From beb5d6df5c5785db7c32a24a5d2a351cb964bfbc Mon Sep 17 00:00:00 2001
From: Clemens Lang via Gcrypt-devel <gcrypt-devel@lists.gnupg.org>
Date: Mon, 14 Feb 2022 18:49:59 +0100
Subject: [PATCH] fips: Use ELF header to find hmac file offset
* src/fips.c [ENABLE_HMAC_BINARY_CHECK] (hmac256_check): Use ELF headers
to locate the file offset for the HMAC in addition to information from
the loader
--
The previous method of locating the offset of the .rodata1 section in
the ELF file on disk used information obtained from the loader. This
computed the address of the value in memory at runtime, but the offset
in the file can be different. Specifically, the old code computed
a value relative to ElfW(Phdr).p_vaddr, but the offset in the file is
relative to ElfW(Phdr).p_offset. These values can differ, so the
computed address at runtime must be translated into a file offset
relative to p_offset.
This is largely cosmetic, since the text section that should contain the
HMAC usually has both p_vaddr and p_offset set to 0.
Signed-off-by: Clemens Lang <cllang@redhat.com>
---
README | 3 ++-
src/fips.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 69 insertions(+), 7 deletions(-)
diff --git a/README b/README
index 3b465c1b..4d7697dd 100644
--- a/README
+++ b/README
@@ -157,7 +157,8 @@
--enable-hmac-binary-check
Include support to check the binary at runtime
against a HMAC checksum. This works only in FIPS
- mode and on systems providing the dladdr function.
+ mode on systems providing the dladdr function and using
+ the ELF binary format.
--with-fips-module-version=version
Specify a string used as a module version for FIPS
diff --git a/src/fips.c b/src/fips.c
index 391b94f1..c40274d9 100644
--- a/src/fips.c
+++ b/src/fips.c
@@ -25,6 +25,8 @@
#include <string.h>
#ifdef ENABLE_HMAC_BINARY_CHECK
# include <dlfcn.h>
+# include <elf.h>
+# include <limits.h>
# include <link.h>
#endif
#ifdef HAVE_SYSLOG
@@ -594,6 +596,57 @@ run_random_selftests (void)
static const unsigned char __attribute__ ((section (".rodata1")))
hmac_for_the_implementation[HMAC_LEN];
+/**
+ * Determine the offset of the given virtual address in the ELF file opened as
+ * fp and return it in offset. Rewinds fp to the beginning on success.
+ */
+static gpg_error_t
+get_file_offset (FILE *fp, unsigned long paddr, unsigned long *offset)
+{
+ ElfW (Ehdr) ehdr;
+ ElfW (Phdr) phdr;
+ uint16_t e_phidx;
+
+ // read the ELF header
+ if (0 != fseek (fp, 0, SEEK_SET))
+ return gpg_error_from_syserror ();
+ if (1 != fread (&ehdr, sizeof (ehdr), 1, fp))
+ return gpg_error_from_syserror ();
+
+ // the section header entry size should match the size of the shdr struct
+ if (ehdr.e_phentsize != sizeof (phdr))
+ return gpg_error (GPG_ERR_INV_OBJ);
+ if (ehdr.e_phoff == 0)
+ return gpg_error (GPG_ERR_INV_OBJ);
+
+ // jump to the first program header
+ if (0 != fseek (fp, ehdr.e_phoff, SEEK_SET))
+ return gpg_error_from_syserror ();
+
+ // iterate over the program headers, compare their virtual addresses with the
+ // address we are looking for, and if the program header matches, calculate
+ // the offset of the given paddr in the file using the program header's
+ // p_offset field.
