//
// Context.h
//
// Library: NetSSL_OpenSSL
// Package: SSLCore
// Module:  Context
//
// Definition of the Context class.
//
// Copyright (c) 2006-2010, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef NetSSL_Context_INCLUDED
#define NetSSL_Context_INCLUDED


#include "Poco/Net/NetSSL.h"
#include "Poco/Net/SocketDefs.h"
#include "Poco/Crypto/X509Certificate.h"
#include "Poco/Crypto/EVPPKey.h"
#include "Poco/Crypto/RSAKey.h"
#include "Poco/RefCountedObject.h"
#include "Poco/AutoPtr.h"
#include <openssl/ssl.h>
#include <cstdlib>


namespace Poco {
namespace Net {


class NetSSL_API Context: public Poco::RefCountedObject
	/// This class encapsulates context information for
	/// an SSL server or client, such as the certificate
	/// verification mode and the location of certificates
	/// and private key files, as well as the list of
	/// supported ciphers.
	///
	/// The Context class is also used to control
	/// SSL session caching on the server and client side.
	///
	/// A Note Regarding TLSv1.3 Support:
	///
	/// TLSv1.3 support requires at least OpenSSL version 1.1.1.
	/// Make sure that the TLSv1.3 cipher suites are enabled:
	///
	///   - TLS_AES_256_GCM_SHA384
	///   - TLS_CHACHA20_POLY1305_SHA256
	///   - TLS_AES_128_GCM_SHA256
	///   - TLS_AES_128_CCM_8_SHA256
	///   - TLS_AES_128_CCM_SHA256
	///
	/// The first three of the above cipher suites should be enabled
	/// by default in OpenSSL if you do not provide an explicit
	/// cipher configuration (cipherList).
{
public:
	using Ptr = Poco::AutoPtr<Context>;

	enum Usage
	{
		TLS_CLIENT_USE,     /// Context is used by a client for TLSv1 or higher. Use requireMinimumProtocol() or disableProtocols() to disable undesired older versions.
		TLS_SERVER_USE,     /// Context is used by a client for TLSv1 or higher. Use requireMinimumProtocol() or disableProtocols() to disable undesired older versions.
		CLIENT_USE, 	    /// DEPRECATED. Context is used by a client.
		SERVER_USE,         /// DEPRECATED. Context is used by a server.
		TLSV1_CLIENT_USE,   /// DEPRECATED. Context is used by a client requiring TLSv1.
		TLSV1_SERVER_USE,   /// DEPRECATED. Context is used by a server requiring TLSv1.
		TLSV1_1_CLIENT_USE, /// DEPRECATED. Context is used by a client requiring TLSv1.1 (OpenSSL 1.0.0 or newer).
		TLSV1_1_SERVER_USE, /// DEPRECATED. Context is used by a server requiring TLSv1.1 (OpenSSL 1.0.0 or newer).
		TLSV1_2_CLIENT_USE, /// DEPRECATED. Context is used by a client requiring TLSv1.2 (OpenSSL 1.0.1 or newer).
		TLSV1_2_SERVER_USE, /// DEPRECATED. Context is used by a server requiring TLSv1.2 (OpenSSL 1.0.1 or newer).
		TLSV1_3_CLIENT_USE, /// DEPRECATED. Context is used by a client requiring TLSv1.3 (OpenSSL 1.1.1 or newer).
		TLSV1_3_SERVER_USE  /// DEPRECATED. Context is used by a server requiring TLSv1.3 (OpenSSL 1.1.1 or newer).
	};

	enum VerificationMode
	{
		VERIFY_NONE    = SSL_VERIFY_NONE,
			/// Server: The server will not send a client certificate
			/// request to the client, so the client will not send a certificate.
			///
			/// Client: If not using an anonymous cipher (by default disabled),
			/// the server will send a certificate which will be checked, but
			/// the result of the check will be ignored.

		VERIFY_RELAXED = SSL_VERIFY_PEER,
			/// Server: The server sends a client certificate request to the
			/// client. The certificate returned (if any) is checked.
			/// If the verification process fails, the TLS/SSL handshake is
			/// immediately terminated with an alert message containing the
			/// reason for the verification failure.
			///
			/// Client: The server certificate is verified, if one is provided.
			/// If the verification process fails, the TLS/SSL handshake is
			/// immediately terminated with an alert message containing the
			/// reason for the verification failure.

