Password Formats

Notes about the password encryption formats generated and understood by Apache.

Basic Authentication

There are five formats that Apache recognizes for basic-authentication passwords. Note that not all formats work on every platform:

bcrypt

"$2y$" + the result of the crypt_blowfish algorithm. See the APR source file crypt_blowfish.c for the details of the algorithm.

MD5

"$apr1$" + the result of an Apache-specific algorithm using an iterated (1,000 times) MD5 digest of various combinations of a random 32-bit salt and the password. See the APR source file apr_md5.c for the details of the algorithm.

SHA1

"{SHA}" + Base64-encoded SHA-1 digest of the password. Insecure.

CRYPT

Unix only. Uses the traditional Unix crypt(3) function with a randomly-generated 32-bit salt (only 12 bits used) and the first 8 characters of the password. Insecure.

PLAIN TEXT (i.e. unencrypted)

Windows & Netware only. Insecure.

Generating values with htpasswd

$ htpasswd -nbB myName myPassword
myName:$2y$05$c4WoMPo3SXsafkva.HHa6uXQZWr7oboPiC2bT/r7q1BB8I2s0BRqC

$ htpasswd -nbm myName myPassword
myName:$apr1$r31.....$HqJZimcKQFAMYayBlzkrA/

$ htpasswd -nbs myName myPassword
myName:{SHA}VBPuJHI7uixaa6LQGWx4s+5GKNE=

$ htpasswd -nbd myName myPassword
myName:rqXexS6ZhobKA

Generating CRYPT and MD5 values with the OpenSSL command-line program

OpenSSL knows the Apache-specific MD5 algorithm.

$ openssl passwd -apr1 myPassword
$apr1$qHDFfhPC$nITSVHgYbDAK1Y0acGRnY0

openssl passwd -crypt myPassword
qQ5vTYO3c8dsU

Validating CRYPT or MD5 passwords with the OpenSSL command line program

The salt for a CRYPT password is the first two characters (converted to a binary value). To validate myPassword against rqXexS6ZhobKA

$ openssl passwd -crypt -salt rq myPassword
Warning: truncating password to 8 characters
rqXexS6ZhobKA

Note that using myPasswo instead of myPassword will produce the same result because only the first 8 characters of CRYPT passwords are considered.

The salt for an MD5 password is between $apr1$ and the following $ (as a Base64-encoded binary value - max 8 chars). To validate myPassword against $apr1$r31.....$HqJZimcKQFAMYayBlzkrA/

$ openssl passwd -apr1 -salt r31..... myPassword
$apr1$r31.....$HqJZimcKQFAMYayBlzkrA/

Database password fields for mod_dbd

The SHA1 variant is probably the most useful format for DBD authentication. Since the SHA1 and Base64 functions are commonly available, other software can populate a database with encrypted passwords that are usable by Apache basic authentication.

To create Apache SHA1-variant basic-authentication passwords in various languages:

'{SHA}' . base64_encode(sha1($password, TRUE))

"{SHA}" + new sun.misc.BASE64Encoder().encode(java.security.MessageDigest.getInstance("SHA1").digest(password.getBytes()))

"{SHA}" & ToBase64(BinaryDecode(Hash(password, "SHA1"), "Hex"))

require 'digest/sha1'
require 'base64'
'{SHA}' + Base64.encode64(Digest::SHA1.digest(password))

Use the APR function: apr_sha1_base64

import base64
import hashlib
"{SHA}" + format(base64.b64encode(hashlib.sha1(password).digest()))

Digest Authentication

Apache recognizes one format for digest-authentication passwords - the MD5 hash of the string user:realm:password as a 32-character string of hexadecimal digits. realm is the Authorization Realm argument to the AuthName directive in httpd.conf.

Database password fields for mod_dbd

Since the MD5 function is commonly available, other software can populate a database with encrypted passwords that are usable by Apache digest authentication.

To create Apache digest-authentication passwords in various languages:

md5($user . ':' . $realm . ':' .$password)

byte b[] = java.security.MessageDigest.getInstance("MD5").digest( (user + ":" + realm + ":" + password ).getBytes());
java.math.BigInteger bi = new java.math.BigInteger(1, b);
String s = bi.toString(16);
while (s.length() < 32)
 s = "0" + s;  // String s is the encrypted password

LCase(Hash( (user & ":" & realm & ":" & password) , "MD5"))

require 'digest/md5'
Digest::MD5.hexdigest(user + ':' + realm + ':' + password)

encode(digest( user || ':' || realm || ':' || password , 'md5'), 'hex')