path: root/src/tlsproxy/tlsproxy.c

/*++
/* NAME
/*	tlsproxy 8
/* SUMMARY
/*	Postfix TLS proxy
/* SYNOPSIS
/*	\fBtlsproxy\fR [generic Postfix daemon options]
/* DESCRIPTION
/*	The \fBtlsproxy\fR(8) server implements a two-way TLS proxy. It
/*	is used by the \fBpostscreen\fR(8) server to talk SMTP-over-TLS
/*	with remote SMTP clients that are not allowlisted (including
/*	clients whose allowlist status has expired), and by the
/*	\fBsmtp\fR(8) client to support TLS connection reuse, but it
/*	should also work for non-SMTP protocols.
/*
/*	Although one \fBtlsproxy\fR(8) process can serve multiple
/*	sessions at the same time, it is a good idea to allow the
/*	number of processes to increase with load, so that the
/*	service remains responsive.
/* PROTOCOL EXAMPLE
/* .ad
/* .fi
/*	The example below concerns \fBpostscreen\fR(8). However,
/*	the \fBtlsproxy\fR(8) server is agnostic of the application
/*	protocol, and the example is easily adapted to other
/*	applications.
/*
/*	After receiving a valid remote SMTP client STARTTLS command,
/*	the \fBpostscreen\fR(8) server sends the remote SMTP client
/*	endpoint string, the requested role (server), and the
/*	requested timeout to \fBtlsproxy\fR(8).  \fBpostscreen\fR(8)
/*	then receives a "TLS available" indication from \fBtlsproxy\fR(8).
/*	If the TLS service is available, \fBpostscreen\fR(8) sends
/*	the remote SMTP client file descriptor to \fBtlsproxy\fR(8),
/*	and sends the plaintext 220 greeting to the remote SMTP
/*	client.  This triggers TLS negotiations between the remote
/*	SMTP client and \fBtlsproxy\fR(8).  Upon completion of the
/*	TLS-level handshake, \fBtlsproxy\fR(8) translates between
/*	plaintext from/to \fBpostscreen\fR(8) and ciphertext to/from
/*	the remote SMTP client.
/* SECURITY
/* .ad
/* .fi
/*	The \fBtlsproxy\fR(8) server is moderately security-sensitive.
/*	It talks to untrusted clients on the network. The process
/*	can be run chrooted at fixed low privilege.
/* DIAGNOSTICS
/*	Problems and transactions are logged to \fBsyslogd\fR(8)
/*	or \fBpostlogd\fR(8).
/* CONFIGURATION PARAMETERS
/* .ad
/* .fi
/*	Changes to \fBmain.cf\fR are not picked up automatically,
/*	as \fBtlsproxy\fR(8) processes may run for a long time
/*	depending on mail server load.  Use the command "\fBpostfix
/*	reload\fR" to speed up a change.
/*
/*	The text below provides only a parameter summary. See
/*	\fBpostconf\fR(5) for more details including examples.
/* STARTTLS GLOBAL CONTROLS
/* .ad
/* .fi
/*	The following settings are global and therefore cannot be
/*	overruled by information specified in a \fBtlsproxy\fR(8)
/*	client request.
/* .IP "\fBtls_append_default_CA (no)\fR"
/*	Append the system-supplied default Certification Authority
/*	certificates to the ones specified with *_tls_CApath or *_tls_CAfile.
/* .IP "\fBtls_daemon_random_bytes (32)\fR"
/*	The number of pseudo-random bytes that an \fBsmtp\fR(8) or \fBsmtpd\fR(8)
/*	process requests from the \fBtlsmgr\fR(8) server in order to seed its
/*	internal pseudo random number generator (PRNG).
/* .IP "\fBtls_high_cipherlist (see 'postconf -d' output)\fR"
/*	The OpenSSL cipherlist for "high" grade ciphers.
/* .IP "\fBtls_medium_cipherlist (see 'postconf -d' output)\fR"
/*	The OpenSSL cipherlist for "medium" or higher grade ciphers.
/* .IP "\fBtls_low_cipherlist (see 'postconf -d' output)\fR"
/*	The OpenSSL cipherlist for "low" or higher grade ciphers.
/* .IP "\fBtls_export_cipherlist (see 'postconf -d' output)\fR"
/*	The OpenSSL cipherlist for "export" or higher grade ciphers.
/* .IP "\fBtls_null_cipherlist (eNULL:!aNULL)\fR"
/*	The OpenSSL cipherlist for "NULL" grade ciphers that provide
/*	authentication without encryption.
/* .IP "\fBtls_eecdh_strong_curve (prime256v1)\fR"
/*	The elliptic curve used by the Postfix SMTP server for sensibly
/*	strong
/*	ephemeral ECDH key exchange.
/* .IP "\fBtls_eecdh_ultra_curve (secp384r1)\fR"
/*	The elliptic curve used by the Postfix SMTP server for maximally
/*	strong
/*	ephemeral ECDH key exchange.
/* .IP "\fBtls_disable_workarounds (see 'postconf -d' output)\fR"
/*	List or bit-mask of OpenSSL bug work-arounds to disable.
/* .IP "\fBtls_preempt_cipherlist (no)\fR"
/*	With SSLv3 and later, use the Postfix SMTP server's cipher
/*	preference order instead of the remote client's cipher preference
/*	order.
/* .PP
/*	Available in Postfix version 2.9 and later:
/* .IP "\fBtls_legacy_public_key_fingerprints (no)\fR"
/*	A temporary migration aid for sites that use certificate
/*	\fIpublic-key\fR fingerprints with Postfix 2.9.0..2.9.5, which use
/*	an incorrect algorithm.
/* .PP
/*	Available in Postfix version 2.11-3.1:
/* .IP "\fBtls_dane_digest_agility (on)\fR"
/*	Configure RFC7671 DANE TLSA digest algorithm agility.
/* .IP "\fBtls_dane_trust_anchor_digest_enable (yes)\fR"
/*	Enable support for RFC 6698 (DANE TLSA) DNS records that contain
/*	digests of trust-anchors with certificate usage "2".
/* .PP
/*	Available in Postfix version 2.11 and later:
/* .IP "\fBtlsmgr_service_name (tlsmgr)\fR"
/*	The name of the \fBtlsmgr\fR(8) service entry in master.cf.
/* .PP
/*	Available in Postfix version 3.0 and later:
/* .IP "\fBtls_session_ticket_cipher (Postfix >= 3.0: aes-256-cbc, Postfix < 3.0: aes-128-cbc)\fR"
/*	Algorithm used to encrypt RFC5077 TLS session tickets.
/* .IP "\fBopenssl_path (openssl)\fR"
/*	The location of the OpenSSL command line program \fBopenssl\fR(1).
/* .PP
/*	Available in Postfix version 3.2 and later:
/* .IP "\fBtls_eecdh_auto_curves (see 'postconf -d' output)\fR"
/*	The prioritized list of elliptic curves supported by the Postfix
/*	SMTP client and server.
/* .PP
/*	Available in Postfix version 3.4 and later:
/* .IP "\fBtls_server_sni_maps (empty)\fR"
/*	Optional lookup tables that map names received from remote SMTP
/*	clients via the TLS Server Name Indication (SNI) extension to the
/*	appropriate keys and certificate chains.
/* .PP
/*	Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:
/* .IP "\fBtls_fast_shutdown_enable (yes)\fR"
/*	A workaround for implementations that hang Postfix while shutting
/*	down a TLS session, until Postfix times out.
/* .PP
/*	Available in Postfix 3.9, 3.8.1, 3.7.6, 3.6.10, 3.5.20 and later:
/* .IP "\fBtls_config_file (default)\fR"
/*	Optional configuration file with baseline OpenSSL settings.
/* .IP "\fBtls_config_name (empty)\fR"
/*	The application name passed by Postfix to OpenSSL library
/*	initialization functions.
/* STARTTLS SERVER CONTROLS
/* .ad
/* .fi
/*	These settings are clones of Postfix SMTP server settings.
/*	They allow \fBtlsproxy\fR(8) to load the same certificate
/*	and private key information as the Postfix SMTP server,
/*	before dropping privileges, so that the key files can be
/*	kept read-only for root. These settings can currently not
/*	be overruled by information in a \fBtlsproxy\fR(8) client
/*	request, but that limitation may be removed in a future
/*	version.
/* .IP "\fBtlsproxy_tls_CAfile ($smtpd_tls_CAfile)\fR"
/*	A file containing (PEM format) CA certificates of root CAs
/*	trusted to sign either remote SMTP client certificates or intermediate
/*	CA certificates.
/* .IP "\fBtlsproxy_tls_CApath ($smtpd_tls_CApath)\fR"
/*	A directory containing (PEM format) CA certificates of root CAs
/*	trusted to sign either remote SMTP client certificates or intermediate
/*	CA certificates.
/* .IP "\fBtlsproxy_tls_always_issue_session_ids ($smtpd_tls_always_issue_session_ids)\fR"
/*	Force the Postfix \fBtlsproxy\fR(8) server to issue a TLS session id,
/*	even when TLS session caching is turned off.
/* .IP "\fBtlsproxy_tls_ask_ccert ($smtpd_tls_ask_ccert)\fR"
/*	Ask a remote SMTP client for a client certificate.
/* .IP "\fBtlsproxy_tls_ccert_verifydepth ($smtpd_tls_ccert_verifydepth)\fR"
/*	The verification depth for remote SMTP client certificates.
/* .IP "\fBtlsproxy_tls_cert_file ($smtpd_tls_cert_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) server RSA certificate in PEM
/*	format.
/* .IP "\fBtlsproxy_tls_ciphers ($smtpd_tls_ciphers)\fR"
/*	The minimum TLS cipher grade that the Postfix \fBtlsproxy\fR(8) server
/*	will use with opportunistic TLS encryption.
/* .IP "\fBtlsproxy_tls_dcert_file ($smtpd_tls_dcert_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) server DSA certificate in PEM
/*	format.
/* .IP "\fBtlsproxy_tls_dh1024_param_file ($smtpd_tls_dh1024_param_file)\fR"
/*	File with DH parameters that the Postfix \fBtlsproxy\fR(8) server
/*	should use with non-export EDH ciphers.
/* .IP "\fBtlsproxy_tls_dh512_param_file ($smtpd_tls_dh512_param_file)\fR"
/*	File with DH parameters that the Postfix \fBtlsproxy\fR(8) server
/*	should use with export-grade EDH ciphers.
/* .IP "\fBtlsproxy_tls_dkey_file ($smtpd_tls_dkey_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) server DSA private key in PEM
/*	format.
/* .IP "\fBtlsproxy_tls_eccert_file ($smtpd_tls_eccert_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) server ECDSA certificate in PEM
/*	format.
/* .IP "\fBtlsproxy_tls_eckey_file ($smtpd_tls_eckey_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) server ECDSA private key in PEM
/*	format.
/* .IP "\fBtlsproxy_tls_eecdh_grade ($smtpd_tls_eecdh_grade)\fR"
/*	The Postfix \fBtlsproxy\fR(8) server security grade for ephemeral
/*	elliptic-curve Diffie-Hellman (EECDH) key exchange.
/* .IP "\fBtlsproxy_tls_exclude_ciphers ($smtpd_tls_exclude_ciphers)\fR"
/*	List of ciphers or cipher types to exclude from the \fBtlsproxy\fR(8)
/*	server cipher list at all TLS security levels.
/* .IP "\fBtlsproxy_tls_fingerprint_digest ($smtpd_tls_fingerprint_digest)\fR"
/*	The message digest algorithm to construct remote SMTP
/*	client-certificate
/*	fingerprints.
/* .IP "\fBtlsproxy_tls_key_file ($smtpd_tls_key_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) server RSA private key in PEM
/*	format.
/* .IP "\fBtlsproxy_tls_loglevel ($smtpd_tls_loglevel)\fR"
/*	Enable additional Postfix \fBtlsproxy\fR(8) server logging of TLS
/*	activity.
/* .IP "\fBtlsproxy_tls_mandatory_ciphers ($smtpd_tls_mandatory_ciphers)\fR"
/*	The minimum TLS cipher grade that the Postfix \fBtlsproxy\fR(8) server
/*	will use with mandatory TLS encryption.
/* .IP "\fBtlsproxy_tls_mandatory_exclude_ciphers ($smtpd_tls_mandatory_exclude_ciphers)\fR"
/*	Additional list of ciphers or cipher types to exclude from the
/*	\fBtlsproxy\fR(8) server cipher list at mandatory TLS security levels.
/* .IP "\fBtlsproxy_tls_mandatory_protocols ($smtpd_tls_mandatory_protocols)\fR"
/*	The SSL/TLS protocols accepted by the Postfix \fBtlsproxy\fR(8) server
/*	with mandatory TLS encryption.
/* .IP "\fBtlsproxy_tls_protocols ($smtpd_tls_protocols)\fR"
/*	List of TLS protocols that the Postfix \fBtlsproxy\fR(8) server will
/*	exclude or include with opportunistic TLS encryption.
/* .IP "\fBtlsproxy_tls_req_ccert ($smtpd_tls_req_ccert)\fR"
/*	With mandatory TLS encryption, require a trusted remote SMTP
/*	client certificate in order to allow TLS connections to proceed.
/* .IP "\fBtlsproxy_tls_security_level ($smtpd_tls_security_level)\fR"
/*	The SMTP TLS security level for the Postfix \fBtlsproxy\fR(8) server;
/*	when a non-empty value is specified, this overrides the obsolete
/*	parameters smtpd_use_tls and smtpd_enforce_tls.
/* .IP "\fBtlsproxy_tls_chain_files ($smtpd_tls_chain_files)\fR"
/*	Files with the Postfix \fBtlsproxy\fR(8) server keys and certificate
/*	chains in PEM format.
/* STARTTLS CLIENT CONTROLS
/* .ad
/* .fi
/*	These settings are clones of Postfix SMTP client settings.
/*	They allow \fBtlsproxy\fR(8) to load the same certificate
/*	and private key information as the Postfix SMTP client,
/*	before dropping privileges, so that the key files can be
/*	kept read-only for root. Some settings may be overruled by
/*	information in a \fBtlsproxy\fR(8) client request.
/* .PP
/*	Available in Postfix version 3.4 and later:
/* .IP "\fBtlsproxy_client_CAfile ($smtp_tls_CAfile)\fR"
/*	A file containing CA certificates of root CAs trusted to sign
/*	either remote TLS server certificates or intermediate CA certificates.
/* .IP "\fBtlsproxy_client_CApath ($smtp_tls_CApath)\fR"
/*	Directory with PEM format Certification Authority certificates
/*	that the Postfix \fBtlsproxy\fR(8) client uses to verify a remote TLS
/*	server certificate.
/* .IP "\fBtlsproxy_client_chain_files ($smtp_tls_chain_files)\fR"
/*	Files with the Postfix \fBtlsproxy\fR(8) client keys and certificate
/*	chains in PEM format.
/* .IP "\fBtlsproxy_client_cert_file ($smtp_tls_cert_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) client RSA certificate in PEM
/*	format.
/* .IP "\fBtlsproxy_client_key_file ($smtp_tls_key_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) client RSA private key in PEM
/*	format.
/* .IP "\fBtlsproxy_client_dcert_file ($smtp_tls_dcert_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) client DSA certificate in PEM
/*	format.
/* .IP "\fBtlsproxy_client_dkey_file ($smtp_tls_dkey_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) client DSA private key in PEM
/*	format.
/* .IP "\fBtlsproxy_client_eccert_file ($smtp_tls_eccert_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) client ECDSA certificate in PEM
/*	format.
/* .IP "\fBtlsproxy_client_eckey_file ($smtp_tls_eckey_file)\fR"
/*	File with the Postfix \fBtlsproxy\fR(8) client ECDSA private key in PEM
/*	format.
/* .IP "\fBtlsproxy_client_fingerprint_digest ($smtp_tls_fingerprint_digest)\fR"
/*	The message digest algorithm used to construct remote TLS server
/*	certificate fingerprints.
/* .IP "\fBtlsproxy_client_loglevel ($smtp_tls_loglevel)\fR"
/*	Enable additional Postfix \fBtlsproxy\fR(8) client logging of TLS
/*	activity.
/* .IP "\fBtlsproxy_client_loglevel_parameter (smtp_tls_loglevel)\fR"
/*	The name of the parameter that provides the tlsproxy_client_loglevel
/*	value.
/* .IP "\fBtlsproxy_client_scert_verifydepth ($smtp_tls_scert_verifydepth)\fR"
/*	The verification depth for remote TLS server certificates.
/* .IP "\fBtlsproxy_client_use_tls ($smtp_use_tls)\fR"
/*	Opportunistic mode: use TLS when a remote server announces TLS
/*	support.
/* .IP "\fBtlsproxy_client_enforce_tls ($smtp_enforce_tls)\fR"
/*	Enforcement mode: require that SMTP servers use TLS encryption.
/* .IP "\fBtlsproxy_client_per_site ($smtp_tls_per_site)\fR"
/*	Optional lookup tables with the Postfix \fBtlsproxy\fR(8) client TLS
/*	usage policy by next-hop destination and by remote TLS server
/*	hostname.
/* .PP
/*	Available in Postfix version 3.4-3.6:
/* .IP "\fBtlsproxy_client_level ($smtp_tls_security_level)\fR"
/*	The default TLS security level for the Postfix \fBtlsproxy\fR(8)
/*	client.
/* .IP "\fBtlsproxy_client_policy ($smtp_tls_policy_maps)\fR"
/*	Optional lookup tables with the Postfix \fBtlsproxy\fR(8) client TLS
/*	security policy by next-hop destination.
/* .PP
/*	Available in Postfix version 3.7 and later:
/* .IP "\fBtlsproxy_client_security_level ($smtp_tls_security_level)\fR"
/*	The default TLS security level for the Postfix \fBtlsproxy\fR(8)
/*	client.
/* .IP "\fBtlsproxy_client_policy_maps ($smtp_tls_policy_maps)\fR"
/*	Optional lookup tables with the Postfix \fBtlsproxy\fR(8) client TLS
/*	security policy by next-hop destination.
/* OBSOLETE STARTTLS SUPPORT CONTROLS
/* .ad
/* .fi
/*	These parameters are supported for compatibility with
/*	\fBsmtpd\fR(8) legacy parameters.
/* .IP "\fBtlsproxy_use_tls ($smtpd_use_tls)\fR"
/*	Opportunistic TLS: announce STARTTLS support to remote SMTP clients,
/*	but do not require that clients use TLS encryption.
/* .IP "\fBtlsproxy_enforce_tls ($smtpd_enforce_tls)\fR"
/*	Mandatory TLS: announce STARTTLS support to remote SMTP clients, and
/*	require that clients use TLS encryption.
/* .IP "\fBtlsproxy_client_use_tls ($smtp_use_tls)\fR"
/*	Opportunistic mode: use TLS when a remote server announces TLS
/*	support.
/* .IP "\fBtlsproxy_client_enforce_tls ($smtp_enforce_tls)\fR"
/*	Enforcement mode: require that SMTP servers use TLS encryption.
/* RESOURCE CONTROLS
/* .ad
/* .fi
/* .IP "\fBtlsproxy_watchdog_timeout (10s)\fR"
/*	How much time a \fBtlsproxy\fR(8) process may take to process local
/*	or remote I/O before it is terminated by a built-in watchdog timer.
/* MISCELLANEOUS CONTROLS
/* .ad
/* .fi
/* .IP "\fBconfig_directory (see 'postconf -d' output)\fR"
/*	The default location of the Postfix main.cf and master.cf
/*	configuration files.
/* .IP "\fBprocess_id (read-only)\fR"
/*	The process ID of a Postfix command or daemon process.
/* .IP "\fBprocess_name (read-only)\fR"
/*	The process name of a Postfix command or daemon process.
/* .IP "\fBsyslog_facility (mail)\fR"
/*	The syslog facility of Postfix logging.
/* .IP "\fBsyslog_name (see 'postconf -d' output)\fR"
/*	A prefix that is prepended to the process name in syslog
/*	records, so that, for example, "smtpd" becomes "prefix/smtpd".
/* .PP
/*	Available in Postfix 3.3 and later:
/* .IP "\fBservice_name (read-only)\fR"
/*	The master.cf service name of a Postfix daemon process.
/* SEE ALSO
/*	postscreen(8), Postfix zombie blocker
/*	smtpd(8), Postfix SMTP server
/*	postconf(5), configuration parameters
/*	postlogd(8), Postfix logging
/*	syslogd(8), system logging
/* LICENSE
/* .ad
/* .fi
/*	The Secure Mailer license must be distributed with this software.
/* HISTORY
/* .ad
/* .fi
/*	This service was introduced with Postfix version 2.8.
/* AUTHOR(S)
/*	Wietse Venema
/*	IBM T.J. Watson Research
/*	P.O. Box 704
/*	Yorktown Heights, NY 10598, USA
/*
/*	Wietse Venema
/*	Google, Inc.
/*	111 8th Avenue
/*	New York, NY 10011, USA
/*--*/

