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TRIPWIRE

NAME

SYNOPSIS

DESCRIPTION

Tripwire is a file integrity checker - a utility that compares a designated set of files and directories against information stored in a previously generated database. Added or deleted files are flagged and reported, as are any files that have changed from their previously recorded state in the database. When run against system files on a regular basis, any file changes would be spotted when Tripwire is next run, giving system administrators information to enact damage control measures immediately.

Using Tripwire, system administrators can conclude with an extremely high degree of certainty that a given set of files and directories remain untouched from unauthorized modifications, provided the program and database are appropriately protected (e.g., stored on read-only media). Note that reports of changed files indicate a change from the time of the last Tripwire database installation or update. For best effect, the files being monitored should be reinstalled from known good sources. (See the Tripwire design document for further details.)

Tripwire uses message-digest algorithms (one-way hash functions) to detect changes in a hard-to-spoof manner. This should be able to detect significant changes to critical files, including those caused by insertion of backdoors or viruses. Tripwire also monitors changes to file permissions, modification times, and other significant changes to inodes as selected by the system administrator on a per-file/directory basis.

Tripwire runs in one of four modes: Database Generation, Database Update, Integrity Checking, or Interactive Update mode. In Database Generation mode, Tripwire initializes the database based upon the entries enumerated in the tw.config file. Database Update mode provides incremental database update functionality on a per-file/directory basis. This obviates having to regenerate the entire database every time a file or set of files change. The Integrity Checking mode generates a report of added, deleted, or changed files, comparing all the files described by the tw.config file against the files residing on the filesystem. Lastly, the Interactive Update mode reports added, deleted, and changed files and prompts the user whether those database entries should be updated.

The Interactive Update mode provides a simple and thorough method for system administrators to keep Tripwire databases ``in sync'' with filesystems that change.  

OPTIONS

When run without any arguments, tripwire runs in Integrity Checking mode.

-initialize

Database Generation mode. Creates the database which is used for all subsequent Integrity Checking runs.

-update pathname/entry ...

Database Update mode. This mode updates the specified pathname or entry in the database. If the argument provided is a file, only that file is updated. If the argument is a directory, that directory and all of its children are updated. If the argument is an entry in the tw.config file, the entire entry in the database is updated.

-interactive

Interactive Integrity Checking. Tripwire first reports all added, deleted, and changed files, then prompting the user whether the entry should be updated in the database.

Note that Tripwire opens up /dev/tty instead of using stdin. This prevents automating interactive updates, reducing the chance of system administrators inadvertently updating entries. Updating the database should always be done with care and deliberation.

-loosedir

Loosens checking rules for directories in Integrity Checking modes so changes in size, nlink, modification and creation times no longer are reported. This significantly quiets Tripwire reports, at the possible risk of missing important changes.

-d dbasefile

Reads the database information from the specified file dbasefile. stdin can specified by ``-d -''.

-c configfile

Read the configuration information from the specified file configfile. stdin can specified by ``-c -''.

-cfd openfd

Read the configuration information from the open file descriptor openfd. This option allows programs outside of Tripwire to supply services such as networking, compression, and encryption.

-dfd openfd

Read the database file from the open file descriptor openfd. This option allows programs outside of Tripwire to supply services such as networking, compression, and encryption.

-Dvar=value

Defines the tw.config variable var to value. (As if @@define were used.)

-Uvar

Undefine the tw.config variable var. (As if @@undef were used.)

-i [#|all]

Ignore the specified signature, and skip it when comparing against database entries. If all is specified, no signatures are collected or compared.

-E

Prints out preprocessed tw.config file to stdout.

-preprocess

Same as -E option.

-q

Quiet mode. In this mode, Tripwire prints only one line reports for each added, changed, or deleted file. Phase 5 is skipped, which prints all the pairs of expected and observed file attribute values.

-v

Verbose mode. Prints out filenames as they are being scanned during signature computation.

-help

Print out inode interpretation message (for parsing messages when files have changed).

-version

Prints out version information.

DATABASE GENERATION MODE

In Database Generation mode, tripwire creates the database file based upon the entries in tw.config. The name of this database file is defined at compile-time in config.h - it defaults to tw.db_[hostname]. The generated database is placed in the ./databases directory, and must be moved to the target directory manually.

Note that you must manually move this file to your database directory. This is because the default database directory should be a read-only file system.  

DATABASE UPDATE MODE

In Database Update mode, tripwire updates the specified files, directories, or entries in the database. The old database is saved in the ./databases directory with the .old suffix. The new, updated database is also written to the ./databases directory. As in the Database Generation mode, the new database must be manually moved to the Tripwire database directory.

tripwire in Database Update mode requires at least one argument, which is used as an entry. The entry argument specifies which file or directory is to be updated, and is interpreted similar to tw.config entries. If the argument is a filename, only that file is updated in the database. Similarly, if the argument is a directory name, the directory and its children are updated. If the argument is also an entry in the tw.config file, the entire entry is updated.

Database updates yield a new database file with added, deleted, or changed entries. This functionality is provided to allow Tripwire databases to be updated in a controlled manner to reflect filesystem changes, obviating the need to regenerate the entire database again.  

