Fix to resolve STM32 hash FIFO. Simplify logic for ensuring FIFO gets filled before doing a save/restore. ZD 18294

wolfcrypt/src/port/st/stm32.c

@@ -303,12 +303,11 @@ int wc_Stm32_Hash_Update(STM32_HASH_Context* stmCtx, word32 algo,
     int ret = 0;
     byte* local = (byte*)stmCtx->buffer;
     int wroteToFifo = 0;
-    const word32 fifoSz = (STM32_HASH_FIFO_SIZE * STM32_HASH_REG_SIZE);
     word32 chunkSz;
 
 #ifdef DEBUG_STM32_HASH
-    printf("STM Hash Update: algo %x, len %d, blockSz %d\n",
+    printf("STM Hash Update: algo %x, len %d, buffLen %d, fifoBytes %d\n",
-        algo, len, blockSize);
+        algo, len, stmCtx->buffLen, stmCtx->fifoBytes);
 #endif
     (void)blockSize;
 
@@ -323,40 +322,27 @@ int wc_Stm32_Hash_Update(STM32_HASH_Context* stmCtx, word32 algo,
     /* restore hash context or init as new hash */
     wc_Stm32_Hash_RestoreContext(stmCtx, algo);
 
-    chunkSz = fifoSz;
-#ifdef STM32_HASH_FIFO_WORKAROUND
-    /* if FIFO already has bytes written then fill remainder first */
-    if (stmCtx->fifoBytes > 0) {
-        chunkSz -= stmCtx->fifoBytes;
-        stmCtx->fifoBytes = 0;
-    }
-#endif
-
     /* write blocks to FIFO */
     while (len) {
-        word32 add = min(len, chunkSz - stmCtx->buffLen);
+        word32 add;
+
+        /* fill the FIFO plus one additional to flush the block */
+        chunkSz = ((STM32_HASH_FIFO_SIZE + 1) * STM32_HASH_REG_SIZE);
+        /* account for extra bytes in the FIFO (use mask 0x3F to get remain) */
+        chunkSz -= (stmCtx->fifoBytes &
+            ((STM32_HASH_FIFO_SIZE * STM32_HASH_REG_SIZE)-1));
+
+        add = min(len, chunkSz - stmCtx->buffLen);
         XMEMCPY(&local[stmCtx->buffLen], data, add);
 
         stmCtx->buffLen += add;
         data            += add;
         len             -= add;
 
-    #ifdef STM32_HASH_FIFO_WORKAROUND
-        /* We cannot leave the FIFO full and do save/restore
-         * the last must be large enough to flush block from FIFO */
-        if (stmCtx->buffLen + len <= fifoSz * 2) {
-            chunkSz = fifoSz + STM32_HASH_REG_SIZE;
-        }
-    #endif
-
         if (stmCtx->buffLen == chunkSz) {
             wc_Stm32_Hash_Data(stmCtx, stmCtx->buffLen);
             wroteToFifo = 1;
-        #ifdef STM32_HASH_FIFO_WORKAROUND
+            stmCtx->fifoBytes += chunkSz;
-            if (chunkSz > fifoSz)
-                stmCtx->fifoBytes = chunkSz - fifoSz;
-            chunkSz = fifoSz;
-        #endif
         }
     }
 
@@ -380,7 +366,8 @@ int wc_Stm32_Hash_Final(STM32_HASH_Context* stmCtx, word32 algo,
     int ret = 0;
 
 #ifdef DEBUG_STM32_HASH
-    printf("STM Hash Final: algo %x, digestSz %d\n", algo, digestSize);
+    printf("STM Hash Final: algo %x, digestSz %d, buffLen %d, fifoBytes %d\n",
+        algo, digestSize, stmCtx->buffLen, stmCtx->fifoBytes);
 #endif
 
     /* turn on hash clock */

wolfcrypt/src/sha256.c

@@ -2496,7 +2496,7 @@ int wc_Sha256GetHash(wc_Sha256* sha256, byte* hash)
     ret = wc_Sha256Copy(sha256, tmpSha256);
     if (ret == 0) {
         ret = wc_Sha256Final(tmpSha256, hash);
-        wc_Sha256Free(tmpSha256); /* TODO move outside brackets? */
+        wc_Sha256Free(tmpSha256);
     }
 
 

wolfssl/wolfcrypt/port/st/stm32.h

@@ -71,26 +71,6 @@
 #define STM32_HASH_REG_SIZE  4
 #define STM32_HASH_FIFO_SIZE 16 /* FIFO is 16 deep 32-bits wide */
 
-#if (defined(WOLFSSL_STM32U5) || defined(WOLFSSL_STM32H5) || \
-    defined(WOLFSSL_STM32H7)) && !defined(NO_STM32_HASH_FIFO_WORKAROUND)
-    /* workaround for hash FIFO to write one extra to finalize */
-    /* RM: Message Data Feeding: Data are entered into the HASH
-     * one 32-bit word at a time, by writing them into the HASH_DIN register.
-     * The current contents of the HASH_DIN register are transferred to the
-     * 16 words input FIFO each time the register is written with new data.
-     * Hence HASH_DIN and the FIFO form a seventeen 32-bit words length FIFO. */
-    #undef  STM32_HASH_BUFFER_SIZE
-    #define STM32_HASH_BUFFER_SIZE 17
-
-    #undef  STM32_HASH_FIFO_WORKAROUND
-    #define STM32_HASH_FIFO_WORKAROUND
-#endif
-
-#ifndef STM32_HASH_BUFFER_SIZE
-#define STM32_HASH_BUFFER_SIZE STM32_HASH_FIFO_SIZE
-#endif
-
-
 /* STM32 Hash Context */
 typedef struct {
     /* Context switching registers */
@@ -100,13 +80,11 @@ typedef struct {
     uint32_t HASH_CSR[HASH_CR_SIZE];
 
     /* Hash state / buffers */
-    word32 buffer[STM32_HASH_BUFFER_SIZE]; /* partial word buffer */
+    word32 buffer[STM32_HASH_FIFO_SIZE+1]; /* partial word buffer */
     word32 buffLen; /* partial word remain */
     word32 loLen;   /* total update bytes
                  (only lsb 6-bits is used for nbr valid bytes in last word) */
-#ifdef STM32_HASH_FIFO_WORKAROUND
+    word32 fifoBytes; /* number of currently filled FIFO bytes */
-    int    fifoBytes; /* number of currently filled FIFO bytes */
-#endif
 } STM32_HASH_Context;