bdlde_md5.h

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/// @file bdlde_md5.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlde_md5.h                                                        -*-C++-*-
#ifndef INCLUDED_BDLDE_MD5
#define INCLUDED_BDLDE_MD5
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlde_md5 bdlde_md5
/// @brief  Provide a value-semantic type encoding a message in an MD5 digest.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlde
/// @{
/// @addtogroup bdlde_md5
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlde_md5-purpose"> Purpose</a>
/// * <a href="#bdlde_md5-classes"> Classes </a>
/// * <a href="#bdlde_md5-description"> Description </a>
///   * <a href="#bdlde_md5-security"> Security </a>
///   * <a href="#bdlde_md5-performance"> Performance </a>
///   * <a href="#bdlde_md5-usage"> Usage </a>
///     * <a href="#bdlde_md5-example-1-basic-usage"> Example 1: Basic Usage </a>
///   * <a href="#bdlde_md5-additional-copyright-notice"> Additional Copyright Notice </a>
///
/// # Purpose {#bdlde_md5-purpose}
/// Provide a value-semantic type encoding a message in an MD5 digest.
///
/// # Classes {#bdlde_md5-classes}
///
/// -  bdlde::Md5: value-semantic type representing an MD5 digest
///
/// @see  bdlde_crc32
///
/// # Description {#bdlde_md5-description}
/// This component implements a mechanism for computing, updating,
/// and streaming an MD5 digest (a hash comprising 128 bits).  One possible
/// application is determining whether or not a message was received without
/// errors, although due to security vulnerabilities, it should no longer be
/// used for this purpose (see the Security section below).  This implementation
/// is based on the RFC 1321 specification which can be found at:
/// @code
/// http://www.ietf.org/rfc/rfc1321.txt
/// @endcode
/// Note that an MD5 digest does not aid in error correction.
///
/// ## Security {#bdlde_md5-security}
///
///
/// Practical collision and chosen-prefix collision attacks are known against
/// MD5.  Do not use MD5 to generate digital signatures under any circumstances,
/// and do not use MD5 at all except when it is required for interoperation with
/// legacy systems that use MD5.  SHA-2 (available in the @ref bdlde_sha2 
/// component) and SHA-3 are more secure alternatives to MD5.
///
/// You might think that your application doesn't require collision resistance.
/// However, (1) you might be mistaken, (2) once you start using MD5, you
/// prevent future versions of your application from being able to rely on
/// collision resistance unless they break backward compatibility, (3) a
/// maintainer of your application might accidentally make a change that
/// implicitly assumes collision resistance, and (4) if you expose MD5 hashes to
/// your users, they might assume that they are secure digital signatures, which
/// will make their applications insecure.  In light of the foregoing
/// considerations, and the availability of SHA-2 and SHA-3 as alternatives,
/// there is no justification for using MD5 unless you absolutely have to.
///
/// ## Performance {#bdlde_md5-performance}
///
///
/// The performance of this component is slightly slower than the native
/// `openssl` implementation of MD5.  It is typically within 7% of the speed of
/// the native `openssl` implementation with an error margin of +/-2%, depending
/// on machine load.  A million iterations of the `update` method will typically
/// take between 0.84s to 0.90s on Sun and 0.68s to 0.69s on IBM.  A million
/// iterations of the equivalent function in `openssl`, `MD5_Update`, will
/// typically take between 0.80s to 0.85s on Sun and 0.65s to 0.67s on IBM.
///
/// ## Usage {#bdlde_md5-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Basic Usage {#bdlde_md5-example-1-basic-usage}
///
///
/// The following snippets of code illustrate a typical use of the `bdlde::Md5`
/// class.  Each function would typically execute in separate processes or
/// potentially on separate machines.  The `senderExample` function below
/// demonstrates how a message sender can write a message and its MD5 digest
/// to a `bdex` output stream.  Note that `Out` may be a `typedef` of any class
/// that implements the `bslx::OutStream` protocol:
/// @code
/// /// Write a message and its MD5 digest to the specified `output`
/// /// stream.
/// void senderExample(Out& output)
/// {
///     // Prepare a message.
///     bsl::string message = "This is a test message.";
///
///     // Generate a digest for `message`.
///     bdlde::Md5 digest(message.data(), static_cast<int>(message.length()));
///
///     // Write the message to `output`.
///     output << message;
///
///     // Write the digest to `output`.
///     const int VERSION = 1;
///     digest.bdexStreamOut(output, VERSION);
/// }
/// @endcode
/// The `receiverExample` function below illustrates how a message receiver can
/// read a message and its MD5 digest from a `bdex` input stream, then perform a
/// local MD5 computation to verify that the message was received intact.  Note
/// that `In` may be a `typedef` of any class that implements the
/// `bslx::InStream` protocol:
/// @code
/// /// Read a message and its MD5 digest from the specified `input` stream,
/// /// and verify the integrity of the message.
/// void receiverExample(In& input)
/// {
///     // Read the message from `input`.
///     bsl::string message;
///     input >> message;
///
///     // Read the digest from `input`.
///     bdlde::Md5 digest;
///     const int VERSION = 1;
///     digest.bdexStreamIn(input, VERSION);
///
///     // Locally compute the digest of the received `message`.
///     bdlde::Md5 digestLocal;
///     digestLocal.update(message.data(), static_cast<int>(message.length()));
///
///     // Verify that the received and locally-computed digests match.
///     assert(digestLocal == digest);
/// }
/// @endcode
/// Due to security vulnerabilities in the MD5 algorithm (see the Security
/// section above), the use of MD5 contemplated above is insecure unless the
/// transmission channel is *completely trusted*, which is often impossible to
/// guarantee in practice.  Therefore, MD5 should no longer be used in this way.
///
/// ## Additional Copyright Notice {#bdlde_md5-additional-copyright-notice}
///
///
/// The implementation of this component is *substantially* derived from the RSA
/// Data Security, Inc. MD5 Message-Digest Algorithm that was published in the
/// aforementioned RFC 1321.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlde
 * @{
 */
/** @addtogroup bdlde_md5
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bsls_alignedbuffer.h>
#include <bsls_compilerfeatures.h>
#include <bsls_types.h>
 
