--- src/client.c	2004-01-21 04:35:13.000000000 -0500
+++ src/client.c	2004-01-21 04:37:19.000000000 -0500
@@ -202,3 +202,5 @@ static int init_remote(CLI *c) {
     /* Setup c->remote_fd, now */
-    if(c->opt->option.remote) {
+    if(c->opt->option.fdforward) {
+	fd=c->opt->use_fd;
+    } else if(c->opt->option.remote) {
         c->resolved_addresses=NULL;
--- src/options.c	2004-01-21 04:35:13.000000000 -0500
+++ src/options.c	2004-01-21 04:35:30.000000000 -0500
@@ -618,2 +618,25 @@ static char *service_options(CMD cmd, LO
 
+    /* fdforward */
+    switch(cmd) {
+    case CMD_INIT:
+        section->option.fdforward=0;
+        section->use_fd=-1;
+        break;
+    case CMD_EXEC:
+        if(strcasecmp(opt, "fdforward"))
+            break;
+        section->option.fdforward=1;
+        if(atoi(arg)>0 || !strcmp(arg, "0"))
+            section->use_fd=atoi(arg);
+        else
+            return "Illegal fdforward value";
+        return NULL; /* OK */
+    case CMD_DEFAULT:
+        break;
+    case CMD_HELP:
+        log_raw("%-15s = an already open socket file descriptor",
+            "fdforward");
+        break;
+    }
+
     /* delay */
@@ -734,3 +757,26 @@ static char *service_options(CMD cmd, LO
             "protocol");
-        log_raw("%18scurrently supported: smtp, pop3, nntp", "");
+        log_raw("%18scurrently supported: smtp, pop3, imap, nntp", "");
+        break;
+    }
+
+    /* revertible */
+    switch(cmd) {
+    case CMD_INIT:
+        section->option.revertible=0;
+        break;
+    case CMD_EXEC:
+        if(strcasecmp(opt, "revertible"))
+            break;
+        if(!strcasecmp(arg, "yes"))
+            section->option.revertible=1;
+        else if(!strcasecmp(arg, "no"))
+            section->option.revertible=0;
+        else
+            return "argument should be either 'yes' or 'no'";
+        return NULL; /* OK */
+    case CMD_DEFAULT:
+        break;
+    case CMD_HELP:
+        log_raw("%-15s = yes|no allow starttls enabled protocols to revert back to plaintext",
+            "revertible");
         break;
@@ -989,3 +1035,4 @@ static char *section_validate(LOCAL_OPTI
             (unsigned int)section->option.program +
-            (unsigned int)section->option.remote != 2)
+            (unsigned int)section->option.remote +
+	    (unsigned int)section->option.fdforward != 2)
 #endif
--- src/protocol.c	2004-01-21 04:35:13.000000000 -0500
+++ src/protocol.c	2004-01-21 04:35:30.000000000 -0500
@@ -40,2 +40,4 @@ static int pop3_client(CLI *);
 static int pop3_server(CLI *);
+static int imap_client(CLI *);
+static int imap_server(CLI *);
 static int nntp_client(CLI *);
@@ -69,2 +71,8 @@ int negotiate(CLI *c) {
     }
+    if(!strcmp(c->opt->protocol, "imap")) {
+        if(options.option.client)
+            return imap_client(c);
+        else
+            return imap_server(c);
+    }
     if(!strcmp(c->opt->protocol, "nntp")) {
@@ -130,4 +138,114 @@ static int smtp_client(CLI *c) {
 
