Date: Mon, 24 Mar 2003 19:18:45 +0100 (CET) From: sigsegv@login.kvalito.no (Jan-Espen Pettersen) To: blueeskimo@gmx.net Cc: questions@freebsd.org, tony@idk.com Subject: Re: Generating passwords Message-ID: <20030324181845.AE4EA1276E0@login.kvalito.no>
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On Monday 24 March 2003 07:24, you wrote:
> On Mon, 2003-03-24 at 00:04, Jan-Espen Pettersen wrote:
> > This C program will generate random passwords.
> > ...
> > int main()
> > {
> > int min_lenght = 8;
> > int max_lenght = 30;
> > int a;
> > long int b;
> > char *c =
> > "-abcdefghijklmnopqrstuvwxyz-ABCDEFGHIJKLMNOPQRSTUVWXYZ---_/*+1234567890!
> >#---1234567890-"; char *d;
> > long int e;
> > srandomdev();
> > e = random();
> > e = min_lenght + (e % ((max_lenght - min_lenght) + 1));
> > printf("lenght=%d\n", e);
> > e++;
> > d = (char *) malloc(e);
> > e--;
> > d[e] = 0;
> > a = 0;
> > while (a < e)
> > {
> > b = random();
> > b = b % strlen(c);
> > d[a] = c[b];
> > a++;
> > };
> > printf("password=\"%s\"\n", d);
> > };
>
> I have a few issues with this code ..
> a) You never free() your malloc'ed memory
>
> b) You shouldn't call strlen(c) every time you iterate through the
> while() loop (since 'c' isn't changing). Set this length in a variable
> before the while loop, then make use of that variable. This could even
> be a #define, since the string is hard-coded.
>
> c) I'm not sure this is completely portable: d[e] = 0;
> Just in case, I'd suggest: d[e] = '\0';
>
> d) Combine these two lines:
> b = random();
> b = b % strlen(c);
> --> b = random() % len; // using 'len' variable as I mentioned before.
>
> e) You never return from main(). Some compilers will be very unhappy
> about this. Better to be explicit.
>
> f) You don't check the return value of malloc(). This should be a
> no-brainer. *Always* check the return value of malloc/calloc, no matter
> how little memory you are requesting.
Oops, sorry, that program was only a program I wrote relly fast for internal use only. for a very long while ago. I should have checked it for that type of warnings/errors/bad code.
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