/*
 * smtp.c, SJ
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>
#include <syslog.h>
#include <time.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <piler.h>
#include <smtp.h>


void process_command_ehlo_lhlo(struct session_ctx *sctx, int *protocol_state, char *resp, int resplen){
   char tmpbuf[MAXBUFSIZE];
   char extensions[SMALLBUFSIZE];

   memset(extensions, 0, sizeof(extensions));

   if(*protocol_state == SMTP_STATE_INIT) *protocol_state = SMTP_STATE_HELO;

   if(sctx->sdata->tls == 0) snprintf(extensions, sizeof(extensions)-1, "%s", sctx->data->starttls);
   if(sctx->cfg->enable_chunking == 1) strncat(extensions, SMTP_EXTENSION_CHUNKING, sizeof(extensions)-strlen(extensions)-2);

   snprintf(tmpbuf, sizeof(tmpbuf)-1, SMTP_RESP_250_EXTENSIONS, sctx->cfg->hostid, extensions);

   strncat(resp, tmpbuf, resplen-strlen(resp));
}


void process_command_starttls(struct session_ctx *sctx, int *protocol_state, int *starttls, char *resp, int resplen){

   if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_PRIORITY, "%s: starttls request from client", sctx->sdata->ttmpfile);

   if(sctx->data->ctx){
      sctx->data->ssl = SSL_new(sctx->data->ctx);
      if(sctx->data->ssl){

         SSL_set_options(sctx->data->ssl, SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3);

         if(SSL_set_fd(sctx->data->ssl, sctx->new_sd) == 1){
            strncat(resp, SMTP_RESP_220_READY_TO_START_TLS, resplen);
            *starttls = 1;
            *protocol_state = SMTP_STATE_INIT;
            return;
         } syslog(LOG_PRIORITY, "%s: SSL_set_fd() failed", sctx->sdata->ttmpfile);
      } syslog(LOG_PRIORITY, "%s: SSL_new() failed", sctx->sdata->ttmpfile);
   } syslog(LOG_PRIORITY, "%s: SSL ctx is null!", sctx->sdata->ttmpfile);

   strncat(resp, SMTP_RESP_454_ERR_TLS_TEMP_ERROR, resplen);
}


void process_command_mail_from(struct session_ctx *sctx, int *protocol_state, char *buf, char *resp, int resplen){

   if(*protocol_state != SMTP_STATE_HELO && *protocol_state != SMTP_STATE_PERIOD && *protocol_state != SMTP_STATE_BDAT){
      strncat(resp, SMTP_RESP_503_ERR, resplen);
   }
   else {
      if(*protocol_state == SMTP_STATE_PERIOD || *protocol_state == SMTP_STATE_BDAT){
         if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_PRIORITY, "%s: initiated new transaction", sctx->sdata->ttmpfile);

         unlink(sctx->sdata->ttmpfile);
         unlink(sctx->sdata->tmpframe);

         init_session_data(sctx->sdata, sctx->cfg);
      }

      *protocol_state = SMTP_STATE_MAIL_FROM;

      snprintf(sctx->sdata->mailfrom, SMALLBUFSIZE-1, "%s\r\n", buf);

      memset(sctx->sdata->fromemail, 0, SMALLBUFSIZE);
      extractEmail(sctx->sdata->mailfrom, sctx->sdata->fromemail);

      strncat(resp, SMTP_RESP_250_OK, strlen(SMTP_RESP_250_OK));

   }

}


void process_command_rcpt_to(struct session_ctx *sctx, int *protocol_state, char *buf, char *resp, int resplen){

   if(*protocol_state == SMTP_STATE_MAIL_FROM || *protocol_state == SMTP_STATE_RCPT_TO){

      if(strlen(buf) > SMALLBUFSIZE/2){
         strncat(resp, SMTP_RESP_550_ERR_TOO_LONG_RCPT_TO, resplen);
         return;
      }

      if(sctx->sdata->num_of_rcpt_to < MAX_RCPT_TO-1){
         extractEmail(buf, sctx->sdata->rcptto[sctx->sdata->num_of_rcpt_to]);
      }

      *protocol_state = SMTP_STATE_RCPT_TO;

      if(sctx->sdata->num_of_rcpt_to < MAX_RCPT_TO-1) sctx->sdata->num_of_rcpt_to++;

      strncat(resp, SMTP_RESP_250_OK, resplen);
   }
   else {
      strncat(resp, SMTP_RESP_503_ERR, resplen);
   }
}


void process_command_data(struct session_ctx *sctx, int *protocol_state, char *resp, int resplen){

   if(*protocol_state != SMTP_STATE_RCPT_TO){
      strncat(resp, SMTP_RESP_503_ERR, resplen);
   }
   else {
      sctx->sdata->fd = open(sctx->sdata->filename, O_CREAT|O_RDWR, S_IRUSR|S_IWUSR|S_IRGRP);
      if(sctx->sdata->fd == -1){
         syslog(LOG_PRIORITY, "%s: %s", ERR_OPEN_TMP_FILE, sctx->sdata->ttmpfile);
         strncat(resp, SMTP_RESP_451_ERR, resplen);
      }
      else {
         *protocol_state = SMTP_STATE_DATA;
         strncat(resp, SMTP_RESP_354_DATA_OK, resplen-1);
      }
   }

