From 5a13d00b6579326b12793a4b957c069358ddc590 Mon Sep 17 00:00:00 2001
From: PeterKietzmann <peter.kietzmann@haw-hamburg.de>
Date: Thu, 9 Jul 2020 11:46:12 +0200
Subject: [PATCH] sys/random: make sha1prng sha256 compatible

---
 Makefile.dep                          |  3 +-
 sys/random/{sha1prng.c => shaxprng.c} | 80 +++++++++++++++++++++------
 tests/rng/test.c                      |  2 +
 3 files changed, 66 insertions(+), 19 deletions(-)
 rename sys/random/{sha1prng.c => shaxprng.c} (54%)

diff --git a/Makefile.dep b/Makefile.dep
index 783119f4d3..46bf040078 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -782,7 +782,8 @@ ifneq (,$(filter random,$(USEMODULE)))
     USEMODULE += tinymt32
   endif
 
-  ifneq (,$(filter prng_sha1prng,$(USEMODULE)))
+  ifneq (,$(filter prng_sha%prng,$(USEMODULE)))
+    USEMODULE += prng_shaxprng
     USEMODULE += hashes
   endif
 
diff --git a/sys/random/sha1prng.c b/sys/random/shaxprng.c
similarity index 54%
rename from sys/random/sha1prng.c
rename to sys/random/shaxprng.c
index 6e7156715f..cdfbd9652c 100644
--- a/sys/random/sha1prng.c
+++ b/sys/random/shaxprng.c
@@ -14,7 +14,9 @@
  * @{
  * @file
  *
- * @brief   SHA1PRNG random number generator implementation
+ * @brief   SHA based PRNG random number generator implementation
+ *
+ * BLABLA
  *
  * @author Peter Kietzmann <peter.kietzmann@haw-hamburg.de>
  * @}
@@ -24,10 +26,52 @@
 #include <string.h>
 
 #include "hashes/sha1.h"
+#include "hashes/sha256.h"
+#include "kernel_defines.h"
 
-#define STATE_SIZE           (SHA1_DIGEST_LENGTH)
+#if IS_USED(MODULE_PRNG_SHA1PRNG)
+/* state size is digset length of SHA-1 */
+#define STATE_SIZE                      (SHA1_DIGEST_LENGTH)
+typedef sha1_context shax_context_t;
+#elif IS_USED(MODULE_PRNG_SHA256PRNG)
+/* state size is digest length of SHA-256 */
+#define STATE_SIZE                      (SHA256_DIGEST_LENGTH)
+typedef sha256_context_t shax_context_t;
+#endif
+
+static inline void _shax_init(shax_context_t *ctx)
+{
+    if (IS_USED(MODULE_PRNG_SHA1PRNG)) {
+        sha1_init((sha1_context *)ctx);
+    }
+    else if (IS_USED(MODULE_PRNG_SHA256PRNG)) {
+        sha256_init((sha256_context_t *)ctx);
+    }
+}
+
+static inline void _shax_update(shax_context_t *ctx, const void *data, size_t len)
+{
+    if (IS_USED(MODULE_PRNG_SHA1PRNG)) {
+        sha1_update((sha1_context *)ctx, data, len);
+    }
+    else if (IS_USED(MODULE_PRNG_SHA256PRNG)) {
+        sha256_update((sha256_context_t *)ctx, data, len);
+    }
+}
+
+static inline void _shax_final(shax_context_t *ctx, void *digest)
+{
+    if (IS_USED(MODULE_PRNG_SHA1PRNG)) {
+        sha1_final((sha1_context *)ctx, digest);
+    }
+    else if (IS_USED(MODULE_PRNG_SHA256PRNG)) {
+        sha256_final((sha256_context_t *)ctx, digest);
+    }
+}
+
+/* allocate SHA context */
+static shax_context_t ctx;
 
-static sha1_context ctx;
 static uint32_t datapos = STATE_SIZE;
 static int8_t digestdata[STATE_SIZE];
 static int8_t prng_state[STATE_SIZE];
@@ -62,7 +106,7 @@ void _updatestate(int8_t *state)
     }
 }
 
-void _random_bytes(uint8_t *bytes, size_t size) /* TODO: use with global API */
+void _random_bytes(uint8_t *bytes, size_t size)
 {
     uint32_t loc = 0;
     while (loc < size)
@@ -88,14 +132,14 @@ void _random_bytes(uint8_t *bytes, size_t size) /* TODO: use with global API */
         /* no out data ready, (re)fill internal buffer */
         else
         {
-            /* reset SHA1 internal state */
-            sha1_init(&ctx);
+            /* reset SHA internal state */
+            _shax_init(&ctx);
 
-            /* update SHA1 internal state with PRNG state */
-            sha1_update(&ctx, (void *)prng_state, sizeof(prng_state));
+            /* update SHA internal state with PRNG state */
+            _shax_update(&ctx, prng_state, sizeof(prng_state));
 
             /* get the digest */
-            sha1_final(&ctx, digestdata);
+            _shax_final(&ctx, digestdata);
 
             /* update PRNG state for next round */
             _updatestate(prng_state);
@@ -108,9 +152,9 @@ void _random_bytes(uint8_t *bytes, size_t size) /* TODO: use with global API */
 
 void random_init_by_array(uint32_t init_key[], int key_length)
 {
-    sha1_init(&ctx);
-    sha1_update(&ctx, (void *)init_key, key_length);
-    sha1_final(&ctx, digestdata);
+    _shax_init(&ctx);
+    _shax_update(&ctx, init_key, key_length);
+    _shax_final(&ctx, digestdata);
 
     /* copy seeded SHA1 state to PRNG state */
     memcpy(prng_state, &ctx.state, STATE_SIZE);
@@ -124,13 +168,13 @@ void random_init(uint32_t seed)
 uint32_t random_uint32(void)
 {
     uint32_t ret;
-    int8_t bytes[sizeof(uint32_t)];
-    _random_bytes((uint8_t *)bytes, sizeof(uint32_t));
+    uint8_t bytes[sizeof(uint32_t)];
+    _random_bytes(bytes, sizeof(bytes));
 
-    ret = ((bytes[0] & 0xff) << 24)
-        | ((bytes[1] & 0xff) << 16)
-        | ((bytes[2] & 0xff) <<  8)
-        |  (bytes[3] & 0xff);
+    ret = ((uint32_t)(bytes[0] & 0xff) << 24)
+        | ((uint32_t)(bytes[1] & 0xff) << 16)
+        | ((uint32_t)(bytes[2] & 0xff) <<  8)
+        | ((uint32_t)(bytes[3] & 0xff));
 
     return ret;
 }
diff --git a/tests/rng/test.c b/tests/rng/test.c
index 41bf6f229e..d796bfcec7 100644
--- a/tests/rng/test.c
+++ b/tests/rng/test.c
@@ -61,6 +61,8 @@ static void test_init(char *name)
         puts("Musl C PRNG.\n");
 #elif MODULE_PRNG_SHA1PRNG
         puts("SHA1 PRNG.\n");
+#elif MODULE_PRNG_SHA256PRNG
+        puts("SHA256 PRNG.\n");
 #elif MODULE_PRNG_TINYMT32
         puts("Tiny Mersenne Twister PRNG.\n");
 #elif MODULE_PRNG_XORSHIFT