#if defined(NO_BUFFER) || defined(NO_IP) || defined(NO_OPENSSL)
# error "Badness, NO_BUFFER, NO_IP or NO_OPENSSL is defined, turn them *off*"
#endif

/* Include our bits'n'pieces */
#include "tunala.h"

/********************************************/
/* Our local types that specify our "world" */
/********************************************/

/*
 * These represent running "tunnels". Eg. if you wanted to do SSL in a
 * "message-passing" scanario, the "int" file-descriptors might be replaced
 * by thread or process IDs, and the "select" code might be replaced by
 * message handling code. Whatever.
 */
typedef struct _tunala_item_t {
    /*
     * The underlying SSL state machine. This is a data-only processing unit
     * and we communicate with it by talking to its four "buffers".
     */
    state_machine_t sm;
    /*
     * The file-descriptors for the "dirty" (encrypted) side of the SSL
     * setup. In actuality, this is typically a socket and both values are
     * identical.
     */
    int dirty_read, dirty_send;
    /*
     * The file-descriptors for the "clean" (unencrypted) side of the SSL
     * setup. These could be stdin/stdout, a socket (both values the same),
     * or whatever you like.
     */
    int clean_read, clean_send;
} tunala_item_t;

/*
 * This structure is used as the data for running the main loop. Namely, in a
 * network format such as this, it is stuff for select() - but as pointed out,
 * when moving the real-world to somewhere else, this might be replaced by
 * something entirely different. It's basically the stuff that controls when
 * it's time to do some "work".
 */
typedef struct _select_sets_t {
    int max;                    /* As required as the first argument to
                                 * select() */
    fd_set reads, sends, excepts; /* As passed to select() */
} select_sets_t;
typedef struct _tunala_selector_t {
    select_sets_t last_selected; /* Results of the last select() */
    select_sets_t next_select;  /* What we'll next select on */
} tunala_selector_t;

/*
 * This structure is *everything*. We do it to avoid the use of globals so
 * that, for example, it would be easier to shift things around between
 * async-IO, thread-based, or multi-fork()ed (or combinations thereof).
 */
typedef struct _tunala_world_t {
    /* The file-descriptor we "listen" on for new connections */
    int listen_fd;
    /* The array of tunnels */
    tunala_item_t *tunnels;
    /* the number of tunnels in use and allocated, respectively */
    unsigned int tunnels_used, tunnels_size;
    /* Our outside "loop" context stuff */
    tunala_selector_t selector;
    /*
     * Our SSL_CTX, which is configured as the SSL client or server and has
     * the various cert-settings and callbacks configured.
     */
    SSL_CTX *ssl_ctx;
    /*
     * Simple flag with complex logic :-) Indicates whether we're an SSL
     * server or an SSL client.
     */
    int server_mode;
} tunala_world_t;

/*****************************/
/* Internal static functions */
/*****************************/

static SSL_CTX *initialise_ssl_ctx(int server_mode, const char *engine_id,
                                   const char *CAfile, const char *cert,
                                   const char *key, const char *dcert,
                                   const char *dkey, const char *cipher_list,
                                   const char *dh_file,
                                   const char *dh_special, int tmp_rsa,
                                   int ctx_options, int out_state,
                                   int out_verify, int verify_mode,
                                   unsigned int verify_depth);
static void selector_init(tunala_selector_t * selector);
static void selector_add_listener(tunala_selector_t * selector, int fd);
static void selector_add_tunala(tunala_selector_t * selector,
                                tunala_item_t * t);
static int selector_select(tunala_selector_t * selector);
/*
 * This returns -1 for error, 0 for no new connections, or 1 for success, in
 * which case *newfd is populated.
 */
static int selector_get_listener(tunala_selector_t * selector, int fd,
                                 int *newfd);
static int tunala_world_new_item(tunala_world_t * world, int fd,
                                 const char *ip, unsigned short port,
                                 int flipped);
static void tunala_world_del_item(tunala_world_t * world, unsigned int idx);
static int tunala_item_io(tunala_selector_t * selector, tunala_item_t * item);

/*********************************************/
/* MAIN FUNCTION (and its utility functions) */
/*********************************************/

static const char *def_proxyhost = "127.0.0.1:443";
static const char *def_listenhost = "127.0.0.1:8080";
static int def_max_tunnels = 50;
static const char *def_cacert = NULL;
static const char *def_cert = NULL;
static const char *def_key = NULL;
static const char *def_dcert = NULL;
static const char *def_dkey = NULL;
static const char *def_engine_id = NULL;
static int def_server_mode = 0;
static int def_flipped = 0;
static const char *def_cipher_list = NULL;
static const char *def_dh_file = NULL;
static const char *def_dh_special = NULL;
static int def_tmp_rsa = 1;
static int def_ctx_options = 0;
static int def_verify_mode = 0;
static unsigned int def_verify_depth = 10;
static int def_out_state = 0;
static unsigned int def_out_verify = 0;
static int def_out_totals = 0;
static int def_out_conns = 0;

