/*

Copyright (c) 2007 Carl Byington - 510 Software Group, released under
the GPL version 3 or any later version at your choice available at
http://www.gnu.org/licenses/gpl-3.0.txt

Based on a sample milter Copyright (c) 2000-2003 Sendmail, Inc. and its
suppliers.

-p port  The port through which the MTA will connect to this milter.
-t sec   The timeout value.
-c       Check the config, and print a copy to stdout. Don't start the
         milter or do anything with the socket.
-d       increase debug level

*/


// from sendmail sample
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <sysexits.h>
#include <unistd.h>

// needed for thread
#include <pthread.h>

// needed for std c++ collections
#include <set>
#include <map>
#include <list>

// misc stuff needed here
#include <ctype.h>
#include <syslog.h>
#include <pwd.h>
#include <sys/wait.h>   /* header for waitpid() and various macros */
#include <signal.h>     /* header for signal functions */

#include "includes.h"

#ifndef HAVE_DAEMON
    #include "daemon.h"
    #include "daemon.c"
#endif

extern "C" {
    #include <libmilter/mfapi.h>
    sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr);
    sfsistat mlfi_envfrom(SMFICTX *ctx, char **argv);
    sfsistat mlfi_envrcpt(SMFICTX *ctx, char **argv);
    sfsistat mlfi_eom(SMFICTX *ctx);
    sfsistat mlfi_abort(SMFICTX *ctx);
    sfsistat mlfi_close(SMFICTX *ctx);
    void sig_chld(int signo);
}

// command line options
const char  *optionConfigFile = "sm-archive.conf" ;
const char  *optionPidFile    = "/var/run/sm-archive.pid" ;
int  debug_syslog  = 0;
//
bool syslog_opened = false;
bool use_syslog    = true;  // false to printf
bool loader_run    = true;  // used to stop the config loader thread
CONFIG   *config = NULL;    // protected by the config_mutex
int   generation = 0;       // protected by the config_mutex
const int maxlen = 1000;    // used for snprintf buffers

pthread_mutex_t  config_mutex;
pthread_mutex_t  syslog_mutex;


mlfiPriv::mlfiPriv() {
    pthread_mutex_lock(&config_mutex);
        pc = config;
        pc->reference_count++;
    pthread_mutex_unlock(&config_mutex);
    mailaddr = NULL;
    queueid  = NULL;
}

mlfiPriv::~mlfiPriv() {
    pthread_mutex_lock(&config_mutex);
        pc->reference_count--;
    pthread_mutex_unlock(&config_mutex);
    reset(true);
}

void mlfiPriv::reset(bool final) {
    targets.clear();
    for (string_set::iterator i=removal.begin(); i!=removal.end(); i++) {
        const char *remove = (*i);
        free((void*)remove);
    }
    removal.clear();
    if (mailaddr) free((void*)mailaddr);
    if (queueid)  free((void*)queueid);
    if (!final) {
        mailaddr = NULL;
        queueid  = NULL;
    }
}

#define MLFIPRIV    ((struct mlfiPriv *) smfi_getpriv(ctx))


////////////////////////////////////////////////
// syslog a message
//
void my_syslog(mlfiPriv *priv, const char *text) {
    char buf[maxlen];
    if (priv) {
        snprintf(buf, sizeof(buf), "%s: %s",
            priv->queueid ? priv->queueid : "NOQUEUE", text);
        text = buf;
    }
    if (use_syslog) {
        pthread_mutex_lock(&syslog_mutex);
            if (!syslog_opened) {
                openlog("sm-archive", LOG_PID, LOG_MAIL);
                syslog_opened = true;
            }
            syslog(LOG_NOTICE, "%s", text);
        pthread_mutex_unlock(&syslog_mutex);
    }
    else {
        printf("%s \n", text);
    }
}

void my_syslog(const char *text) {
    my_syslog(NULL, text);
}


////////////////////////////////////////////////
// this email address is passed in from sendmail, and will
// always be enclosed in <>. It may have mixed case, just
// as the mail client sent it. We dup the string and convert
// the duplicate to lower case.
// Postfix will return addresses without <> if they have been provided
// this way in the SMTP dialog.
//
const char *to_lower_string(const char *email);
const char *to_lower_string(const char *email) {
    char *key, *p;
    int i;

    if (strcmp(email, "<>") == 0) return strdup(email);
    if (email[0] == '<') p = (char *) email + 1;
    else                 p = (char *) email;
    key = (char *) malloc(strlen(p) + 1);
    for (i = 0; p[i] != '\0'; i++) key[i] = tolower(p[i]);
    if (p[i - 1] == '>') i--;
    key[i] = '\0';
    return key;
}


