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

Steffen Nurpmeso steffen at sdaoden.eu
Fri Nov 22 07:48:44 AEST 2019

Dave Horsfall wrote in <alpine.BSF.2.21.9999.1911220658250.33542 at aneurin\
 |On Tue, 19 Nov 2019, Tony Finch wrote:
 |> Amusingly POSIX says the C standard takes precedence wrt the details of 
 |> gets() (and other library functions) and C18 abolished gets(). I'm 
 |> slightly surprised that the POSIX committee didn't see that coming and 
 |> include the change in the 2018 edition...

This week (on the 19th, to be exact) Geoff Clare made official the
desire to align a forthcoming POSIX Issue 8 with ISO C17.
Current POSIX (1003.1(2016)/Issue7+TC2) still aligns with C99.

And, compared to C99, the POSIX wording causes sympathy

37022         Reading a line that overflows the array pointed to by s results in undefined behavior. The use of
37023         fgets( ) is recommended.
37024               Since the user cannot specify the length of the buffer passed to gets( ), use of this function is
37025               discouraged. The length of the string read is unlimited. It is possible to overflow this buffer in
37026               such a way as to cause applications to fail, or possible system security violations.
37027               Applications should use the fgets( ) function instead of the obsolescent gets( ) function.
37029         The standard developers decided to mark the gets( ) function as obsolescent even though it is in
37030         the ISO C standard due to the possibility of buffer overflow.
37032         The gets( ) function may be removed in a future version.

 |Didn't know that gets() had finally been abolished; it's possibly the most 
 |unsafe function (OK, macro) on the planet.  I've long been tempted to 
 |remove gets() and see what breaks...

It seems to have been removed in C 2011, except get_s(), which is
still present in the C 2017 draft that i have.  (I have never used
any of the _s() functions.)

|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)

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