Only ever pick CURLAUTH_BEARER if we have a Bearer token #2754

dscho · 2018-07-17T12:59:02Z

The Bearer authentication was added to cURL 7.61.0, but there is a
problem: if CURLAUTH_ANY is selected, and the server supports multiple
authentication methods including the Bearer method, we strongly prefer
that latter method (only CURLAUTH_NEGOTIATE beats it), and if the Bearer
authentication fails, we will never even try to attempt any other
method.

This is particularly unfortunate when we already know that we do not
have any Bearer token to work with.

Such a scenario happens e.g. when using Git to push to Visual Studio
Team Services (which supports Basic and Bearer authentication among
other methods) and specifying the Personal Access Token directly in the
URL (this aproach is frequently taken by automated builds).

Let's make sure that we have a Bearer token to work with before we add
it to our available authentication methods.

Signed-off-by: Johannes Schindelin johannes.schindelin@gmx.de

dscho · 2018-07-17T13:03:23Z

Note: while this is a bit pressing of a problem for me because it prevents the Git for Windows SDK from being updated (and I only realized this yesterday, as I forgot to configure the notification mails properly, while the automated build to update the SDK has apparently been broken for over a week...), I realize that this bug might be more complex than meets the eye: I assume that the oauth_bearer is set already when we parse the server's authentication methods, but I do not actually know for sure...

dscho · 2018-07-17T16:12:52Z

@bagder is this a valid approach?

bagder

It makes perfect sense to me!

dscho · 2018-07-18T12:41:00Z

It makes perfect sense to me!

My only concern is: do you see any way that the Bearer authentication should be added to the avail bit field before some caller might add the token? If there is any chance for that right now, my patch would break it.

dscho · 2018-07-18T13:38:30Z

lib/http.c

@@ -925,7 +925,7 @@ CURLcode Curl_http_input_auth(struct connectdata *conn, bool proxy,
            }
          }
          else
-            if(checkprefix("Bearer", auth)) {
+            if(conn->oauth_bearer && checkprefix("Bearer", auth)) {


This is probably the wrong spot to do this. I think pickoneauth() is the correct place. Let me test this.

I just force-pushed an update.

The reason: I was not comfortable meddling with the avail bit-field, as the server did report it as available authentication method, and users of libcurl will see that information.

Instead, the patch now really only verifies at pickoneauth() time that we pick the Bearer method only when we have a Bearer token.

Note: for the Basic authentication method, IIRC it is totally legitimate to pick it without valid credentials, and then kick that result back to the caller, so that credentials can be provided interactively. But for the Bearer authentication, I think it makes no sense to ask for a token interactively, like, ever: you either have it, or you don't. And if you don't have a token, let's not try to authenticate with it ;-)

Oh yes, and of course I verified that the force-pushed patch also fixes the symptom on my side.

dscho · 2018-07-18T15:02:39Z

@bagder could you re-review, please? 😊

dscho · 2018-07-18T15:03:27Z

could you re-review, please?

(I ask because I would like to back-port this fix, to fix Git for Windows snapshot builds for the use case I outlined in the commit message.)

dscho · 2018-07-19T08:54:43Z

(I ask because I would like to back-port this fix, to fix Git for Windows snapshot builds for the use case I outlined in the commit message.)

And I would hate to back-port a change that needs to be modified before entering curl's master branch...

This is necessary e.g. to allow fetching from/pushing to VSTS via https://<user>:<pass>@<host>/<path> (which is frequently used in automated builds, as VSTS does offer Bearer authentication, and cURL would fail to connect because it would not fall back to Basic authentication. This patch has been contributed to the cURL project as curl/curl#2754 Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

bagder · 2018-07-19T18:47:03Z

lib/http.c

    if(!pickhost)
      data->state.authproblem = TRUE;
  }
  if(conn->bits.proxy_user_passwd &&
     ((data->req.httpcode == 407) ||
      (conn->bits.authneg && data->req.httpcode < 300))) {
-    pickproxy = pickoneauth(&data->state.authproxy);
+    pickproxy = pickoneauth(&data->state.authproxy, authmask);


The oauth_bearer is however only documented and implemented to work for host auth... Which really begs the question what libcurl should do if this is asked to be used for proxy auth. Maybe this should just always disable CURLAUTH_BEARER for proxy since there's no option to set the bearer string for it?

Right, and this code is guarded behind a test for proxy_user_password, too...

dscho · 2018-07-19T20:09:39Z

lib/http.c

@@ -517,14 +521,14 @@ CURLcode Curl_http_auth_act(struct connectdata *conn)
  if(conn->bits.user_passwd &&


@bagder Oh, BTW, shouldn't this be if((conn->bits.user_passwd || conn->oauth_bearer) && now?

ah, yes you're right, I believe that would probably be what oauth-bearer users would want!

I'll make it so, in a separate commit, but for convenience in the same PR.

Done: 9453aac

The Bearer authentication was added to cURL 7.61.0, but there is a problem: if CURLAUTH_ANY is selected, and the server supports multiple authentication methods including the Bearer method, we strongly prefer that latter method (only CURLAUTH_NEGOTIATE beats it), and if the Bearer authentication fails, we will never even try to attempt any other method. This is particularly unfortunate when we already know that we do not have any Bearer token to work with. Such a scenario happens e.g. when using Git to push to Visual Studio Team Services (which supports Basic and Bearer authentication among other methods) and specifying the Personal Access Token directly in the URL (this aproach is frequently taken by automated builds). Let's make sure that we have a Bearer token to work with before we select the Bearer authentication among the available authentication methods. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho · 2018-07-20T15:28:42Z

What is this Travis error about ?!?!