 /*
  * System library.
  */
#include <sys_defs.h>
#include <errno.h>

#ifdef STRCASECMP_IN_STRINGS_H
#include <strings.h>
#endif

 /*
  * Utility library.
  */
#include <msg.h>
#include <vstream.h>
#include <iostuff.h>
#include <nbbio.h>
#include <mymalloc.h>
#include <split_at.h>

 /*
  * Global library.
  */
#include <been_here.h>
#include <mail_proto.h>
#include <mail_params.h>
#include <mail_conf.h>
#include <mail_version.h>

 /*
  * Master library.
  */
#include <mail_server.h>

 /*
  * TLS library.
  */
#ifdef USE_TLS
#define TLS_INTERNAL			/* XXX */
#include <tls.h>
#include <tls_proxy.h>

 /*
  * Application-specific.
  */
#include <tlsproxy.h>

 /*
  * Tunable parameters. We define our clones of the smtpd(8) parameters to
  * avoid any confusion about which parameters are used by this program.
  */
int     var_smtpd_tls_ccert_vd;
char   *var_smtpd_tls_loglevel;
bool    var_smtpd_use_tls;
bool    var_smtpd_enforce_tls;
bool    var_smtpd_tls_ask_ccert;
bool    var_smtpd_tls_req_ccert;
bool    var_smtpd_tls_set_sessid;
char   *var_smtpd_relay_ccerts;
char   *var_smtpd_tls_chain_files;
char   *var_smtpd_tls_cert_file;
char   *var_smtpd_tls_key_file;
char   *var_smtpd_tls_dcert_file;
char   *var_smtpd_tls_dkey_file;
char   *var_smtpd_tls_eccert_file;
char   *var_smtpd_tls_eckey_file;
char   *var_smtpd_tls_CAfile;
char   *var_smtpd_tls_CApath;
char   *var_smtpd_tls_ciph;
char   *var_smtpd_tls_mand_ciph;
char   *var_smtpd_tls_excl_ciph;
char   *var_smtpd_tls_mand_excl;
char   *var_smtpd_tls_proto;
char   *var_smtpd_tls_mand_proto;
char   *var_smtpd_tls_dh512_param_file;
char   *var_smtpd_tls_dh1024_param_file;
char   *var_smtpd_tls_eecdh;
char   *var_smtpd_tls_fpt_dgst;
char   *var_smtpd_tls_level;

int     var_tlsp_tls_ccert_vd;
char   *var_tlsp_tls_loglevel;
bool    var_tlsp_use_tls;
bool    var_tlsp_enforce_tls;
bool    var_tlsp_tls_ask_ccert;
bool    var_tlsp_tls_req_ccert;
bool    var_tlsp_tls_set_sessid;
char   *var_tlsp_tls_chain_files;
char   *var_tlsp_tls_cert_file;
char   *var_tlsp_tls_key_file;
char   *var_tlsp_tls_dcert_file;
char   *var_tlsp_tls_dkey_file;
char   *var_tlsp_tls_eccert_file;
char   *var_tlsp_tls_eckey_file;
char   *var_tlsp_tls_CAfile;
char   *var_tlsp_tls_CApath;
char   *var_tlsp_tls_ciph;
char   *var_tlsp_tls_mand_ciph;
char   *var_tlsp_tls_excl_ciph;
char   *var_tlsp_tls_mand_excl;
char   *var_tlsp_tls_proto;
char   *var_tlsp_tls_mand_proto;
char   *var_tlsp_tls_dh512_param_file;
char   *var_tlsp_tls_dh1024_param_file;
char   *var_tlsp_tls_eecdh;
char   *var_tlsp_tls_fpt_dgst;
char   *var_tlsp_tls_level;

int     var_tlsp_watchdog;

