include: util: Add mem_xor functions

Add functions to do XOR on arrays of memory, with one that
takes arbitrary sizes and one for 32 bits and 128 bits as
those are common sizes for this functionality.

Signed-off-by: Emil Gydesen <[email protected]>

Author: Thalley

include/zephyr/sys/util.h

@@ -657,6 +657,45 @@ char *utf8_lcpy(char *dst, const char *src, size_t n);
 	(((buflen) != 0) &&                        \
 	((UINTPTR_MAX - (uintptr_t)(addr)) <= ((uintptr_t)((buflen) - 1))))
 
+/**
+ * @brief XOR n bytes
+ *
+ * @param dst  Destination of where to store result. Shall be @p len bytes.
+ * @param src1 First source. Shall be @p len bytes.
+ * @param src2 Second source. Shall be @p len bytes.
+ * @param len  Number of bytes to XOR.
+ */
+static inline void mem_xor_n(uint8_t *dst, const uint8_t *src1, const uint8_t *src2, size_t len)
+{
+	while (len--) {
+		*dst++ = *src1++ ^ *src2++;
+	}
+}
+
+/**
+ * @brief XOR 32 bits
+ *
+ * @param dst  Destination of where to store result. Shall be 32 bits.
+ * @param src1 First source. Shall be 32 bits.
+ * @param src2 Second source. Shall be 32 bits.
+ */
+static inline void mem_xor_32(uint8_t dst[4], const uint8_t src1[4], const uint8_t src2[4])
+{
+	mem_xor_n(dst, src1, src2, 4U);
+}
+
+/**
+ * @brief XOR 128 bits
+ *
+ * @param dst  Destination of where to store result. Shall be 128 bits.
+ * @param src1 First source. Shall be 128 bits.
+ * @param src2 Second source. Shall be 128 bits.
+ */
+static inline void mem_xor_128(uint8_t dst[16], const uint8_t src1[16], const uint8_t src2[16])
+{
+	mem_xor_n(dst, src1, src2, 16);
+}
+
 #ifdef __cplusplus
 }
 #endif

subsys/bluetooth/audio/csip_crypto.c

@@ -17,6 +17,7 @@
 #include <tinycrypt/cmac_mode.h>
 #include <tinycrypt/ccm_mode.h>
 #include <zephyr/sys/byteorder.h>
+#include <zephyr/sys/util.h>
 
 #include "common/bt_str.h"
 
@@ -51,16 +52,6 @@ static int aes_cmac(const uint8_t key[BT_CSIP_CRYPTO_KEY_SIZE],
 	return 0;
 }
 
-static void xor_128(const uint8_t a[16], const uint8_t b[16], uint8_t out[16])
-{
-	size_t len = 16;
-	/* TODO: Identical to the xor_128 from smp.c: Move to util */
-
-	while (len--) {
-		*out++ = *a++ ^ *b++;
-	}
-}
-
 int bt_csip_sih(const uint8_t sirk[BT_CSIP_SET_SIRK_SIZE], uint8_t r[BT_CSIP_CRYPTO_PRAND_SIZE],
 		uint8_t out[BT_CSIP_CRYPTO_HASH_SIZE])
 {
@@ -229,7 +220,7 @@ int bt_csip_sef(const uint8_t k[BT_CSIP_CRYPTO_KEY_SIZE],
 		sys_mem_swap(k1_out, sizeof(k1_out));
 	}
 
-	xor_128(k1_out, sirk, out_sirk);
+	mem_xor_128(out_sirk, k1_out, sirk);
 	LOG_DBG("out %s", bt_hex(out_sirk, BT_CSIP_SET_SIRK_SIZE));
 
 	return 0;

subsys/bluetooth/controller/ll_sw/nordic/lll/lll_adv_iso.c

@@ -9,6 +9,7 @@
 
 #include <soc.h>
 #include <zephyr/sys/byteorder.h>
+#include <zephyr/sys/util.h>
 
 #include "hal/cpu.h"
 #include "hal/ccm.h"

subsys/bluetooth/controller/ll_sw/nordic/lll/lll_sync_iso.c

@@ -9,6 +9,7 @@
 
 #include <soc.h>
 #include <zephyr/sys/byteorder.h>
+#include <zephyr/sys/util.h>
 
 #include "hal/cpu.h"
 #include "hal/ccm.h"

subsys/bluetooth/controller/ll_sw/ull_conn_iso.c

@@ -6,6 +6,7 @@
 
 #include <zephyr/kernel.h>
 #include <zephyr/sys/byteorder.h>
+#include <zephyr/sys/util.h>
 #include <zephyr/bluetooth/hci_types.h>
 
