RFD: Services lockdown for security providers

[Anthony Scarpino]

Hi Martin,

Interesting proposal.  I think Alternative 1 is a better direction to 
explore from a code structure standpoint.  If I remember correctly, 
Preferred Provider is accessed when getting a service or instance of the 
algorithm.  That happens on a per-operation basis.  What you describe is 
something that would reshape contents of the ProviderList where 
algorithms or services would not be in the list at all.  That is were I 
think #2 gets too complex in trying to handle both in the same property. 
  #2 may end up putting all checks in a per-operation check, hindering 
performance every time as the list grows.

I agree this is mostly used in the FIPS situation or where someone wants 
to disable an algorithm completely, say MD5.  In those cases it's best 
to just prevent the algorithm from ever being available.

On the smaller details side that you list.  I think the name ".enabled" 
doesn't fit, particularly as the first thing in the example disables all 
Ciphers :).  I don't have any suggestions at this time.

As far as the syntax.  I think it maybe a bit difficult to parse in code 
and mental to disable all Ciphers, then enable just for SunJCE and SUN. 
The SUN '*" confused me until I realized you were enabling Ciphers. 
Seems too easy to get wrong.  I know you weren't making a formal spec, 
but we have to start somewhere.

thanks

Tony


On 2/17/23 10:52 AM, Martin Balao wrote:
> Hi,
> 
> We would like to discuss a limitation in the current configuration 
> capabilities for security providers and possible solutions that we are 
> exploring (†).
> 
> As you know, current configuration capabilities in java.security allow 
> users to install security providers, decide their priority in a list 
> (security.provider.<n> properties) and even circumvent this priority for 
> specific algorithms (jdk.security.provider.preferred property). However, 
> there is no granularity in terms of what service types and algorithms 
> are enabled once a security provider is installed: it's an all or 
> nothing scheme. It is worth noting that security providers can bring 
> with them a diverse range of service types. As an example, the SUN 
> security provider comes with the following service types: SecureRandom, 
> Signature, KeyPairGenerator, AlgorithmParameterGenerator, 
> AlgorithmParameters, KeyFactory, MessageDigest, CertificateFactory, 
> KeyStore, CertStore, Policy, Configuration, CertPathBuilder and 
> CertPathValidator [1].
> 
> In some cases, the user may need to enforce that all cryptographic 
> primitives come from a specific security provider. This could happen, 
> for example, when operating in a FIPS-compliant environment or under 
> strict security policies. To better illustrate, let's say that the user 
> requires that all cryptographic operations are performed in a Hardware 
> Security Module (HSM). On the OpenJDK side, this means that the 
> implementation for Cipher, Signature, Mac and other cryptographic 
> services must be the one in the SunPKCS11 security provider. Let's also 
> suppose that other non-cryptographic services such as those for 
> certificates validation and TLS are required, and their implementation 
> is in the SUN and SunJSSE security providers respectively. Setting 
> SunPKCS11 at the highest priority of the list is not a strong guarantee 
> to ensure that all cryptographic operations come from it: it's possible 
> that an algorithm for Signature is not implemented in SunPKCS11 or in 
> its underlying token but in the SUN security provider. Disabling the SUN 
> security provider wouldn't be an option in this case because we need its 
> certificates validation service.
> 
> This problem goes beyond OpenJDK default security providers. Even if we 
> come up with a new layout for service types, algorithms and providers 
> —putting backward compatibility issues aside—, there is always the 
> possibility that a 3rd party security provider does not follow any 
> services grouping convention. It might also be the case that we need to 
> disable a specific algorithm only —i.e. for cryptographic policy 
> reasons— and TLS or JAR signing properties fall short.
> 
> In our view, it would be beneficial to add more configuration 
> flexibility and control to the existing API in which any security 
> provider can be plugged in, in the form of deciding which service types 
> and algorithms are enabled for each installed provider.
> 
> There are 2 alternatives that we are exploring to tackle this problem.
> 
> Alternative #1
> ===========================
> 
> Introduce a new security property to decide which service types and 
> algorithms are enabled for each security provider. The default value for 
> this property would be empty, which keeps this feature disabled and all 