E: Unable to locate package clang-6.0

So far, the code tries to pick an authentication method only if user/password credentials are available, which is not the case for Bearer authentictation... Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

dscho · 2018-07-20T18:31:34Z

What is this Travis error about ?!?!
E: Unable to locate package clang-6.0

Seems to have been intermittent...

bagder · 2018-07-20T20:30:31Z

Seems to have been intermittent...

Yes, unfortunately we have a few like that. I try to spot and restart those when they occur...

dscho · 2018-07-21T10:28:05Z

Seems to have been intermittent...

Yes, unfortunately we have a few like that.

Any idea what causes it?

dscho · 2018-07-23T12:18:36Z

@bagder Oh, and: what should I do, still, to get this merged? I got a report on Friday (and root cause confirmed yesterday) that this very same issue happened to a non-Windows based Git user (where I cannot easily work around the bug by releasing a new Git for Windows version with a patched cURL)...

bagder · 2018-07-23T18:54:18Z

I will merge this asap. I'm slower than usual a few weeks while I'm on vacation...

bagder · 2018-07-24T08:12:28Z

Thanks!

So far, the code tries to pick an authentication method only if user/password credentials are available, which is not the case for Bearer authentictation... Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Closes #2754

dscho · 2018-07-24T08:45:38Z

I'm slower than usual a few weeks while I'm on vacation...

Oy, I am sorry! I could have easily waited until the end of your vacation... mortified

The Bearer authentication was added to cURL 7.61.0, but there is a problem: if CURLAUTH_ANY is selected, and the server supports multiple authentication methods including the Bearer method, we strongly prefer that latter method (only CURLAUTH_NEGOTIATE beats it), and if the Bearer authentication fails, we will never even try to attempt any other method. This is particularly unfortunate when we already know that we do not have any Bearer token to work with. Such a scenario happens e.g. when using Git to push to Visual Studio Team Services (which supports Basic and Bearer authentication among other methods) and specifying the Personal Access Token directly in the URL (this aproach is frequently taken by automated builds). Let's make sure that we have a Bearer token to work with before we select the Bearer authentication among the available authentication methods. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Closes curl#2754

So far, the code tries to pick an authentication method only if user/password credentials are available, which is not the case for Bearer authentictation... Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Closes curl#2754

The Bearer authentication was added to cURL 7.61.0, but there is a problem: if CURLAUTH_ANY is selected, and the server supports multiple authentication methods including the Bearer method, we strongly prefer that latter method (only CURLAUTH_NEGOTIATE beats it), and if the Bearer authentication fails, we will never even try to attempt any other method. This is particularly unfortunate when we already know that we do not have any Bearer token to work with. Such a scenario happens e.g. when using Git to push to Visual Studio Team Services (which supports Basic and Bearer authentication among other methods) and specifying the Personal Access Token directly in the URL (this aproach is frequently taken by automated builds). Let's make sure that we have a Bearer token to work with before we select the Bearer authentication among the available authentication methods. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Closes curl#2754

So far, the code tries to pick an authentication method only if user/password credentials are available, which is not the case for Bearer authentictation... Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Closes curl#2754

bagder added HTTP authentication labels Jul 17, 2018

bagder approved these changes Jul 17, 2018

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dscho commented Jul 18, 2018

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dscho force-pushed the bearer-auth-requires-oauth-bearer branch 2 times, most recently from d526cb3 to a1e36d2 Compare July 18, 2018 14:58

dscho force-pushed the bearer-auth-requires-oauth-bearer branch from a1e36d2 to 46ea3c8 Compare July 18, 2018 18:29

bagder reviewed Jul 19, 2018

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dscho commented Jul 19, 2018

View reviewed changes

dscho force-pushed the bearer-auth-requires-oauth-bearer branch from 46ea3c8 to 9d40f70 Compare July 19, 2018 20:10

dscho force-pushed the bearer-auth-requires-oauth-bearer branch from 9d40f70 to cd4011f Compare July 20, 2018 13:15

Pick Bearer authentication whenever a token is available

9453aac

So far, the code tries to pick an authentication method only if user/password credentials are available, which is not the case for Bearer authentictation... Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

bagder closed this in df57b43 Jul 24, 2018

dscho deleted the bearer-auth-requires-oauth-bearer branch July 24, 2018 08:46

bagder mentioned this pull request Jul 30, 2018

Unix: using git client with curl 7.61 and libcurl 7.61 leads to auth failed on TFS with NTLM #2799

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Only ever pick CURLAUTH_BEARER if we have a Bearer token #2754

Only ever pick CURLAUTH_BEARER if we have a Bearer token #2754

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		@@ -517,14 +521,14 @@ CURLcode Curl_http_auth_act(struct connectdata *conn)
		if(conn->bits.user_passwd &&

Only ever pick CURLAUTH_BEARER if we *have* a Bearer token #2754

Only ever pick CURLAUTH_BEARER if we *have* a Bearer token #2754

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Only ever pick CURLAUTH_BEARER if we have a Bearer token #2754

Only ever pick CURLAUTH_BEARER if we have a Bearer token #2754