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// Copyright (C) 2010-2024 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
#ifndef TSIGKEY_H
#define TSIGKEY_H
#include <cryptolink/cryptolink.h>
namespace isc {
namespace dns {
class Name;
/// @brief TSIG key.
///
/// This class holds a TSIG key along with some related attributes as
/// defined in RFC2845.
///
/// A TSIG key consists of the following attributes:
/// - Key name
/// - Hash algorithm
/// - Digest bits
/// - Shared secret
///
/// <b>Implementation Notes</b>
///
/// We may add more attributes in future versions. For example, if and when
/// we support the TKEY protocol (RFC2930), we may need to introduce the
/// notion of inception and expiration times.
/// At that point we may also have to introduce a class hierarchy to handle
/// different types of keys in a polymorphic way.
/// At the moment we use the straightforward value-type class with minimal
/// attributes.
///
/// In the TSIG protocol, hash algorithms are represented in the form of
/// domain name.
/// Our interfaces provide direct translation of this concept; for example,
/// the constructor from parameters take a @ref Name object to specify the
/// algorithm.
/// On one hand, this may be counter intuitive.
/// An API user would rather specify "hmac-md5" instead of
/// <code>Name("hmac-md5.sig-alg.reg.int")</code>.
/// On the other hand, it may be more convenient for some kind of applications
/// if we maintain the algorithm as the expected representation for
/// protocol operations (such as sign and very a message).
/// Considering these points, we adopt the interface closer to the protocol
/// specification for now.
/// To minimize the burden for API users, we also define a set of constants
/// for commonly used algorithm names so that the users don't have to
/// remember the actual domain names defined in the protocol specification.
/// We may also have to add conversion routines between domain names
/// and more intuitive representations (e.g. strings) for algorithms.
class TSIGKey {
public:
///
/// @brief Constructors, Assignment Operator and Destructor.
///
//@{
/// @brief Constructor from key parameters.
///
/// The algorithm_name should generally be a known algorithm to this
/// implementation, which are defined via the
/// <code>static const</code> member functions.
///
/// Other names are still accepted as long as the secret is empty
/// (secret is null and secret_len is 0), however; in some cases
/// we might want to treat just the pair of key name and algorithm name
/// opaquely, e.g., when generating a response TSIG with a BADKEY error
/// because the algorithm is unknown as specified in Section 3.2 of
/// RFC2845 (in which case the algorithm name would be copied from the
/// request to the response, and for that purpose it would be convenient
/// if a TSIGKey object can hold a name for an "unknown" algorithm).
///
/// @note RFC2845 does not specify which algorithm name should be used
/// in such a BADKEY response. The behavior of using the same algorithm
/// is derived from the BIND 9 implementation.
///
/// It is unlikely that a TSIG key with an unknown algorithm is of any
/// use with actual crypto operation, so care must be taken when dealing
/// with such keys. (The restriction for the secret will prevent
/// accidental creation of such a dangerous key, e.g., due to misspelling
/// in a configuration file).
/// If the given algorithm name is unknown and non empty secret is
/// specified, an exception of type InvalidParameter will be thrown.
///
/// secret and secret_len must be consistent in that the latter
/// is 0 if and only if the former is null;
/// otherwise an exception of type InvalidParameter will be thrown.
///
/// digestbits is the truncated length in bits or 0 which means no
/// truncation and is the default. Constraints for non-zero value
/// are in RFC 4635 section 3.1: minimum 80 or the half of the
/// full (i.e., not truncated) length, integral number of octets
/// (i.e., multiple of 8), and maximum the full length.
///
/// This constructor internally involves resource allocation, and if
/// it fails, a corresponding standard exception will be thrown.
///
/// @param key_name The name of the key as a domain name.
/// @param algorithm_name The hash algorithm used for this key in the
/// form of domain name. For example, it can be
/// TSIGKey::HMACSHA256_NAME() for HMAC-SHA256.
/// @param secret Point to a binary sequence of the shared secret to be
/// used for this key, or null if the secret is empty.
/// @param secret_len The size of the binary %data (secret) in bytes.
/// @param digestbits The number of bits to include in the digest
/// (0 means to include all).
TSIGKey(const Name& key_name, const Name& algorithm_name,
const void* secret, size_t secret_len, size_t digestbits = 0);
/// @brief Constructor from an input string
///
/// The string must be of the form:
/// name:secret[:algorithm][:digestbits]
/// Where "name" is a domain name for the key, "secret" is a
/// base64 representation of the key secret, and the optional
/// "algorithm" is an algorithm identifier as specified in RFC 4635.