+#define PP_BUFSIZE 8192
+static int plaintext_proxy(CLI *c)
+{
+  fd_set rd_set, wr_set;
+  char rbuf[PP_BUFSIZE];
+  int rbufend,rdone;
+  char lbuf[PP_BUFSIZE];
+  int lbufend,ldone;
+  struct timeval tv;
+  int ready;
+  int fdmax;
+  int howmuch, sofar;
+
+  fdmax = c->remote_fd.fd;
+  if (c->local_wfd.fd > fdmax)
+    fdmax = c->local_wfd.fd;
+  if (c->local_rfd.fd > fdmax)
+    fdmax = c->local_rfd.fd;
+  fdmax++;
+  
+  lbufend = rbufend = 0;
+  rdone = ldone = 0;
+
+  tv.tv_sec = 86400;
+  tv.tv_usec = 0;
+  while( !( (rdone || ldone) && (!rbufend && !lbufend) ) ) {
+    log(LOG_DEBUG,"rdone=%d, ldone=%d, rbufend=%d, lbufend=%d",rdone,ldone,rbufend,lbufend);
+    FD_ZERO(&rd_set);
+    FD_ZERO(&wr_set);
+    if (rbufend)
+      FD_SET((c->local_wfd.fd),&wr_set);
+    else if (!rdone)
+      FD_SET(c->remote_fd.fd,&rd_set);
+    
+    if (lbufend)
+      FD_SET(c->remote_fd.fd,&wr_set);
+    else if (!ldone)
+      FD_SET(c->local_rfd.fd,&rd_set);
+    
+    do { /* Skip "Interrupted system call" errors */
+      ready=select(fdmax, &rd_set, &wr_set, NULL, &tv);
+    } while(ready<0 && get_last_socket_error()==EINTR);
+    
+    if(ready<0) { /* Break the connection for others */
+      sockerror("select");
+      return 1;
+    }
+    if(!ready) { /* Timeout */
+      log(LOG_DEBUG, "select timeout - connection reset");
+      return 1;
+    }
+    
+    if (lbufend > 0) {
+      if (FD_ISSET(c->remote_fd.fd,&wr_set))
+	{
+	  sofar = 0;
+	  while (sofar < lbufend) {
+	    if ((howmuch=write(c->remote_fd.fd,lbuf+sofar,lbufend-sofar)) < 0) {
+	      sockerror("write");
+	      return 1;
+	    }
+	    sofar += howmuch;
+	  }
+	  lbufend = 0;
+	}
+    } else {
+      if (FD_ISSET(c->local_rfd.fd,&rd_set)) {
+	if ( (lbufend = read(c->local_rfd.fd,lbuf,PP_BUFSIZE)) < 0) {
+	  sockerror("read");
+	  return 1;
+	}
+	if (lbufend == 0) /* EOF */
+        {
+	  log(LOG_DEBUG,"EOF reading from local");
+	  ldone=1;
+	}
+      }
+    }
+
+    if (rbufend > 0) {
+      if (FD_ISSET(c->local_wfd.fd, &wr_set)) {
+	sofar = 0;
+	while (sofar < rbufend) {
+	  if ( (howmuch = write(c->local_wfd.fd, rbuf + sofar, rbufend - sofar)) < 0) {
+	    sockerror("write");
+	    return 1;
+	  }
+	  sofar += howmuch;
+	}
+	rbufend = 0;
+      }
+    } else {
+      if (FD_ISSET(c->remote_fd.fd,&rd_set)) {
+	if ( (rbufend = read(c->remote_fd.fd,rbuf,PP_BUFSIZE)) < 0) {
+	  sockerror("read");
+	  return 1;
+	}
+	if (rbufend == 0) /* EOF */ {
+	  log(LOG_DEBUG,"EOF reading from remote");
+	  rdone=1;
+	}
+      }
+    }
+  }
+
+  log(LOG_DEBUG, "plaintext_proxy finished normally.");
+  return 0;
+}
+
 static int smtp_server(CLI *c) {
     char line[STRLEN];
+    int read_ret;
 
