text: /*
   *  sha1.c
   *
   *  Description:
   *      This file implements the Secure Hashing Algorithm 1 as
   *      defined in FIPS PUB 180-1 published April 17, 1995.
   *
   *      The SHA-1, produces a 160-bit message digest for a given
   *      data stream.  It should take about 2**n steps to find a
   *      message with the same digest as a given message and
   *      2**(n/2) to find any two messages with the same digest,
   *      when n is the digest size in bits.  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
   *      uses  (included via "sha1.h" to define 32 and 8
   *      bit unsigned integer types.  If your C compiler does not
   *      support 32 bit unsigned integers, this code is not
   *      appropriate.
   *
   *  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 the size of an 8-bit character.
   *
   */
  
  
  #include "sha1.h"
  
  /*
   *  Define the SHA1 circular left shift macro
   */
  #define SHA1CircularShift(bits,word) \
                  (((word) << (bits)) | ((word) >> (32-(bits))))
  
  /* Local Function Prototyptes */
  void SHA1PadMessage(SHA1Context *);
  void SHA1ProcessMessageBlock(SHA1Context *);
  
  /*
   *  SHA1Reset
   *
   *  Description:
   *      This function will initialize the SHA1Context in preparation
   *      for computing a new SHA1 message digest.
   *
   *  Parameters:
   *      context: [in/out]
   *          The context to reset.
   *
   *  Returns:
   *      sha Error Code.
   *
   */
  int SHA1Reset(SHA1Context *context)
  {
      if (!context)
      {
          return shaNull;
      }
  
      context->Length_Low             = 0;
      context->Length_High            = 0;
      context->Message_Block_Index    = 0;
  
      context->Intermediate_Hash[0]   = 0x67452301;
      context->Intermediate_Hash[1]   = 0xEFCDAB89;
      context->Intermediate_Hash[2]   = 0x98BADCFE;
      context->Intermediate_Hash[3]   = 0x10325476;
      context->Intermediate_Hash[4]   = 0xC3D2E1F0;
  
      context->Computed   = 0;
      context->Corrupted  = 0;
  
      return shaSuccess;
  }
  
  /*
   *  SHA1Result
   *
   *  Description:
   *      This function will return the 160-bit message digest into the
   *      Message_Digest array  provided by the caller.
   *      NOTE: The first octet of hash is stored in the 0th element,
   *            the last octet of hash in the 19th element.
   *
   *  Parameters:
   *      context: [in/out]
   *          The context to use to calculate the SHA-1 hash.
   *      Message_Digest: [out]
   *          Where the digest is returned.
   *
   *  Returns:
   *      sha Error Code.
   *
   */
  int SHA1Result( SHA1Context *context,
                  unsigned char Message_Digest[SHA1HashSize])
  {
      int i;
  
      if (!context || !Message_Digest)
      {
          return shaNull;
      }
  
      if (context->Corrupted)
      {
          return context->Corrupted;
      }
  
      if (!context->Computed)
      {
          SHA1PadMessage(context);
          for(i=0; i<64; ++i)
          {
              /* message may be sensitive, clear it out */
              context->Message_Block[i] = 0;
          }
          context->Length_Low = 0;    /* and clear length */
          context->Length_High = 0;
          context->Computed = 1;
      }
  
      for(i = 0; i < SHA1HashSize; ++i)
      {
          Message_Digest[i] = context->Intermediate_Hash[i>>2]
                              >> 8 * ( 3 - ( i & 0x03 ) );
      }
  
      return shaSuccess;
  }
  
  /*
   *  SHA1Input
   *
   *  Description:
   *      This function accepts an array of octets as the next portion
   *      of the message.
   *
   *  Parameters:
   *      context: [in/out]
   *          The SHA context to update
   *      message_array: [in]
   *          An array of characters representing the next portion of
   *          the message.
   *      length: [in]
   *          The length of the message in message_array
   *
   *  Returns:
   *      sha Error Code.
   *
   */
  int SHA1Input(    SHA1Context    *context,
                    const unsigned char  *message_array,
                    unsigned       length)
  {
      if (!length)
      {
          return shaSuccess;
      }
  
      if (!context || !message_array)
      {
          return shaNull;
      }
  
      if (context->Computed)
      {
          context->Corrupted = shaStateError;
          return shaStateError;
      }
  
      if (context->Corrupted)
      {
           return context->Corrupted;
      }
      while(length-- && !context->Corrupted)
      {
      context->Message_Block[context->Message_Block_Index++] =
                      (*message_array & 0xFF);
  
      context->Length_Low += 8;
      if (context->Length_Low == 0)
      {
          context->Length_High++;
          if (context->Length_High == 0)
          {
              /* Message is too long */
              context->Corrupted = 1;
          }
      }
  
      if (context->Message_Block_Index == 64)
      {
          SHA1ProcessMessageBlock(context);
      }
  
      message_array++;
      }
  
      return shaSuccess;
  }
  
  /*
   *  SHA1ProcessMessageBlock
   *
   *  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 code, especially the
   *      single character names, were used because those were the
   *      names used in the publication.
   *
   *
   */
  void SHA1ProcessMessageBlock(SHA1Context *context)
  {
      const unsigned int K[] =    {       /* Constants defined in SHA-1   */
                              0x5A827999,
                              0x6ED9EBA1,
                              0x8F1BBCDC,
                              0xCA62C1D6
                              };
      int           t;                 /* Loop counter                */
      unsigned int      temp;              /* Temporary word value        */
      unsigned int      W[80];             /* Word sequence               */
      unsigned int      A, B, C, D, E;     /* Word buffers                */
  
      /*
       *  Initialize the first 16 words in the array W
       */
      for(t = 0; t < 16; t++)
      {
          W[t] = context->Message_Block[t * 4] << 24;
          W[t] |= context->Message_Block[t * 4 + 1] << 16;
          W[t] |= context->Message_Block[t * 4 + 2] << 8;
          W[t] |= context->Message_Block[t * 4 + 3];
      }
  
      for(t = 16; t < 80; t++)
      {
         W[t] = SHA1CircularShift(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
      }
  
      A = context->Intermediate_Hash[0];
      B = context->Intermediate_Hash[1];
      C = context->Intermediate_Hash[2];
      D = context->Intermediate_Hash[3];
      E = context->Intermediate_Hash[4];
  
      for(t = 0; t < 20; t++)
      {
          temp =  SHA1CircularShift(5,A) +
                  ((B & C) | ((~B) & D)) + E + W[t] + K[0];
          E = D;
          D = C;
          C = SHA1CircularShift(30,B);
          B = A;
          A = temp;
      }
  
      for(t = 20; t < 40; t++)
      {
          temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[1];
          E = D;
          D = C;
          C = SHA1CircularShift(30,B);
          B = A;
          A = temp;
      }
  
      for(t = 40; t < 60; t++)
      {
          temp = SHA1CircularShift(5,A) +
                 ((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
          E = D;
          D = C;
          C = SHA1CircularShift(30,B);
          B = A;
          A = temp;
      }
  
      for(t = 60; t < 80; t++)
      {
          temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[3];
          E = D;
          D = C;
          C = SHA1CircularShift(30,B);
          B = A;
          A = temp;
      }
  
      context->Intermediate_Hash[0] += A;
      context->Intermediate_Hash[1] += B;
      context->Intermediate_Hash[2] += C;
      context->Intermediate_Hash[3] += D;
      context->Intermediate_Hash[4] += E;
  
      context->Message_Block_Index = 0;
  }
  
  
  /*
   *  SHA1PadMessage
   *
   *  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 the ProcessMessageBlock function
   *      provided appropriately.  When it returns, it can be assumed that
   *      the message digest has been computed.
   *
   *  Parameters:
   *      context: [in/out]
   *          The context to pad
   *      ProcessMessageBlock: [in]
   *          The appropriate SHA*ProcessMessageBlock function
   *  Returns:
   *      Nothing.
   *
   */
  
  void SHA1PadMessage(SHA1Context *context)
  {
      /*
       *  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 (context->Message_Block_Index > 55)
      {
          context->Message_Block[context->Message_Block_Index++] = 0x80;
          while(context->Message_Block_Index < 64)
          {
              context->Message_Block[context->Message_Block_Index++] = 0;
          }
  
          SHA1ProcessMessageBlock(context);
  
          while(context->Message_Block_Index < 56)
          {
              context->Message_Block[context->Message_Block_Index++] = 0;
          }
      }
      else
      {
          context->Message_Block[context->Message_Block_Index++] = 0x80;
          while(context->Message_Block_Index < 56)
          {
              context->Message_Block[context->Message_Block_Index++] = 0;
          }
      }
  
      /*
       *  Store the message length as the last 8 octets
       */
      context->Message_Block[56] = context->Length_High >> 24;
      context->Message_Block[57] = context->Length_High >> 16;
      context->Message_Block[58] = context->Length_High >> 8;
      context->Message_Block[59] = context->Length_High;
      context->Message_Block[60] = context->Length_Low >> 24;
      context->Message_Block[61] = context->Length_Low >> 16;
      context->Message_Block[62] = context->Length_Low >> 8;
      context->Message_Block[63] = context->Length_Low;
  
      SHA1ProcessMessageBlock(context);
  }
  
  