sslserver - accept TLS connections and setup SSL CTX
sslserver [ opts ] host port prog
opts is a series of getopt-style options, host is a host name or IP
address, port is a TCP port, and prog is one or more arguments
specifying a program to run for each accepted connection.
The server's address is given by host and port.
sslserver will be attached to the primary IP address of host while the
host name is fed through qualification using dns_ip6_qualify. If host
is given as dotted decimal IPv4 or compactified IPv6 address, sslserver
will bind uniquely to those. In order to bind sslserver to a LLU IPv6
address (ie. fe80::a:b:c) additionally the interface name -Iifname has
to be provided.
Note: The kernel might use temporary changing SLAAC addresses.
sslserver can be instructed to be multi-homing capable while binding to
all available IP addresses. Now host is given as '0' or '::' perhaps
accompanied by the flags -4 or -6.
Further, sslserver can be forced to provide dual-stack capabilities,
thus allowing IPv4 and IPv6 clients to attach to the same instance once
host equals ':0' as pseudo IP address.
port may be a numeric port number or a port name. If port is 0,
sslserver will choose a free port.
sslserver listens for connections from TCP clients. Typically, for
each connection, it runs prog, with file descriptor 0 reading from, and
file descriptor 1 writing to a child process ssl. If however sslserver
is called with the option -n, it communcates with prog on mutually
chosen, arbitrary file descriptors. prog needs to support the UCSPI-
TLS API. The ssl process attempts an SSL accept via the network. If
it succeeds, it translates data between prog and the network,
performing any necessary SSL encoding and decoding. Before running
prog, sslserver reads and sets certain environment variables.
sslserver exits when it receives SIGTERM.
-q Quiet. Do not print error messages.
-Q (Default.) Print error messages.
-6 Use IPv6 connections. This will set PROTO to TCP6 and put IPv6
addresses in TCP6LOCALIP and TCP6REMOTEIP.
-c n Do not handle more than n simultaneous connections. If there
are n simultaneous connections copies of prog running, defer
acceptance of a new connection until one copy finishes. n must
be a positive integer. The default value is 40.
-x cdb Follow the rules compiled into cdb by tcprules. These rules may
specify setting environment variables or rejecting connections
from bad sources. You can rerun tcprules to change the rules
while sslserver is running.
-X With -x cdb, allow connections even if -I cdb does not exist.
Normally sslserver will drop the connection if cdb does not
Write banner to the network immediately after each SSL
connection is made. The banner is subject to SSL encryption.
-g gid Switch group ID to gid after preparing to receive connections.
gid must be a positive integer.
-u uid Switch user ID to uid after preparing to receive connections.
uid must be a positive integer.
-U Same as -g $GID -u $UID. Typically, $GID and $UID are set by
Bind to the network interface ifname ("eth0" on Linux, for
example). This is only defined and needed for IPv6 link-local
-b n Allow a backlog of approximately n pending connections.
-o Leave IP options alone. If the client is sending packets along
an IP source route, send packets back along the same route.
-O (Default.) Kill IP options. A client can still use source
routing to connect and to send data, but packets will be sent
back along the default route.
-d Delay sending data for a fraction of a second whenever the
remote host is responding slowly. This is currently the default,
but it may not be in the future; if you want it, set it
-D Never delay sending data; enable TCP_NODELAY.
-t n Give up on the $SSLREMOTEINFO connection attempt after n
-N (Default.) Setup the SSL environment immediately.
-s Store client and server certificate information in the
environment, a la mod_ssl.
-S (Default.) Do not store client and server certificate
information in the environment.
X509 certificate and encryption options:
-3 Read a null-terminated key password from file descriptor 3.
-m (Mail.) Require valid client certificates, but don't check for
-z (Host.) Require valid client certificates and match FQDN (if
given) against SAN/DN.
-Z (Default.) Do not require client certificates.
-h (Default.) Look up the remote host name in DNS to set the
environment variable $SSLREMOTEHOST. In this case, additionally
the CN/SAN in the X509 certificate can be checked, provided, the
option -z is set.
-H Do not look up the remote host name in DNS; remove the
environment variable $SSLREMOTEHOST. To avoid loops, you must
use this option for servers on TCP port 53.
-p Paranoid. After looking up the remote host name in DNS, look up
the IP addresses in DNS for that host name, and remove the
environment variable $SSLREMOTEHOST if none of the addresses
match the client's IP address.