@@ -136,3 +254,3 @@ static int smtp_server(CLI *c) {
 
-    if(fdscanf(c, c->remote_fd.fd, "220%[^\n]", line)!=1) {
+    if(fdscanf(c, c->remote_fd.fd, "220%[^\r\n]", line)!=1) {
         log(LOG_ERR, "Unknown server welcome");
@@ -142,13 +260,48 @@ static int smtp_server(CLI *c) {
         return -1;
-    if(fdscanf(c, c->local_rfd.fd, "EHLO %[^\n]", line)!=1) {
-        log(LOG_ERR, "Unknown client EHLO");
-        return -1;
+    
+    /* See if we get an EHLO command */
+    if (((read_ret=fdgets(c, c->local_rfd.fd, line)) >= 0) &&
+	(strlen(line) >= 4) &&
+	(!line[4] || isspace(line[4])) &&
+	 (strncasecmp(line,"ehlo",4) == 0) ) {
+      if (fdputs(c,c->remote_fd.fd,line) < 0)
+	return -1;
+      while ( (fdgets(c,c->remote_fd.fd, line) >= 0) 
+	      && (line[3] == '-') ) {
+	if (fdputs(c,c->local_wfd.fd,line) < 0)
+	  return -1;
+      }
+      line[3] = '-';
+      if (fdputs(c,c->local_wfd.fd,line) < 0)
+	return -1;
+      if (fdputs(c,c->local_wfd.fd,"250 STARTTLS") < 0)
+	return -1;
+      
+      /* See if we get a STARTTLS command */
+      if (((read_ret=fdgets(c,c->local_rfd.fd, line)) >= 0) &&
+	  (strlen(line) >= 8) &&
+	  (!line[8] || isspace(line[8])) &&
+	  (strncasecmp(line,"starttls",8) == 0) ) {
+	if (!line[8]) {
+	  /* Technically, we should shut down the SMTP connection and get
+	   * a new one, but screw it for now. */
+	  if(fdputs(c,c->local_wfd.fd, "220 Go ahead") >= 0)
+	    return 0;
+	} else {
+	  fdputs(c,c->local_wfd.fd,"501 Syntax error (no parameters allowed; STARTTLS disabled) (#5.5.4)");
+	  return -1;
+	} 
+	
+      }
     }
-    if(fdprintf(c, c->local_wfd.fd, "250-%s Welcome", line)<0)
-        return -1;
-    if(fdprintf(c, c->local_wfd.fd, "250 STARTTLS")<0)
-        return -1;
-    if(fdscanf(c, c->local_rfd.fd, "STARTTLS", line)<0) {
-        log(LOG_ERR, "STARTTLS expected");
-        return -1;
+    if (read_ret < 0)
+      return -1;
+    if (c->opt->option.revertible) {
+      if (fdputs(c,c->remote_fd.fd,line) < 0)
+	return -1;
+      exit(plaintext_proxy(c));
+    }
+    else {
+      fdputs(c,c->local_wfd.fd,"421 Encryption required; must use STARTTLS");
+      return -1;
     }
@@ -184,22 +337,145 @@ static int pop3_server(CLI *c) {
 
-    if(fdscanf(c, c->remote_fd.fd, "%[^\n]", line)<0)
+    if(fdscanf(c, c->remote_fd.fd, "%[^\r\n]", line)<0)
         return -1;
+
     if(fdprintf(c, c->local_wfd.fd, "%s + stunnel", line)<0)
         return -1;
-    if(fdscanf(c, c->local_rfd.fd, "%[^\n]", line)<0)
+
+    while(1) {
+	if(fdgets(c,c->local_rfd.fd, line)<0)
+	    return -1;
+	if(strncasecmp(line, "CAPA", 4) == 0) { /* Client wants RFC 2449 extensions */
+	    fdputs(c,c->remote_fd.fd,line);
+	    if (fdgets(c,c->remote_fd.fd,line) < 0)
+		return -1;
+	    if (line[0] == '+') {
+		if (fdputs(c,c->local_wfd.fd,line) < 0)
+		    return -1;
+		while ( (fdgets(c,c->remote_fd.fd,line) >= 0)
+			&& ( (strlen(line) > 1) || (line[0] != '.') ) ) {
+		    if (fdputs(c,c->local_wfd.fd,line) < 0)
+			return -1;
+		}
+	    } else {
+		if (fdputs(c,c->local_wfd.fd,"+OK Stunnel capability list follows") < 0)
+		    return -1;
+	    }
+	    if (fdputs(c,c->local_wfd.fd,"STLS") < 0)
+		return -1;
+	    if (fdputs(c,c->local_wfd.fd,".") < 0)
+		return -1;
+	} else if (strncasecmp(line, "STLS", 4) == 0) {
+	    if(fdputs(c,c->local_wfd.fd, "+OK stunnel starting TLS negotiation")<0)
+		return -1;
+	    return 0;
+	}
+	else {
+	    if (fdputs(c,c->remote_fd.fd,line) < 0)
+		return -1;
+	    if (c->opt->option.revertible)
+		exit(plaintext_proxy(c));
+	    else {
+		fdputs(c,c->local_wfd.fd,"-Encryption required; must use STLS");
+		    return -1;
+	    }
+	}
+    }
+    return -1;
+}
+
+static int imap_client(CLI *c) {
+    char line[STRLEN];
+
+    if(fdgets(c,c->remote_fd.fd, line)<0)
         return -1;
-    if(!strncmp(line, "CAPA", 4)) { /* Client wants RFC 2449 extensions */
-        if(fdprintf(c, c->local_wfd.fd, "-ERR Stunnel does not support capabilities")<0)
-            return -1;
-        if(fdscanf(c, c->local_rfd.fd, "%[^\n]", line)<0)
-            return -1;
+    if(strncasecmp(line,"* OK ",4)) {
+        log(LOG_ERR, "Unknown server welcome");
     }
-    if(strncmp(line, "STLS", 4)) {
-        log(LOG_ERR, "Client does not want TLS");
+    if(fdputs(c,c->local_wfd.fd, line)<0)
+    if(fdprintf(c,c->remote_fd.fd, "a STARTTLS")<0)
+        return -1;
+    if(fdgets(c,c->remote_fd.fd, line)<0)
+        return -1;
+    if(strncasecmp(line,"a OK ",5)) {
+        log(LOG_ERR, "Server does not support TLS");
         return -1;
     }
-    if(fdprintf(c, c->local_wfd.fd, "+OK Stunnel starts TLS negotiation")<0)
+    return 0;
+}
+
+static int imap_server(CLI *c) {
+    char line[STRLEN];
+    char procline[STRLEN];
+    char *tag, *cmd;
+    int do_if_fail = 0;
+
+    if (fdgets(c,c->remote_fd.fd,line) < 0)
+      return -1;
+
+    if(fdprintf(c,c->local_wfd.fd, "%s + stunnel", line)<0)
         return -1;
 