////////////////////////////////////////////////
// start of sendmail milter interfaces
//
sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr)
{
    // allocate some private memory
    mlfiPriv *priv = new mlfiPriv;
    // save the private data
    smfi_setpriv(ctx, (void*)priv);
    // continue processing
    return SMFIS_CONTINUE;
}

sfsistat mlfi_envfrom(SMFICTX *ctx, char **from)
{
    mlfiPriv &priv = *MLFIPRIV;
    priv.mailaddr  = to_lower_string(from[0]);
    return SMFIS_CONTINUE;
}

void add_target(mlfiPriv &priv, const char *target);
void add_target(mlfiPriv &priv, const char *target)
{
    if (target) {
        string_set::iterator i = priv.targets.find(target);
        if (i == priv.targets.end()) priv.targets.insert(target);
    }
}

void add_remove(mlfiPriv &priv, const char *remove);
void add_remove(mlfiPriv &priv, const char *remove)
{
    if (remove) {
        string_set::iterator i = priv.removal.find(remove);
        if (i == priv.removal.end()) priv.removal.insert(remove);
    }
}

sfsistat mlfi_envrcpt(SMFICTX *ctx, char **rcpt)
{
    mlfiPriv &priv = *MLFIPRIV;
    CONFIG &dc = *priv.pc;
    const char *i_macro = smfi_getsymval(ctx, (char*)"i");
    if (!priv.queueid && i_macro) priv.queueid = strdup(i_macro);
    const char *rcptaddr    = to_lower_string(rcpt[0]);
    if (debug_syslog > 1) {
        char msg[maxlen];
        snprintf(msg, sizeof(msg), "from <%s> to <%s>", priv.mailaddr, rcptaddr);
        my_syslog(&priv, msg);
    }
    const char *target = dc.find_to(rcptaddr);
    add_target(priv, target);
    bool remove  = dc.find_remove(rcptaddr);
    if (remove) add_remove(priv, strdup(rcptaddr));
    free((void*)rcptaddr);
    return SMFIS_CONTINUE;
}

sfsistat mlfi_eom(SMFICTX *ctx)
{
    mlfiPriv &priv = *MLFIPRIV;
    CONFIG &dc = *priv.pc;
    const char *i_macro = smfi_getsymval(ctx, (char*)"i");
    if (!priv.queueid && i_macro) priv.queueid = strdup(i_macro);
    const char *target = dc.find_from(priv.mailaddr);
    add_target(priv, target);
    for (string_set::iterator i=priv.targets.begin(); i!=priv.targets.end(); i++) {
        target = (*i);
        smfi_addrcpt(ctx, (char*)target);
        if (debug_syslog > 1) {
            char msg[maxlen];
            snprintf(msg, sizeof(msg), "adding recipient <%s>", target);
            my_syslog(&priv, msg);
        }
    }
    for (string_set::iterator i=priv.removal.begin(); i!=priv.removal.end(); i++) {
        const char *remove = (*i);
        smfi_delrcpt(ctx, (char*)remove);
        if (debug_syslog > 1) {
            char msg[maxlen];
            snprintf(msg, sizeof(msg), "removing recipient <%s>", remove);
            my_syslog(&priv, msg);
        }
    }
    // reset for a new message on the same connection
    mlfi_abort(ctx);
    return SMFIS_CONTINUE;
}

sfsistat mlfi_abort(SMFICTX *ctx)
{
    mlfiPriv &priv = *MLFIPRIV;
    priv.reset();
    return SMFIS_CONTINUE;
}

sfsistat mlfi_close(SMFICTX *ctx)
{
    mlfiPriv *priv = MLFIPRIV;
    if (!priv) return SMFIS_CONTINUE;
    delete priv;
    smfi_setpriv(ctx, NULL);
    return SMFIS_CONTINUE;
}

struct smfiDesc smfilter =
{
    (char*)"SM-ARCHIVE",// filter name
    SMFI_VERSION,       // version code -- do not change
    SMFIF_ADDRCPT | \
    SMFIF_DELRCPT,      // flags
    mlfi_connect,       // connection info filter
    NULL,               // SMTP HELO command filter
    mlfi_envfrom,       // envelope sender filter
    mlfi_envrcpt,       // envelope recipient filter
    NULL,               // header filter
    NULL,               // end of header
    NULL,               // body block filter
    mlfi_eom,           // end of message
    mlfi_abort,         // message aborted
    mlfi_close,         // connection cleanup
};


