openssl/ssl

22 Jun 1996
This file belongs in ../apps, but I'll leave it here because it deals
with SSL :-) It is rather dated but it gives you an idea of how
things work.
===

17 Jul 1995
I have been changing things quite a bit and have not fully updated
this file, so take what you read with a grain of salt
eric
===
The s_client and s_server programs can be used to test SSL capable
IP/port addresses and the verification of the X509 certificates in use
by these services. I strongly advise having a look at the code to get
an idea of how to use the authentication under SSLeay. Any feedback
on changes and improvements would be greatly accepted.

This file will probably be gibberish unless you have read
rfc1421, rfc1422, rfc1423 and rfc1424 which describe PEM
authentication.

A Brief outline (and examples) how to use them to do so.

NOTE:
The environment variable SSL_CIPER is used to specify the prefered
cipher to use, play around with setting it's value to combinations of
RC4-MD5, EXP-RC4-MD5, CBC-DES-MD5, CBC3-DES-MD5, CFB-DES-NULL
in a : separated list.

This directory contains 3 X509 certificates which can be used by these programs.
client.pem: a file containing a certificate and private key to be used
by s_client.
server.pem :a file containing a certificate and private key to be used
by s_server.
eay1024.pem:the certificate used to sign client.pem and server.pem.
This would be your CA's certificate. There is also a link
from the file a8556381.0 to eay1024.PEM. The value a8556381
is returned by 'x509 -hash -noout value used by X509 verification routines to 'find' this
certificte when search a directory for it.
[the above is not true any more, the CA cert is
../certs/testca.pem which is signed by ../certs/mincomca.pem]

When testing the s_server, you may get
bind: Address already in use
errors. These indicate the port is still being held by the unix
kernel and you are going to have to wait for it to let go of it. If
this is the case, remember to use the port commands on the s_server and
s_client to talk on an alternative port.

=====
s_client.
This program can be used to connect to any IP/hostname:port that is
talking SSL. Once connected, it will attempt to authenticate the
certificate it was passed and if everything works as expected, a 2
directional channel will be open. Any text typed will be sent to the
other end. type Q to exit. Flags are as follows.
-host arg : Arg is the host or IP address to connect to.
-port arg : Arg is the port to connect to (https is 443).
-verify arg : Turn on authentication of the server certificate.
: Arg specifies the 'depth', this will covered below.
-cert arg : The optional certificate to use. This certificate
: will be returned to the server if the server
: requests it for client authentication.
-key arg : The private key that matches the certificate
: specified by the -cert option. If this is not
: specified (but -cert is), the -cert file will be
: searched for the Private key. Both files are
: assumed to be in PEM format.
-CApath arg : When to look for certificates when 'verifying' the
: certificate from the server.
-CAfile arg : A file containing certificates to be used for
: 'verifying' the server certificate.
-reconnect : Once a connection has been made, drop it and
: reconnect with same session-id. This is for testing :-).

The '-verify n' parameter specifies not only to verify the servers
certificate but to also only take notice of 'n' levels. The best way
to explain is to show via examples.
Given
s_server -cert server.PEM is running.

s_client
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo server
issuer= /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify error:num=1:unable to get issuer certificate
verify return:1
CIPHER is CBC-DES-MD5
What has happened is that the 'SSLeay demo server' certificate's
issuer ('CA') could not be found but because verify is not on, we
don't care and the connection has been made anyway. It is now 'up'
using CBC-DES-MD5 mode. This is an unauthenticate secure channel.
You may not be talking to the right person but the data going to them
is encrypted.

s_client -verify 0
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo server
issuer= /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify error:num=1:unable to get issuer certificate
verify return:1
CIPHER is CBC-DES-MD5
We are 'verifying' but only to depth 0, so since the 'SSLeay demo server'
certificate passed the date and checksum, we are happy to proceed.

s_client -verify 1
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo server
issuer= /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify error:num=1:unable to get issuer certificate
verify return:0
ERROR
verify error:unable to get issuer certificate
In this case we failed to make the connection because we could not
authenticate the certificate because we could not find the
'CA' certificate.

s_client -verify 1 -CAfile eay1024.PEM
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo server
verify return:1
depth=1 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify return:1
CIPHER is CBC-DES-MD5
We loaded the certificates from the file eay1024.PEM. Everything
checked out and so we made the connection.

s_client -verify 1 -CApath .
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo server
verify return:1
depth=1 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify return:1
CIPHER is CBC-DES-MD5
We looked in out local directory for issuer certificates and 'found'
a8556381.0 and so everything is ok.

