* New Validation API
Some guidelines in designing the new validation API
* Previously, the `Valid` method was placed on the claim, which was always not entirely semantically correct, since the validity is concerning the token, not the claims. Although the validity of the token is based on the processing of the claims (such as `exp`). Therefore, the function `Valid` was removed from the `Claims` interface and the single canonical way to retrieve the validity of the token is to retrieve the `Valid` property of the `Token` struct.
* The previous fact was enhanced by the fact that most claims implementations had additional exported `VerifyXXX` functions, which are now removed
* All validation errors should be comparable with `errors.Is` to determine, why a particular validation has failed
* Developers want to adjust validation options. Popular options include:
* Leeway when processing exp, nbf, iat
* Not verifying `iat`, since this is actually just an informational claim. When purely looking at the standard, this should probably the default
* Verifying `aud` by default, which actually the standard sort of demands. We need to see how strong we want to enforce this
* Developers want to create their own claim types, mostly by embedding one of the existing types such as `RegisteredClaims`.
* Sometimes there is the need to further tweak the validation of a token by checking the value of a custom claim. Previously, this was possibly by overriding `Valid`. However, this was error-prone, e.g., if the original `Valid` was not called. Therefore, we should provide an easy way for *additional* checks, without by-passing the necessary validations
This leads to the following two major changes:
* The `Claims` interface now represents a set of functions that return the mandatory claims represented in a token, rather than just a `Valid` function. This is also more semantically correct.
* All validation tasks are offloaded to a new (optional) `validator`, which can also be configured with appropriate options. If no custom validator was supplied, a default one is used.
Co-authored-by: Micah Parks <66095735+MicahParks@users.noreply.github.com>
By default base64 decoder works in non-strict mode which
allows tweaking signatures having padding without failing validation.
This creates a potential problem if application treats token value as an identifier.
For example ES256 signature has length of 64 bytes and two padding symbols (stripped by default).
Therefore its base64-encoded value can only end with A, Q, g and w.
In non-strict mode last symbol could be tweaked resulting in 16 distinct
token values having the same signature and passing validation.
This change adds backward-compatible global config variable DecodeStrict
(similar to existing DecodePaddingAllowed) that enables strict base64 decoder mode.
See also https://github.com/golang/go/issues/15656.
Signed-off-by: Alexander Yastrebov <yastrebov.alex@gmail.com>
* improve code comments, including security consideration
* Add link to URL with details about security vulnerabilities.
* Update token.go
Co-authored-by: Christian Banse <oxisto@aybaze.com>
* Update token.go
Co-authored-by: Christian Banse <oxisto@aybaze.com>
* update code comments
Co-authored-by: Christian Banse <oxisto@aybaze.com>
Christian Banse