////////////////////////////////////////////////
//  reload the config
//
CONFIG* new_conf();
CONFIG* new_conf() {
    CONFIG *newc = new CONFIG;
    pthread_mutex_lock(&config_mutex);
        newc->generation = generation++;
    pthread_mutex_unlock(&config_mutex);
    if (debug_syslog) {
        char buf[maxlen];
        snprintf(buf, sizeof(buf), "loading configuration generation %d", newc->generation);
        my_syslog(buf);
    }
    if (load_conf(*newc, optionConfigFile)) {
        newc->load_time = time(NULL);
        return newc;
    }
    delete newc;
    return NULL;
}


////////////////////////////////////////////////
//  thread to watch the old config files for changes
//  and reload when needed. we also cleanup old
//  configs whose reference count has gone to zero.
//
extern "C" {void* config_loader(void *arg);}
void* config_loader(void *arg) {
    while (loader_run) {
        sleep(180);  // look for modifications every 3 minutes
        if (!loader_run) break;
        CONFIG &dc = *config;
        time_t then = dc.load_time;
        struct stat st;
        bool reload = false;
        for (string_set::iterator i=dc.config_files.begin(); i!=dc.config_files.end(); i++) {
            const char *fn = *i;
            if (stat(fn, &st))           reload = true; // file disappeared
            else if (st.st_mtime > then) reload = true; // file modified
            if (reload) break;
        }
        if (reload) {
            CONFIG *newc = new_conf();
            if (newc) {
                // replace the global config pointer
                pthread_mutex_lock(&config_mutex);
                    CONFIG *old = config;
                    bool last = old && (!old->reference_count);
                    config = newc;
                pthread_mutex_unlock(&config_mutex);
                if (last) delete old;   // there were no references to this config
            }
            else {
                // failed to load new config
                my_syslog("failed to load new configuration");
                system("echo 'failed to load new sm-archive configuration from /etc/sm-archive' | mail -s 'error in /etc/sm-archive configuration' root");
                // update the load time on the current config to prevent complaining every 3 minutes
                dc.load_time = time(NULL);
            }
        }
    }
    return NULL;
}


void usage(const char *prog);
void usage(const char *prog)
{
    fprintf(stderr, "Usage: %s  [-d [level]] [-c] -p sm-sock-addr [-t timeout] [-C config-file] [-P pid-file]\n", prog);
    fprintf(stderr, "where sm-sock-addr is for the connection to sendmail\n");
    fprintf(stderr, "    and should be one of\n");
    fprintf(stderr, "        inet:port@ip-address\n");
    fprintf(stderr, "        local:local-domain-socket-file-name\n");
    fprintf(stderr, "-c will load and dump the config to stdout\n");
    fprintf(stderr, "-d will set the syslog message level, currently 0 to 3\n");
    fprintf(stderr, "-C specifies the config file, defaults to sm-archive.conf\n");
    fprintf(stderr, "-P specifies the pid file, defaults to /var/run/sm-archive.pid\n");
}



void setup_socket(const char *sock);
void setup_socket(const char *sock) {
    unlink(sock);
    //  sockaddr_un addr;
    //  memset(&addr, '\0', sizeof addr);
    //  addr.sun_family = AF_UNIX;
    //  strncpy(addr.sun_path, sock, sizeof(addr.sun_path)-1);
    //  int s = socket(AF_UNIX, SOCK_STREAM, 0);
    //  bind(s, (sockaddr*)&addr, sizeof(addr));
    //  close(s);
}


/*
 * The signal handler function -- only gets called when a SIGCHLD
 * is received, ie when a child terminates
 */
void sig_chld(int signo)
{
    int status;
    /* Wait for any child without blocking */
    while (waitpid(-1, &status, WNOHANG) > 0) {
        // ignore child exit status, we only do this to cleanup zombies
    }
}


int main(int argc, char**argv)
{
    token_init();
    bool check   = false;
    bool setconn = false;
    int c;
    const char *args = "p:t:d:chC:P:";
    extern char *optarg;

