--- a/buffer.c	Tue Jan 23 22:44:18 2018 +0800
+++ b/buffer.c	Thu Jan 25 21:55:25 2018 +0800
@@ -67,7 +67,7 @@
 }
 
 /* overwrite the contents of the buffer to clear it */
-void buf_burn(buffer* buf) {
+void buf_burn(const buffer* buf) {
 	
 	m_burn(buf->data, buf->size);
 
@@ -91,7 +91,7 @@
 
 /* Create a copy of buf, allocating required memory etc. */
 /* The new buffer is sized the same as the length of the source buffer. */
-buffer* buf_newcopy(buffer* buf) {
+buffer* buf_newcopy(const buffer* buf) {
 	
 	buffer* ret;
 
@@ -184,7 +184,7 @@
 
 /* returns an in-place pointer to the buffer, checking that
  * the next len bytes from that position can be used */
-unsigned char* buf_getptr(buffer* buf, unsigned int len) {
+unsigned char* buf_getptr(const buffer* buf, unsigned int len) {
 
 	if (len > BUF_MAX_INCR || buf->pos + len > buf->len) {
 		dropbear_exit("Bad buf_getptr");
@@ -194,7 +194,7 @@
 
 /* like buf_getptr, but checks against total size, not used length.
  * This allows writing past the used length, but not past the size */
-unsigned char* buf_getwriteptr(buffer* buf, unsigned int len) {
+unsigned char* buf_getwriteptr(const buffer* buf, unsigned int len) {
 
 	if (len > BUF_MAX_INCR || buf->pos + len > buf->size) {
 		dropbear_exit("Bad buf_getwriteptr");