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| author | Zack Weinberg <zackw@panix.com> | 2016-09-15 07:29:44 -0400 |
|---|---|---|
| committer | Zack Weinberg <zackw@panix.com> | 2016-12-16 16:21:54 -0500 |
| commit | ea1bd74defcf9d5291d14972e63105168ca9eb4f (patch) | |
| tree | 98e2a212f799a95dd8c2976448d4d492a07c716b | |
| parent | c0b4353654e635e280ec0c1972f251bf696abb36 (diff) | |
| download | glibc-ea1bd74defcf9d5291d14972e63105168ca9eb4f.tar.xz glibc-ea1bd74defcf9d5291d14972e63105168ca9eb4f.zip | |
New string function explicit_bzero (from OpenBSD).
explicit_bzero(s, n) is the same as memset(s, 0, n), except that the
compiler is not allowed to delete a call to explicit_bzero even if the
memory pointed to by 's' is dead after the call. Right now, this effect
is achieved externally by having explicit_bzero be a function whose
semantics are unknown to the compiler, and internally, with a no-op
asm statement that clobbers memory. This does mean that small
explicit_bzero operations cannot be expanded inline as small memset
operations can, but on the other hand, small memset operations do get
deleted by the compiler. Hopefully full compiler support for
explicit_bzero will happen relatively soon.
There are two new tests: test-explicit_bzero.c verifies the
visible semantics in the same way as the existing test-bzero.c,
and tst-xbzero-opt.c verifies the not-being-optimized-out property.
The latter is conceptually based on a test written by Matthew Dempsky
for the OpenBSD regression suite.
The crypt() implementation has an immediate use for this new feature.
We avoid having to add a GLIBC_PRIVATE alias for explicit_bzero
by running all of libcrypt's calls through the fortified variant,
__explicit_bzero_chk, which is in the impl namespace anyway. Currently
I'm not aware of anything in libc proper that needs this, but the
glue is all in place if it does become necessary. The legacy DES
implementation wasn't bothering to clear its buffers, so I added that,
mostly for consistency's sake.
* string/explicit_bzero.c: New routine.
* string/test-explicit_bzero.c, string/tst-xbzero-opt.c: New tests.
* string/Makefile (routines, strop-tests, tests): Add them.
* string/test-memset.c: Add ifdeffage for testing explicit_bzero.
* string/string.h [__USE_MISC]: Declare explicit_bzero.
* debug/explicit_bzero_chk.c: New routine.
* debug/Makefile (routines): Add it.
* debug/tst-chk1.c: Test fortification of explicit_bzero.
* string/bits/string3.h: Fortify explicit_bzero.
* manual/string.texi: Document explicit_bzero.
* NEWS: Mention addition of explicit_bzero.
* crypt/crypt-entry.c (__crypt_r): Clear key-dependent intermediate
data before returning, using explicit_bzero.
* crypt/md5-crypt.c (__md5_crypt_r): Likewise.
* crypt/sha256-crypt.c (__sha256_crypt_r): Likewise.
* crypt/sha512-crypt.c (__sha512_crypt_r): Likewise.
* include/string.h: Redirect internal uses of explicit_bzero
to __explicit_bzero_chk[_internal].
* string/Versions [GLIBC_2.25]: Add explicit_bzero.
* debug/Versions [GLIBC_2.25]: Add __explicit_bzero_chk.
* sysdeps/arm/nacl/libc.abilist
* sysdeps/unix/sysv/linux/aarch64/libc.abilist
* sysdeps/unix/sysv/linux/alpha/libc.abilist
* sysdeps/unix/sysv/linux/arm/libc.abilist
* sysdeps/unix/sysv/linux/hppa/libc.abilist
* sysdeps/unix/sysv/linux/i386/libc.abilist
* sysdeps/unix/sysv/linux/ia64/libc.abilist
* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
* sysdeps/unix/sysv/linux/microblaze/libc.abilist
* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
* sysdeps/unix/sysv/linux/nios2/libc.abilist
* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
* sysdeps/unix/sysv/linux/sh/libc.abilist
* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
* sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist:
Add entries for explicit_bzero and __explicit_bzero_chk.
