listing for S
s_server - SSL/TLS server program
openssl s_server [-accept port] [-context id] [-verify depth] [-Verify
depth] [-cert filename] [-key keyfile] [-dcert filename] [-dkey keyfile]
[-dhparam filename] [-nbio] [-nbio_test] [-crlf] [-debug] [-state] [-CApath
directory] [-CAfile filename] [-nocert] [-cipher cipherlist] [-quiet]
[-no_tmp_rsa] [-ssl2] [-ssl3] [-tls1] [-no_ssl2] [-no_ssl3] [-no_tls1]
[-no_dhe] [-bugs] [-hack] [-www] [-WWW] [-rand filename] [-engine id]
The TCP port to listen on for connections. If not specified 4433 is
Sets the SSL context id. It can be given any string value. If this
option is not present a default value will be used.
The certificate to use. Most server's 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.
The private key to use. If not specified then the certificate file
will be used.
Specifies 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). 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
-nocert If this option is set then no certificate is used. This restricts
the cipher suites available to the anonymous ones (currently just
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.
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.
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.
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.
-state Prints out the SSL session states.
-debug Prints extensive debugging information including a hex dump of all
Tests non-blocking I/O
-nbio Turns on non-blocking I/O
-crlf Translates a line feed from the terminal into CR+LF.
-quiet Inhibits printing of session and certificate information.
-ssl2, -ssl3, -tls1, -no_ssl2, -no_ssl3, -no_tls1
Disables the use of certain SSL or TLS protocols. By default the
initial handshake uses a method which should be compatible with all
servers and permit them to use SSL v3, SSL v2 or TLS as
-bugs There are several known bugs in SSL and TLS implementations. Adding
this option enables various workarounds.
-hack Enables a further workaround for some early Netscape SSL code.
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
is irrelevant. See the ciphers command for more information.
-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
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 an OS-dependent character. The
separator is a semicolon (;) for MS-Windows, a comma (,) for
OpenVMS, and a colon (:) for all others.
Specifying an engine (by its unique id string) will cause s_server
to attempt to obtain a functional reference to the specified
engine, thus initializing it if needed. The engine will then be set
as the default for all available algorithms.
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:
q Ends the current SSL connection but still accept new connections.
Q Ends the current SSL connection and exit.
r Renegotiates the SSL session.
R Renegotiates the SSL session and request a client certificate.
P Sends some plain text down the underlying TCP connection: this
should cause the client to disconnect due to a protocol violation.
S Prints out some session cache status information.
The s_server command implements a generic SSL/TLS server which listens for
connections on a given port using SSL/TLS.
The <command role="strong">s_server command can be used to debug SSL
clients. To accept connections from a web browser the following command can
openssl s_server -accept 443 -www
Most web browsers (in particular Netscape and MSIE) only support RSA cipher
suites, so they cannot connect to servers which do not use a certificate
carrying an RSA key or a version of OpenSSL with RSA disabled.
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
The session parameters can be printed out using the sess_id program.
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 only 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.
Commands: sess_id(1ssl), s_client(1ssl), ciphers(1ssl)
listing for S