anope/sessions.c

/* Session Limiting functions.
 *
 * (C) 2003 Anope Team
 * Contact us at info@anope.org
 *
 * Please read COPYING and README for furhter details.
 *
 * Based on the original code of Epona by Lara.
 * Based on the original code of Services by Andy Church. 
 * 
 * $Id$ 
 *
 */

#include "services.h"
#include "pseudo.h"

/*************************************************************************/

/* SESSION LIMITING
 *
 * The basic idea of session limiting is to prevent one host from having more 
 * than a specified number of sessions (client connections/clones) on the 
 * network at any one time. To do this we have a list of sessions and 
 * exceptions. Each session structure records information about a single host,
 * including how many clients (sessions) that host has on the network. When a 
 * host reaches it's session limit, no more clients from that host will be 
 * allowed to connect.
 *
 * When a client connects to the network, we check to see if their host has 
 * reached the default session limit per host, and thus whether it is allowed 
 * any more. If it has reached the limit, we kill the connecting client; all 
 * the other clients are left alone. Otherwise we simply increment the counter 
 * within the session structure. When a client disconnects, we decrement the 
 * counter. When the counter reaches 0, we free the session.
 *
 * Exceptions allow one to specify custom session limits for a specific host 
 * or a range thereof. The first exception that the host matches is the one 
 * used.
 *
 * "Session Limiting" is likely to slow down services when there are frequent 
 * client connects and disconnects. The size of the exception list can also 
 * play a large role in this performance decrease. It is therefore recommened 
 * that you keep the number of exceptions to a minimum. A very simple hashing 
 * method is currently used to store the list of sessions. I'm sure there is 
 * room for improvement and optimisation of this, along with the storage of 
 * exceptions. Comments and suggestions are more than welcome!
 *
 * -TheShadow (02 April 1999)
 */

/*************************************************************************/

typedef struct session_ Session;
struct session_ {
    Session *prev, *next;
    char *host;
    int count;                  /* Number of clients with this host */
    int hits;                   /* Number of subsequent kills for a host */
};

/* I'm sure there is a better way to hash the list of hosts for which we are
 * storing session information. This should be sufficient for the mean time.
 * -TheShadow */

#define HASH(host)      (((host)[0]&31)<<5 | ((host)[1]&31))

static Session *sessionlist[1024];
static int32 nsessions = 0;

Exception *exceptions = NULL;
int16 nexceptions = 0;

/*************************************************************************/

static Session *findsession(const char *host);

static Exception *find_host_exception(const char *host);
static int exception_add(const char *mask, const int limit,
                         const char *reason, const char *who,
                         const time_t expires);

/*************************************************************************/
/****************************** Statistics *******************************/
/*************************************************************************/

void get_session_stats(long *nrec, long *memuse)
{
    Session *session;
    long mem;
    int i;

    mem = sizeof(Session) * nsessions;
    for (i = 0; i < 1024; i++) {
        for (session = sessionlist[i]; session; session = session->next) {
            mem += strlen(session->host) + 1;
        }
    }

    *nrec = nsessions;
    *memuse = mem;
}

void get_exception_stats(long *nrec, long *memuse)
{
    long mem;
    int i;

    mem = sizeof(Exception) * nexceptions;
    for (i = 0; i < nexceptions; i++) {
        mem += strlen(exceptions[i].mask) + 1;
        mem += strlen(exceptions[i].reason) + 1;
    }
    *nrec = nexceptions;
    *memuse = mem;
}

/*************************************************************************/
/************************* Session List Display **************************/
/*************************************************************************/

/* Syntax: SESSION LIST threshold
 *	Lists all sessions with atleast threshold clients.
 *	The threshold value must be greater than 1. This is to prevent 
 * 	accidental listing of the large number of single client sessions.
 *
 * Syntax: SESSION VIEW host
 *	Displays detailed session information about the supplied host.
 */

int do_session(User * u)
{
    Session *session;
    Exception *exception;
    char *cmd = strtok(NULL, " ");
    char *param1 = strtok(NULL, " ");
    int mincount;
    int i;

    if (!LimitSessions) {
        notice_lang(s_OperServ, u, OPER_SESSION_DISABLED);
        return MOD_CONT;
    }

    if (!cmd)
        cmd = "";

    if (stricmp(cmd, "LIST") == 0) {
        if (!param1) {
            syntax_error(s_OperServ, u, "SESSION",
                         OPER_SESSION_LIST_SYNTAX);