/// The default algorithm is hmac-md5.sig-alg.reg.int.
/// "digestbits" is the minimum truncated length in bits.
/// The default digestbits value is 0 and means truncation is forbidden.
///
/// The same restriction about the algorithm name (and secret) as that
/// for the other constructor applies.
///
/// Since ':' is used as a separator here, it is not possible to
/// use this constructor to create keys with a ':' character in
/// their name.
///
/// @throw InvalidParameter exception if the input string is
/// invalid.
///
/// @param str The string to make a TSIGKey from
explicit TSIGKey(const std::string& str);
/// @brief The copy constructor.
///
/// It internally allocates a resource, and if it fails a corresponding
/// standard exception will be thrown.
/// This constructor never throws an exception otherwise.
TSIGKey(const TSIGKey& source);
/// @brief Assignment operator.
///
/// It internally allocates a resource, and if it fails a corresponding
/// standard exception will be thrown.
/// This operator never throws an exception otherwise.
///
/// This operator provides the strong exception guarantee: When an
/// exception is thrown the content of the assignment target will be
/// intact.
TSIGKey& operator=(const TSIGKey& source);
/// @brief The destructor.
virtual ~TSIGKey();
//@}
///
/// @brief Getter Methods
///
/// These methods never throw an exception.
//@{
/// @brief Return the key name.
const Name& getKeyName() const;
/// @brief Return the algorithm name.
const Name& getAlgorithmName() const;
/// @brief Return the hash algorithm name in the form of cryptolink::HashAlgorithm
isc::cryptolink::HashAlgorithm getAlgorithm() const;
/// @brief Return the minimum truncated length.
size_t getDigestbits() const;
/// @brief Return the length of the TSIG secret in bytes.
size_t getSecretLength() const;
/// @brief Return the value of the TSIG secret.
///
/// If it returns a non null pointer, the memory region beginning at the
/// address returned by this method is valid up to the bytes specified
/// by the return value of getSecretLength().
///
/// The memory region is only valid while the corresponding TSIGKey
/// object is valid. The caller must hold the TSIGKey object while
/// it needs to refer to the region or it must make a local copy of the
/// region.
const void* getSecret() const;
//@}
/// @brief Converts the TSIGKey to a string value
///
/// The resulting string will be of the form
/// name:secret:algorithm[:digestbits].
/// Where "name" is a domain name for the key, "secret" is a
/// base64 representation of the key secret, and "algorithm" is
/// an algorithm identifier as specified in RFC 4635.
/// When not zero, digestbits is appended.
///
/// @return The string representation of the given TSIGKey.
std::string toText() const;
/// @brief Well known algorithm names as defined in RFC2845 and RFC4635.
///
/// Note: we begin with the "mandatory" algorithms defined in RFC4635
/// as a minimal initial set.
/// We'll add others as we see the need for them.
//@{
static const Name& HMACMD5_NAME(); // HMAC-MD5 (RFC2845)
static const Name& HMACMD5_SHORT_NAME();
static const Name& HMACSHA1_NAME(); // HMAC-SHA1 (RFC4635)
static const Name& HMACSHA256_NAME(); // HMAC-SHA256 (RFC4635)
static const Name& HMACSHA224_NAME(); // HMAC-SHA256 (RFC4635)
static const Name& HMACSHA384_NAME(); // HMAC-SHA256 (RFC4635)
static const Name& HMACSHA512_NAME(); // HMAC-SHA256 (RFC4635)
static const Name& GSSTSIG_NAME(); // GSS-TSIG (RFC3645)
//@}
private:
struct TSIGKeyImpl;
boost::shared_ptr<TSIGKeyImpl> impl_;
};
/// @brief A simple repository of a set of TSIGKey objects.
///
/// This is a "key ring" to maintain TSIG keys (TSIGKey objects) and
/// provides trivial operations such as add, remove, and find.
///
/// The keys are identified by their key names.
/// So, for example, two or more keys of the same key name but of different
/// algorithms are considered to be the same, and cannot be stored in the
/// key ring at the same time.
///
/// <b>Implementation Note:</b>
/// For simplicity the initial implementation requests the application make
/// a copy of keys stored in the key ring if it needs to use the keys for
/// a long period (during which some of the keys may be removed).
/// This is based on the observations that a single server will not hold
/// a huge number of keys nor use keys in many different contexts (such as
/// in different DNS transactions).
/// If this assumption does not hold and memory consumption becomes an issue
/// we may have to revisit the design.
class TSIGKeyRing {
public:
/// Result codes of various public methods of TSIGKeyRing
enum Result {
SUCCESS = 0, // The operation is successful.
