// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

/**************************** sha1.c ****************************/
/******************** See RFC 4634 for details ******************/
/*
*  Description:
*      This file implements the Secure Hash Signature Standard
*      algorithms as defined in the National Institute of Standards
*      and Technology Federal Information Processing Standards
*      Publication (FIPS PUB) 180-1 published on April 17, 1995, 180-2
*      published on August 1, 2002, and the FIPS PUB 180-2 Change
*      Notice published on February 28, 2004.
*
*      A combined document showing all algorithms is available at
*              http://csrc.nist.gov/publications/fips/
*              fips180-2/fips180-2withchangenotice.pdf
*
*      The SHA-1 algorithm 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 "sha.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. This implementation uses SHA1Input() to hash the bits
*      that are a multiple of the size of an 8-bit character, and then
*      uses SHA1FinalBits() to hash the final few bits of the input.
*/

#include <stdlib.h>
#include "azure_c_shared_utility/gballoc.h"

#include "azure_c_shared_utility/sha.h"
#include "azure_c_shared_utility/sha-private.h"

/*
*  Define the SHA1 circular left shift macro
*/
#define SHA1_ROTL(bits,word) \
                (((word) << (bits)) | ((word) >> (32-(bits))))

/*
* add "length" to the length
*/
#define SHA1AddLength(context, length)                     \
    (addTemp = (context)->Length_Low,                      \
     (context)->Corrupted =                                \
        (((context)->Length_Low += (length)) < addTemp) && \
        (++(context)->Length_High == 0) ? 1 : 0)

/* Local Function Prototypes */
static void SHA1Finalize(SHA1Context *context, uint8_t Pad_Byte);
static void SHA1PadMessage(SHA1Context *, uint8_t Pad_Byte);
static 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;


    /* Initial Hash Values: FIPS-180-2 section 5.3.1 */
    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;
}

/*
*  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 int length)
{
    int result;
    uint32_t addTemp;
    if (!length)
    {
        result = shaSuccess;
    }
    else if (!context || !message_array)
    {
        result = shaNull;
    }
    else if (context->Computed) 
    {
        result = context->Corrupted = shaStateError;
    }
    else if (context->Corrupted)
    {
        result = context->Corrupted;
    }
    else
    {
        while (length-- && !context->Corrupted)
        {
            context->Message_Block[context->Message_Block_Index++] = (*message_array & 0xFF);

            if (!SHA1AddLength(context, 8) && (context->Message_Block_Index == SHA1_Message_Block_Size))
            {
                SHA1ProcessMessageBlock(context);
            }
            message_array++;
        }
        result = shaSuccess;
    }
    return result;
}

/*
* SHA1FinalBits
*
* Description:
*   This function will add in any final bits of the message.
*
* Parameters:
*   context: [in/out]
*     The SHA context to update
*   message_bits: [in]
*     The final bits of the message, in the upper portion of the
*     byte. (Use 0b###00000 instead of 0b00000### to input the
*     three bits ###.)
*   length: [in]
*     The number of bits in message_bits, between 1 and 7.
*
* Returns:
*   sha Error Code.
*/
int SHA1FinalBits(SHA1Context *context, const uint8_t message_bits,
    unsigned int length)
{
    uint32_t addTemp;

    uint8_t masks[8] = {
        /* 0 0b00000000 */ 0x00, /* 1 0b10000000 */ 0x80,
        /* 2 0b11000000 */ 0xC0, /* 3 0b11100000 */ 0xE0,
        /* 4 0b11110000 */ 0xF0, /* 5 0b11111000 */ 0xF8,
        /* 6 0b11111100 */ 0xFC, /* 7 0b11111110 */ 0xFE
    };
    uint8_t markbit[8] = {
        /* 0 0b10000000 */ 0x80, /* 1 0b01000000 */ 0x40,
        /* 2 0b00100000 */ 0x20, /* 3 0b00010000 */ 0x10,
        /* 4 0b00001000 */ 0x08, /* 5 0b00000100 */ 0x04,
        /* 6 0b00000010 */ 0x02, /* 7 0b00000001 */ 0x01
    };

    if (!length)
        return shaSuccess;

    if (!context)
        return shaNull;

    if (context->Computed || (length >= 8) || (length == 0)) {
        context->Corrupted = shaStateError;
        return shaStateError;
    }

    if (context->Corrupted)
        return context->Corrupted;

    SHA1AddLength(context, length);
    SHA1Finalize(context,
        (uint8_t)((message_bits & masks[length]) | markbit[length]));

