Experimental_XCLIENT. Bug 2702

14 files changed, 415 insertions, 25 deletions

diff --git a/src/OS/Makefile-Base b/src/OS/Makefile-Base
index d00ab9404..71aee4d93 100644
--- a/src/OS/Makefile-Base
+++ b/src/OS/Makefile-Base
@@ -497,7 +497,8 @@ OBJ_EXPERIMENTAL =	arc.o \
 			dmarc.o \
 			imap_utf7.o \
 			spf.o \
-			utf8.o
+			utf8.o \
+			xclient.o
 
 # Targets for final binaries; the main one has a build number which is
 # updated each time. We don't bother with that for the auxiliaries.
@@ -873,6 +874,7 @@ dmarc.o:	$(HDRS) pdkim/pdkim.h dmarc.h dmarc.c
 imap_utf7.o:	$(HDRS) imap_utf7.c
 spf.o:		$(HDRS) spf.h spf.c
 utf8.o:		$(HDRS) utf8.c
+xclient.o:	$(HDRS) xclient.c
 
 # The module containing tables of available lookups, routers, auths, and
 # transports must be rebuilt if any of them are. However, because the makefiles
diff --git a/src/scripts/MakeLinks b/src/scripts/MakeLinks
index af6138063..0694af4c0 100755
--- a/src/scripts/MakeLinks
+++ b/src/scripts/MakeLinks
@@ -125,7 +125,7 @@ done
 
 # EXPERIMENTAL_*
 for f in  arc.c bmi_spam.c bmi_spam.h dcc.c dcc.h dane.c dane-openssl.c \
-  danessl.h imap_utf7.c spf.c spf.h srs.c srs.h utf8.c
+  danessl.h imap_utf7.c spf.c spf.h srs.c srs.h utf8.c xclient.c
 do
   ln -s ../src/$f $f
 done
diff --git a/src/src/auths/xtextdecode.c b/src/src/auths/xtextdecode.c
index b6a927194..edd2282d0 100644
--- a/src/src/auths/xtextdecode.c
+++ b/src/src/auths/xtextdecode.c
@@ -32,9 +32,9 @@ Returns:      the number of bytes in the result, excluding the final zero;
 */
 
 int
-auth_xtextdecode(uschar *code, uschar **ptr)
+auth_xtextdecode(uschar * code, uschar ** ptr)
 {
-register int x;
+int x;
 uschar * result = store_get(Ustrlen(code) + 1, code);
 *ptr = result;
 
diff --git a/src/src/config.h.defaults b/src/src/config.h.defaults
index 221705224..fb5fe3603 100644
--- a/src/src/config.h.defaults
+++ b/src/src/config.h.defaults
@@ -211,6 +211,7 @@ Do not put spaces between # and the 'define'.
 #define EXPERIMENTAL_DSN_INFO
 #define EXPERIMENTAL_ESMTP_LIMITS
 #define EXPERIMENTAL_QUEUEFILE
+#define EXPERIMENTAL_XCLIENT
 
 
 /* For developers */
diff --git a/src/src/exim.c b/src/src/exim.c
index c16beb1af..06863347d 100644
--- a/src/src/exim.c
+++ b/src/src/exim.c
@@ -1132,6 +1132,9 @@ g = string_cat(g, US"Support for:");
 #ifdef EXPERIMENTAL_QUEUEFILE
   g = string_cat(g, US" Experimental_QUEUEFILE");
 #endif
+#ifdef EXPERIMENTAL_XCLIENT
+  g = string_cat(g, US" Experimental_XCLIENT");
+#endif
 g = string_cat(g, US"\n");
 
 g = string_cat(g, US"Lookups (built-in):");
diff --git a/src/src/functions.h b/src/src/functions.h
index 76392f304..aa5057a83 100644
--- a/src/src/functions.h
+++ b/src/src/functions.h
@@ -686,6 +686,11 @@ extern BOOL    write_chunk(transport_ctx *, uschar *, int);
 extern ssize_t write_to_fd_buf(int, const uschar *, size_t);
 extern uschar *wrap_header(const uschar *, unsigned, unsigned, const uschar *, unsigned);
 
