web application with secured sections, sessions and related trouble

I would like to create web application with admin/checkout sections being secured. Assuming I have SSL set up for subdomain.mydomain.com I would like to make sure that all that top-secret stuff ;) like checkout pages and admin section is transferred securely. Would it be ok to structure my application as below?

subdomain.mydomain.com
    adminSectionFolder
        adminPage1.php
        adminPage2.php
    checkoutPagesFolder
        checkoutPage1.php
        checkoutPage2.php
        checkoutPage3.php
    homepage.php
    loginPage.php
    someOtherPage.php
    someNonSecureFolder
        nonSecurePage1.php
        nonSecurePage2.php
        nonSecurePage3.php
    imagesFolder
        image1.jpg
        image2.jpg
        image3.jpg

Users would access my web application via http as there is no need for SSL for homepage and similar. Checkout/admin pages would have to be accessed via https though (that I would ensure via .htaccess redirects). I would also like to have login form on every page of the site, including non-secure pages. Now my questions are:

1. if I have form on non-secure page e.g http://subdomain.mydomain.com/homepage.php and that form sends data to https://subdomain.mydomain.com/loginPage.php, is data being send encrypted as if it were sent from https://subdomain.mydomain.com/homepage.php? I do realize users will not see padlock, but browser still should encrypt it, is it right?

EDIT: my apologies.. above in bold I originally typed http but meant https, my bad

2.If on secure page loginPage.php (or any other accessed via https for that instance) I created session, session ID would be assigned, and in case of my web app. something like username of the logged in user. Would I be able to access these session variable from http://subdomain.mydomain.com/homepage.php to for example display greeting message? If session ID is stored in cookies then it would be trouble I assume, but could someone clarify how it should be done? It seems important to have username and password send over SSL.

3.Related to above question I think.. would it actually make any sense to have login secured via SSL so usenrame/password would be transferred securely, and then session ID being transferred with no SSL? I mean wouldnt it be the same really if someone caught username and password being transferred, or caught session ID? Please let me know if I make sense here cause it feels like I'm missing something important.

EDIT: I came up with idea but again please let me know if that would work. Having above, so assuming that sharing session between http and https is as secure as login in user via plain http (not https), I guess on all non secure pages, like homepage etc. I could check if user is already logged in, and if so from php redirect to https version of same page. So user fills in login form from homepage.php, over ssl details are send to backend so probably https://.../homepage.php. Trying to access http://.../someOtherPage.php script would always check if session i开发者_运维问答s created and if so redirect user to https version of this page so https://.../someOtherPage.php. Would that work?

4.To avoid browser popping message "this page contains non secure items..." my links to css, images and all assets, e.g. in case of http://subdomain.mydomain.com/checkoutPage1.php should be absolute so "/images/image1.jpg" or relative so "../images/image1.jpg"? I guess one of those would have to work :)

wow that's long post, thanks for your patience if you got that far and any answers :) oh yeh and I use php/apache on shared hosting

If the SSL termination is on the webserver itself, then you'll probably need to configure seperate document roots for the secure and non-secure parts - while you could specify that these both reference the same physical directory, you're going to get tied in knots switching between the parts. Similarly if your SSL termination is before the webserver you've got no systematic separation of the secure and non-secure parts.

Its a lot tidier to separate out the secure and non-secure parts into seperate trees - note that if you have non-SSL content on a secure page, the users will get warning messages.

Regards your specific questions

1. NO - whether data is encrypted depends on where it is GOING TO, not where it is coming from

2. YES - but only if you DO NOT set the secure_only cookie flag - note that if you follow my recommendations above, you also need to ensure that the cookie path is set to '/'

3. the page which processes the username and password MUST be secure. If not then you are exposing your clients authentication details (most people use the same password for all the sites they visit) and anyone running a network sniffer or proxy would have access.

Your EDIT left me a bit confused. SSL is computationally expensive and slow - so you want to minimise its use - but you need to balance this with your users perception of security - don't keep switching from SSL to non-SSL, and although its perfectly secure for users to enter their details on a page served up by non-SSL which sends to a SSL page, the users may not understand this distinction.

4. See the first part of my answer above.

C.