        } else if ((mincount = atoi(param1)) <= 1) {
            notice_lang(s_OperServ, u, OPER_SESSION_INVALID_THRESHOLD);

        } else {
            notice_lang(s_OperServ, u, OPER_SESSION_LIST_HEADER, mincount);
            notice_lang(s_OperServ, u, OPER_SESSION_LIST_COLHEAD);
            for (i = 0; i < 1024; i++) {
                for (session = sessionlist[i]; session;
                     session = session->next) {
                    if (session->count >= mincount)
                        notice_lang(s_OperServ, u,
                                    OPER_SESSION_LIST_FORMAT,
                                    session->count, session->host);
                }
            }
        }
    } else if (stricmp(cmd, "VIEW") == 0) {
        if (!param1) {
            syntax_error(s_OperServ, u, "SESSION",
                         OPER_SESSION_VIEW_SYNTAX);

        } else {
            session = findsession(param1);
            if (!session) {
                notice_lang(s_OperServ, u, OPER_SESSION_NOT_FOUND, param1);
            } else {
                exception = find_host_exception(param1);

                notice_lang(s_OperServ, u, OPER_SESSION_VIEW_FORMAT,
                            param1, session->count,
                            exception ? exception->
                            limit : DefSessionLimit);
            }
        }

    } else {
        syntax_error(s_OperServ, u, "SESSION", OPER_SESSION_SYNTAX);
    }
    return MOD_CONT;
}

/*************************************************************************/
/********************* Internal Session Functions ************************/
/*************************************************************************/

static Session *findsession(const char *host)
{
    Session *session;
    int i;

    if (!host)
        return NULL;

    for (i = 0; i < 1024; i++) {
        for (session = sessionlist[i]; session; session = session->next) {
            if (stricmp(host, session->host) == 0) {
                return session;
            }
        }
    }

    return NULL;
}

/* Attempt to add a host to the session list. If the addition of the new host
 * causes the the session limit to be exceeded, kill the connecting user.
 * Returns 1 if the host was added or 0 if the user was killed.
 */

int add_session(const char *nick, const char *host)
{
    Session *session, **list;
    Exception *exception;
    int sessionlimit = 0;

    session = findsession(host);

    if (session) {
        exception = find_host_exception(host);
        if (checkDefCon(DEFCON_REDUCE_SESSION)) {
            sessionlimit =
                exception ? exception->limit : DefConSessionLimit;
        } else {
            sessionlimit = exception ? exception->limit : DefSessionLimit;
        }

        if (sessionlimit != 0 && session->count >= sessionlimit) {
            if (SessionLimitExceeded)
                notice(s_OperServ, nick, SessionLimitExceeded, host);
            if (SessionLimitDetailsLoc)
                notice(s_OperServ, nick, SessionLimitDetailsLoc);

            /* We don't use kill_user() because a user stucture has not yet
             * been created. Simply kill the user. -TheShadow
             */
#ifdef IRC_BAHAMUT
            send_cmd(NULL, "SVSKILL %s :Session limit exceeded", nick);
#else
            send_cmd(s_OperServ, "KILL %s :%s (Session limit exceeded)",
                     nick, s_OperServ);
#endif
            session->hits++;
            if (MaxSessionKill && session->hits >= MaxSessionKill) {
                char akillmask[BUFSIZE];
                snprintf(akillmask, sizeof(akillmask), "*@%s", host);
                add_akill(NULL, akillmask, s_OperServ,
                          time(NULL) + SessionAutoKillExpiry,
                          "Session limit exceeded");
                wallops(s_OperServ,
                        "Added a temporary AKILL for \2%s\2 due to excessive connections",
                        akillmask);
            }
            return 0;
        } else {
            session->count++;
            return 1;
        }
    }

    nsessions++;
    session = scalloc(sizeof(Session), 1);
    session->host = sstrdup(host);
    list = &sessionlist[HASH(session->host)];
    session->next = *list;
    if (*list)
        (*list)->prev = session;
    *list = session;
    session->count = 1;

    return 1;
}

void del_session(const char *host)
{
    Session *session;

    if (debug >= 2)
        alog("debug: del_session() called");