+#ifdef EXPERIMENTAL_XCLIENT
+extern uschar * xclient_smtp_command(uschar *, int *, BOOL *);
+extern gstring * xclient_smtp_advertise_str(gstring *);
+#endif
+
 
 /******************************************************************************/
 /* Predicate: if an address is in a tainted pool.
diff --git a/src/src/globals.c b/src/src/globals.c
index 539bae00e..9f4053937 100644
--- a/src/src/globals.c
+++ b/src/src/globals.c
@@ -995,11 +995,18 @@ uschar *host_lookup_msg        = US"";
 int     host_number            = 0;
 uschar *host_number_string     = NULL;
 uschar *host_reject_connection = NULL;
-tree_node *hostlist_anchor     = NULL;
-int     hostlist_count         = 0;
+uschar *hosts_connection_nolog = NULL;
+#ifdef SUPPORT_PROXY
+uschar *hosts_proxy            = NULL;
+#endif
 uschar *hosts_treat_as_local   = NULL;
 uschar *hosts_require_helo     = US"*";
-uschar *hosts_connection_nolog = NULL;
+#ifdef EXPERIMENTAL_XCLIENT
+uschar *hosts_xclient	       = NULL;
+#endif
+tree_node *hostlist_anchor     = NULL;
+int     hostlist_count         = 0;
+
 
 int     ignore_bounce_errors_after = 10*7*24*60*60;  /* 10 weeks */
 uschar *ignore_fromline_hosts  = NULL;
@@ -1232,8 +1239,7 @@ int     process_info_len       = 0;
 uschar *process_log_path       = NULL;
 const uschar *process_purpose  = US"fresh-exec";
 
-#if defined(SUPPORT_PROXY) || defined(SUPPORT_SOCKS)
-uschar *hosts_proxy            = NULL;
+#if defined(SUPPORT_PROXY) || defined(SUPPORT_SOCKS) || defined(EXPERIMENTAL_XCLIENT)
 uschar *proxy_external_address = NULL;
 int     proxy_external_port    = 0;
 uschar *proxy_local_address    = NULL;
@@ -1660,5 +1666,4 @@ int     warning_count          = 0;
 const uschar *warnmsg_delay    = NULL;
 const uschar *warnmsg_recipients = NULL;
 
-
 /*  End of globals.c */
diff --git a/src/src/globals.h b/src/src/globals.h
index e216b9208..3a5513382 100644
--- a/src/src/globals.h
+++ b/src/src/globals.h
@@ -661,12 +661,16 @@ extern uschar *host_lookup_order;      /* Order of host lookup types */
 extern uschar *host_lookup_msg;        /* Text for why it failed */
 extern int     host_number;            /* For sharing spools */
 extern uschar *host_number_string;     /* For expanding */
-extern uschar *hosts_require_helo;     /* check for HELO/EHLO before MAIL */
 extern uschar *host_reject_connection; /* Reject these hosts */
-extern tree_node *hostlist_anchor;     /* Tree of defined host lists */
-extern int     hostlist_count;         /* Number defined */
 extern uschar *hosts_connection_nolog; /* Limits the logging option */
+extern uschar *hosts_require_helo;     /* check for HELO/EHLO before MAIL */
 extern uschar *hosts_treat_as_local;   /* For routing */
+#ifdef EXPERIMENTAL_XCLIENT
+extern uschar *hosts_xclient;	       /* Allow XCLIENT command for specified hosts */
+#endif
+extern tree_node *hostlist_anchor;     /* Tree of defined host lists */
+extern int     hostlist_count;         /* Number defined */
+
 
 extern int     ignore_bounce_errors_after; /* Keep them for this time. */
 extern BOOL    ignore_fromline_local;  /* Local SMTP ignore fromline */
@@ -828,7 +832,8 @@ extern int     proxy_external_port;    /* Port on remote interface of proxy */
 extern uschar *proxy_local_address;    /* IP of local interface of proxy */
 extern int     proxy_local_port;       /* Port on local interface of proxy */
 extern int     proxy_protocol_timeout; /* Timeout for proxy negotiation */
-extern BOOL    proxy_session;          /* TRUE if receiving mail from valid proxy  */
+extern BOOL    proxy_session;          /* TRUE if receiving mail from valid proxy
+					  or sending via one */
 #endif
 
