jwt.Parse got "invalid character 'x' looking for beginning of value"

[lggomez]

Migrated from https://github.com/dgrijalva/jwt-go/issues/361:

alanywlee commented on Oct 8, 2019

I am trying to parse a RS256 encoded token (tokenString) from java, it could be successfully decoded by public key in java using the following java code

Jwts.parser().setSigningKey(publicKey).parseClaimsJws(jwt);

However, It could be verified by jwt.SigningMethodRS256.Verify() just as described in https://stackoverflow.com/questions/51834234/i-have-a-public-key-and-a-jwt-how-do-i-check-if-its-valid-in-go

But not able to be jwt.Parse, I tried to write more debug print messages inside the parse function, and verified not even run into it.

    tokenString := "eyJhbGciOiJSUzI1NiIsInppcCI6IkRFRiJ9.eNqqVkqtKFCyMjQ1s7Q0sbA0MtFRyk3NTUot8kxRslIKLbZQggn4JeamAoUcfRz99HxcXRWeze172tr4bFq7Ui0AAAD__w.jBXD4LT4aq4oXTgDoPkiV6n4QdSZPZI1Z4J8MWQC42aHK0oXwcovEU06dVbtB81TF-2byuu0-qi8J0GUttODT67k6gCl6DV_iuCOV7gczwTcvKslotUvXzoJ2wa0QuujnjxLEE50r0p6k0tsv_9OIFSUZzDksJFYNPlJH2eFG55DROx4TsOz98az37SujZi9GGbTc9SLgzFHPrHMrovRZ5qLC_w4JrdtsLzBBI11OQJgRYwV8fQf4O8IsMkHtetjkN7dKgUkJtRarNWOk76rpTPppLypiLU4_J0-wrElLMh1TzUVZW6Fz2cDHDDBACJgMmKQ2pOFEDK_vYZN74dLCF5GiTZV6DbXhNxO7lqT7JUN4a3p2z96G7WNRjblf2qZeuYdQvkIsiK-rCbSIE836XeY5gaBgkOzuEvzl_tMrpRmb5Oox1ibOfVT2KBh9Lvqsb1XbQjCio2CLE2ViCLqoe0AaRqlUyrk3n8BIG-r0IW4dcw96CEryEMIjsjVp9mtPXamJzf391kt8Rf3iRBqwv3zP7Plg1ResXbmsFUgOflAUPcYmfLug4W3W52ntcUlTHAKXrNfaJL9QQiYAaDukG-ZHDytsOWTuuXw7lVxjt-XYi1VbRAIjh1aIYSELEmEpE4Ny74htQtywYXMQNfJpB0nNn8IiWakgcYYMJ0TmKM"

    token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
        fmt.Println("token parse start...")
    ...
    }
    // ... error handling
    if err != nil {
        log.Fatal(err)
    }

It got error message as following

2019/10/08 17:29:38 invalid character 'x' looking for beginning of value exit status 1

I am curious if I can verify token signature, how come not able to parse its header and claims body. Or I missed anything before doing jwt.Parse()

Any comment is highly appreciated....

[lggomez]

The error still happens and as expected there is an invalid JSON input, in this case on the payload:

https://jwt.io/#debugger-io?token=eyJhbGciOiJSUzI1NiIsInppcCI6IkRFRiJ9.eNqqVkqtKFCyMjQ1s7Q0sbA0MtFRyk3NTUot8kxRslIKLbZQggn4JeamAoUcfRz99HxcXRWeze172tr4bFq7Ui0AAAD__w.jBXD4LT4aq4oXTgDoPkiV6n4QdSZPZI1Z4J8MWQC42aHK0oXwcovEU06dVbtB81TF-2byuu0-qi8J0GUttODT67k6gCl6DV_iuCOV7gczwTcvKslotUvXzoJ2wa0QuujnjxLEE50r0p6k0tsv_9OIFSUZzDksJFYNPlJH2eFG55DROx4TsOz98az37SujZi9GGbTc9SLgzFHPrHMrovRZ5qLC_w4JrdtsLzBBI11OQJgRYwV8fQf4O8IsMkHtetjkN7dKgUkJtRarNWOk76rpTPppLypiLU4_J0-wrElLMh1TzUVZW6Fz2cDHDDBACJgMmKQ2pOFEDK_vYZN74dLCF5GiTZV6DbXhNxO7lqT7JUN4a3p2z96G7WNRjblf2qZeuYdQvkIsiK-rCbSIE836XeY5gaBgkOzuEvzl_tMrpRmb5Oox1ibOfVT2KBh9Lvqsb1XbQjCio2CLE2ViCLqoe0AaRqlUyrk3n8BIG-r0IW4dcw96CEryEMIjsjVp9mtPXamJzf391kt8Rf3iRBqwv3zP7Plg1ResXbmsFUgOflAUPcYmfLug4W3W52ntcUlTHAKXrNfaJL9QQiYAaDukG-ZHDytsOWTuuXw7lVxjt-XYi1VbRAIjh1aIYSELEmEpE4Ny74htQtywYXMQNfJpB0nNn8IiWakgcYYMJ0TmKM

The issue here is that we could handle this in a more graceful way rather than returning the raw json parser error

[oxisto]

Fixed by #234