in reply to Re^2: Insecure CPAN module in taint mode
in thread Insecure CPAN module in taint mode

Your example code assumes that the entirety of /usr and /bin are inherently safe. I cannot answer for you whether that is true on your webserver (which, IIRC, is a shared hosting server). edit:in light of afoken's additional points, I concur that your snippet was not sufficient./edit

Further, your example code ignores the remainder of the untainting in my example snippet, and shows that you didn't read the whole of perlsec, nor even the few paragraphs in the section called Cleaning Up Your Path. The delete was there for a reason; that reason was explained in the documentation I linked, but can be summed up in the statement that those other environment variables can affect execution similar to PATH. If you do not follow the complete advice, perl will still consider $ENV{PATH} tainted until you take care of those other environment variables as well.

But if you believe the assumptions about those paths is valid, and if you have implemented but not shown the other advice mentioned, then your code seems a reasonable way of making sure that only the "safe" path elements are included. edit:struck out; see afoken's additional points for why your code still isn't a reasonable way to trim the PATH/edit

But, while cleaning up PATH (and the related variables) is advisable from an un-tainting perspective, I think that Corion's advice in Re: Insecure CPAN module in taint mode is still even better: why fork out to an external process unless necessary?

edit:see inline edits/edit

Replies are listed 'Best First'.
Re^4: Insecure CPAN module in taint mode
by Bod (Deacon) on Jul 06, 2021 at 22:22 UTC
    and shows that you didn't read the whole of perlsec, nor even the few paragraphs in the section called Cleaning Up Your Path

    I did!
    I put the delete in. Once the error had gone I commented that line out to see if it was necessary and the error did not return. Hence why I didn't include it in the code snippet.

    I think that Corion's advice...

    Good advice it may be. But on this shared hosting (you remembered correctly) it didn't work - Re^2: Insecure CPAN module in taint mode

      I put the delete in. Once the error had gone I commented that line out to see if it was necessary and the error did not return.

      Sorry, since your example didn't include the delete, I interpreted that to mean that you hadn't used it. (I've only got what you show me to go on, so that's not an unreasonable interpretation.)

      My first experiment didn't have the delete but did change the PATH, and it wasn't sufficient to remove the taint message; my second experiment added the delete and the taint message went away; in a later experiment, I accidentally forgot the delete, and the taint message came back. So I don't know how the taint message went away for you. I would personally be worried that it will come back unexpectedly; since it doesn't hurt to leave it in, that would be my recommendation.

        I would personally be worried that it will come back unexpectedly; since it doesn't hurt to leave it in, that would be my recommendation

        On that recommendation, it has been added back in...