    session = findsession(host);

    if (!session) {
        wallops(s_OperServ,
                "WARNING: Tried to delete non-existant session: \2%s",
                host);
        alog("session: Tried to delete non-existant session: %s", host);
        return;
    }

    if (session->count > 1) {
        session->count--;
        return;
    }

    if (session->prev)
        session->prev->next = session->next;
    else
        sessionlist[HASH(session->host)] = session->next;
    if (session->next)
        session->next->prev = session->prev;

    if (debug >= 2)
        alog("debug: del_session(): free session structure");

    free(session->host);
    free(session);

    nsessions--;

    if (debug >= 2)
        alog("debug: del_session() done");
}


/*************************************************************************/
/********************** Internal Exception Functions *********************/
/*************************************************************************/

void expire_exceptions(void)
{
    int i;
    time_t now = time(NULL);

    for (i = 0; i < nexceptions; i++) {
        if (exceptions[i].expires == 0 || exceptions[i].expires > now)
            continue;
        if (WallExceptionExpire)
            wallops(s_OperServ,
                    "Session limit exception for %s has expired.",
                    exceptions[i].mask);
        free(exceptions[i].mask);
        free(exceptions[i].reason);
        nexceptions--;
        memmove(exceptions + i, exceptions + i + 1,
                sizeof(Exception) * (nexceptions - i));
        exceptions = srealloc(exceptions, sizeof(Exception) * nexceptions);
        i--;
    }
}

/* Find the first exception this host matches and return it. */

Exception *find_host_exception(const char *host)
{
    int i;

    for (i = 0; i < nexceptions; i++) {
        if (match_wild_nocase(exceptions[i].mask, host)) {
            return &exceptions[i];
        }
    }

    return NULL;
}

/*************************************************************************/
/*********************** Exception Load/Save *****************************/
/*************************************************************************/

#define SAFE(x) do {                                    \
    if ((x) < 0) {                                      \
        if (!forceload)                                 \
            fatal("Read error on %s", ExceptionDBName); \
        nexceptions = i;                                \
        break;                                          \
    }                                                   \
} while (0)

void load_exceptions()
{
    dbFILE *f;
    int i;
    int16 n;
    int16 tmp16;
    int32 tmp32;

    if (!
        (f = open_db(s_OperServ, ExceptionDBName, "r", EXCEPTION_VERSION)))
        return;
    switch (i = get_file_version(f)) {
    case 9:
    case 8:
    case 7:
        SAFE(read_int16(&n, f));
        nexceptions = n;
        exceptions = scalloc(sizeof(Exception) * nexceptions, 1);
        if (!nexceptions) {
            close_db(f);
            return;
        }
        for (i = 0; i < nexceptions; i++) {
            SAFE(read_string(&exceptions[i].mask, f));
            SAFE(read_int16(&tmp16, f));
            exceptions[i].limit = tmp16;
            SAFE(read_buffer(exceptions[i].who, f));
            SAFE(read_string(&exceptions[i].reason, f));
            SAFE(read_int32(&tmp32, f));
            exceptions[i].time = tmp32;
            SAFE(read_int32(&tmp32, f));
            exceptions[i].expires = tmp32;
        }
        break;

    default:
        fatal("Unsupported version (%d) on %s", i, ExceptionDBName);
    }                           /* switch (ver) */

    close_db(f);
}

#undef SAFE

/*************************************************************************/

#define SAFE(x) do {                                            \
    if ((x) < 0) {                                              \
        restore_db(f);                                          \
        log_perror("Write error on %s", ExceptionDBName);       \
        if (time(NULL) - lastwarn > WarningTimeout) {           \
            wallops(NULL, "Write error on %s: %s", ExceptionDBName,  \
                        strerror(errno));                       \
            lastwarn = time(NULL);                              \
        }                                                       \
        return;                                                 \
    }                                                           \
} while (0)

void save_exceptions()
{
    dbFILE *f;
    int i;
    static time_t lastwarn = 0;

    if (!
        (f = open_db(s_OperServ, ExceptionDBName, "w", EXCEPTION_VERSION)))
        return;
    SAFE(write_int16(nexceptions, f));
    for (i = 0; i < nexceptions; i++) {
        SAFE(write_string(exceptions[i].mask, f));
        SAFE(write_int16(exceptions[i].limit, f));
        SAFE(write_buffer(exceptions[i].who, f));
        SAFE(write_string(exceptions[i].reason, f));
        SAFE(write_int32(exceptions[i].time, f));
        SAFE(write_int32(exceptions[i].expires, f));
    }
    close_db(f);
}

