Merge branch 'ln/cc20rng-revamp' into ln/devel

7 files changed, 167 insertions, 165 deletions

diff --git a/src/cc20rng/.clang-format b/src/cc20rng/.clang-format
new file mode 100644
index 0000000..8367454
--- /dev/null
+++ b/src/cc20rng/.clang-format
@@ -0,0 +1,4 @@
+IndentWidth: 4
+BreakBeforeBraces: Custom
+BraceWrapping:
+  AfterFunction: true
diff --git a/src/cc20rng/Makefile b/src/cc20rng/Makefile
index c52bc52..bc5fce5 100644
--- a/src/cc20rng/Makefile
+++ b/src/cc20rng/Makefile
@@ -45,6 +45,10 @@ $(PROJ_NAME).elf: $(SRCS)
 	$(OBJDUMP) -St $(PROJ_NAME).elf >$(PROJ_NAME).lst
 	$(SIZE) $(PROJ_NAME).elf
 
+c-format:
+	clang-format-4.0 -i cc20_prng.[ch]
+	clang-format-4.0 -style="{IndentWidth: 2}" -i main.c
+
 clean:
 	rm -f *.o
 	rm -f $(PROJ_NAME).elf
diff --git a/src/cc20rng/cc20_prng.c b/src/cc20rng/cc20_prng.c
index 3d52fc6..36c06a4 100644
--- a/src/cc20rng/cc20_prng.c
+++ b/src/cc20rng/cc20_prng.c
@@ -41,15 +41,16 @@
 #define CHACHA20_CONSTANT3 0x6b206574
 
 #ifdef CHACHA20_PRNG_DEBUG
-void _dump(struct cc20_state *cc, char *str);
+static void _dump(struct cc20_state *cc, char *str);
 #endif
 
-inline uint32_t rotl32 (uint32_t x, uint32_t n)
+static inline uint32_t rotl32(uint32_t x, uint32_t n)
 {
     return (x << n) | (x >> (32 - n));
 }
 
-inline void _qr(struct cc20_state *cc, uint32_t a, uint32_t b, uint32_t c, uint32_t d)
+static inline void _qr(struct cc20_state *cc, uint32_t a, uint32_t b,
+                       uint32_t c, uint32_t d)
 {
     cc->i[a] += cc->i[b];
     cc->i[d] ^= cc->i[a];
@@ -68,43 +69,40 @@ inline void _qr(struct cc20_state *cc, uint32_t a, uint32_t b, uint32_t c, uint3
     cc->i[b] = rotl32(cc->i[b], 7);
 }
 
-void chacha20_prng_reseed(struct cc20_state *cc, uint32_t *entropy)
+static void chacha20_setup(struct cc20_state *state,
+                           const struct cc20_state *src)
 {
-    uint32_t i = 256 / 8 / 4;
-    while (i--) {
-	cc->i[i] = entropy[i];
-    }
+    state->s.constant[0] = CHACHA20_CONSTANT0;
+    state->s.constant[1] = CHACHA20_CONSTANT1;
+    state->s.constant[2] = CHACHA20_CONSTANT2;
+    state->s.constant[3] = CHACHA20_CONSTANT3;
+
+    for (int i = 4; i < CHACHA20_BLOCK_SIZE_WORDS; i++)
+        state->i[i] = src->i[i];
 }
 
-void chacha20_prng_block(struct cc20_state *cc, uint32_t block_counter, struct cc20_state *out)
+void chacha20_prng_block(struct cc20_state *cc, uint8_t *out)
 {
     uint32_t i;
+    struct cc20_state *ws = (struct cc20_state *)out;
 
