[PATCH 3/4] Disable lazy binding by default

[Michael Hudson-Doyle]

On Fri, 30 Jun 2023 at 06:42, Siddhesh Poyarekar via Libc-alpha <
libc-alpha@sourceware.org> wrote:

> Lazy binding is a key security feature and is enabled by all major
> distributions by default.


This seems backwards. "Lazy binding prevents some key security features and
is disabled by all major distributions by default"? Or something like that?

Cheers,
mwh


>   Default to this more secure option and flip
> the flag to allow disabling it if needed.
>
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> ---
>  INSTALL             | 10 +++++-----
>  NEWS                |  3 +++
>  configure           |  4 ++--
>  configure.ac        |  6 +++---
>  manual/install.texi |  9 ++++-----
>  5 files changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/INSTALL b/INSTALL
> index f02358e933..88ffe7748f 100644
> --- a/INSTALL
> +++ b/INSTALL
> @@ -205,11 +205,11 @@ if ‘CFLAGS’ is specified it must enable
> optimization.  For example:
>       of routines called directly from assembler are excluded from this
>       protection.  This option is enabled by default and set to ‘strong’.
>
> -‘--enable-bind-now’
> -     Disable lazy binding for installed shared objects and programs.
> -     This provides additional security hardening because it enables full
> -     RELRO and a read-only global offset table (GOT), at the cost of
> -     slightly increased program load times.
> +‘--disable-bind-now’
> +     Enable lazy binding for installed shared objects and programs.
> +     Lazy binding may improve program load times but it will disable
> +     security hardening that enables full RELRO and a read-only global
> +     offset table (GOT).
>
>  ‘--enable-pt_chown’
>       The file ‘pt_chown’ is a helper binary for ‘grantpt’ (*note
> diff --git a/NEWS b/NEWS
> index 47ec0b741c..264fad5d86 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -52,6 +52,9 @@ Major new features:
>    default.  This may be overridden by using the --enable-stack-protector
>    configure option.
>
> +* Lazy binding is now disabled by default and can be overridden with the
> +  --disable-bind-now configure flag.
> +
>  Deprecated and removed features, and other changes affecting
> compatibility:
>
>  * In the Linux kernel for the hppa/parisc architecture some of the
> diff --git a/configure b/configure
> index 863621cabf..6d4b05df18 100755
> --- a/configure
> +++ b/configure
> @@ -1462,7 +1462,7 @@ Optional Features:
>                            hardcode newly built glibc path in tests
>                            [default=no]
>    --disable-hidden-plt    do not hide internal function calls to avoid PLT
> -  --enable-bind-now       disable lazy relocations in DSOs
> +  --disable-bind-now      enable lazy relocations in DSOs
>    --enable-stack-protector=[yes|no|all|strong]
>                            Use -fstack-protector[-all|-strong] to detect
> glibc
>                            buffer overflows
> @@ -4448,7 +4448,7 @@ if test ${enable_bind_now+y}
>  then :
>    enableval=$enable_bind_now; bindnow=$enableval
>  else $as_nop
> -  bindnow=no
> +  bindnow=yes
>  fi
>
>
> diff --git a/configure.ac b/configure.ac
> index d85452b3b3..6fc72df700 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -213,10 +213,10 @@ if test "x$hidden" = xno; then
>  fi
>
>  AC_ARG_ENABLE([bind-now],
> -             AS_HELP_STRING([--enable-bind-now],
> -                            [disable lazy relocations in DSOs]),
> +             AS_HELP_STRING([--disable-bind-now],
> +                            [enable lazy relocations in DSOs]),
>               [bindnow=$enableval],
> -             [bindnow=no])
> +             [bindnow=yes])
>  AC_SUBST(bindnow)
>  if test "x$bindnow" = xyes; then
>    AC_DEFINE(BIND_NOW)
> diff --git a/manual/install.texi b/manual/install.texi
> index b1aa5eb60c..ae43dc51ac 100644
> --- a/manual/install.texi
> +++ b/manual/install.texi
> @@ -231,11 +231,10 @@ options to detect stack overruns.  Only the dynamic
> linker and a small
>  number of routines called directly from assembler are excluded from this
>  protection.  This option is enabled by default and set to @option{strong}.
>
> -@item --enable-bind-now
> -Disable lazy binding for installed shared objects and programs.  This
> -provides additional security hardening because it enables full RELRO
> -and a read-only global offset table (GOT), at the cost of slightly
> -increased program load times.
> +@item --disable-bind-now
> +Enable lazy binding for installed shared objects and programs.  Lazy
> binding
> +may improve program load times but it will disable security hardening that
> +enables full RELRO and a read-only global offset table (GOT).
>
>  @pindex pt_chown
>  @findex grantpt
> --
> 2.41.0
>
>