epee: add SSL support

RPC connections now have optional tranparent SSL.

An optional private key and certificate file can be passed,
using the --{rpc,daemon}-ssl-private-key and
--{rpc,daemon}-ssl-certificate options. Those have as
argument a path to a PEM format private private key and
certificate, respectively.
If not given, a temporary self signed certificate will be used.

SSL can be enabled or disabled using --{rpc}-ssl, which
accepts autodetect (default), disabled or enabled.

Access can be restricted to particular certificates using the
--rpc-ssl-allowed-certificates, which takes a list of
paths to PEM encoded certificates. This can allow a wallet to
connect to only the daemon they think they're connected to,
by forcing SSL and listing the paths to the known good
certificates.

To generate long term certificates:

openssl genrsa -out /tmp/KEY 4096
openssl req -new -key /tmp/KEY -out /tmp/REQ
openssl x509 -req -days 999999 -sha256 -in /tmp/REQ -signkey /tmp/KEY -out /tmp/CERT

/tmp/KEY is the private key, and /tmp/CERT is the certificate,
both in PEM format. /tmp/REQ can be removed. Adjust the last
command to set expiration date, etc, as needed. It doesn't
make a whole lot of sense for monero anyway, since most servers
will run with one time temporary self signed certificates anyway.

SSL support is transparent, so all communication is done on the
existing ports, with SSL autodetection. This means you can start
using an SSL daemon now, but you should not enforce SSL yet or
nothing will talk to you.

