sha1.cpp

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/*
 *  sha1.cpp
 *
 *  Copyright (C) 1998, 2009
 *  Paul E. Jones <paulej@packetizer.com>
 *  All Rights Reserved.
 *
 *****************************************************************************
 *  $Id: sha1.cpp 12 2009-06-22 19:34:25Z paulej $
 *****************************************************************************
 *
 *  Description:
 *      This class implements the Secure Hashing Standard as defined
 *      in FIPS PUB 180-1 published April 17, 1995.
 *
 *      The Secure Hashing Standard, which uses the Secure Hashing
 *      Algorithm (SHA), produces a 160-bit message digest for a
 *      given data stream.  In theory, it is highly improbable that
 *      two messages will produce the same message digest.  Therefore,
 *      this algorithm can serve as a means of providing a "fingerprint"
 *      for a message.
 *
 *  Portability Issues:
 *      SHA-1 is defined in terms of 32-bit "words".  This code was
 *      written with the expectation that the processor has at least
 *      a 32-bit machine word size.  If the machine word size is larger,
 *      the code should still function properly.  One caveat to that
 *      is that the input functions taking characters and character arrays
 *      assume that only 8 bits of information are stored in each character.
 *
 *  Caveats:
 *      SHA-1 is designed to work with messages less than 2^64 bits long.
 *      Although SHA-1 allows a message digest to be generated for
 *      messages of any number of bits less than 2^64, this implementation
 *      only works with messages with a length that is a multiple of 8
 *      bits.
 *
 */

#include "sha1.h"

namespace fhicl {

  /*
   *  SHA1
   *
   *  Description:
   *      This is the constructor for the sha1 class.
   *
   *  Parameters:
   *      None.
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *
   */
  SHA1::SHA1() { Reset(); }

  /*
   *  Reset
   *
   *  Description:
   *      This function will initialize the sha1 class member variables
   *      in preparation for computing a new message digest.
   *
   *  Parameters:
   *      None.
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *
   */
  void
  SHA1::Reset()
  {
    Length_Low = 0;
    Length_High = 0;
    Message_Block_Index = 0;

    H[0] = 0x67452301;
    H[1] = 0xEFCDAB89;
    H[2] = 0x98BADCFE;
    H[3] = 0x10325476;
    H[4] = 0xC3D2E1F0;

    Computed = false;
    Corrupted = false;
  }

  /*
   *  Result
   *
   *  Description:
   *      This function will return the 160-bit message digest into the
   *      array provided.
   *
   *  Parameters:
   *      message_digest_array: [out]
   *          This is an array of five unsigned integers which will be filled
   *          with the message digest that has been computed.
   *
   *  Returns:
   *      True if successful, false if it failed.
   *
   *  Comments:
   *
   */
  bool
  SHA1::Result(unsigned* message_digest_array)
  {
    int i; // Counter

    if (Corrupted) {
      return false;
    }

    if (!Computed) {
      PadMessage();
      Computed = true;
    }

    for (i = 0; i < 5; i++) {
      message_digest_array[i] = H[i];
    }

    return true;
  }

  /*
   *  Input
   *
   *  Description:
   *      This function accepts an array of octets as the next portion of
   *      the message.
   *
   *  Parameters:
   *      message_array: [in]
   *          An array of characters representing the next portion of the
   *          message.
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *
   */
  void
  SHA1::Input(const unsigned char* message_array, unsigned length)
  {
    if (!length) {
      return;
    }

    if (Computed || Corrupted) {
      Corrupted = true;
      return;
    }

    while (length-- && !Corrupted) {
      Message_Block[Message_Block_Index++] = (*message_array & 0xFF);

      Length_Low += 8;
      Length_Low &= 0xFFFFFFFF; // Force it to 32 bits
      if (Length_Low == 0) {
        Length_High++;
        Length_High &= 0xFFFFFFFF; // Force it to 32 bits
        if (Length_High == 0) {
          Corrupted = true; // Message is too long
        }
      }

      if (Message_Block_Index == 64) {
        ProcessMessageBlock();
      }

      message_array++;
    }
  }

  /*
   *  Input
   *
   *  Description:
   *      This function accepts an array of octets as the next portion of
   *      the message.
   *
   *  Parameters:
   *      message_array: [in]
   *          An array of characters representing the next portion of the
   *          message.
   *      length: [in]
   *          The length of the message_array
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *
   */
  void
  SHA1::Input(const char* message_array, unsigned length)
  {
    Input((unsigned char*)message_array, length);
  }