-    out->i[0] = CHACHA20_CONSTANT0;
-    out->i[1] = CHACHA20_CONSTANT1;
-    out->i[2] = CHACHA20_CONSTANT2;
-    out->i[3] = CHACHA20_CONSTANT3;
-
-    cc->i[12] = block_counter;
-
-    for (i = 4; i < CHACHA20_NUM_WORDS; i++) {
-	out->i[i] = cc->i[i];
-    }
+    chacha20_setup(ws, cc);
 
     for (i = 10; i; i--) {
-	_qr(out, 0, 4, 8,12);
-	_qr(out, 1, 5, 9,13);
-	_qr(out, 2, 6,10,14);
-	_qr(out, 3, 7,11,15);
-	_qr(out, 0, 5,10,15);
-	_qr(out, 1, 6,11,12);
-	_qr(out, 2, 7, 8,13);
-	_qr(out, 3, 4, 9,14);
+        _qr(ws, 0, 4, 8, 12);
+        _qr(ws, 1, 5, 9, 13);
+        _qr(ws, 2, 6, 10, 14);
+        _qr(ws, 3, 7, 11, 15);
+        _qr(ws, 0, 5, 10, 15);
+        _qr(ws, 1, 6, 11, 12);
+        _qr(ws, 2, 7, 8, 13);
+        _qr(ws, 3, 4, 9, 14);
     }
 
-    for (i = 0; i < CHACHA20_NUM_WORDS; i++) {
-	out->i[i] += cc->i[i];
-    }
+    for (i = 0; i < CHACHA20_BLOCK_SIZE_WORDS; i++)
+        ws->i[i] += cc->i[i];
+
+    cc->s.counter--;
 }
 
 int chacha20_prng_self_test1()
@@ -113,17 +111,19 @@ int chacha20_prng_self_test1()
      *   https://tools.ietf.org/html/rfc7539#section-2.3.2
      */
     struct cc20_state test = {
-        {0x61707865, 0x3320646e, 0x79622d32, 0x6b206574,
-         0x03020100, 0x07060504, 0x0b0a0908, 0x0f0e0d0c,
-         0x13121110, 0x17161514, 0x1b1a1918, 0x1f1e1d1c,
-         0x00000001, 0x09000000, 0x4a000000, 0x00000000,
+        .i = {
+            0x61707865, 0x3320646e, 0x79622d32, 0x6b206574,
+	    0x03020100, 0x07060504, 0x0b0a0908, 0x0f0e0d0c,
+	    0x13121110, 0x17161514, 0x1b1a1918, 0x1f1e1d1c,
+	    0x00000001, 0x09000000, 0x4a000000, 0x00000000,
         }};
     struct cc20_state expected = {
-	{0xe4e7f110, 0x15593bd1, 0x1fdd0f50, 0xc47120a3,
-	 0xc7f4d1c7, 0x0368c033, 0x9aaa2204, 0x4e6cd4c3,
-	 0x466482d2, 0x09aa9f07, 0x05d7c214, 0xa2028bd9,
-	 0xd19c12b5, 0xb94e16de, 0xe883d0cb, 0x4e3c50a2,
-	}};
+        .i = {
+            0xe4e7f110, 0x15593bd1, 0x1fdd0f50, 0xc47120a3,
+	    0xc7f4d1c7, 0x0368c033, 0x9aaa2204, 0x4e6cd4c3,
+	    0x466482d2, 0x09aa9f07, 0x05d7c214, 0xa2028bd9,
+	    0xd19c12b5, 0xb94e16de, 0xe883d0cb, 0x4e3c50a2,
+        }};
     uint32_t i;
     struct cc20_state out;
 
@@ -131,13 +131,15 @@ int chacha20_prng_self_test1()
     _dump(&test, "Test vector from RFC7539, section 2.3.2. Input:");
 #endif
 
-    chacha20_prng_block(&test, 1, &out);
+    test.s.counter = 1;		/* nop */
+    chacha20_prng_block(&test, (uint8_t *)&out);
 #ifdef CHACHA20_PRNG_DEBUG
     _dump(&out, "Test vector from RFC7539, section 2.3.2. Output:");
 #endif
 
-    for (i = 0; i < CHACHA20_NUM_WORDS; i++) {
-        if (out.i[i] != expected.i[i]) return 0;
+    for (i = 0; i < CHACHA20_BLOCK_SIZE_WORDS; i++) {
+        if (out.i[i] != expected.i[i])
+            return 0;
     }
 
