add fake hash function to only copy inputs (#5)

* add fake hash function to only copy inputs

* fix tests

* fix code formatting

Makefile

@@ -159,7 +159,7 @@ endif
 
 # Hash module
 
-HASH_SRC = $(wildcard src/hash/sha*.c) src/hash/hash_algs.c
+HASH_SRC = $(wildcard src/hash/sha*.c) src/hash/copy.c src/hash/hash_algs.c
 HASH_OBJECTS = $(patsubst %.c, %.o, $(HASH_SRC))
 HASH_DEPS = $(patsubst %.c, %.d, $(HASH_SRC))
 

src/hash/copy.c

@@ -0,0 +1,61 @@
+#include "../lib_ecc_config.h"
+
+#include "copy.h"
+
+/* Init hash function */
+void copy256_init(copy256_context *ctx)
+{
+	MUST_HAVE(ctx != NULL);
+
+	ctx->copied_bytes = 0;
+}
+
+/* Update hash function */
+void copy256_update(copy256_context *ctx, const u8 *input, u32 ilen)
+{
+	u32 bytes_to_copy = ilen;
+	u16 left_bytes;
+
+	MUST_HAVE((ctx != NULL) && (input != NULL));
+
+	/* Nothing to process, return */
+	if (ilen == 0) {
+		return;
+	}
+
+	/* Get what's left in our local buffer */
+	left_bytes = COPY256_SIZE - (ctx->copied_bytes & 0x3F);
+
+	if (bytes_to_copy >= left_bytes) {
+		bytes_to_copy = left_bytes;
+	}
+	local_memcpy(ctx->buffer + ctx->copied_bytes, input, bytes_to_copy);
+	ctx->copied_bytes += bytes_to_copy;
+	return;
+}
+
+/* Finalize */
+void copy256_final(copy256_context *ctx, u8 output[COPY256_SIZE])
+{
+	MUST_HAVE((ctx != NULL) && (output != NULL));
+	// The ec_self_tests here may send less than COPY256_SIZE bytes
+	// We always send COPY256_SIZE to outputs, even if library users
+	// didn't send COPY256_SIZE to us.
+	local_memcpy(output, ctx->buffer, COPY256_SIZE);
+}
+
+void copy256_scattered(const u8 **inputs, const u32 *ilens,
+		      u8 output[COPY256_SIZE])
+{
+	copy256_context ctx;
+	int pos = 0;
+
+	copy256_init(&ctx);
+
+	while (inputs[pos] != NULL) {
+		copy256_update(&ctx, inputs[pos], ilens[pos]);
+		pos += 1;
+	}
+
+	copy256_final(&ctx, output);
+}

src/hash/copy.h

@@ -0,0 +1,23 @@
+#ifndef __COPY_H__
+#define __COPY_H__
+
+#include "../lib_ecc_config.h"
+#include "../words/words.h"
+#include "../utils/utils.h"
+
+#define COPY256_SIZE  32
+
+typedef struct {
+	u64 copied_bytes;
+	/* Internal buffer to handle updates in a block */
+	u8 buffer[COPY256_SIZE];
+} copy256_context;
+
+void copy256_init(copy256_context *ctx);
+void copy256_update(copy256_context *ctx, const u8 *input, u32 ilen);
+void copy256_final(copy256_context *ctx, u8 output[COPY256_SIZE]);
+void copy256_scattered(const u8 **inputs, const u32 *ilens,
+		      u8 output[COPY256_SIZE]);
+void copy256(const u8 *input, u32 ilen, u8 output[COPY256_SIZE]);
+
+#endif /* __COPY_H__ */

src/hash/hash_algs.h

@@ -19,6 +19,7 @@
 #include "../lib_ecc_config.h"
 #include "../lib_ecc_types.h"
 #include "../words/words.h"
+#include "copy.h"
 #include "sha224.h"
 #include "sha256.h"
 #include "sha384.h"
@@ -245,6 +246,14 @@ static const hash_mapping hash_maps[] = {
 #define MAX_HASH_ALG_NAME_LEN 9
 #endif /* MAX_HASH_ALG_NAME_LEN */
 #endif /* WITH_HASH_SHA3_512 */
+	{.type = COPY256,
+	 .name = "COPY256",
+	 .digest_size = COPY256_SIZE,
+	 .block_size = COPY256_SIZE,
+	 .hfunc_init = (_hfunc_init) copy256_init,
+	 .hfunc_update = (_hfunc_update) copy256_update,
+	 .hfunc_finalize = (_hfunc_finalize) copy256_final,
+	 .hfunc_scattered = copy256_scattered},
 	{.type = UNKNOWN_HASH_ALG,	/* Needs to be kept last */
 	 .name = "UNKNOWN",
 	 .digest_size = 0,

src/lib_ecc_types.h

@@ -77,6 +77,7 @@ typedef enum {
 #ifdef WITH_HASH_SHA3_512
 	SHA3_512 = 10,
 #endif
+	COPY256 = 11,
 } hash_alg_type;
 
 /* All curves we support */