 /*
  * Defaults for tlsp_clnt_*.
  */
char   *var_smtp_tls_loglevel;
int     var_smtp_tls_scert_vd;
char   *var_smtp_tls_chain_files;
char   *var_smtp_tls_cert_file;
char   *var_smtp_tls_key_file;
char   *var_smtp_tls_dcert_file;
char   *var_smtp_tls_dkey_file;
char   *var_smtp_tls_eccert_file;
char   *var_smtp_tls_eckey_file;
char   *var_smtp_tls_CAfile;
char   *var_smtp_tls_CApath;
char   *var_smtp_tls_fpt_dgst;
char   *var_smtp_tls_level;
bool    var_smtp_use_tls;
bool    var_smtp_enforce_tls;
char   *var_smtp_tls_per_site;
char   *var_smtp_tls_policy;

char   *var_tlsp_clnt_loglevel;
char   *var_tlsp_clnt_logparam;
int     var_tlsp_clnt_scert_vd;
char   *var_tlsp_clnt_chain_files;
char   *var_tlsp_clnt_cert_file;
char   *var_tlsp_clnt_key_file;
char   *var_tlsp_clnt_dcert_file;
char   *var_tlsp_clnt_dkey_file;
char   *var_tlsp_clnt_eccert_file;
char   *var_tlsp_clnt_eckey_file;
char   *var_tlsp_clnt_CAfile;
char   *var_tlsp_clnt_CApath;
char   *var_tlsp_clnt_fpt_dgst;
char   *var_tlsp_clnt_level;
bool    var_tlsp_clnt_use_tls;
bool    var_tlsp_clnt_enforce_tls;
char   *var_tlsp_clnt_per_site;
char   *var_tlsp_clnt_policy;

 /*
  * TLS per-process status.
  */
static TLS_APPL_STATE *tlsp_server_ctx;
static bool tlsp_pre_jail_done;
static int ask_client_cert;
static char *tlsp_pre_jail_client_param_key;	/* pre-jail global params */
static char *tlsp_pre_jail_client_init_key;	/* pre-jail init props */

 /*
  * TLS per-client status.
  */
static HTABLE *tlsp_client_app_cache;	/* per-client init props */
static BH_TABLE *tlsp_params_mismatch_filter;	/* per-client nag filter */

 /*
  * Error handling: if a function detects an error, then that function is
  * responsible for destroying TLSP_STATE. Exceptions to this principle are
  * indicated in the code.
  */

 /*
  * Internal status API.
  */
#define TLSP_STAT_OK	0
#define TLSP_STAT_ERR	(-1)

 /*
  * SLMs.
  */
#define STR(x)	vstring_str(x)
#define LEN(x)	VSTRING_LEN(x)

 /*
  * The code that implements the TLS engine looks simpler than expected. That
  * is the result of a great deal of effort, mainly in design and analysis.
  * 
  * The initial use case was to provide TLS support for postscreen(8).
  * 
  * By design, postscreen(8) is an event-driven server that must scale up to a
  * large number of clients. This means that postscreen(8) must avoid doing
  * CPU-intensive operations such as those in OpenSSL.
  * 
  * tlsproxy(8) runs the OpenSSL code on behalf of postscreen(8), translating
  * plaintext SMTP messages from postscreen(8) into SMTP-over-TLS messages to
  * the remote SMTP client, and vice versa. As long as postscreen(8) does not
  * receive email messages, the cost of doing TLS operations will be modest.
  * 
  * Like postscreen(8), one tlsproxy(8) process services multiple remote SMTP
  * clients. Unlike postscreen(8), there can be more than one tlsproxy(8)
  * process, although their number is meant to be much smaller than the
  * number of remote SMTP clients that talk TLS.
  * 
  * As with postscreen(8), all I/O must be event-driven: encrypted traffic
  * between tlsproxy(8) and remote SMTP clients, and plaintext traffic
  * between tlsproxy(8) and postscreen(8). Event-driven plaintext I/O is
  * straightforward enough that it could be abstracted away with the nbbio(3)
  * module.
  * 
  * The event-driven TLS I/O implementation is founded on on-line OpenSSL
  * documentation, supplemented by statements from OpenSSL developers on
  * public mailing lists. After some field experience with this code, we may
  * be able to factor it out as a library module, like nbbio(3), that can
  * become part of the TLS library.
  * 
  * Later in the life cycle, tlsproxy(8) has also become an enabler for TLS
  * connection reuse across different SMTP client processes.
  */

static void tlsp_ciphertext_event(int, void *);

#define TLSP_INIT_TIMEOUT	100

static void tlsp_plaintext_event(int event, void *context);

/* tlsp_drain - delayed exit after "postfix reload" */

static void tlsp_drain(char *unused_service, char **unused_argv)
{
    int     count;

    /*
     * After "postfix reload", complete work-in-progress in the background,
     * instead of dropping already-accepted connections on the floor.
     * 
     * All error retry counts shall be limited. Instead of blocking here, we
     * could retry failed fork() operations in the event call-back routines,
     * but we don't need perfection. The host system is severely overloaded
     * and service levels are already way down.
     */
    for (count = 0; /* see below */ ; count++) {
	if (count >= 5) {
	    msg_fatal("fork: %m");
	} else if (event_server_drain() != 0) {
	    msg_warn("fork: %m");
	    sleep(1);
	    continue;
	} else {
	    return;
	}
    }
}

/* tlsp_eval_tls_error - translate TLS "error" result into action */

static int tlsp_eval_tls_error(TLSP_STATE *state, int err)
{
    int     ciphertext_fd = state->ciphertext_fd;

    /*
     * The ciphertext file descriptor is in non-blocking mode, meaning that
     * each SSL_accept/connect/read/write/shutdown request may return an
     * "error" indication that it needs to read or write more ciphertext. The
     * purpose of this routine is to translate those "error" indications into
     * the appropriate read/write/timeout event requests.
     */
    switch (err) {

	/*
	 * No error means a successful SSL_accept/connect/shutdown request or
	 * sequence of SSL_read/write requests. Disable read/write events on
	 * the ciphertext stream. Keep the ciphertext stream timer alive as a
	 * safety mechanism for the case that the plaintext pseudothreads get
	 * stuck.
	 */
    case SSL_ERROR_NONE:
	if (state->ssl_last_err != SSL_ERROR_NONE) {
	    event_disable_readwrite(ciphertext_fd);
	    event_request_timer(tlsp_ciphertext_event, (void *) state,
				state->timeout);
	    state->ssl_last_err = SSL_ERROR_NONE;
	}
	return (TLSP_STAT_OK);

	/*
	 * The TLS engine wants to write to the network. Turn on
	 * write/timeout events on the ciphertext stream.
	 */
    case SSL_ERROR_WANT_WRITE:
	if (state->ssl_last_err == SSL_ERROR_WANT_READ)
	    event_disable_readwrite(ciphertext_fd);
	if (state->ssl_last_err != SSL_ERROR_WANT_WRITE) {
	    event_enable_write(ciphertext_fd, tlsp_ciphertext_event,
			       (void *) state);
	    state->ssl_last_err = SSL_ERROR_WANT_WRITE;
	}
	event_request_timer(tlsp_ciphertext_event, (void *) state,
			    state->timeout);
	return (TLSP_STAT_OK);

	/*
	 * The TLS engine wants to read from the network. Turn on
	 * read/timeout events on the ciphertext stream.
	 */
    case SSL_ERROR_WANT_READ:
	if (state->ssl_last_err == SSL_ERROR_WANT_WRITE)
	    event_disable_readwrite(ciphertext_fd);
	if (state->ssl_last_err != SSL_ERROR_WANT_READ) {
	    event_enable_read(ciphertext_fd, tlsp_ciphertext_event,
			      (void *) state);
	    state->ssl_last_err = SSL_ERROR_WANT_READ;
	}
	event_request_timer(tlsp_ciphertext_event, (void *) state,
			    state->timeout);
	return (TLSP_STAT_OK);

	/*
	 * Some error. Self-destruct. This automagically cleans up all
	 * pending read/write and timeout event requests, making state a
	 * dangling pointer.
	 */
    case SSL_ERROR_SSL:
	tls_print_errors();
	/* FALLTHROUGH */
    default:

	/*
	 * Allow buffered-up plaintext output to trickle out. Permanently
	 * disable read/write activity on the ciphertext stream, so that this
	 * function will no longer be called. Keep the ciphertext stream
	 * timer alive as a safety mechanism for the case that the plaintext
	 * pseudothreads get stuck. Return into tlsp_strategy(), which will
	 * enable plaintext write events.
	 */
#define TLSP_CAN_TRICKLE_OUT_PLAINTEXT(buf) \
	((buf) && !NBBIO_ERROR_FLAGS(buf) && NBBIO_WRITE_PEND(buf))

	if (TLSP_CAN_TRICKLE_OUT_PLAINTEXT(state->plaintext_buf)) {
	    event_disable_readwrite(ciphertext_fd);
	    event_request_timer(tlsp_ciphertext_event, (void *) state,
				state->timeout);
	    state->flags |= TLSP_FLAG_NO_MORE_CIPHERTEXT_IO;
	    return (TLSP_STAT_OK);
	}
	tlsp_state_free(state);
	return (TLSP_STAT_ERR);
    }
}

/* tlsp_post_handshake - post-handshake processing */

static int tlsp_post_handshake(TLSP_STATE *state)
{

    /*
     * Do not assume that tls_server_post_accept() and
     * tls_client_post_connect() will always succeed.
     */
    if (state->is_server_role)
	state->tls_context = tls_server_post_accept(state->tls_context);
    else
	state->tls_context = tls_client_post_connect(state->tls_context,
						 state->client_start_props);
    if (state->tls_context == 0) {
	tlsp_state_free(state);
	return (TLSP_STAT_ERR);
    }

    /*
     * Report TLS handshake results to the tlsproxy client.
     * 
     * Security: this sends internal data over the same local plaintext stream
     * that will also be used for sending decrypted remote content from an
     * arbitrary remote peer. For this reason we enable decrypted I/O only
     * after reporting the TLS handshake results. The Postfix attribute
     * protocol is robust enough that an attacker cannot append content.
     */
    if ((state->req_flags & TLS_PROXY_FLAG_SEND_CONTEXT) != 0
	&& (attr_print(state->plaintext_stream, ATTR_FLAG_NONE,
		       SEND_ATTR_FUNC(tls_proxy_context_print,
				      (void *) state->tls_context),
		       ATTR_TYPE_END) != 0
	    || vstream_fflush(state->plaintext_stream) != 0)) {
	msg_warn("cannot send TLS context: %m");
	tlsp_state_free(state);
	return (TLSP_STAT_ERR);
    }

