctx;
    unsigned char secret[CHALLENGE_SECRET_LENGTH], *tmp;
    unsigned long length;
    unsigned long e = 0;
    unsigned long cnt = 0;
    int ret;

    if(!rsa)
        return -1;
    if(rb_get_random(secret, CHALLENGE_SECRET_LENGTH)) {
        SHA1_Init(&ctx);
        SHA1_Update(&ctx, (uint8_t *)secret, CHALLENGE_SECRET_LENGTH);
        *r_response = malloc(SHA_DIGEST_LENGTH);
        SHA1_Final((uint8_t *)*r_response, &ctx);

        length = RSA_size(rsa);
        tmp = rb_malloc(length);
        ret = RSA_public_encrypt(CHALLENGE_SECRET_LENGTH, secret, tmp, rsa, RSA_PKCS1_OAEP_PADDING);

        if(ret >= 0) {
            *r_challenge = (char *)rb_base64_encode(tmp, ret);
            rb_free(tmp);
            return 0;
        }

        rb_free(tmp);
        rb_free(*r_response);
        *r_response = NULL;
    }

    ERR_load_crypto_strings();
    while ((cnt < 100) && (e = ERR_get_error())) {
        ilog(L_MAIN, "SSL error: %s", ERR_error_string(e, 0));
        cnt++;
    }

    return (-1);
}

#endif /* HAVE_LIBCRYPTO */
