htpasswd - Manage user files for basic authentication

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htpasswd is used to create and update the flat-files used to store usernames and password for basic authentication of HTTP users. If htpasswd cannot access a file, such as not being able to write to the output file or not being able to read the file in order to update it, it returns an error status and makes no changes.

Resources available from the Apache HTTP server can be restricted to just the users listed in the files created by htpasswd. This program can only manage usernames and passwords stored in a flat-file. It can hash and display password information for use in other types of data stores, though. To use a DBM database see dbmmanage or htdbm.

htpasswd hashes passwords using either bcrypt, a version of MD5 modified for Apache, SHA-1, or the system's crypt() routine. SHA-2-based hashes (SHA-256 and SHA-512) are supported for crypt(). Files managed by htpasswd may contain a mixture of different encoding types of passwords; some user records may have bcrypt or MD5-hashed passwords while others in the same file may have passwords hashed with crypt().

This manual page only lists the command line arguments. For details of the directives necessary to configure user authentication in httpd see the Apache manual, which is part of the Apache distribution or can be found at http://httpd.apache.org/.

Synopsis
Options
Exit Status
Examples
Security Considerations
Restrictions

Synopsis ¶

htpasswd [ -c ] [ -i ] [ -m | -B | -2 | -5 | -d | -s | -p ] [ -r rounds ] [ -C cost ] [ -D ] [ -v ] passwdfile username

htpasswd -b [ -c ] [ -m | -B | -2 | -5 | -d | -s | -p ] [ -r rounds ] [ -C cost ] [ -D ] [ -v ] passwdfile username password

htpasswd -n [ -i ] [ -m | -B | -2 | -5 | -d | -s | -p ] [ -r rounds ] [ -C cost ] username

htpasswd -nb [ -m | -B | -2 | -5 | -d | -s | -p ] [ -r rounds ] [ -C cost ] username password

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.
Available in 2.4.4 and later.
-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 file. This is useful for generating password records acceptable to Apache for inclusion in non-text data stores. 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. This is the default (since version 2.2.18).
-2: Use SHA-256 crypt() based hashes for passwords. This is supported on most Unix platforms.
-5: Use SHA-512 crypt() based hashes for passwords. This is supported on most Unix platforms.
-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 17).
-r: This flag is only allowed in combination with -2 or -5. It sets the number of hash rounds used for the SHA-2 algorithms (higher is more secure but slower; the default is 5,000).
-d: Use crypt() hashing for passwords. This is not supported by the httpd server on Windows and Netware. This algorithm limits the password length to 8 characters. This algorithm is insecure by today's standards. It used to be the default algorithm until version 2.2.17.
-s: Use SHA-1 (160-bit) 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 htpasswd will support creation on all platforms, the httpd daemon will only accept plain text passwords on Windows and Netware.
-D: Delete user. If the username exists in the specified htpasswd file, it will be deleted.
-v: Verify password. Verify that the given password matches the password of the user stored in the specified htpasswd file.
Available in 2.4.5 and later.
passwdfile: Name of the file to contain the user name and password. If -c is given, this file is created if it does not already exist, or rewritten and truncated 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 file. Only used with the -b flag.

Exit Status ¶

htpasswd returns a zero status ("true") if the username and password have been successfully added or updated in the passwdfile. htpasswd 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 password file.

Examples ¶

htpasswd /usr/local/etc/apache/.htpasswd-users jsmith

Adds or modifies the password for user jsmith. The user is prompted for the password. The password will be hashed using the modified Apache MD5 algorithm. If the file does not exist, htpasswd will do nothing except return an error.

htpasswd -c /home/doe/public_html/.htpasswd 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 htpasswd will display a message and return an error status.

htpasswd -db /usr/web/.htpasswd-all jones Pwd4Steve

Encrypts the password from the command line (Pwd4Steve) using the crypt() algorithm, and stores it in the specified file.

Security Considerations ¶

Web password files such as those managed by htpasswd should not be within the Web server's URI space -- that is, they should not be fetchable with a browser.

This program is not safe as a setuid executable. Do not make it setuid.

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-1 hashing format 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-1 and crypt() formats are insecure by today's standards.

The SHA-2-based crypt() formats (SHA-256 and SHA-512) are supported on most modern Unix systems, and follow the specification at https://www.akkadia.org/drepper/SHA-crypt.txt.

Restrictions ¶

On the Windows platform, passwords hashed with htpasswd are limited to no more than 255 characters in length. Longer passwords will be truncated to 255 characters.

The MD5 algorithm used by htpasswd 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 :.

The cost of computing a bcrypt password hash value increases with the number of rounds specified by the -C option. The apr-util library enforces a maximum number of rounds of 17 in version 1.6.0 and later.