-    return 0;
+    while(1) {
+      if(fdgets(c,c->local_rfd.fd, line)<0)
+        return -1;
+      safecopy(procline, line);
+      tag = procline;
+      if (!(cmd=strchr(procline,' '))) {
+	do_if_fail = 1;
+	break;
+      }
+      *cmd='\0';
+      cmd++;
+      if(strncasecmp(cmd, "CAPABILITY", 11) == 0) {
+	fdputs(c,c->remote_fd.fd,line);
+	if (fdgets(c,c->remote_fd.fd,line) < 0)
+	  return -1;
+	if (strncasecmp(line,"* CAPABILITY",12) == 0) {
+	  safeconcat(line," STARTTLS");
+	  fdputs(c,c->local_wfd.fd,line);
+	} else {
+	  do_if_fail = 2;
+	  break;
+	}
+	if (fdgets(c,c->remote_fd.fd,line) < 0)
+	  return -1;
+	if ( (strncasecmp(line,tag,strlen(tag)) != 0) ||
+	     (line[strlen(tag)] != ' ') ||
+	     (strncasecmp(line+strlen(tag)+1,"OK",2) != 0) )
+	  {
+	    do_if_fail = 2;
+	    break;
+	  }
+	if (fdputs(c,c->local_wfd.fd,line) < 0)
+	  return -1;
+      }
+      else if (strncasecmp(cmd, "STARTTLS", 8) == 0) {
+	if (fdwrite(c,c->local_wfd.fd,tag,strlen(tag)) < 0)
+	  return -1;
+	if (fdwrite(c,c->local_wfd.fd," ",1) < 0)
+	  return -1;
+	if (fdputs(c,c->local_wfd.fd,"OK Begin TLS negotiation now") < 0)
+	  return -1;
+
+	return 0;
+      } else {
+	do_if_fail = 1;
+	break;
+      }
+    }
+    
+    if (c->opt->option.revertible) {
+      if (do_if_fail == 1) {
+	if (fdputs(c,c->remote_fd.fd,line) < 0)
+	  return -1;
+      } else if (do_if_fail == 2) {
+	if (fdputs(c,c->local_wfd.fd,line) < 0)
+	  return -1;
+      }
+      exit(plaintext_proxy(c));
+    }
+    else {
+      fdputs(c,c->local_wfd.fd,"-Encryption required; must use STLS");
+      return -1;
+    }
 }
--- src/prototypes.h	2004-01-21 04:35:13.000000000 -0500
+++ src/prototypes.h	2004-01-21 04:35:30.000000000 -0500
@@ -159,2 +159,3 @@ typedef struct local_options {
     char *remote_address;
+    int use_fd;
     int timeout_busy; /* Maximum waiting for data time */
@@ -171,2 +172,4 @@ typedef struct local_options {
         unsigned int remote:1;
+        unsigned int fdforward:1;
+	unsigned int revertible:1;
 #ifndef USE_WIN32
@@ -215,2 +218,3 @@ typedef struct {
     LOCAL_OPTIONS *opt;
+    int allow_downgrade;
     char accepting_address[16], connecting_address[16]; /* Dotted-decimal */
@@ -272,2 +276,5 @@ int fdscanf(CLI *, int, const char *, ch
 #endif
+int fdwrite(CLI *, int, char *, int);
+int fdgets(CLI *, int, char *);
+int fdputs(CLI *, int, char *);
 