+ for (e_phidx = 0; e_phidx < ehdr.e_phnum; e_phidx++)
+ {
+ if (1 != fread (&phdr, sizeof (phdr), 1, fp))
+ return gpg_error_from_syserror ();
+ if (phdr.p_type == PT_LOAD && phdr.p_vaddr <= paddr
+ && phdr.p_vaddr + phdr.p_memsz > paddr)
+ {
+ // found section, compute the offset of paddr in the file
+ *offset = phdr.p_offset + (paddr - phdr.p_vaddr);
+
+ if (0 != fseek (fp, 0, SEEK_SET))
+ return gpg_error_from_syserror ();
+ return 0;
+ }
+ }
+
+ // section not found in the file
+ return gpg_error (GPG_ERR_INV_OBJ);
+}
+
static gpg_error_t
hmac256_check (const char *filename, const char *key, struct link_map *lm)
{
@@ -603,6 +656,7 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
size_t buffer_size, nread;
char *buffer;
unsigned long paddr;
+ unsigned long offset = 0;
unsigned long off = 0;
paddr = (unsigned long)hmac_for_the_implementation - lm->l_addr;
@@ -611,6 +665,13 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
if (!fp)
return gpg_error (GPG_ERR_INV_OBJ);
+ err = get_file_offset (fp, paddr, &offset);
+ if (err)
+ {
+ fclose (fp);
+ return err;
+ }
+
err = _gcry_md_open (&hd, GCRY_MD_SHA256, GCRY_MD_FLAG_HMAC);
if (err)
{
@@ -651,14 +712,14 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
nread = fread (buffer+HMAC_LEN, 1, buffer_size, fp);
if (nread < buffer_size)
{
- if (off - HMAC_LEN <= paddr && paddr <= off + nread)
- memset (buffer + HMAC_LEN + paddr - off, 0, HMAC_LEN);
+ if (off - HMAC_LEN <= offset && offset <= off + nread)
+ memset (buffer + HMAC_LEN + offset - off, 0, HMAC_LEN);
_gcry_md_write (hd, buffer, nread+HMAC_LEN);
break;
}
- if (off - HMAC_LEN <= paddr && paddr <= off + nread)
- memset (buffer + HMAC_LEN + paddr - off, 0, HMAC_LEN);
+ if (off - HMAC_LEN <= offset && offset <= off + nread)
+ memset (buffer + HMAC_LEN + offset - off, 0, HMAC_LEN);
_gcry_md_write (hd, buffer, nread);
memcpy (buffer, buffer+buffer_size, HMAC_LEN);
off += nread;
@@ -694,8 +755,8 @@ check_binary_integrity (void)
const char *key = KEY_FOR_BINARY_CHECK;
void *extra_info;
- if (!dladdr1 (hmac_for_the_implementation,
- &info, &extra_info, RTLD_DL_LINKMAP))
+ if (!dladdr1 (hmac_for_the_implementation, &info, &extra_info,
+ RTLD_DL_LINKMAP))
err = gpg_error_from_syserror ();
else
err = hmac256_check (info.dli_fname, key, extra_info);
--
2.39.0
From 521500624b4b11538d206137205e2a511dad7072 Mon Sep 17 00:00:00 2001
From: NIIBE Yutaka <gniibe@fsij.org>
Date: Tue, 15 Feb 2022 20:38:02 +0900
Subject: [PATCH] fips: Fix previous commit.
--
Coding style fix.
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
---
src/fips.c | 64 +++++++++++++++++++++++++++---------------------------
1 file changed, 32 insertions(+), 32 deletions(-)
diff --git a/src/fips.c b/src/fips.c
index c40274d9..f16bce8b 100644
--- a/src/fips.c
+++ b/src/fips.c
@@ -596,54 +596,55 @@ run_random_selftests (void)
static const unsigned char __attribute__ ((section (".rodata1")))
hmac_for_the_implementation[HMAC_LEN];
-/**
- * Determine the offset of the given virtual address in the ELF file opened as
- * fp and return it in offset. Rewinds fp to the beginning on success.
+/*
+ * In the ELF file opened as FP, determine the offset of the given
+ * virtual address ADDR and return it in OFFSET. Rewinds FP to the
+ * beginning on success.
*/
static gpg_error_t
-get_file_offset (FILE *fp, unsigned long paddr, unsigned long *offset)
+get_file_offset (FILE *fp, unsigned long addr, unsigned long *offset)
{
ElfW (Ehdr) ehdr;
ElfW (Phdr) phdr;
uint16_t e_phidx;
- // read the ELF header
- if (0 != fseek (fp, 0, SEEK_SET))
+ /* Read the ELF header */
+ if (fseek (fp, 0, SEEK_SET) != 0)
return gpg_error_from_syserror ();
- if (1 != fread (&ehdr, sizeof (ehdr), 1, fp))
+ if (fread (&ehdr, sizeof (ehdr), 1, fp) != 1)
return gpg_error_from_syserror ();
- // the section header entry size should match the size of the shdr struct
+ /* The program header entry size should match the size of the phdr struct */
if (ehdr.e_phentsize != sizeof (phdr))
return gpg_error (GPG_ERR_INV_OBJ);
if (ehdr.e_phoff == 0)
return gpg_error (GPG_ERR_INV_OBJ);
- // jump to the first program header
- if (0 != fseek (fp, ehdr.e_phoff, SEEK_SET))
+ /* Jump to the first program header */
+ if (fseek (fp, ehdr.e_phoff, SEEK_SET) != 0)
return gpg_error_from_syserror ();
- // iterate over the program headers, compare their virtual addresses with the
- // address we are looking for, and if the program header matches, calculate
- // the offset of the given paddr in the file using the program header's
- // p_offset field.