static const char *helpstring =
    "\n'Tunala' (A tunneler with a New Zealand accent)\n"
    "Usage: tunala [options], where options are from;\n"
    " -listen [host:]<port>  (default = 127.0.0.1:8080)\n"
    " -proxy <host>:<port>   (default = 127.0.0.1:443)\n"
    " -maxtunnels <num>      (default = 50)\n"
    " -cacert <path|NULL>    (default = NULL)\n"
    " -cert <path|NULL>      (default = NULL)\n"
    " -key <path|NULL>       (default = whatever '-cert' is)\n"
    " -dcert <path|NULL>     (usually for DSA, default = NULL)\n"
    " -dkey <path|NULL>      (usually for DSA, default = whatever '-dcert' is)\n"
    " -engine <id|NULL>      (default = NULL)\n"
    " -server <0|1>          (default = 0, ie. an SSL client)\n"
    " -flipped <0|1>         (makes SSL servers be network clients, and vice versa)\n"
    " -cipher <list>         (specifies cipher list to use)\n"
    " -dh_file <path>        (a PEM file containing DH parameters to use)\n"
    " -dh_special <NULL|generate|standard> (see below: def=NULL)\n"
    " -no_tmp_rsa            (don't generate temporary RSA keys)\n"
    " -no_ssl2               (disable SSLv2)\n"
    " -no_ssl3               (disable SSLv3)\n"
    " -no_tls1               (disable TLSv1)\n"
    " -v_peer                (verify the peer certificate)\n"
    " -v_strict              (do not continue if peer doesn't authenticate)\n"
    " -v_once                (no verification in renegotiates)\n"
    " -v_depth <num>         (limit certificate chain depth, default = 10)\n"
    " -out_conns             (prints client connections and disconnections)\n"
    " -out_state             (prints SSL handshake states)\n"
    " -out_verify <0|1|2|3>  (prints certificate verification states: def=1)\n"
    " -out_totals            (prints out byte-totals when a tunnel closes)\n"
    " -<h|help|?>            (displays this help screen)\n"
    "Notes:\n"
    "(1) It is recommended to specify a cert+key when operating as an SSL server.\n"
    "    If you only specify '-cert', the same file must contain a matching\n"
    "    private key.\n"
    "(2) Either dh_file or dh_special can be used to specify where DH parameters\n"
    "    will be obtained from (or '-dh_special NULL' for the default choice) but\n"
    "    you cannot specify both. For dh_special, 'generate' will create new DH\n"
    "    parameters on startup, and 'standard' will use embedded parameters\n"
    "    instead.\n"
    "(3) Normally an ssl client connects to an ssl server - so that an 'ssl client\n"
    "    tunala' listens for 'clean' client connections and proxies ssl, and an\n"
    "    'ssl server tunala' listens for ssl connections and proxies 'clean'. With\n"
    "    '-flipped 1', this behaviour is reversed so that an 'ssl server tunala'\n"
    "    listens for clean client connections and proxies ssl (but participating\n"
    "    as an ssl *server* in the SSL/TLS protocol), and an 'ssl client tunala'\n"
    "    listens for ssl connections (participating as an ssl *client* in the\n"
    "    SSL/TLS protocol) and proxies 'clean' to the end destination. This can\n"
    "    be useful for allowing network access to 'servers' where only the server\n"
    "    needs to authenticate the client (ie. the other way is not required).\n"
    "    Even with client and server authentication, this 'technique' mitigates\n"
    "    some DoS (denial-of-service) potential as it will be the network client\n"
    "    having to perform the first private key operation rather than the other\n"
    "    way round.\n"
    "(4) The 'technique' used by setting '-flipped 1' is probably compatible with\n"
    "    absolutely nothing except another complimentary instance of 'tunala'\n"
    "    running with '-flipped 1'. :-)\n";

/*
 * Default DH parameters for use with "-dh_special standard" ... stolen
 * striaght from s_server.
 */
static unsigned char dh512_p[] = {
    0xDA, 0x58, 0x3C, 0x16, 0xD9, 0x85, 0x22, 0x89, 0xD0, 0xE4, 0xAF, 0x75,
    0x6F, 0x4C, 0xCA, 0x92, 0xDD, 0x4B, 0xE5, 0x33, 0xB8, 0x04, 0xFB, 0x0F,
    0xED, 0x94, 0xEF, 0x9C, 0x8A, 0x44, 0x03, 0xED, 0x57, 0x46, 0x50, 0xD3,
    0x69, 0x99, 0xDB, 0x29, 0xD7, 0x76, 0x27, 0x6B, 0xA2, 0xD3, 0xD4, 0x12,
    0xE2, 0x18, 0xF4, 0xDD, 0x1E, 0x08, 0x4C, 0xF6, 0xD8, 0x00, 0x3E, 0x7C,
    0x47, 0x74, 0xE8, 0x33,
};

static unsigned char dh512_g[] = {
    0x02,
};

/*
 * And the function that parses the above "standard" parameters, again,
 * straight out of s_server.
 */
static DH *get_dh512(void)
{
    DH *dh = NULL;

    if ((dh = DH_new()) == NULL)
        return (NULL);
    dh->p = BN_bin2bn(dh512_p, sizeof(dh512_p), NULL);
    dh->g = BN_bin2bn(dh512_g, sizeof(dh512_g), NULL);
    if ((dh->p == NULL) || (dh->g == NULL))
        return (NULL);
    return (dh);
}

