Change the static buffer size so it is easily reset on configure. Not…

…e, this doesn't play nice at the moment.

src/internal.c

@@ -150,6 +150,11 @@
   WOLFSSH_NO_CURVE25519_SHA256
     Set when Curve25519 or SHA2-256 are disabled in wolfSSL. Set to disable use
     of Curve25519 key exchange.
+  WOLFSSH_STATIC_BUFFER_LEN
+    Set to change the size of the static buffer used in the WOLFSSH_BUFFER
+    structure. This must be at least AES_BLOCK_SIZE. When larger, it will
+    reduce the chance that a dynamic receive buffer would need to be
+    allocated.
 */
 
 static const char sshProtoIdStr[] = "SSH-2.0-wolfSSHv"
@@ -2844,13 +2849,13 @@ int BufferInit(WOLFSSH_BUFFER* buffer, word32 size, void* heap)
     if (buffer == NULL)
         return WS_BAD_ARGUMENT;
 
-    if (size <= STATIC_BUFFER_LEN)
-        size = STATIC_BUFFER_LEN;
+    if (size <= WOLFSSH_STATIC_BUFFER_LEN)
+        size = WOLFSSH_STATIC_BUFFER_LEN;
 
     WMEMSET(buffer, 0, sizeof(WOLFSSH_BUFFER));
     buffer->heap = heap;
     buffer->bufferSz = size;
-    if (size > STATIC_BUFFER_LEN) {
+    if (size > WOLFSSH_STATIC_BUFFER_LEN) {
         buffer->buffer = (byte*)WMALLOC(size, heap, DYNTYPE_BUFFER);
         if (buffer->buffer == NULL)
             return WS_MEMORY_E;
@@ -2924,7 +2929,7 @@ void ShrinkBuffer(WOLFSSH_BUFFER* buf, int forcedFree)
         WLOG(WS_LOG_DEBUG, "SB: usedSz = %u, forcedFree = %u",
              usedSz, forcedFree);
 
-        if (!forcedFree && usedSz > STATIC_BUFFER_LEN)
+        if (!forcedFree && usedSz > WOLFSSH_STATIC_BUFFER_LEN)
             return;
 
         if (!forcedFree && usedSz) {
@@ -2938,7 +2943,7 @@ void ShrinkBuffer(WOLFSSH_BUFFER* buf, int forcedFree)
         }
         buf->dynamicFlag = 0;
         buf->buffer = buf->staticBuffer;
-        buf->bufferSz = STATIC_BUFFER_LEN;
+        buf->bufferSz = WOLFSSH_STATIC_BUFFER_LEN;
         buf->length = forcedFree ? 0 : usedSz;
         buf->idx = 0;
     }

wolfssh/internal.h

@@ -449,10 +449,16 @@ WOLFSSH_LOCAL const char* IdToName(byte id);
 WOLFSSH_LOCAL const char* NameByIndexType(byte type, word32* index);
 
 
-#define STATIC_BUFFER_LEN AES_BLOCK_SIZE
 /* This is one AES block size. We always grab one
  * block size first to decrypt to find the size of
  * the rest of the data. */
+#ifndef WOLFSSH_STATIC_BUFFER_LEN
+    #define WOLFSSH_STATIC_BUFFER_LEN AES_BLOCK_SIZE
+#endif
+
+#if WOLFSSH_STATIC_BUFFER_LEN < AES_BLOCK_SIZE
+    #error "WOLFSSH_STATIC_BUFFER_LEN must be at least 16"
+#endif
 
 
 typedef struct WOLFSSH_BUFFER {
@@ -462,7 +468,7 @@ typedef struct WOLFSSH_BUFFER {
     word32 idx;       /* idx to part of length already consumed */
     byte* buffer;     /* place holder for actual buffer */
     word32 bufferSz;  /* current buffer size */
-    ALIGN16 byte staticBuffer[STATIC_BUFFER_LEN];
+    ALIGN16 byte staticBuffer[WOLFSSH_STATIC_BUFFER_LEN];
     byte dynamicFlag; /* dynamic memory currently in use */
 } WOLFSSH_BUFFER;