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Add issuer, audience and azp checks in bearer token validator #864

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merged 3 commits into from
Jun 7, 2024

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julien-nc
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The bearer token validation is less complete than the login controller one.

  • add issuer, audience and azp (authorized party) checks in bearer token validator
  • make it possible to disable bearer token audience check via config.php.

closes #856

@julien-nc julien-nc added enhancement New feature or request 3. to review labels May 10, 2024
@julien-nc julien-nc force-pushed the enh/856/add-bearer-token-audience-check branch from 99ea021 to bc823aa Compare May 10, 2024 09:39
return null;
}
} else {
$this->logger->debug('Multiple audiences but no authorized party (azp) in the id token');
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Suggested change
$this->logger->debug('Multiple audiences but no authorized party (azp) in the id token');
$this->logger->debug('Multiple audiences but no authorized party (azp) in the access token');

or simple token may be?

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ID tokens are JWT tokens. Access tokens are more or less equivalent to OAuth tokens. This log message is correct IMO.

lib/User/Validator/SelfEncodedValidator.php Outdated Show resolved Hide resolved
$checkAudience = !isset($oidcSystemConfig['selfencoded_bearer_validation_audience_check'])
|| !in_array($oidcSystemConfig['selfencoded_bearer_validation_audience_check'], [false, 'false', 0, '0'], true);
if ($checkAudience) {
if (!($payload->aud === $provider->getClientId() || in_array($provider->getClientId(), $payload->aud, true))) {
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@SagarGi SagarGi May 23, 2024

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hi @julien-nc I check out this PR. In case we have a single audience in the access token other than nextcloud.
for example i tried to make request with with access token:

   "aud": "client_other_than_nextcloud"

i got server error with status code 500 as:

<?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
    <s:exception>TypeError</s:exception>
    <s:message>in_array(): Argument #2 ($haystack) must be of type array, string given</s:message>
</d:error>

It seems like it is checking for multiple audience as an array but for single we have only string. Might be the reason for the error?

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Audience can be a string or an array. The check is now safer. Any better?

@julien-nc julien-nc force-pushed the enh/856/add-bearer-token-audience-check branch from bc823aa to 022ff1a Compare May 23, 2024 15:15
@julien-nc julien-nc force-pushed the enh/856/add-bearer-token-audience-check branch from 022ff1a to 6984473 Compare June 3, 2024 11:22
@julien-nc
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@wielinde Could you say again what was your concern about the azp check?

The current check (when validating the token for API calls) is:
If there are multiple audiences in the token (the aud attribute of the token is an array), we want the azp token attribute (authorized party) to be equal to the Oidc client ID.

This was implemented following points 4 and 5 of https://openid.net/specs/openid-connect-core-1_0.html#IDTokenValidation

Do you think this check only makes sense to authenticate in NC but not when validating a token used to make API calls?

@wielinde
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wielinde commented Jun 3, 2024

@julien-nc I understand the specification that you have linked above in the following manner:

Only when there is an azp is given, then it shall be taken into account. However, that it is present in a token is not the default. In a vanilla OIDC setup, the azp shall not be added to a token, unless required by a OIDC extension.

And I am not aware of any such OIDC extension. So from my understanding, I would remove the requirement that the an azp must be given whenever an array of aud is present. And when azp is given, then it needs to be in the list auf aud AND be the Nextcloud client. Does that make sense?

// FYI @ba1ash

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julien-nc commented Jun 4, 2024

@wielinde I can't remember where I found a different description of how the azp check should be done. Anyway let's stick to this one.
For both login token and bearer token, the check is now: (Independently of the aud claim) If the token has the azp claim, it should be equal to the Oidc client ID.
If audience check is disabled for bearer token validation, the azp is not checked even if it's present.

All good?

@wielinde
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wielinde commented Jun 4, 2024

@julien-nc From my understanding of the spec, that looks good, now. Thank you.

@julien-nc julien-nc requested a review from SagarGi June 7, 2024 09:52
…ake it possible to disable audience check via config

Signed-off-by: Julien Veyssier <[email protected]>
Signed-off-by: Julien Veyssier <[email protected]>
@julien-nc julien-nc force-pushed the enh/856/add-bearer-token-audience-check branch from 8cdbd7e to 91e7712 Compare June 7, 2024 10:00
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Code looks good 👍

@julien-nc julien-nc merged commit a3980ce into main Jun 7, 2024
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@julien-nc julien-nc deleted the enh/856/add-bearer-token-audience-check branch June 7, 2024 13:56
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Audience claim verification check with Bearer token
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