/*
 * Originally from Polarssl here
 * http://polarssl.org/show_source?file=md5
 * under GPL2 or later
 * truncated to remove hmac support
 */


#include <string.h>
#include <stdio.h>


typedef struct
{
    unsigned long total[2];     /*!< number of bytes processed  */
    unsigned long state[4];     /*!< intermediate digest state  */
    unsigned char buffer[64];   /*!< data block being processed */
}
md5_context;


/**
 * \brief          MD5 context setup
 *
 * \param ctx      context to be initialized
 */
void md5_starts( md5_context *ctx );

/**
 * \brief          MD5 process buffer
 *
 * \param ctx      MD5 context
 * \param input    buffer holding the  data
 * \param ilen     length of the input data
 */
void md5_update( md5_context *ctx, const unsigned char *input, int ilen );

/**
 * \brief          MD5 final digest
 *
 * \param ctx      MD5 context
 * \param output   MD5 checksum result
 */
void md5_finish( md5_context *ctx, unsigned char output[16] );

/**
 * \brief          Output = MD5( input buffer )
 *
 * \param input    buffer holding the  data
 * \param ilen     length of the input data
 * \param output   MD5 checksum result
 */
void md5( const unsigned char *input, int ilen, unsigned char output[16] );

/**
 * \brief          Output = MD5( file contents )
 *
 * \param path     input file name
 * \param output   MD5 checksum result
 *
 * \return         0 if successful, 1 if fopen failed,
 *                 or 2 if fread failed
 */
int md5_file( const char *path, unsigned char output[16] );


/*
 * 32-bit integer manipulation macros (little endian)
 */
#ifndef GET_ULONG_LE
#define GET_ULONG_LE(n,b,i)                             \
{                                                       \
    (n) = ( (unsigned long) (b)[(i)    ]       )        \
        | ( (unsigned long) (b)[(i) + 1] <<  8 )        \
        | ( (unsigned long) (b)[(i) + 2] << 16 )        \
        | ( (unsigned long) (b)[(i) + 3] << 24 );       \
}
#endif

#ifndef PUT_ULONG_LE
#define PUT_ULONG_LE(n,b,i)                             \
{                                                       \
    (b)[(i)    ] = (unsigned char) ( (n)       );       \
    (b)[(i) + 1] = (unsigned char) ( (n) >>  8 );       \
    (b)[(i) + 2] = (unsigned char) ( (n) >> 16 );       \
    (b)[(i) + 3] = (unsigned char) ( (n) >> 24 );       \
}
#endif

/*
 * MD5 context setup
 */
void md5_starts( md5_context *ctx )
{
    ctx->total[0] = 0;
    ctx->total[1] = 0;

    ctx->state[0] = 0x67452301;
    ctx->state[1] = 0xEFCDAB89;
    ctx->state[2] = 0x98BADCFE;
    ctx->state[3] = 0x10325476;
}

static void md5_process( md5_context *ctx, const unsigned char data[64] )
{
    unsigned long X[16], A, B, C, D;

    GET_ULONG_LE( X[ 0], data,  0 );
    GET_ULONG_LE( X[ 1], data,  4 );
    GET_ULONG_LE( X[ 2], data,  8 );
    GET_ULONG_LE( X[ 3], data, 12 );
    GET_ULONG_LE( X[ 4], data, 16 );
    GET_ULONG_LE( X[ 5], data, 20 );
    GET_ULONG_LE( X[ 6], data, 24 );
    GET_ULONG_LE( X[ 7], data, 28 );
    GET_ULONG_LE( X[ 8], data, 32 );
    GET_ULONG_LE( X[ 9], data, 36 );
    GET_ULONG_LE( X[10], data, 40 );
    GET_ULONG_LE( X[11], data, 44 );
    GET_ULONG_LE( X[12], data, 48 );
    GET_ULONG_LE( X[13], data, 52 );
    GET_ULONG_LE( X[14], data, 56 );
    GET_ULONG_LE( X[15], data, 60 );

#define S(x,n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))

#define P(a,b,c,d,k,s,t)                                \
{                                                       \
    a += F(b,c,d) + X[k] + t; a = S(a,s) + b;           \
}

