Data.ByteString.Base64.URL

This module contains ByteString-valued combinators for implementing the RFC 4648 specification of the Base64url encoding format. This includes strictly padded/unpadded and lenient decoding variants, as well as internal and external validation for canonicity.

Encoding

encodeBase64 :: ByteString -> Text

Encode a ByteString value as a Base64url Text value with padding.

See: RFC-4648 section 5

Examples:

>>> encodeBase64 "<<?>>"
"PDw_Pj4="

encodeBase64' :: ByteString -> ByteString

Encode a ByteString as a Base64url ByteString value with padding.

See: RFC-4648 section 5

Examples:

>>> encodeBase64' "<<?>>"
"PDw_Pj4="

encodeBase64Unpadded :: ByteString -> Text

Encode a ByteString value as Base64url Text without padding. Note that for Base64url, padding is optional. If you call this function, you will simply be encoding as Base64url and stripping padding chars from the output.

See: RFC-4648 section 3.2

Examples:

>>> encodeBase64Unpadded "<<?>>"
"PDw_Pj4"

encodeBase64Unpadded' :: ByteString -> ByteString

Encode a ByteString value as Base64url without padding. Note that for Base64url, padding is optional. If you call this function, you will simply be encoding as Base64url and stripping padding chars from the output.

See: RFC-4648 section 3.2

Examples:

>>> encodeBase64Unpadded' "<<?>>"
"PDw_Pj4"

Decoding

decodeBase64 :: ByteString -> Either Text ByteString

Decode a padded Base64url encoded ByteString value. If its length is not a multiple of 4, then padding chars will be added to fill out the input to a multiple of 4 for safe decoding as Base64url-encoded values are optionally padded.

For a decoder that fails on unpadded input of incorrect size, use decodeBase64Unpadded.

See: RFC-4648 section 4

Examples:

>>> decodeBase64 "PDw_Pj4="
Right "<<?>>"

>>> decodeBase64 "PDw_Pj4"
Right "<<?>>"

>>> decodeBase64 "PDw-Pg="
Left "Base64-encoded bytestring has invalid padding"

>>> decodeBase64 "PDw-Pg"
Right "<<>>"

decodeBase64Unpadded :: ByteString -> Either Text ByteString

Decode an unpadded Base64url-encoded ByteString value. Input strings are required to be unpadded, and will undergo validation prior to decoding to confirm.

In general, unless unpadded Base64url is explicitly required, it is safer to call decodeBase64.

See: RFC-4648 section 4

Examples:

>>> decodeBase64Unpadded "PDw_Pj4"
Right "<<?>>"

>>> decodeBase64Unpadded "PDw_Pj4="
Left "Base64-encoded bytestring has invalid padding"

decodeBase64Padded :: ByteString -> Either Text ByteString

Decode a padded Base64url-encoded ByteString value. Input strings are required to be correctly padded, and will be validated prior to decoding to confirm.

In general, unless padded Base64url is explicitly required, it is safer to call decodeBase64.

See: RFC-4648 section 4

Examples:

>>> decodeBase64Padded "PDw_Pj4="
Right "<<?>>"

>>> decodeBase64Padded "PDw_Pj4"
Left "Base64-encoded bytestring requires padding"

decodeBase64Lenient :: ByteString -> ByteString

Leniently decode an unpadded Base64url-encoded ByteString. This function will not generate parse errors. If input data contains padding chars, then the input will be parsed up until the first pad character.

Note: This is not RFC 4648-compliant.

Examples:

>>> decodeBase64Lenient "PDw_Pj4="
"<<?>>"

>>> decodeBase64Lenient "PDw_%%%$}Pj4"
"<<?>>"

Validation

isBase64Url :: ByteString -> Bool

Tell whether a ByteString is encoded in padded or unpadded Base64url format.

This function will also detect non-canonical encodings such as ZE==, which are externally valid Base64url-encoded values, but are internally inconsistent "impossible" values.

Examples:

>>> isBase64Url "PDw_Pj4="
True

>>> isBase64Url "PDw_Pj4"
True

>>> isBase64Url "PDw_Pj"
False

isValidBase64Url :: ByteString -> Bool

Tell whether a ByteString is a valid Base64url format.

This will not tell you whether or not this is a correct Base64url representation, only that it conforms to the correct shape. To check whether it is a true Base64 encoded ByteString value, use isBase64Url.

Examples:

>>> isValidBase64Url "PDw_Pj4="
True

>>> isValidBase64Url "PDw_Pj"
True

>>> isValidBase64Url "%"
False