    /*
     * Initialize plaintext-related session state. Once we have this behind
     * us, the TLSP_STATE destructor will automagically clean up requests for
     * plaintext read/write/timeout events, which makes error recovery
     * easier.
     */
    state->plaintext_buf =
	nbbio_create(vstream_fileno(state->plaintext_stream),
		     VSTREAM_BUFSIZE, state->server_id,
		     tlsp_plaintext_event,
		     (void *) state);
    return (TLSP_STAT_OK);
}

/* tlsp_strategy - decide what to read or write next. */

static void tlsp_strategy(TLSP_STATE *state)
{
    TLS_SESS_STATE *tls_context = state->tls_context;
    NBBIO  *plaintext_buf;
    int     ssl_stat;
    int     ssl_read_err;
    int     ssl_write_err;
    int     handshake_err;

    /*
     * This function is called after every ciphertext or plaintext event, to
     * schedule new ciphertext or plaintext I/O.
     */

    /*
     * Try to make an SSL I/O request. If this fails with SSL_ERROR_WANT_READ
     * or SSL_ERROR_WANT_WRITE, enable ciphertext read or write events, and
     * retry the SSL I/O request in a later tlsp_strategy() call.
     */
    if ((state->flags & TLSP_FLAG_NO_MORE_CIPHERTEXT_IO) == 0) {

	/*
	 * Do not enable plain-text I/O before completing the TLS handshake.
	 * Otherwise the remote peer can prepend plaintext to the optional
	 * TLS_SESS_STATE object.
	 */
	if (state->flags & TLSP_FLAG_DO_HANDSHAKE) {
	    state->timeout = state->handshake_timeout;
	    ERR_clear_error();
	    if (state->is_server_role)
		ssl_stat = SSL_accept(tls_context->con);
	    else
		ssl_stat = SSL_connect(tls_context->con);
	    if (ssl_stat != 1) {
		handshake_err = SSL_get_error(tls_context->con, ssl_stat);
		tlsp_eval_tls_error(state, handshake_err);
		/* At this point, state could be a dangling pointer. */
		return;
	    }
	    state->flags &= ~TLSP_FLAG_DO_HANDSHAKE;
	    state->timeout = state->session_timeout;
	    if (tlsp_post_handshake(state) != TLSP_STAT_OK) {
		/* At this point, state is a dangling pointer. */
		return;
	    }
	}

	/*
	 * Shutdown and self-destruct after NBBIO error. This automagically
	 * cleans up all pending read/write and timeout event requests.
	 * Before shutting down TLS, we stop all plain-text I/O events but
	 * keep the NBBIO error flags.
	 */
	plaintext_buf = state->plaintext_buf;
	if (NBBIO_ERROR_FLAGS(plaintext_buf)) {
	    if (NBBIO_ACTIVE_FLAGS(plaintext_buf))
		nbbio_disable_readwrite(state->plaintext_buf);
	    ERR_clear_error();
	    if (!SSL_in_init(tls_context->con)
		&& (ssl_stat = SSL_shutdown(tls_context->con)) < 0) {
		handshake_err = SSL_get_error(tls_context->con, ssl_stat);
		tlsp_eval_tls_error(state, handshake_err);
		/* At this point, state could be a dangling pointer. */
		return;
	    }
	    tlsp_state_free(state);
	    return;
	}

	/*
	 * Try to move data from the plaintext input buffer to the TLS
	 * engine.
	 * 
	 * XXX We're supposed to repeat the exact same SSL_write() call
	 * arguments after an SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE
	 * result. Rumor has it that this is because each SSL_write() call
	 * reads from the buffer incrementally, and returns > 0 only after
	 * the final byte is processed. Rumor also has it that setting
	 * SSL_MODE_ENABLE_PARTIAL_WRITE and
	 * SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER voids this requirement, and
	 * that repeating the request with an increased request size is OK.
	 * Unfortunately all this is not or poorly documented, and one has to
	 * rely on statements from OpenSSL developers in public mailing
	 * archives.
	 */
	ssl_write_err = SSL_ERROR_NONE;
	while (NBBIO_READ_PEND(plaintext_buf) > 0) {
	    ERR_clear_error();
	    ssl_stat = SSL_write(tls_context->con, NBBIO_READ_BUF(plaintext_buf),
				 NBBIO_READ_PEND(plaintext_buf));
	    ssl_write_err = SSL_get_error(tls_context->con, ssl_stat);
	    if (ssl_write_err != SSL_ERROR_NONE)
		break;
	    /* Allow the plaintext pseudothread to read more data. */
	    NBBIO_READ_PEND(plaintext_buf) -= ssl_stat;
	    if (NBBIO_READ_PEND(plaintext_buf) > 0)
		memmove(NBBIO_READ_BUF(plaintext_buf),
			NBBIO_READ_BUF(plaintext_buf) + ssl_stat,
			NBBIO_READ_PEND(plaintext_buf));
	}

	/*
	 * Try to move data from the TLS engine to the plaintext output
	 * buffer. Note: data may arrive as a side effect of calling
	 * SSL_write(), therefore we call SSL_read() after calling
	 * SSL_write().
	 * 
	 * XXX We're supposed to repeat the exact same SSL_read() call arguments
	 * after an SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE result. This
	 * supposedly means that our plaintext writer must not memmove() the
	 * plaintext output buffer until after the SSL_read() call succeeds.
	 * For now I'll ignore this, because 1) SSL_read() is documented to
	 * return the bytes available, instead of returning > 0 only after
	 * the entire buffer is processed like SSL_write() does; and 2) there
	 * is no "read" equivalent of the SSL_R_BAD_WRITE_RETRY,
	 * SSL_MODE_ENABLE_PARTIAL_WRITE or
	 * SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER features.
	 */
	ssl_read_err = SSL_ERROR_NONE;
	while (NBBIO_WRITE_PEND(state->plaintext_buf) < NBBIO_BUFSIZE(plaintext_buf)) {
	    ERR_clear_error();
	    ssl_stat = SSL_read(tls_context->con,
				NBBIO_WRITE_BUF(plaintext_buf)
				+ NBBIO_WRITE_PEND(state->plaintext_buf),
				NBBIO_BUFSIZE(plaintext_buf)
				- NBBIO_WRITE_PEND(state->plaintext_buf));
	    ssl_read_err = SSL_get_error(tls_context->con, ssl_stat);
	    if (ssl_read_err != SSL_ERROR_NONE)
		break;
	    NBBIO_WRITE_PEND(plaintext_buf) += ssl_stat;
	}

	/*
	 * Try to enable/disable ciphertext read/write events. If SSL_write()
	 * was satisfied, see if SSL_read() wants to do some work. In case of
	 * an unrecoverable error, this automagically destroys the session
	 * state after cleaning up all pending read/write and timeout event
	 * requests.
	 */
	if (tlsp_eval_tls_error(state, ssl_write_err != SSL_ERROR_NONE ?
				ssl_write_err : ssl_read_err) < 0)
	    /* At this point, state is a dangling pointer. */
	    return;
    }

    /*
     * Destroy state when the ciphertext I/O was permanently disabled and we
     * can no longer trickle out plaintext.
     */
    else {
	plaintext_buf = state->plaintext_buf;
	if (!TLSP_CAN_TRICKLE_OUT_PLAINTEXT(plaintext_buf)) {
	    tlsp_state_free(state);
	    return;
	}
    }

    /*
     * Try to enable/disable plaintext read/write events. Basically, if we
     * have nothing to write to the plaintext stream, see if there is
     * something to read. If the write buffer is empty and the read buffer is
     * full, suspend plaintext I/O until conditions change (but keep the
     * timer active, as a safety mechanism in case ciphertext I/O gets
     * stuck).
     * 
     * XXX In theory, if the ciphertext peer keeps writing fast enough then we
     * would never read from the plaintext stream and cause the latter to
     * block. In practice, postscreen(8) limits the number of client
     * commands, and thus postscreen(8)'s output will fit in a kernel buffer.
     * A remote SMTP server is not supposed to flood the local SMTP client
     * with massive replies; if it does, then the local SMTP client should
     * deal with it.
     */
    if (NBBIO_WRITE_PEND(plaintext_buf) > 0) {
	if (NBBIO_ACTIVE_FLAGS(plaintext_buf) & NBBIO_FLAG_READ)
	    nbbio_disable_readwrite(plaintext_buf);
	nbbio_enable_write(plaintext_buf, state->timeout);
    } else if (NBBIO_READ_PEND(plaintext_buf) < NBBIO_BUFSIZE(plaintext_buf)) {
	if (NBBIO_ACTIVE_FLAGS(plaintext_buf) & NBBIO_FLAG_WRITE)
	    nbbio_disable_readwrite(plaintext_buf);
	nbbio_enable_read(plaintext_buf, state->timeout);
    } else {
	if (NBBIO_ACTIVE_FLAGS(plaintext_buf))
	    nbbio_slumber(plaintext_buf, state->timeout);
    }
}

/* tlsp_plaintext_event - plaintext was read/written */

static void tlsp_plaintext_event(int event, void *context)
{
    TLSP_STATE *state = (TLSP_STATE *) context;

    /*
     * Safety alert: the plaintext pseudothreads have "slumbered" for too
     * long (see code above). This means that the ciphertext pseudothreads
     * are stuck.
     */
    if ((NBBIO_ERROR_FLAGS(state->plaintext_buf) & NBBIO_FLAG_TIMEOUT) != 0
	&& NBBIO_ACTIVE_FLAGS(state->plaintext_buf) == 0)
	msg_warn("deadlock on ciphertext stream for %s", state->remote_endpt);

    /*
     * This is easy, because the NBBIO layer has already done the event
     * decoding and plaintext I/O for us. All we need to do is decide if we
     * want to read or write more plaintext.
     */
    tlsp_strategy(state);
    /* At this point, state could be a dangling pointer. */
}

/* tlsp_ciphertext_event - ciphertext is ready to read/write */

static void tlsp_ciphertext_event(int event, void *context)
{
    TLSP_STATE *state = (TLSP_STATE *) context;

    /*
     * Without a TLS equivalent of the NBBIO layer, we must decode the events
     * ourselves and do the ciphertext I/O. Then, we can decide if we want to
     * read or write more ciphertext.
     */
    if (event == EVENT_READ || event == EVENT_WRITE) {
	tlsp_strategy(state);
	/* At this point, state could be a dangling pointer. */
    } else {
	if (event == EVENT_TIME && state->ssl_last_err == SSL_ERROR_NONE)
	    msg_warn("deadlock on plaintext stream for %s",
		     state->remote_endpt);
	else
	    msg_warn("ciphertext read/write %s for %s",
		     event == EVENT_TIME ? "timeout" : "error",
		     state->remote_endpt);
	tlsp_state_free(state);
    }
}

/* tlsp_client_start_pre_handshake - turn on TLS or force disconnect */

static int tlsp_client_start_pre_handshake(TLSP_STATE *state)
{
    state->client_start_props->ctx = state->appl_state;
    state->client_start_props->fd = state->ciphertext_fd;
    state->tls_context = tls_client_start(state->client_start_props);
    if (state->tls_context != 0)
	return (TLSP_STAT_OK);

    tlsp_state_free(state);
    return (TLSP_STAT_ERR);
}

/* tlsp_server_start_pre_handshake - turn on TLS or force disconnect */

static int tlsp_server_start_pre_handshake(TLSP_STATE *state)
{
    TLS_SERVER_START_PROPS props;
    static char *cipher_grade;
    static VSTRING *cipher_exclusions;

    /*
     * The code in this routine is pasted literally from smtpd(8). I am not
     * going to sanitize this because doing so surely will break things in
     * unexpected ways.
     */