49 files changed, 711 insertions, 22 deletions
@@ -1,3 +1,62 @@ +2016-12-16 Zack Weinberg <zackw@panix.com> + Florian Weimer <fweimer@redhat.com> + Nick Mathewson <nickm@torproject.org> + + * string/explicit_bzero.c: New routine. + * string/test-explicit_bzero.c, string/tst-xbzero-opt.c: New tests. + * string/Makefile (routines, strop-tests, tests): Add them. + * string/test-memset.c: Add ifdeffage for testing explicit_bzero. + * string/string.h [__USE_MISC]: Declare explicit_bzero. + + * debug/explicit_bzero_chk.c: New routine. + * debug/Makefile (routines): Add it. + * debug/tst-chk1.c: Test fortification of explicit_bzero. + * string/bits/string3.h: Fortify explicit_bzero. + + * manual/string.texi: Document explicit_bzero. + * NEWS: Mention addition of explicit_bzero. + + * crypt/crypt-entry.c (__crypt_r): Clear key-dependent intermediate + data before returning, using explicit_bzero. + * crypt/md5-crypt.c (__md5_crypt_r): Likewise. + * crypt/sha256-crypt.c (__sha256_crypt_r): Likewise. + * crypt/sha512-crypt.c (__sha512_crypt_r): Likewise. + + * include/string.h: Redirect internal uses of explicit_bzero + to __explicit_bzero_chk[_internal]. + * string/Versions [GLIBC_2.25]: Add explicit_bzero. + * debug/Versions [GLIBC_2.25]: Add __explicit_bzero_chk. + * sysdeps/arm/nacl/libc.abilist + * sysdeps/unix/sysv/linux/aarch64/libc.abilist + * sysdeps/unix/sysv/linux/alpha/libc.abilist + * sysdeps/unix/sysv/linux/arm/libc.abilist + * sysdeps/unix/sysv/linux/hppa/libc.abilist + * sysdeps/unix/sysv/linux/i386/libc.abilist + * sysdeps/unix/sysv/linux/ia64/libc.abilist + * sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist + * sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist + * sysdeps/unix/sysv/linux/microblaze/libc.abilist + * sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist + * sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist + * sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist + * sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist + * sysdeps/unix/sysv/linux/nios2/libc.abilist + * sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist + * sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist + * sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist + * sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist + * sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist + * sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist + * sysdeps/unix/sysv/linux/sh/libc.abilist + * sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist + * sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist + * sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist + * sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist + * sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist + * sysdeps/unix/sysv/linux/x86_64/64/libc.abilist + * sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist: + Add entries for explicit_bzero and __explicit_bzero_chk. + 2016-12-16 Joseph Myers <joseph@codesourcery.com> * math/fenv.h @@ -84,6 +84,12 @@ Version 2.25 * The functions strfromd, strfromf, and strfroml, from ISO/IEC TS 18661-1:2014, are added to libc. They convert a floating-point number into string. +* The function explicit_bzero, from OpenBSD, has been added to libc. It is + intended to be used instead of memset() to erase sensitive data after use; + the compiler will not optimize out calls to explicit_bzero even if they + are "unnecessary" (in the sense that no _correct_ program can observe the + effects of the memory clear). + * On ColdFire, MicroBlaze, Nios II and SH3, the float_t type is now defined to float instead of double. This does not affect the ABI of any libraries that are part of the GNU C Library, but may affect the ABI of other diff --git a/crypt/crypt-entry.c b/crypt/crypt-entry.c index a7dfccaa36..23e776fb9e 100644 --- a/crypt/crypt-entry.c +++ b/crypt/crypt-entry.c @@ -141,6 +141,15 @@ __crypt_r (const char *key, const char *salt, * And convert back to 6 bit ASCII */ _ufc_output_conversion_r (res[0], res[1], salt, data); + + /* + * Erase key-dependent intermediate