Provided by: apache2-utils_2.4.62-3ubuntu1_amd64 
NAME
htdbm - Manipulate DBM password databases
SYNOPSIS
htdbm [ -TDBTYPE ] [ -i ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [ -v ]
filename username
htdbm -b [ -TDBTYPE ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [ -v ] filename
username password
htdbm -n [ -i ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [ -v ] username
htdbm -nb [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [ -v ] username password
htdbm -v [ -TDBTYPE ] [ -i ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [ -v ]
filename username
htdbm -vb [ -TDBTYPE ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [ -v ]
filename username password
htdbm -x [ -TDBTYPE ] filename username
htdbm -l [ -TDBTYPE ]
SUMMARY
htdbm is used to manipulate the DBM format files used to store usernames and password for
basic authentication of HTTP users via mod_authn_dbm. See the dbmmanage documentation for
more information about these DBM files.
OPTIONS
-b Use batch mode; i.e., get the password from the command line rather than prompting
for it. This option should be used with extreme care, since the password is clearly
visible on the command line. For script use see the -i option.
-i Read the password from stdin without verification (for script usage).
-c Create the passwdfile. If passwdfile already exists, it is rewritten and truncated.
This option cannot be combined with the -n option.
-n Display the results on standard output rather than updating a database. This option
changes the syntax of the command line, since the passwdfile argument (usually the
first one) is omitted. It cannot be combined with the -c option.
-m Use MD5 hashing for passwords. On Windows and Netware, this is the default.
-B Use bcrypt hashing for passwords. This is currently considered to be very secure.
-C This flag is only allowed in combination with -B (bcrypt hashing). It sets the
computing time used for the bcrypt algorithm (higher is more secure but slower,
default: 5, valid: 4 to 31).
-d Use crypt() hashing for passwords. The default on all platforms but Windows and
Netware. Though possibly supported by htdbm on all platforms, it is not supported
by the httpd server on Windows and Netware. This algorithm is insecure by today's
standards.
-s Use SHA hashing for passwords. Facilitates migration from/to Netscape servers using
the LDAP Directory Interchange Format (ldif). This algorithm is insecure by today's
standards.
-p Use plaintext passwords. Though htdbm will support creation on all platforms, the
httpd daemon will only accept plain text passwords on Windows and Netware.
-l Print each of the usernames and comments from the database on stdout.
-v Verify the username and password. The program will print a message indicating
whether the supplied password is valid. If the password is invalid, the program
exits with error code 3.
-x Delete user. If the username exists in the specified DBM file, it will be deleted.
-t Interpret the final parameter as a comment. When this option is specified, an
additional string can be appended to the command line; this string will be stored
in the "Comment" field of the database, associated with the specified username.
filename
The filename of the DBM format file. Usually without the extension .db, .pag, or
.dir. If -c is given, the DBM file is created if it does not already exist, or
updated if it does exist.
username
The username to create or update in passwdfile. If username does not exist in this
file, an entry is added. If it does exist, the password is changed.
password
The plaintext password to be hashed and stored in the DBM file. Used only with the
-b flag.
-TDBTYPE
Type of DBM file (SDBM, GDBM, DB, or "default").
BUGS
One should be aware that there are a number of different DBM file formats in existence,
and with all likelihood, libraries for more than one format may exist on your system. The
three primary examples are SDBM, NDBM, GNU GDBM, and Berkeley/Sleepycat DB 2/3/4.
Unfortunately, all these libraries use different file formats, and you must make sure that
the file format used by filename is the same format that htdbm expects to see. htdbm
currently has no way of determining what type of DBM file it is looking at. If used
against the wrong format, will simply return nothing, or may create a different DBM file
with a different name, or at worst, it may corrupt the DBM file if you were attempting to
write to it.
One can usually use the file program supplied with most Unix systems to see what format a
DBM file is in.
EXIT STATUS
htdbm returns a zero status ("true") if the username and password have been successfully
added or updated in the DBM File. htdbm returns 1 if it encounters some problem accessing
files, 2 if there was a syntax problem with the command line, 3 if the password was
entered interactively and the verification entry didn't match, 4 if its operation was
interrupted, 5 if a value is too long (username, filename, password, or final computed
record), 6 if the username contains illegal characters (see the Restrictions section), and
7 if the file is not a valid DBM password file.
EXAMPLES
htdbm /usr/local/etc/apache/.htdbm-users jsmith
Adds or modifies the password for user jsmith. The user is prompted for the password. If
executed on a Windows system, the password will be hashed using the modified Apache MD5
algorithm; otherwise, the system's crypt() routine will be used. If the file does not
exist, htdbm will do nothing except return an error.
htdbm -c /home/doe/public_html/.htdbm jane
Creates a new file and stores a record in it for user jane. The user is prompted for the
password. If the file exists and cannot be read, or cannot be written, it is not altered
and htdbm will display a message and return an error status.
htdbm -mb /usr/web/.htdbm-all jones Pwd4Steve
Encrypts the password from the command line (Pwd4Steve) using the MD5 algorithm, and
stores it in the specified file.
SECURITY CONSIDERATIONS
Web password files such as those managed by htdbm should not be within the Web server's
URI space -- that is, they should not be fetchable with a browser.
The use of the -b option is discouraged, since when it is used the plaintext password
appears on the command line.
When using the crypt() algorithm, note that only the first 8 characters of the password
are used to form the password. If the supplied password is longer, the extra characters
will be silently discarded.
The SHA hashing option does not use salting: for a given password, there is only one
hashed representation. The crypt() and MD5 formats permute the representation by
prepending a random salt string, to make dictionary attacks against the passwords more
difficult.
The SHA and crypt() formats are insecure by today's standards.
RESTRICTIONS
On the Windows platform, passwords hashed with htdbm are limited to no more than 255
characters in length. Longer passwords will be truncated to 255 characters.
The MD5 algorithm used by htdbm is specific to the Apache software; passwords hashed using
it will not be usable with other Web servers.
Usernames are limited to 255 bytes and may not include the character :.