    // Process command line options
    while ((c = getopt(argc, argv, args)) != -1) {
        switch (c) {
            case 'p':
                if (optarg == NULL || *optarg == '\0') {
                    fprintf(stderr, "Illegal sendmail socket: %s\n", optarg);
                    exit(EX_USAGE);
                }
                if (smfi_setconn(optarg) == MI_FAILURE) {
                    fprintf(stderr, "smfi_setconn failed\n");
                    exit(EX_SOFTWARE);
                }
                     if (strncasecmp(optarg, "unix:", 5) == 0)  setup_socket(optarg + 5);
                else if (strncasecmp(optarg, "local:", 6) == 0) setup_socket(optarg + 6);
                setconn = true;
                break;

            case 't':
                if (optarg == NULL || *optarg == '\0') {
                    fprintf(stderr, "Illegal timeout: %s\n", optarg);
                    exit(EX_USAGE);
                }
                if (smfi_settimeout(atoi(optarg)) == MI_FAILURE) {
                    fprintf(stderr, "smfi_settimeout failed\n");
                    exit(EX_SOFTWARE);
                }
                break;

            case 'c':
                check = true;
                break;

            case 'd':
                if (optarg == NULL || *optarg == '\0') debug_syslog = 1;
                else                                   debug_syslog = atoi(optarg);
                break;

            case 'C':
                if (optarg == NULL || *optarg == '\0') {
                    fprintf( stderr, "Must specify the config file path: %s\n", optarg );
                    exit(EX_USAGE);
                }
                optionConfigFile = optarg ;
                break ;

            case 'P':
                if (optarg == NULL || *optarg == '\0') {
                    fprintf( stderr, "Must specify the pid file path: %s\n", optarg );
                    exit(EX_USAGE);
                }
                optionPidFile = optarg ;
                break ;

            case 'h':
            default:
                usage(argv[0]);
                exit(EX_USAGE);
        }
    }

    if (check) {
        use_syslog   = false;
        debug_syslog = 10;
        CONFIG *conf = new_conf();
        if (conf) {
            conf->dump();
            delete conf;
            clear_strings();    // for valgrind checking
            return 0;
        }
        else {
            return 1;   // config failed to load
        }
    }

    if (!setconn) {
        fprintf(stderr, "%s: Missing required -p argument\n", argv[0]);
        usage(argv[0]);
        exit(EX_USAGE);
    }

    if (smfi_register(smfilter) == MI_FAILURE) {
        fprintf(stderr, "smfi_register failed\n");
        exit(EX_UNAVAILABLE);
    }

    // switch to background mode
    if (daemon(1,0) < 0) {
        fprintf(stderr, "daemon() call failed\n");
        exit(EX_UNAVAILABLE);
    }

    // write the pid
    const char *pidpath = optionPidFile;
    unlink(pidpath);
    FILE *f = fopen(pidpath, "w");
    if (f) {
#ifdef linux
        // from a comment in the DCC source code:
        // Linux threads are broken.  Signals given the
        // original process are delivered to only the
        // thread that happens to have that PID.  The
        // sendmail libmilter thread that needs to hear
        // SIGINT and other signals does not, and that breaks
        // scripts that need to stop milters.
        // However, signaling the process group works.
        fprintf(f, "-%d\n", (u_int)getpgrp());
#else
        fprintf(f, "%d\n", (u_int)getpid());
#endif
        fclose(f);
    }

    // initialize the thread sync objects
    pthread_mutex_init(&config_mutex, 0);
    pthread_mutex_init(&syslog_mutex, 0);

    // drop root privs
    struct passwd *pw = getpwnam("sm-archive");
    if (pw) {
        if (setgid(pw->pw_gid) == -1) {
            my_syslog("failed to switch to group sm-archive");
        }
        if (setuid(pw->pw_uid) == -1) {
            my_syslog("failed to switch to user sm-archive");
        }
    }

    // load the initial config
    config = new_conf();
    if (!config) {
        my_syslog("failed to load initial configuration, quitting");
        exit(1);
    }

    // only create threads after the fork() in daemon
    pthread_t tid;
    if (pthread_create(&tid, 0, config_loader, 0))
        my_syslog("failed to create config loader thread");
    if (pthread_detach(tid))
        my_syslog("failed to detach config loader thread");

    time_t starting = time(NULL);
    int rc = smfi_main();
    if ((rc != MI_SUCCESS) && (time(NULL) > starting+5*60)) {
        my_syslog("trying to restart after smfi_main()");
        loader_run = false;     // eventually the config loader thread will terminate
        execvp(argv[0], argv);
    }
    exit((rc == MI_SUCCESS) ? 0 : EX_UNAVAILABLE);
}