103 lines
3.6 KiB
Text
Executable file
103 lines
3.6 KiB
Text
Executable file
# test_zeroize.gdb
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#
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# Copyright The Mbed TLS Contributors
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# SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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#
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# This file is provided under the Apache License 2.0, or the
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# GNU General Public License v2.0 or later.
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#
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# **********
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# Apache License 2.0:
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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# **********
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#
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# **********
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# GNU General Public License v2.0 or later:
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License along
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# with this program; if not, write to the Free Software Foundation, Inc.,
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# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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#
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# **********
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#
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# Purpose
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#
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# Run a test using the debugger to check that the mbedtls_platform_zeroize()
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# function in platform_util.h is not being optimized out by the compiler. To do
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# so, the script loads the test program at programs/test/zeroize.c and sets a
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# breakpoint at the last return statement in main(). When the breakpoint is
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# hit, the debugger manually checks the contents to be zeroized and checks that
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# it is actually cleared.
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#
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# The mbedtls_platform_zeroize() test is debugger driven because there does not
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# seem to be a mechanism to reliably check whether the zeroize calls are being
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# eliminated by compiler optimizations from within the compiled program. The
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# problem is that a compiler would typically remove what it considers to be
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# "unnecessary" assignments as part of redundant code elimination. To identify
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# such code, the compilar will create some form dependency graph between
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# reads and writes to variables (among other situations). It will then use this
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# data structure to remove redundant code that does not have an impact on the
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# program's observable behavior. In the case of mbedtls_platform_zeroize(), an
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# intelligent compiler could determine that this function clears a block of
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# memory that is not accessed later in the program, so removing the call to
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# mbedtls_platform_zeroize() does not have an observable behavior. However,
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# inserting a test after a call to mbedtls_platform_zeroize() to check whether
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# the block of memory was correctly zeroed would force the compiler to not
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# eliminate the mbedtls_platform_zeroize() call. If this does not occur, then
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# the compiler potentially has a bug.
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#
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# Note: This test requires that the test program is compiled with -g3.
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set confirm off
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file ./programs/test/zeroize
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search GDB_BREAK_HERE
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break $_
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set args ./programs/test/zeroize.c
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run
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set $i = 0
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set $len = sizeof(buf)
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set $buf = buf
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while $i < $len
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if $buf[$i++] != 0
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echo The buffer at was not zeroized\n
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quit 1
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end
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end
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echo The buffer was correctly zeroized\n
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continue
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if $_exitcode != 0
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echo The program did not terminate correctly\n
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quit 1
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end
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quit 0
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