		VERIFY_STRICT  = SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
			/// Server: If the client did not return a certificate, the TLS/SSL
			/// handshake is immediately terminated with a handshake failure
			/// alert.
			///
			/// Client: Same as VERIFY_RELAXED.

		VERIFY_ONCE    = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE
			/// Server: Only request a client certificate on the initial
			/// TLS/SSL handshake. Do not ask for a client certificate
			/// again in case of a renegotiation.
			///
			/// Client: Same as VERIFY_RELAXED.
	};

	enum Protocols
	{
		PROTO_SSLV2   = 0x01,
		PROTO_SSLV3   = 0x02,
		PROTO_TLSV1   = 0x04,
		PROTO_TLSV1_1 = 0x08,
		PROTO_TLSV1_2 = 0x10,
		PROTO_TLSV1_3 = 0x20
	};

	struct NetSSL_API Params
	{
		Params();
			/// Initializes the struct with default values.

		std::string privateKeyFile;
			/// Path to the private key file used for encryption.
			/// Can be empty if no private key file is used.

		std::string certificateFile;
			/// Path to the certificate file (in PEM format).
			/// If the private key and the certificate are stored in the same file, this
			/// can be empty if privateKeyFile is given.

		std::string caLocation;
			/// Path to the file or directory containing the CA/root certificates.
			/// Can be empty if the OpenSSL builtin CA certificates
			/// are used (see loadDefaultCAs).

		VerificationMode verificationMode;
			/// Specifies whether and how peer certificates are validated.
			/// Defaults to VERIFY_RELAXED.

		int verificationDepth;
			/// Sets the upper limit for verification chain sizes. Verification
			/// will fail if a certificate chain larger than this is encountered.
			/// Defaults to 9.

		bool loadDefaultCAs;
			/// Specifies whether the builtin CA certificates from OpenSSL are used.
			/// Defaults to false.

		std::string cipherList;
			/// Specifies the supported ciphers in OpenSSL notation.
			/// Defaults to "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH".

		std::string dhParamsFile;
			/// Specifies a file containing Diffie-Hellman parameters.
			/// If empty, the default parameters are used.

		bool dhUse2048Bits;
			/// If set to true, will use 2048-bit MODP Group with 256-bit
			/// prime order subgroup (RFC5114) instead of 1024-bit for DH.

		std::string ecdhCurve;
			/// OpenSSL 1.0.1 and earlier:
			///   Specifies the name of the curve to use for ECDH, based
			///   on the curve names specified in RFC 4492.
			///   Defaults to "prime256v1".
			/// OpenSSL 1.0.2 to 1.1.0:
			///   Specifies the colon-separated list of curves
			///   to be used for ECDH, based on the curve names
			///   defined by OpenSSL, such as
			///   "X448:X25519:P-521:P-384:P-256"
			///   Defaults to the subset supported by the OpenSSL version
			///   among the above.
			/// OpenSSL 1.1.1 and above:
			///   Specifies the colon-separated list of groups
			///   (some of which can be curves) to be used for ECDH
			///   and other TLSv1.3 ephemeral key negotiation, based
			///   on the group names defined by OpenSSL. Defaults to
			///   "X448:X25519:ffdhe4096:ffdhe3072:ffdhe2048:ffdhe6144:ffdhe8192:P-521:P-384:P-256"
	};

	Context(Usage usage, const Params& params);
		/// Creates a Context using the given parameters.
		///
		///   * usage specifies whether the context is used by a client or server.
		///   * params specifies the context parameters.

	Context(
		Usage usage,
		const std::string& privateKeyFile,
		const std::string& certificateFile,
		const std::string& caLocation,
		VerificationMode verificationMode = VERIFY_RELAXED,
		int verificationDepth = 9,
		bool loadDefaultCAs = false,
		const std::string& cipherList = "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH");
		/// Creates a Context.
		///
		///   * usage specifies whether the context is used by a client or server.
		///   * privateKeyFile contains the path to the private key file used for encryption.
		///     Can be empty if no private key file is used.
		///   * certificateFile contains the path to the certificate file (in PEM format).
		///     If the private key and the certificate are stored in the same file, this
		///     can be empty if privateKeyFile is given.
		///   * caLocation contains the path to the file or directory containing the
		///     CA/root certificates. Can be empty if the OpenSSL builtin CA certificates
		///     are used (see loadDefaultCAs).
		///   * verificationMode specifies whether and how peer certificates are validated.
		///   * verificationDepth sets the upper limit for verification chain sizes. Verification
		///     will fail if a certificate chain larger than this is encountered.
		///   * loadDefaultCAs specifies whether the builtin CA certificates from OpenSSL are used.
		///   * cipherList specifies the supported ciphers in OpenSSL notation.
		///
		/// Note: If the private key is protected by a passphrase, a PrivateKeyPassphraseHandler
		/// must have been setup with the SSLManager, or the SSLManager's PrivateKeyPassphraseRequired
		/// event must be handled.

