Web application behind reverse proxy - how do I handle SSL?

Question

I have a public Apache server which needs to proxy to an internal Apache server (for SVN access). What I'd like to have is:

User  ---[HTTPS]--->  Web Server  ---[HTTP]--->  SVN Server

I'm not too familiar with SSL handling, so I'd like some opinions on this approach. Is this an ok model; should I be using SSL everywhere, etc.

My approach works for the most part, but fails when rewriting redirects back to HTTPS. If a user goes to

    https://acme.web.mcx/svn (no trailing '/')

they are redirected by the SVN server to

    http://acme.web.mcx/svn/ (almost there!) 

Here's my config for the Web Server (Proxying server):

<VirtualHost *:443>
    ServerAdmin me@admin.com
    ServerAlias *.web.mcx www.web.mcx web.mcx

    DocumentRoot /server/web/app/webroot
    ErrorLog logs/web-error_log
    CustomLog logs/web-access_log common

    RewriteEngine On

    RewriteCond %{HTTP_HOST} !^www\.web\.mcx$ [NC]
    RewriteCond %{HTTP_HOST} ^(www\.)?([^.]+)\.web\.mcx$ [NC]
    RewriteRule ^/svn(.*) http://db.mcx/svn$1 [P]
    ProxyPassReverse /svn http://db.mcx/svn
    ProxyPreserveHost on

    SSLEngine on
    SSLCertificateFile      /etc/httpd/ssl/server.crt
    SSLCertificateKeyFile   /etc/httpd/ssl/server.key
    SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown

    ProxyRequests Off
    <Proxy *>
        Order deny,allow
        Allow from all
    </Proxy>
    ProxyVia On

<Location /svn/>
    <Limit OPTIONS PROPFIND GET REPORT MKACTIVITY PROPPATCH PUT CHECKOUT MKCOL MOVE COPY DELETE LOCK UNLOCK MERGE>
        Order Deny,Allow
        Allow from all
        Satisfy Any
    </Limit>
</Location>

Answer 1

I keep answering my own questions :)

Here's my 'works until it breaks' solution: I changed my VirtualHost setting to always redirect http:// requests for /svn* to https. The client will be redirected twice sometimes (if they don't use the trailing slash), but that's ok with me. Redirect one: SVN server redirects client to the proper path with a slash (although forgets about https), redirect two: Web server redirects client back to https.

<VirtualHost *:80>
    ServerAdmin me@admin.com
    ServerAlias *.web.mcx www.web.mcx web.mcx

    DocumentRoot /server/web/app/webroot
    ErrorLog logs/web-error_log
    CustomLog logs/web-access_log common

    RewriteEngine On

    RewriteCond %{HTTP_HOST} !^www\.web\.mcx$ [NC]
    RewriteCond %{HTTP_HOST} ^(www\.)?([^.]+)\.web\.mcx$ [NC]
    RewriteCond %{REQUEST_URI} svn.*
    RewriteRule ^(.*)$ https://%{HTTP_HOST}$1 [R,L]

    ProxyRequests Off
</VirtualHost>