Posted almost 7 years ago. Visible to the public.

Test whether Perfect Forward Secrecy (PFS) is enabled on a server (using OpenSSL)

Use the following command to test if a server (in this example: on port 443) uses Perfect Forward Secrecy (PFS):

openssl s_client -connect -cipher ECDHE-RSA-RC4-SHA

You should see something like the following:

~ > openssl s_client -connect -cipher ECDHE-RSA-RC4-SHA CONNECTED(00000003) depth=1 O = AlphaSSL, CN = AlphaSSL CA - G2 verify error:num=20:unable to get local issuer certificate verify return:0 --- Certificate chain 0 s:/C=DE/OU=Domain Control Validated/ i:/O=AlphaSSL/CN=AlphaSSL CA - G2 ...

Note that OpenSSL keeps the connection open if PFS is supported.

In case the server does not support PFS, it looks like this:

~ > openssl s_client -connect localhost:443 -cipher ECDHE-RSA-RC4-SHA CONNECTED(00000003) 140293946562208:error:14077410:SSL routines:SSL23_GET_SERVER_HELLO:sslv3 alert handshake failure:s23_clnt.c:724: --- no peer certificate available --- No client certificate CA names sent --- SSL handshake has read 7 bytes and written 127 bytes --- New, (NONE), Cipher is (NONE) Secure Renegotiation IS NOT supported Compression: NONE Expansion: NONE ---

... and OpenSSL exits.

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Owner of this card:

Thomas Eisenbarth
Last edit:
almost 7 years ago
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Posted by Thomas Eisenbarth to makandra dev
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