/* Various help/error messages used by main() */
static int usage(const char *errstr, int isunknownarg)
{
    if (isunknownarg)
        fprintf(stderr, "Error: unknown argument '%s'\n", errstr);
    else
        fprintf(stderr, "Error: %s\n", errstr);
    fprintf(stderr, "%s\n", helpstring);
    return 1;
}

static int err_str0(const char *str0)
{
    fprintf(stderr, "%s\n", str0);
    return 1;
}

static int err_str1(const char *fmt, const char *str1)
{
    fprintf(stderr, fmt, str1);
    fprintf(stderr, "\n");
    return 1;
}

static int parse_max_tunnels(const char *s, unsigned int *maxtunnels)
{
    unsigned long l;
    if (!int_strtoul(s, &l) || (l < 1) || (l > 1024)) {
        fprintf(stderr, "Error, '%s' is an invalid value for "
                "maxtunnels\n", s);
        return 0;
    }
    *maxtunnels = (unsigned int)l;
    return 1;
}

static int parse_server_mode(const char *s, int *servermode)
{
    unsigned long l;
    if (!int_strtoul(s, &l) || (l > 1)) {
        fprintf(stderr, "Error, '%s' is an invalid value for the "
                "server mode\n", s);
        return 0;
    }
    *servermode = (int)l;
    return 1;
}

static int parse_dh_special(const char *s, const char **dh_special)
{
    if ((strcmp(s, "NULL") == 0) || (strcmp(s, "generate") == 0) ||
        (strcmp(s, "standard") == 0)) {
        *dh_special = s;
        return 1;
    }
    fprintf(stderr, "Error, '%s' is an invalid value for 'dh_special'\n", s);
    return 0;
}

static int parse_verify_level(const char *s, unsigned int *verify_level)
{
    unsigned long l;
    if (!int_strtoul(s, &l) || (l > 3)) {
        fprintf(stderr, "Error, '%s' is an invalid value for "
                "out_verify\n", s);
        return 0;
    }
    *verify_level = (unsigned int)l;
    return 1;
}

static int parse_verify_depth(const char *s, unsigned int *verify_depth)
{
    unsigned long l;
    if (!int_strtoul(s, &l) || (l < 1) || (l > 50)) {
        fprintf(stderr, "Error, '%s' is an invalid value for "
                "verify_depth\n", s);
        return 0;
    }
    *verify_depth = (unsigned int)l;
    return 1;
}

/* Some fprintf format strings used when tunnels close */
static const char *io_stats_dirty =
    "    SSL traffic;   %8lu bytes in, %8lu bytes out\n";
static const char *io_stats_clean =
    "    clear traffic; %8lu bytes in, %8lu bytes out\n";

int main(int argc, char *argv[])
{
    unsigned int loop;
    int newfd;
    tunala_world_t world;
    tunala_item_t *t_item;
    const char *proxy_ip;
    unsigned short proxy_port;
    /* Overridables */
    const char *proxyhost = def_proxyhost;
    const char *listenhost = def_listenhost;
    unsigned int max_tunnels = def_max_tunnels;
    const char *cacert = def_cacert;
    const char *cert = def_cert;
    const char *key = def_key;
    const char *dcert = def_dcert;
    const char *dkey = def_dkey;
    const char *engine_id = def_engine_id;
    int server_mode = def_server_mode;
    int flipped = def_flipped;
    const char *cipher_list = def_cipher_list;
    const char *dh_file = def_dh_file;
    const char *dh_special = def_dh_special;
    int tmp_rsa = def_tmp_rsa;
    int ctx_options = def_ctx_options;
    int verify_mode = def_verify_mode;
    unsigned int verify_depth = def_verify_depth;
    int out_state = def_out_state;
    unsigned int out_verify = def_out_verify;
    int out_totals = def_out_totals;
    int out_conns = def_out_conns;

