-.\" $File: magic.man,v 1.36 2007/01/10 22:56:49 christos Exp $
+.\" $File: magic.man,v 1.37 2007/01/12 17:38:27 christos Exp $
.Dd January 10, 2007
.Dt MAGIC __FSECTION__
.Os
A string of bytes.
The string type specification can be optionally followed
by /[Bbc]*.
-The
+The
.Dq B
flag compacts whitespace in the target, which must
contain at least one whitespace character.
consecutive blanks, the target needs at least
.Dv n
consecutive blanks to match.
-The
+The
.Dq b
flag treats every blank in the target as an optional blank.
Finally the
characters in the target.
.It Dv pstring
A pascal style string where the first byte is interpreted as the an
-unsigned length. The string is not NUL terminated.
+unsigned length.
+The string is not NUL terminated.
.It Dv date
A four-byte value interpreted as a UNIX date.
.It Dv qdate
A regular expression match in extended POSIX regular expression syntax
(much like egrep).
The type specification can be optionally followed by /[cse]*.
-The
+The
.Dq c
flag makes the match case insensitive, while the
.Dq s
will match the beginning and end of individual lines, respectively,
not beginning and end of file.
.It Dv search
-A literal string search starting at the given offset. It must be followed by
-.Dv /<number>
+A literal string search starting at the given offset.
+It must be followed by
+.Dv \*[Lt]number\*[Gt]
which specifies how many matches shall be attempted (the range).
This is suitable for searching larger binary expressions with variable
offsets, using
.Dv \e
escapes for special characters.
-.It Dv default
+.It Dv default
This is intended to be used with the text
.Dv x
(which is always true) and a message that is to be used if there are
.El
.Pp
The numeric types may optionally be followed by
-.Dv &
+.Dv \*[Am]
and a numeric value,
to specify that the value is to be AND'ed with the
numeric value before any comparisons are done.
It may be
.Dv = ,
to specify that the value from the file must equal the specified value,
-.Dv < ,
+.Dv \*[Lt] ,
to specify that the value from the file must be less than the specified
value,
-.Dv > ,
+.Dv \*[Gt] ,
to specify that the value from the file must be greater than the specified
value,
-.Dv & ,
+.Dv \*[Am] ,
to specify that the value from the file must have set all of the bits
that are set in the specified value,
.Dv ^ ,
For all tests except
.Em string
and
-.Em regex,
+.Em regex ,
operation
.Dv !
specifies that the line matches if the test does
file must match the specified byte string.
The operators
.Dv = ,
-.Dv <
+.Dv \*[Lt]
and
-.Dv >
+.Dv \*[Gt]
(but not
-.Dv & )
+.Dv \*[Am] )
can be applied to strings.
The length used for matching is that of the string argument
in the magic file.
This means that a line can match any string, and
then presumably print that string, by doing
-.Em >\e0
+.Em \*[Gt]\e0
(because all strings are greater than the null string).
.Pp
The special test
.Em x
always evaluates to true.
.Dv message
-The message to be printed if the comparison succeeds. If the string
-contains a
+The message to be printed if the comparison succeeds.
+If the string contains a
.Xr printf 3
format specification, the value from the file (with any specified masking
performed) is printed using the message as the format string.
along with the file type or need additional tests to determine the true
file type.
These additional tests are introduced by one or more
-.Em >
+.Em \*[Gt]
characters preceding the offset.
The number of
-.Em >
+.Em \*[Gt]
on the line indicates the level of the test; a line with no
-.Em >
+.Em \*[Gt]
at the beginning is considered to be at level 0.
Tests are arranged in a tree-like hierarchy:
If a the test on a line at level
(or less) appears.
For more complex files, one can use empty messages to get just the
"if/then" effect, in the following way:
-.Bd -literal -offset indent
+.Bd -literal -offset indent
0 string MZ
->0x18 leshort <0x40 MS-DOS executable
->0x18 leshort >0x3f extended PC executable (e.g., MS Windows)
+\*[Gt]0x18 leshort \*[Lt]0x40 MS-DOS executable
+\*[Gt]0x18 leshort \*[Gt]0x3f extended PC executable (e.g., MS Windows)
.Ed
.Pp
Offsets do not need to be constant, but can also be read from the file
being examined.
