Basic authentication is not really possible to get working with manually-issued certs

[xefinity]

From my quick look at code, i found out that there is key exchange public key signing in source, but no way to set keys for it are provided in the interface. (It is possible to set them through certificates, but certificates don't look like they are made for usage outside Steamworks).
And my question is: can i set keys for signing and verifying key exchange public keys using only interface?
If no, i think it's worth considering adding some simple API for that, for example:

AddKeyExchangePublicKeys(CECSigningPublicKey* keys, size_t keyCount);
SetKeyExchangePrivateKey(CECSigningPrivateKey key);

(CECSigningPublic/PrivateKey are here for example)
I think, it will improve protection against MITM.

[zpostfacto]

Sorry, what exactly do you want to do?

The certificate format is proprietary (it is not X509), but the framework is pretty standard stuff. There are methods to set a particular certificate, and a certificate tool, if you want to generate one.

Also, just to clarify, the Diffie-Hellman key exchange is always done with ephemeral keys. The keys used for signing have longer lifetimes. What was your goal in specifying a particular key to use for key exchange?

[xefinity]

I guess I poorly translated the text from Russian, so in short I want to sign keys that are exchanged so that I can verify that they weren't tampered with. (Like TLS, where certificates are signed by CA). ср, 15 июн. 2022 г. в 03:59, Fletcher Dunn ***@***.***>:

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Sorry, what exactly do you want to do? The certificate format is proprietary (it is not X509), but the framework is pretty standard stuff. There are methods to set a particular certificate, and a certificate tool, if you want to generate one. Also, just to clarify, the Diffie-Hellman key *exchange* is always done with ephemeral keys. The keys used for signing have longer lifetimes. What was your goal in specifying a particular key to use for key exchange? — Reply to this email directly, view it on GitHub <#237 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AR5IDSDRU7CT34XUVIPZT5TVPETHRANCNFSM5YYO7LDA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[zpostfacto]

There is a basic cert store, and a certificate generation tool. And you can hardcode a particular trusted root AC key by #defining STEAMNETWORKINGSOCKETS_HARDCODED_ROOT_CA_KEY. However, I suspect there might be some missing pieces, depending on your use case. I can think of at least three:

1.) The cert tool actually doesn't have a way to specify the identity that should go into the cert.
2.) There isn't an easy way to tell the library to use a particular private key and cert.
3.) There isn't really an API for adding intermediate certs into the cert store.

Each of those would be really easy to add, though. All of the stuff under the hood is present, there just isn't the exact API call you need.

NOTE: It might seem kinda weird that these don't exist to handle the "typical" use case, but it actually hasn't come up, because all of the certificate issuance in Steam and partners is all automated! We never issue certificates by hand.

One thing that would be quite a lot of work to fix is that, unlike TLS, we do not send intermediate certs in the handshake. We require that both sides have all required intermediate certs. So if you are using any intermediate certs you need to make sure they are distributed. If you only have a single root CA, then you just hardcode the trusted key.

If you tell me more about your use case, I might be able to point you in the right direction if you are interested in adding those missing pieces. Again, I think it would be pretty easy, as everything under the hood is present, there just isn't the highest level API entry point to do exactly what you need.

[xefinity]

I guess this is what I need. The only modifications needed are adding identity to certtool generation (for me it's plain string), re-enabling signed certificate enforcement, removing appID check and adding ability to parse certificate from string (or outputting certificate in array form). ср, 15 июн. 2022 г., 19:28 Fletcher Dunn ***@***.***>:

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I'm not sure what your use case is exactly, but I suspect there might be some missing pieces. I can think of at least three: 1.) The cert tool actually doesn't have a way to specify the identity that should go into the cert. 2.) There isn't an easy way to tell the library to use a particular private key and cert into the library. 3.) There isn't really an API for adding intermediate certs into the cert store. Each of those would be really easy to add, though. All of the stuff under the hood is present, there just isn't the exact API call you need. There is a basic cert store, and a certificate generation tool. And you can hardcode a particular trusted root AC key by #defining STEAMNETWORKINGSOCKETS_HARDCODED_ROOT_CA_KEY. NOTE: It might seem kinda weird that these don't exist to handle the "typical" use case, but it actually hasn't come up, because all of the certificate issuance in Steam and partners is all automated! We never issue certificates by hand. One thing that would be quite a lot of work to fix is that, unlike TLS, we do not send intermediate certs in the handshake. We require that both sides have all required intermediate certs. So if you are using any intermediate certs you need to make sure they are distributed. If you only have a single root CA, then you just hardcode the trusted key. If you tell me more about your use case, I might be able to point you in the right direction if you are interested in adding those missing pieces. Again, I think it would be pretty easy, as everything under the hood is present, there just isn't the highest level API entry point to do exactly what you need. — Reply to this email directly, view it on GitHub <#237 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AR5IDSDDW3RQ4K3OUKBEAH3VPIAETANCNFSM5YYO7LDA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[zpostfacto]

I changed the title to clarify what is needed here. If I have some time I'll add the needed features.

I don't think there's anything unusual your use case, it seems like an entirely normal situation. It's actually kind of surprising that nobody has complained about this not being possible before.

[ResakaGit]

I'd like to work on this. Following the scope outlined above, I'll prepare a PR adding the missing pieces: (1) let the cert tool specify the identity that goes into the cert, (2) an API to tell the library to use a particular cert + private key, and (3) a way to add intermediate certs to the cert store.

[ResakaGit]

I've opened #427 with the first part of this: a way to install a root of trust in the open source build (GameNetworkingSockets_AddTrustedCert), plus GameNetworkingSockets_SetAppID, since cert validation checks the local app ID and there was no way to set it in the OSS build. It also resurrects test_pki with a runtime-generated PKI.

While working on it, a few design questions came up that I'd appreciate your input on:

1. Self-signed roots installed by the app. Rather than a compile-time switch, Add API to install trusted CA certs in the open source build #427 marks certs installed through the new entry point as explicitly trusted by the app, and only those may act as self-signed roots -- the hardcoded Valve root stays trusted, and certs that arrive any other way are rejected exactly as before (so the "only trust the one hardcoded root key" invariant is preserved for anything the app didn't vouch for, including any code that populates the store dynamically). Does that approach work for you, or would you prefer it gated at compile time?

2. Naming. I used the GameNetworkingSockets_ prefix (like Init/Kill, since these are OSS-only process-level functions) rather than SteamNetworkingSockets_ (used by the global setters). Happy to rename.

3. Certtool follow-up. For the remaining pieces I'd add --identity (reusing SteamNetworkingIdentity::ParseString, and failing early if no app is specified, since RecvCryptoHandshake requires app_ids on identity-bound certs) and a flag to emit private_key_data in the signed cert blob, which SetCertificate already consumes -- that closes the gap reported in Self signed certificates #384 without touching the library. Does that match what you had in mind in your earlier comment?

4. CSR flow. GetCertificateRequest tells users to pass the blob to SteamDatagram_CreateCert, which isn't part of this repo. Would you want the certtool to grow a sign_cert_request command that consumes that blob (taking only key_data from it; identity/app/pops always from operator flags), or leave that out of scope for now?