/* Parse command-line arguments */
 next_arg:
    argc--;
    argv++;
    if (argc > 0) {
        if (strcmp(*argv, "-listen") == 0) {
            if (argc < 2)
                return usage("-listen requires an argument", 0);
            argc--;
            argv++;
            listenhost = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-proxy") == 0) {
            if (argc < 2)
                return usage("-proxy requires an argument", 0);
            argc--;
            argv++;
            proxyhost = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-maxtunnels") == 0) {
            if (argc < 2)
                return usage("-maxtunnels requires an argument", 0);
            argc--;
            argv++;
            if (!parse_max_tunnels(*argv, &max_tunnels))
                return 1;
            goto next_arg;
        } else if (strcmp(*argv, "-cacert") == 0) {
            if (argc < 2)
                return usage("-cacert requires an argument", 0);
            argc--;
            argv++;
            if (strcmp(*argv, "NULL") == 0)
                cacert = NULL;
            else
                cacert = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-cert") == 0) {
            if (argc < 2)
                return usage("-cert requires an argument", 0);
            argc--;
            argv++;
            if (strcmp(*argv, "NULL") == 0)
                cert = NULL;
            else
                cert = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-key") == 0) {
            if (argc < 2)
                return usage("-key requires an argument", 0);
            argc--;
            argv++;
            if (strcmp(*argv, "NULL") == 0)
                key = NULL;
            else
                key = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-dcert") == 0) {
            if (argc < 2)
                return usage("-dcert requires an argument", 0);
            argc--;
            argv++;
            if (strcmp(*argv, "NULL") == 0)
                dcert = NULL;
            else
                dcert = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-dkey") == 0) {
            if (argc < 2)
                return usage("-dkey requires an argument", 0);
            argc--;
            argv++;
            if (strcmp(*argv, "NULL") == 0)
                dkey = NULL;
            else
                dkey = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-engine") == 0) {
            if (argc < 2)
                return usage("-engine requires an argument", 0);
            argc--;
            argv++;
            engine_id = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-server") == 0) {
            if (argc < 2)
                return usage("-server requires an argument", 0);
            argc--;
            argv++;
            if (!parse_server_mode(*argv, &server_mode))
                return 1;
            goto next_arg;
        } else if (strcmp(*argv, "-flipped") == 0) {
            if (argc < 2)
                return usage("-flipped requires an argument", 0);
            argc--;
            argv++;
            if (!parse_server_mode(*argv, &flipped))
                return 1;
            goto next_arg;
        } else if (strcmp(*argv, "-cipher") == 0) {
            if (argc < 2)
                return usage("-cipher requires an argument", 0);
            argc--;
            argv++;
            cipher_list = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-dh_file") == 0) {
            if (argc < 2)
                return usage("-dh_file requires an argument", 0);
            if (dh_special)
                return usage("cannot mix -dh_file with " "-dh_special", 0);
            argc--;
            argv++;
            dh_file = *argv;
            goto next_arg;
        } else if (strcmp(*argv, "-dh_special") == 0) {
            if (argc < 2)
                return usage("-dh_special requires an argument", 0);
            if (dh_file)
                return usage("cannot mix -dh_file with " "-dh_special", 0);
            argc--;
            argv++;
            if (!parse_dh_special(*argv, &dh_special))
                return 1;
            goto next_arg;
        } else if (strcmp(*argv, "-no_tmp_rsa") == 0) {
            tmp_rsa = 0;
            goto next_arg;
        } else if (strcmp(*argv, "-no_ssl2") == 0) {
            ctx_options |= SSL_OP_NO_SSLv2;
            goto next_arg;
        } else if (strcmp(*argv, "-no_ssl3") == 0) {
            ctx_options |= SSL_OP_NO_SSLv3;
            goto next_arg;
        } else if (strcmp(*argv, "-no_tls1") == 0) {
            ctx_options |= SSL_OP_NO_TLSv1;
            goto next_arg;
        } else if (strcmp(*argv, "-v_peer") == 0) {
            verify_mode |= SSL_VERIFY_PEER;
            goto next_arg;
        } else if (strcmp(*argv, "-v_strict") == 0) {
            verify_mode |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
            goto next_arg;
        } else if (strcmp(*argv, "-v_once") == 0) {
            verify_mode |= SSL_VERIFY_CLIENT_ONCE;
            goto next_arg;
        } else if (strcmp(*argv, "-v_depth") == 0) {
            if (argc < 2)
                return usage("-v_depth requires an argument", 0);
            argc--;
            argv++;
            if (!parse_verify_depth(*argv, &verify_depth))
                return 1;
            goto next_arg;
        } else if (strcmp(*argv, "-out_state") == 0) {
            out_state = 1;
            goto next_arg;
        } else if (strcmp(*argv, "-out_verify") == 0) {
            if (argc < 2)
                return usage("-out_verify requires an argument", 0);
            argc--;
            argv++;
            if (!parse_verify_level(*argv, &out_verify))
                return 1;
            goto next_arg;
        } else if (strcmp(*argv, "-out_totals") == 0) {
            out_totals = 1;
            goto next_arg;
        } else if (strcmp(*argv, "-out_conns") == 0) {
            out_conns = 1;
            goto next_arg;
        } else if ((strcmp(*argv, "-h") == 0) ||
                   (strcmp(*argv, "-help") == 0) ||
                   (strcmp(*argv, "-?") == 0)) {
            fprintf(stderr, "%s\n", helpstring);
            return 0;
        } else
            return usage(*argv, 1);
    }
    /* Run any sanity checks we want here */
    if (!cert && !dcert && server_mode)
        fprintf(stderr, "WARNING: you are running an SSL server without "
                "a certificate - this may not work!\n");

    /* Initialise network stuff */
    if (!ip_initialise())
        return err_str0("ip_initialise failed");
    /* Create the SSL_CTX */
    if ((world.ssl_ctx = initialise_ssl_ctx(server_mode, engine_id,
                                            cacert, cert, key, dcert, dkey,
                                            cipher_list, dh_file, dh_special,
                                            tmp_rsa, ctx_options, out_state,
                                            out_verify, verify_mode,
                                            verify_depth)) == NULL)
        return err_str1("initialise_ssl_ctx(engine_id=%s) failed",
                        (engine_id == NULL) ? "NULL" : engine_id);
    if (engine_id)
        fprintf(stderr, "Info, engine '%s' initialised\n", engine_id);
    /* Create the listener */
    if ((world.listen_fd = ip_create_listener(listenhost)) == -1)
        return err_str1("ip_create_listener(%s) failed", listenhost);
    fprintf(stderr, "Info, listening on '%s'\n", listenhost);
    if (!ip_parse_address(proxyhost, &proxy_ip, &proxy_port, 0))
        return err_str1("ip_parse_address(%s) failed", proxyhost);
    fprintf(stderr, "Info, proxying to '%s' (%d.%d.%d.%d:%d)\n", proxyhost,
            (int)proxy_ip[0], (int)proxy_ip[1],
            (int)proxy_ip[2], (int)proxy_ip[3], (int)proxy_port);
    fprintf(stderr, "Info, set maxtunnels to %d\n", (int)max_tunnels);
    fprintf(stderr, "Info, set to operate as an SSL %s\n",
            (server_mode ? "server" : "client"));
    /* Initialise the rest of the stuff */
    world.tunnels_used = world.tunnels_size = 0;
    world.tunnels = NULL;
    world.server_mode = server_mode;
    selector_init(&world.selector);