     return 1;
@@ -149,23 +151,26 @@ int chacha20_prng_self_test2()
      *   https://tools.ietf.org/html/rfc7539#section-2.4.2
      */
     struct cc20_state test = {
-	{0x61707865, 0x3320646e, 0x79622d32, 0x6b206574,
-	 0x03020100, 0x07060504, 0x0b0a0908, 0x0f0e0d0c,
-	 0x13121110, 0x17161514, 0x1b1a1918, 0x1f1e1d1c,
-	 0x00000001, 0x00000000, 0x4a000000, 0x00000000,
-	}};
+        .i = {
+            0x61707865, 0x3320646e, 0x79622d32, 0x6b206574,
+	    0x03020100, 0x07060504, 0x0b0a0908, 0x0f0e0d0c,
+	    0x13121110, 0x17161514, 0x1b1a1918, 0x1f1e1d1c,
+	    0x00000001, 0x00000000, 0x4a000000, 0x00000000,
+        }};
     struct cc20_state expected1 = {
-	{0xf3514f22, 0xe1d91b40, 0x6f27de2f, 0xed1d63b8,
-	 0x821f138c, 0xe2062c3d, 0xecca4f7e, 0x78cff39e,
-	 0xa30a3b8a, 0x920a6072, 0xcd7479b5, 0x34932bed,
-	 0x40ba4c79, 0xcd343ec6, 0x4c2c21ea, 0xb7417df0,
-	}};
+        .i = {
+            0xf3514f22, 0xe1d91b40, 0x6f27de2f, 0xed1d63b8,
+	    0x821f138c, 0xe2062c3d, 0xecca4f7e, 0x78cff39e,
+	    0xa30a3b8a, 0x920a6072, 0xcd7479b5, 0x34932bed,
+	    0x40ba4c79, 0xcd343ec6, 0x4c2c21ea, 0xb7417df0,
+        }};
     struct cc20_state expected2 = {
-	{0x9f74a669, 0x410f633f, 0x28feca22, 0x7ec44dec,
-	 0x6d34d426, 0x738cb970, 0x3ac5e9f3, 0x45590cc4,
-	 0xda6e8b39, 0x892c831a, 0xcdea67c1, 0x2b7e1d90,
-	 0x037463f3, 0xa11a2073, 0xe8bcfb88, 0xedc49139,
-	}};
+        .i = {
+            0x9f74a669, 0x410f633f, 0x28feca22, 0x7ec44dec,
+	    0x6d34d426, 0x738cb970, 0x3ac5e9f3, 0x45590cc4,
+	    0xda6e8b39, 0x892c831a, 0xcdea67c1, 0x2b7e1d90,
+	    0x037463f3, 0xa11a2073, 0xe8bcfb88, 0xedc49139,
+        }};
     struct cc20_state out;
     uint32_t i;
 
@@ -173,20 +178,24 @@ int chacha20_prng_self_test2()
     _dump(&test, "Test vector from RFC7539, section 2.4.2. Input:");
 #endif
 
-    chacha20_prng_block(&test, 1, &out);
+    test.s.counter = 1;		/* nop */
+    chacha20_prng_block(&test, (uint8_t *)&out);
 #ifdef CHACHA20_PRNG_DEBUG
     _dump(&out, "First block");
 #endif
-    for (i = 0; i < CHACHA20_NUM_WORDS; i++) {
-	if (out.i[i] != expected1.i[i]) return 0;
+    for (i = 0; i < CHACHA20_BLOCK_SIZE_WORDS; i++) {
+        if (out.i[i] != expected1.i[i])
+            return 0;
     }
 
-    chacha20_prng_block(&test, 2, &out);
+    test.s.counter = 2;
+    chacha20_prng_block(&test, (uint8_t *)&out);
 #ifdef CHACHA20_PRNG_DEBUG
     _dump(&out, "Second block");
 #endif
-    for (i = 0; i < CHACHA20_NUM_WORDS; i++) {
-	if (out.i[i] != expected2.i[i]) return 0;
+    for (i = 0; i < CHACHA20_BLOCK_SIZE_WORDS; i++) {
+        if (out.i[i] != expected2.i[i])
+            return 0;
     }
 
     return 1;
@@ -201,19 +210,17 @@ void _dump(struct cc20_state *cc, char *str)
     printf("%s\n", str);
 
     for (i = 0; i < 4; i++) {
-	printf("%02i  %08x %08x %08x %08x\n", i * 4, cc->i[i * 4 + 0],
-	       cc->i[i * 4 + 1], cc->i[i * 4 + 2], cc->i[i * 4 + 3]);
+        printf("%02i  %08x %08x %08x %08x\n", i * 4, cc->i[i * 4 + 0],
+               cc->i[i * 4 + 1], cc->i[i * 4 + 2], cc->i[i * 4 + 3]);
     }
     printf("\n");
 }
 #endif
 