> services from installed security providers available.
> 
> As for the new property's syntax and semantics, we've been considering 
> an allow-list along the lines of:
> 
> jdk.security.provider.enabled = security-provider-1 { service-type-1 : 
> alg-1, ... ; ... } , ...
> 
> Note: we need a formal syntax specification, this is for illustration only.
> 
> As part of the syntax we are considering the use of wildcards (*) to 
> match multiple security providers, service types and algorithms, and 
> minus signs (-) to remove service types. When a service type is removed, 
> the action applies to all algorithms and any attempt to specify them 
> explicitly would be an error. The minus sign cannot be used at the 
> algorithm level. We are also thinking that in case of a partial or total 
> contradiction between conditions, the right-most value applies on top of 
> the others. If a security provider, service type or algorithm does not 
> exist, we can simply write a debug warning and ignore it. As for the 
> name of the algorithms, we can also include Ciphers transformations.
> 
> Example:
> 
> jdk.security.provider.enabled = * { -Cipher }, SunJCE { Cipher : 
> AES/GCM/NoPadding, DES ; Signature }, SUN { * ; -Signature }
> 
> This would be interpreted as:
> 
>   * Irrespective of the provider (*), Cipher services should be removed 
> (-). This rule would be superfluous in this case because the property 
> itself is an allow-list and there is nothing to the left that enables 
> Cipher service types for any provider.
>   * From the SunJCE security provider, Cipher services with 
> AES/GCM/NoPadding and DES transformations are allowed, and Signature 
> services with any algorithm are allowed. Notice that there is a shortcut 
> here: the algorithm list that follows the service name, "': alg-1, ..." 
> is optional. When omitted all the service's algorithms are enabled.
>   * From the SUN security provider, every service type is allowed except 
> Signature (recall that a minus sign can only apply to a service, 
> removing all associated algorithms).
> 
> It's not the goal of this proposal to invalidate property values that 
> lead to inconsistent internal states, such as "the Cipher service of 
> SunJCE depends on AlgorithmParameters from SUN". This is because the 
> combinations for a check are virtually infinite: there can be 3rd party 
> security providers with their own semantics and dependencies. In the 
> same way, we cannot determine at start time any application 
> dependencies. It's up to the user to analyze all types of dependencies 
> before setting a value.
> 
> 
> Alternative #2
> ===========================
> 
> Introduce a boolean security property to turn the value of the existing 
> jdk.security.provider.preferred property into the only combinations of 
> algorithm, service and provider that are allowed:
> 
> jdk.security.provider.preferredOnly = true
> 
> The default value for the new property would be "false", keeping the 
> current "preferred" behavior in which all algorithms and services from 
> installed security providers are available.
> 
> Contrary to Alternative #1, the user has to explicitly list the 
> algorithms and cannot rely on wildcards to express wide categories such 
> as "all Cipher algorithms from SunJCE" or "all algorithms from SunJCE". 
> The use of minus signs to remove service types or algorithms wouldn't be 
> available either.
> 
> In order to mitigate the burden on users we can consider extending 
> jdk.security.provider.preferred syntax as long as we keep 
> backward-compatibility and stay within the boundaries of a "preferred" 
> semantics. For example, we can accept a value of 
> "jdk.security.provider.preferred=SunJCE" to mean that any service and 
> any algorithm from SunJCE is either preferred or allowed, depending on 
> the value of jdk.security.provider.preferredOnly. This case would be a 
> service type and algorithm wildcard. We can also define an 
> algorithms-only wildcard, such as Cipher.*:SunJCE.
> 
> Alternative #2 has the advantage of reusing most or all of the existing 
> syntax. However, it's worth noticing that it implies an overloaded 
> semantic that can turn confusing or inconvenient in some cases. As an 
> example, a user that relies on the prioritized security providers list 
> for most of the algorithms and has only a few preferred exceptions, 
> would need to express preferences by extension upon turning on this 
> feature. Alternative #1 keeps preferences and availability as two 
> separate concepts, in a more clear way.
> 
> 
> Thanks,
> Martin.-
> 
> -- 
> [1] - 
> https://docs.oracle.com/en/java/javase/17/security/oracle-providers.html#GUID-3A80CC46-91E1-4E47-AC51-CB7B782CEA7D
> (†) - Thanks to @fferrari for his contributions to this proposal.
>