BearSSLHelpers.h

/*
  WiFiClientBearSSL- SSL client/server for esp8266 using BearSSL libraries
  - Mostly compatible with Arduino WiFi shield library and standard
    WiFiClient/ServerSecure (except for certificate handling).

  Copyright (c) 2018 Earle F. Philhower, III

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#ifndef _BEARSSLHELPERS_H
#define _BEARSSLHELPERS_H

#include <bearssl/bearssl.h>
#include <StackThunk.h>
#include <Updater.h>

// Internal opaque structures, not needed by user applications
namespace brssl {
  class public_key;
  class private_key;
};

namespace BearSSL {

// Holds either a single public RSA or EC key for use when BearSSL wants a pubkey.
// Copies all associated data so no need to keep input PEM/DER keys.
// All inputs can be either in RAM or PROGMEM.
class PublicKey {
  public:
    PublicKey();
    PublicKey(const char *pemKey);
    PublicKey(const uint8_t *derKey, size_t derLen);
    ~PublicKey();

    bool parse(const char *pemKey);
    bool parse(const uint8_t *derKey, size_t derLen);

    // Accessors for internal use, not needed by apps
    bool isRSA() const;
    bool isEC() const;
    const br_rsa_public_key *getRSA() const;
    const br_ec_public_key *getEC() const;

    // Disable the copy constructor, we're pointer based
    PublicKey(const PublicKey& that) = delete;

  private:
    brssl::public_key *_key;
};

// Holds either a single private RSA or EC key for use when BearSSL wants a secretkey.
// Copies all associated data so no need to keep input PEM/DER keys.
// All inputs can be either in RAM or PROGMEM.
class PrivateKey {
  public:
    PrivateKey();
    PrivateKey(const char *pemKey);
    PrivateKey(const uint8_t *derKey, size_t derLen);
    ~PrivateKey();

    bool parse(const char *pemKey);
    bool parse(const uint8_t *derKey, size_t derLen);

    // Accessors for internal use, not needed by apps
    bool isRSA() const;
    bool isEC() const;
    const br_rsa_private_key *getRSA() const;
    const br_ec_private_key *getEC() const;

    // Disable the copy constructor, we're pointer based
    PrivateKey(const PrivateKey& that) = delete;

  private:
    brssl::private_key *_key;
};

// Holds one or more X.509 certificates and associated trust anchors for
// use whenever BearSSL needs a cert or TA.  May want to have multiple
// certs for things like a series of trusted CAs (but check the CertStore class
// for a more memory efficient way).
// Copies all associated data so no need to keep input PEM/DER certs.
// All inputs can be either in RAM or PROGMEM.
class X509List {
  public:
    X509List();
    X509List(const char *pemCert);
    X509List(const uint8_t *derCert, size_t derLen);
    ~X509List();

    bool append(const char *pemCert);
    bool append(const uint8_t *derCert, size_t derLen);

    // Accessors
    size_t getCount() const {
      return _count;
    }
    const br_x509_certificate *getX509Certs() const {
      return _cert;
    }
    const br_x509_trust_anchor *getTrustAnchors() const {
      return _ta;
    }

    // Disable the copy constructor, we're pointer based
    X509List(const X509List& that) = delete;

  private:
    size_t _count;
    br_x509_certificate *_cert;
    br_x509_trust_anchor *_ta;
};

// Opaque object which wraps the BearSSL SSL session to make repeated connections
// significantly faster.  Completely optional.
class WiFiClientSecure;

class Session {
  friend class WiFiClientSecure;

  public:
    Session() { memset(&_session, 0, sizeof(_session)); }
  private:
    br_ssl_session_parameters *getSession() { return &_session; }
    // The actual BearSSL ession information
    br_ssl_session_parameters _session;
};

// Updater SHA256 hash and signature verification
class HashSHA256 : public UpdaterHashClass {
  public:
    virtual void begin() override;
    virtual void add(const void *data, uint32_t len) override;
    virtual void end() override;
    virtual int len() override;
    virtual const void *hash() override;
    virtual const unsigned char *oid() override;
  private:
    br_sha256_context _cc;
    unsigned char _sha256[32];
};

class SigningVerifier : public UpdaterVerifyClass {
  public:
    virtual uint32_t length() override;
    virtual bool verify(UpdaterHashClass *hash, const void *signature, uint32_t signatureLen) override;

  public:
    SigningVerifier(PublicKey *pubKey) { _pubKey = pubKey; stack_thunk_add_ref(); }
    ~SigningVerifier() { stack_thunk_del_ref(); }

  private:
    PublicKey *_pubKey;
};
  
// Stack thunked versions of calls
extern "C" {
extern unsigned char *thunk_br_ssl_engine_recvapp_buf( const br_ssl_engine_context *cc, size_t *len);
extern void thunk_br_ssl_engine_recvapp_ack(br_ssl_engine_context *cc, size_t len);
extern unsigned char *thunk_br_ssl_engine_recvrec_buf( const br_ssl_engine_context *cc, size_t *len);
extern void thunk_br_ssl_engine_recvrec_ack(br_ssl_engine_context *cc, size_t len);
extern unsigned char *thunk_br_ssl_engine_sendapp_buf( const br_ssl_engine_context *cc, size_t *len);
extern void thunk_br_ssl_engine_sendapp_ack(br_ssl_engine_context *cc, size_t len);
extern unsigned char *thunk_br_ssl_engine_sendrec_buf( const br_ssl_engine_context *cc, size_t *len);
extern void thunk_br_ssl_engine_sendrec_ack(br_ssl_engine_context *cc, size_t len);
};

};

#endif