|author||David Benjamin <firstname.lastname@example.org>||Thu May 20 15:57:09 2021 -0400|
|committer||David Benjamin <email@example.com>||Fri Jun 11 18:36:38 2021 +0000|
Add most of an ECH client implementation. Based on an initial implementation by Dan McArdle at https://boringssl-review.googlesource.com/c/boringssl/+/46784 This CL contains most of a client implementation for draft-ietf-tls-esni-10. The pieces missing so far, which will be done in follow-up CLs are: 1. While the ClientHelloInner is padded, the server Certificate message is not. I'll add that once we resolve the spec discussions on how to do that. (We were originally going to use TLS record-level padding, but that doesn't work well with QUIC.) 2. The client should check the public name is a valid DNS name before copying it into ClientHelloOuter.server_name. 3. The ClientHelloOuter handshake flow is not yet implemented. This CL can detect when the server selects ClientHelloOuter, but for now the handshake immediately fails. A follow-up CL will remove that logic and instead add the APIs and extra checks needed. Otherwise, this should be complete, including padding and compression. The main interesting point design-wise is that we run through ClientHello construction multiple times. We need to construct ClientHelloInner and ClientHelloOuter. Then each of those has slight variants: EncodedClientHelloInner is the compressed form, and ClientHelloOuterAAD just has the ECH extension erased to avoid a circular dependency. I've computed ClientHelloInner and EncodedClientHelloInner concurrently because the compression scheme requires shifting the extensions around to be contiguous. However, I've computed ClientHelloOuterAAD and ClientHelloOuter by running through the logic twice. This probably can be done better, but the next draft revises the construction anyway, so I'm thinking I'll rework it then. (In the next draft, we use a placeholder payload of the same length, so we can construct the ClientHello once and fill in the payload.) Additionally, now that we have a client available in ssl_test, this adds a threading test to confirm that SSL_CTX_set1_ech_keys is properly synchronized. (Confirmed that, if I drop the lock in SSL_CTX_set1_ech_keys, TSan notices.) Change-Id: Icaff68b595035bdcc73c468ff638e67c84239ef4 Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48004 Reviewed-by: Adam Langley <firstname.lastname@example.org>
BoringSSL is a fork of OpenSSL that is designed to meet Google's needs.
Although BoringSSL is an open source project, it is not intended for general use, as OpenSSL is. We don't recommend that third parties depend upon it. Doing so is likely to be frustrating because there are no guarantees of API or ABI stability.
Programs ship their own copies of BoringSSL when they use it and we update everything as needed when deciding to make API changes. This allows us to mostly avoid compromises in the name of compatibility. It works for us, but it may not work for you.
BoringSSL arose because Google used OpenSSL for many years in various ways and, over time, built up a large number of patches that were maintained while tracking upstream OpenSSL. As Google's product portfolio became more complex, more copies of OpenSSL sprung up and the effort involved in maintaining all these patches in multiple places was growing steadily.
Currently BoringSSL is the SSL library in Chrome/Chromium, Android (but it's not part of the NDK) and a number of other apps/programs.
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