-/* Test vector from RFC, used as simple power-on self-test of ability to compute
- * a block correctly.
+/* Test vector from RFC7539, used as simple power-on self-test of
+ * ability to compute a block correctly.
  */
 int chacha20_prng_self_test()
 {
-    return \
-	chacha20_prng_self_test1() && \
-	chacha20_prng_self_test2();
+    return chacha20_prng_self_test1() && chacha20_prng_self_test2();
 }
diff --git a/src/cc20rng/cc20_prng.h b/src/cc20rng/cc20_prng.h
index 6940f53..08f78d7 100644
--- a/src/cc20rng/cc20_prng.h
+++ b/src/cc20rng/cc20_prng.h
@@ -3,16 +3,22 @@
 
 #include <stdint.h>
 
-#define CHACHA20_MAX_BLOCK_COUNTER	0xffffffff
-#define CHACHA20_NUM_WORDS              16
-#define CHACHA20_BLOCK_SIZE		(CHACHA20_NUM_WORDS * 4)
+#define CHACHA20_BLOCK_SIZE_WORDS 16
+#define CHACHA20_BLOCK_SIZE (CHACHA20_BLOCK_SIZE_WORDS * 4)
 
 struct cc20_state {
-    uint32_t i[CHACHA20_NUM_WORDS];
+    union {
+        struct {
+            uint32_t constant[4];
+            uint32_t key[8];
+            uint32_t counter;
+            uint32_t nonce[3];
+        } s;
+        uint32_t i[CHACHA20_BLOCK_SIZE_WORDS];
+    };
 };
 
-extern void chacha20_prng_reseed(struct cc20_state *cc, uint32_t *entropy);
-extern void chacha20_prng_block(struct cc20_state *cc, uint32_t block_counter, struct cc20_state *out);
-extern int chacha20_prng_self_test();
+void chacha20_prng_block(struct cc20_state *cc, uint8_t *out);
+int chacha20_prng_self_test();
 
 #endif /* __STM32_CHACHA20_H */
diff --git a/src/cc20rng/main.c b/src/cc20rng/main.c
index e478409..cc063f4 100644
--- a/src/cc20rng/main.c
+++ b/src/cc20rng/main.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2014, 2015, 2016 NORDUnet A/S
+ * Copyright (c) 2019 Sunet
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or
@@ -31,12 +32,11 @@
  */
 #include <string.h>
 
-#include "main.h"
-#include "stm_init.h"
 #include "cc20_prng.h"
+#include "stm_init.h"
 
-#define UART_RANDOM_BYTES_PER_CHUNK	8
-#define RESEED_BLOCKS			CHACHA20_MAX_BLOCK_COUNTER
+#define UART_RANDOM_BYTES_PER_CHUNK 8
+#define RESEED_BLOCKS CHACHA20_MAX_BLOCK_COUNTER
 
 extern DMA_HandleTypeDef hdma_tim;
 
@@ -44,19 +44,22 @@ static UART_HandleTypeDef *huart;
 static __IO ITStatus UartReady = RESET;
 
 static union {
-  uint8_t rnd[257];		/* 256 bytes + 1 for use in the POST */
+  uint8_t rnd[257]; /* 256 bytes + 1 for use in the POST */
   uint32_t rnd32[64];
 } buf;
 
-/* First DMA value (DMA_counters[0]) is unreliable, leftover in DMA FIFO perhaps? */
-#define FIRST_DMA_IDX_USED  3
+/* First DMA value (DMA_counters[0]) is unreliable, leftover in DMA FIFO
+ * perhaps? */
+#define FIRST_DMA_IDX_USED 3
 