data. Data dependent only on + * the salt is not considered sensitive. + */ + explicit_bzero (ktab, sizeof (ktab)); + explicit_bzero (data->keysched, sizeof (data->keysched)); + explicit_bzero (res, sizeof (res)); + return data->crypt_3_buf; } weak_alias (__crypt_r, crypt_r) diff --git a/crypt/md5-crypt.c b/crypt/md5-crypt.c index 2243bc7aed..6125c7f7f2 100644 --- a/crypt/md5-crypt.c +++ b/crypt/md5-crypt.c @@ -288,13 +288,13 @@ __md5_crypt_r (const char *key, const char *salt, char *buffer, int buflen) #ifndef USE_NSS __md5_init_ctx (&ctx); __md5_finish_ctx (&ctx, alt_result); - memset (&ctx, '\0', sizeof (ctx)); - memset (&alt_ctx, '\0', sizeof (alt_ctx)); + explicit_bzero (&ctx, sizeof (ctx)); + explicit_bzero (&alt_ctx, sizeof (alt_ctx)); #endif if (copied_key != NULL) - memset (copied_key, '\0', key_len); + explicit_bzero (copied_key, key_len); if (copied_salt != NULL) - memset (copied_salt, '\0', salt_len); + explicit_bzero (copied_salt, salt_len); free (free_key); return buffer; diff --git a/crypt/sha256-crypt.c b/crypt/sha256-crypt.c index d768234879..8c670ea405 100644 --- a/crypt/sha256-crypt.c +++ b/crypt/sha256-crypt.c @@ -371,16 +371,16 @@ __sha256_crypt_r (const char *key, const char *salt, char *buffer, int buflen) #ifndef USE_NSS __sha256_init_ctx (&ctx); __sha256_finish_ctx (&ctx, alt_result); - memset (&ctx, '\0', sizeof (ctx)); - memset (&alt_ctx, '\0', sizeof (alt_ctx)); + explicit_bzero (&ctx, sizeof (ctx)); + explicit_bzero (&alt_ctx, sizeof (alt_ctx)); #endif - memset (temp_result, '\0', sizeof (temp_result)); - memset (p_bytes, '\0', key_len); - memset (s_bytes, '\0', salt_len); + explicit_bzero (temp_result, sizeof (temp_result)); + explicit_bzero (p_bytes, key_len); + explicit_bzero (s_bytes, salt_len); if (copied_key != NULL) - memset (copied_key, '\0', key_len); + explicit_bzero (copied_key, key_len); if (copied_salt != NULL) - memset (copied_salt, '\0', salt_len); + explicit_bzero (copied_salt, salt_len); free (free_key); free (free_pbytes); diff --git a/crypt/sha512-crypt.c b/crypt/sha512-crypt.c index f404c88b20..dac145b2e9 100644 --- a/crypt/sha512-crypt.c +++ b/crypt/sha512-crypt.c @@ -393,16 +393,16 @@ __sha512_crypt_r (const char *key, const char *salt, char *buffer, int buflen) #ifndef USE_NSS __sha512_init_ctx (&ctx); __sha512_finish_ctx (&ctx, alt_result); - memset (&ctx, '\0', sizeof (ctx)); - memset (&alt_ctx, '\0', sizeof (alt_ctx)); + explicit_bzero (&ctx, sizeof (ctx)); + explicit_bzero (&alt_ctx, sizeof (alt_ctx)); #endif - memset (temp_result, '\0', sizeof (temp_result)); - memset (p_bytes, '\0', key_len); - memset (s_bytes, '\0', salt_len); + explicit_bzero (temp_result, sizeof (temp_result)); + explicit_bzero (p_bytes, key_len); + explicit_bzero (s_bytes, salt_len); if (copied_key != NULL) - memset (copied_key, '\0', key_len); + explicit_bzero (copied_key, key_len); if (copied_salt != NULL) - memset (copied_salt, '\0', salt_len); + explicit_bzero (copied_salt, salt_len); free (free_key); free (free_pbytes); diff --git a/debug/Makefile b/debug/Makefile index 6b5f31e4f6..84d3f92c0d 100644 --- a/debug/Makefile +++ b/debug/Makefile @@ -48,6 +48,7 @@ routines = backtrace backtracesyms backtracesymsfd noophooks \ vdprintf_chk obprintf_chk \ longjmp_chk ____longjmp_chk \ fdelt_chk poll_chk ppoll_chk \ + explicit_bzero_chk \ stack_chk_fail fortify_fail \ $(static-only-routines) static-only-routines := warning-nop stack_chk_fail_local diff --git a/debug/Versions b/debug/Versions index 0482c85f19..a6628db356 100644 --- a/debug/Versions +++ b/debug/Versions @@ -55,6 +55,9 @@ libc { GLIBC_2.16 { __poll_chk; __ppoll_chk; } + GLIBC_2.25 { + __explicit_bzero_chk; + } GLIBC_PRIVATE { __fortify_fail; } diff --git a/debug/explicit_bzero_chk.c b/debug/explicit_bzero_chk.c new file mode 100644 index 0000000000..2e507f8297 --- /dev/null +++ b/debug/explicit_bzero_chk.c @@ -0,0 +1,44 @@ +/* Generic implementation of __explicit_bzero_chk. + Copyright (C) 1991-2016 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Torbjorn Granlund (tege@sics.se). + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Publ |