If the first character following the last
-.Em >
+.Em \*[Gt]
is a
.Em (
then the string after the parenthesis is interpreted as an indirect offset.
The value at that offset is read, and is used again as an offset
in the file.
Indirect offsets are of the form:
-.Em (( x [.[bslBSL]][+\-][ y ]).
+.Em (( x [.[bslBSL]][+\-][ y ]) .
The value of
.Em x
-is used as an offset in the file. A byte, short or long is read at that offset
-depending on the
+is used as an offset in the file.
+A byte, short or long is read at that offset depending on the
.Em [bslBSLm]
type specifier.
The capitalized types interpret the number as a big endian
The default type if one is not specified is long.
.Pp
That way variable length structures can be examined:
-.Bd -literal -offset indent
+.Bd -literal -offset indent
# MS Windows executables are also valid MS-DOS executables
0 string MZ
->0x18 leshort <0x40 MZ executable (MS-DOS)
+\*[Gt]0x18 leshort \*[Lt]0x40 MZ executable (MS-DOS)
# skip the whole block below if it is not an extended executable
->0x18 leshort >0x3f
->>(0x3c.l) string PE\e0\e0 PE executable (MS-Windows)
->>(0x3c.l) string LX\e0\e0 LX executable (OS/2)
+\*[Gt]0x18 leshort \*[Gt]0x3f
+\*[Gt]\*[Gt](0x3c.l) string PE\e0\e0 PE executable (MS-Windows)
+\*[Gt]\*[Gt](0x3c.l) string LX\e0\e0 LX executable (OS/2)
.Ed
.Pp
This strategy of examining has one drawback: You must make sure that
.Pp
If this indirect offset cannot be used as-is, there are simple calculations
possible: appending
-.Em [+-*/%&|^]<number>
+.Em [+-*/%\*[Am]|^]\*[Lt]number\*[Gt]
inside parentheses allows one to modify
the value read from the file before it is used as an offset:
-.Bd -literal -offset indent
+.Bd -literal -offset indent
# MS Windows executables are also valid MS-DOS executables
0 string MZ
# sometimes, the value at 0x18 is less that 0x40 but there's still an
# extended executable, simply appended to the file
->0x18 leshort <0x40
->>(4.s*512) leshort 0x014c COFF executable (MS-DOS, DJGPP)
->>(4.s*512) leshort !0x014c MZ executable (MS-DOS)
+\*[Gt]0x18 leshort \*[Lt]0x40
+\*[Gt]\*[Gt](4.s*512) leshort 0x014c COFF executable (MS-DOS, DJGPP)
+\*[Gt]\*[Gt](4.s*512) leshort !0x014c MZ executable (MS-DOS)
.Ed
.Pp
Sometimes you do not know the exact offset as this depends on the length or
-position (when indirection was used before) of preceding fields. You can
-specify an offset relative to the end of the last up-level field using
-.Sq &
+position (when indirection was used before) of preceding fields.