 /*
  * Number of counters used to produce 8 bits of entropy is:
- *   8 * 4 - four flanks are used to produce two (hopefully) uncorrelated bits (a and b)
+ *   8 * 4 - four flanks are used to produce two (hopefully) uncorrelated bits
+ * (a and b)
  *     * 2 - von Neumann will on average discard 1/2 of the bits 'a' and 'b'
  */
-#define DMA_COUNTERS_NUM ((UART_RANDOM_BYTES_PER_CHUNK * 8 * 4 * 2) + FIRST_DMA_IDX_USED + 1)
+#define DMA_COUNTERS_NUM                                                       \
+  ((UART_RANDOM_BYTES_PER_CHUNK * 8 * 4 * 2) + FIRST_DMA_IDX_USED + 1)
 struct DMA_params {
   volatile uint32_t buf0[DMA_COUNTERS_NUM];
   volatile uint32_t buf1[DMA_COUNTERS_NUM];
@@ -64,30 +67,26 @@ struct DMA_params {
 };
 
 static struct DMA_params DMA = {
-  {},
-  {},
-  0,
+    {}, {}, 0,
 };
 
-
 /* The main work horse functions */
 static void get_entropy32(uint32_t num_bytes, uint32_t buf_idx);
 /* Various support functions */
 static inline uint32_t get_one_bit(void) __attribute__((__always_inline__));
 static volatile uint32_t *restart_DMA(void);
 static inline volatile uint32_t *get_DMA_read_buf(void);
-static inline uint32_t safe_get_counter(volatile uint32_t *dmabuf, const uint32_t dmabuf_idx);
+static inline uint32_t safe_get_counter(volatile uint32_t *dmabuf,
+                                        const uint32_t dmabuf_idx);
 static void check_uart_rx(UART_HandleTypeDef *this);
-static void cc_reseed(struct cc20_state *cc);
+static uint32_t cc_reseed(struct cc20_state *cc);
 
 void Error_Handler(void);
 
-
-int
-main()
-{
-  uint32_t i, timeout, block_counter = 0;
-  struct cc20_state cc, out;
+int main() {
+  uint32_t i, timeout, block_counter;
+  struct cc20_state cc_state = {0};
+  uint8_t cc_result[CHACHA20_BLOCK_SIZE];
   HAL_StatusTypeDef res;
 
   /* Initialize buffers */
@@ -97,10 +96,10 @@ main()
     DMA.buf1[i] = 0xffff0100 + i;
   }
 
-  stm_init((uint32_t *) &DMA.buf0, DMA_COUNTERS_NUM);
+  stm_init((uint32_t *)&DMA.buf0, DMA_COUNTERS_NUM);
 
-  if (! chacha20_prng_self_test()) {
-      Error_Handler();
+  if (!chacha20_prng_self_test()) {
+    Error_Handler();
   }
 
   /* Ensure there is actual Timer IC counters in both DMA buffers. */
@@ -110,47 +109,37 @@ main()
   huart = &huart1;
 
   /* Toggle GREEN LED to show we've initialized */
-  {
-    for (i = 0; i < 10; i++) {
-      HAL_GPIO_TogglePin(LED_PORT, LED_GREEN);
-      HAL_Delay(125);
-    }
+  for (i = 0; i < 10; i++) {
+    HAL_GPIO_TogglePin(LED_PORT, LED_GREEN);
+    HAL_Delay(125);
   }
 
-  /* Generate initial block of random data directly into buf */
-  cc_reseed(&cc);
-  block_counter = RESEED_BLOCKS;
-  chacha20_prng_block(&cc, block_counter--, (struct cc20_state *) buf.rnd32);
+  /* Generate initial block of ChaCha20 output directly into buf. */
+  block_counter = cc_reseed(&cc_state);
+  chacha20_prng_block(&cc_state, buf.rnd);
+  block_counter--;
 
-  /*
-   * Main loop
-   */
+  /* Main loop */
   while (1) {
-    if (! (block_counter % 1000)) {
+    if (!(block_counter % 1000))
       HAL_GPIO_TogglePin(LED_PORT, LED_YELLOW);
-    }
-
-    if (! block_counter) {
-	cc_reseed(&cc);
-	block_counter = RESEED_BLOCKS;
-    }
 
     /* Send buf on UART (non blocking interrupt driven send). */
     UartReady = RESET;
-    res = HAL_UART_Transmit_IT(huart, &buf.rnd[0], CHACHA20_BLOCK_SIZE);
+    res = HAL_UART_Transmit_IT(huart, buf.rnd, CHACHA20_BLOCK_SIZE);
 
