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      1 /*	$NetBSD: smtp_sasl_proto.c,v 1.3 2022/10/08 16:12:49 christos Exp $	*/
      2 
      3 /*++
      4 /* NAME
      5 /*	smtp_sasl_proto 3
      6 /* SUMMARY
      7 /*	Postfix SASL interface for SMTP client
      8 /* SYNOPSIS
      9 /*	#include smtp_sasl.h
     10 /*
     11 /*	void	smtp_sasl_helo_auth(state, words)
     12 /*	SMTP_STATE *state;
     13 /*	const char *words;
     14 /*
     15 /*	int	smtp_sasl_helo_login(state)
     16 /*	SMTP_STATE *state;
     17 /* DESCRIPTION
     18 /*	This module contains random chunks of code that implement
     19 /*	the SMTP protocol interface for SASL negotiation. The goal
     20 /*	is to reduce clutter in the main SMTP client source code.
     21 /*
     22 /*	smtp_sasl_helo_auth() processes the AUTH option in the
     23 /*	SMTP server's EHLO response.
     24 /*
     25 /*	smtp_sasl_helo_login() authenticates the SMTP client to the
     26 /*	SMTP server, using the authentication mechanism information
     27 /*	given by the server. The result is a Postfix delivery status
     28 /*	code in case of trouble.
     29 /*
     30 /*	Arguments:
     31 /* .IP state
     32 /*	Session context.
     33 /* .IP words
     34 /*	List of SASL authentication mechanisms (separated by blanks)
     35 /* DIAGNOSTICS
     36 /*	All errors are fatal.
     37 /* LICENSE
     38 /* .ad
     39 /* .fi
     40 /*	The Secure Mailer license must be distributed with this software.
     41 /* AUTHOR(S)
     42 /*	Original author:
     43 /*	Till Franke
     44 /*	SuSE Rhein/Main AG
     45 /*	65760 Eschborn, Germany
     46 /*
     47 /*	Adopted by:
     48 /*	Wietse Venema
     49 /*	IBM T.J. Watson Research
     50 /*	P.O. Box 704
     51 /*	Yorktown Heights, NY 10598, USA
     52 /*
     53 /*	Wietse Venema
     54 /*	Google, Inc.
     55 /*	111 8th Avenue
     56 /*	New York, NY 10011, USA
     57 /*--*/
     58 
     59 /* System library. */
     60 
     61 #include <sys_defs.h>
     62 #include <string.h>
     63 #ifdef STRCASECMP_IN_STRINGS_H
     64 #include <strings.h>
     65 #endif
     66 
     67 /* Utility library. */
     68 
     69 #include <msg.h>
     70 #include <mymalloc.h>
     71 #include <stringops.h>
     72 
     73 /* Global library. */
     74 
     75 #include <mail_params.h>
     76 #include <sasl_mech_filter.h>
     77 
     78 /* Application-specific. */
     79 
     80 #include "smtp.h"
     81 #include "smtp_sasl.h"
     82 
     83 #ifdef USE_SASL_AUTH
     84 
     85 /* smtp_sasl_helo_auth - handle AUTH option in EHLO reply */
     86 
     87 void    smtp_sasl_helo_auth(SMTP_SESSION *session, const char *words)
     88 {
     89     const char *mech_list = sasl_mech_filter(smtp_sasl_mechs, words);
     90     char   *junk;
     91 
     92     /*
     93      * XXX If the server offers no compatible authentication mechanisms, then
     94      * pretend that the server doesn't support SASL authentication.
     95      *
     96      * XXX If the server offers multiple different lists, concatenate them. Let
     97      * the SASL library worry about duplicates.
     98      */
     99     if (session->sasl_mechanism_list) {
    100 	if (strcasecmp(session->sasl_mechanism_list, mech_list) != 0
    101 	    && strlen(mech_list) > 0
    102 	    && strlen(session->sasl_mechanism_list) < var_line_limit) {
    103 	    junk = concatenate(session->sasl_mechanism_list, " ", mech_list,
    104 			       (char *) 0);
    105 	    myfree(session->sasl_mechanism_list);
    106 	    session->sasl_mechanism_list = junk;
    107 	}
    108 	return;
    109     }
    110     if (strlen(mech_list) > 0) {
    111 	session->sasl_mechanism_list = mystrdup(mech_list);
    112     } else {
    113 	msg_warn(*words ? "%s offered no supported AUTH mechanisms: '%s'" :
    114 		 "%s offered null AUTH mechanism list%s",
    115 		 session->namaddrport, words);
    116     }
    117     session->features |= SMTP_FEATURE_AUTH;
    118 }
    119 
    120 /* smtp_sasl_helo_login - perform SASL login */
    121 
    122 int     smtp_sasl_helo_login(SMTP_STATE *state)
    123 {
    124     SMTP_SESSION *session = state->session;
    125     DSN_BUF *why = state->why;
    126     int     ret;
    127 
    128     /*
    129      * Skip authentication when no authentication info exists for this
    130      * server, so that we talk to each other like strangers.
    131      */
    132     if (smtp_sasl_passwd_lookup(session) == 0) {
    133 	session->features &= ~SMTP_FEATURE_AUTH;
    134 	return 0;
    135     }
    136 
    137     /*
    138      * Otherwise, if authentication information exists, assume that
    139      * authentication is required, and assume that an authentication error is
    140      * recoverable from the message delivery point of view. An authentication
    141      * error is unrecoverable from a session point of view - the session will
    142      * not be reused.
    143      */
    144     ret = 0;
    145     if (session->sasl_mechanism_list == 0) {
    146 	dsb_simple(why, "4.7.0", "SASL authentication failed: "
    147 		   "server %s offered no compatible authentication mechanisms for this type of connection security",
    148 		   session->namaddr);
    149 	ret = smtp_sess_fail(state);
    150 	/* Session reuse is disabled. */
    151     } else {
    152 #ifndef USE_TLS
    153 	smtp_sasl_start(session, VAR_LMTP_SMTP(SASL_OPTS), var_smtp_sasl_opts);
    154 #else
    155 	if (session->tls_context == 0)
    156 	    smtp_sasl_start(session, VAR_LMTP_SMTP(SASL_OPTS),
    157 			    var_smtp_sasl_opts);
    158 	else if (TLS_CERT_IS_MATCHED(session->tls_context))
    159 	    smtp_sasl_start(session, VAR_LMTP_SMTP(SASL_TLSV_OPTS),
    160 			    var_smtp_sasl_tlsv_opts);
    161 	else
    162 	    smtp_sasl_start(session, VAR_LMTP_SMTP(SASL_TLS_OPTS),
    163 			    var_smtp_sasl_tls_opts);
    164 #endif
    165 	if (smtp_sasl_authenticate(session, why) <= 0) {
    166 	    ret = smtp_sess_fail(state);
    167 	    /* Session reuse is disabled. */
    168 	}
    169     }
    170     return (ret);
    171 }
    172 
    173 #endif
    174