	Context(
		Usage usage,
		const std::string& caLocation,
		VerificationMode verificationMode = VERIFY_RELAXED,
		int verificationDepth = 9,
		bool loadDefaultCAs = false,
		const std::string& cipherList = "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH");
		/// Creates a Context.
		///
		///   * usage specifies whether the context is used by a client or server.
		///   * caLocation contains the path to the file or directory containing the
		///     CA/root certificates. Can be empty if the OpenSSL builtin CA certificates
		///     are used (see loadDefaultCAs).
		///   * verificationMode specifies whether and how peer certificates are validated.
		///   * verificationDepth sets the upper limit for verification chain sizes. Verification
		///     will fail if a certificate chain larger than this is encountered.
		///   * loadDefaultCAs specifies whether the builtin CA certificates from OpenSSL are used.
		///   * cipherList specifies the supported ciphers in OpenSSL notation.
		///
		/// Note that a private key and/or certificate must be specified with
		/// usePrivateKey()/useCertificate() before the Context can be used.

	~Context();
		/// Destroys the Context.

	void useCertificate(const Poco::Crypto::X509Certificate& certificate);
		/// Sets the certificate to be used by the Context.
		///
		/// To set-up a complete certificate chain, it might be
		/// necessary to call addChainCertificate() to specify
		/// additional certificates.
		///
		/// Note that useCertificate() must always be called before
		/// usePrivateKey().

	void addChainCertificate(const Poco::Crypto::X509Certificate& certificate);
		/// Adds a certificate for certificate chain validation.

	void addCertificateAuthority(const Poco::Crypto::X509Certificate& certificate);
		/// Add one trusted certification authority to be used by the Context.

	void usePrivateKey(const Poco::Crypto::RSAKey& key);
		/// Sets the private key to be used by the Context.
		///
		/// Note that useCertificate() must always be called before
		/// usePrivateKey().
		///
		/// Note: If the private key is protected by a passphrase, a PrivateKeyPassphraseHandler
		/// must have been setup with the SSLManager, or the SSLManager's PrivateKeyPassphraseRequired
		/// event must be handled.

	void usePrivateKey(const Poco::Crypto::EVPPKey &pkey);
		/// Sets the private key to be used by the Context.
		///
		/// Note that useCertificate() must always be called before
		/// usePrivateKey().
		///
		/// Note: If the private key is protected by a passphrase, a PrivateKeyPassphraseHandler
		/// must have been setup with the SSLManager, or the SSLManager's PrivateKeyPassphraseRequired
		/// event must be handled.

	SSL_CTX* sslContext() const;
		/// Returns the underlying OpenSSL SSL Context object.

	Usage usage() const;
		/// Returns whether the context is for use by a client or by a server
		/// and whether TLSv1 is required.

	bool isForServerUse() const;
		/// Returns true iff the context is for use by a server.

	Context::VerificationMode verificationMode() const;
		/// Returns the verification mode.

	void enableSessionCache(bool flag = true);
		/// Enable or disable SSL/TLS session caching.
		/// For session caching to work, it must be enabled
		/// on the server, as well as on the client side.
		///
		/// The default is disabled session caching.
		///
		/// To enable session caching on the server side, use the
		/// two-argument version of this method to specify
		/// a session ID context.