 extern uschar *prvscheck_address;      /* Set during prvscheck expansion item */
diff --git a/src/src/host.c b/src/src/host.c
index 8d53eb3de..136ee8953 100644
--- a/src/src/host.c
+++ b/src/src/host.c
@@ -824,9 +824,9 @@ Returns:     pointer to character string
 */
 
 uschar *
-host_ntoa(int type, const void *arg, uschar *buffer, int *portptr)
+host_ntoa(int type, const void * arg, uschar * buffer, int * portptr)
 {
-uschar *yield;
+uschar * yield;
 
 /* The new world. It is annoying that we have to fish out the address from
 different places in the block, depending on what kind of address it is. It
diff --git a/src/src/macro_predef.c b/src/src/macro_predef.c
index 0053cb245..8fade68ca 100644
--- a/src/src/macro_predef.c
+++ b/src/src/macro_predef.c
@@ -205,6 +205,9 @@ due to conflicts with other common macros. */
 #ifndef DISABLE_TLS_RESUME
   builtin_macro_create(US"_HAVE_TLS_RESUME");
 #endif
+#ifdef EXPERIMENTAL_XCLIENT
+  builtin_macro_create(US"_HAVE_XCLIENT");
+#endif
 
 #ifdef LOOKUP_LSEARCH
   builtin_macro_create(US"_HAVE_LOOKUP_LSEARCH");
diff --git a/src/src/macros.h b/src/src/macros.h
index 36ed185ed..c55276332 100644
--- a/src/src/macros.h
+++ b/src/src/macros.h
@@ -822,7 +822,11 @@ most recent SMTP commands. SCH_NONE is "empty". */
 enum { SCH_NONE, SCH_AUTH, SCH_DATA, SCH_BDAT,
        SCH_EHLO, SCH_ETRN, SCH_EXPN, SCH_HELO,
        SCH_HELP, SCH_MAIL, SCH_NOOP, SCH_QUIT, SCH_RCPT, SCH_RSET, SCH_STARTTLS,
-       SCH_VRFY };
+       SCH_VRFY,
+#ifdef EXPERIMENTAL_XCLIENT
+       SCH_XCLIENT,
+#endif
+       };
 
 /* Returns from host_find_by{name,dns}() */
 
diff --git a/src/src/readconf.c b/src/src/readconf.c
index 3b26e87d5..7d48f085d 100644
--- a/src/src/readconf.c
+++ b/src/src/readconf.c
@@ -187,6 +187,9 @@ static optionlist optionlist_config[] = {
 #endif
   { "hosts_require_helo",       opt_stringptr,   {&hosts_require_helo} },
   { "hosts_treat_as_local",     opt_stringptr,   {&hosts_treat_as_local} },
+#ifdef EXPERIMENTAL_XCLIENT
+  { "hosts_xclient",		opt_stringptr,	 {&hosts_xclient} },
+#endif
 #ifdef LOOKUP_IBASE
   { "ibase_servers",            opt_stringptr,   {&ibase_servers} },
 #endif
@@ -399,7 +402,7 @@ static optionlist optionlist_config[] = {
   { "uucp_from_pattern",        opt_stringptr,   {&uucp_from_pattern} },
   { "uucp_from_sender",         opt_stringptr,   {&uucp_from_sender} },
   { "warn_message_file",        opt_stringptr,   {&warn_message_file} },
-  { "write_rejectlog",          opt_bool,        {&write_rejectlog} }
+  { "write_rejectlog",          opt_bool,        {&write_rejectlog} },
 };
 
 #ifndef MACRO_PREDEF
diff --git a/src/src/smtp_in.c b/src/src/smtp_in.c
index 7a45772ce..6f4ad9495 100644
--- a/src/src/smtp_in.c
+++ b/src/src/smtp_in.c
@@ -75,6 +75,9 @@ enum {
   ETRN_CMD,                     /* This by analogy with TURN from the RFC */
   STARTTLS_CMD,                 /* Required by the STARTTLS RFC */
   TLS_AUTH_CMD,			/* auto-command at start of SSL */
+#ifdef EXPERIMENTAL_XCLIENT
+  XCLIENT_CMD,			/* per xlexkiro implementation */
+#endif
 