    /*
     * Perform the before-handshake portion of per-session initialization.
     * Pass a null VSTREAM to indicate that this program will do the
     * ciphertext I/O, not libtls.
     * 
     * The cipher grade and exclusions don't change between sessions. Compute
     * just once and cache.
     */
#define ADD_EXCLUDE(vstr, str) \
    do { \
	if (*(str)) \
	    vstring_sprintf_append((vstr), "%s%s", \
				   VSTRING_LEN(vstr) ? " " : "", (str)); \
    } while (0)

    if (cipher_grade == 0) {
	cipher_grade =
	    var_tlsp_enforce_tls ? var_tlsp_tls_mand_ciph : var_tlsp_tls_ciph;
	cipher_exclusions = vstring_alloc(10);
	ADD_EXCLUDE(cipher_exclusions, var_tlsp_tls_excl_ciph);
	if (var_tlsp_enforce_tls)
	    ADD_EXCLUDE(cipher_exclusions, var_tlsp_tls_mand_excl);
	if (ask_client_cert)
	    ADD_EXCLUDE(cipher_exclusions, "aNULL");
    }
    state->tls_context =
	TLS_SERVER_START(&props,
			 ctx = tlsp_server_ctx,
			 stream = (VSTREAM *) 0,/* unused */
			 fd = state->ciphertext_fd,
			 timeout = 0,		/* unused */
			 requirecert = (var_tlsp_tls_req_ccert
					&& var_tlsp_enforce_tls),
			 serverid = state->server_id,
			 namaddr = state->remote_endpt,
			 cipher_grade = cipher_grade,
			 cipher_exclusions = STR(cipher_exclusions),
			 mdalg = var_tlsp_tls_fpt_dgst);

    if (state->tls_context == 0) {
	tlsp_state_free(state);
	return (TLSP_STAT_ERR);
    }

    /*
     * XXX Do we care about TLS session rate limits? Good postscreen(8)
     * clients will occasionally require the tlsproxy to renew their
     * allowlist status, but bad clients hammering the server can suck up
     * lots of CPU cycles. Per-client concurrency limits in postscreen(8)
     * will divert only naive security "researchers".
     */
    return (TLSP_STAT_OK);
}

 /*
  * From here on down is low-level code that sets up the plumbing before
  * passing control to the TLS engine above.
  */

/* tlsp_request_read_event - pre-handshake event boiler plate */

static void tlsp_request_read_event(int fd, EVENT_NOTIFY_FN handler,
				            int timeout, void *context)
{
    event_enable_read(fd, handler, context);
    event_request_timer(handler, context, timeout);
}

/* tlsp_accept_event - pre-handshake event boiler plate */

static void tlsp_accept_event(int event, EVENT_NOTIFY_FN handler,
			              void *context)
{
    if (event != EVENT_TIME)
	event_cancel_timer(handler, context);
    else
	errno = ETIMEDOUT;
    /* tlsp_state_free() disables pre-handshake plaintext I/O events. */
}

/* tlsp_get_fd_event - receive final connection hand-off information */

static void tlsp_get_fd_event(int event, void *context)
{
    const char *myname = "tlsp_get_fd_event";
    TLSP_STATE *state = (TLSP_STATE *) context;
    int     plaintext_fd = vstream_fileno(state->plaintext_stream);
    int     status;

    /*
     * At this point we still manually manage plaintext read/write/timeout
     * events. Disable I/O events on the plaintext stream until the TLS
     * handshake is completed. Every code path must either destroy state, or
     * request the next event, otherwise we have a file and memory leak.
     */
    tlsp_accept_event(event, tlsp_get_fd_event, (void *) state);
    event_disable_readwrite(plaintext_fd);

    if (event != EVENT_READ
	|| (state->ciphertext_fd = LOCAL_RECV_FD(plaintext_fd)) < 0) {
	msg_warn("%s: receive remote SMTP peer file descriptor: %m", myname);
	tlsp_state_free(state);
	return;
    }

    /*
     * This is a bit early, to ensure that timer events for this file handle
     * are guaranteed to be turned off by the TLSP_STATE destructor.
     */
    state->ciphertext_timer = tlsp_ciphertext_event;
    non_blocking(state->ciphertext_fd, NON_BLOCKING);

    /*
     * Perform the TLS layer before-handshake initialization. We perform the
     * remainder after the actual TLS handshake completes.
     */
    if (state->is_server_role)
	status = tlsp_server_start_pre_handshake(state);
    else
	status = tlsp_client_start_pre_handshake(state);
    if (status != TLSP_STAT_OK)
	/* At this point, state is a dangling pointer. */
	return;

    /*
     * Trigger the initial proxy server I/Os.
     */
    tlsp_strategy(state);
    /* At this point, state could be a dangling pointer. */
}

/* tlsp_config_diff - report server-client config differences */

static void tlsp_log_config_diff(const char *server_cfg, const char *client_cfg)
{
    VSTRING *diff_summary = vstring_alloc(100);
    char   *saved_server = mystrdup(server_cfg);
    char   *saved_client = mystrdup(client_cfg);
    char   *server_field;
    char   *client_field;
    char   *server_next;
    char   *client_next;

    /*
     * Not using argv_split(), because it would treat multiple consecutive
     * newline characters as one.
     */
    for (server_field = saved_server, client_field = saved_client;
	 server_field && client_field;
	 server_field = server_next, client_field = client_next) {
	server_next = split_at(server_field, '\n');
	client_next = split_at(client_field, '\n');
	if (strcmp(server_field, client_field) != 0) {
	    if (LEN(diff_summary) > 0)
		vstring_sprintf_append(diff_summary, "; ");
	    vstring_sprintf_append(diff_summary,
				   "(server) '%s' != (client) '%s'",
				   server_field, client_field);
	}
    }
    msg_warn("%s", STR(diff_summary));

    vstring_free(diff_summary);
    myfree(saved_client);
    myfree(saved_server);
}

/* tlsp_client_init - initialize a TLS client engine */

static TLS_APPL_STATE *tlsp_client_init(TLS_CLIENT_PARAMS *tls_params,
				          TLS_CLIENT_INIT_PROPS *init_props)
{
    TLS_APPL_STATE *appl_state;
    VSTRING *param_buf;
    char   *param_key;
    VSTRING *init_buf;
    char   *init_key;
    int     log_hints = 0;

    /*
     * Use one TLS_APPL_STATE object for all requests that specify the same
     * TLS_CLIENT_INIT_PROPS. Each TLS_APPL_STATE owns an SSL_CTX, which is
     * expensive to create. Bug: TLS_CLIENT_PARAMS are not used when creating
     * a TLS_APPL_STATE instance.
     * 
     * First, compute the TLS_APPL_STATE cache lookup key. Save a copy of the
     * pre-jail request TLS_CLIENT_PARAMS and TLSPROXY_CLIENT_INIT_PROPS
     * settings, so that we can detect post-jail requests that do not match.
     */
    param_buf = vstring_alloc(100);
    param_key = tls_proxy_client_param_serialize(attr_print_plain, param_buf,
						 tls_params);
    init_buf = vstring_alloc(100);
    init_key = tls_proxy_client_init_serialize(attr_print_plain, init_buf,
					       init_props);
    if (tlsp_pre_jail_done == 0) {
	if (tlsp_pre_jail_client_param_key == 0
	    || tlsp_pre_jail_client_init_key == 0) {
	    tlsp_pre_jail_client_param_key = mystrdup(param_key);
	    tlsp_pre_jail_client_init_key = mystrdup(init_key);
	} else if (strcmp(tlsp_pre_jail_client_param_key, param_key) != 0
		   || strcmp(tlsp_pre_jail_client_init_key, init_key) != 0) {
	    msg_panic("tlsp_client_init: too many pre-jail calls");
	}
    }

    /*
     * Log a warning if a post-jail request uses unexpected TLS_CLIENT_PARAMS
     * settings. Bug: TLS_CLIENT_PARAMS settings are not used when creating a
     * TLS_APPL_STATE instance; this makes a mismatch of TLS_CLIENT_PARAMS
     * settings problematic.
     */
    if (tlsp_pre_jail_done
	&& !been_here_fixed(tlsp_params_mismatch_filter, param_key)
	&& strcmp(tlsp_pre_jail_client_param_key, param_key) != 0) {
	msg_warn("request from tlsproxy client with unexpected settings");
	tlsp_log_config_diff(tlsp_pre_jail_client_param_key, param_key);
	log_hints = 1;
    }

    /*
     * Look up the cached TLS_APPL_STATE for this tls_client_init request.
     */
    if ((appl_state = (TLS_APPL_STATE *)
	 htable_find(tlsp_client_app_cache, init_key)) == 0) {

	/*
	 * Before creating a TLS_APPL_STATE instance, log a warning if a
	 * post-jail request differs from the saved pre-jail request AND the
	 * post-jail request specifies file/directory pathname arguments.
	 * Unexpected requests containing pathnames are problematic after
	 * chroot (pathname resolution) and after dropping privileges (key
	 * files must be root read-only). Unexpected requests are not a
	 * problem as long as they contain no pathnames (for example a
	 * tls_loglevel change).
	 * 
	 * We could eliminate some of this complication by adding code that
	 * opens a cert/key lookup table at pre-jail time, and by reading
	 * cert/key info on-the-fly from that table. But then all requests
	 * would still have to specify the same table.
	 */
#define NOT_EMPTY(x) ((x) && *(x))

	if (tlsp_pre_jail_done
	    && strcmp(tlsp_pre_jail_client_init_key, init_key) != 0
	    && (NOT_EMPTY(init_props->chain_files)
		|| NOT_EMPTY(init_props->cert_file)
		|| NOT_EMPTY(init_props->key_file)
		|| NOT_EMPTY(init_props->dcert_file)
		|| NOT_EMPTY(init_props->dkey_file)
		|| NOT_EMPTY(init_props->eccert_file)
		|| NOT_EMPTY(init_props->eckey_file)
		|| NOT_EMPTY(init_props->CAfile)
		|| NOT_EMPTY(init_props->CApath))) {
	    msg_warn("request from tlsproxy client with unexpected settings");
	    tlsp_log_config_diff(tlsp_pre_jail_client_init_key, init_key);
	    log_hints = 1;
	}
    }
    if (log_hints)
	msg_warn("to avoid this warning, 1) identify the tlsproxy "
		 "client that is making this request, 2) configure "
		 "a custom tlsproxy service with settings that "
		 "match that tlsproxy client, and 3) configure "
		 "that tlsproxy client with a tlsproxy_service_name "
		 "setting that resolves to that custom tlsproxy "
		 "service");

    /*
     * TLS_APPL_STATE creation may fail when a post-jail request specifies
     * unexpected cert/key information, but that is OK because we already
     * logged a warning with configuration suggestions.
     */
    if (appl_state == 0
	&& (appl_state = tls_client_init(init_props)) != 0) {
	(void) htable_enter(tlsp_client_app_cache, init_key,
			    (void *) appl_state);

	/*
	 * To maintain sanity, allow partial SSL_write() operations, and
	 * allow SSL_write() buffer pointers to change after a WANT_READ or
	 * WANT_WRITE result. This is based on OpenSSL developers talking on
	 * a mailing list, but is not supported by documentation. If this
	 * code stops working then no-one can be held responsible.
	 */
	SSL_CTX_set_mode(appl_state->ssl_ctx,
			 SSL_MODE_ENABLE_PARTIAL_WRITE
			 | SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
    }
    vstring_free(init_buf);
    vstring_free(param_buf);
    return (appl_state);
}

/* tlsp_close_event - pre-handshake plaintext-client close event */

static void tlsp_close_event(int event, void *context)
{
    TLSP_STATE *state = (TLSP_STATE *) context;

    tlsp_accept_event(event, tlsp_close_event, (void *) state);
    tlsp_state_free(state);
}

/* tlsp_get_request_event - receive initial hand-off info */

static void tlsp_get_request_event(int event, void *context)
{
    const char *myname = "tlsp_get_request_event";
    TLSP_STATE *state = (TLSP_STATE *) context;
    VSTREAM *plaintext_stream = state->plaintext_stream;
    int     plaintext_fd = vstream_fileno(plaintext_stream);
    static VSTRING *remote_endpt;
    static VSTRING *server_id;
    int     req_flags;
    int     handshake_timeout;
    int     session_timeout;
    int     ready = 0;

