/* Various 'random' functions for general use in the FB6 MUCK server. */
/* Attributions as given, modified by Jonah 'Points' Safar */

#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*****************************************************************/

/*
 * This code implements the MD5 message-digest algorithm.
 * The algorithm is due to Ron Rivest.  This code was
 * written by Colin Plumb in 1993, no copyright is claimed.
 * This code is in the public domain; do with it what you wish.
 *
 * Equivalent code is available from RSA Data Security, Inc.
 * This code has been tested against that, and is equivalent,
 * except that you don't need to include two pages of legalese
 * with every copy.
 *
 * To compute the message digest of a chunk of bytes, declare an
 * MD5Context structure, pass it to MD5Init, call MD5Update as
 * needed on buffers full of bytes, and then call MD5Final, which
 * will fill a supplied 16-byte array with the digest.
 */

typedef unsigned long word32;
typedef unsigned char byte;

struct xMD5Context {
	word32 buf[4];
	word32 bytes[2];
	word32 in[16];
};

void xMD5Init(struct xMD5Context *context);
void xMD5Update(struct xMD5Context *context, byte const *buf, int len);
void xMD5Final(byte digest[16], struct xMD5Context *context);
void xMD5Transform(word32 buf[4], word32 const in[16]);


/*
 * Shuffle the bytes into little-endian order within words, as per the
 * MD5 spec.  Note: this code works regardless of the byte order.
 */
void
byteSwap(word32 * buf, unsigned words)
{
	byte *p = (byte *) buf;

	do {
		*buf++ = (word32) ((unsigned) p[3] << 8 | p[2]) << 16 | ((unsigned) p[1] << 8 | p[0]);
		p += 4;
	} while (--words);
}

/*
 * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
 * initialization constants.
 */
void
xMD5Init(struct xMD5Context *ctx)
{
	ctx->buf[0] = 0x67452301;
	ctx->buf[1] = 0xefcdab89;
	ctx->buf[2] = 0x98badcfe;
	ctx->buf[3] = 0x10325476;

	ctx->bytes[0] = 0;
	ctx->bytes[1] = 0;
}

/*
 * Update context to reflect the concatenation of another buffer full
 * of bytes.
 */
void
xMD5Update(struct xMD5Context *ctx, const byte *buf, int len)
{
	word32 t;

	/* Update byte count */

	t = ctx->bytes[0];
	if ((ctx->bytes[0] = t + len) < t)
		ctx->bytes[1]++;		/* Carry from low to high */

	t = 64 - (t & 0x3f);		/* Space available in ctx->in (at least 1) */
	if ((unsigned) t > len) {
		bcopy(buf, (byte *) ctx->in + 64 - (unsigned) t, len);
		return;
	}
	/* First chunk is an odd size */
	bcopy(buf, (byte *) ctx->in + 64 - (unsigned) t, (unsigned) t);
	byteSwap(ctx->in, 16);
	xMD5Transform(ctx->buf, ctx->in);
	buf += (unsigned) t;
	len -= (unsigned) t;

	/* Process data in 64-byte chunks */
	while (len >= 64) {
		bcopy(buf, (byte*)ctx->in, 64);
		byteSwap(ctx->in, 16);
		xMD5Transform(ctx->buf, ctx->in);
		buf += 64;
		len -= 64;
	}

	/* Handle any remaining bytes of data. */
	bcopy(buf, (byte*)ctx->in, len);
}

/*
 * Final wrapup - pad to 64-byte boundary with the bit pattern 
 * 1 0* (64-bit count of bits processed, MSB-first)
 */
void
xMD5Final(byte digest[16], struct xMD5Context *ctx)
{
	int count = (int) (ctx->bytes[0] & 0x3f);	/* Bytes in ctx->in */
	byte *p = (byte *) ctx->in + count;	/* First unused byte */

	/* Set the first char of padding to 0x80.  There is always room. */
	*p++ = 0x80;

	/* Bytes of padding needed to make 56 bytes (-8..55) */
	count = 56 - 1 - count;

	if (count < 0) {			/* Padding forces an extra block */
		bzero(p, count + 8);
		byteSwap(ctx->in, 16);
		xMD5Transform(ctx->buf, ctx->in);
		p = (byte *) ctx->in;
		count = 56;
	}
	bzero(p, count + 8);
	byteSwap(ctx->in, 14);

	/* Append length in bits and transform */
	ctx->in[14] = ctx->bytes[0] << 3;
	ctx->in[15] = ctx->bytes[1] << 3 | ctx->bytes[0] >> 29;
	xMD5Transform(ctx->buf, ctx->in);

	byteSwap(ctx->buf, 4);
	bcopy((byte*)ctx->buf, digest, 16);
	bzero((byte*)ctx, sizeof(ctx));
}


/* The four core functions - F1 is optimized somewhat */

/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f,w,x,y,z,in,s) \
	 (w += f(x,y,z) + in, w = (w<<s | w>>(32-s)) + x)

/*
 * The core of the MD5 algorithm, this alters an existing MD5 hash to
 * reflect the addition of 16 longwords of new data.  MD5Update blocks
 * the data and converts bytes into longwords for this routine.
 */
void
xMD5Transform(word32 buf[4], word32 const in[16])
{
	register word32 a, b, c, d;

	a = buf[0];
	b = buf[1];
	c = buf[2];
	d = buf[3];

	MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
	MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
	MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
	MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
	MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
	MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
	MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
	MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
	MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
	MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
	MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
	MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
	MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
	MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
	MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
	MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);

	MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
	MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
	MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
	MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
	MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
	MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
	MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
	MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
	MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
	MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
	MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
	MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
	MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
	MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
	MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
	MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

	MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
	MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
	MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
	MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
	MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
	MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
	MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
	MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
	MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
	MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
	MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
	MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
	MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
	MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
	MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
	MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);

	MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
	MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
	MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
	MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
	MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
	MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
	MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
	MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
	MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
	MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
	MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
	MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
	MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
	MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
	MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
	MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);

	buf[0] += a;
	buf[1] += b;
	buf[2] += c;
	buf[3] += d;
}


/* dest buffer MUST be at least 16 bytes long. */
void
MD5hash(void *dest, const void *orig, int len)
{
	struct xMD5Context context;

	xMD5Init(&context);
	xMD5Update(&context, (const byte*)orig, len);
	xMD5Final((byte*)dest, &context);
}


/*
 * outbuf MUST be at least (((strlen(inbuf)+3)/4)*3)+1 chars long to read
 * the full set of base64 encoded data in the string.
 */
size_t
Base64Decode(void* outbuf, size_t outbuflen, const char* inbuf)
{
	unsigned char* outb = (unsigned char*)outbuf;
	const char *in = inbuf;
	unsigned int acc = 0;
	unsigned int val = 0;
	size_t bytcnt = 0;
	int bitcnt = 0;

	while (*in || bitcnt) {
		if (!*in || *in == '=') {
			val = 0;
		} else if (*in >= 'A' && *in <= 'Z') {
			val = *in - 'A';
		} else if (*in >= 'a' && *in <= 'z') {
			val = *in - 'a' + 26;
		} else if (*in >= '0' && *in <= '9') {
			val = *in - '0' + 52;
		} else if (*in == '+') {
			val = 62;
		} else if (*in == '/') {
			val = 63;
		} else {
			in++;
			continue;
		}
		acc = (acc << 6) | (val & 0x3f);
		bitcnt += 6;
		if (bitcnt >= 8) {
			if (bytcnt >= outbuflen) {
				break;
			}
			bytcnt++;
			bitcnt -= 8;
			*outb++ = (acc >> bitcnt) & 0xff;
			acc &= ~(0xff << bitcnt);
		}
		if (*in) in++;
	}
	return bytcnt;
}


/* outbuf MUST be at least (((inlen+2)/3)*4)+1 chars long. */
void
Base64Encode(char* outbuf, const void* inbuf, size_t inlen)
{
	const char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	const unsigned char* inb = (unsigned char*)inbuf;
	unsigned char* out;
	size_t numb;
	size_t endcnt;
	size_t i;

	numb = inlen;
	if (numb > 0) {
		unsigned int acc = 0;
		out = (unsigned char*)outbuf;
		for (i = 0; i < numb; i++) {
			if (i % 3 == 0) {
				acc = inb[i];
			} else if (i % 3 == 1) {
				acc <<= 8;
				acc |= inb[i];
			} else {
				acc <<= 8;
				acc |= inb[i];

				*out++ = b64[(acc >> 18) & 0x3f];
				*out++ = b64[(acc >> 12) & 0x3f];
				*out++ = b64[(acc >> 6) & 0x3f];
				*out++ = b64[acc & 0x3f];
			}
		}
		if (i % 3 == 0) {
		    endcnt = 0;
		} else if (i % 3 == 1) {
			endcnt = 2;
		} else {
		    endcnt = 1;
		}
		for (; i % 3; i++) {
			acc <<= 8;
		}
		if (endcnt > 0) {
			*out++ = b64[(acc >> 18) & 0x3f];
			*out++ = b64[(acc >> 12) & 0x3f];
			if (endcnt < 2)
				*out++ = b64[(acc >> 6) & 0x3f];
			if (endcnt < 1)
				*out++ = b64[acc & 0x3f];
			while (endcnt-->0)
				*out++ = '=';
		}
	}
	*out++ = '\0';

	out = (unsigned char*)outbuf;
	while (*out) {
		if (*out++ > 127)
			abort();
	}
}


/* dest buffer MUST be at least 24 chars long. */
void
MD5base64(char *dest, const void *orig, int len)
{
	void* tmp = (void*)malloc(16);
	MD5hash(tmp, orig, len);
	Base64Encode(dest, tmp, 16);
	free(tmp);
}

/*****************************************************************/

/*
static unsigned long digest[4];
*/

/* Create the initial buffer for the given connection and dump some semi-
   random string into it to start.  If seed is zero, seed off the clock. */
void *
init_seed(char *seed)
{
	unsigned long *digest;
	int loop;
	int tbuf[8];

	if (!(digest = (unsigned long *) malloc(sizeof(unsigned long) * 4))) {
		return (NULL);
	}
	if (!seed) {
		/* No fixed seed given... make something up */
		srand((unsigned int) time(NULL));
		for (loop = 0; loop < 8; loop++)
			tbuf[loop] = rand();
		memcpy(digest, tbuf, 16);
	} else {
		memcpy(digest, seed, 16);
	}
	return ((void *) digest);
}

/* Deletes a buffer. */
void
delete_seed(void *buffer)
{
	free(buffer);
}

unsigned long
rnd(void *buffer)
{
	unsigned long *digest = (unsigned long *) buffer;

	if (!digest)
		return (0);
	MD5hash(digest, digest, sizeof(digest));
	return (digest[0]);
}

/* Test code, ignore
int main(int argc, char **argv) {
  void *seed = NULL;
  int loop;
  char buff[2048];

  gets(buff);
  if (buff[0]=='\0'||buff[0]=='\n') {
    seed = init_seed(NULL);
  } else {
    seed = init_seed(buff);
  }
  for (loop = 0; loop < 16; loop++)
    printf("%2d:  %12lu\n",loop,rnd(seed));
  delete_seed(seed);
  exit(1);
}
*/