SigningMethod sha256-rsa-mgf1

[Ahrens, Helge]

Dear all,

 

I didn’t find any information about this:

Does simplasaml (I’m currently using v2.0.15) support SigningMethod sha256-rsa-mgf1 (RSASSA-PSS) and if so, where can I change the default? The national (German) IdP is switching from rsa-sha256 and when testing the new setting in our Dev-Environment I encountered this error:

 

***

simplesamlphp DEBUG […] Received SAML2 Response from 'https://int.id.bund.de/idp'.

simplesamlphp DEBUG […] Has 1 candidate keys for validation.

simplesamlphp DEBUG […] Validation with key #0 failed with exception: Unsupported signing algorithm.

 

SimpleSAML\Error\Error: UNHANDLEDEXCEPTION
Backtrace:

2 public/_include.php:31 (SimpleSAML_exception_handler)

1 …/vendor/symfony/error-handler/ErrorHandler.php:619 (Symfony\Component\ErrorHandler\ErrorHandler::handleException)

0 [builtin] (N/A)

Caused by: Exception: Unsupported signing algorithm.

Backtrace:

11 …/vendor/simplesamlphp/saml2/src/SAML2/Utils.php:140 (SAML2\Utils::castKey)

10 …/vendor/simplesamlphp/saml2/src/SAML2/Utils.php:191 (SAML2\Utils::validateSignature)

9 [builtin] (call_user_func)

8 …/vendor/simplesamlphp/saml2/src/SAML2/Message.php:263 (SAML2\Message::validate)

7 modules/saml/src/Message.php:168 (SimpleSAML\Module\saml\Message::checkSign)

6 modules/saml/src/Message.php:602 (SimpleSAML\Module\saml\Message::processResponse)

5 modules/saml/src/Controller/ServiceProvider.php:317 (SimpleSAML\Module\saml\Controller\ServiceProvider::assertionConsumerService)

4 …/vendor/symfony/http-kernel/HttpKernel.php:163 (Symfony\Component\HttpKernel\HttpKernel::handleRaw)

3 …/vendor/symfony/http-kernel/HttpKernel.php:75 (Symfony\Component\HttpKernel\HttpKernel::handle)

2 …/vendor/symfony/http-kernel/Kernel.php:202 (Symfony\Component\HttpKernel\Kernel::handle)

1 src/SimpleSAML/Module.php:234 (SimpleSAML\Module::process)

0 public/module.php:17 (N/A)

***

 

Best wishes and thank you for any hint to a solution!

Helge

[Tim van Dijen]

Hi Helge,

Unfortunately it's not supported. This is not a limitation of SimpleSAMLphp but a limitation of PHP's openssl extension that doesn't support this.

- Tim

Op woensdag 15 januari 2025 om 09:47:24 UTC+1 schreef Ahrens, Helge:

[Ahrens, Helge]

Dear Tim,

 

thank you for your fast reply. So I’ll be forced to change from php-based SAML to another solution? That is unfortunate.

 

Best wishes

Helge

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[Tim van Dijen]

Hi Helge,

No, not necessarily. There are PHP-based crypto-libraries like phpseclibs that do not rely on PHP's openssl extension and that _do_ support RSS-PSS.
The unfortunate part is that the crypto-library underneath SimpleSAMLphp is tightly coupled to the openssl extension and therefore cannot support it.
We will at some point migrate to a better crypto-library, but with current resources for the project this is going to take a _really_ long time :(

-Tim

Op woensdag 15 januari 2025 om 13:18:18 UTC+1 schreef Ahrens, Helge:

[Ahrens, Helge]

Dear Tim,

 

thank you for the insight! Do you have an overview of the parts that would need change? Because either I’ll try and changing it in my simplesaml installation and maybe that can help your effort for migration as well or I’ll have to migrate to another backend (not sure how much work that might be).

