+/*************************************************
+* 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 */
git://git.exim.org / exim.git / commitdiff