    /*
     * At this point we still manually manage plaintext read/write/timeout
     * events. Every code path must either destroy state or request the next
     * event, otherwise this pseudo-thread is idle until the client goes
     * away.
     */
    tlsp_accept_event(event, tlsp_get_request_event, (void *) state);

    /*
     * One-time initialization.
     */
    if (remote_endpt == 0) {
	remote_endpt = vstring_alloc(10);
	server_id = vstring_alloc(10);
    }

    /*
     * Receive the initial request attributes. Receive the remainder after we
     * figure out what role we are expected to play.
     * 
     * The tlsproxy server does not enforce per-request read/write deadlines or
     * minimal data rates. Instead, the tlsproxy server relies on the
     * tlsproxy client to enforce these context-dependent limits. When a
     * tlsproxy client decides to time out, it will close its end of the
     * tlsproxy stream, and the tlsproxy server will handle that immediately.
     */
    if (event != EVENT_READ
	|| attr_scan(plaintext_stream, ATTR_FLAG_STRICT,
		     RECV_ATTR_STR(TLS_ATTR_REMOTE_ENDPT, remote_endpt),
		     RECV_ATTR_INT(TLS_ATTR_FLAGS, &req_flags),
		     RECV_ATTR_INT(TLS_ATTR_TIMEOUT, &handshake_timeout),
		     RECV_ATTR_INT(TLS_ATTR_TIMEOUT, &session_timeout),
		     RECV_ATTR_STR(TLS_ATTR_SERVERID, server_id),
		     ATTR_TYPE_END) != 5) {
	msg_warn("%s: receive request attributes: %m", myname);
	tlsp_state_free(state);
	return;
    }

    /*
     * XXX We use the same fixed timeout throughout the entire session for
     * both plaintext and ciphertext communication. This timeout is just a
     * safety feature; the real timeout will be enforced by our plaintext
     * peer (except during TLS the handshake, when we intentionally disable
     * plaintext I/O).
     */
    state->remote_endpt = mystrdup(STR(remote_endpt));
    state->server_id = mystrdup(STR(server_id));
    msg_info("CONNECT %s %s",
	     (req_flags & TLS_PROXY_FLAG_ROLE_SERVER) ? "from" :
	     (req_flags & TLS_PROXY_FLAG_ROLE_CLIENT) ? "to" :
	     "(bogus_direction)", state->remote_endpt);
    state->req_flags = req_flags;
    /* state->is_server_role is set below. */
    state->handshake_timeout = handshake_timeout;
    state->session_timeout = session_timeout + 10;	/* XXX */

    /*
     * Receive the TLS preferences now, to reduce the number of protocol
     * roundtrips.
     */
    switch (req_flags & (TLS_PROXY_FLAG_ROLE_CLIENT | TLS_PROXY_FLAG_ROLE_SERVER)) {
    case TLS_PROXY_FLAG_ROLE_CLIENT:
	state->is_server_role = 0;
	if (attr_scan(plaintext_stream, ATTR_FLAG_STRICT,
		      RECV_ATTR_FUNC(tls_proxy_client_param_scan,
				     (void *) &state->tls_params),
		      RECV_ATTR_FUNC(tls_proxy_client_init_scan,
				     (void *) &state->client_init_props),
		      RECV_ATTR_FUNC(tls_proxy_client_start_scan,
				     (void *) &state->client_start_props),
		      ATTR_TYPE_END) != 3) {
	    msg_warn("%s: receive client TLS settings: %m", myname);
	    tlsp_state_free(state);
	    return;
	}
	state->appl_state = tlsp_client_init(state->tls_params,
					     state->client_init_props);
	ready = state->appl_state != 0;
	break;
    case TLS_PROXY_FLAG_ROLE_SERVER:
	state->is_server_role = 1;
	ready = (tlsp_server_ctx != 0);
	break;
    default:
	state->is_server_role = 0;
	msg_warn("%s: bad request flags: 0x%x", myname, req_flags);
	ready = 0;
    }

    /*
     * For portability we must send some data, after receiving the request
     * attributes and before receiving the remote file descriptor.
     * 
     * If the requested TLS engine is unavailable, hang up after making sure
     * that the plaintext peer has received our "sorry" indication.
     */
    if (attr_print(plaintext_stream, ATTR_FLAG_NONE,
		   SEND_ATTR_INT(MAIL_ATTR_STATUS, ready),
		   ATTR_TYPE_END) != 0
	|| vstream_fflush(plaintext_stream) != 0
	|| ready == 0) {
	tlsp_request_read_event(plaintext_fd, tlsp_close_event,
				TLSP_INIT_TIMEOUT, (void *) state);
	return;
    } else {
	tlsp_request_read_event(plaintext_fd, tlsp_get_fd_event,
				TLSP_INIT_TIMEOUT, (void *) state);
	return;
    }
}

/* tlsp_service - handle new client connection */

static void tlsp_service(VSTREAM *plaintext_stream,
			         char *service,
			         char **argv)
{
    TLSP_STATE *state;
    int     plaintext_fd = vstream_fileno(plaintext_stream);

    /*
     * Sanity check. This service takes no command-line arguments.
     */
    if (argv[0])
	msg_fatal("unexpected command-line argument: %s", argv[0]);

    /*
     * This program handles multiple connections, so it must not block. We
     * use event-driven code for all operations that introduce latency.
     * Except that attribute lists are sent/received synchronously, once the
     * socket is found to be ready for transmission.
     */
    non_blocking(plaintext_fd, NON_BLOCKING);
    vstream_control(plaintext_stream,
		    CA_VSTREAM_CTL_PATH("plaintext"),
		    CA_VSTREAM_CTL_TIMEOUT(5),
		    CA_VSTREAM_CTL_END);

    (void) attr_print(plaintext_stream, ATTR_FLAG_NONE,
		   SEND_ATTR_STR(MAIL_ATTR_PROTO, MAIL_ATTR_PROTO_TLSPROXY),
		      ATTR_TYPE_END);
    if (vstream_fflush(plaintext_stream) != 0)
	msg_warn("write %s attribute: %m", MAIL_ATTR_PROTO);

    /*
     * Receive postscreen's remote SMTP client address/port and socket.
     */
    state = tlsp_state_create(service, plaintext_stream);
    tlsp_request_read_event(plaintext_fd, tlsp_get_request_event,
			    TLSP_INIT_TIMEOUT, (void *) state);
}

/* pre_jail_init_server - pre-jail initialization */

static void pre_jail_init_server(void)
{
    TLS_SERVER_INIT_PROPS props;
    const char *cert_file;
    int     have_server_cert;
    int     no_server_cert_ok;
    int     require_server_cert;

    /*
     * The code in this routine is pasted literally from smtpd(8). I am not
     * going to sanitize this because doing so surely will break things in
     * unexpected ways.
     */
    if (*var_tlsp_tls_level) {
	switch (tls_level_lookup(var_tlsp_tls_level)) {
	default:
	    msg_fatal("Invalid TLS level \"%s\"", var_tlsp_tls_level);
	    /* NOTREACHED */
	    break;
	case TLS_LEV_SECURE:
	case TLS_LEV_VERIFY:
	case TLS_LEV_FPRINT:
	    msg_warn("%s: unsupported TLS level \"%s\", using \"encrypt\"",
		     VAR_TLSP_TLS_LEVEL, var_tlsp_tls_level);
	    /* FALLTHROUGH */
	case TLS_LEV_ENCRYPT:
	    var_tlsp_enforce_tls = var_tlsp_use_tls = 1;
	    break;
	case TLS_LEV_MAY:
	    var_tlsp_enforce_tls = 0;
	    var_tlsp_use_tls = 1;
	    break;
	case TLS_LEV_NONE:
	    var_tlsp_enforce_tls = var_tlsp_use_tls = 0;
	    break;
	}
    }
    var_tlsp_use_tls = var_tlsp_use_tls || var_tlsp_enforce_tls;
    if (!var_tlsp_use_tls) {
	msg_warn("TLS server role is disabled with %s or %s",
		 VAR_TLSP_TLS_LEVEL, VAR_TLSP_USE_TLS);
	return;
    }

    /*
     * Load TLS keys before dropping privileges.
     * 
     * Can't use anonymous ciphers if we want client certificates. Must use
     * anonymous ciphers if we have no certificates.
     */
    ask_client_cert = require_server_cert =
	(var_tlsp_tls_ask_ccert
	 || (var_tlsp_enforce_tls && var_tlsp_tls_req_ccert));
    if (strcasecmp(var_tlsp_tls_cert_file, "none") == 0) {
	no_server_cert_ok = 1;
	cert_file = "";
    } else {
	no_server_cert_ok = 0;
	cert_file = var_tlsp_tls_cert_file;
    }
    have_server_cert =
	(*cert_file || *var_tlsp_tls_dcert_file || *var_tlsp_tls_eccert_file);

    if (*var_tlsp_tls_chain_files != 0) {
	if (!have_server_cert)
	    have_server_cert = 1;
	else
	    msg_warn("Both %s and one or more of the legacy "
		     " %s, %s or %s are non-empty; the legacy "
		     " parameters will be ignored",
		     VAR_TLSP_TLS_CHAIN_FILES,
		     VAR_TLSP_TLS_CERT_FILE,
		     VAR_TLSP_TLS_ECCERT_FILE,
		     VAR_TLSP_TLS_DCERT_FILE);
    }
    /* Some TLS configuration errors are not show stoppers. */
    if (!have_server_cert && require_server_cert)
	msg_warn("Need a server cert to request client certs");
    if (!var_tlsp_enforce_tls && var_tlsp_tls_req_ccert)
	msg_warn("Can't require client certs unless TLS is required");
    /* After a show-stopper error, log a warning. */
    if (have_server_cert || (no_server_cert_ok && !require_server_cert)) {

	tls_pre_jail_init(TLS_ROLE_SERVER);

	/*
	 * Large parameter lists are error-prone, so we emulate a language
	 * feature that C does not have natively: named parameter lists.
	 */
	tlsp_server_ctx =
	    TLS_SERVER_INIT(&props,
			    log_param = VAR_TLSP_TLS_LOGLEVEL,
			    log_level = var_tlsp_tls_loglevel,
			    verifydepth = var_tlsp_tls_ccert_vd,
			    cache_type = TLS_MGR_SCACHE_SMTPD,
			    set_sessid = var_tlsp_tls_set_sessid,
			    chain_files = var_tlsp_tls_chain_files,
			    cert_file = cert_file,
			    key_file = var_tlsp_tls_key_file,
			    dcert_file = var_tlsp_tls_dcert_file,
			    dkey_file = var_tlsp_tls_dkey_file,
			    eccert_file = var_tlsp_tls_eccert_file,
			    eckey_file = var_tlsp_tls_eckey_file,
			    CAfile = var_tlsp_tls_CAfile,
			    CApath = var_tlsp_tls_CApath,
			    dh1024_param_file
			    = var_tlsp_tls_dh1024_param_file,
			    dh512_param_file
			    = var_tlsp_tls_dh512_param_file,
			    eecdh_grade = var_tlsp_tls_eecdh,
			    protocols = var_tlsp_enforce_tls ?
			    var_tlsp_tls_mand_proto :
			    var_tlsp_tls_proto,
			    ask_ccert = ask_client_cert,
			    mdalg = var_tlsp_tls_fpt_dgst);
    } else {
	msg_warn("No server certs available. TLS can't be enabled");
    }