To view this discussion visit https://groups.google.com/d/msgid/simplesamlphp/313a3715-fe0f-4854-83c4-656ab9581a1bn%40googlegroups.com.

[Tim van Dijen]

Hi Helge,

The crypto-library that is in use now is https://github.com/robrichards/xmlseclibs ...

Because that one is not very well maintained, we decided to set up our very own crypto-library under https://github.com/simplesamlphp/xml-security .

That one by itself is finished, but not yet in use by SimpleSAMLphp because the API was changed completely.
It has support for multiple back-ends, with one back-end implemented (openssl), but it could also have a backend for phpseclib.

So two steps that need to be done:
- Add backend for phpseclib into the xml-security library

- Integrate this new library into SimpleSAMLphp

It will be quite a lot of work, I think, but we would really appreciate your help!

- Tim

Op woensdag 15 januari 2025 om 13:43:28 UTC+1 schreef Ahrens, Helge:

[Ahrens, Helge]

Dear Tim,

 

I’ll take a look at the code, however I have a tight schedule (the change must be completed by the end of June). Depending on how we estimate the effort in the team, we may have to change the backend.

.
To view this discussion visit https://groups.google.com/d/msgid/simplesamlphp/4ffd7369-17b7-42f2-9a8f-1bb3bc955934n%40googlegroups.com.

[Ahrens, Helge]

Dear Tim,

 

are there already issues/tasks in the simplesamlphp and xml-security repositories where we could start working on?

I’m a little lost where I should start, except that I would start by trying to integrate phpseclib directly in a local simplesamlphp instance to see if I can get it working. From there I could try integrating it in xml-security. Or should I first try to integrate xml-security in simplesamlphp?

 

Best wishes

Helge

To view this discussion visit https://groups.google.com/d/msgid/simplesamlphp/e4edf2a3d55d49d2bd7e8616a470c437%40ulb.hhu.de.

[Peter Schober]

Tim van Dijen <tvd...@gmail.com> [2025-01-15 15:00 CET]:

> - Add backend for phpseclib into the xml-security library

Btw, is libsodium an option here? It should come with PHP core since
v7.2, so no new dendency added.
The main reason I could think of why this wouldn't work is (in
the words of some older paragonie.com article[1]):
"Stringent requirements to maintain interoperability with weak
cryptography."
Best,
-peter

[1] https://paragonie.com/blog/2015/09/how-to-safely-implement-cryptography-in-any-application

[Tim van Dijen]

Hi Peter,

I don't think this is true, at least not for all platorms, because I still have to install ext-sodium manually on my distro.

Anyway, I don't think it matters all that much... phpseclibs or sodium.. It both comes down to fitting in a new type of backend..

I personally have a slight preference for phpseclibs because it's a pure PHP-solution, making it much more flexible.

- Tim

Op dinsdag 21 januari 2025 om 13:01:00 UTC+1 schreef Peter Schober:

[Peter Schober]

Tim van Dijen <tvd...@gmail.com> [2025-01-21 13:41 CET]:

> I don't think this is true, at least not for all platorms, because I
> still have to install ext-sodium manually on my distro.

I was a bit inprecise before, I'll quote from the docs[1] instead:

> As of PHP 7.2.0 this extension is bundled with PHP.

Best,
-peter

[1] https://www.php.net/manual/en/sodium.installation.php

[monk...@gmail.com]

I was digging into the openssl versions in php and and the released openssl versions. 

I see that openssl 3.5.0 has some promise, for example with RSA_FLAG_TYPE_RSASSAPSS. That constant or ones like it do not exist in php-8.4.6/ext/openssl. I also don't see RSASSA in ext/openssl in git master for php.

I also found this heavy handed patch which passes off RSASSA_PSS requests to the phpseclib3\Crypt library from inside the robrichards/xmlseclibs library.

https://github.com/robrichards/xmlseclibs/pull/262

I thought I would put my findings from the little search around here in case somebody reads this thread.