+ /* Iterate over the program headers, compare their virtual addresses
+ with the address we are looking for, and if the program header
+ matches, calculate the offset of the given ADDR in the file using
+ the program header's p_offset field. */
for (e_phidx = 0; e_phidx < ehdr.e_phnum; e_phidx++)
{
- if (1 != fread (&phdr, sizeof (phdr), 1, fp))
+ if (fread (&phdr, sizeof (phdr), 1, fp) != 1)
return gpg_error_from_syserror ();
- if (phdr.p_type == PT_LOAD && phdr.p_vaddr <= paddr
- && phdr.p_vaddr + phdr.p_memsz > paddr)
+ if (phdr.p_type == PT_LOAD
+ && phdr.p_vaddr <= addr && addr < phdr.p_vaddr + phdr.p_memsz)
{
- // found section, compute the offset of paddr in the file
- *offset = phdr.p_offset + (paddr - phdr.p_vaddr);
+ /* Found segment, compute the offset of ADDR in the file */
+ *offset = phdr.p_offset + (addr - phdr.p_vaddr);
- if (0 != fseek (fp, 0, SEEK_SET))
+ if (fseek (fp, 0, SEEK_SET) != 0)
return gpg_error_from_syserror ();
return 0;
}
}
- // section not found in the file
+ /* Segment not found in the file */
return gpg_error (GPG_ERR_INV_OBJ);
}
@@ -655,17 +656,16 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
gcry_md_hd_t hd;
size_t buffer_size, nread;
char *buffer;
- unsigned long paddr;
+ unsigned long addr;
unsigned long offset = 0;
- unsigned long off = 0;
-
- paddr = (unsigned long)hmac_for_the_implementation - lm->l_addr;
+ unsigned long pos = 0;
+ addr = (unsigned long)hmac_for_the_implementation - lm->l_addr;
fp = fopen (filename, "rb");
if (!fp)
return gpg_error (GPG_ERR_INV_OBJ);
- err = get_file_offset (fp, paddr, &offset);
+ err = get_file_offset (fp, addr, &offset);
if (err)
{
fclose (fp);
@@ -698,7 +698,7 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
}
nread = fread (buffer, 1, HMAC_LEN, fp);
- off += nread;
+ pos += nread;
if (nread < HMAC_LEN)
{
xfree (buffer);
@@ -712,17 +712,17 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
nread = fread (buffer+HMAC_LEN, 1, buffer_size, fp);
if (nread < buffer_size)
{
- if (off - HMAC_LEN <= offset && offset <= off + nread)
- memset (buffer + HMAC_LEN + offset - off, 0, HMAC_LEN);
+ if (pos - HMAC_LEN <= offset && offset <= pos + nread)
+ memset (buffer + HMAC_LEN + offset - pos, 0, HMAC_LEN);
_gcry_md_write (hd, buffer, nread+HMAC_LEN);
break;
}
- if (off - HMAC_LEN <= offset && offset <= off + nread)
- memset (buffer + HMAC_LEN + offset - off, 0, HMAC_LEN);
+ if (pos - HMAC_LEN <= offset && offset <= pos + nread)
+ memset (buffer + HMAC_LEN + offset - pos, 0, HMAC_LEN);
_gcry_md_write (hd, buffer, nread);
memcpy (buffer, buffer+buffer_size, HMAC_LEN);
- off += nread;
+ pos += nread;
}
if (ferror (fp))
--
2.39.1
From 9dcf9305962b90febdf2d7cc73b49feadbf6a01f Mon Sep 17 00:00:00 2001
From: NIIBE Yutaka <gniibe@fsij.org>
Date: Wed, 16 Feb 2022 14:06:02 +0900
Subject: [PATCH] fips: Integrity check improvement, with only loadable
segments.
* configure.ac (READELF): Check the tool.
* src/Makefile.am (libgcrypt.so.hmac): Use genhmac.sh with hmac256.
* src/fips.c (get_file_offsets): Rename from get_file_offset.
Determine the OFFSET2 at the end of loadable segments, too.
Add fixup of the ELF header to exclude section information.
(hmac256_check): Finish scanning at the end of loadble segments.
* src/genhmac.sh: New.
--
This change fixes the build with ld.gold.
GnuPG-bug-id: 5835
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
---
configure.ac | 1 +
src/Makefile.am | 4 +--
src/fips.c | 73 +++++++++++++++++++++++++++++--------------
src/genhmac.sh | 83 +++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 136 insertions(+), 25 deletions(-)
create mode 100755 src/genhmac.sh
diff --git a/configure.ac b/configure.ac
index f0f1637f..ea01f5a6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -579,6 +579,7 @@ else
AC_DEFINE(ENABLE_HMAC_BINARY_CHECK,1,
[Define to support an HMAC based integrity check])
AC_CHECK_TOOL(OBJCOPY, [objcopy])
+ AC_CHECK_TOOL(READELF, [readelf])
if test "$use_hmac_binary_check" != yes ; then
DEF_HMAC_BINARY_CHECK=-DKEY_FOR_BINARY_CHECK="'\"$use_hmac_binary_check\"'"
fi
diff --git a/src/Makefile.am b/src/Makefile.am
index 018d5761..72100671 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -24,7 +24,7 @@ pkgconfigdir = $(libdir)/pkgconfig
pkgconfig_DATA = libgcrypt.pc
EXTRA_DIST = libgcrypt-config.in libgcrypt.m4 libgcrypt.vers \
- gcrypt.h.in libgcrypt.def libgcrypt.pc.in
+ gcrypt.h.in libgcrypt.def libgcrypt.pc.in genhmac.sh
bin_SCRIPTS = libgcrypt-config
m4datadir = $(datadir)/aclocal
@@ -149,7 +149,7 @@ libgcrypt.la.done: libgcrypt.so.hmac
@touch libgcrypt.la.done
libgcrypt.so.hmac: hmac256 libgcrypt.la
- ./hmac256 --stdkey --binary < .libs/libgcrypt.so > $@
+ READELF=$(READELF) AWK=$(AWK) $(srcdir)/genhmac.sh > $@
else !USE_HMAC_BINARY_CHECK
libgcrypt.la.done: libgcrypt.la
@touch libgcrypt.la.done
diff --git a/src/fips.c b/src/fips.c
index f16bce8b..134d0eae 100644
--- a/src/fips.c
+++ b/src/fips.c
@@ -598,50 +598,68 @@ hmac_for_the_implementation[HMAC_LEN];
/*
* In the ELF file opened as FP, determine the offset of the given
- * virtual address ADDR and return it in OFFSET. Rewinds FP to the
+ * virtual address ADDR and return it in R_OFFSET1. Determine the
+ * offset of last loadable section in R_OFFSET2. Rewinds FP to the
* beginning on success.