#undef SAFE

/*************************************************************************/

void save_rdb_exceptions()
{
#ifdef USE_RDB
    int i;
    Exception *e;

    if (!rdb_open())
        return;
    rdb_clear_table("anope_os_exceptions");
    for (i = 0; i < nexceptions; i++) {
        e = &exceptions[i];
        rdb_save_exceptions(e);
    }
    rdb_close();
#endif
}

/*************************************************************************/
/************************ Exception Manipulation *************************/
/*************************************************************************/

static int exception_add(const char *mask, const int limit,
                         const char *reason, const char *who,
                         const time_t expires)
{
    int i;

    /* Check if an exception already exists for this mask */
    for (i = 0; i < nexceptions; i++)
        if (stricmp(mask, exceptions[i].mask) == 0)
            return 0;

    nexceptions++;
    exceptions = srealloc(exceptions, sizeof(Exception) * nexceptions);

    exceptions[nexceptions - 1].mask = sstrdup(mask);
    exceptions[nexceptions - 1].limit = limit;
    exceptions[nexceptions - 1].reason = sstrdup(reason);
    exceptions[nexceptions - 1].time = time(NULL);
    strscpy(exceptions[nexceptions - 1].who, who, NICKMAX);
    exceptions[nexceptions - 1].expires = expires;
    exceptions[nexceptions - 1].num = nexceptions - 1;

    return 1;
}

/*************************************************************************/

static int exception_del(const int index)
{
    if (index < 0 || index >= nexceptions)
        return 0;

    free(exceptions[index].mask);
    free(exceptions[index].reason);
    nexceptions--;
    memmove(exceptions + index, exceptions + index + 1,
            sizeof(Exception) * (nexceptions - index));
    exceptions = srealloc(exceptions, sizeof(Exception) * nexceptions);

    return 1;
}

/* We use the "num" property to keep track of the position of each exception
 * when deleting using ranges. This is because an exception's position changes
 * as others are deleted. The positions will be recalculated once the process
 * is complete. -TheShadow
 */

static int exception_del_callback(User * u, int num, va_list args)
{
    int i;
    int *last = va_arg(args, int *);

    *last = num;
    for (i = 0; i < nexceptions; i++) {
        if (num - 1 == exceptions[i].num)
            break;
    }
    if (i < nexceptions)
        return exception_del(i);
    else
        return 0;
}

static int exception_list(User * u, const int index, int *sent_header)
{
    if (index < 0 || index >= nexceptions)
        return 0;
    if (!*sent_header) {
        notice_lang(s_OperServ, u, OPER_EXCEPTION_LIST_HEADER);
        notice_lang(s_OperServ, u, OPER_EXCEPTION_LIST_COLHEAD);
        *sent_header = 1;
    }
    notice_lang(s_OperServ, u, OPER_EXCEPTION_LIST_FORMAT, index + 1,
                exceptions[index].limit, exceptions[index].mask);
    return 1;
}

static int exception_list_callback(User * u, int num, va_list args)
{
    int *sent_header = va_arg(args, int *);

    return exception_list(u, num - 1, sent_header);
}

static int exception_view(User * u, const int index, int *sent_header)
{
    char timebuf[32], expirebuf[256];
    struct tm tm;
    time_t t = time(NULL);

    if (index < 0 || index >= nexceptions)
        return 0;
    if (!*sent_header) {
        notice_lang(s_OperServ, u, OPER_EXCEPTION_LIST_HEADER);
        *sent_header = 1;
    }

    tm = *localtime(exceptions[index].time ? &exceptions[index].time : &t);
    strftime_lang(timebuf, sizeof(timebuf),
                  u, STRFTIME_SHORT_DATE_FORMAT, &tm);

    expire_left(u->na, expirebuf, sizeof(expirebuf),
                exceptions[index].expires);

    notice_lang(s_OperServ, u, OPER_EXCEPTION_VIEW_FORMAT,
                index + 1, exceptions[index].mask,
                *exceptions[index].who ?
                exceptions[index].who : "<unknown>",
                timebuf, expirebuf, exceptions[index].limit,
                exceptions[index].reason);
    return 1;
}

