Extend backend TLS configuration with cert host and SNI#168
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To get closer to parity with C@E backend configuration, we add the ability to specify a certificate hostname, distinct from both the host URI or any override host. In addition, backends can now specify whether to use SNI or not; if they do, and the cert hostname is present, it will be used for SNI. That is slightly less flexible than C@E, which allows distinct SNI and cert hosts. That's not currently possible with the TLS implementation we're using in Viceroy, and the C@E customization is mostly used to _disable_ SNI, which we provide here using a dedicated flag. The new backend settings are: * `cert_host` to specify the hostname for certificate checking (and SNI, if enabled) * `use_sni`, a boolean specifying whether to employ SNI for the backend. Both settings are optional. If `cert_host` is not specified, the host from the backend URI is used instead. If `use_sni` is not specified, SNI is enabled by default.
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To get closer to parity with C@E backend configuration, we add the ability to specify a certificate hostname, distinct from both the host URI or any override host. In addition, backends can now specify whether to use SNI or not; if they do, and the cert hostname is present, it will be used for SNI.
That is slightly less flexible than C@E, which allows distinct SNI and cert hosts. That's not currently possible with the TLS implementation we're using in Viceroy, and the C@E customization is mostly used to disable SNI, which we provide here using a dedicated flag.
The new backend settings are:
cert_hostto specify the hostname for certificate checking (and SNI, if enabled)use_sni, a boolean specifying whether to employ SNI for the backend.Both settings are optional. If
cert_hostis not specified, the host from the backend URI is used instead. Ifuse_sniis not specified, SNI is enabled by default.Note: this PR does not include tests, which would require quite a bit of scaffolding to do properly. I have, however, tested locally using a real
fastly.tomlprovided by a customer, which requirescert_hostspecification to properly reach the backend.