    A = ctx->state[0];
    B = ctx->state[1];
    C = ctx->state[2];
    D = ctx->state[3];

#define F(x,y,z) (z ^ (x & (y ^ z)))

    P( A, B, C, D,  0,  7, 0xD76AA478 );
    P( D, A, B, C,  1, 12, 0xE8C7B756 );
    P( C, D, A, B,  2, 17, 0x242070DB );
    P( B, C, D, A,  3, 22, 0xC1BDCEEE );
    P( A, B, C, D,  4,  7, 0xF57C0FAF );
    P( D, A, B, C,  5, 12, 0x4787C62A );
    P( C, D, A, B,  6, 17, 0xA8304613 );
    P( B, C, D, A,  7, 22, 0xFD469501 );
    P( A, B, C, D,  8,  7, 0x698098D8 );
    P( D, A, B, C,  9, 12, 0x8B44F7AF );
    P( C, D, A, B, 10, 17, 0xFFFF5BB1 );
    P( B, C, D, A, 11, 22, 0x895CD7BE );
    P( A, B, C, D, 12,  7, 0x6B901122 );
    P( D, A, B, C, 13, 12, 0xFD987193 );
    P( C, D, A, B, 14, 17, 0xA679438E );
    P( B, C, D, A, 15, 22, 0x49B40821 );

#undef F

#define F(x,y,z) (y ^ (z & (x ^ y)))

    P( A, B, C, D,  1,  5, 0xF61E2562 );
    P( D, A, B, C,  6,  9, 0xC040B340 );
    P( C, D, A, B, 11, 14, 0x265E5A51 );
    P( B, C, D, A,  0, 20, 0xE9B6C7AA );
    P( A, B, C, D,  5,  5, 0xD62F105D );
    P( D, A, B, C, 10,  9, 0x02441453 );
    P( C, D, A, B, 15, 14, 0xD8A1E681 );
    P( B, C, D, A,  4, 20, 0xE7D3FBC8 );
    P( A, B, C, D,  9,  5, 0x21E1CDE6 );
    P( D, A, B, C, 14,  9, 0xC33707D6 );
    P( C, D, A, B,  3, 14, 0xF4D50D87 );
    P( B, C, D, A,  8, 20, 0x455A14ED );
    P( A, B, C, D, 13,  5, 0xA9E3E905 );
    P( D, A, B, C,  2,  9, 0xFCEFA3F8 );
    P( C, D, A, B,  7, 14, 0x676F02D9 );
    P( B, C, D, A, 12, 20, 0x8D2A4C8A );

#undef F
    
#define F(x,y,z) (x ^ y ^ z)

    P( A, B, C, D,  5,  4, 0xFFFA3942 );
    P( D, A, B, C,  8, 11, 0x8771F681 );
    P( C, D, A, B, 11, 16, 0x6D9D6122 );
    P( B, C, D, A, 14, 23, 0xFDE5380C );
    P( A, B, C, D,  1,  4, 0xA4BEEA44 );
    P( D, A, B, C,  4, 11, 0x4BDECFA9 );
    P( C, D, A, B,  7, 16, 0xF6BB4B60 );
    P( B, C, D, A, 10, 23, 0xBEBFBC70 );
    P( A, B, C, D, 13,  4, 0x289B7EC6 );
    P( D, A, B, C,  0, 11, 0xEAA127FA );
    P( C, D, A, B,  3, 16, 0xD4EF3085 );
    P( B, C, D, A,  6, 23, 0x04881D05 );
    P( A, B, C, D,  9,  4, 0xD9D4D039 );
    P( D, A, B, C, 12, 11, 0xE6DB99E5 );
    P( C, D, A, B, 15, 16, 0x1FA27CF8 );
    P( B, C, D, A,  2, 23, 0xC4AC5665 );

#undef F

#define F(x,y,z) (y ^ (x | ~z))