   /* This is a dummy to identify the non-sync commands when pipelining */
 
@@ -189,14 +192,22 @@ count of non-mail commands and possibly provoke an error.
 tls_auth is a pseudo-command, never expected in input.  It is activated
 on TLS startup and looks for a tls authenticator. */
 
-enum {	CL_RSET, CL_HELO, CL_EHLO, CL_AUTH,
+enum {
+	CL_RSET = 0,
+	CL_HELO,
+	CL_EHLO,
+	CL_AUTH,
 #ifndef DISABLE_TLS
-	CL_STLS, CL_TLAU,
+	CL_STLS,
+	CL_TLAU,
+#endif
+#ifdef EXPERIMENTAL_XCLIENT
+	CL_XCLI,
 #endif
 };
 
 static smtp_cmd_list cmd_list[] = {
-  /* name         len                     cmd     has_arg is_mail_cmd */
+  /*             name         len                     cmd     has_arg is_mail_cmd */
 
   [CL_RSET] = { "rset",       sizeof("rset")-1,       RSET_CMD,	FALSE, FALSE },  /* First */
   [CL_HELO] = { "helo",       sizeof("helo")-1,       HELO_CMD, TRUE,  FALSE },
@@ -206,8 +217,9 @@ static smtp_cmd_list cmd_list[] = {
   [CL_STLS] = { "starttls",   sizeof("starttls")-1,   STARTTLS_CMD, FALSE, FALSE },
   [CL_TLAU] = { "tls_auth",   0,                      TLS_AUTH_CMD, FALSE, FALSE },
 #endif
-
-/* If you change anything above here, also fix the definitions below. */
+#ifdef EXPERIMENTAL_XCLIENT
+  [CL_XCLI] = { "xclient",    sizeof("xclient")-1,    XCLIENT_CMD, TRUE,  FALSE },
+#endif
 
   { "mail from:", sizeof("mail from:")-1, MAIL_CMD, TRUE,  TRUE  },
   { "rcpt to:",   sizeof("rcpt to:")-1,   RCPT_CMD, TRUE,  TRUE  },
@@ -241,6 +253,9 @@ uschar * smtp_names[] =
   [SCH_RSET] = US"RSET",
   [SCH_STARTTLS] = US"STARTTLS",
   [SCH_VRFY] = US"VRFY",
+#ifdef EXPERIMENTAL_XCLIENT
+  [SCH_XCLIENT] = US"XCLIENT",
+#endif
   };
 
 static uschar *protocols_local[] = {
@@ -1260,6 +1275,7 @@ return OTHER_CMD;
 
 
 
+
 /*************************************************
 *          Forced closedown of call              *
 *************************************************/
@@ -1774,7 +1790,6 @@ while (done <= 0)
       bsmtp_transaction_linecount = receive_linecount;
       break;
 
-
     /* The MAIL FROM command requires an address as an operand. All we
     do here is to parse it for syntactic correctness. The form "<>" is
     a special case which converts into an empty string. The start/end
@@ -4178,7 +4193,13 @@ while (done <= 0)
 	  fl.tls_advertised = TRUE;
 	  }
 #endif
-
+#ifdef EXPERIMENTAL_XCLIENT
+	if (proxy_session || verify_check_host(&hosts_xclient) != FAIL)
+	  {
+	  g = string_catn(g, smtp_code, 3);
+	  g = xclient_smtp_advertise_str(g);
+	  }
+#endif
 #ifndef DISABLE_PRDR
 	/* Per Recipient Data Response, draft by Eric A. Hall extending RFC */
 	if (prdr_enable)
@@ -4244,6 +4265,41 @@ while (done <= 0)
       toomany = FALSE;
       break;   /* HELO/EHLO */
 