+You can specify an offset relative to the end of the last up-level
+field using
+.Sq \*[Am]
as a prefix to the offset:
-.Bd -literal -offset indent
+.Bd -literal -offset indent
0 string MZ
->0x18 leshort >0x3f
->>(0x3c.l) string PE\e0\e0 PE executable (MS-Windows)
+\*[Gt]0x18 leshort \*[Gt]0x3f
+\*[Gt]\*[Gt](0x3c.l) string PE\e0\e0 PE executable (MS-Windows)
# immediately following the PE signature is the CPU type
->>>&0 leshort 0x14c for Intel 80386
->>>&0 leshort 0x184 for DEC Alpha
+\*[Gt]\*[Gt]\*[Gt]\*[Am]0 leshort 0x14c for Intel 80386
+\*[Gt]\*[Gt]\*[Gt]\*[Am]0 leshort 0x184 for DEC Alpha
.Ed
.Pp
Indirect and relative offsets can be combined:
-.Bd -literal -offset indent
+.Bd -literal -offset indent
0 string MZ
->0x18 leshort <0x40
->>(4.s*512) leshort !0x014c MZ executable (MS-DOS)
+\*[Gt]0x18 leshort \*[Lt]0x40
+\*[Gt]\*[Gt](4.s*512) leshort !0x014c MZ executable (MS-DOS)
# if it's not COFF, go back 512 bytes and add the offset taken
# from byte 2/3, which is yet another way of finding the start
# of the extended executable
->>>&(2.s-514) string LE LE executable (MS Windows VxD driver)
+\*[Gt]\*[Gt]\*[Gt]\*[Am](2.s-514) string LE LE executable (MS Windows VxD driver)
.Ed
.Pp
Or the other way around:
-.Bd -literal -offset indent
+.Bd -literal -offset indent
0 string MZ
->0x18 leshort >0x3f
->>(0x3c.l) string LE\e0\e0 LE executable (MS-Windows)
+\*[Gt]0x18 leshort \*[Gt]0x3f
+\*[Gt]\*[Gt](0x3c.l) string LE\e0\e0 LE executable (MS-Windows)
# at offset 0x80 (-4, since relative offsets start at the end
# of the up-level match) inside the LE header, we find the absolute
# offset to the code area, where we look for a specific signature
->>>(&0x7c.l+0x26) string UPX \eb, UPX compressed
+\*[Gt]\*[Gt]\*[Gt](\*[Am]0x7c.l+0x26) string UPX \eb, UPX compressed
.Ed
.Pp
Or even both!
-.Bd -literal -offset indent
+.Bd -literal -offset indent
0 string MZ
->0x18 leshort >0x3f
->>(0x3c.l) string LE\e0\e0 LE executable (MS-Windows)
+\*[Gt]0x18 leshort \*[Gt]0x3f
+\*[Gt]\*[Gt](0x3c.l) string LE\e0\e0 LE executable (MS-Windows)
# at offset 0x58 inside the LE header, we find the relative offset
# to a data area where we look for a specific signature
->>>&(&0x54.l-3) string UNACE \eb, ACE self-extracting archive
+\*[Gt]\*[Gt]\*[Gt]\*[Am](\*[Am]0x54.l-3) string UNACE \eb, ACE self-extracting archive
.Ed
.Pp
Finally, if you have to deal with offset/length pairs in your file, even the
second value in a parenthesized expression can be taken from the file itself,
-using another set of parentheses. Note that this additional indirect offset
-is always relative to the start of the main indirect offset.
-.Bd -literal -offset indent
+using another set of parentheses.
+Note that this additional indirect offset is always relative to the
+start of the main indirect offset.
+.Bd -literal -offset indent
0 string MZ
->0x18 leshort >0x3f
->>(0x3c.l) string PE\e0\e0 PE executable (MS-Windows)
+\*[Gt]0x18 leshort \*[Gt]0x3f
+\*[Gt]\*[Gt](0x3c.l) string PE\e0\e0 PE executable (MS-Windows)
# search for the PE section called ".idata"...
->>>&0xf4 search/0x140 .idata
+\*[Gt]\*[Gt]\*[Gt]\*[Am]0xf4 search/0x140 .idata
# ...and go to the end of it, calculated from start+length;
# these are located 14 and 10 bytes after the section name
->>>>(&0xe.l+(-4)) string PK\e3\e4 \eb, ZIP self-extracting archive
+\*[Gt]\*[Gt]\*[Gt]\*[Gt](\*[Am]0xe.l+(-4)) string PK\e3\e4 \eb, ZIP self-extracting archive
.Ed
+.Sh SEE ALSO
+.Xr file __CSECTION__
+\- the command that reads this file.
.Sh BUGS
The formats
.Dv long ,
of bytes (2B, 4B, etc),
since the files being recognized typically come from
a system on which the lengths are invariant.
-.Sh SEE ALSO
-.Xr file __CSECTION__
-\- the command that reads this file.
.\"
.\" From: guy@sun.uucp (Guy Harris)
.\" Newsgroups: net.bugs.usg
.\" the changes I posted to the S5R2 version.
.\"
.\" Modified for Ian Darwin's version of the file command.
-.\" @(#)$Id: magic.man,v 1.37 2007/01/12 17:38:27 christos Exp $
+.\" @(#)$Id: magic.man,v 1.38 2007/01/27 00:52:08 ljt Exp $
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