See https://docs.google.com/document/d/1V9GE97DDrpiDSWdI6dPPy1mQGiWwfEwSViPewMlrwn4/edit?tab=t.0#heading=h.177fzfbof7mt for additional context on Egress gRPC for Search

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There is an open issue on the gRPC library (https://github.com/grpc/grpc/issues/14216) indicating the lack of support for cert (private key PEM file) passwords.

We would need to add upstream support to gRPC for certificate passwords:

• Add an option to pass this to the public API here: https://github.com/grpc/grpc/blob/4943b77a5e497a83beedc6b23b760d8193baa126/include/grpc/credentials.h#L400-L460
• Plumb this down to the SSL handshaking code in gRPC
• Update the PEM private key reader in gRPC to use a passwork callback: https://github.com/grpc/grpc/blob/4943b77a5e497a83beedc6b23b760d8193baa126/src/core/tsi/ssl_transport_security.cc#L1008
• See https://docs.openssl.org/3.3/man3/PEM_read_bio_PrivateKey/#synopsis

And also ensure our local certificate check properly uses the certificate password as well: https://github.com/10gen/mongo/blob/1a49046d343f0cf1e154ecac5654fb8f7030a094/src/mongo/transport/grpc/client.cpp#L683