}


void process_command_bdat(struct session_ctx *sctx, int *protocol_state, char *buf, char *resp, int resplen){
   int n, expected_bdat_len;
   char puf[MAXBUFSIZE];

   if(*protocol_state != SMTP_STATE_RCPT_TO){
      strncat(resp, SMTP_RESP_503_ERR, resplen);
      return;
   }

   sctx->bdat_rounds = 0;
   sctx->bdat_last_round = 0;

   while(sctx->bdat_last_round != 1){
      sctx->bdat_rounds++;
      expected_bdat_len = 0;

      if(sctx->bdat_rounds == 1){
         expected_bdat_len = extract_bdat_command(sctx, buf);

         sctx->sdata->fd = open(sctx->sdata->filename, O_CREAT|O_RDWR, S_IRUSR|S_IWUSR|S_IRGRP);
         if(sctx->sdata->fd == -1){
            syslog(LOG_PRIORITY, "%s: %s", ERR_OPEN_TMP_FILE, sctx->sdata->ttmpfile);
            strncat(resp, SMTP_RESP_451_ERR, resplen);
            return;
         }
         else {
            *protocol_state = SMTP_STATE_BDAT;
         }
      }
      else if(sctx->bdat_last_round != 1){
         if((n = recvtimeoutssl(sctx->new_sd, &puf[0], sizeof(puf), TIMEOUT, sctx->sdata->tls, sctx->data->ssl)) > 0){
            expected_bdat_len = extract_bdat_command(sctx, puf);
            if(expected_bdat_len <= 0 && sctx->bdat_rounds > 0) sctx->bdat_rounds--;
         }
      }

      if(expected_bdat_len > 0) sctx->sdata->tot_len += read_bdat_data(sctx, expected_bdat_len);
   }

   fsync(sctx->sdata->fd);
   close(sctx->sdata->fd);
}


int extract_bdat_command(struct session_ctx *sctx, char *buf){
   int expected_bdat_len=0;
   char *p;

   // determine if this is the last BDAT command

   p = strcasestr(buf, " LAST");
   if(p){
      sctx->bdat_last_round = 1;
      syslog(LOG_INFO, "%s: BDAT LAST", sctx->sdata->ttmpfile);
      *p = '\0';
   }

   // determine the size to be read

   p = strchr(buf, ' ');
   if(p){
      expected_bdat_len = atoi(p);
      if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_INFO, "%s: BDAT len=%d", sctx->sdata->ttmpfile, expected_bdat_len);
   }

   if(!p || expected_bdat_len <= 0){
      syslog(LOG_INFO, "%s: malformed BDAT command", sctx->sdata->ttmpfile);
      return -1;
   }

   return expected_bdat_len;
}


int read_bdat_data(struct session_ctx *sctx, int expected_bdat_len){
   int n, read_bdat_len=0, written_bdat_len=0;
   char puf[MAXBUFSIZE];

   while(read_bdat_len < expected_bdat_len){
      if((n = recvtimeoutssl(sctx->new_sd, &puf[0], sizeof(puf), TIMEOUT, sctx->sdata->tls, sctx->data->ssl)) > 0){
         read_bdat_len += n;
         written_bdat_len += write(sctx->sdata->fd, puf, n);
      }
   }

   if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_INFO, "%s: wrote %d bytes of BDAT data", sctx->sdata->ttmpfile, written_bdat_len);

   return written_bdat_len;
}


void process_command_quit(struct session_ctx *sctx, int *protocol_state, char *resp, int resplen){
   char tmpbuf[MAXBUFSIZE];

   *protocol_state = SMTP_STATE_FINISHED;

   snprintf(tmpbuf, sizeof(tmpbuf)-1, SMTP_RESP_221_GOODBYE, sctx->cfg->hostid);
   strncat(resp, tmpbuf, resplen);

   unlink(sctx->sdata->ttmpfile);
   unlink(sctx->sdata->tmpframe);

   if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_PRIORITY, "%s: removed", sctx->sdata->ttmpfile);
}


void process_command_reset(struct session_ctx *sctx, int *protocol_state, char *resp, int resplen){

   strncat(resp, SMTP_RESP_250_OK, resplen);

   if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_PRIORITY, "%s: removed", sctx->sdata->ttmpfile);

   unlink(sctx->sdata->ttmpfile);
   unlink(sctx->sdata->tmpframe);

   init_session_data(sctx->sdata, sctx->cfg);

   *protocol_state = SMTP_STATE_HELO;
}


void send_buffered_response(struct session_ctx *sctx, int starttls, char *resp){
   int rc;
   char ssl_error[SMALLBUFSIZE];

   write1(sctx->new_sd, resp, strlen(resp), sctx->sdata->tls, sctx->data->ssl);

   if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_PRIORITY, "%s: sent: %s", sctx->sdata->ttmpfile, resp);
   memset(resp, 0, MAXBUFSIZE);

   if(starttls == 1 && sctx->sdata->tls == 0){

      if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_PRIORITY, "%s: waiting for ssl handshake", sctx->sdata->ttmpfile);

      rc = SSL_accept(sctx->data->ssl);

      if(sctx->cfg->verbosity >= _LOG_DEBUG) syslog(LOG_PRIORITY, "%s: SSL_accept() finished", sctx->sdata->ttmpfile);

      if(rc == 1){
         sctx->sdata->tls = 1;
      }
      else {
         ERR_error_string_n(ERR_get_error(), ssl_error, SMALLBUFSIZE);
         syslog(LOG_PRIORITY, "%s: SSL_accept() failed, rc=%d, errorcode: %d, error text: %s\n", sctx->sdata->ttmpfile, rc, SSL_get_error(sctx->data->ssl, rc), ssl_error);
      }
   }
}