Fix slice index out of range panic possibilities

internal/matchers/text.go

@@ -163,10 +163,10 @@ func Json(in []byte) bool {
 //
 // BUG(gabriel-vasile): The "type" key should be searched for in the root object.
 func GeoJson(in []byte) bool {
+	in = trimLWS(in)
 	if len(in) == 0 {
 		return false
 	}
-	in = trimLWS(in)
 	// geojson is always an object
 	if in[0] != '{' {
 		return false

internal/matchers/video.go

@@ -31,13 +31,12 @@ func isMatroskaFileTypeMatched(in []byte, flType string) bool {
 // The logic of search is: find first instance of \x42\x82 and then
 // search for given string after one byte of above instance.
 func isFileTypeNamePresent(in []byte, flType string) bool {
-	var ind int
-	if len(in) >= 4096 { // restricting length to 4096
-		ind = bytes.Index(in[0:4096], []byte("\x42\x82"))
-	} else {
-		ind = bytes.Index(in, []byte("\x42\x82"))
+	ind, maxInd, lenIn := 0, 4096, len(in)
+	if lenIn < maxInd { // restricting length to 4096
+		maxInd = lenIn
 	}
-	if ind > 0 {
+	ind = bytes.Index(in[:maxInd], []byte("\x42\x82"))
+	if ind > 0 && lenIn > ind+3 {
 		// filetype name will be present exactly
 		// one byte after the match of the two bytes "\x42\x82"
 		return bytes.HasPrefix(in[ind+3:], []byte(flType))
@@ -52,7 +51,7 @@ func Flv(in []byte) bool {
 
 // Mpeg matches a Moving Picture Experts Group file.
 func Mpeg(in []byte) bool {
-	return bytes.HasPrefix(in, []byte{0x00, 0x00, 0x01}) &&
+	return len(in) > 3 && bytes.HasPrefix(in, []byte{0x00, 0x00, 0x01}) &&
 		in[3] >= 0xB0 && in[3] <= 0xBF
 }