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Re: [Bug-wget] Contribution on bug #45037

From: Ángel González
Subject: Re: [Bug-wget] Contribution on bug #45037
Date: Sun, 17 May 2015 00:56:50 +0200
User-agent: Thunderbird

On 16/05/15 22:10, Ander Juaristi Alamos wrote:

I found another task where I want to contribute, the issue with 45037.
For what I understand, and read in the mailling list, the problem occur inftp.c
ftp_loop_internal ->  remove_link.

But what I don't understand, is why each time he try to remove
the symbolic link. What is the purpose of this statement, in overall context of 
As Tim pointed out, the purpose is not to overwrite the content of the file the 
link points to.
If README was a regular file and then you passed "-O README", it's okay to 
overwrite it (I don't
know what's Wget default behavior here, if it prompts the user or whatever), 
because the user is supposed
to be aware of such action. But if README was a symlink, passing "-O README" 
could be a malicious
action, as Angel said. If you want an example of such an action and its 
google for "Symlink race".

That was here, because that was a feature, and now a bug, because some others 
statements was removed ?

If for example I have a symbolic link README in local, and try to download 
another file, with the
same name README remotely, with -O foo, normally, my symbolic link README 
should not be modified.
Exactly. Looking at the code, my guess is that the person who wrote it didn't 
take into account that
the user could have passed the "-O" option (or maybe it wasn't yet implemented 
then, who knows). He or she
just picked the name of the downloaded file.
The -O option already existed in d5be8ecc (and probably in Geturl, too).

But now if I pass -O README, the symbolic link will be removed because it's a 
redirection ?
so It's not possible to just renamed it ?
It sounds like that's exactly what should be done. Treat the symlink as if it 
was a local file: if a symlink
exists with the same name as the downloaded file, rename the downloaded file to 
README.1, for instance.
Actually, instead of _renaming_ it, you should just create it with the right name.

Sorry if my questions are silly, but I'am starting in the code of wget, and my 
knowledge are weak.
Something this project has taught me is that there's no silly question. It's 
better to ask even though you're
not really sure (and you've made some research on your own before :D) than keep 
quiet and make wrong assumptions by yourself.

+1 Perfectly explained, Ander

Loïc, the interesting thing is that the rest of us don't really know why things where done that way, either. That piece of code has been there since the first svn revision, in 1999 (wget 1.5.3) and very few people contributing back then are still active nowadays. Moreover, much more difficult than being "there" is to remember exactly why it was added!

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