NAME
hfind - Lookup a hash value in a hash database
SYNOPSIS
hfind [-i db_type ] [-f lookup_file ] [-eq] db_file [hashes]
DESCRIPTION
hfind looks up hash values in a database using a binary search
algorithm. This allows one to easily create a hash database and
identify if a file is known or not. It works with the NIST National
Software Reference Library (NSRL) and the output of ’md5sum’.
Before the database can be used by ’hfind’, an index file must be
created with the ’-i’ option.
This tool is needed for efficiency. Most text-based databases do not
have fixed length entries and are sometimes not sorted. The hfind tool
will create an index file that is sorted and has fixed-length entries.
This allows for fast lookups using a binary search algorithm instead of
a linear search such as ’grep’.
ARGUMENTS
-i db_type
Create an index file for the database. This step must be done
before a lookup can be performed. The ’db_type’ argument
specifies the database type (i.e. nsrl-md5 or md5sum). See
section below.
-f lookup_file
Specify the location of a file that contains one hash value per
line. These hashes will be looked up in the database.
-e Extended mode. Additional information besides just the name is
printed. (Does not apply for all hash database types).
-q Quick mode. Instead of displaying the corresponding information
with the hash, just display 0 if the hash was not found and 1 if
it was. If this flag is used, then only one hash can be given
at a time.
-V Display version
db_file
The location of the hash database file.
[hashes]
The hashes to lookup. If they are not supplied on the command
line, STDIN is used. If index files exist for both SHA-1 and
MD5 hashes, then both types of hashes can be given at runtime.
INDEX FILE
hfind uses an index file to perform a binary search for a hash value.
This is much faster than using ’grep’, which will do a linear search.
Before a hash database is used, a corresponding index file must be
created. This is done with the ’-i’ option to hfind.
The resulting index file will be named based on the database file name.
The name will have the original name following by the hash type (sha1
or md5) followed by ’.idx’. For example, creating an MD5 hash index of
the NIST NSRL results in ’NSRLFile.txt-md5.idx’ and the SHA-1 index
results in ’NSRLFile.txt-sha1.idx’.
The file has two columns. Each entry is sorted by the first column,
which is the hash value. The second column has the byte offset of the
corresponding entry in the original file. So, when a hash is found in
the index, the offset is recorded and then ’hfind’ seeks to the entry
in the original database.
The following input types are valid. For NSRL, ’nsrl-md5’ and ´nsrl-
sha1’ can be used. The difference is which hash value the index is
sorted by. The ’md5sum’ value can also be used to sort and index "home
made" databases. ’hfind’ can take data in both common formats:
MD5 (test.txt) = 76b1f4de1522c20b67acc132937cf82e
and
76b1f4de1522c20b67acc132937cf82e test.txt
EXAMPLES
To create an MD5 index file for NIST NSRL:
# hfind -i nsrl-md5 /usr/local/hash/nsrl/NSRLFile.txt
To lookup a value in the NSRL:
# hfind /usr/local/hash/nsrl/NSRLFile.txt
76b1f4de1522c20b67acc132937cf82e
76b1f4de1522c20b67acc132937cf82e Hash Not Found
You can even do both SHA-1 and MD5 if you want:
# hfind -i nsrl-sha1 /usr/local/hash/nsrl/NSRLFile.txt
# hfind /usr/local/hash/nsrl/NSRLFile.txt
76b1f4de1522c20b67acc132937cf82e
80001A80B3F1B80076B297CEE8805AAA04E1B5BA
76b1f4de1522c20b67acc132937cf82e Hash Not Found
80001A80B3F1B80076B297CEE8805AAA04E1B5BA thrdcore.cpp
To make a database of critical binaries of a trusted system, use
’md5sum’:
# md5sum /bin/* /sbin/* /usr/bin/* /usr/bin/* /usr/local/bin/*
/usr/local/sbin/* > system.md5
# hfind -i md5sum system.md5
To look entries up, the following will work:
# hfind system.md5 76b1f4de1522c20b67acc132937cf82e
76b1f4de1522c20b67acc132937cf82e Hash Not Found
or
# md5sum -q /bin/* | hfind system.md5
928682269cd3edb1acdf9a7f7e606ff2 /bin/bash
<...>
or
# md5sum -q /bin/* > bin.md5
# hfind -f bin.md5 system.md5
928682269cd3edb1acdf9a7f7e606ff2 /bin/bash
<...>
SEE ALSO
sorter(1)
The NIST National Software Reference Library (NSRL) can be found at
www.nsrl.nist.gov.
LICENSE
Distributed under the Common Public License, found in the cpl1.0.txt
file in the The Sleuth Kit licenses directory.
AUTHOR
Brian Carrier <carrier at sleuthkit dot org>
Send documentation updates to <doc-updates at sleuthkit dot org>