/usr/man/cat.1/openssl-s_server.1.Z
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 file-
name] [-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_resump-
tion_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 pub-
lic key type: for example the DSS cipher suites require a certifi-
cate 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
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 certifi-
cate 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 gener-
ate 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 effec-
tively 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.
-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 informa-
tion. These are also used when building the server certificate
chain.
-CAfile file
A file containing trusted certificates to use during client authen-
tication 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 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.
-ssl2, -ssl3, -tls1, -tls1_1, -tls1_2, -no_ssl2, -no_ssl3, -no_tls1,
-no_tls1_1, -no_tls1_2
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 authentica-
tion (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.
-serverpref
use the server's cipher preferences, rather than the client's pref-
erences.
-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 cor-
rect 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 num-
ber generator, or an EGD socket (see RAND_egd(3)). Multiple files
can be specified separated by a OS-dependent character. The sepa-
rator is ; for 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 Nego-
tiation 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 spe-
cial operations: these are listed below.
q end the current SSL connection but still accept new connections.
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 cer-
tificate is strictly speaking a protocol violation, some SSL clients
interpret this to mean any CA is acceptable. This is useful for debug-
ging 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 2019-09-10 S_SERVER(1)
See also s_server(1)
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