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Apache

System check - Syntax testing

• Syntax check

$ apache2ctl configtest

• Get a list of all virtual hosts which are defined in all apache configuration files:

$ apache2ctl -S

Redirect RedirectMatch Rewrite

First the differences

• Redirect sends folks looking for one url to another - that they always see in the address-bar
• RedirectMatch Just like Redircect except you can pass parts of the old url to the new url
• Rewrite Can do all that and send a different url and not tell the browser.

The choice depends on just what you need to do. Rewrite is complex - learning curve - but you can serve alternative urls without giving a HTML code. If you are only doing a simple redirection - possibly matching some urls - redirect is the way to go. When you can't do it with Redirect, you will probably want to start learning Mod_Rewrite.

• Important - if you rewrite to the whole url ( http://example.com/fishnets.htm ) - it redirects and the address bar in the browser is updated. If instead you rewrite without the domain parte ( /fishnets.htm ) it only sends it - the url is unchanged unless you issue a R= flag.

Rewrite Notes

Flags

Rewrite Flags - multiple flags are separated by commas [C,B]

• L = Last. Stop processing RewriteRules once this one matches. Order counts!
• C = Chain. Continue processing the next RewriteRule. If this rule doesn't match, then the next rule won't be executed. More on this later.
• E = Set environmental variable. Apache has various environmental variables that can affect web-server behavior.
• F = Forbidden. Returns a 403-Forbidden error if this rule matches.
• G = Gone. Returns a 410-Gone error if this rule matches.
• H = Handler. Forces the request to be handled as if it were the specified MIME-type.
• N = Next. Forces the rule to start over again and re-match. BE CAREFUL! Loops can result.
• NC = No case. Allows [jpg] to match both jpg and JPG.
• NE = No escape. Prevents the rewriting of special characters (. ? # & etc) into their hex-code equivalents.
• NS = No subrequests. If you're using server-side-includes, this will prevent matches to the included files.
• P = Proxy. Forces the rule to be handled by mod_proxy. Transparently provide content from other servers, because your web-server fetches it and re-serves it. This is a dangerous flag, as a poorly written one will turn your web-server into an open-proxy and That is Bad.
• PT = Pass Through. Take into account Alias statements in RewriteRule matching.
• QSA = QSAppend. When the original string contains a query (http://example.com/thing?asp=foo) append the original query string to the rewritten string. Normally it would be discarded. Important for dynamic content.
• R = Redirect. Provide an HTTP redirect to the specified URL. Can also provide exact redirect code [R=303]. Very similar to RedirectMatch, which is faster and should be used when possible.
• S = Skip. Skip this rule.
• T = Type. Specify the mime-type of the returned content. Very similar to the AddType directive.

Matching and Escaping

• Use the \ (back-slash) to escape any of the following characters. * . $ + \ become \* \. \$ \+ \[ \]

Simple matching

^ 	Start matching at this point
$ 	End point of the match
. 	Any character
[] 	Starts a class
| 	Starts alternative match this|that would mean match this or that
() 	starts a back reference point
? 	match 0 or 1 time Quantifier
+ 	match atleast 1 or more times Quantifier
* 	match 0 to infinite times Quantifier
{} 	match minimum to maximum Quantifier {0,3} match up to 3 times

Class Definitions

• What is in the brackets [] denotes a class

Char. 	Definition
^ 	Negates the class. [^A-Z]+ means don't match any uppercases
\ 	Use before any of the following characters to escape or null the meaning or it. [\+]+
- 	Range for matching [0-9]+ [a-zA-Z]+

Apache error log

Ignore these

[error] Hostname 123.123.123.123 provided via SNI and hostname example.com provided via HTTP are different

From a bot that is using the IP rather than the domain name.

[error] [client 195.159.233.44] rejecting client initiated renegotiation

Someone probing TLS

www-prefix

Using a www-prfix advertised stupidity. www is spam and not useful Dump the www in your configs and register at http://no-www.org/