HTDBM(1) htdbm HTDBM(1)
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 encryption for passwords. On Windows and Netware, this is the default.
-B Use bcrypt encryption for passwords. This is currently considered to be very secure.
-C This flag is only allowed in combination with -B (bcrypt encryption). It sets the computing time used
for the bcrypt algorithm (higher is more secure but slower, default: 5, valid: 4 to 31).
-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, asso‐
ciated 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 encrypted 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 likeli‐
hood, 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 cor‐
rupt 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 encrypted using the modified Apache MD5 algorithm; otherwise, the system's
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 speci‐
fied 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 unencrypted 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 encryption format does not use salting: for a given password, there is only one encrypted representa‐
tion. The crypt() and MD5 formats permute the representation by prepending a random salt string, to make dic‐
tionary attacks against the passwords more difficult.
The SHA and crypt() formats are insecure by today's standards.
RESTRICTIONS
On the Windows platform, passwords encrypted 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 encrypted using it will not be
usable with other Web servers.
Usernames are limited to 255 bytes and may not include the character :.
Apache HTTP Server 2012-12-12 HTDBM(1)
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