pw_tls_client_mbedtls: Add initialization logic

Define necessary data structures for MbedTLS based TLS client and
implement initialization logic.

Bug: 398
Change-Id: I07c7659d889fec2c9ae9a5f863147ffe30287057
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/51403
Commit-Queue: Yecheng Zhao <zyecheng@google.com>
Reviewed-by: David Palchak <palchak@google.com>
Reviewed-by: Ali Zhang <alizhang@google.com>

1 files changed, 43 insertions, 1 deletions

diff --git a/pw_tls_client_mbedtls/public/pw_tls_client_mbedtls/backend_types.h b/pw_tls_client_mbedtls/public/pw_tls_client_mbedtls/backend_types.h
index a080dff69..e3a2fd44b 100644
--- a/pw_tls_client_mbedtls/public/pw_tls_client_mbedtls/backend_types.h
+++ b/pw_tls_client_mbedtls/public/pw_tls_client_mbedtls/backend_types.h
@@ -14,9 +14,51 @@
 
 #pragma once
 
+#include "mbedtls/certs.h"
+#include "mbedtls/ctr_drbg.h"
+#include "mbedtls/entropy.h"
+#include "mbedtls/error.h"
+#include "mbedtls/ssl.h"
+#include "pw_status/status.h"
+#include "pw_tls_client/options.h"
+
 namespace pw::tls_client::backend {
 class SessionImplementation {
-  // TODO(pwbug/398): To implement
+ public:
+  SessionImplementation(SessionOptions options);
+  ~SessionImplementation();
+  Status Setup();
+  void SetTlsStatus(TLSStatus status) { tls_status_ = status; }
+  TLSStatus GetTlsStatus() { return tls_status_; }
+
+  // The method is for test only. When given a non-Ok status, it will override
+  // the status returned by entropy source pw::tls_client::GetRandomBytes();
+  static void SetEntropySourceStatus(Status status);
+
+ private:
+  // mbedtls entropy
+  mbedtls_entropy_context entropy_ctx_;
+  mbedtls_ctr_drbg_context drbg_ctx_;
+
+  // SSL data structure
+  mbedtls_ssl_context ssl_ctx_;
+
+  // Configuration data structure
+  mbedtls_ssl_config ssl_config_;
+
+  // A copy of the option when creating the client.
+  SessionOptions session_options_;
+
+  TLSStatus tls_status_ = TLSStatus::kOk;
+
+  static int MbedTlsWrite(void* ctx, const uint8_t* buf, size_t len);
+  static int MbedTlsRead(void* ctx, unsigned char* buf, size_t len);
+  static int MbedTlsEntropySource(void* ctx,
+                                  unsigned char* out,
+                                  size_t len,
+                                  size_t* output_length);
+
+  static Status entropy_source_status_;
 };
 
 }  // namespace pw::tls_client::backend