After experimenting some more I think I resolved this. It seems that
specifying SSLv23_client_method(), in conjunction with SSL_OP_NO_SSLv2 and
SSL_OP_NO_SSLv3, actually does send a TLSv1 handshake record, with {3,3} in the
ClientHello.
What confused me was that the docs for SSLv23_client_method() say "A client
will send out SSLv2 client hello messages". It does not say that when you use
SSL_OP_NO_SSLv2 that it actually sends a TLS 1.0 handshake message (as long as
any TLS version is allowed but even if SSLv3 is enabled). So in my case
SSLv23_client_method() with SSL_OP_NO_SSLv2 and SSL_OP_NO_SSLv3 does the trick.
....................................
Erik Tkal
Juniper OAC/UAC/Pulse Development
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Erik Tkal
Sent: Thursday, August 30, 2012 4:02 PM
To: [email protected]
Subject: FW: Negotiating TLS 1.0 from 1.2
Reposting in openssl-dev. Is this a bug or an oversight or an intentional
omission? Or am I just not doing something right? If I modify s3_pkt.c in
ssl3_get_record() to not fail out but to just change the version in the SSL
session then it seems to work ok.
-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Erik Tkal
Sent: Wednesday, August 29, 2012 2:48 PM
To: [email protected]
Subject: RE: Negotiating TLS 1.0 from 1.2
TLS 1.1 would be acceptable, but the server is 1.0 (we don't have any
implementing 1.1). The server sends a TLS 1.0 ServerHello, which per the RFC
should work:
A TLS 1.2 client who wishes to negotiate with such older servers will
send a normal TLS 1.2 ClientHello, containing { 3, 3 } (TLS 1.2) in
ClientHello.client_version. If the server does not support this
version, it will respond with a ServerHello containing an older
version number. If the client agrees to use this version, the
negotiation will proceed as appropriate for the negotiated protocol.
What I'm trying to figure out is how to tell OpenSSL that the client agrees to
use this version, whereas now it generates a fatal alert. I cannot use an
SSLv2 handshake, as this is inside EAP-TLS.
....................................
Erik Tkal
Juniper OAC/UAC/Pulse Development
-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Abhiram Shandilya
Sent: Wednesday, August 29, 2012 2:38 PM
To: [email protected]
Subject: RE: Negotiating TLS 1.0 from 1.2
Hi Erik:
If you only want to allow TLSv1.2 and TLSv1.0 handshakes you will need to try a
connection with the TLSv1_2_client_method and then by TLSv1_client_method. You
can also use SSLv23_client_method to negotiate only TLSv1.2 and TLSv1.0 using
an SSLv2 handshake by explicitly disabling SSLv2, SSLv3 and TLSv1.1 using
SSL_CTX_set_options(ctx, SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3|SSL_OP_NO_TLSv1_1). At
least that's my understanding.
Regards
Abhi
-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Erik Tkal
Sent: Wednesday, August 29, 2012 10:47 AM
To: [email protected]
Subject: Negotiating TLS 1.0 from 1.2
I have a client that I want to attempt to negotiate TLS 1.2 but will accept TLS
1.0. What is the magic incantation (e.g. TLSv1_client_method() vs
TLSv1_2_client_method() in conjunction with what options)?
Specifying TLSv1_client_method() seems to only offer TLS 1.0 {3,1}. Specifying
TLSv1_2_client_method() offers TLS 1.2 {3,3}, but then when the server returns
a TLS 1.0 {3,1} ServerHello, the client generates a Protocol Version alert.
How do I tell the client that this is acceptable? Appendix E of RFC 5246
indicates this should be possible.
I am using OpenSSL 1.0.1c.
....................................
Erik Tkal
Juniper OAC/UAC/Pulse Development
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