#include <bsl_cstring.h>
#include <bsl_iosfwd.h>
 
 
namespace bdlde {
 
                                 // =========
                                 // class Md5
                                 // =========
 
/// This `class` represents an MD5 digest that can be updated as additional
/// data is provided.
///
/// More generally, this class supports a complete set of *value*
/// *semantic* operations, including copy construction, assignment,
/// equality comparison, `ostream` printing, and `bdex` serialization.
/// (A precise operational definition of when two instances have the same
/// value can be found in the description of `operator==` for the class.)
/// This container is *exception* *neutral* with no guarantee of rollback:
/// if an exception is thrown during the invocation of a method on a
/// pre-existing instance, the class is left in a valid state, but its
/// value is undefined.  In no event is memory leaked.  Finally, *aliasing*
/// (e.g., using all or part of an object as both source and destination)
/// is supported in all cases.
///
/// See @ref bdlde_md5 
class Md5 {
 
    // DATA
    unsigned int       d_state[4];    // state array storing the digest
 
    bsls::Types::Int64 d_length;      // length of the message
 
    unsigned char      d_buffer[64];  // buffer for storing remaining part of
                                      // message that is not yet incorporated
                                      // into `d_state`
 
    // FRIENDS
    friend bool operator==(const Md5&, const Md5&);
 
  public:
    // TYPES
 
    /// A maximally-aligned, 16-byte object type used to represent an MD5
    /// digest.
    typedef bsls::AlignedBuffer<16> Md5Digest;
 
    // CLASS METHODS
 
    /// Return the maximum valid BDEX format version, as indicated by the
    /// specified `versionSelector`, to be passed to the `bdexStreamOut` method.  
    /// 
    /// \note Note that   the `versionSelector` is expected to be formatted
    /// as `yyyymmdd`, a date representation.  See the `bslx` package-level
    /// documentation for more information on BDEX streaming of
    /// value-semantic types and containers.
    static int maxSupportedBdexVersion(int);
 
    // CREATORS
 
    /// Construct an MD5 digest having the value corresponding to no data
    /// having been provided.
    Md5();
 
    /// Construct an MD5 digest corresponding to the specified `data` having the specified `length` (in bytes).  
    /// 
    /// \pre The behavior is undefined   unless `0 <= length`.  
    /// 
    /// \note Note that   if `data` is 0, then `length` also must
    /// be 0.
    Md5(const void *data, int length);
 
    /// Construct an MD5 digest having the value of the specified `original`
    /// digest.
    Md5(const Md5& original);
 
    /// Destroy this MD5 digest.
    ~Md5();
 
    // MANIPULATORS
 
#if defined(BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS)
    /// Assign to this MD5 digest the value of the specified `rhs` MD5
    /// digest and return a reference to this modifiable MD5 digest.
    Md5& operator=(const Md5& rhs) = default;
#endif
 
    /// Assign to this object the value read from the specified input
    /// `stream` using the specified `version` format and return a reference
    /// to the modifiable `stream`.  If `stream` is initially invalid, this
    /// operation has no effect.  If `stream` becomes invalid during this
    /// operation, this object is valid, but its value is undefined.  If the
    /// specified `version` is not supported, `stream` is marked invalid, but this object is unaltered.  
    /// 
    /// \note Note that   no version is read from
    /// `stream`.  (See the package-group-level documentation for more
    /// information on `bdex` streaming of container types.)
    template <class STREAM>
    STREAM& bdexStreamIn(STREAM& stream, int version);
 
    /// Reset the value of this MD5 digest to the value provided by the
    /// default constructor.
    void reset();
 
