Fix strncat/cpy bounding issues (fix #1425)

ChangeLog

@@ -2,6 +2,7 @@
             nRF5x: Make FlashWrite cope with flash writes > 4k
             Increase max size of native strings on platforms that support it - 16 bit to 32 bit (#1432)
             Fix stack size detection on Linux (fix #1427)
+            Fix strncat/cpy bounding issues (fix #1425)
 
      1v98 : Allow Crypto SHA1 without SHA256/512 (for ESP8266 where flash is scarce)
             Add better docs for the form of Wifi callback functions

src/jslex.c

@@ -814,19 +814,14 @@ void jslTokenAsString(int token, char *str, size_t len) {
   }
 
   assert(len>=10);
-  strncpy(str, "?[",len);
-  itostr(token, &str[2], 10);
-  strncat(str, "]",len);
+  espruino_snprintf(str, len, "?[%d]", token);
 }
 
 void jslGetTokenString(char *str, size_t len) {
   if (lex->tk == LEX_ID) {
-    strncpy(str, "ID:", len);
-    strncat(str, jslGetTokenValueAsString(), len);
+    espruino_snprintf(str, len, "ID:%s", jslGetTokenValueAsString());
   } else if (lex->tk == LEX_STR) {
-    strncpy(str, "String:'", len);
-    strncat(str, jslGetTokenValueAsString(), len);
-    strncat(str, "'", len);
+    espruino_snprintf(str, len, "String:'%s'", jslGetTokenValueAsString());
   } else
     jslTokenAsString(lex->tk, str, len);
 }

src/jspin.c

@@ -179,7 +179,7 @@ void jshGetPinString(char *result, Pin pin) {
 #endif
 #endif
     } else {
-      strncpy(result, "undefined", 10);
+      strcpy(result, "undefined");
     }
   }
 
@@ -379,10 +379,10 @@ void jshPinFunctionToString(JshPinFunction pinFunc, JshPinFunctionToStringFlags
     jsiConsolePrintf("Couldn't convert pin function %d\n", pinFunc);
     return;
   }
-  if (flags & JSPFTS_DEVICE) strncat(buf, devStr, bufSize);
+  if (flags & JSPFTS_DEVICE) strncat(buf, devStr, bufSize-1);
   if (flags & JSPFTS_DEVICE_NUMBER) itostr(devIdx, &buf[strlen(buf)], 10);
-  if (flags & JSPFTS_SPACE) strncat(buf, " ", bufSize);
-  if (infoStr && (flags & JSPFTS_TYPE)) strncat(buf, infoStr, bufSize);
+  if (flags & JSPFTS_SPACE) strncat(buf, " ", bufSize-(strlen(buf)+1));
+  if (infoStr && (flags & JSPFTS_TYPE)) strncat(buf, infoStr, bufSize-(strlen(buf)+1));
 }
 
 /** Prints a list of capable pins, eg:

src/jsutils.c

@@ -604,11 +604,12 @@ void itostr_extra(JsVarInt vals,char *str,bool signedVal, unsigned int base) {
 }
 
 void ftoa_bounded_extra(JsVarFloat val,char *str, size_t len, int radix, int fractionalDigits) {
+  assert(len>9); // in case if strcpy
   const JsVarFloat stopAtError = 0.0000001;
-  if (isnan(val)) strncpy(str,"NaN",len);
+  if (isnan(val)) strcpy(str,"NaN");
   else if (!isfinite(val)) {
-    if (val<0) strncpy(str,"-Infinity",len);
-    else strncpy(str,"Infinity",len);
+    if (val<0) strcpy(str,"-Infinity");
+    else strcpy(str,"Infinity");
   } else {
     if (val<0) {
       if (--len <= 0) { *str=0; return; } // bounds check

src/jsvar.c

@@ -1186,6 +1186,7 @@ size_t jsvGetString(const JsVar *v, char *str, size_t len) {
   const char *s = jsvGetConstString(v);
   if (s) {
     strncpy(str, s, len);
+    str[len-1] = 0;
     return strlen(s);
   } else if (jsvIsInt(v)) {
     itostr(v->varData.integer, str, 10);
@@ -1218,7 +1219,7 @@ size_t jsvGetString(const JsVar *v, char *str, size_t len) {
       jsvUnLock(stringVar);
       return l;
     } else {
-      strncpy(str, "", len);
+      str[0] = 0;
       jsExceptionHere(JSET_INTERNALERROR, "Variable type cannot be converted to string");
       return 0;
     }