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Common Lisp define is a directory that is a subdirectory or other directory

I am using hunchentoot to create a simple web application to open a directory tree on the internet. The problem I am facing is finding a reliable and secure way to determine if the requested directory is actually a child directory *share-root*

, which is /srv/share

.

I spent time cl-fad, but it's not exactly what I need (or I am not using it in a way that solves my problem).

My goal is to be able to get a path like: /srv/share/media/../../../

and understand that the request should be ignored because it is requesting something outside of the share.

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1 answer


I suggest enough-namestring

in combination with truename

: if

(enough-namestring foo bar)

is a relative path, then foo

is under bar

. In other words:

(defun pathname-under-p (under top)
  (case (car (pathname-directory (enough-namestring (truename under)
                                                    (truename top))))
    ((nil :relative) t)
    (t nil)))


or simply

(defun pathname-under-p (under top)
  (not (eq :absolute (car (pathname-directory (enough-namestring (truename under)
                                                                 (truename top)))))))

If your implementation does not support truename

in the directory, you will have to use the implementation-defined function or directory

.

Many thanks to @Svante for debugging.

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