site.authent — Another Example

site.authent is set up with two virtual hosts, one for customers and one for salespeople, and each has its own logs in ... /logs/customers and ... /logs/salesmen. We can follow that scheme and apply one LogFormat to both, or each can have its own logs with its own LogFormats inside the <VirtualHost> directives. They can also have common log files, set up by moving ErrorLog and TransferLog outside the <VirtualHost> sections, with different LogFormats within the sections to distinguish the entries. In this last case, the LogFormat files could look like this:

<VirtualHost www.butterthlies.com>
LogFormat "Customer:..."
...
</VirtualHost>

<VirtualHost sales.butterthlies.com>
LogFormat "Sales:..."
...
</VirtualHost>

Let’s experiment with a format for customers, leaving everything else the same:

<VirtualHost www.butterthlies.com>
LogFormat "customers: host %h, logname %l, user %u, time %t, request %r
    status %s, bytes %b,"
...

We have inserted the words host , logname, and so on to make it clear in the file what is doing what. In real life you probably wouldn’t want to clutter the file up in this way because you would look at it regularly and remember what was what or, more likely, process the logs with a program that would know the format. Logging on to www.butterthlies.com and going to summer catalog produces this log file:

customers: host 192.168.123.1, logname unknown, user -, time [07/Nov/
    1996:14:28:46 +0000], request GET / HTTP/1.0, status 200,bytes -
customers: host 192.168.123.1, logname unknown, user -, time [07/Nov/
    1996:14:28:49 +0000], request GET /hen.jpg HTTP/1.0, status 200,
    bytes 12291,
customers: host 192.168.123.1, logname unknown, user -, time [07/Nov
    /1996:14:29:04 +0000], request GET /tree.jpg HTTP/1.0, status 200,
    bytes 11532,
customers: host 192.168.123.1, logname unknown, user -, time [07/Nov/
    1996:14:29:19 +0000], request GET /bath.jpg HTTP/1.0, status 200,
    bytes 5880,

This is not too difficult to follow. Notice that while we have logname unknown, the user is -, the usual report for an unknown value. This is because customers do not have to give an ID; the same log for salespeople, who do, would have a value here.

We can improve things by inserting lists of conditions based on the error codes after the % and before the command letter. The error codes are defined in the HTTP 1.0 specification:

200 OK
302 Found
304 Not Modified
400 Bad Request
401 Unauthorized
403 Forbidden
404 Not found
500 Server error
503 Out of resources
501 Not Implemented
502 Bad Gateway

The list from HTTP 1.1 is as follows:

100  Continue
101  Switching Protocols
200  OK
201  Created
202  Accepted
203  Non-Authoritative Information
204  No Content
205  Reset Content 
206  Partial Content
300  Multiple Choices
301  Moved Permanently
302  Moved Temporarily
303  See Other
304  Not Modified
305  Use Proxy
400  Bad Request
401  Unauthorized
402  Payment Required
403  Forbidden
404  Not Found
405  Method Not Allowed
406  Not Acceptable
407  Proxy Authentication Required
408  Request Time-out
409  Conflict
410  Gone
411  Length Required
412  Precondition Failed
413  Request Entity Too Large
414  Request-URI Too Large
415  Unsupported Media Type
500  Internal Server Error
501  Not Implemented
502  Bad Gateway
503  Service Unavailable
504  Gateway Time-out
505  HTTP Version not supported

You can use ! before a code to mean “if not.” !200 means “log this if the response was not OK.” Let’s put this in salesmen:

<VirtualHost sales.butterthlies.com>
LogFormat "sales: host %!200h, logname %!200l, user %u, time %t, request %r,
    status %s,bytes %b,"
...

An attempt to log in as fred with the password don't know produces the following entry:

sales: host 192.168.123.1, logname unknown, user fred, time [19/Aug/
    1996:07:58:04 +0000], request GET HTTP/1.0, status 401, bytes -

However, if it had been the infamous bill with the password theft, we would see:

host -, logname -, user bill, ...

because we asked for host and logname to be logged only if the request was not OK. We can combine more than one condition, so that if we only want to know about security problems on sales, we could log usernames only if they failed to authenticate:

LogFormat "sales: bad user: %400,401,403u"

We can also extract data from the HTTP headers in both directions:

%[condition]{user-agent}i

This prints the user agent (i.e., the software the client is running) if condition is met. The old way of doing this was AgentLog logfile and ReferLog logfile.