    /*
     * To maintain sanity, allow partial SSL_write() operations, and allow
     * SSL_write() buffer pointers to change after a WANT_READ or WANT_WRITE
     * result. This is based on OpenSSL developers talking on a mailing list,
     * but is not supported by documentation. If this code stops working then
     * no-one can be held responsible.
     */
    if (tlsp_server_ctx)
	SSL_CTX_set_mode(tlsp_server_ctx->ssl_ctx,
			 SSL_MODE_ENABLE_PARTIAL_WRITE
			 | SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
}

/* pre_jail_init_client - pre-jail initialization */

static void pre_jail_init_client(void)
{
    int     clnt_use_tls;

    /*
     * The cache with TLS_APPL_STATE instances for different TLS_CLIENT_INIT
     * configurations.
     */
    tlsp_client_app_cache = htable_create(10);

    /*
     * Most sites don't use TLS client certs/keys. In that case, enabling
     * tlsproxy-based connection caching is trivial.
     * 
     * But some sites do use TLS client certs/keys, and that is challenging when
     * tlsproxy runs in a post-jail environment: chroot breaks pathname
     * resolution, and an unprivileged process should not be able to open
     * files with secrets. The workaround: assume that most of those sites
     * will use a fixed TLS client identity. In that case, tlsproxy can load
     * the corresponding certs/keys at pre-jail time, so that secrets can
     * remain read-only for root. As long as the tlsproxy pre-jail TLS client
     * configuration with cert or key pathnames is the same as the one used
     * in the Postfix SMTP client, sites can selectively or globally enable
     * tlsproxy-based connection caching without additional TLS
     * configuration.
     * 
     * Loading one TLS client configuration at pre-jail time is not sufficient
     * for the minority of sites that want to use TLS connection caching with
     * multiple TLS client identities. To alert the operator, tlsproxy will
     * log a warning when a TLS_CLIENT_INIT message specifies a different
     * configuration than the tlsproxy pre-jail client configuration, and
     * that different configuration specifies file/directory pathname
     * arguments. The workaround is to have one tlsproxy process per TLS
     * client identity.
     * 
     * The general solution for single-identity or multi-identity clients is to
     * stop loading certs and keys from individual files. Instead, have a
     * cert/key map, indexed by client identity, read-only by root. After
     * opening the map as root at pre-jail time, tlsproxy can read certs/keys
     * on-the-fly as an unprivileged process at post-jail time. This is the
     * approach that was already proposed for server-side SNI support, and it
     * could be reused here. It would also end the proliferation of RSA
     * cert/key parameters, DSA cert/key parameters, EC cert/key parameters,
     * and so on.
     * 
     * Horror: In order to create the same pre-jail TLS client context as the
     * one used in the Postfix SMTP client, we have to duplicate intricate
     * SMTP client code, including a handful configuration parameters that
     * tlsproxy does not need. We must duplicate the logic, so that we only
     * load certs and keys when the SMTP client would load them.
     */
    if (*var_tlsp_clnt_level != 0)
	switch (tls_level_lookup(var_tlsp_clnt_level)) {
	case TLS_LEV_SECURE:
	case TLS_LEV_VERIFY:
	case TLS_LEV_DANE_ONLY:
	case TLS_LEV_FPRINT:
	case TLS_LEV_ENCRYPT:
	    var_tlsp_clnt_use_tls = var_tlsp_clnt_enforce_tls = 1;
	    break;
	case TLS_LEV_DANE:
	case TLS_LEV_MAY:
	    var_tlsp_clnt_use_tls = 1;
	    var_tlsp_clnt_enforce_tls = 0;
	    break;
	case TLS_LEV_NONE:
	    var_tlsp_clnt_use_tls = var_tlsp_clnt_enforce_tls = 0;
	    break;
	default:
	    /* tls_level_lookup() logs no warning. */
	    /* session_tls_init() assumes that var_tlsp_clnt_level is sane. */
	    msg_fatal("Invalid TLS level \"%s\"", var_tlsp_clnt_level);
	}
    clnt_use_tls = (var_tlsp_clnt_use_tls || var_tlsp_clnt_enforce_tls);

    /*
     * Initialize the TLS data before entering the chroot jail.
     */
    if (clnt_use_tls || var_tlsp_clnt_per_site[0] || var_tlsp_clnt_policy[0]) {
	TLS_CLIENT_PARAMS tls_params;
	TLS_CLIENT_INIT_PROPS init_props;

	tls_pre_jail_init(TLS_ROLE_CLIENT);

	/*
	 * We get stronger type safety and a cleaner interface by combining
	 * the various parameters into a single tls_client_props structure.
	 * 
	 * Large parameter lists are error-prone, so we emulate a language
	 * feature that C does not have natively: named parameter lists.
	 */
	(void) tls_proxy_client_param_from_config(&tls_params);
	(void) TLS_CLIENT_INIT_ARGS(&init_props,
				    log_param = var_tlsp_clnt_logparam,
				    log_level = var_tlsp_clnt_loglevel,
				    verifydepth = var_tlsp_clnt_scert_vd,
				    cache_type = TLS_MGR_SCACHE_SMTP,
				    chain_files = var_tlsp_clnt_chain_files,
				    cert_file = var_tlsp_clnt_cert_file,
				    key_file = var_tlsp_clnt_key_file,
				    dcert_file = var_tlsp_clnt_dcert_file,
				    dkey_file = var_tlsp_clnt_dkey_file,
				    eccert_file = var_tlsp_clnt_eccert_file,
				    eckey_file = var_tlsp_clnt_eckey_file,
				    CAfile = var_tlsp_clnt_CAfile,
				    CApath = var_tlsp_clnt_CApath,
				    mdalg = var_tlsp_clnt_fpt_dgst);
	if (tlsp_client_init(&tls_params, &init_props) == 0)
	    msg_warn("TLS client initialization failed");
    }
}

/* pre_jail_init - pre-jail initialization */

static void pre_jail_init(char *unused_name, char **unused_argv)
{

    /*
     * Initialize roles separately.
     */
    pre_jail_init_server();
    pre_jail_init_client();

    /*
     * tlsp_client_init() needs to know if it is called pre-jail or
     * post-jail.
     */
    tlsp_pre_jail_done = 1;

    /*
     * Bug: TLS_CLIENT_PARAMS attributes are not used when creating a
     * TLS_APPL_STATE instance; we can only warn about attribute mismatches.
     */
    tlsp_params_mismatch_filter = been_here_init(BH_BOUND_NONE, BH_FLAG_NONE);
}

MAIL_VERSION_STAMP_DECLARE;