It is worth noting that 'CA' is a self certified certificate. If you
are passed one of these, it will fail to 'verify' at depth 0 because
we need to lookup the certifier of a certificate from some information
that we trust and keep locally.

SSL_CIPHER=CBC3-DES-MD5:RC4-MD5
export SSL_CIPHER
s_client -verify 10 -CApath . -reconnect
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo server
verify return:1
depth=1 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify return:1
drop the connection and reconnect with the same session id
CIPHER is CBC3-DES-MD5
This has done a full connection and then re-estabished it with the
same session id but a new socket. No RSA stuff occures on the second
connection. Note that we said we would prefer to use CBC3-DES-MD5
encryption and so, since the server supports it, we are.

=====
s_server
This program accepts SSL connections on a specified port
Once connected, it will estabish an SSL connection and optionaly
attempt to authenticate the client. A 2 directional channel will be
open. Any text typed will be sent to the other end. Type Q to exit.
Flags are as follows.
-port arg : Arg is the port to listen on.
-verify arg : Turn on authentication of the client if they have a
: certificate. Arg specifies the 'depth'.
-Verify arg : Turn on authentication of the client. If they don't
: have a valid certificate, drop the connection.
-cert arg : The certificate to use. This certificate
: will be passed to the client. If it is not
: specified, it will default to server.PEM
-key arg : The private key that matches the certificate
: specified by the -cert option. If this is not
: specified (but -cert is), the -cert file will be
: searched for the Private key. Both files are
: assumed to be in PEM format. Default is server.PEM
-CApath arg : When to look for certificates when 'verifying' the
: certificate from the client.
-CAfile arg : A file containing certificates to be used for
: 'verifying' the client certificate.

For the following 'demo' I will specify the s_server command and
the s_client command and then list the output from the s_server.
s_server
s_client
CONNECTED
CIPHER is CBC-DES-MD5
Everything up and running

s_server -verify 0
s_client
CONNECTED
CIPHER is CBC-DES-MD5
Ok since no certificate was returned and we don't care.

s_server -verify 0
./s_client -cert client.PEM
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo client
issuer= /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify error:num=1:unable to get issuer certificate
verify return:1
CIPHER is CBC-DES-MD5
Ok since we were only verifying to level 0

s_server -verify 4
s_client -cert client.PEM
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo client
issuer= /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify error:num=1:unable to get issuer certificate
verify return:0
ERROR
verify error:unable to get issuer certificate
Bad because we could not authenticate the returned certificate.

s_server -verify 4 -CApath .
s_client -cert client.PEM
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo client
verify return:1
depth=1 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify return:1
CIPHER is CBC-DES-MD5
Ok because we could authenticate the returned certificate :-).

s_server -Verify 0 -CApath .
s_client
CONNECTED
ERROR
SSL error:function is:REQUEST_CERTIFICATE
:error is :client end did not return a certificate
Error because no certificate returned.

s_server -Verify 4 -CApath .
s_client -cert client.PEM
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo client
verify return:1
depth=1 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify return:1
CIPHER is CBC-DES-MD5
Full authentication of the client.

So in summary to do full authentication of both ends
s_server -Verify 9 -CApath .
s_client -cert client.PEM -CApath . -verify 9
From the server side
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo client
verify return:1
depth=1 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify return:1
CIPHER is CBC-DES-MD5
From the client side
CONNECTED
depth=0 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=SSLeay demo server
verify return:1
depth=1 /C=AU/SOP=QLD/O=Mincom Pty. Ltd./OU=CS/CN=CA
verify return:1
CIPHER is CBC-DES-MD5

For general probing of the 'internet https' servers for the
distribution area, run
s_client -host www.netscape.com -port 443 -verify 4 -CApath ../rsa/hash
Then enter
GET /
and you should be talking to the https server on that host.

www.rsa.com was refusing to respond to connections on 443 when I was
testing.

have fun :-).

eric