https://issues.apache.org/bugzilla/show_bug.cgi?id=52954
Bug #: 52954
Summary: Allowing for broken android HTTP DIGEST support
Product: Tomcat 7
Version: trunk
Platform: All
OS/Version: All
Status: NEW
Severity: enhancement
Priority: P2
Component: Catalina
AssignedTo: [email protected]
ReportedBy: [email protected]
Classification: Unclassified
Android's browser has a slightly broken implementation of DIGEST support,
causing it to fail authentication against Tomcat.
There are 2 issues here which if bypassed in DigestAuthenticator, allow Android
devices to authenticate successfully.
1. nc (nonce-count) is 6 digits instead of 8
nonce-count = "nc" "=" nc-value
nc-value = 8LHEX
Fail as per RFC, however:
"The nc-value is the hexadecimal
count of the number of requests (including the current request)
that the client has sent with the nonce value in this request."
So Android is sending a 24 bit number instead of a 32 bit number.
Tomcat is failing auth based on (nc.length() != 8) which means the request must
match the RFC, but I can't see anything saying that it's necessary to fail
based on a shorter nc-value.
Additionally, if this value wrapped due to being too short (the client would
have to send the same nonce 16777216 times in a single request), we'd fail it
anyway because of the nc check (count <= info.getCount()).
2. uri is specified as an absolute URI, whereas browsers and examples show it
as a relative URI.
However, the RFC specifies this as:
digest-uri = "uri" "=" digest-uri-value
digest-uri-value = request-uri ; As specified by HTTP/1.1
But in RFC 2616 (HTTP/1.1):
Request-URI = "*" | absoluteURI | abs_path | authority
...
"To allow for transition to absoluteURIs in all requests in future
versions of HTTP, all HTTP/1.1 servers MUST accept the absoluteURI
form in requests, even though HTTP/1.1 clients will only generate
them in requests to proxies."
So this one is a bit vague as to whether an absolute uri should cause a
validation fail.
There is an issue listed here showing similar problems against Apache.
http://code.google.com/p/android/issues/detail?id=21239
---------
I've only listed this as an enhancement, as Tomcat isn't broken here, but I'm
interested in opinions:
We could:
1. patch Tomcat to allow the two above situations
2. make the above allowable via a setting in the Realm
3. just continue to block digest auth for all Android devices until they fix
the problem.
Best Regards,
Neale Rudd
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