*/
static gpg_error_t
-get_file_offset (FILE *fp, unsigned long addr, unsigned long *offset)
+get_file_offsets (FILE *fp, unsigned long addr, ElfW (Ehdr) *ehdr_p,
+ unsigned long *r_offset1, unsigned long *r_offset2)
{
- ElfW (Ehdr) ehdr;
ElfW (Phdr) phdr;
uint16_t e_phidx;
+ long pos = 0;
/* Read the ELF header */
if (fseek (fp, 0, SEEK_SET) != 0)
return gpg_error_from_syserror ();
- if (fread (&ehdr, sizeof (ehdr), 1, fp) != 1)
+ if (fread (ehdr_p, sizeof (*ehdr_p), 1, fp) != 1)
return gpg_error_from_syserror ();
+ /* Fix up the ELF header, clean all section information. */
+ ehdr_p->e_shoff = 0;
+ ehdr_p->e_shentsize = 0;
+ ehdr_p->e_shnum = 0;
+ ehdr_p->e_shstrndx = 0;
+
/* The program header entry size should match the size of the phdr struct */
- if (ehdr.e_phentsize != sizeof (phdr))
+ if (ehdr_p->e_phentsize != sizeof (phdr))
return gpg_error (GPG_ERR_INV_OBJ);
- if (ehdr.e_phoff == 0)
+ if (ehdr_p->e_phoff == 0)
return gpg_error (GPG_ERR_INV_OBJ);
/* Jump to the first program header */
- if (fseek (fp, ehdr.e_phoff, SEEK_SET) != 0)
+ if (fseek (fp, ehdr_p->e_phoff, SEEK_SET) != 0)
return gpg_error_from_syserror ();
/* Iterate over the program headers, compare their virtual addresses
with the address we are looking for, and if the program header
matches, calculate the offset of the given ADDR in the file using
the program header's p_offset field. */
- for (e_phidx = 0; e_phidx < ehdr.e_phnum; e_phidx++)
+ for (e_phidx = 0; e_phidx < ehdr_p->e_phnum; e_phidx++)
{
if (fread (&phdr, sizeof (phdr), 1, fp) != 1)
return gpg_error_from_syserror ();
- if (phdr.p_type == PT_LOAD
- && phdr.p_vaddr <= addr && addr < phdr.p_vaddr + phdr.p_memsz)
- {
- /* Found segment, compute the offset of ADDR in the file */
- *offset = phdr.p_offset + (addr - phdr.p_vaddr);
- if (fseek (fp, 0, SEEK_SET) != 0)
- return gpg_error_from_syserror ();
- return 0;
- }
+ if (phdr.p_type == PT_PHDR)
+ continue;
+
+ if (phdr.p_type != PT_LOAD)
+ break;
+
+ pos = phdr.p_offset + phdr.p_filesz;
+ if (phdr.p_vaddr <= addr && addr < phdr.p_vaddr + phdr.p_memsz)
+ /* Found segment, compute the offset of ADDR in the file */
+ *r_offset1 = phdr.p_offset + (addr - phdr.p_vaddr);
+ }
+
+ if (*r_offset1)
+ {
+ if (fseek (fp, 0, SEEK_SET) != 0)
+ return gpg_error_from_syserror ();
+
+ *r_offset2 = (unsigned long)pos;
+ return 0;
}
/* Segment not found in the file */
@@ -657,15 +675,17 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
size_t buffer_size, nread;
char *buffer;
unsigned long addr;
- unsigned long offset = 0;
+ unsigned long offset1 = 0;
+ unsigned long offset2 = 0;
unsigned long pos = 0;
+ ElfW (Ehdr) ehdr;
addr = (unsigned long)hmac_for_the_implementation - lm->l_addr;
fp = fopen (filename, "rb");
if (!fp)
return gpg_error (GPG_ERR_INV_OBJ);
- err = get_file_offset (fp, addr, &offset);
+ err = get_file_offsets (fp, addr, &ehdr, &offset1, &offset2);
if (err)
{
fclose (fp);
@@ -710,16 +730,23 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
while (1)
{
nread = fread (buffer+HMAC_LEN, 1, buffer_size, fp);
+ if (pos + nread >= offset2)
+ nread = offset2 - pos;
+
+ /* Copy, fixed ELF header at the beginning. */
+ if (pos - HMAC_LEN == 0)
+ memcpy (buffer, &ehdr, sizeof (ehdr));
+
if (nread < buffer_size)
{
