[OAUTH-WG] draft-ietf-oauth-json-web-token-19 - Examples

Hannes Tschofenig <hannes.tschofenig@gmx.net> Fri, 25 April 2014 10:48 UTC

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Date: Fri, 25 Apr 2014 12:37:40 +0200
From: Hannes Tschofenig <hannes.tschofenig@gmx.net>
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Subject: [OAUTH-WG] draft-ietf-oauth-json-web-token-19 - Examples
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Hi all,

As a document shepherd I have to verify the entire document and this
includes the examples as well.

Section 3.1:

You write:

"
   The following octet sequence is the UTF-8 representation of the JWT
   Header/JWS Header above:

   [123, 34, 116, 121, 112, 34, 58, 34, 74, 87, 84, 34, 44, 13, 10, 32,
   34, 97, 108, 103, 34, 58, 34, 72, 83, 50, 53, 54, 34, 125]
"

The values IMHO are represented in Decimal code point rather than Octal
UTF-8 bytes, as stated above.
See the following online tool to see the difference:
http://www.ltg.ed.ac.uk/~richard/utf-8.cgi?input=%22&mode=char

Note that you could also show a hex encoding instead (e.g., via
http://ostermiller.org/calc/encode.html). Hixie's decoder would then
produce the correct decoding. Here is the link to his software:
http://software.hixie.ch/utilities/cgi/unicode-decoder/utf8-decoder
(Note that this program seems to have flaws for most other options.)

When do a Base64URL encoding of

{"typ":"JWT","alg":"HS256"}

then I get

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9

but your spec says:

eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9

Same with {"iss":"joe","exp":1300819380,"http://example.com/is_root":true}.

My result:
eyJpc3MiOiJqb2UiLCJleHAiOjEzMDA4MTkzODAsImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ

Your result:
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ

Note: I am using this online tool for Base64URL encoding:
http://kjur.github.io/jsjws/tool_b64uenc.html.
Interestingly, when I dump the data into http://jwt.io/ then I get a
correct decoding. It might well be that the kjur.github.io has a flaw.

Just wanted to check what tool you have used to create these encodings.


Section 6.1:

The example in Section 6.1 is the same as in 3.1. Maybe it would be
useful to show something different here.

The example in Appendix A.1 is more sophisticated since it demonstrates
encryption. To verify it I would need to have a library that supports
JWE and RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256. Which library
have you been using?

I was wondering whether it would make sense to add two other examples,
namely for integrity protection. One example showing an HMAC-based keyed
message digest and another one using a digital signature.

Here is a simple example to add that almost all JWT libraries seem to be
able to create and verify:

Header:
{"alg":"HS256","typ":"JWT"}

I use the HS256 algorithm with a shared secret '12345'.

Body:

{"iss":"https://as.example.com","sub":"mailto:john@example.com","nbf":1398420753,"exp":1398424353,"iat":1398420753}

jwt.encode({"iss":"https://as.example.com","sub":"mailto:john@example.com","nbf":1398420753,"exp":1398424353,"iat":1398420753},"12345",
"HS256")

I used http://www.onlineconversion.com/unix_time.htm to create the
date/time values:
"nbf":1398420753 --> Fri, 25 Apr 2014 10:12:33 GMT
"exp":1398424353 --> Fri, 25 Apr 2014 11:12:33 GMT
"iat":1398420753 --> Fri, 25 Apr 2014 10:12:33 GMT

Here is the output created with https://github.com/progrium/pyjwt/ and
verified with http://jwt.io/:
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwczovL2FzLmV4YW1wbGUuY29tIiwiaWF0IjoxMzk4NDIwNzUzLCJzdWIiOiJtYWlsdG86am9obkBleGFtcGxlLmNvbSIsImV4cCI6MTM5ODQyNDM1MywibmJmIjoxMzk4NDIwNzUzfQ.0gfRUIley70bMP7hN6sMWkHwHezdrv2E1LAVcNdTsq4

Ciao
Hannes