fix(backend): validate JWT issuer (iss) claim when an issuer option is provided#8772
fix(backend): validate JWT issuer (iss) claim when an issuer option is provided#8772jacekradko wants to merge 1 commit into
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📝 WalkthroughWalkthroughThis PR adds opt-in issuer claim validation to JWT verification in the Clerk backend. ChangesJWT Issuer Validation
Estimated code review effort🎯 2 (Simple) | ⏱️ ~12 minutes Poem
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API Changes Report
Summary
@clerk/backendCurrent version: 3.5.0 Subpath
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Actionable comments posted: 2
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Inline comments:
In `@packages/backend/src/jwt/__tests__/assertions.test.ts`:
- Around line 237-242: Update the tests in
packages/backend/src/jwt/__tests__/assertions.test.ts to stop treating an
explicitly configured-but-empty issuer as "opt-in": change the expectation for
assertIssuerClaim(iss, '') to expect it to throw (i.e., configured-empty should
fail), and add a new predicate-edge-case test that calls assertIssuerClaim with
a non-string or missing iss (e.g., an object with iss:number or undefined)
alongside a predicate function to verify it fails in a controlled way; reference
the assertIssuerClaim function and adjust the related assertions in both the
block around the current opt-in test and the second block noted (lines ~254-267)
to cover these failure paths.
In `@packages/backend/src/jwt/assertions.ts`:
- Around line 99-115: assertIssuerClaim currently treats an empty-string issuer
as "not configured" and calls predicate resolvers with iss cast to string, which
can skip validation or throw non-TokenVerificationError exceptions; change the
guard to check for issuer === undefined (so empty string is treated as
configured) and ensure the predicate is only invoked when typeof iss ===
'string' (otherwise throw TokenVerificationError with
TokenVerificationErrorAction.EnsureClerkJWT and
TokenVerificationErrorReason.TokenInvalidIssuer); update the isValid computation
in assertIssuerClaim to perform the typeof iss === 'string' check before calling
a function issuer(iss) and produce the stable token-invalid-issuer error when
iss is missing or malformed.
🪄 Autofix (Beta)
Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
- Create a new PR with the fixes
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📒 Files selected for processing (7)
.changeset/backend-issuer-validation.mdpackages/backend/src/errors.tspackages/backend/src/jwt/__tests__/assertions.test.tspackages/backend/src/jwt/__tests__/verifyJwt.test.tspackages/backend/src/jwt/assertions.tspackages/backend/src/jwt/verifyJwt.tspackages/backend/src/tokens/__tests__/verify.test.ts
| it('does not throw if no issuer is provided (opt-in)', () => { | ||
| expect(() => assertIssuerClaim(iss)).not.toThrow(); | ||
| expect(() => assertIssuerClaim(iss, undefined)).not.toThrow(); | ||
| expect(() => assertIssuerClaim(undefined)).not.toThrow(); | ||
| expect(() => assertIssuerClaim(iss, '')).not.toThrow(); | ||
| }); |
There was a problem hiding this comment.
Adjust issuer tests to avoid codifying validation bypass and cover predicate edge-case errors.
The current case at Line 241 (issuer: '') asserts skip behavior even though issuer is supplied. Add/adjust tests so configured-but-empty issuer fails, and include a predicate case with non-string/missing iss to verify controlled failure behavior.
Suggested test updates
it('does not throw if no issuer is provided (opt-in)', () => {
expect(() => assertIssuerClaim(iss)).not.toThrow();
expect(() => assertIssuerClaim(iss, undefined)).not.toThrow();
expect(() => assertIssuerClaim(undefined)).not.toThrow();
- expect(() => assertIssuerClaim(iss, '')).not.toThrow();
+ expect(() => assertIssuerClaim(iss, '')).toThrow(`Invalid JWT issuer claim (iss) "https://clerk.example.com".`);
});
@@
it('throws if iss is missing or not a string when an issuer string is required', () => {
expect(() => assertIssuerClaim(undefined, iss)).toThrow(`Invalid JWT issuer claim (iss) undefined.`);
expect(() => assertIssuerClaim(42, iss)).toThrow(`Invalid JWT issuer claim (iss) 42.`);
});
+
+ it('throws if iss is missing when issuer resolver is a predicate', () => {
+ expect(() => assertIssuerClaim(undefined, i => i.startsWith('https://clerk.'))).toThrow(
+ `Invalid JWT issuer claim (iss) undefined.`,
+ );
+ });As per coding guidelines, **/*.{test,spec}.{ts,tsx} should verify proper error handling and edge cases for new functionality.