INTEGRITY CHECKING MODE

In Integrity Checking mode, tripwire reads in the tw.config file, and rebuilds a new database to reflect the current files. Tripwire then compares the new database with the existing Tripwire database stored on the filesystem, reporting added or deleted files, as well as those files that have changed.

The tw.config file, in addition to the list of files and directories, also lists which attributes can change and be safely ignored by Tripwire. Tripwire applies these select-flags to decide which changes can be safely unreported.

Each file that differs from the information stored in the database is considered ``changed.'' However, only the changes that remain after the select-flags are applied are displayed. For each change, the expected and actual information is printed. For instance:

2:30am (mentor) 985 % tripwire
### Phase 1:   Reading configuration file
### Phase 2:   Generating file list
### Phase 3:   Creating file information database
### Phase 4:   Searching for inconsistencies
###
###                     Total files scanned:            82
###                           Files added:              0
###                           Files deleted:            0
###                           Files changed:            80
###
###                     After applying rules:
###                           Changes discarded:        79
###                           Changes remaining:        1
###
changed: -rw------- genek        4433 Oct 13 02:30:34 1992 /tmp/genek/tripwire-0.92/config.h
### Phase 5:   Generating observed/expected pairs for changed files
###
### Attr        Observed (what it is)         Expected (what it should be)
### =========== ============================= =============================
/tmp/genek/tripwire-0.92/config.h
       st_size: 4441                          4433
    md5 (sig1): 0aqL1O06C3Fj1YBXz3.CPdcb      0cPX1H.DYS.s1vZdKD.ELMDR
 snefru (sig2): 0PcgcK/MZvEm.8pIWe.Gbnn/      /8VoJv1JcoUA0NvoGN.k3P6E
  crc32 (sig3): .EHA6x                        /OuGNV
  crc16 (sig4): ...9/q                        ...6yu
    md4 (sig5): /hQ0sU.UEbJo.UR4VZ/mNG/h      .UR4VZ/mNG/h/VSG/W/Z643k
    md2 (sig6): .hLwjb.VRA0O.Z72y90xTYqA      1LR0Gg1l.vqB0.1g330Pi8/p

Tripwire in Interactive Update mode will look similar. However, for each added, deleted, or changed file, the user is prompted whether the entry corresponding to the file or directory should be updated. The user can answer with either ``y'', ``n'', ``Y'', or ``N''. The first two answers are simply ``yes, update the specified file'' and ``no, don't update the file'' respectively.

Answering ``Y'' not only updates the specified file or directory, but all other files or directories that share the same entry in the tw.config file. For example, if ``Y'' were answered for /etc, then all the files generated by the /etc entry will also be updated. Answering ``N'' is similar, but skips all files and directories corresponding to the specified entry.

A possible Tripwire session running in Interactive Update mode may look like:

3:34pm (flounder) tw/src 5 %%% tripwire -interactive
### Phase 1:   Reading configuration file
### Phase 2:   Generating file list
### Phase 3:   Creating file information database
### Phase 4:   Searching for inconsistencies
###
###                     Total files scanned:            49
###                           Files added:              0
###                           Files deleted:            0
###                           Files changed:            49
###
###                     After applying rules:
###                           Changes discarded:        48
###                           Changes remaining:        1
###
changed: -rw------- genek        7893 May  5 15:30:37 1993 /homes/genek/research/tw/src/databases/tw.db_flounder.Eng.Sun.COM.old
### Phase 5:   Generating observed/expected pairs for changed files
###
### Attr        Observed (what it is)         Expected (what it should be)
### =========== ============================= =============================
/homes/genek/research/tw/src/databases/tw.db_flounder.Eng.Sun.COM.old
      st_mtime: Wed May  5 15:30:37 1993      Wed May  5 15:24:09 1993
      st_ctime: Wed May  5 15:30:37 1993      Wed May  5 15:24:09 1993
---> File: '/homes/genek/research/tw/src/databases/tw.db_flounder.Eng.Sun.COM.old'
---> Update entry?  [YN(y)nh?] y

### Updating database...
###
### Phase 1:   Reading configuration file
### Phase 2:   Generating file list
### Phase 3:   Updating file information database
### Phase 3:   Updating file information database
###
### Old database file will be moved to `tw.db_barnum.cs.purdue.edu.old'
###            in ./databases.
###
### Updated database will be stored in './databases/tw.db_barnum.cs.purdue.edu'
###            (Tripwire expects it to be moved to '/tmp/genek'.)
###
3:34pm (flounder) tw/src 6 %%% 

DIAGNOSTICS

ENVIRONMENT

BUGS

SEE ALSO

The Design and Implementation of Tripwire: A UNIX File Integrity Checker by Gene Kim and Eugene Spafford. Purdue Technical Report CSD-TR-93-071.  

AUTHORS

Gene Kim
Purdue University
gkim@cs.purdue.edu

Eugene Spafford
Purdue University
spaf@cs.purdue.edu

Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

DATABASE GENERATION MODE

DATABASE UPDATE MODE

INTEGRITY CHECKING MODE

DIAGNOSTICS

ENVIRONMENT

BUGS

SEE ALSO

AUTHORS