- if (pos - HMAC_LEN <= offset && offset <= pos + nread)
- memset (buffer + HMAC_LEN + offset - pos, 0, HMAC_LEN);
+ if (pos - HMAC_LEN <= offset1 && offset1 <= pos + nread)
+ memset (buffer + HMAC_LEN + offset1 - pos, 0, HMAC_LEN);
_gcry_md_write (hd, buffer, nread+HMAC_LEN);
break;
}
- if (pos - HMAC_LEN <= offset && offset <= pos + nread)
- memset (buffer + HMAC_LEN + offset - pos, 0, HMAC_LEN);
+ if (pos - HMAC_LEN <= offset1 && offset1 <= pos + nread)
+ memset (buffer + HMAC_LEN + offset1 - pos, 0, HMAC_LEN);
_gcry_md_write (hd, buffer, nread);
memcpy (buffer, buffer+buffer_size, HMAC_LEN);
pos += nread;
diff --git a/src/genhmac.sh b/src/genhmac.sh
new file mode 100755
index 00000000..bb33b9c6
--- /dev/null
+++ b/src/genhmac.sh
@@ -0,0 +1,83 @@
+#! /bin/sh
+
+#
+# genhmac.sh - Build tool to generate hmac hash
+#
+# Copyright (C) 2022 g10 Code GmbH
+#
+# This file is part of libgcrypt.
+#
+# libgcrypt is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public License
+# as published by the Free Software Foundation; either version 2.1 of
+# the License, or (at your option) any later version.
+#
+# libgcrypt 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, see <https://www.gnu.org/licenses/>.
+#
+
+set -e
+
+#
+# Following variables should be defined to invoke this script
+#
+# READELF
+# AWK
+#
+
+AWK_VERSION_OUTPUT=$($AWK 'BEGIN { print PROCINFO["version"] }')
+if test -n "$AWK_VERSION_OUTPUT"; then
+ # It's GNU awk, which supports PROCINFO.
+ AWK_OPTION=--non-decimal-data
+fi
+
+FILE=.libs/libgcrypt.so
+
+#
+# Fixup the ELF header to clean up section information
+#
+printf '%b' '\002' > 2.bin
+dd ibs=1 skip=4 count=1 if=$FILE status=none > class-byte.bin
+if cmp class-byte.bin 2.bin; then
+ CLASS=64
+ HEADER_SIZE=64
+else
+ CLASS=32
+ HEADER_SIZE=52
+fi
+
+if test $CLASS -eq 64; then
+ dd ibs=1 count=40 if=$FILE status=none
+ dd ibs=1 count=8 if=/dev/zero status=none
+ dd ibs=1 skip=48 count=10 if=$FILE status=none
+ dd ibs=1 count=6 if=/dev/zero status=none
+else
+ dd ibs=1 count=32 if=$FILE status=none
+ dd ibs=1 count=4 if=/dev/zero status=none
+ dd ibs=1 skip=36 count=10 if=$FILE status=none
+ dd ibs=1 count=6 if=/dev/zero status=none
+fi > header-fixed.bin
+
+# Compute the end of loadable segment.
+#
+# This require computation in hexadecimal, and GNU awk needs
+# --non-decimal-data option
+#
+OFFSET=$($READELF --wide --program-headers $FILE | \
+ $AWK $AWK_OPTION "/^ LOAD/ { offset=\$2+\$5-$HEADER_SIZE }\
+END { print offset}")
+
+#
+# Feed the header fixed and loadable segments to HMAC256
+# to generate hmac hash of the FILE
+#
+(cat header-fixed.bin; \
+ dd ibs=1 skip=$HEADER_SIZE count=$OFFSET if=$FILE status=none) \
+ | ./hmac256 --stdkey --binary
+
+rm -f 2.bin class-byte.bin header-fixed.bin
--
2.39.1
From a340e980388243ceae6df57d101036f3f2a955be Mon Sep 17 00:00:00 2001
From: NIIBE Yutaka <gniibe@fsij.org>
Date: Wed, 16 Feb 2022 20:08:15 +0900
Subject: [PATCH] fips: More portable integrity check.
* src/Makefile.am (EXTRA_DIST): Change the name of the script.
(libgcrypt.la.done): Invoce OBJCOPY with --add-section.
(libgcrypt.so.hmac): Specify ECHO_N.
* src/fips.c (get_file_offset): Rename from get_file_offsets.
Find the note section and return the value in HMAC.