    P( A, B, C, D,  0,  6, 0xF4292244 );
    P( D, A, B, C,  7, 10, 0x432AFF97 );
    P( C, D, A, B, 14, 15, 0xAB9423A7 );
    P( B, C, D, A,  5, 21, 0xFC93A039 );
    P( A, B, C, D, 12,  6, 0x655B59C3 );
    P( D, A, B, C,  3, 10, 0x8F0CCC92 );
    P( C, D, A, B, 10, 15, 0xFFEFF47D );
    P( B, C, D, A,  1, 21, 0x85845DD1 );
    P( A, B, C, D,  8,  6, 0x6FA87E4F );
    P( D, A, B, C, 15, 10, 0xFE2CE6E0 );
    P( C, D, A, B,  6, 15, 0xA3014314 );
    P( B, C, D, A, 13, 21, 0x4E0811A1 );
    P( A, B, C, D,  4,  6, 0xF7537E82 );
    P( D, A, B, C, 11, 10, 0xBD3AF235 );
    P( C, D, A, B,  2, 15, 0x2AD7D2BB );
    P( B, C, D, A,  9, 21, 0xEB86D391 );

#undef F

    ctx->state[0] += A;
    ctx->state[1] += B;
    ctx->state[2] += C;
    ctx->state[3] += D;
}

/*
 * MD5 process buffer
 */
void md5_update( md5_context *ctx, const unsigned char *input, int ilen )
{
    int fill;
    unsigned long left;

    if( ilen <= 0 )
        return;

    left = ctx->total[0] & 0x3F;
    fill = 64 - left;

    ctx->total[0] += ilen;
    ctx->total[0] &= 0xFFFFFFFF;

    if( ctx->total[0] < (unsigned long) ilen )
        ctx->total[1]++;

    if( left && ilen >= fill )
    {
        memcpy( (void *) (ctx->buffer + left),
                (void *) input, fill );
        md5_process( ctx, ctx->buffer );
        input += fill;
        ilen  -= fill;
        left = 0;
    }

    while( ilen >= 64 )
    {
        md5_process( ctx, input );
        input += 64;
        ilen  -= 64;
    }

    if( ilen > 0 )
    {
        memcpy( (void *) (ctx->buffer + left),
                (void *) input, ilen );
    }
}

static const unsigned char md5_padding[64] =
{
 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/*
 * MD5 final digest
 */
void md5_finish( md5_context *ctx, unsigned char output[16] )
{
    unsigned long last, padn;
    unsigned long high, low;
    unsigned char msglen[8];

    high = ( ctx->total[0] >> 29 )
         | ( ctx->total[1] <<  3 );
    low  = ( ctx->total[0] <<  3 );

    PUT_ULONG_LE( low,  msglen, 0 );
    PUT_ULONG_LE( high, msglen, 4 );

    last = ctx->total[0] & 0x3F;
    padn = ( last < 56 ) ? ( 56 - last ) : ( 120 - last );

    md5_update( ctx, (unsigned char *) md5_padding, padn );
    md5_update( ctx, msglen, 8 );

    PUT_ULONG_LE( ctx->state[0], output,  0 );
    PUT_ULONG_LE( ctx->state[1], output,  4 );
    PUT_ULONG_LE( ctx->state[2], output,  8 );
    PUT_ULONG_LE( ctx->state[3], output, 12 );
}

/*
 * output = MD5( input buffer )
 */
void md5( const unsigned char *input, int ilen, unsigned char output[16] )
{
    md5_context ctx;

    md5_starts( &ctx );
    md5_update( &ctx, input, ilen );
    md5_finish( &ctx, output );

    memset( &ctx, 0, sizeof( md5_context ) );
}

/*
 * output = MD5( file contents )
 */
int md5_file( const char *path, unsigned char output[16] )
{
    FILE *f;
    size_t n;
    md5_context ctx;
    unsigned char buf[1024];

    if( ( f = fopen( path, "rb" ) ) == NULL )
        return( 1 );

    md5_starts( &ctx );

    while( ( n = fread( buf, 1, sizeof( buf ), f ) ) > 0 )
        md5_update( &ctx, buf, (int) n );

    md5_finish( &ctx, output );

    memset( &ctx, 0, sizeof( md5_context ) );

    if( ferror( f ) != 0 )
    {
        fclose( f );
        return( 2 );
    }

    fclose( f );
    return( 0 );
}