	void enableSessionCache(bool flag, const std::string& sessionIdContext);
		/// Enables or disables SSL/TLS session caching on the server.
		/// For session caching to work, it must be enabled
		/// on the server, as well as on the client side.
		///
		/// SessionIdContext contains the application's unique
		/// session ID context, which becomes part of each
		/// session identifier generated by the server within this
		/// context. SessionIdContext can be an arbitrary sequence
		/// of bytes with a maximum length of SSL_MAX_SSL_SESSION_ID_LENGTH.
		///
		/// A non-empty sessionIdContext should be specified even if
		/// session caching is disabled to avoid problems with clients
		/// requesting to reuse a session (e.g. Firefox 3.6).
		///
		/// This method may only be called on SERVER_USE Context objects.

	bool sessionCacheEnabled() const;
		/// Returns true iff the session cache is enabled.

	void setSessionCacheSize(std::size_t size);
		/// Sets the maximum size of the server session cache, in number of
		/// sessions. The default size (according to OpenSSL documentation)
		/// is 1024*20, which may be too large for many applications,
		/// especially on embedded platforms with limited memory.
		///
		/// Specifying a size of 0 will set an unlimited cache size.
		///
		/// This method may only be called on SERVER_USE Context objects.

	std::size_t getSessionCacheSize() const;
		/// Returns the current maximum size of the server session cache.
		///
		/// This method may only be called on SERVER_USE Context objects.

	void setSessionTimeout(long seconds);
		/// Sets the timeout (in seconds) of cached sessions on the server.
		/// A cached session will be removed from the cache if it has
		/// not been used for the given number of seconds.
		///
		/// This method may only be called on SERVER_USE Context objects.

	long getSessionTimeout() const;
		/// Returns the timeout (in seconds) of cached sessions on the server.
		///
		/// This method may only be called on SERVER_USE Context objects.

	void flushSessionCache();
		/// Flushes the SSL session cache on the server.
		///
		/// This method may only be called on SERVER_USE Context objects.

	void enableExtendedCertificateVerification(bool flag = true);
		/// Enable or disable the automatic post-connection
		/// extended certificate verification.
		///
		/// See X509Certificate::verify() for more information.

	bool extendedCertificateVerificationEnabled() const;
		/// Returns true iff automatic extended certificate
		/// verification is enabled.

	void disableStatelessSessionResumption();
		/// Newer versions of OpenSSL support RFC 4507 tickets for stateless
		/// session resumption.
		///
		/// The feature can be disabled by calling this method.

	void disableProtocols(int protocols);
		/// Disables the given protocols.
		///
		/// The protocols to be disabled are specified by OR-ing
		/// values from the Protocols enumeration, e.g.:
		///
		///   context.disableProtocols(PROTO_SSLV2 | PROTO_SSLV3);

	void requireMinimumProtocol(Protocols protocol);
		/// Disables all protocol version lower than the given one.
		/// To require at least TLS 1.2 or later:
		///
		///   context.requireMinimumProtocol(PROTO_TLSV1_2);

	void preferServerCiphers();
		/// When choosing a cipher, use the server's preferences instead of the client
		/// preferences. When not called, the SSL server will always follow the clients
		/// preferences. When called, the SSL/TLS server will choose following its own
		/// preferences.

private:
	void init(const Params& params);
		/// Initializes the Context with the given parameters.

	void initDH(bool use2048Bits, const std::string& dhFile);
		/// Initializes the Context with Diffie-Hellman parameters.

	void initECDH(const std::string& curve);
		/// Initializes the Context with Elliptic-Curve Diffie-Hellman key
		/// exchange curve parameters.

	void createSSLContext();
		/// Create a SSL_CTX object according to Context configuration.

	Usage _usage;
	VerificationMode _mode;
	SSL_CTX* _pSSLContext;
	bool _extendedCertificateVerification;
};


//
// inlines
//
inline Context::Usage Context::usage() const
{
	return _usage;
}


inline bool Context::isForServerUse() const
{
	return _usage == SERVER_USE
		|| _usage == TLS_SERVER_USE
		|| _usage == TLSV1_SERVER_USE
		|| _usage == TLSV1_1_SERVER_USE
		|| _usage == TLSV1_2_SERVER_USE
		|| _usage == TLSV1_3_SERVER_USE;
}


inline Context::VerificationMode Context::verificationMode() const
{
	return _mode;
}


inline SSL_CTX* Context::sslContext() const
{
	return _pSSLContext;
}


inline bool Context::extendedCertificateVerificationEnabled() const
{
	return _extendedCertificateVerification;
}


} } // namespace Poco::Net


#endif // NetSSL_Context_INCLUDED