/usr/man/cat.1/s_server.1
S_SERVER(1) OpenSSL S_SERVER(1)
NAME
openssl-s_server, s_server - SSL/TLS server program
SYNOPSIS
openssl s_server [-accept port] [-context id] [-verify
depth] [-Verify depth] [-crl_check] [-crl_check_all] [-cert
filename] [-certform DER|PEM] [-key keyfile] [-keyform
DER|PEM] [-pass arg] [-dcert filename] [-dcertform DER|PEM]
[-dkey keyfile] [-dkeyform DER|PEM] [-dpass arg] [-dhparam
filename] [-nbio] [-nbio_test] [-crlf] [-debug] [-msg]
[-state] [-CApath directory] [-CAfile filename]
[-no_alt_chains] [-nocert] [-client_sigalgs sigalglist]
[-named_curve curve] [-cipher cipherlist] [-serverpref]
[-quiet] [-no_tmp_rsa] [-ssl2] [-ssl3] [-tls1] [-no_ssl2]
[-no_ssl3] [-no_tls1] [-no_dhe] [-no_ecdhe] [-bugs] [-hack]
[-www] [-WWW] [-HTTP] [-engine id] [-tlsextdebug]
[-no_ticket] [-id_prefix arg] [-rand file(s)] [-serverinfo
file] [-no_resumption_on_reneg] [-status] [-status_verbose]
[-status_timeout nsec] [-status_url url] [-alpn protocols]
[-nextprotoneg protocols]
DESCRIPTION
The s_server command implements a generic SSL/TLS server
which listens for connections on a given port using SSL/TLS.
OPTIONS
-accept port
the TCP port to listen on for connections. If not
specified 4433 is used.
-context id
sets the SSL context id. It can be given any string
value. If this option is not present a default value
will be used.
-cert certname
The certificate to use, most servers cipher suites
require the use of a certificate and some require a
certificate with a certain public key type: for example
the DSS cipher suites require a certificate containing a
DSS (DSA) key. If not specified then the filename
"server.pem" will be used.
-certform format
The certificate format to use: DER or PEM. PEM is the
default.
-key keyfile
The private key to use. If not specified then the
certificate file will be used.
-keyform format
1.0.2t Last change: 2019-09-10 1
S_SERVER(1) OpenSSL S_SERVER(1)
The private format to use: DER or PEM. PEM is the
default.
-pass arg
the private key password source. For more information
about the format of arg see the PASS PHRASE ARGUMENTS
section in openssl(1).
-dcert filename, -dkey keyname
specify an additional certificate and private key, these
behave in the same manner as the -cert and -key options
except there is no default if they are not specified (no
additional certificate and key is used). As noted above
some cipher suites require a certificate containing a
key of a certain type. Some cipher suites need a
certificate carrying an RSA key and some a DSS (DSA)
key. By using RSA and DSS certificates and keys a server
can support clients which only support RSA or DSS cipher
suites by using an appropriate certificate.
-dcertform format, -dkeyform format, -dpass arg
additional certificate and private key format and
passphrase respectively.
-nocert
if this option is set then no certificate is used. This
restricts the cipher suites available to the anonymous
ones (currently just anonymous DH).
-dhparam filename
the DH parameter file to use. The ephemeral DH cipher
suites generate keys using a set of DH parameters. If
not specified then an attempt is made to load the
parameters from the server certificate file. If this
fails then a static set of parameters hard coded into
the s_server program will be used.
-no_dhe
if this option is set then no DH parameters will be
loaded effectively disabling the ephemeral DH cipher
suites.
-no_ecdhe
if this option is set then no ECDH parameters will be
selected, effectively disabling the ephemeral ECDH
cipher suites.
-no_tmp_rsa
certain export cipher suites sometimes use a temporary
RSA key, this option disables temporary RSA key
generation.
1.0.2t Last change: 2019-09-10 2
S_SERVER(1) OpenSSL S_SERVER(1)
-verify depth, -Verify depth
The verify depth to use. This specifies the maximum
length of the client certificate chain and makes the
server request a certificate from the client. With the
-verify option a certificate is requested but the client
does not have to send one, with the -Verify option the
client must supply a certificate or an error occurs.
If the ciphersuite cannot request a client certificate
(for example an anonymous ciphersuite or PSK) this
option has no effect.
-crl_check, -crl_check_all
Check the peer certificate has not been revoked by its
CA. The CRL(s) are appended to the certificate file.
With the -crl_check_all option all CRLs of all CAs in
the chain are checked.
-CApath directory
The directory to use for client certificate
verification. This directory must be in "hash format",
see verify for more information. These are also used
when building the server certificate chain.
-CAfile file
A file containing trusted certificates to use during
client authentication and to use when attempting to
build the server certificate chain. The list is also
used in the list of acceptable client CAs passed to the
client when a certificate is requested.
-no_alt_chains
See the verify manual page for details.
-state
prints out the SSL session states.
-debug
print extensive debugging information including a hex
dump of all traffic.
-msg
show all protocol messages with hex dump.
-nbio_test
tests non blocking I/O
-nbio
turns on non blocking I/O
-crlf
this option translated a line feed from the terminal
1.0.2t Last change: 2019-09-10 3
S_SERVER(1) OpenSSL S_SERVER(1)
into CR+LF.
-quiet
inhibit printing of session and certificate information.
-psk_hint hint
Use the PSK identity hint hint when using a PSK cipher
suite.
-psk key
Use the PSK key key when using a PSK cipher suite. The
key is given as a hexadecimal number without leading 0x,
for example -psk 1a2b3c4d. This option must be provided
in order to use a PSK cipher.