/* We're ready to loop */
 main_loop:
    /* Should we listen for *new* tunnels? */
    if (world.tunnels_used < max_tunnels)
        selector_add_listener(&world.selector, world.listen_fd);
    /* We should add in our existing tunnels */
    for (loop = 0; loop < world.tunnels_used; loop++)
        selector_add_tunala(&world.selector, world.tunnels + loop);
    /* Now do the select */
    switch (selector_select(&world.selector)) {
    case -1:
        if (errno != EINTR) {
            fprintf(stderr, "selector_select returned a " "badness error.\n");
            goto shouldnt_happen;
        }
        fprintf(stderr, "Warn, selector interrupted by a signal\n");
        goto main_loop;
    case 0:
        fprintf(stderr, "Warn, selector_select returned 0 - signal?" "?\n");
        goto main_loop;
    default:
        break;
    }
    /* Accept new connection if we should and can */
    if ((world.tunnels_used < max_tunnels)
        && (selector_get_listener(&world.selector, world.listen_fd, &newfd) ==
            1)) {
        /* We have a new connection */
        if (!tunala_world_new_item(&world, newfd, proxy_ip,
                                   proxy_port, flipped))
            fprintf(stderr, "tunala_world_new_item failed\n");
        else if (out_conns)
            fprintf(stderr, "Info, new tunnel opened, now up to "
                    "%d\n", world.tunnels_used);
    }
    /*
     * Give each tunnel its moment, note the while loop is because it makes
     * the logic easier than with "for" to deal with an array that may shift
     * because of deletes.
     */
    loop = 0;
    t_item = world.tunnels;
    while (loop < world.tunnels_used) {
        if (!tunala_item_io(&world.selector, t_item)) {
            /*
             * We're closing whether for reasons of an error or a natural
             * close. Don't increment loop or t_item because the next item is
             * moving to us!
             */
            if (!out_totals)
                goto skip_totals;
            fprintf(stderr, "Tunnel closing, traffic stats follow\n");
            /* Display the encrypted (over the network) stats */
            fprintf(stderr, io_stats_dirty,
                    buffer_total_in(state_machine_get_buffer
                                    (&t_item->sm, SM_DIRTY_IN)),
                    buffer_total_out(state_machine_get_buffer
                                     (&t_item->sm, SM_DIRTY_OUT)));
            /*
             * Display the local (tunnelled) stats. NB: Data we *receive* is
             * data sent *out* of the state_machine on its 'clean' side.
             * Hence the apparent back-to-front OUT/IN mixup here :-)
             */
            fprintf(stderr, io_stats_clean,
                    buffer_total_out(state_machine_get_buffer
                                     (&t_item->sm, SM_CLEAN_OUT)),
                    buffer_total_in(state_machine_get_buffer
                                    (&t_item->sm, SM_CLEAN_IN)));
 skip_totals:
            tunala_world_del_item(&world, loop);
            if (out_conns)
                fprintf(stderr, "Info, tunnel closed, down to %d\n",
                        world.tunnels_used);
        } else {
            /* Move to the next item */
            loop++;
            t_item++;
        }
    }
    goto main_loop;
    /* Should never get here */
 shouldnt_happen:
    abort();
    return 1;
}

/****************/
/* OpenSSL bits */
/****************/

static int ctx_set_cert(SSL_CTX *ctx, const char *cert, const char *key)
{
    FILE *fp = NULL;
    X509 *x509 = NULL;
    EVP_PKEY *pkey = NULL;
    int toret = 0;              /* Assume an error */

    /* cert */
    if (cert) {
        if ((fp = fopen(cert, "r")) == NULL) {
            fprintf(stderr, "Error opening cert file '%s'\n", cert);
            goto err;
        }
        if (!PEM_read_X509(fp, &x509, NULL, NULL)) {
            fprintf(stderr, "Error reading PEM cert from '%s'\n", cert);
            goto err;
        }
        if (!SSL_CTX_use_certificate(ctx, x509)) {
            fprintf(stderr, "Error, cert in '%s' can not be used\n", cert);
            goto err;
        }
        /* Clear the FILE* for reuse in the "key" code */
        fclose(fp);
        fp = NULL;
        fprintf(stderr, "Info, operating with cert in '%s'\n", cert);
        /*
         * If a cert was given without matching key, we assume the same file
         * contains the required key.
         */
        if (!key)
            key = cert;
    } else {
        if (key)
            fprintf(stderr, "Error, can't specify a key without a "
                    "corresponding certificate\n");
        else
            fprintf(stderr, "Error, ctx_set_cert called with " "NULLs!\n");
        goto err;
    }
    /* key */
    if (key) {
        if ((fp = fopen(key, "r")) == NULL) {
            fprintf(stderr, "Error opening key file '%s'\n", key);
            goto err;
        }
        if (!PEM_read_PrivateKey(fp, &pkey, NULL, NULL)) {
            fprintf(stderr, "Error reading PEM key from '%s'\n", key);
            goto err;
        }
        if (!SSL_CTX_use_PrivateKey(ctx, pkey)) {
            fprintf(stderr, "Error, key in '%s' can not be used\n", key);
            goto err;
        }
        fprintf(stderr, "Info, operating with key in '%s'\n", key);
    } else
        fprintf(stderr, "Info, operating without a cert or key\n");
    /* Success */
    toret = 1;
 err:
    if (x509)
        X509_free(x509);
    if (pkey)
        EVP_PKEY_free(pkey);
    if (fp)
        fclose(fp);
    return toret;
}

static int ctx_set_dh(SSL_CTX *ctx, const char *dh_file,
                      const char *dh_special)
{
    DH *dh = NULL;
    FILE *fp = NULL;

