From 3e8fc7d9f21329d5a98ec3cf6de138bce9bc2c05 Mon Sep 17 00:00:00 2001 From: Yaakov Selkowitz Date: Mon, 27 Nov 2017 23:07:10 -0600 Subject: [PATCH] ssp: add Object Size Checking common code The Object Size Checking (-D_FORTIFY_SOURCE=*) functionality provides wrappers around functions suspectible to buffer overflows. While independent from Stack Smashing Protection (-fstack-protector*), they are often used and implemented together. While GCC also provides an implementation in libssp, it is completely broken (CVE-2016-4973, RHBZ#1324759) and seemingly unfixable, as there is no reliable way for a preprocessor macro to trigger a link flag. Therefore, adding this here is necessary to make it work. Note that this does require building gcc with --disable-libssp and gcc_cv_libc_provides_ssp=yes. Signed-off-by: Yaakov Selkowitz --- newlib/libc/include/ssp/ssp.h | 77 ++++++++++++++++++++++++++++++ newlib/libc/include/sys/features.h | 18 ++++++- newlib/libc/ssp/chk_fail.c | 13 +++++ 3 files changed, 107 insertions(+), 1 deletion(-) create mode 100644 newlib/libc/include/ssp/ssp.h create mode 100644 newlib/libc/ssp/chk_fail.c diff --git a/newlib/libc/include/ssp/ssp.h b/newlib/libc/include/ssp/ssp.h new file mode 100644 index 000000000..5c65cf4b2 --- /dev/null +++ b/newlib/libc/include/ssp/ssp.h @@ -0,0 +1,77 @@ +/* $NetBSD: ssp.h,v 1.13 2015/09/03 20:43:47 plunky Exp $ */ + +/*- + * Copyright (c) 2006, 2011 The NetBSD Foundation, Inc. + * All rights reserved. + * + * This code is derived from software contributed to The NetBSD Foundation + * by Christos Zoulas. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS + * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED + * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR + * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS + * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ +#ifndef _SSP_SSP_H_ +#define _SSP_SSP_H_ + +#include + +/* __ssp_real is used by the implementation in libc */ +#if __SSP_FORTIFY_LEVEL == 0 +#define __ssp_real_(fun) fun +#else +#define __ssp_real_(fun) __ssp_real_ ## fun +#endif +#define __ssp_real(fun) __ssp_real_(fun) + +#define __ssp_inline extern __inline__ __attribute__((__always_inline__, __gnu_inline__)) + +#define __ssp_bos(ptr) __builtin_object_size(ptr, __SSP_FORTIFY_LEVEL > 1) +#define __ssp_bos0(ptr) __builtin_object_size(ptr, 0) + +#define __ssp_check(buf, len, bos) \ + if (bos(buf) != (size_t)-1 && len > bos(buf)) \ + __chk_fail() +#define __ssp_decl(rtype, fun, args) \ +rtype __ssp_real_(fun) args __asm__(__ASMNAME(#fun)); \ +__ssp_inline rtype fun args __asm__(__ASMNAME("__ssp_protected_" #fun)); \ +__ssp_inline rtype fun args +#define __ssp_redirect_raw(rtype, fun, args, call, cond, bos) \ +__ssp_decl(rtype, fun, args) \ +{ \ + if (cond) \ + __ssp_check(__buf, __len, bos); \ + return __ssp_real_(fun) call; \ +} + +#define __ssp_redirect(rtype, fun, args, call) \ + __ssp_redirect_raw(rtype, fun, args, call, 1, __ssp_bos) +#define __ssp_redirect0(rtype, fun, args, call) \ + __ssp_redirect_raw(rtype, fun, args, call, 1, __ssp_bos0) + +#define __ssp_overlap(a, b, l) \ + (((a) <= (b) && (b) < (a) + (l)) || ((b) <= (a) && (a) < (b) + (l))) + +__BEGIN_DECLS +void __stack_chk_fail(void) __dead2; +void __chk_fail(void) __dead2; +__END_DECLS + +#endif /* _SSP_SSP_H_ */ diff --git a/newlib/libc/include/sys/features.h b/newlib/libc/include/sys/features.h index 95d20533e..2900b332f 100644 --- a/newlib/libc/include/sys/features.h +++ b/newlib/libc/include/sys/features.h @@ -100,6 +100,9 @@ extern "C" { * _SVID_SOURCE (deprecated by _DEFAULT_SOURCE) * _DEFAULT_SOURCE (or none of the above) * POSIX-1.2008 with BSD and SVr4 extensions + * + * _FORTIFY_SOURCE = 1 or 2 + * Object Size Checking function wrappers */ #ifdef _GNU_SOURCE @@ -233,9 +236,11 @@ extern "C" { * __GNU_VISIBLE * GNU extensions; enabled with _GNU_SOURCE. * + * __SSP_FORTIFY_LEVEL + * Object Size Checking; defined to 0 (off), 1, or 2. + * * In all cases above, "enabled by default" means either by defining * _DEFAULT_SOURCE, or by not defining any of the public feature test macros. - * Defining _GNU_SOURCE makes all of the above avaliable. */ #ifdef _ATFILE_SOURCE @@ -314,6 +319,17 @@ extern "C" { #define __XSI_VISIBLE 0 #endif +#if _FORTIFY_SOURCE > 0 && !defined(__cplusplus) && !defined(__lint__) && \ + (__OPTIMIZE__ > 0 || defined(__clang__)) && __GNUC_PREREQ__(4, 1) +# if _FORTIFY_SOURCE > 1 +# define __SSP_FORTIFY_LEVEL 2 +# else +# define __SSP_FORTIFY_LEVEL 1 +# endif +#else +# define __SSP_FORTIFY_LEVEL 0 +#endif + /* RTEMS adheres to POSIX -- 1003.1b with some features from annexes. */ #ifdef __rtems__ diff --git a/newlib/libc/ssp/chk_fail.c b/newlib/libc/ssp/chk_fail.c new file mode 100644 index 000000000..b1f8e42a6 --- /dev/null +++ b/newlib/libc/ssp/chk_fail.c @@ -0,0 +1,13 @@ +#include +#include +#include + +void +__attribute__((__noreturn__)) +__chk_fail(void) +{ + char msg[] = "*** buffer overflow detected ***: terminated\n"; + write (2, msg, strlen (msg)); + raise (SIGABRT); + _exit (127); +}