static int exception_view_callback(User * u, int num, va_list args)
{
    int *sent_header = va_arg(args, int *);

    return exception_view(u, num - 1, sent_header);
}

/*************************************************************************/

/* Syntax: EXCEPTION ADD [+expiry] mask limit reason
 *	Adds mask to the exception list with limit as the maximum session
 *	limit and +expiry as an optional expiry time.
 *
 * Syntax: EXCEPTION DEL mask
 *	Deletes the first exception that matches mask exactly.
 *
 * Syntax: EXCEPTION LIST [mask]
 *	Lists all exceptions or those matching mask.
 *
 * Syntax: EXCEPTION VIEW [mask]
 *	Displays detailed information about each exception or those matching
 *	mask.
 *
 * Syntax: EXCEPTION MOVE num position
 *	Moves the exception at position num to position.
 */

int do_exception(User * u)
{
    char *cmd = strtok(NULL, " ");
    char *mask, *reason, *expiry, *limitstr;
    int limit, expires;
    int i;

    if (!LimitSessions) {
        notice_lang(s_OperServ, u, OPER_EXCEPTION_DISABLED);
        return MOD_CONT;
    }

    if (!cmd)
        cmd = "";

    if (stricmp(cmd, "ADD") == 0) {
        if (nexceptions >= 32767) {
            notice_lang(s_OperServ, u, OPER_EXCEPTION_TOO_MANY);
            return MOD_CONT;
        }

        mask = strtok(NULL, " ");
        if (mask && *mask == '+') {
            expiry = mask;
            mask = strtok(NULL, " ");
        } else {
            expiry = NULL;
        }
        limitstr = strtok(NULL, " ");
        reason = strtok(NULL, "");

        if (!reason) {
            syntax_error(s_OperServ, u, "EXCEPTION",
                         OPER_EXCEPTION_ADD_SYNTAX);
            return MOD_CONT;
        }

        expires = expiry ? dotime(expiry) : ExceptionExpiry;
        if (expires < 0) {
            notice_lang(s_OperServ, u, BAD_EXPIRY_TIME);
            return MOD_CONT;
        } else if (expires > 0) {
            expires += time(NULL);
        }

        limit = (limitstr && isdigit(*limitstr)) ? atoi(limitstr) : -1;

        if (limit < 0 || limit > MaxSessionLimit) {
            notice_lang(s_OperServ, u, OPER_EXCEPTION_INVALID_LIMIT,
                        MaxSessionLimit);
            return MOD_CONT;

        } else {
            if (strchr(mask, '!') || strchr(mask, '@')) {
                notice_lang(s_OperServ, u,
                            OPER_EXCEPTION_INVALID_HOSTMASK);
                return MOD_CONT;
            }

            if (exception_add(mask, limit, reason, u->nick, expires))
                notice_lang(s_OperServ, u, OPER_EXCEPTION_ADDED, mask,
                            limit);
            else
                notice_lang(s_OperServ, u, OPER_EXCEPTION_ALREADY_PRESENT,
                            mask, limit);
            if (readonly)
                notice_lang(s_OperServ, u, READ_ONLY_MODE);
        }
    } else if (stricmp(cmd, "DEL") == 0) {
        mask = strtok(NULL, " ");

        if (!mask) {
            syntax_error(s_OperServ, u, "EXCEPTION",
                         OPER_EXCEPTION_DEL_SYNTAX);
            return MOD_CONT;
        }

        if (isdigit(*mask) && strspn(mask, "1234567890,-") == strlen(mask)) {
            int count, deleted, last = -1;
            deleted =
                process_numlist(mask, &count, exception_del_callback, u,
                                &last);
            if (!deleted) {
                if (count == 1) {
                    notice_lang(s_OperServ, u,
                                OPER_EXCEPTION_NO_SUCH_ENTRY, last);
                } else {
                    notice_lang(s_OperServ, u, OPER_EXCEPTION_NO_MATCH);
                }
            } else if (deleted == 1) {
                notice_lang(s_OperServ, u, OPER_EXCEPTION_DELETED_ONE);
            } else {
                notice_lang(s_OperServ, u, OPER_EXCEPTION_DELETED_SEVERAL,
                            deleted);
            }
        } else {
            int deleted = 0;

            for (i = 0; i < nexceptions; i++) {
                if (stricmp(mask, exceptions[i].mask) == 0) {
                    exception_del(i);
                    notice_lang(s_OperServ, u, OPER_EXCEPTION_DELETED,
                                mask);
                    deleted = 1;
                    break;
                }
            }
            if (!deleted && i == nexceptions)
                notice_lang(s_OperServ, u, OPER_EXCEPTION_NOT_FOUND, mask);
        }