/* main - the main program */

int     main(int argc, char **argv)
{

    /*
     * Each table below initializes the named variables to their implicit
     * default value, or to the explicit value in main.cf or master.cf. Here,
     * "compat" means that a table initializes a variable "smtpd_blah" or
     * "smtp_blah" that provides the implicit default value for variable
     * "tlsproxy_blah" which is initialized by a different table. To make
     * this work, the variables in a "compat" table must be initialized
     * before the variables in the corresponding non-compat table.
     */
    static const CONFIG_INT_TABLE compat_int_table[] = {
	VAR_SMTPD_TLS_CCERT_VD, DEF_SMTPD_TLS_CCERT_VD, &var_smtpd_tls_ccert_vd, 0, 0,
	VAR_SMTP_TLS_SCERT_VD, DEF_SMTP_TLS_SCERT_VD, &var_smtp_tls_scert_vd, 0, 0,
	0,
    };
    static const CONFIG_NINT_TABLE nint_table[] = {
	VAR_TLSP_TLS_CCERT_VD, DEF_TLSP_TLS_CCERT_VD, &var_tlsp_tls_ccert_vd, 0, 0,
	VAR_TLSP_CLNT_SCERT_VD, DEF_TLSP_CLNT_SCERT_VD, &var_tlsp_clnt_scert_vd, 0, 0,
	0,
    };
    static const CONFIG_TIME_TABLE time_table[] = {
	VAR_TLSP_WATCHDOG, DEF_TLSP_WATCHDOG, &var_tlsp_watchdog, 10, 0,
	0,
    };
    static const CONFIG_BOOL_TABLE compat_bool_table[] = {
	VAR_SMTPD_USE_TLS, DEF_SMTPD_USE_TLS, &var_smtpd_use_tls,
	VAR_SMTPD_ENFORCE_TLS, DEF_SMTPD_ENFORCE_TLS, &var_smtpd_enforce_tls,
	VAR_SMTPD_TLS_ACERT, DEF_SMTPD_TLS_ACERT, &var_smtpd_tls_ask_ccert,
	VAR_SMTPD_TLS_RCERT, DEF_SMTPD_TLS_RCERT, &var_smtpd_tls_req_ccert,
	VAR_SMTPD_TLS_SET_SESSID, DEF_SMTPD_TLS_SET_SESSID, &var_smtpd_tls_set_sessid,
	VAR_SMTP_USE_TLS, DEF_SMTP_USE_TLS, &var_smtp_use_tls,
	VAR_SMTP_ENFORCE_TLS, DEF_SMTP_ENFORCE_TLS, &var_smtp_enforce_tls,
	0,
    };
    static const CONFIG_NBOOL_TABLE nbool_table[] = {
	VAR_TLSP_USE_TLS, DEF_TLSP_USE_TLS, &var_tlsp_use_tls,
	VAR_TLSP_ENFORCE_TLS, DEF_TLSP_ENFORCE_TLS, &var_tlsp_enforce_tls,
	VAR_TLSP_TLS_ACERT, DEF_TLSP_TLS_ACERT, &var_tlsp_tls_ask_ccert,
	VAR_TLSP_TLS_RCERT, DEF_TLSP_TLS_RCERT, &var_tlsp_tls_req_ccert,
	VAR_TLSP_TLS_SET_SESSID, DEF_TLSP_TLS_SET_SESSID, &var_tlsp_tls_set_sessid,
	VAR_TLSP_CLNT_USE_TLS, DEF_TLSP_CLNT_USE_TLS, &var_tlsp_clnt_use_tls,
	VAR_TLSP_CLNT_ENFORCE_TLS, DEF_TLSP_CLNT_ENFORCE_TLS, &var_tlsp_clnt_enforce_tls,
	0,
    };
    static const CONFIG_STR_TABLE compat_str_table[] = {
	VAR_SMTPD_TLS_CHAIN_FILES, DEF_SMTPD_TLS_CHAIN_FILES, &var_smtpd_tls_chain_files, 0, 0,
	VAR_SMTPD_TLS_CERT_FILE, DEF_SMTPD_TLS_CERT_FILE, &var_smtpd_tls_cert_file, 0, 0,
	VAR_SMTPD_TLS_KEY_FILE, DEF_SMTPD_TLS_KEY_FILE, &var_smtpd_tls_key_file, 0, 0,
	VAR_SMTPD_TLS_DCERT_FILE, DEF_SMTPD_TLS_DCERT_FILE, &var_smtpd_tls_dcert_file, 0, 0,
	VAR_SMTPD_TLS_DKEY_FILE, DEF_SMTPD_TLS_DKEY_FILE, &var_smtpd_tls_dkey_file, 0, 0,
	VAR_SMTPD_TLS_ECCERT_FILE, DEF_SMTPD_TLS_ECCERT_FILE, &var_smtpd_tls_eccert_file, 0, 0,
	VAR_SMTPD_TLS_ECKEY_FILE, DEF_SMTPD_TLS_ECKEY_FILE, &var_smtpd_tls_eckey_file, 0, 0,
	VAR_SMTPD_TLS_CA_FILE, DEF_SMTPD_TLS_CA_FILE, &var_smtpd_tls_CAfile, 0, 0,
	VAR_SMTPD_TLS_CA_PATH, DEF_SMTPD_TLS_CA_PATH, &var_smtpd_tls_CApath, 0, 0,
	VAR_SMTPD_TLS_CIPH, DEF_SMTPD_TLS_CIPH, &var_smtpd_tls_ciph, 1, 0,
	VAR_SMTPD_TLS_MAND_CIPH, DEF_SMTPD_TLS_MAND_CIPH, &var_smtpd_tls_mand_ciph, 1, 0,
	VAR_SMTPD_TLS_EXCL_CIPH, DEF_SMTPD_TLS_EXCL_CIPH, &var_smtpd_tls_excl_ciph, 0, 0,
	VAR_SMTPD_TLS_MAND_EXCL, DEF_SMTPD_TLS_MAND_EXCL, &var_smtpd_tls_mand_excl, 0, 0,
	VAR_SMTPD_TLS_PROTO, DEF_SMTPD_TLS_PROTO, &var_smtpd_tls_proto, 0, 0,
	VAR_SMTPD_TLS_MAND_PROTO, DEF_SMTPD_TLS_MAND_PROTO, &var_smtpd_tls_mand_proto, 0, 0,
	VAR_SMTPD_TLS_512_FILE, DEF_SMTPD_TLS_512_FILE, &var_smtpd_tls_dh512_param_file, 0, 0,
	VAR_SMTPD_TLS_1024_FILE, DEF_SMTPD_TLS_1024_FILE, &var_smtpd_tls_dh1024_param_file, 0, 0,
	VAR_SMTPD_TLS_EECDH, DEF_SMTPD_TLS_EECDH, &var_smtpd_tls_eecdh, 1, 0,
	VAR_SMTPD_TLS_FPT_DGST, DEF_SMTPD_TLS_FPT_DGST, &var_smtpd_tls_fpt_dgst, 1, 0,
	VAR_SMTPD_TLS_LOGLEVEL, DEF_SMTPD_TLS_LOGLEVEL, &var_smtpd_tls_loglevel, 0, 0,
	VAR_SMTPD_TLS_LEVEL, DEF_SMTPD_TLS_LEVEL, &var_smtpd_tls_level, 0, 0,
	VAR_SMTP_TLS_CHAIN_FILES, DEF_SMTP_TLS_CHAIN_FILES, &var_smtp_tls_chain_files, 0, 0,
	VAR_SMTP_TLS_CERT_FILE, DEF_SMTP_TLS_CERT_FILE, &var_smtp_tls_cert_file, 0, 0,
	VAR_SMTP_TLS_KEY_FILE, DEF_SMTP_TLS_KEY_FILE, &var_smtp_tls_key_file, 0, 0,
	VAR_SMTP_TLS_DCERT_FILE, DEF_SMTP_TLS_DCERT_FILE, &var_smtp_tls_dcert_file, 0, 0,
	VAR_SMTP_TLS_DKEY_FILE, DEF_SMTP_TLS_DKEY_FILE, &var_smtp_tls_dkey_file, 0, 0,
	VAR_SMTP_TLS_CA_FILE, DEF_SMTP_TLS_CA_FILE, &var_smtp_tls_CAfile, 0, 0,
	VAR_SMTP_TLS_CA_PATH, DEF_SMTP_TLS_CA_PATH, &var_smtp_tls_CApath, 0, 0,
	VAR_SMTP_TLS_FPT_DGST, DEF_SMTP_TLS_FPT_DGST, &var_smtp_tls_fpt_dgst, 1, 0,
	VAR_SMTP_TLS_ECCERT_FILE, DEF_SMTP_TLS_ECCERT_FILE, &var_smtp_tls_eccert_file, 0, 0,
	VAR_SMTP_TLS_ECKEY_FILE, DEF_SMTP_TLS_ECKEY_FILE, &var_smtp_tls_eckey_file, 0, 0,
	VAR_SMTP_TLS_LOGLEVEL, DEF_SMTP_TLS_LOGLEVEL, &var_smtp_tls_loglevel, 0, 0,
	VAR_SMTP_TLS_PER_SITE, DEF_SMTP_TLS_PER_SITE, &var_smtp_tls_per_site, 0, 0,
	VAR_SMTP_TLS_LEVEL, DEF_SMTP_TLS_LEVEL, &var_smtp_tls_level, 0, 0,
	VAR_SMTP_TLS_POLICY, DEF_SMTP_TLS_POLICY, &var_smtp_tls_policy, 0, 0,
	0,
    };
    static const CONFIG_STR_TABLE str_table[] = {
	VAR_TLSP_TLS_CHAIN_FILES, DEF_TLSP_TLS_CHAIN_FILES, &var_tlsp_tls_chain_files, 0, 0,
	VAR_TLSP_TLS_CERT_FILE, DEF_TLSP_TLS_CERT_FILE, &var_tlsp_tls_cert_file, 0, 0,
	VAR_TLSP_TLS_KEY_FILE, DEF_TLSP_TLS_KEY_FILE, &var_tlsp_tls_key_file, 0, 0,
	VAR_TLSP_TLS_DCERT_FILE, DEF_TLSP_TLS_DCERT_FILE, &var_tlsp_tls_dcert_file, 0, 0,
	VAR_TLSP_TLS_DKEY_FILE, DEF_TLSP_TLS_DKEY_FILE, &var_tlsp_tls_dkey_file, 0, 0,
	VAR_TLSP_TLS_ECCERT_FILE, DEF_TLSP_TLS_ECCERT_FILE, &var_tlsp_tls_eccert_file, 0, 0,
	VAR_TLSP_TLS_ECKEY_FILE, DEF_TLSP_TLS_ECKEY_FILE, &var_tlsp_tls_eckey_file, 0, 0,
	VAR_TLSP_TLS_CA_FILE, DEF_TLSP_TLS_CA_FILE, &var_tlsp_tls_CAfile, 0, 0,
	VAR_TLSP_TLS_CA_PATH, DEF_TLSP_TLS_CA_PATH, &var_tlsp_tls_CApath, 0, 0,
	VAR_TLSP_TLS_CIPH, DEF_TLSP_TLS_CIPH, &var_tlsp_tls_ciph, 1, 0,
	VAR_TLSP_TLS_MAND_CIPH, DEF_TLSP_TLS_MAND_CIPH, &var_tlsp_tls_mand_ciph, 1, 0,
	VAR_TLSP_TLS_EXCL_CIPH, DEF_TLSP_TLS_EXCL_CIPH, &var_tlsp_tls_excl_ciph, 0, 0,
	VAR_TLSP_TLS_MAND_EXCL, DEF_TLSP_TLS_MAND_EXCL, &var_tlsp_tls_mand_excl, 0, 0,
	VAR_TLSP_TLS_PROTO, DEF_TLSP_TLS_PROTO, &var_tlsp_tls_proto, 0, 0,
	VAR_TLSP_TLS_MAND_PROTO, DEF_TLSP_TLS_MAND_PROTO, &var_tlsp_tls_mand_proto, 0, 0,
	VAR_TLSP_TLS_512_FILE, DEF_TLSP_TLS_512_FILE, &var_tlsp_tls_dh512_param_file, 0, 0,
	VAR_TLSP_TLS_1024_FILE, DEF_TLSP_TLS_1024_FILE, &var_tlsp_tls_dh1024_param_file, 0, 0,
	VAR_TLSP_TLS_EECDH, DEF_TLSP_TLS_EECDH, &var_tlsp_tls_eecdh, 1, 0,
	VAR_TLSP_TLS_FPT_DGST, DEF_TLSP_TLS_FPT_DGST, &var_tlsp_tls_fpt_dgst, 1, 0,
	VAR_TLSP_TLS_LOGLEVEL, DEF_TLSP_TLS_LOGLEVEL, &var_tlsp_tls_loglevel, 0, 0,
	VAR_TLSP_TLS_LEVEL, DEF_TLSP_TLS_LEVEL, &var_tlsp_tls_level, 0, 0,
	VAR_TLSP_CLNT_LOGLEVEL, DEF_TLSP_CLNT_LOGLEVEL, &var_tlsp_clnt_loglevel, 0, 0,
	VAR_TLSP_CLNT_LOGPARAM, DEF_TLSP_CLNT_LOGPARAM, &var_tlsp_clnt_logparam, 0, 0,
	VAR_TLSP_CLNT_CHAIN_FILES, DEF_TLSP_CLNT_CHAIN_FILES, &var_tlsp_clnt_chain_files, 0, 0,
	VAR_TLSP_CLNT_CERT_FILE, DEF_TLSP_CLNT_CERT_FILE, &var_tlsp_clnt_cert_file, 0, 0,
	VAR_TLSP_CLNT_KEY_FILE, DEF_TLSP_CLNT_KEY_FILE, &var_tlsp_clnt_key_file, 0, 0,
	VAR_TLSP_CLNT_DCERT_FILE, DEF_TLSP_CLNT_DCERT_FILE, &var_tlsp_clnt_dcert_file, 0, 0,
	VAR_TLSP_CLNT_DKEY_FILE, DEF_TLSP_CLNT_DKEY_FILE, &var_tlsp_clnt_dkey_file, 0, 0,
	VAR_TLSP_CLNT_ECCERT_FILE, DEF_TLSP_CLNT_ECCERT_FILE, &var_tlsp_clnt_eccert_file, 0, 0,
	VAR_TLSP_CLNT_ECKEY_FILE, DEF_TLSP_CLNT_ECKEY_FILE, &var_tlsp_clnt_eckey_file, 0, 0,
	VAR_TLSP_CLNT_CAFILE, DEF_TLSP_CLNT_CAFILE, &var_tlsp_clnt_CAfile, 0, 0,
	VAR_TLSP_CLNT_CAPATH, DEF_TLSP_CLNT_CAPATH, &var_tlsp_clnt_CApath, 0, 0,
	VAR_TLSP_CLNT_FPT_DGST, DEF_TLSP_CLNT_FPT_DGST, &var_tlsp_clnt_fpt_dgst, 1, 0,
	VAR_TLSP_CLNT_LEVEL, DEF_TLSP_CLNT_LEVEL, &var_tlsp_clnt_level, 0, 0,
	VAR_TLSP_CLNT_PER_SITE, DEF_TLSP_CLNT_PER_SITE, &var_tlsp_clnt_per_site, 0, 0,
	VAR_TLSP_CLNT_POLICY, DEF_TLSP_CLNT_POLICY, &var_tlsp_clnt_policy, 0, 0,
	0,
    };

    /*
     * Fingerprint executables and core dumps.
     */
    MAIL_VERSION_STAMP_ALLOCATE;

    /*
     * Pass control to the event-driven service skeleton.
     */
    event_server_main(argc, argv, tlsp_service,
		      CA_MAIL_SERVER_INT_TABLE(compat_int_table),
		      CA_MAIL_SERVER_NINT_TABLE(nint_table),
		      CA_MAIL_SERVER_STR_TABLE(compat_str_table),
		      CA_MAIL_SERVER_STR_TABLE(str_table),
		      CA_MAIL_SERVER_BOOL_TABLE(compat_bool_table),
		      CA_MAIL_SERVER_NBOOL_TABLE(nbool_table),
		      CA_MAIL_SERVER_TIME_TABLE(time_table),
		      CA_MAIL_SERVER_PRE_INIT(pre_jail_init),
		      CA_MAIL_SERVER_SLOW_EXIT(tlsp_drain),
		      CA_MAIL_SERVER_RETIRE_ME,
		      CA_MAIL_SERVER_WATCHDOG(&var_tlsp_watchdog),
		      CA_MAIL_SERVER_UNLIMITED,
		      0);
}

#else

/* tlsp_service - respond to external trigger(s), non-TLS version */

static void tlsp_service(VSTREAM *stream, char *unused_service,
			         char **unused_argv)
{
    msg_info("TLS support is not compiled in -- exiting");
    event_server_disconnect(stream);
}

/* main - the main program */

int     main(int argc, char **argv)
{

    /*
     * We can't simply use msg_fatal() here, because the logging hasn't been
     * initialized. The text would disappear because stderr is redirected to
     * /dev/null.
     * 
     * We invoke event_server_main() to complete program initialization
     * (including logging) and then invoke the tlsp_service() routine to log
     * the message that says why this program will not run.
     */
    event_server_main(argc, argv, tlsp_service,
		      0);
}

#endif