  /*
   *  Input
   *
   *  Description:
   *      This function accepts a single octets as the next message element.
   *
   *  Parameters:
   *      message_element: [in]
   *          The next octet in the message.
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *
   */
  void
  SHA1::Input(unsigned char message_element)
  {
    Input(&message_element, 1);
  }

  /*
   *  Input
   *
   *  Description:
   *      This function accepts a single octet as the next message element.
   *
   *  Parameters:
   *      message_element: [in]
   *          The next octet in the message.
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *
   */
  void
  SHA1::Input(char message_element)
  {
    Input((unsigned char*)&message_element, 1);
  }

  /*
   *  operator<<
   *
   *  Description:
   *      This operator makes it convenient to provide character strings to
   *      the SHA1 object for processing.
   *
   *  Parameters:
   *      message_array: [in]
   *          The character array to take as input.
   *
   *  Returns:
   *      A reference to the SHA1 object.
   *
   *  Comments:
   *      Each character is assumed to hold 8 bits of information.
   *
   */
  SHA1&
  SHA1::operator<<(const char* message_array)
  {
    const char* p = message_array;

    while (*p) {
      Input(*p);
      p++;
    }

    return *this;
  }

  /*
   *  operator<<
   *
   *  Description:
   *      This operator makes it convenient to provide character strings to
   *      the SHA1 object for processing.
   *
   *  Parameters:
   *      message_array: [in]
   *          The character array to take as input.
   *
   *  Returns:
   *      A reference to the SHA1 object.
   *
   *  Comments:
   *      Each character is assumed to hold 8 bits of information.
   *
   */
  SHA1&
  SHA1::operator<<(const unsigned char* message_array)
  {
    const unsigned char* p = message_array;

    while (*p) {
      Input(*p);
      p++;
    }

    return *this;
  }

  /*
   *  operator<<
   *
   *  Description:
   *      This function provides the next octet in the message.
   *
   *  Parameters:
   *      message_element: [in]
   *          The next octet in the message
   *
   *  Returns:
   *      A reference to the SHA1 object.
   *
   *  Comments:
   *      The character is assumed to hold 8 bits of information.
   *
   */
  SHA1&
  SHA1::operator<<(const char message_element)
  {
    Input((unsigned char*)&message_element, 1);

    return *this;
  }

  /*
   *  operator<<
   *
   *  Description:
   *      This function provides the next octet in the message.
   *
   *  Parameters:
   *      message_element: [in]
   *          The next octet in the message
   *
   *  Returns:
   *      A reference to the SHA1 object.
   *
   *  Comments:
   *      The character is assumed to hold 8 bits of information.
   *
   */
  SHA1&
  SHA1::operator<<(const unsigned char message_element)
  {
    Input(&message_element, 1);

    return *this;
  }

  /*
   *  ProcessMessageBlock
   *
   *  Description:
   *      This function will process the next 512 bits of the message
   *      stored in the Message_Block array.
   *
   *  Parameters:
   *      None.
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *      Many of the variable names in this function, especially the single
   *      character names, were used because those were the names used
   *      in the publication.
   *
   */
  void
  SHA1::ProcessMessageBlock()
  {
    const unsigned K[] = {// Constants defined for SHA-1
                          0x5A827999,
                          0x6ED9EBA1,
                          0x8F1BBCDC,
                          0xCA62C1D6};
    int t;                  // Loop counter
    unsigned temp;          // Temporary word value
    unsigned W[80];         // Word sequence
    unsigned A, B, C, D, E; // Word buffers

    /*
     *  Initialize the first 16 words in the array W
     */
    for (t = 0; t < 16; t++) {
      W[t] = ((unsigned)Message_Block[t * 4]) << 24;
      W[t] |= ((unsigned)Message_Block[t * 4 + 1]) << 16;
      W[t] |= ((unsigned)Message_Block[t * 4 + 2]) << 8;
      W[t] |= ((unsigned)Message_Block[t * 4 + 3]);
    }

    for (t = 16; t < 80; t++) {
      W[t] = CircularShift(1, W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16]);
    }

