Merge pull request #241 from gabriel-vasile/dbf

Fix json detected as dbf when it starts with low ascii values

internal/magic/binary.go

@@ -64,16 +64,27 @@ func MachO(raw []byte, limit uint32) bool {
 // Dbf matches a dBase file.
 // https://www.dbase.com/Knowledgebase/INT/db7_file_fmt.htm
 func Dbf(raw []byte, limit uint32) bool {
- if len(raw) < 4 {
+ if len(raw) < 68 {
  return false
  }
 
- // 3rd and 4th bytes contain the last update month and day of month
+ // 3rd and 4th bytes contain the last update month and day of month.
  if !(0 < raw[2] && raw[2] < 13 && 0 < raw[3] && raw[3] < 32) {
  return false
  }
 
- // dbf type is dictated by the first byte
+ // 12, 13, 30, 31 are reserved bytes and always filled with 0x00.
+ if raw[12] != 0x00 || raw[13] != 0x00 || raw[30] != 0x00 || raw[31] != 0x00 {
+ return false
+ }
+ // Production MDX flag;
+ // 0x01 if a production .MDX file exists for this table;
+ // 0x00 if no .MDX file exists.
+ if raw[28] > 0x01 {
+ return false
+ }
+
+ // dbf type is dictated by the first byte.
  dbfTypes := []byte{
  0x02, 0x03, 0x04, 0x05, 0x30, 0x31, 0x32, 0x42, 0x62, 0x7B, 0x82,
  0x83, 0x87, 0x8A, 0x8B, 0x8E, 0xB3, 0xCB, 0xE5, 0xF5, 0xF4, 0xFB,

mimetype_test.go

@@ -94,6 +94,7 @@ var files = map[string]string{
  "xpm.xpm": "image/x-xpixmap",
  "js.js": "application/javascript",
  "json.json": "application/json",
+ "json.lowascii.json": "application/json",
  // json.{int,float,string}.txt contain a single JSON value. They are valid JSON
  // documents, but they should not be detected as application/json. This mimics
  // the behaviour of the file utility and seems the correct thing to do.

testdata/json.lowascii.json

@@ -0,0 +1,2 @@
+{
+ "fixture for issue #": 239}