Also applies to: 254-267
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/__tests__/assertions.test.ts` around lines 237 -
242, Update the tests in packages/backend/src/jwt/__tests__/assertions.test.ts
to stop treating an explicitly configured-but-empty issuer as "opt-in": change
the expectation for assertIssuerClaim(iss, '') to expect it to throw (i.e.,
configured-empty should fail), and add a new predicate-edge-case test that calls
assertIssuerClaim with a non-string or missing iss (e.g., an object with
iss:number or undefined) alongside a predicate function to verify it fails in a
controlled way; reference the assertIssuerClaim function and adjust the related
assertions in both the block around the current opt-in test and the second block
noted (lines ~254-267) to cover these failure paths.
Source: Coding guidelines
| export const assertIssuerClaim = (iss: unknown, issuer?: IssuerResolver) => { | ||
| // No issuer configured, skip validation. Preserves the default behavior, matching how | ||
| // the audience and authorized parties claims are only checked when an option is provided. | ||
| if (!issuer) { | ||
| return; | ||
| } | ||
|
|
||
| const isValid = typeof issuer === 'function' ? issuer(iss as string) : typeof iss === 'string' && iss === issuer; | ||
|
|
||
| if (!isValid) { | ||
| throw new TokenVerificationError({ | ||
| action: TokenVerificationErrorAction.EnsureClerkJWT, | ||
| reason: TokenVerificationErrorReason.TokenInvalidIssuer, | ||
| message: `Invalid JWT issuer claim (iss) ${JSON.stringify(iss)}.`, | ||
| }); | ||
| } | ||
| }; |
There was a problem hiding this comment.
Fail closed for configured issuer and guard predicate execution.
Line 102 currently treats issuer: '' as “not configured”, which silently skips validation. Line 106 also calls predicate resolvers with iss as string, so malformed tokens can surface non-TokenVerificationError exceptions instead of a stable token-invalid-issuer failure.
Suggested fix
-export const assertIssuerClaim = (iss: unknown, issuer?: IssuerResolver) => {
+export const assertIssuerClaim = (iss: unknown, issuer?: IssuerResolver): void => {
// No issuer configured, skip validation. Preserves the default behavior, matching how
// the audience and authorized parties claims are only checked when an option is provided.
- if (!issuer) {
+ if (typeof issuer === 'undefined') {
return;
}
- const isValid = typeof issuer === 'function' ? issuer(iss as string) : typeof iss === 'string' && iss === issuer;
+ const issValue = typeof iss === 'string' ? iss : undefined;
+ let isValid = false;
+
+ if (typeof issuer === 'function') {
+ try {
+ isValid = typeof issValue === 'string' && issuer(issValue);
+ } catch {
+ isValid = false;
+ }
+ } else {
+ isValid = typeof issValue === 'string' && issValue === issuer;
+ }
if (!isValid) {
throw new TokenVerificationError({
action: TokenVerificationErrorAction.EnsureClerkJWT,
reason: TokenVerificationErrorReason.TokenInvalidIssuer,
message: `Invalid JWT issuer claim (iss) ${JSON.stringify(iss)}.`,
});
}
};🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@packages/backend/src/jwt/assertions.ts` around lines 99 - 115,
assertIssuerClaim currently treats an empty-string issuer as "not configured"
and calls predicate resolvers with iss cast to string, which can skip validation
or throw non-TokenVerificationError exceptions; change the guard to check for
issuer === undefined (so empty string is treated as configured) and ensure the
predicate is only invoked when typeof iss === 'string' (otherwise throw
TokenVerificationError with TokenVerificationErrorAction.EnsureClerkJWT and
TokenVerificationErrorReason.TokenInvalidIssuer); update the isValid computation
in assertIssuerClaim to perform the typeof iss === 'string' check before calling
a function issuer(iss) and produce the stable token-invalid-issuer error when
iss is missing or malformed.
1 participant
verifyJwtnever actually validated theissclaim.VerifyJwtOptionshad noissuerfield, theIssuerResolvertype injwt/assertions.tswas unused, and eleven tests inverifyJwt.test.tspassed anissuer:that nothing read, so they passed regardless. This wires it up.assertIssuerClaimis the actual change, and it skips when no issuer is configured:Nobody passes
issuertoday (including the networklessjwtKeypath and the machine/OAuth verifiers that shareverifyJwt), so current behavior doesn't change, andverifyToken/authenticateRequestpick the option up through the existing options composition. The eleven inert tests now exercise the assertion, and I added the negatives that were missing: a mismatched string, a rejecting predicate, and averifyToken({ issuer })case to confirm the option reaches the public API. This does not turn issuer validation on by default inauthenticateRequest; that's a separate change.Summary by CodeRabbit
New Features
issueroption. Provide a string for exact-match validation or a function for custom validation logic. When omitted, issuer validation is skipped entirely.Bug Fixes
issueroption is provided, rather than ignoring it.