passlib.hash.django_digest - Django-specific Hashes

The Django web framework provides a module for storing user accounts and passwords (django.contrib.auth). This module’s password hashing code supports a few simple salted digests, stored using the format id$salt$checksum (where id is an identifier assigned by Django). Passlib provides support for all the hashes used up to and including Django 1.4

See also

• passlib.apps.django_context - a set of premade contexts which mimic Django’s builtin hashing policy, and can read all of the formats listed below.

Django 1.4 Hashes

Django 1.4 introduced a new “hashers” framework, as well as three new modern large-salt variable-cost hash algorithms:

• django_pbkdf2_sha256 - a PBKDF2-HMAC-SHA256 based hash.
• django_pbkdf2_sha1 - a PBKDF2-HMAC-SHA1 based hash.
• django_bcrypt - a wrapper around bcrypt.

These classes can be used directly as follows:

>>> from passlib.hash import django_pbkdf2_sha256 as handler

>>> # encrypt password
>>> h = handler.encrypt("password")
>>> h
'pbkdf2_sha256$10000$s1w0UXDd00XB$+4ORmyvVWAQvoAEWlDgN34vlaJx1ZTZpa1pCSRey2Yk='

>>> # verify password
>>> handler.verify("password", h)
True
>>> handler.verify("eville", h)
False

See also

the generic PasswordHash usage examples

Interface

class passlib.hash.django_pbkdf2_sha256

This class implements Django’s PBKDF2-HMAC-SHA256 hash, and follows the Password Hash Interface.

It supports a variable-length salt, and a variable number of rounds.

The encrypt() and genconfig() methods accept the following optional keywords:

Parameters:

• salt (str) – Optional salt string. If not specified, a 12 character one will be autogenerated (this is recommended). If specified, may be any series of characters drawn from the regexp range [0-9a-zA-Z].
• salt_size (int) – Optional number of characters to use when autogenerating new salts. Defaults to 12, but can be any positive value.
• rounds (int) – Optional number of rounds to use. Defaults to 10000, but must be within range(1,1<<32).
• relaxed (bool) – By default, providing an invalid value for one of the other keywords will result in a ValueError. If relaxed=True, and the error can be corrected, a PasslibHashWarning will be issued instead. Correctable errors include rounds that are too small or too large, and salt strings that are too long.

This should be compatible with the hashes generated by Django 1.4’s PBKDF2PasswordHasher class.

New in version 1.6.

class passlib.hash.django_pbkdf2_sha1

This class implements Django’s PBKDF2-HMAC-SHA1 hash, and follows the Password Hash Interface.

It supports a variable-length salt, and a variable number of rounds.

The encrypt() and genconfig() methods accept the following optional keywords:

Parameters:

• salt (str) – Optional salt string. If not specified, a 12 character one will be autogenerated (this is recommended). If specified, may be any series of characters drawn from the regexp range [0-9a-zA-Z].
• salt_size (int) – Optional number of characters to use when autogenerating new salts. Defaults to 12, but can be any positive value.
• rounds (int) – Optional number of rounds to use. Defaults to 10000, but must be within range(1,1<<32).
• relaxed (bool) – By default, providing an invalid value for one of the other keywords will result in a ValueError. If relaxed=True, and the error can be corrected, a PasslibHashWarning will be issued instead. Correctable errors include rounds that are too small or too large, and salt strings that are too long.

This should be compatible with the hashes generated by Django 1.4’s PBKDF2SHA1PasswordHasher class.

New in version 1.6.

passlib.hash.django_bcrypt

This class implements Django 1.4’s BCrypt wrapper, and follows the Password Hash Interface.

This is identical to bcrypt itself, but with the Django-specific prefix "bcrypt$" prepended. See passlib.hash.bcrypt - BCrypt for more details, the usage and behavior is identical.

This should be compatible with the hashes generated by Django 1.4’s BCryptPasswordHasher class.

New in version 1.6.

Format

An example django_pbkdf2_sha256 hash (of password) is:

pbkdf2_sha256$10000$s1w0UXDd00XB$+4ORmyvVWAQvoAEWlDgN34vlaJx1ZTZpa1pCSRey2Yk=

Both of Django’s PBKDF2 hashes have the same basic format, ident$rounds$salt$checksum, where:

• ident is an identifier (pbkdf2_sha256 in the case of the example).
• rounds is a variable cost parameter encoded in decimal.
• salt consists of (usually 12) alphanumeric digits (s1w0UXDd00XB in the example).
• checksum is the base64 encoding the PBKDF2 digest.

The digest porition is generated by passing the utf-8 encoded password, the ascii-encoded salt string, and the number of rounds into PBKDF2 using the HMAC-SHA256 prf; and generated a 32 byte checksum, which is then encoding using base64.

The other PBKDF2 wrapper functions similarly.

Django 1.0 Hashes

Warning

All of the following hashes are very susceptible to brute-force attacks; since they are simple single-round salted digests. They should not be used for any purpose besides manipulating existing Django password hashes.

