`passlib.utils.binary` - Binary Helper Functions¶

Warning

This module is primarily used as an internal support module. Its interface has not been finalized yet, and may be changed somewhat between major releases of Passlib, as the internal code is cleaned up and simplified.

Constants¶

passlib.utils.binary.BASE64_CHARS¶: Character map used by standard MIME-compatible Base64 encoding scheme.

passlib.utils.binary.HASH64_CHARS¶

Base64 character map used by a number of hash formats; the ordering is wildly different from the standard base64 character map.

This encoding system appears to have originated with des_crypt, but is used by md5_crypt, sha256_crypt, and others. Within Passlib, this encoding is referred as the “hash64” encoding, to distinguish it from normal base64 and others.

passlib.utils.binary.BCRYPT_CHARS¶: Base64 character map used by bcrypt. The ordering is wildly different from both the standard base64 character map, and the common hash64 character map.

Base64 Encoding¶

Base64Engine Class¶

Passlib has to deal with a number of different Base64 encodings, with varying endianness, as well as wildly different character <-> value mappings. This is all encapsulated in the Base64Engine class, which provides common encoding actions for an arbitrary base64-style encoding scheme. There are also a couple of predefined instances which are commonly used by the hashes in Passlib.

class passlib.utils.binary.Base64Engine(charmap, big=False)¶

Provides routines for encoding/decoding base64 data using arbitrary character mappings, selectable endianness, etc.

Parameters:	charmap – A string of 64 unique characters, which will be used to encode successive 6-bit chunks of data. A character’s position within the string should correspond to its 6-bit value. big – Whether the encoding should be big-endian (default False).

Note

This class does not currently handle base64’s padding characters in any way what so ever.

Raw Bytes <-> Encoded Bytes¶

The following methods convert between raw bytes, and strings encoded using the engine’s specific base64 variant:

encode_bytes(source)¶

encode bytes to base64 string.

Parameters:	source – byte string to encode.
Returns:	byte string containing encoded data.

decode_bytes(source)¶

decode bytes from base64 string.

Parameters:	source – byte string to decode.
Returns:	byte string containing decoded data.

encode_transposed_bytes(source, offsets)¶: encode byte string, first transposing source using offset list

decode_transposed_bytes(source, offsets)¶: decode byte string, then reverse transposition described by offset list

Integers <-> Encoded Bytes¶

The following methods allow encoding and decoding unsigned integers to and from the engine’s specific base64 variant. Endianess is determined by the engine’s big constructor keyword.

encode_int6(value)¶: encodes 6-bit integer -> single hash64 character

decode_int6(source)¶: decode single character -> 6 bit integer

encode_int12(value)¶: encodes 12-bit integer -> 2 char string

decode_int12(source)¶: decodes 2 char string -> 12-bit integer

encode_int24(value)¶: encodes 24-bit integer -> 4 char string

decode_int24(source)¶: decodes 4 char string -> 24-bit integer

encode_int64(value)¶

encode 64-bit integer -> 11 char hash64 string

this format is used primarily by des-crypt & variants to encode the DES output value used as a checksum.

decode_int64(source)¶

decode 11 char base64 string -> 64-bit integer

this format is used primarily by des-crypt & variants to encode the DES output value used as a checksum.

Informational Attributes¶

charmap¶: unicode string containing list of characters used in encoding; position in string matches 6bit value of character.

bytemap¶: bytes version of charmap

big¶: boolean flag indicating this using big-endian encoding.

Predefined Instances¶

passlib.utils.binary.h64¶: Predefined instance of Base64Engine which uses the HASH64_CHARS character map and little-endian encoding. (see HASH64_CHARS for more details).

passlib.utils.binary.h64big¶: Predefined variant of h64 which uses big-endian encoding. This is mainly used by des_crypt.

Changed in version 1.6: Previous versions of Passlib contained a module named passlib.utils.h64; As of Passlib 1.6 this was replaced by the the h64 and h64big instances of the Base64Engine class; the interface remains mostly unchanged.

Other¶

passlib.utils.binary.ab64_encode(data)¶

encode using shortened base64 format which omits padding & whitespace. uses custom ./ altchars.

it is primarily used by Passlib’s custom pbkdf2 hashes.

passlib.utils.binary.ab64_decode(data)¶

decode from shortened base64 format which omits padding & whitespace. uses custom ./ altchars, but supports decoding normal +/ altchars as well.