    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)
        SHA1Finalize(context, 0x80);

    for (i = 0; i < SHA1HashSize; ++i)
        Message_Digest[i] = (uint8_t)(context->Intermediate_Hash[i >> 2]
        >> 8 * (3 - (i & 0x03)));

    return shaSuccess;
}

/*
* SHA1Finalize
*
* Description:
*   This helper function finishes off the digest calculations.
*
* Parameters:
*   context: [in/out]
*     The SHA context to update
*   Pad_Byte: [in]
*     The last byte to add to the digest before the 0-padding
*     and length. This will contain the last bits of the message
*     followed by another single bit. If the message was an
*     exact multiple of 8-bits long, Pad_Byte will be 0x80.
*
* Returns:
*   sha Error Code.
*
*/
static void SHA1Finalize(SHA1Context *context, uint8_t Pad_Byte)
{
    int i;
    SHA1PadMessage(context, Pad_Byte);
    /* message may be sensitive, clear it out */
    for (i = 0; i < SHA1_Message_Block_Size; ++i)
        context->Message_Block[i] = 0;
    context->Length_Low = 0;  /* and clear length */
    context->Length_High = 0;
    context->Computed = 1;
}

/*
* 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 helper function will pad the
*   message according to those rules by filling the Message_Block
*   array accordingly. When it returns, it can be assumed that the
*   message digest has been computed.
*
* Parameters:
*   context: [in/out]
*     The context to pad
*   Pad_Byte: [in]
*     The last byte to add to the digest before the 0-padding
*     and length. This will contain the last bits of the message
*     followed by another single bit. If the message was an
*     exact multiple of 8-bits long, Pad_Byte will be 0x80.
*
* Returns:
*   Nothing.
*/
static void SHA1PadMessage(SHA1Context *context, uint8_t Pad_Byte)
{
    /*
    * 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 >= (SHA1_Message_Block_Size - 8)) {
        context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
        while (context->Message_Block_Index < SHA1_Message_Block_Size)
            context->Message_Block[context->Message_Block_Index++] = 0;

        SHA1ProcessMessageBlock(context);
    }
    else
        context->Message_Block[context->Message_Block_Index++] = Pad_Byte;

    while (context->Message_Block_Index < (SHA1_Message_Block_Size - 8))
        context->Message_Block[context->Message_Block_Index++] = 0;

    /*
    * Store the message length as the last 8 octets
    */
    context->Message_Block[56] = (uint8_t)(context->Length_High >> 24);
    context->Message_Block[57] = (uint8_t)(context->Length_High >> 16);

    context->Message_Block[58] = (uint8_t)(context->Length_High >> 8);
    context->Message_Block[59] = (uint8_t)(context->Length_High);
    context->Message_Block[60] = (uint8_t)(context->Length_Low >> 24);
    context->Message_Block[61] = (uint8_t)(context->Length_Low >> 16);
    context->Message_Block[62] = (uint8_t)(context->Length_Low >> 8);
    context->Message_Block[63] = (uint8_t)(context->Length_Low);

    SHA1ProcessMessageBlock(context);
}

/*
* SHA1ProcessMessageBlock
*
* Description:
*   This helper 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.
*/
static void SHA1ProcessMessageBlock(SHA1Context *context)
{
    /* Constants defined in FIPS-180-2, section 4.2.1 */
    const uint32_t K[4] = {
        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] |= ((uint32_t)context->Message_Block[t * 4 + 2]) << 8;
        W[t] |= ((uint32_t)context->Message_Block[t * 4 + 3]);
    }

    for (t = 16; t < 80; t++)
        W[t] = SHA1_ROTL(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 = SHA1_ROTL(5, A) + SHA_Ch(B, C, D) + E + W[t] + K[0];
        E = D;
        D = C;
        C = SHA1_ROTL(30, B);
        B = A;
        A = temp;
    }

    for (t = 20; t < 40; t++) {
        temp = SHA1_ROTL(5, A) + SHA_Parity(B, C, D) + E + W[t] + K[1];
        E = D;
        D = C;
        C = SHA1_ROTL(30, B);
        B = A;
        A = temp;
    }

    for (t = 40; t < 60; t++) {
        temp = SHA1_ROTL(5, A) + SHA_Maj(B, C, D) + E + W[t] + K[2];
        E = D;
        D = C;
        C = SHA1_ROTL(30, B);
        B = A;
        A = temp;
    }

    for (t = 60; t < 80; t++) {
        temp = SHA1_ROTL(5, A) + SHA_Parity(B, C, D) + E + W[t] + K[3];
        E = D;
        D = C;
        C = SHA1_ROTL(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;
}