-P (Default.) Not paranoid.
Do not look up the local host name in DNS; use localname for the
environment variable $SSLLOCALHOST. A common choice for
localname is 0. To avoid loops, you must use this option for
servers on TCP port 53.
-r Attempt to obtain $SSLREMOTEINFO from the remote host.
-R (Default.) Do not attempt to obtain $SSLREMOTEINFO from the
remote host. To avoid loops, you must use this option for
servers on TCP ports 53 and 113.
or alternatively the environment variable $DNSREWRITEFILE points to a
SSL ENVIRONMENT VARIABLES READ
These variables define the run-time environment of sslserver and are
used to specify X509 certificates and keyfile per connection.
$SSL_USER=name The user, reading the certificates and keyfile.
The respective user group.
The numerical UID of the $SSL_USER.
Perform reading of certificates and keyfile in a $SSL_CHROOT
If set, overrides the compiled-in CA file name. The CA file
contains the list of CAs used to verify the client certificate.
Certificates in $CAFILE are processed when the server starts.
If set, overrides the compiled-in CA directory name. The CA
directory contains certificates files used to verify the client
certificate. This list augments the list from $CAFILE.
Certificates in $CADIR are processed during certificate
If set, overrides the compiled-in certificate file name. The
server presents this certificate to clients.
If set, overrides the compiled-in certificate chainfile name.
The server presents this list of certificats to clients. Note:
Providing $CERTCHAINFILE has precedence over $CERTFILE.
Certificates in this file needs to be 'ordered' starting from
the uppermost root certificates and placing your host's
certificate at the end.
If set, override the compiled-in SSL cipher list defining the
security level for the connection. A typical choice would be
If set, overrides the compiled-in DH parameter file name.
If set, overrides the compiled-in key file name. The key is
connection base) the client certificate request.
If set, sslserver requests a valid client certificate on a per-
connection base, unlike the general option -z.
SSL ENVIRONMENT VARAIBLES SET
In case sslserver is called with the option -e, the following mod_ssl
environment variables are provided:
The TLS protocol version (SSLv3, TLSv1, ...).
The hex-encoded SSL session id.
The cipher specification name.
Number of cipher bits (actually used).
Number of cipher bits (possible).
The mod_ssl program version.
The OpenSSL program version.
The version of the client certificate.
The serial of the client certificate.
Subject DN in client's certificate.
Component of client's Subject DN.
Issuer DN of client's certificate.
Component of client's Issuer DN.
Validity of client's certificate (start time).
NONE, SUCCESS, GENEROUS or FAILED:reason.
The serial of the server certificate.
Subject DN in server's certificate.
Component of server's Subject DN.
Issuer DN of server's certificate.
Component of server's Issuer DN.
Validity of server's certificate (start time).
Validity of server's certificate (end time).
Algorithm used for the signature of server's certificate.
Algorithm used for the public key of server's certificate.
PEM-encoded server certificate.
For $SSL_CLIENT_x_DN_x509 and $SSL_SERVER_x_DN_x509, x509 denotes a
component of the DN: C, ST, L, O, OU, CN, T, I, G, S, D, UID, Email.
Other SSL environment variables set:
PROTO, SSLLOCALHOST, SSLLOCALIP, SSLLOCALPORT, SSLREMOTEHOST,
SSLREMOTEINFO, SSLREMOTEIP, SSLREMOTEPORT.
TCP environment variables set:
TCPLOCALHOST, TCPLOCALIP, TCPLOCALPORT, TCPREMOTEHOST, TCPREMOTEINFO,
TCP6 environment variables set:
TCP6INTERFACE, TCP6LOCALHOST, TCP6LOCALIP, TCP6LOCALPORT,
TCP6REMOTEHOST, TCP6REMOTEIP, TCP6REMOTEPORT.
LOGGING AND ERROR MESSAGES
sslserver prints information about individual connections in case -v or
-V is specified as argument. TLS error messages are provided if
unable to speak TLS for pid: ... DH lib
TLS handshake failure.
unable to accept TLS for pid: ...
The remote socket was prematurely closed.
sslclient(1), sslconnect(1), sslcat(1), https@(1), ucspi-tls(2),
tcprules(1), tcprulescheck(1), tcpserver(1), tcp-environ(5)
Man(1) output converted with