[TUHS] buffer overflow (Re: Happy birthday Morris worm

Warner Losh imp at bsdimp.com
Wed Nov 13 09:22:44 AEST 2019

On Tue, Nov 12, 2019 at 3:54 PM Dave Horsfall <dave at horsfall.org> wrote:

> On Tue, 12 Nov 2019, Bakul Shah wrote:
> > Unfortunately strcpy & other buffer overflow friendly functions are
> > still present in the C standard (I am looking at n2434.pdf, draft of
> > Sept 25, 2019). Is C really not fixable?
> No; POSIX requires all sorts of broken functions be present, otherwise it
> is not compliant; heck, last I looked it even requires gets().  And let's
> not even mention pointers...  We are our own worst enemy.[*]

POSIX can't even recognize that leap seconds exist :(

> All is not lost, though; use strncpy() instead of strcpy() etc.  These
> days my first choice is Perl, despite it being bloated (I only use C if
> it's trivial or I need the speed).  I must look at Ruby, though...

strncpy has two issues. First, it doesn't guarantee NUL termination.
Second, it always writes N bytes. It's for a fixed width data field, not a
variable length string whose buffer size is known. strlcpy is much better,
but still has some issues...

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