+#ifdef EXPERIMENTAL_XCLIENT
+    case XCLIENT_CMD:
+      {
+      BOOL fatal = fl.helo_seen;
+      uschar * errmsg;
+      int resp;
+
+      HAD(SCH_XCLIENT);
+      smtp_mailcmd_count++;
+
+      if ((errmsg = xclient_smtp_command(smtp_cmd_data, &resp, &fatal)))
+	if (fatal)
+	  done = synprot_error(L_smtp_syntax_error, resp, NULL, errmsg);
+	else
+	  {
+	  smtp_printf("%d %s\r\n", FALSE, resp, errmsg);
+	  log_write(0, LOG_MAIN|LOG_REJECT, "rejected XCLIENT from %s: %s",
+	    host_and_ident(FALSE), errmsg);
+	  }
+      else
+	{
+	fl.helo_seen = FALSE;			/* Require another EHLO */
+	smtp_code = string_sprintf("%d", resp);
+
+	/*XXX unclear in spec. if this needs to be an ESMTP banner,
+	nor whether we get the original client's HELO after (or a proxy fake).
+	We require that we do; the following HELO/EHLO handling will set
+	sender_helo_name as normal. */
+
+	smtp_printf("%s XCLIENT success\r\n", FALSE, smtp_code);
+	}
+      break; /* XCLIENT */
+      }
+#endif
+
 
     /* The MAIL command requires an address as an operand. All we do
     here is to parse it for syntactic correctness. The form "<>" is
@@ -5353,6 +5409,10 @@ while (done <= 0)
       if (acl_smtp_etrn) smtp_printf(" ETRN", TRUE);
       if (acl_smtp_expn) smtp_printf(" EXPN", TRUE);
       if (acl_smtp_vrfy) smtp_printf(" VRFY", TRUE);
+#ifdef EXPERIMENTAL_XCLIENT
+      if (proxy_session || verify_check_host(&hosts_xclient) != FAIL)
+	smtp_printf(" XCLIENT", TRUE);
+#endif
       smtp_printf("\r\n", FALSE);
       break;
 