(hmac256_check): Simplify by HMAC from the note section, not loaded.
(check_binary_integrity): Use dladdr instead of dladdr1.
* src/gen-note-integrity.sh: Rename from genhmac.sh.
Generate ElfN_Nhdr, and then the hmac.
--
The idea of use of .note is by Daiki Ueno.
https://gitlab.com/dueno/integrity-notes
Further, instead of NOTE segment loaded onto memory, use noload
section in the file.
Thanks to Clemens Lang for initiating this direction of improvement.
The namespace "FDO" would need to be changed.
GnuPG-bug-id: 5835
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
---
src/Makefile.am | 8 +-
src/fips.c | 167 +++++++++++++---------
src/{genhmac.sh => gen-note-integrity.sh} | 34 ++++-
3 files changed, 134 insertions(+), 75 deletions(-)
rename src/{genhmac.sh => gen-note-integrity.sh} (78%)
diff --git a/src/Makefile.am b/src/Makefile.am
index 72100671..b8bb187a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -24,7 +24,7 @@ pkgconfigdir = $(libdir)/pkgconfig
pkgconfig_DATA = libgcrypt.pc
EXTRA_DIST = libgcrypt-config.in libgcrypt.m4 libgcrypt.vers \
- gcrypt.h.in libgcrypt.def libgcrypt.pc.in genhmac.sh
+ gcrypt.h.in libgcrypt.def libgcrypt.pc.in gen-note-integrity.sh
bin_SCRIPTS = libgcrypt-config
m4datadir = $(datadir)/aclocal
@@ -143,13 +143,15 @@ if USE_HMAC_BINARY_CHECK
CLEANFILES += libgcrypt.so.hmac
libgcrypt.la.done: libgcrypt.so.hmac
- $(OBJCOPY) --update-section .rodata1=libgcrypt.so.hmac \
+ $(OBJCOPY) --add-section .note.fdo.integrity=libgcrypt.so.hmac \
+ --set-section-flags .note.fdo.integrity=noload,readonly \
.libs/libgcrypt.so .libs/libgcrypt.so.new
mv -f .libs/libgcrypt.so.new .libs/libgcrypt.so.*.*
@touch libgcrypt.la.done
libgcrypt.so.hmac: hmac256 libgcrypt.la
- READELF=$(READELF) AWK=$(AWK) $(srcdir)/genhmac.sh > $@
+ ECHO_N=$(ECHO_N) READELF=$(READELF) AWK=$(AWK) \
+ $(srcdir)/gen-note-integrity.sh > $@
else !USE_HMAC_BINARY_CHECK
libgcrypt.la.done: libgcrypt.la
@touch libgcrypt.la.done
diff --git a/src/fips.c b/src/fips.c
index 134d0eae..d798d577 100644
--- a/src/fips.c
+++ b/src/fips.c
@@ -593,22 +593,20 @@ run_random_selftests (void)
# endif
#define HMAC_LEN 32
-static const unsigned char __attribute__ ((section (".rodata1")))
-hmac_for_the_implementation[HMAC_LEN];
-
/*
- * In the ELF file opened as FP, determine the offset of the given
- * virtual address ADDR and return it in R_OFFSET1. Determine the
- * offset of last loadable section in R_OFFSET2. Rewinds FP to the
- * beginning on success.
+ * In the ELF file opened as FP, fill the ELF header to the pointer
+ * EHDR_P, determine the offset of last loadable segment in R_OFFSET.
+ * Also, find the section which contains the hmac value and return it
+ * in HMAC. Rewinds FP to the beginning on success.