    if (dh_special) {
        if (strcmp(dh_special, "NULL") == 0)
            return 1;
        if (strcmp(dh_special, "standard") == 0) {
            if ((dh = get_dh512()) == NULL) {
                fprintf(stderr, "Error, can't parse 'standard'"
                        " DH parameters\n");
                return 0;
            }
            fprintf(stderr, "Info, using 'standard' DH parameters\n");
            goto do_it;
        }
        if (strcmp(dh_special, "generate") != 0)
            /*
             * This shouldn't happen - screening values is handled in main().
             */
            abort();
        fprintf(stderr, "Info, generating DH parameters ... ");
        fflush(stderr);
        if (!(dh = DH_new()) || !DH_generate_parameters_ex(dh, 512,
                                                           DH_GENERATOR_5,
                                                           NULL)) {
            fprintf(stderr, "error!\n");
            if (dh)
                DH_free(dh);
            return 0;
        }
        fprintf(stderr, "complete\n");
        goto do_it;
    }
    /* So, we're loading dh_file */
    if ((fp = fopen(dh_file, "r")) == NULL) {
        fprintf(stderr, "Error, couldn't open '%s' for DH parameters\n",
                dh_file);
        return 0;
    }
    dh = PEM_read_DHparams(fp, NULL, NULL, NULL);
    fclose(fp);
    if (dh == NULL) {
        fprintf(stderr, "Error, could not parse DH parameters from '%s'\n",
                dh_file);
        return 0;
    }
    fprintf(stderr, "Info, using DH parameters from file '%s'\n", dh_file);
 do_it:
    SSL_CTX_set_tmp_dh(ctx, dh);
    DH_free(dh);
    return 1;
}

static SSL_CTX *initialise_ssl_ctx(int server_mode, const char *engine_id,
                                   const char *CAfile, const char *cert,
                                   const char *key, const char *dcert,
                                   const char *dkey, const char *cipher_list,
                                   const char *dh_file,
                                   const char *dh_special, int tmp_rsa,
                                   int ctx_options, int out_state,
                                   int out_verify, int verify_mode,
                                   unsigned int verify_depth)
{
    SSL_CTX *ctx = NULL, *ret = NULL;
    const SSL_METHOD *meth;
    ENGINE *e = NULL;

    OpenSSL_add_ssl_algorithms();
    SSL_load_error_strings();

    meth = (server_mode ? SSLv23_server_method() : SSLv23_client_method());
    if (meth == NULL)
        goto err;
    if (engine_id) {
        ENGINE_load_builtin_engines();
        if ((e = ENGINE_by_id(engine_id)) == NULL) {
            fprintf(stderr, "Error obtaining '%s' engine, openssl "
                    "errors follow\n", engine_id);
            goto err;
        }
        if (!ENGINE_set_default(e, ENGINE_METHOD_ALL)) {
            fprintf(stderr, "Error assigning '%s' engine, openssl "
                    "errors follow\n", engine_id);
            goto err;
        }
        ENGINE_free(e);
    }
    if ((ctx = SSL_CTX_new(meth)) == NULL)
        goto err;
    /* cacert */
    if (CAfile) {
        if (!X509_STORE_load_locations(SSL_CTX_get_cert_store(ctx),
                                       CAfile, NULL)) {
            fprintf(stderr, "Error loading CA cert(s) in '%s'\n", CAfile);
            goto err;
        }
        fprintf(stderr, "Info, operating with CA cert(s) in '%s'\n", CAfile);
    } else
        fprintf(stderr, "Info, operating without a CA cert(-list)\n");
    if (!SSL_CTX_set_default_verify_paths(ctx)) {
        fprintf(stderr, "Error setting default verify paths\n");
        goto err;
    }

    /* cert and key */
    if ((cert || key) && !ctx_set_cert(ctx, cert, key))
        goto err;
    /* dcert and dkey */
    if ((dcert || dkey) && !ctx_set_cert(ctx, dcert, dkey))
        goto err;
    /* temporary RSA key generation */
    if (tmp_rsa)
        SSL_CTX_set_tmp_rsa_callback(ctx, cb_generate_tmp_rsa);

    /* cipher_list */
    if (cipher_list) {
        if (!SSL_CTX_set_cipher_list(ctx, cipher_list)) {
            fprintf(stderr, "Error setting cipher list '%s'\n", cipher_list);
            goto err;
        }
        fprintf(stderr, "Info, set cipher list '%s'\n", cipher_list);
    } else
        fprintf(stderr, "Info, operating with default cipher list\n");

    /* dh_file & dh_special */
    if ((dh_file || dh_special) && !ctx_set_dh(ctx, dh_file, dh_special))
        goto err;

    /* ctx_options */
    SSL_CTX_set_options(ctx, ctx_options);

    /* out_state (output of SSL handshake states to screen). */
    if (out_state)
        cb_ssl_info_set_output(stderr);

    /* out_verify */
    if (out_verify > 0) {
        cb_ssl_verify_set_output(stderr);
        cb_ssl_verify_set_level(out_verify);
    }

    /* verify_depth */
    cb_ssl_verify_set_depth(verify_depth);

    /* Success! (includes setting verify_mode) */
    SSL_CTX_set_info_callback(ctx, cb_ssl_info);
    SSL_CTX_set_verify(ctx, verify_mode, cb_ssl_verify);
    ret = ctx;
 err:
    if (!ret) {
        ERR_print_errors_fp(stderr);
        if (ctx)
            SSL_CTX_free(ctx);
    }
    return ret;
}

