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From Quinn Slack <...@cs.stanford.edu>
Subject [PATCH] Add TLS-SRP (RFC 5054) support to mod_ssl
Date Sun, 17 Apr 2011 21:48:11 GMT
Posted at: https://issues.apache.org/bugzilla/show_bug.cgi?id=51075

TLS-SRP (RFC 5054)[1] is an implementation of the Secure Remote Password
(SRP)[2] protocol as a key exchange method for TLS. It uses a shared secret
derived from a user's password to supplement or replace third-party
certificates in authenticating a TLS connection.

This patch adds TLS-SRP support to mod_ssl, adds two new directives
(SSLSRPVerifierFile and SSLSRPUnknownUserSeed), adds two new SSL env vars
(SSL_SRP_USER and SSL_SRP_USERINFO), and includes basic documentation.

The TLS-SRP-specific code uses preprocessor guards on OPENSSL_NO_SRP and is
enabled only if OpenSSL >= 1.0.1, which is the first version of OpenSSL that
will include SRP support[3].

To use this patch:
(1) install OpenSSL 1.0.1;
(2) create an OpenSSL SRP verifier (passwd) file with `openssl srp -srpvfile
passwd.srpv -add username`;
(3) specify this file in the server config with: SSLSRPVerifierFile
/path/to/passwd.srpv
(4) optionally, for easier testing, force the use of SRP: SSLCipherSuite
"!DSS:!aRSA:SRP"

To test the TLS-SRP functionality, use gnutls-cli or a version of cURL with
TLS-SRP support:

gnutls-cli --srpusername user --srppasswd secret host
curl --tlsuser user --tlspassword secret -k https://host

TLS-SRP support for Apache is already provided by mod_gnutls[4]. Now that PAKE
patents have expired and the security of CAs is increasingly being doubted,
TLS-SRP is gaining wider acceptance. GnuTLS, mod_gnutls, and TLSLite have
supported it for years; cURL since February; OpenSSL will support it in the
next release; and I have also assembled patches[5] for Chrome, Firefox, and
NSS.

This patch was originally created by Christophe Renou and Peter Sylvester of
EdelWeb. I updated it to work with Apache 2's mod_ssl.

Bugzilla entry: https://issues.apache.org/bugzilla/show_bug.cgi?id=51075
Patch: https://issues.apache.org/bugzilla/attachment.cgi?id=26892


[1] http://tools.ietf.org/html/rfc5054
[2] http://srp.stanford.edu/
[3] http://cvs.openssl.org/chngview?cn=20484
[4] http://trustedhttp.org/wiki/TLS-SRP_in_Apache_mod_gnutls
[5] http://trustedhttp.org/

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