    A = H[0];
    B = H[1];
    C = H[2];
    D = H[3];
    E = H[4];

    for (t = 0; t < 20; t++) {
      temp = CircularShift(5, A) + ((B & C) | ((~B) & D)) + E + W[t] + K[0];
      temp &= 0xFFFFFFFF;
      E = D;
      D = C;
      C = CircularShift(30, B);
      B = A;
      A = temp;
    }

    for (t = 20; t < 40; t++) {
      temp = CircularShift(5, A) + (B ^ C ^ D) + E + W[t] + K[1];
      temp &= 0xFFFFFFFF;
      E = D;
      D = C;
      C = CircularShift(30, B);
      B = A;
      A = temp;
    }

    for (t = 40; t < 60; t++) {
      temp =
        CircularShift(5, A) + ((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
      temp &= 0xFFFFFFFF;
      E = D;
      D = C;
      C = CircularShift(30, B);
      B = A;
      A = temp;
    }

    for (t = 60; t < 80; t++) {
      temp = CircularShift(5, A) + (B ^ C ^ D) + E + W[t] + K[3];
      temp &= 0xFFFFFFFF;
      E = D;
      D = C;
      C = CircularShift(30, B);
      B = A;
      A = temp;
    }

    H[0] = (H[0] + A) & 0xFFFFFFFF;
    H[1] = (H[1] + B) & 0xFFFFFFFF;
    H[2] = (H[2] + C) & 0xFFFFFFFF;
    H[3] = (H[3] + D) & 0xFFFFFFFF;
    H[4] = (H[4] + E) & 0xFFFFFFFF;

    Message_Block_Index = 0;
  }

  /*
   *  PadMessage
   *
   *  Description:
   *      According to the standard, the message must be padded to an even
   *      512 bits.  The first padding bit must be a '1'.  The last 64 bits
   *      represent the length of the original message.  All bits in between
   *      should be 0.  This function will pad the message according to those
   *      rules by filling the message_block array accordingly.  It will also
   *      call ProcessMessageBlock() appropriately.  When it returns, it
   *      can be assumed that the message digest has been computed.
   *
   *  Parameters:
   *      None.
   *
   *  Returns:
   *      Nothing.
   *
   *  Comments:
   *
   */
  void
  SHA1::PadMessage()
  {
    /*
     *  Check to see if the current message block is too small to hold
     *  the initial padding bits and length.  If so, we will pad the
     *  block, process it, and then continue padding into a second block.
     */
    if (Message_Block_Index > 55) {
      Message_Block[Message_Block_Index++] = 0x80;
      while (Message_Block_Index < 64) {
        Message_Block[Message_Block_Index++] = 0;
      }

      ProcessMessageBlock();

      while (Message_Block_Index < 56) {
        Message_Block[Message_Block_Index++] = 0;
      }
    } else {
      Message_Block[Message_Block_Index++] = 0x80;
      while (Message_Block_Index < 56) {
        Message_Block[Message_Block_Index++] = 0;
      }
    }

    /*
     *  Store the message length as the last 8 octets
     */
    Message_Block[56] = (Length_High >> 24) & 0xFF;
    Message_Block[57] = (Length_High >> 16) & 0xFF;
    Message_Block[58] = (Length_High >> 8) & 0xFF;
    Message_Block[59] = (Length_High)&0xFF;
    Message_Block[60] = (Length_Low >> 24) & 0xFF;
    Message_Block[61] = (Length_Low >> 16) & 0xFF;
    Message_Block[62] = (Length_Low >> 8) & 0xFF;
    Message_Block[63] = (Length_Low)&0xFF;

    ProcessMessageBlock();
  }

  /*
   *  CircularShift
   *
   *  Description:
   *      This member function will perform a circular shifting operation.
   *
   *  Parameters:
   *      bits: [in]
   *          The number of bits to shift (1-31)
   *      word: [in]
   *          The value to shift (assumes a 32-bit integer)
   *
   *  Returns:
   *      The shifted value.
   *
   *  Comments:
   *
   */
  unsigned
  SHA1::CircularShift(int bits, unsigned word)
  {
    return ((word << bits) & 0xFFFFFFFF) | ((word & 0xFFFFFFFF) >> (32 - bits));
  }

} // end of namespace mf