refactor so ykpiv_sign_data() takes size_t input

lib/ykpiv.c

@@ -464,7 +464,7 @@ ykpiv_rc ykpiv_parse_key(ykpiv_state *state,
 }
 
 ykpiv_rc ykpiv_sign_data(ykpiv_state *state,
-    const unsigned char *raw_in, int in_len,
+    const unsigned char *raw_in, size_t in_len,
     unsigned char *sign_out, size_t *out_len,
     unsigned char algorithm, unsigned char key) {
 

lib/ykpiv.h

@@ -73,7 +73,7 @@ extern "C"
 	ykpiv_rc ykpiv_parse_key(ykpiv_state *state,
 			const char *key_in, unsigned char *key_out);
 	ykpiv_rc ykpiv_sign_data(ykpiv_state *state, const unsigned char *sign_in,
-			int in_len,unsigned char *sign_out, size_t *out_len,
+			size_t in_len,unsigned char *sign_out, size_t *out_len,
 			unsigned char algorithm, unsigned char key);
 	ykpiv_rc ykpiv_get_version(ykpiv_state *state, char *version, size_t len);
 	ykpiv_rc ykpiv_verify(ykpiv_state *state, const char *pin, int *tries);

tool/yubico-piv-tool.c

@@ -514,7 +514,7 @@ static bool request_certificate(ykpiv_state *state, enum enum_key_format key_for
   unsigned char algorithm;
   int key = 0;
   unsigned char *signinput;
-  int len = 0;
+  size_t len = 0;
 
   sscanf(slot, "%x", &key);
 
@@ -636,7 +636,7 @@ static bool selfsign_certificate(ykpiv_state *state, enum enum_key_format key_fo
   unsigned char algorithm;
   int key = 0;
   unsigned char *signinput;
-  int len = 0;
+  size_t len = 0;
 
   sscanf(slot, "%x", &key);