Commit 59f69721 authored by Paul Eggert's avatar Paul Eggert
Browse files

Use explicit_bzero to clear GnuTLS keys

* admin/merge-gnulib (GNULIB_MODULES): Add explicit_bzero.
* lib/explicit_bzero.c, m4/explicit_bzero.m4: New files.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/gnutls.c (clear_storage): New function.
(gnutls_symmetric_aead): Use it instead of memset.
parent 252444aa
......@@ -30,7 +30,7 @@ GNULIB_MODULES='
careadlinkat close-stream
count-leading-zeros count-one-bits count-trailing-zeros
crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512
diffseq dtoastr dtotimespec dup2 environ execinfo faccessat
diffseq dtoastr dtotimespec dup2 environ execinfo explicit_bzero faccessat
fcntl fcntl-h fdatasync fdopendir
filemode filevercmp flexmember fstatat fsync
getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog
......
/* Erasure of sensitive data, generic implementation.
Copyright (C) 2016-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
/* An assembler implementation of explicit_bzero can be created as an
assembler alias of an optimized bzero implementation.
Architecture-specific implementations also need to define
__explicit_bzero_chk. */
#if !_LIBC
# include <config.h>
#endif
#include <string.h>
/* glibc-internal users use __explicit_bzero_chk, and explicit_bzero
redirects to that. */
#undef explicit_bzero
/* Set LEN bytes of S to 0. The compiler will not delete a call to
this function, even if S is dead after the call. */
void
explicit_bzero (void *s, size_t len)
{
#ifdef HAVE_EXPLICIT_MEMSET
explicit_memset (s, 0, len);
#else
memset (s, '\0', len);
# ifdef __GNUC__
/* Compiler barrier. */
asm volatile ("" ::: "memory");
# endif
#endif
}
......@@ -21,7 +21,7 @@
# the same distribution terms as the rest of that program.
#
# Generated by gnulib-tool.
# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stat --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=tzset --avoid=unsetenv --avoid=utime --avoid=utime-h --gnu-make --makefile-name=gnulib.mk.in --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 diffseq dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr minmax mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unlocked-io update-copyright utimens vla warnings
# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stat --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=tzset --avoid=unsetenv --avoid=utime --avoid=utime-h --gnu-make --makefile-name=gnulib.mk.in --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 diffseq dtoastr dtotimespec dup2 environ execinfo explicit_bzero faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr minmax mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unlocked-io update-copyright utimens vla warnings
MOSTLYCLEANFILES += core *.stackdump
......@@ -1358,6 +1358,17 @@ EXTRA_libgnu_a_SOURCES += execinfo.c
endif
## end gnulib module execinfo
## begin gnulib module explicit_bzero
ifeq (,$(OMIT_GNULIB_MODULE_explicit_bzero))
EXTRA_DIST += explicit_bzero.c
EXTRA_libgnu_a_SOURCES += explicit_bzero.c
endif
## end gnulib module explicit_bzero
## begin gnulib module faccessat
ifeq (,$(OMIT_GNULIB_MODULE_faccessat))
......
dnl Copyright 2017 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
AC_DEFUN([gl_FUNC_EXPLICIT_BZERO],
[
AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
dnl Persuade glibc <string.h> to declare explicit_bzero.
AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
AC_CHECK_FUNCS_ONCE([explicit_bzero])
if test $ac_cv_func_explicit_bzero = no; then
HAVE_EXPLICIT_BZERO=0
fi
])
AC_DEFUN([gl_PREREQ_EXPLICIT_BZERO],
[
AC_CHECK_FUNCS([explicit_memset])
])
......@@ -72,6 +72,7 @@ AC_DEFUN([gl_EARLY],
# Code from module errno:
# Code from module euidaccess:
# Code from module execinfo:
# Code from module explicit_bzero:
# Code from module extensions:
# Code from module extern-inline:
# Code from module faccessat:
......@@ -210,6 +211,12 @@ AC_DEFUN([gl_INIT],
gl_UNISTD_MODULE_INDICATOR([environ])
gl_HEADER_ERRNO_H
gl_EXECINFO_H
gl_FUNC_EXPLICIT_BZERO
if test $HAVE_EXPLICIT_BZERO = 0; then
AC_LIBOBJ([explicit_bzero])
gl_PREREQ_EXPLICIT_BZERO
fi
gl_STRING_MODULE_INDICATOR([explicit_bzero])
AC_REQUIRE([gl_EXTERN_INLINE])
gl_FUNC_FACCESSAT
if test $HAVE_FACCESSAT = 0; then
......@@ -837,6 +844,7 @@ AC_DEFUN([gl_FILE_LIST], [
lib/euidaccess.c
lib/execinfo.c
lib/execinfo.in.h
lib/explicit_bzero.c
lib/faccessat.c
lib/fcntl.c
lib/fcntl.in.h
......@@ -967,6 +975,7 @@ AC_DEFUN([gl_FILE_LIST], [
m4/errno_h.m4
m4/euidaccess.m4
m4/execinfo.m4
m4/explicit_bzero.m4
m4/extensions.m4
m4/extern-inline.m4
m4/faccessat.m4
......
......@@ -1883,6 +1883,22 @@ The alist key is the cipher name. */)
return ciphers;
}
/* Zero out STORAGE (even if it will become inaccessible. It has
STORAGE_LENGTH bytes. The goal is to improve security a bit, in
case an Emacs module or some buggy part of Emacs attempts to
inspect STORAGE later to retrieve a secret.
Calls to this function document when storage containing a secret is
known to go out of scope. This function is not guaranteed to erase
the secret, as copies of STORAGE may well be accessible elsewhere
on the machine. */
static void
clear_storage (void *storage, ptrdiff_t storage_length)
{
explicit_bzero (storage, storage_length);
}
static Lisp_Object
gnutls_symmetric_aead (bool encrypting, gnutls_cipher_algorithm_t gca,
Lisp_Object cipher,
......@@ -1949,7 +1965,7 @@ gnutls_symmetric_aead (bool encrypting, gnutls_cipher_algorithm_t gca,
if (ret < GNUTLS_E_SUCCESS)
{
memset (storage, 0, storage_length);
clear_storage (storage, storage_length);
SAFE_FREE ();
gnutls_aead_cipher_deinit (acipher);
if (encrypting)
......@@ -1963,7 +1979,7 @@ gnutls_symmetric_aead (bool encrypting, gnutls_cipher_algorithm_t gca,
gnutls_aead_cipher_deinit (acipher);
Lisp_Object output = make_unibyte_string (storage, storage_length);
memset (storage, 0, storage_length);
clear_storage (storage, storage_length);
SAFE_FREE ();
return list2 (output, actual_iv);
#else
......
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