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https://issues.apache.org/jira/browse/HTTPCLIENT-1855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16197447#comment-16197447
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Alessandro Gherardi commented on HTTPCLIENT-1855:
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BasicAuthCache is thread safe, so no data corruption should occur.
It is true that if multiple threads share the same AuthCache and talk to the
same server at the same time, they could overwrite each other's DigestScheme.
Solving that problem would probably require a lot of rework: Currently, the
auth cache is keyed on HttpHost, so there is only room for one DigestScheme per
host.
The change I'm proposing optimizes the
single-AuthCache-per-HttpHost-per-concurrent thread usecase, by effectively
reusing the same server nonce multiple times. If multiple threads must share
the same AuthCache, more network roundtrips/auth challenges will be needed, so
performance won't be optimal. But things will still work.
I believe that saving network roundtrips/auth challenges is worth the cost of
updating the auth cache on every request.
> Digest auth: Nonce counter not incremented after reuse
> ------------------------------------------------------
>
> Key: HTTPCLIENT-1855
> URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1855
> Project: HttpComponents HttpClient
> Issue Type: Bug
> Components: HttpClient (classic)
> Affects Versions: 4.5.2
> Reporter: Alessandro Gherardi
> Attachments: HttpClient5Digest.java, HttpClientDigest.java,
> httpclient5.log, wireshark.txt
>
>
> I have a client app using httpclient 4.5.2 with BasicCredentialsProvider and
> BasicAuthCache. and web server that requires HTTP digest authentication.
> The client sends 3 requests to the web server.
> When the app sends the first request, the server returns an HTTP 401 with a
> digest challenge. httpclient automatically retries the request with the
> Authorization header. The header contains the nonce returned by the server
> and a nonce counter (nc) of 1. The retry succeeds and httpclient caches the
> DigestScheme.
> For the second request, httpclient uses the cached DigestScheme to calculate
> the Authorization header pre-emptively. The header contains the same nonce
> and specifies a nonce counter of 2. The request succeed without requiring a
> retry.
> For the third request, httpclient uses the cached DigestScheme to calculate
> the Authorization header pre-emptively. Even though the header contains the
> same nonce, the nonce counter is set to 2 again. This causes the server to
> return a 401. httpclient should have incremented the nonce counter to 3.
> I believe that the root cause of this problem is that, although DigestScheme
> increases the nonceCount field every time the authenticate() method is
> called, HttpAuthenticator does not re-cache DigestScheme after reusing it.
> The re-cache is needed because BasicAuthCache stores DigestScheme in
> serialized format.
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