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163 lines
4.9 KiB
163 lines
4.9 KiB
// EncodedMsg.cpp -- Encoded Message implementation
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// (c) Copyright Schlumberger Technology Corp., unpublished work, created
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// 1999. This computer program includes Confidential, Proprietary
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// Information and is a Trade Secret of Schlumberger Technology Corp. All
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// use, disclosure, and/or reproduction is prohibited unless authorized
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// in writing. All Rights Reserved.
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#include "NoWarning.h"
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#include "ForceLib.h"
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#include <scuOsExc.h>
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#include "EncodedMsg.h"
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/////////////////////////// HELPER /////////////////////////////////
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namespace
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{
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typedef Blob::value_type Marker;
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enum
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{
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mSeparator = '\x00',
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mPrivatePad = '\xff'
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};
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enum
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{
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// Require three markers: one block type + two separators
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cRequiredMarkersLength = 3 * sizeof Marker
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};
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enum
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{
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mAlternatePrivateBlockType = '\x00',
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mPrivateBlockType = '\x01',
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mPublicBlockType = '\x02'
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};
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enum
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{
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cMinimumPadding = 8
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};
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Blob::size_type
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PadLength(Blob::size_type cMessageLength,
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Blob::size_type cIntendedEncodingLength)
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{
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// Require three markers: one block type + two separators
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Blob::size_type cLength = cIntendedEncodingLength;
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// Calculate pad length, guarding against underflow.
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if (cLength < cMessageLength)
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return 0;
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cLength -= cMessageLength;
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if (cLength < cRequiredMarkersLength)
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return 0;
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cLength -= cRequiredMarkersLength;
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return cLength;
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}
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}
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/////////////////////////// PUBLIC /////////////////////////////////
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// Types
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// C'tors/D'tors
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EncodedMessage::EncodedMessage(Blob const &rMessage,
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RsaKey::Type ktOperation,
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Blob::size_type cIntendedEncodingLength)
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: m_blob()
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{
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// Precondition:
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// if (!RsaKey::IsValidModulusLength(cIntendedEncodingLength))
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// throw scu::OsException(ERROR_INTERNAL_ERROR);
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// Precondition: Message must be small enough to encode
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if (!IsMessageLengthValid(rMessage.length(), cIntendedEncodingLength))
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throw scu::OsException(ERROR_INTERNAL_ERROR);
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m_blob.reserve(cIntendedEncodingLength);
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// Ensure the encoded message when converted to an integer is
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// less than the modulus by leading with a separator
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m_blob += mSeparator;
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Marker const mBlockType = (ktOperation == RsaKey::ktPrivate) ?
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mPrivateBlockType : mPublicBlockType;
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m_blob += mBlockType;
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Blob::size_type cPadLength = PadLength(rMessage.length(),
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cIntendedEncodingLength);
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Pad(ktOperation, cPadLength);
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// Mark beginning of message
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m_blob += mSeparator;
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m_blob += rMessage;
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}
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EncodedMessage::~EncodedMessage()
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{}
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// Operators
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// Operations
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// Access
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Blob
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EncodedMessage::Value() const
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{
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return m_blob;
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}
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// Predicates
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bool
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EncodedMessage::IsMessageLengthValid(Blob::size_type cMessageLength,
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Blob::size_type cIntendedEncodingLength)
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{
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return PadLength(cMessageLength, cIntendedEncodingLength) >=
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cMinimumPadding;
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}
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// Static Variables
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/////////////////////////// PROTECTED /////////////////////////////////
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// C'tors/D'tors
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// Operators
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// Operations
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// Access
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// Predicates
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// Static Variables
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/////////////////////////// PRIVATE /////////////////////////////////
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// Types
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// C'tors/D'tors
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// Operators
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// Operations
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void
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EncodedMessage::Pad(RsaKey::Type ktOperation,
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Blob::size_type cRequiredPadLength)
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{
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if (RsaKey::ktPrivate == ktOperation)
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m_blob.append(cRequiredPadLength, mPrivatePad);
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else // TO DO: Support random pad
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throw scu::OsException(NTE_FAIL);
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}
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// Access
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// Predicates
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// Static Variables
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