     /* Generate next block while this block is being transmitted */
-    chacha20_prng_block(&cc, block_counter--, &out);
-    /* Copying using a loop is faster than memcpy on STM32 */
-    for (i = 0; i < CHACHA20_NUM_WORDS; i++) {
-	buf.rnd32[i] = out.i[i];
-    }
+    if (!block_counter)
+      block_counter = cc_reseed(&cc_state);
+    chacha20_prng_block(&cc_state, cc_result);
+    block_counter--;
 
+    /* Wait for transfer to complete. */
     if (res == HAL_OK) {
       timeout = 0xffff;
-      while (UartReady != SET && timeout) { timeout--; }
+      while (UartReady != SET && timeout)
+        timeout--;
     }
-
     if (UartReady != SET) {
       /* Failed to send, turn on RED LED for one second */
       HAL_GPIO_WritePin(LED_PORT, LED_RED, GPIO_PIN_SET);
@@ -158,28 +147,31 @@ main()
       HAL_GPIO_WritePin(LED_PORT, LED_RED, GPIO_PIN_RESET);
     }
 
+    /* Fill buffer with ChaCha20 output. */
+    for (i = 0; i < CHACHA20_BLOCK_SIZE; i++)
+      buf.rnd[i] = cc_result[i];
+
     /* Check for UART change request */
     check_uart_rx(&huart1);
     check_uart_rx(&huart2);
   }
 }
 
-
 /**
  * @brief  Reseed chacha20 state with hardware generated entropy.
  * @param  cc: ChaCha20 state
- * @retval None
+ * @retval ChaCha20 block counter
  */
-static void
-cc_reseed(struct cc20_state *cc)
-{
-    HAL_GPIO_WritePin(LED_PORT, LED_BLUE, GPIO_PIN_SET);
+static uint32_t cc_reseed(struct cc20_state *cc) {
+  HAL_GPIO_WritePin(LED_PORT, LED_BLUE, GPIO_PIN_SET);
 
-    get_entropy32(CHACHA20_BLOCK_SIZE / 4, 0);
-    restart_DMA();
-    chacha20_prng_reseed(cc, (uint32_t *) &buf);
+  get_entropy32(CHACHA20_BLOCK_SIZE_WORDS, 0);
+  restart_DMA();
+  memcpy(cc, buf.rnd, CHACHA20_BLOCK_SIZE);
+
+  HAL_GPIO_WritePin(LED_PORT, LED_BLUE, GPIO_PIN_RESET);
 
-    HAL_GPIO_WritePin(LED_PORT, LED_BLUE, GPIO_PIN_RESET);
+  return cc->s.counter;
 }
 
 /**
@@ -188,16 +180,14 @@ cc_reseed(struct cc20_state *cc)
  * @param  start: Start index value into buf.rnd32.
  * @retval None
  */
-static inline void get_entropy32(uint32_t count, const uint32_t start)
-{
+static inline void get_entropy32(uint32_t count, const uint32_t start) {
   uint32_t i, bits, buf_idx;
 
   buf_idx = start;
 
   do {
     bits = 0;
-    /* Get 32 bits of entropy.
-     */
+    /* Get 32 bits of entropy. */
     for (i = 32; i; i--) {
       bits <<= 1;
       bits += get_one_bit();
@@ -213,8 +203,7 @@ static inline void get_entropy32(uint32_t count, const uint32_t start)
  * @param  None
  * @retval One bit, in the LSB of an uint32_t since this is a 32 bit MCU.
  */
-static inline uint32_t get_one_bit()
-{
+static inline uint32_t get_one_bit() {
   register uint32_t a, b, temp;
   /* Start at end of buffer so restart_DMA() is called. */
   static uint32_t dmabuf_idx = DMA_COUNTERS_NUM - 1;
@@ -264,8 +253,7 @@ static inline uint32_t get_one_bit()
  * @param  None
  * @retval Pointer to buffer currently being read from.
  */
-static inline volatile uint32_t *get_DMA_read_buf(void)
-{
+static inline volatile uint32_t *get_DMA_read_buf(void) {
   return DMA.write_buf ? DMA.buf0 : DMA.buf1;
 }
 