/*****************/
/* Selector bits */
/*****************/

static void selector_sets_init(select_sets_t * s)
{
    s->max = 0;
    FD_ZERO(&s->reads);
    FD_ZERO(&s->sends);
    FD_ZERO(&s->excepts);
}

static void selector_init(tunala_selector_t * selector)
{
    selector_sets_init(&selector->last_selected);
    selector_sets_init(&selector->next_select);
}

#define SEL_EXCEPTS 0x00
#define SEL_READS   0x01
#define SEL_SENDS   0x02
static void selector_add_raw_fd(tunala_selector_t * s, int fd, int flags)
{
    FD_SET(fd, &s->next_select.excepts);
    if (flags & SEL_READS)
        FD_SET(fd, &s->next_select.reads);
    if (flags & SEL_SENDS)
        FD_SET(fd, &s->next_select.sends);
    /* Adjust "max" */
    if (s->next_select.max < (fd + 1))
        s->next_select.max = fd + 1;
}

static void selector_add_listener(tunala_selector_t * selector, int fd)
{
    selector_add_raw_fd(selector, fd, SEL_READS);
}

static void selector_add_tunala(tunala_selector_t * s, tunala_item_t * t)
{
    /* Set clean read if sm.clean_in is not full */
    if (t->clean_read != -1) {
        selector_add_raw_fd(s, t->clean_read,
                            (buffer_full(state_machine_get_buffer(&t->sm,
                                                                  SM_CLEAN_IN))
                             ? SEL_EXCEPTS : SEL_READS));
    }
    /* Set clean send if sm.clean_out is not empty */
    if (t->clean_send != -1) {
        selector_add_raw_fd(s, t->clean_send,
                            (buffer_empty(state_machine_get_buffer(&t->sm,
                                                                   SM_CLEAN_OUT))
                             ? SEL_EXCEPTS : SEL_SENDS));
    }
    /* Set dirty read if sm.dirty_in is not full */
    if (t->dirty_read != -1) {
        selector_add_raw_fd(s, t->dirty_read,
                            (buffer_full(state_machine_get_buffer(&t->sm,
                                                                  SM_DIRTY_IN))
                             ? SEL_EXCEPTS : SEL_READS));
    }
    /* Set dirty send if sm.dirty_out is not empty */
    if (t->dirty_send != -1) {
        selector_add_raw_fd(s, t->dirty_send,
                            (buffer_empty(state_machine_get_buffer(&t->sm,
                                                                   SM_DIRTY_OUT))
                             ? SEL_EXCEPTS : SEL_SENDS));
    }
}

static int selector_select(tunala_selector_t * selector)
{
    memcpy(&selector->last_selected, &selector->next_select,
           sizeof(select_sets_t));
    selector_sets_init(&selector->next_select);
    return select(selector->last_selected.max,
                  &selector->last_selected.reads,
                  &selector->last_selected.sends,
                  &selector->last_selected.excepts, NULL);
}

/*
 * This returns -1 for error, 0 for no new connections, or 1 for success, in
 * which case *newfd is populated.
 */
static int selector_get_listener(tunala_selector_t * selector, int fd,
                                 int *newfd)
{
    if (FD_ISSET(fd, &selector->last_selected.excepts))
        return -1;
    if (!FD_ISSET(fd, &selector->last_selected.reads))
        return 0;
    if ((*newfd = ip_accept_connection(fd)) == -1)
        return -1;
    return 1;
}

/************************/
/* "Tunala" world stuff */
/************************/

static int tunala_world_make_room(tunala_world_t * world)
{
    unsigned int newsize;
    tunala_item_t *newarray;

    if (world->tunnels_used < world->tunnels_size)
        return 1;
    newsize = (world->tunnels_size == 0 ? 16 :
               ((world->tunnels_size * 3) / 2));
    if ((newarray = malloc(newsize * sizeof(tunala_item_t))) == NULL)
        return 0;
    memset(newarray, 0, newsize * sizeof(tunala_item_t));
    if (world->tunnels_used > 0)
        memcpy(newarray, world->tunnels,
               world->tunnels_used * sizeof(tunala_item_t));
    if (world->tunnels_size > 0)
        free(world->tunnels);
    /* migrate */
    world->tunnels = newarray;
    world->tunnels_size = newsize;
    return 1;
}

static int tunala_world_new_item(tunala_world_t * world, int fd,
                                 const char *ip, unsigned short port,
                                 int flipped)
{
    tunala_item_t *item;
    int newfd;
    SSL *new_ssl = NULL;

    if (!tunala_world_make_room(world))
        return 0;
    if ((new_ssl = SSL_new(world->ssl_ctx)) == NULL) {
        fprintf(stderr, "Error creating new SSL\n");
        ERR_print_errors_fp(stderr);
        return 0;
    }
    item = world->tunnels + (world->tunnels_used++);
    state_machine_init(&item->sm);
    item->clean_read = item->clean_send =
        item->dirty_read = item->dirty_send = -1;
    if ((newfd = ip_create_connection_split(ip, port)) == -1)
        goto err;
    /*
     * Which way round? If we're a server, "fd" is the dirty side and the
     * connection we open is the clean one. For a client, it's the other way
     * around. Unless, of course, we're "flipped" in which case everything
     * gets reversed. :-)
     */
    if ((world->server_mode && !flipped) || (!world->server_mode && flipped)) {
        item->dirty_read = item->dirty_send = fd;
        item->clean_read = item->clean_send = newfd;
    } else {
        item->clean_read = item->clean_send = fd;
        item->dirty_read = item->dirty_send = newfd;
    }
    /*
     * We use the SSL's "app_data" to indicate a call-back induced "kill"
     */
    SSL_set_app_data(new_ssl, NULL);
    if (!state_machine_set_SSL(&item->sm, new_ssl, world->server_mode))
        goto err;
    return 1;
 err:
    tunala_world_del_item(world, world->tunnels_used - 1);
    return 0;