EXIST = 1, // A key is already stored in TSIGKeyRing.
NOTFOUND = 2 // The specified key is not found in TSIGKeyRing.
};
/// @brief A helper structure to represent the search result of
/// <code>TSIGKeyRing::find()</code>.
///
/// This is a straightforward pair of the result code and a pointer
/// to the found key to represent the result of find().
/// We use this in order to avoid overloading the return value for both
/// the result code ("success" or "not found") and the found object,
/// i.e., avoid using null to mean "not found", etc.
///
/// This is a simple value class with no internal state, so for
/// convenience we allow the applications to refer to the members
/// directly.
///
/// See the description of find() for the semantics of the member
/// variables.
struct FindResult {
FindResult(Result param_code, const TSIGKey* param_key) :
code(param_code), key(param_key) {
}
const Result code;
const TSIGKey* const key;
};
///
/// @brief Constructors and Destructor.
///
/// @note The copy constructor and the assignment operator are
/// intentionally defined as private, making this class non copyable.
/// There is no technical reason why this class cannot be copied,
/// but since the key ring can potentially have a large number of keys,
/// a naive copy operation may cause unexpected overhead.
/// It's generally expected for an application to share the same
/// instance of key ring and share it throughout the program via
/// references, so we prevent the copy operation explicitly to avoid
/// unexpected copy operations.
//@{
private:
TSIGKeyRing(const TSIGKeyRing& source);
TSIGKeyRing& operator=(const TSIGKeyRing& source);
public:
/// @brief The default constructor.
///
/// This constructor never throws an exception.
TSIGKeyRing();
/// @brief The destructor.
~TSIGKeyRing();
//@}
/// @brief Return the number of keys stored in the TSIGKeyRing.
///
/// This method never throws an exception.
unsigned int size() const;
/// @brief Add a TSIGKey to the TSIGKeyRing.
///
/// This method will create a local copy of the given key, so the caller
/// does not have to keep owning it.
///
/// If internal resource allocation fails, a corresponding standard
/// exception will be thrown.
/// This method never throws an exception otherwise.
///
/// @param key A TSIGKey to be added.
/// @return SUCCESS if the key is successfully added to the key ring or
/// EXIST if the key ring already stores a key whose name is identical to
/// that of key.
Result add(const TSIGKey& key);
/// Remove a TSIGKey for the given name from the TSIGKeyRing.
///
/// This method never throws an exception.
///
/// @param key_name The name of the key to be removed.
/// @return SUCCESS if the key is successfully removed from the key
/// ring or NOTFOUND if the key ring does not store the key that matches
/// key_name.
Result remove(const Name& key_name);
/// Find a TSIGKey for the given name in the TSIGKeyRing.
///
/// It searches the internal storage for a TSIGKey whose name is
/// key_name.
/// It returns the result in the form of a FindResult
/// object as follows:
/// - code: SUCCESS if a key is found; otherwise NOTFOUND.
/// - key: A pointer to the found TSIGKey object if one is found;
/// otherwise null.
///
/// The pointer returned in the FindResult object is only valid until
/// the corresponding key is removed from the key ring.
/// The caller must ensure that the key is held in the key ring while
/// it needs to refer to it, or it must make a local copy of the key.
///
/// This method never throws an exception.
///
/// @param key_name The name of the key to be found.
/// @return A FindResult object enclosing the search result (see above).
FindResult find(const Name& key_name) const;
/// Find a TSIGKey for the given name in the TSIGKeyRing.
///
/// It searches the internal storage for a TSIGKey whose name is
/// key_name and that uses the hash algorithm identified by
/// algorithm_name.
/// It returns the result in the form of a FindResult
/// object as follows:
/// - code: SUCCESS if a key is found; otherwise NOTFOUND.
/// - key: A pointer to the found TSIGKey object if one is found;
/// otherwise null.
///
/// The pointer returned in the FindResult object is only valid until
/// the corresponding key is removed from the key ring.
/// The caller must ensure that the key is held in the key ring while
/// it needs to refer to it, or it must make a local copy of the key.
///
/// This method never throws an exception.
///
/// @param key_name The name of the key to be found.
/// @param algorithm_name The name of the algorithm of the found key.
/// @return A FindResult object enclosing the search result (see above).
FindResult find(const Name& key_name, const Name& algorithm_name) const;
private:
struct TSIGKeyRingImpl;
boost::shared_ptr<TSIGKeyRingImpl> impl_;
};
}
}
#endif // TSIGKEY_H
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