@@ -274,8 +262,7 @@ static inline volatile uint32_t *get_DMA_read_buf(void)
  * @param  None
  * @retval Pointer to buffer currently being written to.
  */
-static inline volatile uint32_t *get_DMA_write_buf(void)
-{
+static inline volatile uint32_t *get_DMA_write_buf(void) {
   return DMA.write_buf ? DMA.buf1 : DMA.buf0;
 }
 
@@ -284,16 +271,17 @@ static inline volatile uint32_t *get_DMA_write_buf(void)
  * @param  None
  * @retval Pointer to buffer full of Timer IC values ready to be consumed.
  */
-static volatile uint32_t *restart_DMA(void)
-{
+static volatile uint32_t *restart_DMA(void) {
   /* Wait for transfer complete flag to become SET. Trying to change the
    * M0AR register while the DMA is running is a no-no.
    */
-  while(__HAL_DMA_GET_FLAG(&hdma_tim, __HAL_DMA_GET_TC_FLAG_INDEX(&hdma_tim)) == RESET) { ; }
+  while (__HAL_DMA_GET_FLAG(&hdma_tim,
+                            __HAL_DMA_GET_TC_FLAG_INDEX(&hdma_tim)) == RESET)
+    ;
 
   /* Switch buffer being written to */
   DMA.write_buf ^= 1;
-  hdma_tim.Instance->M0AR = (uint32_t) get_DMA_write_buf();
+  hdma_tim.Instance->M0AR = (uint32_t)get_DMA_write_buf();
 
   /* Start at 0 to help manual inspection */
   TIM2->CNT = 0;
@@ -311,7 +299,8 @@ static volatile uint32_t *restart_DMA(void)
  * @param  dmabuf_idx: Word index into `dmabuf'.
  * @retval One Timer IC counter value.
  */
-static inline uint32_t safe_get_counter(volatile uint32_t *dmabuf, const uint32_t dmabuf_idx) {
+static inline uint32_t safe_get_counter(volatile uint32_t *dmabuf,
+                                        const uint32_t dmabuf_idx) {
   register uint32_t a;
   /* Prevent re-use of values. DMA stored values are <= 0xffff. */
   do {
@@ -322,8 +311,7 @@ static inline uint32_t safe_get_counter(volatile uint32_t *dmabuf, const uint32_
 }
 
 /* UART transmit complete callback */
-void HAL_UART_TxCpltCallback(UART_HandleTypeDef *UH)
-{
+void HAL_UART_TxCpltCallback(UART_HandleTypeDef *UH) {
   if ((UH->Instance == USART1 && huart->Instance == USART1) ||
       (UH->Instance == USART2 && huart->Instance == USART2)) {
     /* Signal UART transmit complete to the code in the main loop. */
@@ -350,10 +338,9 @@ static void check_uart_rx(UART_HandleTypeDef *this) {
  * @param  None
  * @retval None
  */
-
-void Error_Handler(void)
-{
+void Error_Handler(void) {
   /* Turn on RED LED and then loop indefinitely */
   HAL_GPIO_WritePin(LED_PORT, LED_RED, GPIO_PIN_SET);
-  while(1) { ; }
+  while (1)
+    ;
 }
diff --git a/src/cc20rng/main.h b/src/cc20rng/main.h
deleted file mode 100644
index 902ecf4..0000000
--- a/src/cc20rng/main.h
+++ /dev/null
@@ -1,4 +0,0 @@
-#ifndef __MAIN_H
-#define __MAIN_H
-
-#endif /* __MAIN_H */
diff --git a/src/cc20rng/stm32f4xx_it.h b/src/cc20rng/stm32f4xx_it.h
index 04c5a36..6edba3c 100644
--- a/src/cc20rng/stm32f4xx_it.h
+++ b/src/cc20rng/stm32f4xx_it.h
@@ -44,8 +44,6 @@
 #endif
 
 /* Includes ------------------------------------------------------------------*/
-#include "main.h"
-
 /* Exported types ------------------------------------------------------------*/
 /* Exported constants --------------------------------------------------------*/
 /* Exported macro ------------------------------------------------------------*/