1 files changed, 319 insertions, 0 deletions

diff --git a/contrib/epee/src/net_ssl.cpp b/contrib/epee/src/net_ssl.cpp
new file mode 100644
index 000000000..941799078
--- /dev/null
+++ b/contrib/epee/src/net_ssl.cpp
@@ -0,0 +1,319 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <string.h>
+#include <boost/asio/ssl.hpp>
+#include <openssl/ssl.h>
+#include <openssl/pem.h>
+#include "misc_log_ex.h"
+#include "net/net_ssl.h"
+
+#undef MONERO_DEFAULT_LOG_CATEGORY
+#define MONERO_DEFAULT_LOG_CATEGORY "net.ssl"
+
+// openssl genrsa -out /tmp/KEY 4096
+// openssl req -new -key /tmp/KEY -out /tmp/REQ
+// openssl x509 -req -days 999999 -sha256 -in /tmp/REQ -signkey /tmp/KEY -out /tmp/CERT
+
+namespace
+{
+  struct openssl_bio_free
+  {
+    void operator()(BIO* ptr) const noexcept
+    {
+      if (ptr)
+        BIO_free(ptr);
+    }
+  };
+  using openssl_bio = std::unique_ptr<BIO, openssl_bio_free>;
+
+  struct openssl_pkey_free
+  {
+    void operator()(EVP_PKEY* ptr) const noexcept
+    {
+      if (ptr)
+        EVP_PKEY_free(ptr);
+    }
+  };
+  using openssl_pkey = std::unique_ptr<EVP_PKEY, openssl_pkey_free>;
+
+}
+
+namespace epee
+{
+namespace net_utils
+{
+
+// https://stackoverflow.com/questions/256405/programmatically-create-x509-certificate-using-openssl
+bool create_ssl_certificate(EVP_PKEY *&pkey, X509 *&cert)
+{
+  MGINFO("Generating SSL certificate");
+  pkey = EVP_PKEY_new();
+  openssl_pkey pkey_deleter{pkey};
+  if (!pkey)
+  {
+    MERROR("Failed to create new private key");
+    return false;
+  }
+  RSA *rsa = RSA_generate_key(4096, RSA_F4, NULL, NULL);
+  if (!rsa)
+  {
+    MERROR("Error generating RSA private key");
+    return false;
+  }
+  if (EVP_PKEY_assign_RSA(pkey, rsa) <= 0)
+  {
+    RSA_free(rsa);
+    MERROR("Error assigning RSA private key");
+    return false;
+  }
+
+  cert = X509_new();
+  if (!cert)
+  {
+    MERROR("Failed to create new X509 certificate");
+    return false;
+  }
+  ASN1_INTEGER_set(X509_get_serialNumber(cert), 1);
+  X509_gmtime_adj(X509_get_notBefore(cert), 0);
+  X509_gmtime_adj(X509_get_notAfter(cert), 3600 * 24 * 182); // half a year
+  if (!X509_set_pubkey(cert, pkey))
+  {
+    MERROR("Error setting pubkey on certificate");
+    X509_free(cert);
+    return false;
+  }
+  X509_NAME *name = X509_get_subject_name(cert);
+  X509_set_issuer_name(cert, name);
+
+  if (X509_sign(cert, pkey, EVP_sha256()) == 0)
+  {
+    MERROR("Error signing certificate");
+    X509_free(cert);
+    return false;
+  }
+  return true;
+}
+
+bool create_ssl_certificate(std::string &pkey_buffer, std::string &cert_buffer)
+{
+  EVP_PKEY *pkey;
+  X509 *cert;
+  if (!create_ssl_certificate(pkey, cert))
+    return false;
+  BIO *bio_pkey = BIO_new(BIO_s_mem()), *bio_cert = BIO_new(BIO_s_mem());
+  openssl_bio bio_pkey_deleter{bio_pkey};
+  bool success = PEM_write_bio_PrivateKey(bio_pkey, pkey, NULL, NULL, 0, NULL, NULL) && PEM_write_bio_X509(bio_cert, cert);
+  X509_free(cert);
+  if (!success)
+  {
+    MERROR("Failed to write cert and/or pkey: " << ERR_get_error());
+    return false;
+  }
+  BUF_MEM *buf = NULL;
+  BIO_get_mem_ptr(bio_pkey, &buf);
+  if (!buf || !buf->data || !buf->length)
+  {
+    MERROR("Failed to write pkey: " << ERR_get_error());
+    return false;
+  }
+  pkey_buffer = std::string(buf->data, buf->length);
+  buf = NULL;
+  BIO_get_mem_ptr(bio_cert, &buf);
+  if (!buf || !buf->data || !buf->length)
+  {
+    MERROR("Failed to write cert: " << ERR_get_error());
+    return false;
+  }
+  cert_buffer = std::string(buf->data, buf->length);
+  return success;
+}
+
+ssl_context_t create_ssl_context(const std::pair<std::string, std::string> &private_key_and_certificate_path, std::list<std::string> allowed_certificates, bool allow_any_cert)
+{
+  ssl_context_t ssl_context({boost::asio::ssl::context(boost::asio::ssl::context::sslv23), std::move(allowed_certificates)});
+
+  // disable sslv2
+  ssl_context.context.set_options(boost::asio::ssl::context::default_workarounds | boost::asio::ssl::context::no_sslv2);
+  ssl_context.context.set_default_verify_paths();
+
+  // set options on the SSL context for added security
+  SSL_CTX *ctx = ssl_context.context.native_handle();
+  CHECK_AND_ASSERT_THROW_MES(ctx, "Failed to get SSL context");
+  SSL_CTX_clear_options(ctx, SSL_OP_LEGACY_SERVER_CONNECT); // SSL_CTX_SET_OPTIONS(3)
+  SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF); // https://stackoverflow.com/questions/22378442
+#ifdef SSL_OP_NO_TICKET
+  SSL_CTX_set_options(ctx, SSL_OP_NO_TICKET); // https://stackoverflow.com/questions/22378442
+#endif
+#ifdef SSL_OP_NO_RENEGOTIATION
+  SSL_CTX_set_options(ctx, SSL_OP_NO_RENEGOTIATION);
+#endif
+#ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
+  SSL_CTX_set_options(ctx, SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION);
+#endif
+#ifdef SSL_OP_NO_COMPRESSION
+  SSL_CTX_set_options(ctx, SSL_OP_NO_COMPRESSION);
+#endif
+  SSL_CTX_set_options(ctx, SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 | SSL_OP_NO_TLSv1 | SSL_OP_NO_TLSv1_1); // https://github.com/ssllabs/research/wiki/SSL-and-TLS-Deployment-Best-Practices
+