 #include "util/util.h"

subsys/bluetooth/controller/util/mem.c

@@ -134,24 +134,6 @@ uint8_t mem_nz(uint8_t *src, uint16_t len)
 	return 0;
 }
 
-/**
- * @brief XOR bytes
- */
-inline void mem_xor_n(uint8_t *dst, uint8_t *src1, uint8_t *src2, uint16_t len)
-{
-	while (len--) {
-		*dst++ = *src1++ ^ *src2++;
-	}
-}
-
-/**
- * @brief XOR 32-bits
- */
-void mem_xor_32(uint8_t *dst, uint8_t *src1, uint8_t *src2)
-{
-	mem_xor_n(dst, src1, src2, 4U);
-}
-
 /**
  * @brief Unit test
  */

subsys/bluetooth/controller/util/mem.h

@@ -63,7 +63,5 @@ uint16_t mem_index_get(const void *mem, const void *mem_pool, uint16_t mem_size)
 
 void mem_rcopy(uint8_t *dst, uint8_t const *src, uint16_t len);
 uint8_t mem_nz(uint8_t *src, uint16_t len);
-void mem_xor_n(uint8_t *dst, uint8_t *src1, uint8_t *src2, uint16_t len);
-void mem_xor_32(uint8_t *dst, uint8_t *src1, uint8_t *src2);
 
 uint32_t mem_ut(void);

subsys/bluetooth/host/smp.c

@@ -1829,15 +1829,6 @@ static uint8_t smp_send_pairing_random(struct bt_smp *smp)
 }
 
 #if !defined(CONFIG_BT_SMP_SC_PAIR_ONLY)
-static void xor_128(const uint8_t p[16], const uint8_t q[16], uint8_t r[16])
-{
-	size_t len = 16;
-
-	while (len--) {
-		*r++ = *p++ ^ *q++;
-	}
-}
-
 static int smp_c1(const uint8_t k[16], const uint8_t r[16],
 		  const uint8_t preq[7], const uint8_t pres[7],
 		  const bt_addr_le_t *ia, const bt_addr_le_t *ra,
@@ -1864,7 +1855,7 @@ static int smp_c1(const uint8_t k[16], const uint8_t r[16],
 	/* c1 = e(k, e(k, r XOR p1) XOR p2) */
 
 	/* Using enc_data as temporary output buffer */
-	xor_128(r, p1, enc_data);
+	mem_xor_128(enc_data, r, p1);
 
 	err = bt_encrypt_le(k, enc_data, enc_data);
 	if (err) {
@@ -1878,7 +1869,7 @@ static int smp_c1(const uint8_t k[16], const uint8_t r[16],
 
 	LOG_DBG("p2 %s", bt_hex(p2, 16));
 
-	xor_128(enc_data, p2, enc_data);
+	mem_xor_128(enc_data, p2, enc_data);
 
 	return bt_encrypt_le(k, enc_data, enc_data);
 }

tests/unit/util/main.c

@@ -646,4 +646,75 @@ ZTEST(util, test_IF_DISABLED)
 	#undef test_IF_DISABLED_FLAG_B
 }
 
+ZTEST(util, test_mem_xor_n)
+{
+	const size_t max_len = 128;
+	uint8_t expected_result[max_len];
+	uint8_t src1[max_len];
+	uint8_t src2[max_len];
+	uint8_t dst[max_len];
+
+	memset(expected_result, 0, sizeof(expected_result));
+	memset(src1, 0, sizeof(src1));
+	memset(src2, 0, sizeof(src2));
+	memset(dst, 0, sizeof(dst));
+
+	for (size_t i = 0U; i < max_len; i++) {
+		const size_t len = i;
+
+		for (size_t j = 0U; j < len; j++) {
+			src1[j] = 0x33;
+			src2[j] = 0x0F;
+			expected_result[j] = 0x3C;
+		}
+
+		mem_xor_n(dst, src1, src2, len);
+		zassert_mem_equal(expected_result, dst, len);
+	}
+}
+
+ZTEST(util, test_mem_xor_32)
+{
+	uint8_t expected_result[4];
+	uint8_t src1[4];
+	uint8_t src2[4];
+	uint8_t dst[4];
+
+	memset(expected_result, 0, sizeof(expected_result));
+	memset(src1, 0, sizeof(src1));
+	memset(src2, 0, sizeof(src2));
+	memset(dst, 0, sizeof(dst));
+
+	for (size_t i = 0U; i < 4; i++) {
+		src1[i] = 0x43;
+		src2[i] = 0x0F;
+		expected_result[i] = 0x4C;
+	}
+
+	mem_xor_32(dst, src1, src2);
+	zassert_mem_equal(expected_result, dst, 4);
+}
+
+ZTEST(util, test_mem_xor_128)
+{
+	uint8_t expected_result[16];
+	uint8_t src1[16];
+	uint8_t src2[16];
+	uint8_t dst[16];
+
+	memset(expected_result, 0, sizeof(expected_result));
+	memset(src1, 0, sizeof(src1));
+	memset(src2, 0, sizeof(src2));
+	memset(dst, 0, sizeof(dst));
+
+	for (size_t i = 0U; i < 16; i++) {
+		src1[i] = 0x53;
+		src2[i] = 0x0F;
+		expected_result[i] = 0x5C;
+	}
+
+	mem_xor_128(dst, src1, src2);
+	zassert_mem_equal(expected_result, dst, 16);
+}
+
 ZTEST_SUITE(util, NULL, NULL, NULL, NULL, NULL);