*/
static gpg_error_t
-get_file_offsets (FILE *fp, unsigned long addr, ElfW (Ehdr) *ehdr_p,
- unsigned long *r_offset1, unsigned long *r_offset2)
+get_file_offset (FILE *fp, ElfW (Ehdr) *ehdr_p,
+ unsigned long *r_offset, unsigned char hmac[HMAC_LEN])
{
ElfW (Phdr) phdr;
- uint16_t e_phidx;
- long pos = 0;
+ ElfW (Shdr) shdr;
+ int i;
+ unsigned long off_segment = 0;
/* Read the ELF header */
if (fseek (fp, 0, SEEK_SET) != 0)
@@ -616,12 +614,6 @@ get_file_offsets (FILE *fp, unsigned long addr, ElfW (Ehdr) *ehdr_p,
if (fread (ehdr_p, sizeof (*ehdr_p), 1, fp) != 1)
return gpg_error_from_syserror ();
- /* Fix up the ELF header, clean all section information. */
- ehdr_p->e_shoff = 0;
- ehdr_p->e_shentsize = 0;
- ehdr_p->e_shnum = 0;
- ehdr_p->e_shstrndx = 0;
-
/* The program header entry size should match the size of the phdr struct */
if (ehdr_p->e_phentsize != sizeof (phdr))
return gpg_error (GPG_ERR_INV_OBJ);
@@ -632,11 +624,9 @@ get_file_offsets (FILE *fp, unsigned long addr, ElfW (Ehdr) *ehdr_p,
if (fseek (fp, ehdr_p->e_phoff, SEEK_SET) != 0)
return gpg_error_from_syserror ();
- /* Iterate over the program headers, compare their virtual addresses
- with the address we are looking for, and if the program header
- matches, calculate the offset of the given ADDR in the file using
- the program header's p_offset field. */
- for (e_phidx = 0; e_phidx < ehdr_p->e_phnum; e_phidx++)
+ /* Iterate over the program headers, determine the last loadable
+ segment. */
+ for (i = 0; i < ehdr_p->e_phnum; i++)
{
if (fread (&phdr, sizeof (phdr), 1, fp) != 1)
return gpg_error_from_syserror ();
@@ -647,45 +637,100 @@ get_file_offsets (FILE *fp, unsigned long addr, ElfW (Ehdr) *ehdr_p,
if (phdr.p_type != PT_LOAD)
break;
- pos = phdr.p_offset + phdr.p_filesz;
- if (phdr.p_vaddr <= addr && addr < phdr.p_vaddr + phdr.p_memsz)
- /* Found segment, compute the offset of ADDR in the file */
- *r_offset1 = phdr.p_offset + (addr - phdr.p_vaddr);
+ off_segment = phdr.p_offset + phdr.p_filesz;
}
- if (*r_offset1)
+ if (!off_segment)
+ /* The segment not found in the file */
+ return gpg_error (GPG_ERR_INV_OBJ);
+
+ /* The section header entry size should match the size of the shdr struct */
+ if (ehdr_p->e_shentsize != sizeof (shdr))
+ return gpg_error (GPG_ERR_INV_OBJ);
+ if (ehdr_p->e_shoff == 0)
+ return gpg_error (GPG_ERR_INV_OBJ);
+
+ /* Jump to the first section header */
+ if (fseek (fp, ehdr_p->e_shoff, SEEK_SET) != 0)
+ return gpg_error_from_syserror ();
+
+ /* Iterate over the section headers, determine the note section,
+ read the hmac value. */
+ for (i = 0; i < ehdr_p->e_shnum; i++)
{
- if (fseek (fp, 0, SEEK_SET) != 0)
+ long off;
+
+ if (fread (&shdr, sizeof (shdr), 1, fp) != 1)
return gpg_error_from_syserror ();
- *r_offset2 = (unsigned long)pos;
- return 0;
+ off = ftell (fp);
+ if (shdr.sh_type == SHT_NOTE && shdr.sh_flags == 0 && shdr.sh_size == 48)
+ {
+ const char header_of_the_note[] = {
+ 0x04, 0x00, 0x00, 0x00,
+ 0x20, 0x00, 0x00, 0x00,
+ 0xca, 0xfe, 0x2a, 0x8e,
+ 'F', 'D', 'O', 0x00
+ };
+ unsigned char header[16];
+
+ /* Jump to the note section. */
+ if (fseek (fp, shdr.sh_offset, SEEK_SET) != 0)
+ return gpg_error_from_syserror ();
+
+ if (fread (header, sizeof (header), 1, fp) != 1)
+ return gpg_error_from_syserror ();
+
+ if (!memcmp (header, header_of_the_note, 16))
+ {
+ /* Found. Read the hmac value into HMAC. */
+ if (fread (hmac, HMAC_LEN, 1, fp) != 1)
+ return gpg_error_from_syserror ();
+ break;
+ }
+
+ /* Back to the next section header. */
+ if (fseek (fp, off, SEEK_SET) != 0)
+ return gpg_error_from_syserror ();
+ }
}
- /* Segment not found in the file */
- return gpg_error (GPG_ERR_INV_OBJ);
+ if (i == ehdr_p->e_shnum)
+ /* The note section not found. */
+ return gpg_error (GPG_ERR_INV_OBJ);
+
+ /* Fix up the ELF header, clean all section information. */
+ ehdr_p->e_shoff = 0;
+ ehdr_p->e_shentsize = 0;
+ ehdr_p->e_shnum = 0;
+ ehdr_p->e_shstrndx = 0;
+
+ *r_offset = off_segment;
+ if (fseek (fp, 0, SEEK_SET) != 0)
+ return gpg_error_from_syserror ();
+
+ return 0;
}
static gpg_error_t
