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mod_ssl
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Compatibility
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F.A.Q. List
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``The solution of this problem is trivial
and is left as an exercise for the reader.''
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Standard textbook cookie
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ow to solve particular security constraints for an SSL-aware webserver
is not always obvious because of the coherences between SSL, HTTP and Apache's
way of processing requests. This chapter gives instructions on how to solve
such typical situations. Treat is as a first step to find out the final
solution, but always try to understand the stuff before you use it. Nothing is
worse than using a security solution without knowing it's restrictions and
coherences.
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How can I authenticate clients based on certificates when I know all my
clients?
[L]
When you know your user community (i.e. a closed user group situation), as
it's the case for instance in an Intranet, you can use plain certificate
authentication. All you have to do is to create client certificates signed by
your own CA certificate ca.crt and then verifiy the clients
against this certificate.
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httpd.conf |
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# require a client certificate which has to be directly
# signed by our CA certificate in ca.crt
SSLVerifyClient require
SSLVerifyDepth 1
SSLCACertificateFile conf/ssl.crt/ca.crt
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How can I authenticate my clients for a particular URL based on certificates
but still allow arbitrary clients to access the remaining parts of the server?
[L]
For this we again use the per-directory reconfiguration feature of mod_ssl:
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httpd.conf |
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SSLVerifyClient none
SSLCACertificateFile conf/ssl.crt/ca.crt
<Location /secure/area>
SSLVerifyClient require
SSLVerifyDepth 1
</Location>
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How can I authenticate only particular clients for a some URLs based
on certificates but still allow arbitrary clients to access the remaining
parts of the server?
[L]
The key is to check for various ingredients of the client certficate. Usually
this means to check the whole or part of the Distinguished Name (DN) of the
Subject. For this two methods exists: The mod_auth based variant
and the SSLRequire variant. The first method is good when the
clients are of totally different type, i.e. when their DNs have no common
fields (usually the organisation, etc.). In this case you've to establish a
password database containing all clients. The second method is better
when your clients are all part of a common hierarchy which is encoded into the
DN. Then you can match them more easily.
The first method:
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/usr/local/apache/conf/httpd.conf |
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SSLVerifyClient none
<Directory /usr/local/apache/htdocs/secure/area>
SSLVerifyClient require
SSLVerifyDepth 5
SSLCACertificateFile conf/ssl.crt/ca.crt
SSLCACertificatePath conf/ssl.crt
SSLOptions +FakeBasicAuth
SSLRequireSSL
AuthName "Snake Oil Authentication"
AuthType Basic
AuthUserFile /usr/local/apache/conf/httpd.passwd
require valid-user
</Directory>
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/usr/local/apache/conf/httpd.passwd |
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/C=DE/L=Munich/O=Snake Oil, Ltd./OU=Staff/CN=Foo:xxj31ZMTZzkVA
/C=US/L=S.F./O=Snake Oil, Ltd./OU=CA/CN=Bar:xxj31ZMTZzkVA
/C=US/L=L.A./O=Snake Oil, Ltd./OU=Dev/CN=Quux:xxj31ZMTZzkVA
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The second method:
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httpd.conf |
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SSLVerifyClient none
<Directory /usr/local/apache/htdocs/secure/area>
SSLVerifyClient require
SSLVerifyDepth 5
SSLCACertificateFile conf/ssl.crt/ca.crt
SSLCACertificatePath conf/ssl.crt
SSLOptions +FakeBasicAuth
SSLRequireSSL
SSLRequire %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." and \
%{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"}
</Directory>
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How can
I require HTTPS with strong ciphers and either basic authentication or client
certificates for access to a subarea on the Intranet website for clients
coming from the Internet but still allow plain HTTP access for clients on the
Intranet?
[L]
Let us assume the Intranet can be distinguished through the IP network
192.160.1.0/24 and the subarea on the Intranet website has the URL
/subarea. Then configure the following outside your HTTPS virtual
host (so it applies to both HTTPS and HTTP):
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httpd.conf |
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SSLCACertificateFile conf/ssl.crt/company-ca.crt
<Directory /usr/local/apache/htdocs>
# Outside the subarea only Intranet access is granted
Order deny,allow
Deny from all
Allow from 192.168.1.0/24
</Directory>
<Directory /usr/local/apache/htdocs/subarea>
# Inside the subarea any Intranet access is allowed
# but from the Internet only HTTPS + Strong-Cipher + Password
# or the alternative HTTPS + Strong-Cipher + Client-Certificate
# If HTTPS is used, make sure a strong cipher is used.
# Additionally allow client certs as alternative to basic auth.
SSLVerifyClient optional
SSLVerifyDepth 1
SSLOptions +FakeBasicAuth +StrictRequire
SSLRequire %{SSL_CIPHER_USEKEYSIZE} >= 128
# Force clients from the Internet to use HTTPS
RewriteEngine on
RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.[0-9]+$
RewriteCond %{HTTPS} !=on
RewriteRule .* - [F]
# Allow Network Access and/or Basic Auth
Satisfy any
# Network Access Control
Order deny,allow
Deny from all
Allow 192.168.1.0/24
# HTTP Basic Authentication
AuthType basic
AuthName "Protected Intranet Area"
AuthUserFile conf/protected.passwd
Require valid-user
</Directory>
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Compatibility
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F.A.Q. List
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