I know I can choose to verify the client with --ssl-verify
, but how can I specify which CA chain that I want to use? I'm used to providing a file (like with curl's --cacert
or WEBrick's :SSLCACertificateFile
), so I've got one ready, but I can't seem to find documentation on how to pass it to thin
.
Short answer: You can't.
Long answer: You could, but you'd have to update EventMachine's C++ extension that builds the ssl connection, and update the call stack up through EventMachine and Thin to pass the certificate authority file along.
How I found this out: Source Code! It's all on github
thin's command line opts are parsed in thin:lib/thin/runner.rb
opts.separator "SSL options:"
opts.on( "--ssl", "Enables SSL") { @options[:ssl] = true }
opts.on( "--ssl-key-file PATH", "Path to private key") { |path| @options[:ssl_key_file] = path }
opts.on( "--ssl-cert-file PATH", "Path to certificate") { |path| @options[:ssl_cert_file] = path }
opts.on( "--ssl-verify", "Enables SSL certificate verification") { @options[:ssl_verify] = true }
and then used to create a controller
controller = case
when cluster? then Controllers::Cluster.new(@options)
when service? then Controllers::Service.new(@options)
else Controllers::Controller.new(@options)
end
In thin:lib/controllers/controller.rb
the ssl options are pulled back out to be stored with the server object
# ssl support
if @options[:ssl]
server.ssl = true
server.ssl_options = { :private_key_file => @options[:ssl_key_file], :cert_chain_file => @options[:ssl_cert_file], :verify_peer => @options[:ssl_verify] }
end
and are finally used to initialize the connection to the client
def initialize_connection(connection)
connection.backend = self
connection.app = @server.app
connection.comm_inactivity_timeout = @timeout
connection.threaded = @threaded
if @ssl
connection.start_tls(@ssl_options)
end
This connection is an EventMachine::Connection
, defined in eventmachine:lib/em/connection.rb
. EventMachine::Connection#start_tls
passes the parameters along to EventMachine::set_tls_parms
.
def start_tls args={}
priv_key, cert_chain, verify_peer = args.values_at(:private_key_file, :cert_chain_file, :verify_peer)
[priv_key, cert_chain].each do |file|
next if file.nil? or file.empty?
raise FileNotFoundException,
"Could not find #{file} for start_tls" unless File.exists? file
end
EventMachine::set_tls_parms(@signature, priv_key || '', cert_chain || '', verify_peer)
EventMachine::start_tls @signature
end
EventMachine::set_tls_parms
is part of the C++ extension and is defined in eventmachine:ext/rubymain.cpp
as the five argument C function t_set_tls_parms
rb_define_module_function (EmModule, "set_tls_parms", (VALUE(*)(...))t_set_tls_parms, 4);
And t_set_tls_parms
defined elsewhere in the same file just passes the ssl options on to evma_set_tls_parms
.
static VALUE t_set_tls_parms (VALUE self, VALUE signature, VALUE privkeyfile, VALUE certchainfile, VALUE verify_peer)
{
/* set_tls_parms takes a series of positional arguments for specifying such things
* as private keys and certificate chains.
* It's expected that the parameter list will grow as we add more supported features.
* ALL of these parameters are optional, and can be specified as empty or NULL strings.
*/
evma_set_tls_parms (NUM2ULONG (signature), StringValuePtr (privkeyfile), StringValuePtr (certchainfile), (verify_peer == Qtrue ? 1 : 0));
return Qnil;
}
The vanilla C function evma_set_tls_parms
is defined in eventmachine:ext/cmain.cpp
. It passes the ssl options on to EventableDescriptor
's SetTlsParms
method:
extern "C" void evma_set_tls_parms (const unsigned long binding, const char *privatekey_filename, const char *certchain_filename, int verify_peer)
{
ensure_eventmachine("evma_set_tls_parms");
EventableDescriptor *ed = dynamic_cast <EventableDescriptor*> (Bindable_t::GetObject (binding));
if (ed)
ed->SetTlsParms (privatekey_filename, certchain_filename, (verify_peer == 1 ? true : false));
}
That SetTlsParms
instance method is defined in eventmachine:ed.cpp
, and all it really does is cache the ssl options in some instance variables.
void ConnectionDescriptor::SetTlsParms (const char *privkey_filename, const char *certchain_filename, bool verify_peer)
{
#ifdef WITH_SSL
if (SslBox)
throw std::runtime_error ("call SetTlsParms before calling StartTls");
if (privkey_filename && *privkey_filename)
PrivateKeyFilename = privkey_filename;
if (certchain_filename && *certchain_filename)
CertChainFilename = certchain_filename;
bSslVerifyPeer = verify_peer;
#endif
#ifdef WITHOUT_SSL
throw std::runtime_error ("Encryption not available on this event-machine");
#endif
}
Those instance variables are used later in the StartTls
instance method (defined in the same file), and passed on to initialize a new SslBox_t
void ConnectionDescriptor::StartTls()
{
#ifdef WITH_SSL
if (SslBox)
throw std::runtime_error ("SSL/TLS already running on connection");
SslBox = new SslBox_t (bIsServer, PrivateKeyFilename, CertChainFilename, bSslVerifyPeer, GetBinding());
_DispatchCiphertext();
#endif
The SslBox_t
constructor is defined in eventmachine:ext/ssl.cpp
, where it uses the ssl options to initialize a new SslContext_t
.
SslBox_t::SslBox_t (bool is_server, const string &privkeyfile, const string &certchainfile, bool verify_peer, const unsigned long binding):
bIsServer (is_server),
bHandshakeCompleted (false),
bVerifyPeer (verify_peer),
pSSL (NULL),
pbioRead (NULL),
pbioWrite (NULL)
{
/* TODO someday: make it possible to re-use SSL contexts so we don't have to create
* a new one every time we come here.
*/
Context = new SslContext_t (bIsServer, privkeyfile, certchainfile);
assert (Context);
The SslContext_t
constructor is defined in the same file where it uses those options with the standard OpenSSL C bindings:
// The SSL_CTX calls here do NOT allocate memory.
int e;
if (privkeyfile.length() > 0)
e = SSL_CTX_use_PrivateKey_file (pCtx, privkeyfile.c_str(), SSL_FILETYPE_PEM);
else
e = SSL_CTX_use_PrivateKey (pCtx, DefaultPrivateKey);
if (e <= 0) ERR_print_errors_fp(stderr);
assert (e > 0);
if (certchainfile.length() > 0)
e = SSL_CTX_use_certificate_chain_file (pCtx, certchainfile.c_str());
else
e = SSL_CTX_use_certificate (pCtx, DefaultCertificate);
if (e <= 0) ERR_print_errors_fp(stderr);
assert (e > 0);
So now we know how the ssl options are used. If the call chain were modified to pass a CA file name along with the rest down to this point, say as const string &certauthfile
, we could use just a couple more OpenSSL calls to add the authority file:
if (certauthfile.length() > 0)
e = SSL_CTX_load_verify_locations(pCtx, certauthfile.c_str(), NULL);
else
;// no default necessary
if (e <= 0) ERR_print_errors_fp(stderr);
assert (e > 0);
Submitting a patch to do this is left as an exercise for the sufficiently motivated.