Tests: verify that CRYPTOPP_ALIGN_DATA delivers the requested alignment

src/Common/Tests.c

@@ -20,6 +20,7 @@
 #include <string.h>
 #include "Pkcs5.h"
 #include "cpu.h"
+#include "Volumes.h"
 
 typedef struct {
 	CRYPTOPP_ALIGN_DATA(16) unsigned __int8 key1[32];
@@ -1280,6 +1281,28 @@ BOOL TestSectorBufEncryption (PCRYPTO_INFO ci)
 	return (nTestsPerformed == 150);
 }
 
+#ifndef TC_WINDOWS_DRIVER
+// Must stay smaller than the alignment under test: the ABI aligns larger objects by itself.
+#define TC_ALIGNMENT_PROBE_SIZE	4
+
+/* Verifies that CRYPTOPP_ALIGN_DATA actually delivers the alignment it requests. It expands
+   to nothing for compilers that are neither MSVC nor GCC/Clang (see Crypto/config.h), and the
+   SIMD backends issue aligned loads against buffers declared with it. */
+static BOOL TestBufferAlignment (void)
+{
+	static CRYPTOPP_ALIGN_DATA(TC_DERIVED_KEY_BUFFER_ALIGNMENT) unsigned char derivedKeyProbe[TC_ALIGNMENT_PROBE_SIZE];
+	static CRYPTOPP_ALIGN_DATA(TC_KEY_INFO_BUFFER_ALIGNMENT) unsigned char keyInfoProbe[TC_ALIGNMENT_PROBE_SIZE];
+
+	if (!TC_IS_ALIGNED (derivedKeyProbe, TC_DERIVED_KEY_BUFFER_ALIGNMENT))
+		return FALSE;
+
+	if (!TC_IS_ALIGNED (keyInfoProbe, TC_KEY_INFO_BUFFER_ALIGNMENT))
+		return FALSE;
+
+	return TRUE;
+}
+#endif
+
 static BOOL DoAutoTestAlgorithms (void)
 {
 	PCRYPTO_INFO ci;
@@ -1489,6 +1512,13 @@ static BOOL DoAutoTestAlgorithms (void)
 		bFailed = TRUE;
 
 	crypto_close (ci);
+
+#ifndef TC_WINDOWS_DRIVER
+	/* Not run in the driver: a failing self-test there reaches TC_BUG_CHECK and would bugcheck the machine. */
+	if (!TestBufferAlignment ())
+		bFailed = TRUE;
+#endif
+
 	return !bFailed;
 }
 

src/Common/Volumes.h

@@ -41,6 +41,9 @@ extern "C" {
 // Required 16-byte alignment for KEY_INFO buffer to ensure optimal performance and compatibility with SIMD instructions.
 #define TC_KEY_INFO_BUFFER_ALIGNMENT			16
 
+// TRUE if the address meets the given alignment.
+#define TC_IS_ALIGNED(address, alignment)		((((uint64) (address)) % (alignment)) == 0)
+
 // Current volume format version (created by TrueCrypt 6.0+)
 #define TC_VOLUME_FORMAT_VERSION				2
 

src/Volume/EncryptionTest.cpp

@@ -70,10 +70,30 @@ namespace VeraCrypt
 
 	void EncryptionTest::TestAll ()
 	{
+		TestAlignment();
 		TestAll (false);
 		TestAll (true);
 	}
 
+	// Must stay smaller than the alignment under test: the ABI aligns larger objects by itself.
+	#define TC_ALIGNMENT_PROBE_SIZE 4
+
+	// Verifies that CRYPTOPP_ALIGN_DATA actually delivers the alignment it requests.
+	// It expands to nothing for compilers that are neither MSVC nor GCC/Clang (see
+	// Crypto/config.h), and the SIMD backends issue aligned loads against buffers
+	// declared with it, so a silent expansion to nothing would fault at run time.
+	void EncryptionTest::TestAlignment ()
+	{
+		static CRYPTOPP_ALIGN_DATA(TC_DERIVED_KEY_BUFFER_ALIGNMENT) uint8 derivedKeyProbe[TC_ALIGNMENT_PROBE_SIZE];
+		static CRYPTOPP_ALIGN_DATA(TC_KEY_INFO_BUFFER_ALIGNMENT) uint8 keyInfoProbe[TC_ALIGNMENT_PROBE_SIZE];
+
+		if (!TC_IS_ALIGNED (derivedKeyProbe, TC_DERIVED_KEY_BUFFER_ALIGNMENT))
+			throw TestFailed (SRC_POS);
+
+		if (!TC_IS_ALIGNED (keyInfoProbe, TC_KEY_INFO_BUFFER_ALIGNMENT))
+			throw TestFailed (SRC_POS);
+	}
+
 	void EncryptionTest::TestAll (bool enableCpuEncryptionSupport)
 	{
 		bool hwSupportEnabled = Cipher::IsHwSupportEnabled();

src/Volume/EncryptionTest.h

@@ -25,6 +25,7 @@ namespace VeraCrypt
 		static void TestAll (bool enableCpuEncryptionSupport);
 
 	protected:
+		static void TestAlignment ();
 		static void TestCiphers ();
 		static void TestLegacyModes ();
 		static void TestPkcs5 ();