        /* Renumber the exception list. I don't believe in having holes in 
         * lists - it makes code more complex, harder to debug and we end up 
         * with huge index numbers. Imho, fixed numbering is only beneficial
         * when one doesn't have range capable manipulation. -TheShadow */

        for (i = 0; i < nexceptions; i++)
            exceptions[i].num = i;

        if (readonly)
            notice_lang(s_OperServ, u, READ_ONLY_MODE);

    } else if (stricmp(cmd, "MOVE") == 0) {
        Exception *exception;
        char *n1str = strtok(NULL, " ");        /* From position */
        char *n2str = strtok(NULL, " ");        /* To position */
        int n1, n2;

        if (!n2str) {
            syntax_error(s_OperServ, u, "EXCEPTION",
                         OPER_EXCEPTION_MOVE_SYNTAX);
            return MOD_CONT;
        }

        n1 = atoi(n1str) - 1;
        n2 = atoi(n2str) - 1;

        if ((n1 >= 0 && n1 < nexceptions) && (n2 >= 0 && n2 < nexceptions)
            && (n1 != n2)) {
            exception = scalloc(sizeof(Exception), 1);
            memcpy(exception, &exceptions[n1], sizeof(Exception));

            if (n1 < n2) {
                /* Shift upwards */
                memmove(&exceptions[n1], &exceptions[n1 + 1],
                        sizeof(Exception) * (n2 - n1));
                memmove(&exceptions[n2], exception, sizeof(Exception));
            } else {
                /* Shift downwards */
                memmove(&exceptions[n2 + 1], &exceptions[n2],
                        sizeof(Exception) * (n1 - n2));
                memmove(&exceptions[n2], exception, sizeof(Exception));
            }

            free(exception);

            notice_lang(s_OperServ, u, OPER_EXCEPTION_MOVED,
                        exceptions[n1].mask, n1 + 1, n2 + 1);

            /* Renumber the exception list. See the DEL block above for why. */
            for (i = 0; i < nexceptions; i++)
                exceptions[i].num = i;

            if (readonly)
                notice_lang(s_OperServ, u, READ_ONLY_MODE);
        } else {
            syntax_error(s_OperServ, u, "EXCEPTION",
                         OPER_EXCEPTION_MOVE_SYNTAX);
        }
    } else if (stricmp(cmd, "LIST") == 0) {
        int sent_header = 0;
        expire_exceptions();
        mask = strtok(NULL, " ");
        if (mask && strspn(mask, "1234567890,-") == strlen(mask)) {
            process_numlist(mask, NULL, exception_list_callback, u,
                            &sent_header);
        } else {
            for (i = 0; i < nexceptions; i++) {
                if (!mask || match_wild_nocase(mask, exceptions[i].mask))
                    exception_list(u, i, &sent_header);
            }
        }
        if (!sent_header)
            notice_lang(s_OperServ, u, OPER_EXCEPTION_NO_MATCH);

    } else if (stricmp(cmd, "VIEW") == 0) {
        int sent_header = 0;
        expire_exceptions();
        mask = strtok(NULL, " ");
        if (mask && strspn(mask, "1234567890,-") == strlen(mask)) {
            process_numlist(mask, NULL, exception_view_callback, u,
                            &sent_header);
        } else {
            for (i = 0; i < nexceptions; i++) {
                if (!mask || match_wild_nocase(mask, exceptions[i].mask))
                    exception_view(u, i, &sent_header);
            }
        }
        if (!sent_header)
            notice_lang(s_OperServ, u, OPER_EXCEPTION_NO_MATCH);

    } else {
        syntax_error(s_OperServ, u, "EXCEPTION", OPER_EXCEPTION_SYNTAX);
    }
    return MOD_CONT;
}

/*************************************************************************/