Django 1.0 supports some basic salted digests, as well as some legacy hashes:

• django_salted_sha1 - simple salted SHA1 digest, Django 1.0-1.3’s default.
• django_salted_md5 - simple salted MD5 digest.
• django_des_crypt - support for legacy des_crypt hashes, shoehorned into Django’s hash format.

These classes can be used directly as follows:

>>> from passlib.hash import django_salted_sha1 as handler

>>> # encrypt password
>>> h = handler.encrypt("password")
>>> h
'sha1$c6218$161d1ac8ab38979c5a31cbaba4a67378e7e60845'

>>> # verify password
>>> handler.verify("password", h)
True
>>> handler.verify("eville", h)
False

See also

the generic PasswordHash usage examples

Interface

class passlib.hash.django_salted_md5

This class implements Django’s Salted MD5 hash, and follows the Password Hash Interface.

It supports a variable-length salt, and uses a single round of MD5.

The encrypt() and genconfig() methods accept the following optional keywords:

Parameters:

• salt (str) – Optional salt string. If not specified, a 12 character one will be autogenerated (this is recommended). If specified, may be any series of characters drawn from the regexp range [0-9a-zA-Z].
• salt_size (int) – Optional number of characters to use when autogenerating new salts. Defaults to 12, but can be any positive value.

This should be compatible with the hashes generated by Django 1.4’s MD5PasswordHasher class.

class passlib.hash.django_salted_sha1

This class implements Django’s Salted SHA1 hash, and follows the Password Hash Interface.

It supports a variable-length salt, and uses a single round of SHA1.

The encrypt() and genconfig() methods accept the following optional keywords:

Parameters:

• salt (str) – Optional salt string. If not specified, a 12 character one will be autogenerated (this is recommended). If specified, may be any series of characters drawn from the regexp range [0-9a-zA-Z].
• salt_size (int) – Optional number of characters to use when autogenerating new salts. Defaults to 12, but can be any positive value.

This should be compatible with Django 1.4’s SHA1PasswordHasher class.

Format

An example django_salted_sha1 hash (of password) is:

sha1$f8793$c4cd18eb02375a037885706d414d68d521ca18c7

Both of Django’s salted hashes have the same basic format, ident$salt$checksum, where:

• ident is an identifier (sha1 in the case of the example, md5 for django_salted_md5).
• salt consists of (usually 5) lowercase hexidecimal digits (f8793 in the example).
• checksum is lowercase hexidecimal encoding of the checksum.

The checksum is generated by concatenating the salt digits followed by the password, and hashing them using the specified digest (MD5 or SHA-1). The digest is then encoded to hexidecimal. If the password is unicode, it is converted to utf-8 first.

Security Issues

Django’s salted hashes should not be considered very secure.

• They use only a single round of digests with known collision and pre-image attacks (SHA1 & MD5).
• While it could be increased, they currently use only 20 bits of entropy in their salt, which is borderline insufficient to defeat rainbow tables.
• They digest the encoded hexidecimal salt, not the raw bytes, increasing the odds that a particular salt+password string will be present in a pre-computed tables of ascii digests.

Des Crypt Wrapper

class passlib.hash.django_des_crypt

This class implements Django’s des_crypt wrapper, and follows the Password Hash Interface.

It supports a fixed-length salt.

The encrypt() and genconfig() methods accept the following optional keywords:

Parameters:salt (str) – Optional salt string. If not specified, one will be autogenerated (this is recommended). If specified, it must be 2 characters, drawn from the regexp range [./0-9A-Za-z].

This should be compatible with the hashes generated by Django 1.4’s CryptPasswordHasher class. Note that Django only supports this hash on Unix systems (though django_des_crypt is available cross-platform under Passlib).

Changed in version 1.6: This class will now accept hashes with empty salt strings, since Django 1.4 generates them this way.

Format

An example django_des_crypt hash (of password) is crypt$cd1a4$cdlRbNJGImptk; the general format is the same as the salted hashes: ident$salt$checksum, where:

• ident is the identifier crypt.
• salt is 5 lowercase hexidecimal digits (cd1a4 in the example).
• checksum is a des_crypt hash (cdlRbNJGImptk in the example).

It should be noted that this class essentially just shoe-horns des_crypt into a format compatible with the Django salted hashes (above). It has a few quirks, such as the fact that only the first two characters of the salt are used by des_crypt, and they are in turn duplicated as the first two characters of the checksum.

For security issues relating to django_des_crypt, see des_crypt.

Other Hashes

class passlib.hash.django_disabled

This class provides disabled password behavior for Django, and follows the Password Hash Interface.

This class does not implement a hash, but instead claims the special hash string "!" which Django uses to indicate an account’s password has been disabled.

• newly encrypted passwords will hash to !.
• it rejects all passwords.

Note

Some older (pre-1.0) versions of Django encoded passwords using hex_md5, though this has been deprecated by Django, and should become increasingly rare.