src/libfreeswan/prng.c

@@ -0,0 +1,202 @@
+/*
+ * crypto-class pseudorandom number generator
+ * currently uses same algorithm as RC4(TM), from Schneier 2nd ed p397
+ * Copyright (C) 2002  Henry Spencer.
+ * 
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Library General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/lgpl.txt>.
+ * 
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
+ * License for more details.
+ *
+ * RCSID $Id: prng.c,v 1.1 2004/03/15 20:35:26 as Exp $
+ */
+#include "internal.h"
+#include "freeswan.h"
+
+/*
+ - prng_init - initialize PRNG from a key
+ */
+void
+prng_init(prng, key, keylen)
+struct prng *prng;
+const unsigned char *key;
+size_t keylen;
+{
+	unsigned char k[256];
+	int i, j;
+	unsigned const char *p;
+	unsigned const char *keyend = key + keylen;
+	unsigned char t;
+
+	for (i = 0; i <= 255; i++)
+		prng->sbox[i] = i;
+	p = key;
+	for (i = 0; i <= 255; i++) {
+		k[i] = *p++;
+		if (p >= keyend)
+			p = key;
+	}
+	j = 0;
+	for (i = 0; i <= 255; i++) {
+		j = (j + prng->sbox[i] + k[i]) & 0xff;
+		t = prng->sbox[i];
+		prng->sbox[i] = prng->sbox[j];
+		prng->sbox[j] = t;
+		k[i] = 0;	/* clear out key memory */
+	}
+	prng->i = 0;
+	prng->j = 0;
+	prng->count = 0;
+}
+
+/*
+ - prng_bytes - get some pseudorandom bytes from PRNG
+ */
+void
+prng_bytes(prng, dst, dstlen)
+struct prng *prng;
+unsigned char *dst;
+size_t dstlen;
+{
+	int i, j, t;
+	unsigned char *p = dst;
+	size_t remain = dstlen;
+#	define	MAX	4000000000ul
+
+	while (remain > 0) {
+		i = (prng->i + 1) & 0xff;
+		prng->i = i;
+		j = (prng->j + prng->sbox[i]) & 0xff;
+		prng->j = j;
+		t = prng->sbox[i];
+		prng->sbox[i] = prng->sbox[j];
+		prng->sbox[j] = t;
+		t = (t + prng->sbox[i]) & 0xff;
+		*p++ = prng->sbox[t];
+		remain--;
+	}
+	if (prng->count < MAX - dstlen)
+		prng->count += dstlen;
+	else
+		prng->count = MAX;
+}
+
+/*
+ - prnt_count - how many bytes have been extracted from PRNG so far?
+ */
+unsigned long
+prng_count(prng)
+struct prng *prng;
+{
+	return prng->count;
+}
+
+/*
+ - prng_final - clear out PRNG to ensure nothing left in memory
+ */
+void
+prng_final(prng)
+struct prng *prng;
+{
+	int i;
+
+	for (i = 0; i <= 255; i++)
+		prng->sbox[i] = 0;
+	prng->i = 0;
+	prng->j = 0;
+	prng->count = 0;	/* just for good measure */
+}
+
+
+
+#ifdef PRNG_MAIN
+
+#include <stdio.h>
+
+void regress();
+
+int
+main(argc, argv)
+int argc;
+char *argv[];
+{
+	struct prng pr;
+	unsigned char buf[100];
+	unsigned char *p;
+	size_t n;
+
+	if (argc < 2) {
+		fprintf(stderr, "Usage: %s {key|-r}\n", argv[0]);
+		exit(2);
+	}
+
+	if (strcmp(argv[1], "-r") == 0) {
+		regress();
+		fprintf(stderr, "regress() returned?!?\n");
+		exit(1);
+	}
+
+	prng_init(&pr, argv[1], strlen(argv[1]));
+	prng_bytes(&pr, buf, 32);
+	printf("0x");
+	for (p = buf, n = 32; n > 0; p++, n--)
+		printf("%02x", *p);
+	printf("\n%lu bytes\n", prng_count(&pr));
+	prng_final(&pr);
+	exit(0);
+}
+
+void
+regress()
+{
+	struct prng pr;
+	unsigned char buf[100];
+	unsigned char *p;
+	size_t n;
+	/* somewhat non-random sample key */
+	unsigned char key[] = "here we go gathering nuts in May";
+	/* first thirty bytes of output from that key */
+	unsigned char good[] = "\x3f\x02\x8e\x4a\x2a\xea\x23\x18\x92\x7c"
+				"\x09\x52\x83\x61\xaa\x26\xce\xbb\x9d\x71"
+				"\x71\xe5\x10\x22\xaf\x60\x54\x8d\x5b\x28";
+	int nzero, none;
+	int show = 0;
+
+	prng_init(&pr, key, strlen(key));
+	prng_bytes(&pr, buf, sizeof(buf));
+	for (p = buf, n = sizeof(buf); n > 0; p++, n--) {
+		if (*p == 0)
+			nzero++;
+		if (*p == 255)
+			none++;
+	}
+	if (nzero > 3 || none > 3) {
+		fprintf(stderr, "suspiciously non-random output!\n");
+		show = 1;
+	}
+	if (memcmp(buf, good, strlen(good)) != 0) {
+		fprintf(stderr, "incorrect output!\n");
+		show = 1;
+	}
+	if (show) {
+		fprintf(stderr, "0x");
+		for (p = buf, n = sizeof(buf); n > 0; p++, n--)
+			fprintf(stderr, "%02x", *p);
+		fprintf(stderr, "\n");
+		exit(1);
+	}
+	if (prng_count(&pr) != sizeof(buf)) {
+		fprintf(stderr, "got %u bytes, but count is %lu\n",
+					sizeof(buf), prng_count(&pr));
+		exit(1);
+	}
+	prng_final(&pr);
+	exit(0);
+}
+
+#endif /* PRNG_MAIN */