#include #include /* * After becoming frustrated with the lack of a standalone, portable, * decent random number generator, I decided to make one based on a * cryptographic one-way hash function. I chose MD5 since it is fast * and free source was readily available. More cryptographically * secure hash functions are available (e.g. SHA-1), but for the * purposes of a rand/random/erand48 replacement, MD5 should be more * than sufficient. * * MD5 takes an arbitrary amount of input and yields a 16 byte hash. * This RNG continually MD5's a 16 byte digest, and uses the bottom N * bits as the random number yielded, where N is just large enough to * include the largest random number desired. * * To yield a random number between 0 and r: * * create mask which has enough bits to include all of r * (for example, if r is 100, mask would be 0x7F) * * do { * digest = MD5(digest) * number = digest & mask * } while (number > r) * * The digest should be loaded and saved to a disk file between * invocations of a program using the RNG. * * Random functions appear after the included MD5 code. * * Send comments to: skrenta@pbm.com (Rich Skrenta) */ /*****************************************************************/ /* * 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, byte const *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, ctx->in, 64); byteSwap(ctx->in, 16); xMD5Transform(ctx->buf, ctx->in); buf += 64; len -= 64; } /* Handle any remaining bytes of data. */ bcopy(buf, 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(ctx->buf, digest, 16); bzero(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<>(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; } void MD5(void *dest, void *orig, int len) { struct xMD5Context context; xMD5Init(&context); xMD5Update(&context, orig, len); xMD5Final(dest, &context); } /*****************************************************************/ static unsigned long digest[4]; #define SEED_FILE "/home/dice/randseed" void load_seed() { int fd; fd = open(SEED_FILE, O_RDONLY); if (fd >= 0) { read(fd, digest, 16); close(fd); } } void save_seed() { int fd; fd = open(SEED_FILE, O_WRONLY|O_CREAT, 0600); if (fd >= 0) { write(fd, digest, 16); close(fd); } } int rnd(int low, int high) { unsigned int range = high - low; unsigned int mask = 0; unsigned int num; int r; for (r = range; r; r >>= 1) mask |= r; do { MD5(digest, digest, sizeof(digest)); num = digest[0] & mask; } while (num > range); return num + low; }