failed to parse token
Nobody has claimed this yet.
Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 45/100
- Issue type
- Bug
- Clarity
- Needs clarification
- Activity status
- Active
- Tech stack
- go
- Domain
- authentication
Research direction
Start at s.iasMiddleware.ParseAndValidateJWT and follow the listed validator.go, token.go, and openid/token_gen.go trace; inspect how the email claim is decoded when IAS mappings contain Corporate and Identity values. Clarify the intended supported claim shape and verify the behavior with a regression case for the reported token; done when the failure is handled according to that decision.
Written by the indexing model from the issue text.
Description
We are using IAS JWT validation to verify that our JWTs are valid.
We have seen that many customers receive an error like this:
{"error":"failed to parse token: failed to decode value for key email: error reading next value: json: cannot unmarshal array into Go value of type
string","file":"server.go:1008","func":"main.(*Server).handleLoginFormAuthentication","level":"warning","msg":"IAS JWT cannot be parsed","time":"2026-08-25T23:44:17.923Z"}
I looked at the IAS attribute mapping, and it seems that the customers added two fields to the mapping: Corporate and Identity values.
For example:
This is the trace:
s.iasMiddleware.ParseAndValidateJWT(iasJwtToken)
↓
vendor/cloud-security-client-go/auth/validator.go:22
NewToken(rawToken)
↓
vendor/cloud-security-client-go/auth/token.go:40
jwt.ParseString(encodedToken, jwt.WithToken(openid.New()))
↓
vendor/lestrrat-go/jwx/jwt/jwt.go:463
json.Unmarshal(payload, ctx.token) ← wraps error as "failed to parse token"
↓
vendor/lestrrat-go/jwx/jwt/openid/token_gen.go:970
stdToken.UnmarshalJSON(buf) ← iterates over all claims
↓
vendor/lestrrat-go/jwx/jwt/openid/token_gen.go:1036
json.AssignNextStringToken(&t.email, dec) ← fails: array ≠ string
↓
vendor/lestrrat-go/jwx/internal/json/json.go:45
dec.Decode(&val) ← ROOT CAUSE: strict string decoding
- Dominant language
- Go
- Stars
- 14
- Forks
- 11
- Avg merge
- 2h 33m
- Merged PRs (30d)
- 1
Getting set up
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First steps
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