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Merge pull request #10581 from valeriosetti/issue665-backport

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[backport] Software GCM table calculation buggy with gcc -O3
This commit is contained in:
Valerio Setti
2026-01-29 15:17:00 +00:00
committed by GitHub
parent 337218d667 2b2f430fcd
commit 25b5fcdcd3
3 changed files with 55 additions and 4 deletions
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6
ChangeLog.d/issue665.txt Normal file
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@@ -0,0 +1,6 @@
Bugfix
* Fix a bug that caused GCM tag calculations to fail, so that data was
correctly encrypted but could not be authenticated. The bug was only
observed with GCC 10.0 to 14.2 inclusive, when compiling with -O3, and
running without AESNI or AESCE.
Fixes #665.

11
library/alignment.h
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@@ -15,6 +15,7 @@
#include <string.h>
#include <stdlib.h>
#if !defined(MBEDTLS_ALIGNMENT_DISABLE_EFFICENT_UNALIGNED_ACCESS) //no-check-names
/*
* Define MBEDTLS_EFFICIENT_UNALIGNED_ACCESS for architectures where unaligned memory
* accesses are known to be efficient.
@@ -35,7 +36,9 @@
* device memory).
*/
#define MBEDTLS_EFFICIENT_UNALIGNED_ACCESS
#endif
#endif /* __ARM_FEATURE_UNALIGNED || MBEDTLS_ARCH_IS_X86 || MBEDTLS_ARCH_IS_X64 ||
* MBEDTLS_PLATFORM_IS_WINDOWS_ON_ARM64 */
#endif /* MBEDTLS_ALIGNMENT_DISABLE_EFFICENT_UNALIGNED_ACCESS */ //no-check-names
#if defined(__IAR_SYSTEMS_ICC__) && \
(defined(MBEDTLS_ARCH_IS_ARM64) || defined(MBEDTLS_ARCH_IS_ARM32) \
@@ -85,13 +88,13 @@ typedef uint64_t __packed mbedtls_uint64_unaligned_t;
#define UINT_UNALIGNED_STRUCT
typedef struct {
uint16_t x;
} __attribute__((packed)) mbedtls_uint16_unaligned_t;
} __attribute__((packed, may_alias)) mbedtls_uint16_unaligned_t;
typedef struct {
uint32_t x;
} __attribute__((packed)) mbedtls_uint32_unaligned_t;
} __attribute__((packed, may_alias)) mbedtls_uint32_unaligned_t;
typedef struct {
uint64_t x;
} __attribute__((packed)) mbedtls_uint64_unaligned_t;
} __attribute__((packed, may_alias)) mbedtls_uint64_unaligned_t;
#endif
/*

42
tests/scripts/components-compiler.sh
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@@ -172,3 +172,45 @@ component_test_zeroize () {
done
done
}
# This originated from an issue (https://github.com/Mbed-TLS/TF-PSA-Crypto/issues/665) found
# in GCM when the library is built with GCC "10.0 <= version <= 14.2" on platforms other than
# x86 and ARM64.
component_test_tf_psa_crypto_optimized_alignment() {
msg "build: verify alignment with O3 optimizations in GCC"
# Disable optimizations for x86 (and ARM64) so that alignment related problems in
# "alignment.h" can be tested also on standard PC.
scripts/config.py unset MBEDTLS_AESNI_C
scripts/config.py unset MBEDTLS_AESCE_C
# "-O3" is the optimization level that causes issues: the compiler tries to
# optimize operations order and if memory dependencies are not respected
# (as it happens in issue tf-psa-crypto#665) this completely messes up results.
EXTRA_C_FLAGS="-O3"
# Forcedly ignore "MBEDTLS_EFFICIENT_UNALIGNED_ACCESS" on x86 so that we
# can test the problematic case, i.e. the case where uint64 integers are
# accessed through "mbedtls_uint64_unaligned_t" structs.
EXTRA_C_FLAGS="$EXTRA_C_FLAGS -DMBEDTLS_ALIGNMENT_DISABLE_EFFICENT_UNALIGNED_ACCESS"
# Adding '-g3' flag doesn't affect testing, BUT it allows to dump the generated
# assembly code for "gcm.o" module for inspection. To do this use the
# following command:
# > objdump -S --disassemble out_of_source_build/drivers/builtin/CMakeFiles/builtin.dir/src/gcm.c.o > gcm.s
# A file named "gcm.s" will be generated containing a mix of C and corresponding
# assembly code.
EXTRA_C_FLAGS="$EXTRA_C_FLAGS -g3"
make CC=gcc CFLAGS="$EXTRA_C_FLAGS"
msg "test: verify alignment with O3 optimizations in GCC"
make test
}
support_test_tf_psa_crypto_optimized_alignment() {
case $(gcc -dumpfullversion 2>/dev/null) in
""|?.*) false;; # too old
10.*|11.*|12.*|13.*) true;;
14.[012].*) true;;
*) false;; # too recent
esac
}