Use SSL in gRPC client server communication

Question

I know nothing about SSL/TLS and am trying to use SSL/TLS channel in gRPC by following instructions found online. Here is the server code:

      std::string server_address("0.0.0.0:50051");
      GreeterServiceImpl service;
    
      grpc::SslServerCredentialsOptions::PemKeyCertPair pkcp ={"a","b"};
      grpc::SslServerCredentialsOptions ssl_opts;
      ssl_opts.pem_root_certs="";
      ssl_opts.pem_key_cert_pairs.push_back(pkcp);
    
      std::shared_ptr<grpc::ServerCredentials> creds;
      creds = grpc::SslServerCredentials(ssl_opts);
    
      ServerBuilder builder;
      builder.AddListeningPort(server_address, creds);
      builder.RegisterService(&service);
      std::unique_ptr<Server> server(builder.BuildAndStart());

The server won't start and terminates with following error.

E1115 13:00:55.657846941   17129 ssl_transport_security.c:636] Invalid cert chain file.
E1115 13:00:55.657936436   17129 security_connector.c:830]   Handshaker factory creation failed with TSI_INVALID_ARGUMENT.
E1115 13:00:55.657954952   17129 server_secure_chttp2.c:344] {"created":"@1479243655.657946821","description":"Unable to create secure server with credentials of type Ssl.","file":"src/core/ext/transport/chttp2/server/secure/server_secure_chttp2.c","file_line":242,"security_status":1}
Server listening on 0.0.0.0:50051
Segmentation fault (core dumped)

All I want to do is just use SSL for server and client communication. Looks like I am missing proper certificates in the server and believe similar things needed in client. Since I don't have any background in SSL it would be great if anybody can point me to examples about how to create those certificates and use properly for gRPC communication.

Answer 1

It appears to be problem with the way the certificates are created. I forgot the post in StackOverflow that had shown how to create the certificates. Used that method and plugged-in the key and certificates to make it work.

Here is how I created the key (server.key) and the certificates (server.crt).

    mypass="pass123"

    echo Generate server key:
    openssl genrsa -passout pass:$mypass -des3 -out server.key 4096

    echo Generate server signing request:
    openssl req -passin pass:$mypass -new -key server.key -out server.csr -subj  "/C=US/ST=CA/L=SanFrancisco/O=Google/OU=youtube/CN=localhost"

    echo Self-sign server certificate:
    openssl x509 -req -passin pass:$mypass -days 365 -in server.csr -signkey server.key -set_serial 01 -out server.crt

    echo Remove passphrase from server key:
    openssl rsa -passin pass:$mypass -in server.key -out server.key

    rm server.csr

Pay attention to the use of localhost here. Same should be used at the time of client channel creation. I modified the example from grpc code base to use these. The server that looked like below.

    std::string server_address("0.0.0.0:50051");
    GreeterServiceImpl service;

    std::string servercert = read_keycert("server.crt");
    std::string serverkey = read_keycert("server.key");

    grpc::SslServerCredentialsOptions::PemKeyCertPair pkcp;
    pkcp.private_key = serverkey;
    pkcp.cert_chain = servercert;

    grpc::SslServerCredentialsOptions ssl_opts;
    ssl_opts.pem_root_certs="";
    ssl_opts.pem_key_cert_pairs.push_back(pkcp);

    std::shared_ptr<grpc::ServerCredentials> creds;
    creds = grpc::SslServerCredentials(ssl_opts);

    ServerBuilder builder;
    builder.AddListeningPort(server_address, creds);
    builder.RegisterService(&service);
    std::unique_ptr<Server> server(builder.BuildAndStart());
    server->Wait();

In client only certificate is required. Here is how it is used in my case.

    std::string cacert = read_keycert("server.crt");
    grpc::SslCredentialsOptions ssl_opts;
    ssl_opts.pem_root_certs=cacert;

    auto ssl_creds = grpc::SslCredentials(ssl_opts);
    GreeterClient greeter(grpc::CreateChannel("localhost:50051", ssl_creds));

The way the key and certificates are generated and used is different in each use case. I think if two servers communicate then these may be different. Not sure. Hope this helps some newbie to start with secure SSL/TLS in gRPC C++.