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Re: (ITS#7506) Diffie-Hellman parameters (DHParamFile) are improperly handled
- To: openldap-its@OpenLDAP.org
- Subject: Re: (ITS#7506) Diffie-Hellman parameters (DHParamFile) are improperly handled
- From: firstname.lastname@example.org
- Date: Mon, 28 Jan 2013 00:28:44 GMT
- Auto-submitted: auto-generated (OpenLDAP-ITS)
I suppose I should attach a test case:
openssl dhparam 1536 > dh1536.pem
openssl req -new -newkey rsa:2048 -keyout server.key \
-out server.crt -sha256 -nodes -subj '/CN=localhost/' -x509
For GnuTLS, load the following config:
For Openssl, change olcTLSCipherSuite to:
Start up slapd with the config, listening on ldaps://localhost:6636.
openssl s_client -connect localhost:6636
With GnuTLS this will fail negotiation; with OpenSSL it will use 1024
bit parameters rather than the 1536 bits params we specified.
The only way I've found to find the actual parameter size is to tcpdump
the negotiation. First, verify that the negotiated cipher suite is
DHE-RSA-AES128-SHA according to s_client, then:
tcpdump -i lo -wldap.pcap port 6636
Apply the SSL decode to the traffic (right click on packet, Decode As,
Transport tab, SSL), find the Server Key Exchange packet, select the
Server Key Exchange portion of the handshake message, and look at the
It should start with 0c, followed by a three byte size, then the next
two bytes are the length of the DH parameters: 0080 for 1024 bits, 00c0
for 1536 bits.
On 01/27/2013 07:13 PM, openldap-its@OpenLDAP.org wrote:
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