COURIERTLS(1) Double Precision, Inc. COURIERTLS(1) NAME couriertls - the Courier mail server TLS/SSL protocol wrapper SYNOPSIS couriertls [option...] {program} {arg...} DESCRIPTION The couriertls program is used by applications to encrypt a network connec- tion using SSL/TLS, without having the application deal with the gory de- tails of SSL/TLS. couriertls is used by the Courier mail server IMAP and ESMTP servers. couriertls is not usually run directly from the commandline. An application typically creates a network connection, then runs couriertls with appropri- ate options to encrypt the network connection with SSL/TLS. OPTIONS -host=host, -port=port These options are used instead of -remotefd, mostly for debugging pur- poses. couriertls connects to the specified server and immediately starts SSL/TLS negotation when the connection is established. -localfd=n Read and write data to encrypt via SSL/TLS from file descriptor n. -statusfd=n Write SSL negotiation status to file descriptor n, then close this file descriptor. If SSL starts succesfully, reading on n gets an immediate EOF. Otherwise, a single line of text - the error message - is read; the file descriptor is closed; and couriertls terminates. -printx509=n Print the x509 certificate on file descriptor n then close it. The x509 certificate is printed before SSL/TLS encryption starts. The applica- tion may immediately read the certificate after running couriertls, un- til the file descriptor is closed. -remotefd=n File descriptor n is the network connection where SSL/TLS encryption is to be used. -server Negotiate server side of the SSL/TLS connection. If this option is not used the client side of the SSL/TLS connection is negotiated. -tcpd couriertls is being called from couriertcpd, and the remote socket is present on descriptors 0 and 1. -tcpd means, basically, the same as -remotefd=0, but couriertls closes file descriptor 1, and redirects file descriptor 1 to file descriptor 2. -user=username Used when couriertls needs to get started as root and fork off a root child process (see below), before dropping root and running as the specified user. -verify=domain Verify that domain is set in the CN field of the trusted X.509 certifi- cate presented by the SSL/TLS peer. TLS_TRUSTCERTS must be initialized (see below), and the certificate must be signed by one of the trusted certificates. The CN field can contain a wildcard: CN=*.example will match -verify=foo.example.com. For SSL/TLS clients, TLS_VERIFYPEER must be set to PEER (see below). -protocol=proto Send proto protocol commands before enabling SSL/TLS on the remote con- nection. proto is either "smtp" or "imap". This is a debugging option that can be used to troubleshoot SSL/TLS with a remote IMAP or SMTP server. If the -remotefd=n option is not specified, the rest of the command line specifies the program to run -- and its arguments -- whose standard input and output is encrypted via SSL/TLS over the network connection. This is done before the -user option drops root and couriertls continues to run as the indicated user. If the program is not specified, the standard input and output of couriertls itself is encrypted. ENVIRONMENT VARIABLES couriertls reads the following environment variables in order to configure the SSL/TLS protocol: TLS_PROTOCOL=proto Set the protocol version. The possible versions are: SSL2, SSL3, TLS1. TLS_CIPHER_LIST=cipherlist Optionally set the list of protocol ciphers to be used. See OpenSSL's documentation for more information. TLS_TIMEOUT=seconds Currently not implemented, and reserved for future use. This is sup- posed to be an inactivity timeout, but it's not yet implemented. TLS_DHCERTFILE=filename PEM file that stores our Diffie-Hellman cipher pair. When OpenSSL is compiled to use Diffie-Hellman ciphers instead of RSA you must generate a DH pair that will be used. In most situations the DH pair is to be treated as confidential, and filename must not be world-readable. TLS_CERTFILE=filename The certificate to use. TLS_CERTFILE is required for SSL/TLS servers, and is optional for SSL/TLS clients. filename must not be world-read- able. TLS_PRIVATE_KEYFILE=filename SSL/TLS private key for decrypting client data. TLS_PRIVATE_KEY is op- tional because <term>TLS_CERTFILE</term> is generated including cert and private key both. filename must not be world-readable, and must be accessible without a pass-phrase, i.e. it must not be encrypted. TLS_TRUSTCERTS=pathname Load trusted root certificates from pathname. pathname can be a file or a directory. If a file, the file should contain a list of trusted certificates, in PEM format. If a directory, the directory should con- tain the trusted certificates, in PEM format, one per file and hashed using OpenSSL's c_rehash script. TLS_TRUSTCERTS is used by SSL/TLS clients (by specifying the -domain option) and by SSL/TLS servers (TLS_VERIFYPEER is set to PEER or REQUIREPEER). TLS_VERIFYPEER=level Whether to verify peer's X.509 certificate. The exact meaning of this option depends upon whether couriertls is used in the client or server mode. In server mode: NONE - do not request an X.509 certificate from the client; PEER - request an optional X.509 certificate from the client, if the client returns one, the SSL/TLS connection is shut down unless the certificate is signed by a trusted certificate authority (see TLS_TRUSTCERTS); REQUIREPEER - same as PEER, except that the SSL/TLS connects is also shut down if the client does not return the optional X.509 certificate. In client mode: NONE - ignore the server's X.509 certificate; PEER - verify the server's X.509 certificate accord- ing to the -domain option, (see above). SEE ALSO couriertcpd(1)[1], courier(8)[2]. AUTHOR Sam Varshavchik Author NOTES 1. couriertcpd(1) http://www.courier-mta.org/couriertcpd.html 2. courier(8) http://www.courier-mta.org/courier.html Courier Mail Server 06/10/2024 COURIERTLS(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT VARIABLES | SEE ALSO | AUTHOR | NOTES
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