tyk [TT-12495] Add support for RSASSA-PSS signed JWTs

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Adding support for the more secure RSA-PSS signed JWTS.

Description

allows for the use of the RSA-PSS signature algorithm commonly referred to as PS256, PS384, PS512. The change is invisible to existing RSA Public Keyuse cases. Simply - by using "RSA Public Key" signing algorithm, Tyk will now validate JWTs signed by both RS & PS Class algorithms using Public Keys.

Motivation and Context

RSA-PSS is considered more secure than PKCS1 v1.5 due to its probabilistic nature, which helps mitigate certain attacks (e.g., padding oracle attacks).

RS256: Commonly used in legacy systems, JWT (JSON Web Tokens), and many existing protocols where backward compatibility is important. PS256: Recommended for new applications where higher security is desired. It is becoming more widely adopted in modern security protocols.

How This Has Been Tested

Unit tests have been added. Both positive + negative tests that test both RS class JWTs and PS class JWTs.

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[ ] Refactoring or add test (improvements in base code or adds test coverage to functionality)

Checklist

[ ] I ensured that the documentation is up to date
[ ] I explained why this PR updates go.mod in detail with reasoning why it's required
[ ] I would like a code coverage CI quality gate exception and have explained why

Jun 24 '24 16:06 sedkis

PR Reviewer Guide 🔍

⏱️ Estimated effort to review [1-5]	3
🧪 Relevant tests	Yes
🔒 Security concerns	No
⚡ Key issues to review	Error Handling Consistency: The error message in `mw_jwt.go` for the RSAPSS check could be more consistent with other error messages in the same function. Consider using a similar format for clarity and uniformity.

Jun 24 '24 16:06 github-actions[bot]

API Changes

no api changes detected

Jun 24 '24 16:06 github-actions[bot]

PR Code Suggestions ✨

Category	Suggestion	Score
Possible bug	Add nil check for token.Header to prevent runtime errors To avoid potential nil pointer dereference, add a nil check for `token.Header` before accessing its "alg" key in the error message formatting. gateway/mw_jwt.go [845] `+if token.Header == nil { + return fmt.Errorf("token header is nil") +} return fmt.Errorf("%v: %v and not RSA or RSAPSS signature", UnexpectedSigningMethod, token.Header["alg"])` Suggestion importance[1-10]: 9 Why: Adding a nil check for `token.Header` prevents potential runtime errors, which is crucial for code reliability and stability.	9
Maintainability	Consolidate conditional checks into a single statement for clarity To improve the readability and maintainability of the JWT signing method assertion, consider consolidating the checks for `jwt.SigningMethodRSA` and `jwt.SigningMethodRSAPSS` into a single conditional statement using logical OR. gateway/mw_jwt.go [843-845] `-if _, ok := token.Method.(jwt.SigningMethodRSA); !ok { - if _, ok := token.Method.(jwt.SigningMethodRSAPSS); !ok { - return fmt.Errorf("%v: %v and not RSA or RSAPSS signature", UnexpectedSigningMethod, token.Header["alg"]) - } +if _, ok := token.Method.(jwt.SigningMethodRSA); !ok && _, ok := token.Method.(jwt.SigningMethodRSAPSS); !ok { + return fmt.Errorf("%v: %v and not RSA or RSAPSS signature", UnexpectedSigningMethod, token.Header["alg"]) }` Suggestion importance[1-10]: 8 Why: Consolidating the checks into a single conditional statement improves code readability and maintainability without altering functionality.	8
Enhancement	Add a test case for RSAPSS signing method To improve the test coverage and ensure the RSAPSS signing method is correctly handled, add a specific test case for RSAPSS similar to the existing RS256 test. gateway/mw_jwt_test.go [1628-1657] `-func TestAssertRS256JWT(t testing.T) { +func TestAssertRSAPSSJWT(t testing.T) { ... }` Suggestion importance[1-10]: 8 Why: Adding a specific test case for RSAPSS improves test coverage and ensures that the RSAPSS signing method is correctly handled.	8
Enhancement	Add assertions to check JWT contents in tests To ensure the robustness of the JWT parsing tests, add assertions to verify the contents of the parsed JWT, such as checking the claims or the header, instead of only checking for errors. gateway/mw_jwt_test.go [1614-1625] `-_, err := parser.Parse(rawJWT, func(token jwt.Token) (interface{}, error) { +token, err := parser.Parse(rawJWT, func(token jwt.Token) (interface{}, error) { if err := assertSigningMethod(signingMethod, token); err != nil { return nil, err } return parseJWTKey(signingMethod, pubKey) }) if err != nil { t.Error("Could not validate RS256 key") } +assert.Equal(t, "John Doe", token.Claims.(jwt.MapClaims)["name"])` Suggestion importance[1-10]: 7 Why: Adding assertions to verify the contents of the parsed JWT enhances test robustness and ensures the JWT is parsed correctly.	7