-hmac256_check (const char *filename, const char *key, struct link_map *lm)
+hmac256_check (const char *filename, const char *key)
{
gpg_error_t err;
FILE *fp;
gcry_md_hd_t hd;
- size_t buffer_size, nread;
+ const size_t buffer_size = 32768;
+ size_t nread;
char *buffer;
- unsigned long addr;
- unsigned long offset1 = 0;
- unsigned long offset2 = 0;
+ unsigned long offset = 0;
unsigned long pos = 0;
ElfW (Ehdr) ehdr;
+ unsigned char hmac[HMAC_LEN];
- addr = (unsigned long)hmac_for_the_implementation - lm->l_addr;
fp = fopen (filename, "rb");
if (!fp)
return gpg_error (GPG_ERR_INV_OBJ);
- err = get_file_offsets (fp, addr, &ehdr, &offset1, &offset2);
+ err = get_file_offset (fp, &ehdr, &offset, hmac);
if (err)
{
fclose (fp);
@@ -707,8 +752,7 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
return err;
}
- buffer_size = 32768;
- buffer = xtrymalloc (buffer_size + HMAC_LEN);
+ buffer = xtrymalloc (buffer_size);
if (!buffer)
{
err = gpg_error_from_syserror ();
@@ -717,38 +761,21 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
return err;
}
- nread = fread (buffer, 1, HMAC_LEN, fp);
- pos += nread;
- if (nread < HMAC_LEN)
- {
- xfree (buffer);
- fclose (fp);
- _gcry_md_close (hd);
- return gpg_error (GPG_ERR_TOO_SHORT);
- }
-
while (1)
{
- nread = fread (buffer+HMAC_LEN, 1, buffer_size, fp);
- if (pos + nread >= offset2)
- nread = offset2 - pos;
+ nread = fread (buffer, 1, buffer_size, fp);
+ if (pos + nread >= offset)
+ nread = offset - pos;
- /* Copy, fixed ELF header at the beginning. */
- if (pos - HMAC_LEN == 0)
+ /* Copy the fixed ELF header at the beginning. */
+ if (pos == 0)
memcpy (buffer, &ehdr, sizeof (ehdr));
+ _gcry_md_write (hd, buffer, nread);
+
if (nread < buffer_size)
- {
- if (pos - HMAC_LEN <= offset1 && offset1 <= pos + nread)
- memset (buffer + HMAC_LEN + offset1 - pos, 0, HMAC_LEN);
- _gcry_md_write (hd, buffer, nread+HMAC_LEN);
- break;
- }
+ break;
- if (pos - HMAC_LEN <= offset1 && offset1 <= pos + nread)
- memset (buffer + HMAC_LEN + offset1 - pos, 0, HMAC_LEN);
- _gcry_md_write (hd, buffer, nread);
- memcpy (buffer, buffer+buffer_size, HMAC_LEN);
pos += nread;
}
@@ -759,7 +786,7 @@ hmac256_check (const char *filename, const char *key, struct link_map *lm)
unsigned char *digest;
digest = _gcry_md_read (hd, 0);
- if (!memcmp (digest, hmac_for_the_implementation, HMAC_LEN))
+ if (!memcmp (digest, hmac, HMAC_LEN))
/* Success. */
err = 0;
else
@@ -780,13 +807,11 @@ check_binary_integrity (void)
gpg_error_t err;
Dl_info info;
const char *key = KEY_FOR_BINARY_CHECK;
- void *extra_info;
- if (!dladdr1 (hmac_for_the_implementation, &info, &extra_info,
- RTLD_DL_LINKMAP))
+ if (!dladdr (hmac256_check, &info))
err = gpg_error_from_syserror ();
else
- err = hmac256_check (info.dli_fname, key, extra_info);
+ err = hmac256_check (info.dli_fname, key);
reporter ("binary", 0, NULL, err? gpg_strerror (err):NULL);
#ifdef HAVE_SYSLOG
diff --git a/src/genhmac.sh b/src/gen-note-integrity.sh
similarity index 78%
rename from src/genhmac.sh
rename to src/gen-note-integrity.sh
index bb33b9c6..969fdca6 100755
--- a/src/genhmac.sh
+++ b/src/gen-note-integrity.sh
@@ -1,7 +1,7 @@
#! /bin/sh
#
-# genhmac.sh - Build tool to generate hmac hash
+# gen-note-integrity.sh - Build tool to generate hmac hash section
#
# Copyright (C) 2022 g10 Code GmbH
#
@@ -28,8 +28,40 @@ set -e
#
# READELF
# AWK
+# ECHO_N
#
+######## Emit ElfN_Nhdr for note.fdo.integrity ########
+
+NOTE_NAME="FDO"
+
+# n_namesz = 4 including NUL
+printf '%b' '\004'
+printf '%b' '\000'
+printf '%b' '\000'
+printf '%b' '\000'
+
+# n_descsz = 32
+printf '%b' '\040'
+printf '%b' '\000'
+printf '%b' '\000'
+printf '%b' '\000'
+
+# n_type: NT_FDO_INTEGRITY=0xCAFE2A8E
+printf '%b' '\312'
+printf '%b' '\376'
+printf '%b' '\052'
+printf '%b' '\216'
+
+# the name
+echo $ECHO_N $NOTE_NAME
+printf '%b' '\000'
+
+# Here comes the alignment. As the size of name is 4, it's none.
+# NO PADDING HERE.
+
+######## Rest is to generate hmac hash ########
+
AWK_VERSION_OUTPUT=$($AWK 'BEGIN { print PROCINFO["version"] }')
if test -n "$AWK_VERSION_OUTPUT"; then
# It's GNU awk, which supports PROCINFO.
--
2.39.1