}

static void tunala_world_del_item(tunala_world_t * world, unsigned int idx)
{
    tunala_item_t *item = world->tunnels + idx;
    if (item->clean_read != -1)
        close(item->clean_read);
    if (item->clean_send != item->clean_read)
        close(item->clean_send);
    item->clean_read = item->clean_send = -1;
    if (item->dirty_read != -1)
        close(item->dirty_read);
    if (item->dirty_send != item->dirty_read)
        close(item->dirty_send);
    item->dirty_read = item->dirty_send = -1;
    state_machine_close(&item->sm);
    /* OK, now we fix the item array */
    if (idx + 1 < world->tunnels_used)
        /* We need to scroll entries to the left */
        memmove(world->tunnels + idx,
                world->tunnels + (idx + 1),
                (world->tunnels_used - (idx + 1)) * sizeof(tunala_item_t));
    world->tunnels_used--;
}

static int tunala_item_io(tunala_selector_t * selector, tunala_item_t * item)
{
    int c_r, c_s, d_r, d_s;     /* Four boolean flags */

    /* Take ourselves out of the gene-pool if there was an except */
    if ((item->clean_read != -1) && FD_ISSET(item->clean_read,
                                             &selector->
                                             last_selected.excepts))
        return 0;
    if ((item->clean_send != -1) && FD_ISSET(item->clean_send,
                                             &selector->
                                             last_selected.excepts))
        return 0;
    if ((item->dirty_read != -1) && FD_ISSET(item->dirty_read,
                                             &selector->
                                             last_selected.excepts))
        return 0;
    if ((item->dirty_send != -1) && FD_ISSET(item->dirty_send,
                                             &selector->
                                             last_selected.excepts))
        return 0;
    /* Grab our 4 IO flags */
    c_r = c_s = d_r = d_s = 0;
    if (item->clean_read != -1)
        c_r = FD_ISSET(item->clean_read, &selector->last_selected.reads);
    if (item->clean_send != -1)
        c_s = FD_ISSET(item->clean_send, &selector->last_selected.sends);
    if (item->dirty_read != -1)
        d_r = FD_ISSET(item->dirty_read, &selector->last_selected.reads);
    if (item->dirty_send != -1)
        d_s = FD_ISSET(item->dirty_send, &selector->last_selected.sends);
    /* If no IO has happened for us, skip needless data looping */
    if (!c_r && !c_s && !d_r && !d_s)
        return 1;
    if (c_r)
        c_r = (buffer_from_fd(state_machine_get_buffer(&item->sm,
                                                       SM_CLEAN_IN),
                              item->clean_read) <= 0);
    if (c_s)
        c_s = (buffer_to_fd(state_machine_get_buffer(&item->sm,
                                                     SM_CLEAN_OUT),
                            item->clean_send) <= 0);
    if (d_r)
        d_r = (buffer_from_fd(state_machine_get_buffer(&item->sm,
                                                       SM_DIRTY_IN),
                              item->dirty_read) <= 0);
    if (d_s)
        d_s = (buffer_to_fd(state_machine_get_buffer(&item->sm,
                                                     SM_DIRTY_OUT),
                            item->dirty_send) <= 0);
    /* If any of the flags is non-zero, that means they need closing */
    if (c_r) {
        close(item->clean_read);
        if (item->clean_send == item->clean_read)
            item->clean_send = -1;
        item->clean_read = -1;
    }
    if (c_s && (item->clean_send != -1)) {
        close(item->clean_send);
        if (item->clean_send == item->clean_read)
            item->clean_read = -1;
        item->clean_send = -1;
    }
    if (d_r) {
        close(item->dirty_read);
        if (item->dirty_send == item->dirty_read)
            item->dirty_send = -1;
        item->dirty_read = -1;
    }
    if (d_s && (item->dirty_send != -1)) {
        close(item->dirty_send);
        if (item->dirty_send == item->dirty_read)
            item->dirty_read = -1;
        item->dirty_send = -1;
    }
    /*
     * This function name is attributed to the term donated by David Schwartz
     * on openssl-dev, message-ID:
     * <NCBBLIEPOCNJOAEKBEAKEEDGLIAA.davids@webmaster.com>. :-)
     */
    if (!state_machine_churn(&item->sm))
        /*
         * If the SSL closes, it will also zero-out the _in buffers and will
         * in future process just outgoing data. As and when the outgoing
         * data has gone, it will return zero here to tell us to bail out.
         */
        return 0;
    /* Otherwise, we return zero if both sides are dead. */
    if (((item->clean_read == -1) || (item->clean_send == -1)) &&
        ((item->dirty_read == -1) || (item->dirty_send == -1)))
        return 0;
    /*
     * If only one side closed, notify the SSL of this so it can take
     * appropriate action.
     */
    if ((item->clean_read == -1) || (item->clean_send == -1)) {
        if (!state_machine_close_clean(&item->sm))
            return 0;
    }
    if ((item->dirty_read == -1) || (item->dirty_send == -1)) {
        if (!state_machine_close_dirty(&item->sm))
            return 0;
    }
    return 1;
}