-no_tls1, -no_tls1_1, -no_tls1_2
-ssl2, -ssl3, -tls1, -tls1_1, -tls1_2, -no_ssl2, -no_ssl3,
These options require or disable the use of the
specified SSL or TLS protocols. By default the initial
handshake uses a version-flexible method which will
negotiate the highest mutually supported protocol
version.
-bugs
there are several known bug in SSL and TLS
implementations. Adding this option enables various
workarounds.
-hack
this option enables a further workaround for some some
early Netscape SSL code (?).
-client_sigalgs sigalglist
Signature algorithms to support for client certificate
authentication (colon-separated list)
-named_curve curve
Specifies the elliptic curve to use. NOTE: this is
single curve, not a list. For a list of all possible
curves, use:
$ openssl ecparam -list_curves
-cipher cipherlist
this allows the cipher list used by the server to be
modified. When the client sends a list of supported
ciphers the first client cipher also included in the
server list is used. Because the client specifies the
preference order, the order of the server cipherlist
irrelevant. See the ciphers command for more
information.
1.0.2t Last change: 2019-09-10 4
S_SERVER(1) OpenSSL S_SERVER(1)
-serverpref
use the server's cipher preferences, rather than the
client's preferences.
-tlsextdebug
print out a hex dump of any TLS extensions received from
the server.
-no_ticket
disable RFC4507bis session ticket support.
-www
sends a status message back to the client when it
connects. This includes lots of information about the
ciphers used and various session parameters. The output
is in HTML format so this option will normally be used
with a web browser.
-WWW
emulates a simple web server. Pages will be resolved
relative to the current directory, for example if the
URL https://myhost/page.html is requested the file
./page.html will be loaded.
-HTTP
emulates a simple web server. Pages will be resolved
relative to the current directory, for example if the
URL https://myhost/page.html is requested the file
./page.html will be loaded. The files loaded are assumed
to contain a complete and correct HTTP response (lines
that are part of the HTTP response line and headers must
end with CRLF).
-engine id
specifying an engine (by its unique id string) will
cause s_server to attempt to obtain a functional
reference to the specified engine, thus initialising it
if needed. The engine will then be set as the default
for all available algorithms.
-id_prefix arg
generate SSL/TLS session IDs prefixed by arg. This is
mostly useful for testing any SSL/TLS code (eg. proxies)
that wish to deal with multiple servers, when each of
which might be generating a unique range of session IDs
(eg. with a certain prefix).
-rand file(s)
a file or files containing random data used to seed the
random number generator, or an EGD socket (see
RAND_egd(3)). Multiple files can be specified separated
by a OS-dependent character. The separator is ; for
1.0.2t Last change: 2019-09-10 5
S_SERVER(1) OpenSSL S_SERVER(1)
MS-Windows, , for OpenVMS, and : for all others.
-serverinfo file
a file containing one or more blocks of PEM data. Each
PEM block must encode a TLS ServerHello extension (2
bytes type, 2 bytes length, followed by "length" bytes
of extension data). If the client sends an empty TLS
ClientHello extension matching the type, the
corresponding ServerHello extension will be returned.
-no_resumption_on_reneg
set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
-status
enables certificate status request support (aka OCSP
stapling).
-status_verbose
enables certificate status request support (aka OCSP
stapling) and gives a verbose printout of the OCSP
response.
-status_timeout nsec
sets the timeout for OCSP response to nsec seconds.
-status_url url
sets a fallback responder URL to use if no responder URL
is present in the server certificate. Without this
option an error is returned if the server certificate
does not contain a responder address.
-alpn protocols, -nextprotoneg protocols
these flags enable the Enable the Application-Layer
Protocol Negotiation or Next Protocol Negotiation
extension, respectively. ALPN is the IETF standard and
replaces NPN. The protocols list is a comma-separated
list of supported protocol names. The list should
contain most wanted protocols first. Protocol names are
printable ASCII strings, for example "http/1.1" or
"spdy/3".
CONNECTED COMMANDS
If a connection request is established with an SSL client
and neither the -www nor the -WWW option has been used then
normally any data received from the client is displayed and
any key presses will be sent to the client.
Certain single letter commands are also recognized which
perform special operations: these are listed below.
q end the current SSL connection but still accept new
connections.
1.0.2t Last change: 2019-09-10 6
S_SERVER(1) OpenSSL S_SERVER(1)
Q end the current SSL connection and exit.
r renegotiate the SSL session.
R renegotiate the SSL session and request a client
certificate.
P send some plain text down the underlying TCP connection:
this should cause the client to disconnect due to a
protocol violation.
S print out some session cache status information.
NOTES
s_server can be used to debug SSL clients. To accept
connections from a web browser the command:
openssl s_server -accept 443 -www
can be used for example.
Although specifying an empty list of CAs when requesting a
client certificate is strictly speaking a protocol
violation, some SSL clients interpret this to mean any CA is
acceptable. This is useful for debugging purposes.
The session parameters can printed out using the sess_id
program.
BUGS
Because this program has a lot of options and also because
some of the techniques used are rather old, the C source of
s_server is rather hard to read and not a model of how
things should be done. A typical SSL server program would be
much simpler.
The output of common ciphers is wrong: it just gives the
list of ciphers that OpenSSL recognizes and the client
supports.
There should be a way for the s_server program to print out
details of any unknown cipher suites a client says it
supports.
SEE ALSO
sess_id(1), s_client(1), ciphers(1)
HISTORY
The -no_alt_chains options was first added to OpenSSL
1.0.2b.
1.0.2t Last change: 2019-09-10 7
See also openssl-s_server(1)
Man(1) output converted with
man2html