On Thu, Aug 12, 1999 at 12:00:00AM +0000, Jeffrey Altman wrote:
> I am setting the cipher list on both my client and server
>
> ADH-DES-CBC3-SHA:ADH-DES-CBC-SHA
>
> and then attempt to make a TLSv1 connection and get the following
> error:
>
> [TLS - handshake starting]
> [TLS - FAILED]
> 235:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake
> failure:.\ssl\s3_pkt.c:774:SSL alert number 40
>
> Is anyone successfully using these ciphers?
You mention SSL_ALLOW_ADH in the subject line, and if the library is
compiled with -DSSL_ALLOW_ADH, those ciphers indeed work (as you can
easily test by running "openssl s_server -cipher ADH" [beware that
s_server must be run in the apps directory so that it can find its
certificate and key even though those are not needed for ADH ciphers]
and "openssl s_client -cipher ADH". Note that both need the -cipher
option as the current default cipher list does not include ADH).
> The reason why I want them is that by using them I do not need to
> worry about certificates. I want to use TLS for privacy but I am
> willing to use Kerberos V5 for mutual end-user to host authentication.
> I plan to avoid the man in the middle attack which is possible when
> using the ADH ciphers by including the following ASN.1 structure
> in the Kerberos V5 checksum field.
>
> TLS_CHECKSUM_DATA ::= SEQUENCE {
> authentication-type-pair OCTET_STRING, -- 2 bytes
> SSLversion INTEGER, -- SSL version number
> Cipher OCTET_STRING, -- the 3 byte cipher ID
> Session_ID OCTET_STRING, -- the Session ID
> Master_key OCTET_STRING, -- the master key
> }
This is not secure. The master secret is derived from data
transmitted in clear and the premaster secret, which is just the
result of the DH exchange, which *can* be influenced by an attacker in
a way such that the client and server agree on its value and the
attacker knows it too.
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