NOMBRE

       bzero explicit_bzero - escribe bytes cero

BIBLIOTECA

       Biblioteca Estándar C (libc, -lc)

SINOPSIS

       #include <strings.h>

       void bzero(void s[.n], size_t n);

       #include <string.h>

       void explicit_bzero(void s[.n], size_t n);

DESCRIPCIÓN

       The  bzero()   function  erases  the  data  in  the  n bytes of the memory starting at the
       location pointed to by s, by writing zeros (bytes containing '\0') to that area.

       The explicit_bzero()  function performs the same task as bzero().  It differs from bzero()
       in  that  it guarantees that compiler optimizations will not remove the erase operation if
       the compiler deduces that the operation is "unnecessary".

VALOR DEVUELTO

       Ninguna.

VERSIONES

       explicit_bzero() apareció por primera vez en la versión 2.25 de glibc.

ATRIBUTOS

       Para obtener una explicación de los términos usados en esta sección, véase attributes(7).

       ┌────────────────────────────────────────────────┬────────────────────┬───────────────────┐
       │Interfaz                                        │ Atributo           │ Valor             │
       ├────────────────────────────────────────────────┼────────────────────┼───────────────────┤
       │bzero(), explicit_bzero()                       │ Seguridad del hilo │ Multi-hilo seguro │
       └────────────────────────────────────────────────┴────────────────────┴───────────────────┘

ESTÁNDARES

       The bzero()  function is deprecated (marked as LEGACY in POSIX.1-2001); use memset(3)   in
       new  programs.   POSIX.1-2008 removes the specification of bzero().  The bzero()  function
       first appeared in 4.3BSD.

       La función explicit_bzero() es una extensión no estándar  presente  también  algunos  BSD.
       Otras  implementaciones  incluyen  funciones  similares  tales  como  memset_explicit()  o
       memset_s().

NOTAS

       The explicit_bzero()  function addresses a problem  that  security-conscious  applications
       may run into when using bzero(): if the compiler can deduce that the location to be zeroed
       will never again be touched by a correct program, then it may  remove  the  bzero()   call
       altogether.   This  is a problem if the intent of the bzero()  call was to erase sensitive
       data (e.g., passwords)  to prevent  the  possibility  that  the  data  was  leaked  by  an
       incorrect  or compromised program.  Calls to explicit_bzero()  are never optimized away by
       the compiler.

       La función explicit_bzero() no resuelve todos los problemas relacionados con el borrado de
       información sensible:

       •  The  explicit_bzero()   function  does  not guarantee that sensitive data is completely
          erased from memory.  (The same is true of bzero().)  For example, there may  be  copies
          of the sensitive data in a register and in "scratch" stack areas.  The explicit_bzero()
          function is not aware of these copies, and can't erase them.

       •  In some circumstances,  explicit_bzero()   can  decrease  security.   If  the  compiler
          determined  that  the  variable  containing the sensitive data could be optimized to be
          stored in a register (because it is small enough to fit in a register, and no operation
          other  than the explicit_bzero()  call would need to take the address of the variable),
          then the explicit_bzero()  call will force the data to be copied from the register to a
          location in RAM that is then immediately erased (while the copy in the register remains
          unaffected).  The problem here is that data in RAM is more likely to be  exposed  by  a
          bug  than  data in a register, and thus the explicit_bzero()  call creates a brief time
          window where the sensitive data is more vulnerable than it would otherwise have been if
          no attempt had been made to erase the data.

       Note  that declaring the sensitive variable with the volatile qualifier does not eliminate
       the above problems.  Indeed, it will make them worse, since, for example, it may  force  a
       variable that would otherwise have been optimized into a register to instead be maintained
       in (more vulnerable)  RAM for its entire lifetime.

       Notwithstanding  the   above   details,   for   security-conscious   applications,   using
       explicit_bzero()    is   generally   preferable  to  not  using  it.   The  developers  of
       explicit_bzero()    anticipate   that   future   compilers   will   recognize   calls   to
       explicit_bzero()   and  take  steps  to  ensure  that all copies of the sensitive data are
       erased, including copies in registers or in "scratch" stack areas.

VÉASE TAMBIÉN

       bstring(3), memset(3), swab(3)

TRADUCCIÓN

       La traducción al español de esta página del  manual  fue  creada  por  Sebastian  Desimone
       <chipy@argenet.com.ar>,   Cesar   D.  Lobejon  <cesar@alien.mec.es>,  Miguel  Pérez  Ibars
       <mpi79470@alu.um.es> y Marcos Fouces <marcos@debian.org>

       Esta traducción es documentación libre; lea  la  GNU  General  Public  License  Version  3
       ⟨https://www.gnu.org/licenses/gpl-3.0.html⟩  o posterior con respecto a las condiciones de
       copyright.  No existe NINGUNA RESPONSABILIDAD.

       Si encuentra algún error en la traducción de esta  página  del  manual,  envíe  un  correo
       electrónico a ⟨debian-l10n-spanish@lists.debian.org⟩.