crypto: sha256 - Use get/put_unaligned_be32 to get input, memzero_explicit

Use get/put_unaligned_be32 in lib/crypto/sha256.c to load / store data
so that it can be used with unaligned buffers too, making it more generic.

And use memzero_explicit for better clearing of sensitive data.

Note unlike other patches in this series this commit actually makes
functional changes to the sha256 code as used by the purgatory code.

This fully aligns the lib/crypto/sha256.c sha256 implementation with the
one from crypto/sha256_generic.c allowing us to remove the latter in
further patches in this series.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

lib/crypto/sha256.c

@@ -14,7 +14,7 @@
 #include <linux/bitops.h>
 #include <linux/string.h>
 #include <crypto/sha256.h>
-#include <asm/byteorder.h>
+#include <asm/unaligned.h>
 
 static inline u32 Ch(u32 x, u32 y, u32 z)
 {
@@ -33,7 +33,7 @@ static inline u32 Maj(u32 x, u32 y, u32 z)
 
 static inline void LOAD_OP(int I, u32 *W, const u8 *input)
 {
-	W[I] = __be32_to_cpu(((__be32 *)(input))[I]);
+	W[I] = get_unaligned_be32((__u32 *)input + I);
 }
 
 static inline void BLEND_OP(int I, u32 *W)
@@ -201,7 +201,7 @@ static void sha256_transform(u32 *state, const u8 *input)
 
 	/* clear any sensitive info... */
 	a = b = c = d = e = f = g = h = t1 = t2 = 0;
-	memset(W, 0, 64 * sizeof(u32));
+	memzero_explicit(W, 64 * sizeof(u32));
 }
 
 int sha256_init(struct sha256_state *sctx)
@@ -270,7 +270,7 @@ int sha256_final(struct sha256_state *sctx, u8 *out)
 
 	/* Store state in digest */
 	for (i = 0; i < 8; i++)
-		dst[i] = cpu_to_be32(sctx->state[i]);
+		put_unaligned_be32(sctx->state[i], &dst[i]);
 
 	/* Zeroize sensitive information. */
 	memset(sctx, 0, sizeof(*sctx));