Improve detection of msdos backup files. Joerg Jenderek

diff --git a/magic/Magdir/msdos b/magic/Magdir/msdos
index e383b9d14429cdd2aab9a4319ac6acb3bf35522d..841d62ebccfe80f2c263e0aeb902adf9b6391d02 100644 (file)
--- a/magic/Magdir/msdos
+++ b/magic/Magdir/msdos
@@ -1,6 +1,6 @@
 
 #------------------------------------------------------------------------------
-# $File: msdos,v 1.117 2017/03/17 21:35:28 christos Exp $
+# $File: msdos,v 1.118 2017/05/20 19:55:27 christos Exp $
 # msdos:  file(1) magic for MS-DOS files
 #
 
@@ -1151,14 +1151,40 @@
 
 # backed up file
 
+# skip some AppleWorks word like Tomahawk.Awp, WIN98SE-DE.vhd
+# by looking for trailing nul of maximal file name string
+0x52   ubyte   0       
+# test for flag byte: FFh~complete file, 00h~split file
+# FFh -127 =   -1 -127 =       -128
+# 00h -127 =    0 -127 =       -127
+>0     byte-127        <-126
 # plausibility check for file name length
-0x53   ubyte-1 <80
-# actually 54 nul bytes
->0x54  string  \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0
->>0x5  string  x       DOS 2.0 backed up file %s,
->>0    ubyte   0xff    complete file
->>0    ubyte   !0xff
->>>1   ushort  x       split file, sequence %d
+>>0x53 ubyte-1 <78     
+# looking for terminating nul of file name string
+>>>(0x53.b+4)  ubyte   0       
+# looking if last char of string is valid DOS file name
+>>>>(0x53.b+3) ubyte   >0x1F   
+# actually 44 nul bytes
+# but sometimes garbage according to Ralf Quint. So can not be used as test
+#>0x54 string  \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0
+# first char of full file name is DOS (5Ch) or UNIX (2Fh) path separator
+# only DOS variant found. UNIX variant according to V32SLASH.TXT in archive PD0315.EXE 
+>>>>>5 ubyte&0x8C      0x0C    
+# ./msdos (version 5.30) labeled the entry as
+# "DOS 2.0 backed up file %s, split file, sequence %d" or
+# "DOS 2.0 backed up file %s, complete file"
+>>>>>>0        ubyte   x       DOS 2.0-3.2 backed up
+#>>>>>>0       ubyte   0xff    complete
+>>>>>>0        ubyte   0
+>>>>>>>1 uleshort      x       sequence %d of
+# full file name with path but without drive letter and colon stored from 0x05 til 0x52
+>>>>>>0x5      string  x       file %s
+# backup name is original filename
+#!:ext *
+# magic/Magdir/msdos, 1169: Warning: EXTENSION type `     *' has bad char '*'
+# file: line 1169: Bad magic entry '  *'
+# after header original file content
+>>>>>>128      indirect x      \b; 
 
 
 # DOS backup 3.3 to 5.x