+  CHECK_AND_ASSERT_THROW_MES(private_key_and_certificate_path.first.empty() == private_key_and_certificate_path.second.empty(), "private key and certificate must be either both given or both empty");
+  if (private_key_and_certificate_path.second.empty())
+  {
+    std::string pkey, cert;
+    CHECK_AND_ASSERT_THROW_MES(create_ssl_certificate(pkey, cert), "Failed to create certificate");
+    ssl_context.context.use_private_key(boost::asio::buffer(pkey), boost::asio::ssl::context::pem);
+    ssl_context.context.use_certificate(boost::asio::buffer(cert), boost::asio::ssl::context::pem);
+  }
+  else
+  {
+    ssl_context.context.use_private_key_file(private_key_and_certificate_path.first, boost::asio::ssl::context::pem);
+    ssl_context.context.use_certificate_file(private_key_and_certificate_path.second, boost::asio::ssl::context::pem);
+  }
+  ssl_context.allow_any_cert = allow_any_cert;
+
+  return ssl_context;
+}
+
+void use_ssl_certificate(ssl_context_t &ssl_context, const std::pair<std::string, std::string> &private_key_and_certificate_path)
+{
+  ssl_context.context.use_private_key_file(private_key_and_certificate_path.first, boost::asio::ssl::context::pem);
+  ssl_context.context.use_certificate_file(private_key_and_certificate_path.second, boost::asio::ssl::context::pem);
+}
+
+bool is_ssl(const unsigned char *data, size_t len)
+{
+  if (len < get_ssl_magic_size())
+    return false;
+
+  // https://security.stackexchange.com/questions/34780/checking-client-hello-for-https-classification
+  MDEBUG("SSL detection buffer, " << len << " bytes: "
+    << (unsigned)(unsigned char)data[0] << " " << (unsigned)(unsigned char)data[1] << " "
+    << (unsigned)(unsigned char)data[2] << " " << (unsigned)(unsigned char)data[3] << " "
+    << (unsigned)(unsigned char)data[4] << " " << (unsigned)(unsigned char)data[5] << " "
+    << (unsigned)(unsigned char)data[6] << " " << (unsigned)(unsigned char)data[7] << " "
+    << (unsigned)(unsigned char)data[8]);
+  if (data[0] == 0x16) // record
+  if (data[1] == 3) // major version
+  if (data[5] == 1) // ClientHello
+  if (data[6] == 0 && data[3]*256 + data[4] == data[7]*256 + data[8] + 4) // length check
+    return true;
+  return false;
+}
+
+bool is_certificate_allowed(boost::asio::ssl::verify_context &ctx, const std::list<std::string> &allowed_certificates)
+{
+  X509_STORE_CTX *sctx = ctx.native_handle();
+  if (!sctx)
+  {
+    MERROR("Error getting verify_context handle");
+    return false;
+  }
+  X509 *cert =X509_STORE_CTX_get_current_cert(sctx);
+  if (!cert)
+  {
+    MERROR("No certificate found in verify_context");
+    return false;
+  }
+
+  BIO *bio_cert = BIO_new(BIO_s_mem());
+  openssl_bio bio_cert_deleter{bio_cert};
+  bool success = PEM_write_bio_X509(bio_cert, cert);
+  if (!success)
+  {
+    MERROR("Failed to print certificate");
+    return false;
+  }
+  BUF_MEM *buf = NULL;
+  BIO_get_mem_ptr(bio_cert, &buf);
+  if (!buf || !buf->data || !buf->length)
+  {
+    MERROR("Failed to write certificate: " << ERR_get_error());
+    return false;
+  }
+  std::string certificate(std::string(buf->data, buf->length));
+  return std::find(allowed_certificates.begin(), allowed_certificates.end(), certificate) != allowed_certificates.end();
+}
+
+bool ssl_handshake(boost::asio::ssl::stream<boost::asio::ip::tcp::socket> &socket, boost::asio::ssl::stream_base::handshake_type type, const epee::net_utils::ssl_context_t &ssl_context)
+{
+  bool verified = false;
+  socket.next_layer().set_option(boost::asio::ip::tcp::no_delay(true));
+  socket.set_verify_mode(boost::asio::ssl::verify_peer);
+  socket.set_verify_callback([&](bool preverified, boost::asio::ssl::verify_context &ctx)
+  {
+    if (!preverified)
+    {
+      const int err = X509_STORE_CTX_get_error(ctx.native_handle());
+      const int depth = X509_STORE_CTX_get_error_depth(ctx.native_handle());
+      if (err != X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT || depth != 0)
+      {
+        MERROR("Invalid SSL certificate, error " << err << " at depth " << depth << ", connection dropped");
+        return false;
+      }
+    }
+    if (!ssl_context.allow_any_cert && !ssl_context.allowed_certificates.empty() && !is_certificate_allowed(ctx, ssl_context.allowed_certificates))
+    {
+      MERROR("Certificate is not in the allowed list, connection droppped");
+      return false;
+    }
+    verified = true;
+    return true;
+  });
+
+  boost::system::error_code ec;
+  socket.handshake(type, ec);
+  if (ec)
+  {
+    MERROR("handshake failed, connection dropped");
+    return false;
+  }
+  if (!ssl_context.allow_any_cert && !verified)
+  {
+    MERROR("Peer did not provide a certificate in the allowed list, connection dropped");
+    return false;
+  }
+  MDEBUG("SSL handshake success");
+  return true;
+}
+
+bool ssl_support_from_string(ssl_support_t &ssl, boost::string_ref s)
+{
+  if (s == "enabled")
+    ssl = epee::net_utils::ssl_support_t::e_ssl_support_enabled;
+  else if (s == "disabled")
+    ssl = epee::net_utils::ssl_support_t::e_ssl_support_disabled;
+  else if (s == "autodetect")
+    ssl = epee::net_utils::ssl_support_t::e_ssl_support_autodetect;
+  else
+    return false;
+  return true;
+}
+
+} // namespace
+} // namespace
+