--- src/sselect.c	2004-01-21 04:35:13.000000000 -0500
+++ src/sselect.c	2004-01-21 04:35:30.000000000 -0500
@@ -183,7 +183,34 @@ void exec_status(void) { /* dead local (
 
+int fdwrite(CLI *c, int fd, char *buffer, int len) {
+    char logline[STRLEN];
+    int ptr, written, towrite;
+
+    for(ptr=0, towrite=len; towrite>0; ptr+=written, towrite-=written) {
+        if(waitforsocket(fd, 1 /* write */, c->opt->timeout_busy)<1)
+            return -1;
+        written=writesocket(fd, buffer+ptr, towrite);
+        if(written<0) {
+            sockerror("writesocket (fdwrite)");
+            return -1;
+        }
+    }
+    safecopy(logline, buffer);
+    safestring(logline);
+    log(LOG_DEBUG, " -> %s", logline);
+    return 0;
+}
+
+int fdputs(CLI *c, int fd, char *line) {
+  char crlf[]="\r\n";
+
+  if (fdwrite(c, fd, line, strlen(line)) < 0)
+    return -1;
+  return fdwrite(c,fd,crlf,strlen(crlf));
+}
+
 int fdprintf(CLI *c, int fd, const char *format, ...) {
     va_list arglist;
-    char line[STRLEN], logline[STRLEN];
+    char line[STRLEN];
     char crlf[]="\r\n";
-    int len, ptr, written, towrite;
+    int len;
 
@@ -198,44 +225,46 @@ int fdprintf(CLI *c, int fd, const char 
     len+=2;
-    for(ptr=0, towrite=len; towrite>0; ptr+=written, towrite-=written) {
-        if(waitforsocket(fd, 1 /* write */, c->opt->timeout_busy)<1)
-            return -1;
-        written=writesocket(fd, line+ptr, towrite);
-        if(written<0) {
-            sockerror("writesocket (fdprintf)");
-            return -1;
-        }
-    }
-    safecopy(logline, line);
-    safestring(logline);
-    log(LOG_DEBUG, " -> %s", logline);
-    return len;
+
+    if (fdwrite(c,fd,line,len)<0)
+	return -1;
+    else
+	return len;
 }
 
-int fdscanf(CLI *c, int fd, const char *format, char *buffer) {
-    char line[STRLEN], logline[STRLEN];
+int fdgets(CLI *c, int fd, char *buffer) {
+    char logline[STRLEN];
     int ptr;
 
-    for(ptr=0; ptr<STRLEN-1; ptr++) {
+    for(ptr=0; ptr<STRLEN-1;) {
         if(waitforsocket(fd, 0 /* read */, c->opt->timeout_busy)<1)
             return -1;
-        switch(readsocket(fd, line+ptr, 1)) {
+        switch(readsocket(fd, buffer+ptr, 1)) {
         case -1: /* error */
-            sockerror("readsocket (fdscanf)");
+            sockerror("readsocket (fdgets)");
             return -1;
         case 0: /* EOF */
-            log(LOG_ERR, "Unexpected socket close (fdscanf)");
+            log(LOG_ERR, "Unexpected socket close (fdgets)");
             return -1;
         }
-        if(line[ptr]=='\r')
+        if(buffer[ptr]=='\r')
             continue;
-        if(line[ptr]=='\n')
+        if(buffer[ptr]=='\n')
             break;
+	ptr++;
     }
-    line[ptr]='\0';
-    safecopy(logline, line);
+    buffer[ptr]='\0';
+    safecopy(logline, buffer);
     safestring(logline);
     log(LOG_DEBUG, " <- %s", logline);
-    return sscanf(line, format, buffer);
+    return 0;
 }
 
+int fdscanf(CLI *c, int fd, const char *format, char *buffer) {
+    char line[STRLEN];
+
+    if (fdgets(c, fd, line) < 0)
+	return -1;
+
+    return sscanf(line, format, buffer);
+}
+ 
 /* End of select.c */