Re: [exim-dev] fopen(), umask, and file permissions

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Author: Wakko Warner
Date:  
To: exim-dev
Subject: Re: [exim-dev] fopen(), umask, and file permissions
Philip Hazel wrote:
> + FILE *
> + modefopen(uschar *filename, char *options, mode_t mode)
> + {
> + FILE *f;
> + umask(0777);
> + f = Ufopen(filename, options);
> + umask(0);
> + if (f != NULL) (void)fchmod(fileno(f), mode);
> + return f;
> + }


Is it possible this could be a slight security concern?

You're creating a file with mode 777 and later chmodding it.

I don't know the code that uses fopen, but it could also be possible that a
file that already exsists with a specific mode gets it's mode clobbered.

One could use open(2) then fdopen(3), but again, I don't know the code well
enough to know for sure.

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