    /// Update the value of this MD5 digest to incorporate the specified
    /// `data` having the specified `length` in bytes.  If the current state
    /// is the default state, the resultant value of this MD5 digest is the
    /// application of the MD5 algorithm upon the currently given `data` of
    /// the given `length`.  If this digest has been previously provided
    /// data and has not been subsequently reset, the current state is not
    /// the default state and the resultant value is equivalent to applying
    /// the MD5 algorithm upon the concatenation of all the provided data. 
    /// 
    /// \pre The behavior is undefined   unless `0 <= length`.  
    /// \note Note that  if `data`
    /// is 0, then `length` also must be 0.
    void update(const void *data, int length);
 
    /// Load the current value of this MD5 digest into the specified
    /// `result` and set the value of this MD5 digest to the value provided
    /// by the default constructor.
    void loadDigestAndReset(Md5Digest *result);
 
    // ACCESSORS
 
    /// Write this value to the specified output `stream` and return a
    /// reference to the modifiable `stream`.  Optionally specify an
    /// explicit `version` format; by default, the maximum supported version
    /// is written to `stream` and used as the format.  If `version` is
    /// specified, that format is used, but *not* written to `stream`.  If
    /// `version` is not supported, `stream` is left unmodified.  (See the
    /// package-group-level documentation for more information on `bdex`
    /// streaming of container types).
    template <class STREAM>
    STREAM& bdexStreamOut(STREAM& stream, int version) const;
 
    /// Format the current value of this MD5 digest to the specified output
    /// `stream` and return a reference to the modifiable `stream`.
    bsl::ostream& print(bsl::ostream& stream) const;
 
    /// Load the current value of this MD5 digest into the specified
    /// `result`.
    void loadDigest(Md5Digest *result) const;
 
#ifndef BDE_OMIT_DEPRECATED
    // CLASS METHODS
 
    /// Return the most current `bdex` streaming version number supported by
    /// this class.  (See the package-group-level documentation for more
    /// information on `bdex` streaming of container types.)
    static int maxSupportedBdexVersion();
#endif
};
 
// FREE OPERATORS
 
/// Return `true` if the specified `lhs` and `rhs` MD5 digests have the same
/// value, and `false` otherwise.  Two digests have the same value if the
/// values obtained from their respective `loadDigest` methods are identical.
bool operator==(const Md5& lhs, const Md5& rhs);
 
/// Return `true` if the specified `lhs` and `rhs` MD5 digests do not have
/// the same value, and `false` otherwise.  Two digests do not have the same
/// value if the values obtained from their respective `loadDigest` methods
/// differ.
inline
bool operator!=(const Md5& lhs, const Md5& rhs);
 
/// Write to the specified output `stream` the specified MD5 `digest` and
/// return a reference to the modifiable `stream`.
inline
bsl::ostream& operator<<(bsl::ostream& stream, const Md5& digest);
 
// ============================================================================
//                        INLINE FUNCTION DEFINITIONS
// ============================================================================
 
                                 // ---------
                                 // class Md5
                                 // ---------
 
// CLASS METHODS
inline
int Md5::maxSupportedBdexVersion(int)
{
    return 1;
}
 
// MANIPULATORS
template <class STREAM>
STREAM& Md5::bdexStreamIn(STREAM& stream, int version)
{
    switch (version) {
      case 1: {
        unsigned int       state[4];
        unsigned char      buf[64];
        bsls::Types::Int64 length;
 
        // first the state
 
        for (int i = 0; i < 4; i++) {
            stream.getUint32(state[i]);
        }
 
        // then the length
 
        stream.getInt64(length);
 
        // finally the buffer
 
        for (int i = 0; i < 64; i++) {
            stream.getUint8(buf[i]);
        }
 
        if (!stream) {
            return stream;                                            // RETURN
        }
 
        d_length = length;
        bsl::memcpy(d_state, state, sizeof state);
        bsl::memcpy(d_buffer, buf, sizeof buf);
 
      } break;
      default: {
        stream.invalidate();
      } break;
    }
    return stream;
}
 
// ACCESSORS
template <class STREAM>
STREAM& Md5::bdexStreamOut(STREAM& stream, int version) const
{
    if (stream) {
        switch (version) {
          case 1: {
            // first the state
 
            for (int i = 0; i < 4; ++i) {
                stream.putUint32(d_state[i]);
            }
 
            // then the length
 
            stream.putInt64(d_length);
 
            // finally the buffer
 
            for (int i = 0; i < 64; ++i) {
                stream.putUint8(d_buffer[i]);
            }
 
          } break;
          default: {
            stream.invalidate();
          } break;
        }
    }
    return stream;
}
 
#ifndef BDE_OMIT_DEPRECATED
inline
int Md5::maxSupportedBdexVersion()
{
    return maxSupportedBdexVersion(0);
}
#endif
 
}  // close package namespace
 
// FREE OPERATORS
inline
bool bdlde::operator!=(const Md5& lhs, const Md5& rhs)
{
    return !(lhs == rhs);
}
 
inline
bsl::ostream& bdlde::operator<<(bsl::ostream& stream, const Md5& digest)
{
    return digest.print(stream);
}
 
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2018 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */