/*
 *  coap_sha1.c
 *
 *  Full Copyright Statement RFC3174
 *
 * =======================================================================
 *
 *  Copyright (C) The Internet Society (2001).  All Rights Reserved.
 *
 *  This document and translations of it may be copied and furnished to
 *  others, and derivative works that comment on or otherwise explain it
 *  or assist in its implementation may be prepared, copied, published
 *  and distributed, in whole or in part, without restriction of any
 *  kind, provided that the above copyright notice and this paragraph are
 *  included on all such copies and derivative works.  However, this
 *  document itself may not be modified in any way, such as by removing
 *  the copyright notice or references to the Internet Society or other
 *  Internet organizations, except as needed for the purpose of
 *  developing Internet standards in which case the procedures for
 *  copyrights defined in the Internet Standards process must be
 *  followed, or as required to translate it into languages other than
 *  English.
 *
 *  The limited permissions granted above are perpetual and will not be
 *  revoked by the Internet Society or its successors or assigns.
 *
 *  This document and the information contained herein is provided on an
 *  "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 *  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 *  BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 *  HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 *  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 *
 * =======================================================================
 *
 *  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 <stdint.h> (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.
 *
 * Taken from https://datatracker.ietf.org/doc/html/rfc3174#section-7.2
 * Reformatted as appropriate.
 */

/**
 * @file coap_sha1.c
 * @brief SHA-1 handling functions
 */

#include "coap3/coap_libcoap_build.h"

#if COAP_WS_SUPPORT && ! COAP_WITH_LIBOPENSSL && ! COAP_WITH_LIBGNUTLS && ! COAP_WITH_LIBMBEDTLS && ! COAP_WITH_LIBWOLFSSL
/*
 *  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,
           uint8_t 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 uint8_t  *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 uint32_t K[] =    {       /* Constants defined in SHA-1   */
    0x5A827999,
    0x6ED9EBA1,
    0x8F1BBCDC,
    0xCA62C1D6
  };
  int           t;                 /* Loop counter                */
  uint32_t      temp;              /* Temporary word value        */
  uint32_t      W[80];             /* Word sequence               */
  uint32_t      A, B, C, D, E;     /* Word buffers                */

  /*
   *  Initialize the first 16 words in the array W
   */
  for (t = 0; t < 16; t++) {
    W[t] = (uint32_t)(context->Message_Block[t * 4]) << 24;
    W[t] |= (uint32_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);
}
#endif /* COAP_WS_SUPPORT && ! COAP_WITH_LIBOPENSSL && ! COAP_WITH_LIBGNUTLS && ! COAP_WITH_LIBMBEDTLS */