diff --git a/src/src/xclient.c b/src/src/xclient.c
new file mode 100644
index 000000000..2a8be9b0e
--- /dev/null
+++ b/src/src/xclient.c
@@ -0,0 +1,299 @@
+/*************************************************
+*     Exim - an Internet mail transport agent    *
+*************************************************/
+
+/* Copyright (c) The Exim Maintainers 2023 */
+/* See the file NOTICE for conditions of use and distribution. */
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "exim.h"
+
+#ifdef EXPERIMENTAL_XCLIENT
+
+/* From https://www.postfix.org/XCLIENT_README.html I infer two generations of
+protocol.  The more recent one obviates the utility of the HELO attribute, since
+it mandates the proxy always sending a HELO/EHLO smtp command following (a
+successful) XCLIENT command, and that will carry a NELO name (which we assume,
+though it isn't specified, will be the actual one presented to the proxy by the
+possibly-new client).  The same applies to the PROTO attribute. */
+
+# define XCLIENT_V2
+
+enum xclient_cmd_e {
+  XCLIENT_CMD_UNKNOWN,
+  XCLIENT_CMD_ADDR,
+  XCLIENT_CMD_NAME,
+  XCLIENT_CMD_PORT,
+  XCLIENT_CMD_LOGIN,
+  XCLIENT_CMD_DESTADDR,
+  XCLIENT_CMD_DESTPORT,
+# ifdef XCLIENT_V1
+  XCLIENT_CMD_HELO,
+  XCLIENT_CMD_PROTO,
+# endif
+};
+
+struct xclient_cmd {
+  const uschar *	str;
+  unsigned		len;
+} xclient_cmds[] = {
+  [XCLIENT_CMD_UNKNOWN] = { NULL },
+  [XCLIENT_CMD_ADDR] =	{ US"ADDR",  4 },
+  [XCLIENT_CMD_NAME] =	{ US"NAME",  4 },
+  [XCLIENT_CMD_PORT] =	{ US"PORT",  4 },
+  [XCLIENT_CMD_LOGIN] =	{ US"LOGIN", 5 },
+  [XCLIENT_CMD_DESTADDR] =	{ US"DESTADDR", 8 },
+  [XCLIENT_CMD_DESTPORT] =	{ US"DESTPORT", 8 },
+# ifdef XCLIENT_V1
+  [XCLIENT_CMD_HELO] =	{ US"HELO",  4 },
+  [XCLIENT_CMD_PROTO] =	{ US"PROTO", 5 },
+# endif
+};
+
+/*************************************************
+*          XCLIENT proxy implementation          *
+*************************************************/
+
+/* Arguments:
+  code        points to the coded string
+  end         points to the end of coded string
+  ptr         where to put the pointer to the result, which is in
+              dynamic store
+Returns:      the number of bytes in the result, excluding the final zero;
+              -1 if the input is malformed
+*/
+
+static int
+xclient_xtextdecode(uschar * code, uschar * end, uschar ** ptr)
+{
+return auth_xtextdecode(string_copyn(code, end-code), ptr);
+}
+
+/*************************************************
+*   Check XCLIENT line and set sender_address    *
+*************************************************/
+
+
+/* Check the format of a XCLIENT line.
+Arguments:
+  s       	the data portion of the line (already past any white space)
+  resp		result: smtp respose code
+  flag		input: helo seen  output: fail is fatal
+
+Return: NULL on success, or error message
+*/
+
+# define XCLIENT_UNAVAIL     US"[UNAVAILABLE]"
+# define XCLIENT_TEMPUNAVAIL US"[TEMPUNAVAIL]"
+
+uschar *
+xclient_smtp_command(uschar * s, int * resp, BOOL * flag)
+{
+uschar * word = s;
+enum {
+  XCLIENT_READ_COMMAND = 0,
+  XCLIENT_READ_VALUE,
+  XCLIENT_SKIP_SPACES
+} state = XCLIENT_SKIP_SPACES;
+enum xclient_cmd_e cmd;
+
+if (  !flag
+   && verify_check_host(&hosts_require_helo) == OK)
+  {
+  *resp = 503;
+  *flag = FALSE;
+  return US"no HELO/EHLO given";
+  }
+
+/* If already in a proxy session, do not re-check permission.
+Strictly we should avoid doing this for a Proxy-Protocol
+session to avoid mixups. */
+
+if(!proxy_session && verify_check_host(&hosts_xclient) == FAIL)
+  {
+  *resp = 550;
+  *flag = TRUE;
+  return US"XCLIENT command used when not advertised";
+  }
+
+if (sender_address)
+  {
+  *resp = 503;
+  *flag = FALSE;
+  return US"mail transaction in progress";
+  }
+
+if (!*word)
+  {
+  s = US"XCLIENT must have at least one operand";
+  goto fatal_501;
+  }
+
+for (state = XCLIENT_SKIP_SPACES; *s; )
+  switch (state)
+    {
+    case XCLIENT_READ_COMMAND:
+      {
+      int len;
+
+      word = s;
+      while (*s && *s != '=') s++;
