BoringSSL Certificate Compression

Question

I was looking for a RFC8879 implementation and found out that BoringSSL has it implemented.

However I haven't found out how can I enable this feature, since the certificate is not compressed by default and there is no parameter in the BoringSSL's TLS client for that.

Does anyone have already worked with this and can give me some help?

Answer 1

SSL_CTX_add_cert_compression_alg(SSL_CTX *ctx, uint16_t alg_id,
                                     bssl::CertCompressFunc compress,
                                     bssl::CertDecompressFunc decompress)

You need to set pair of callbacks for each algorithm. ZLIB has index 1, BROTLI 2, ZSTD 3.