+      len = s - word;
+      if (!*s)
+	{
+	s = string_sprintf("XCLIENT: missing value for parameter '%.*s'",
+			  len, word);
+	goto fatal_501;
+	}
+
+      DEBUG(D_transport) debug_printf(" XCLIENT: cmd %.*s\n", len, word);
+      cmd = XCLIENT_CMD_UNKNOWN;
+      for (struct xclient_cmd * x = xclient_cmds + 1;
+	   x < xclient_cmds + nelem(xclient_cmds); x++)
+	if (len == x->len && strncmpic(word, x->str, len) == 0)
+	  {
+	  cmd = x - xclient_cmds;
+	  break;
+	  }
+      if (cmd == XCLIENT_CMD_UNKNOWN)
+	{
+	s = string_sprintf("XCLIENT: unrecognised parameter '%.*s'",
+			  len, word);
+	goto fatal_501;
+	}
+      state = XCLIENT_READ_VALUE;
+      }
+      break;
+
+    case XCLIENT_READ_VALUE:
+      {
+      int old_pool = store_pool;
+      int len;
+      uschar * val;
+
+      word = ++s;			/* skip the = */
+      while (*s && !isspace(*s)) s++;
+      len = s - word;
+
+      DEBUG(D_transport) debug_printf(" XCLIENT: \tvalue %.*s\n", len, word);
+      if (len == 0)
+	{ s = US"XCLIENT: zero-length value for param"; goto fatal_501; }
+
+      if (  len == 13
+	 && (  strncmpic(word, XCLIENT_UNAVAIL, 13) == 0
+	    || strncmpic(word, XCLIENT_TEMPUNAVAIL, 13) == 0
+	 )  )
+	val = NULL;
+
+      else if ((len = xclient_xtextdecode(word, s, &val)) == -1)
+	{
+	s = string_sprintf("failed xtext decode for XCLIENT: '%.*s'", len, word);
+	goto fatal_501;
+	}
+
+      store_pool = POOL_PERM;
+      switch (cmd)
+	{
+	case XCLIENT_CMD_ADDR:
+	  proxy_local_address = sender_host_address;
+	  sender_host_address = val ? string_copyn(val, len) : NULL;
+	  break;
+	case XCLIENT_CMD_NAME:
+	  sender_host_name = val ? string_copyn(val, len) : NULL;
+	  break;
+	case XCLIENT_CMD_PORT:
+	  proxy_local_port = sender_host_port;
+	  sender_host_port = val ? Uatoi(val) : 0;
+	  break;
+	case XCLIENT_CMD_DESTADDR:
+	  proxy_external_address = val ? string_copyn(val, len) : NULL;
+	  break;
+	case XCLIENT_CMD_DESTPORT:
+	  proxy_external_port = val ? Uatoi(val) : 0;
+	  break;
+
+	case XCLIENT_CMD_LOGIN:
+	  if (val)
+	    {
+	    authenticated_id = string_copyn(val, len);
+	    sender_host_authenticated = US"xclient";
+	    authentication_failed = FALSE;
+	    }
+	  else
+	    {
+	    authenticated_id = NULL;
+	    sender_host_authenticated = NULL;
+	    }
+	  break;
+
+# ifdef XCLIENT_V1
+	case XCLIENT_CMD_HELO:
+	  sender_helo_name = val ? string_copyn(val, len) : NULL;
+	  break;
+	case XCLIENT_CMD_PROTO:
+	  if (!val)
+	    { store_pool = old_pool; s = US"missing proto for XCLIENT"; goto fatal_501; }
+	  else if (len == 4 && strncmpic(val, US"SMTP", 4) == 0)
+	    *esmtpflag = FALSE;	/* function arg */
+	  else if (len == 5 && strncmpic(val, US"ESMTP", 5) == 0)
+	    *esmtpflag = TRUE;
+	  else
+	    { store_pool = old_pool; s = US"bad proto for XCLIENT"; goto fatal_501; }
+	  break;
+# endif
+	}
+      store_pool = old_pool;
+      state = XCLIENT_SKIP_SPACES;
+      break;
+      }
+
+    case XCLIENT_SKIP_SPACES:
+      while (*s && isspace (*s)) s++;
+      state = XCLIENT_READ_COMMAND;
+      break;
+
+    default:
+      s = US"unhandled XCLIENT parameter type";
+      goto fatal_501;
+    }
+
+if (!proxy_local_address)
+  { s = US"missing ADDR for XCLIENT"; goto fatal_501; }
+if (!proxy_local_port)
+  { s = US"missing PORT for XCLIENT"; goto fatal_501; }
+if (state != XCLIENT_SKIP_SPACES)
+  { s = US"bad state parsing XCLIENT parameters"; goto fatal_501; }
+
+host_build_sender_fullhost();
+proxy_session = TRUE;
+*resp = 220;
+return NULL;
+
+fatal_501:
+  *flag = TRUE;
+  *resp = 501;
+  return s;
+}
+
+# undef XCLIENT_UNAVAIL
+# undef XCLIENT_TEMPUNAVAIL
+
+
+gstring *
+xclient_smtp_advertise_str(gstring * g)
+{
+g = string_catn(g, US"-XCLIENT ", 8);
+for (int i = 1; i < nelem(xclient_cmds); i++)
+  {
+  g = string_catn(g, US" ", 1);
+  g = string_cat(g, xclient_cmds[i].str);
+  }
+return string_catn(g, US"\r\n", 2);
+}
+
+
+#endif	/*EXPERIMENTAL_XCLIENT*/
+
+/* vi: aw ai sw=2
+*/
+/* End of xclient.c */