import the arc4random() function by ashes in Bug 90

1 files changed, 208 insertions, 0 deletions

diff --git a/libc/stdlib/arc4random.c b/libc/stdlib/arc4random.c
new file mode 100644
index 000000000..ebdd7d561
--- /dev/null
+++ b/libc/stdlib/arc4random.c
@@ -0,0 +1,208 @@
+/*	$$$: arc4random.c 2005/02/08 robert */
+/*	$NetBSD: arc4random.c,v 1.5.2.1 2004/03/26 22:52:50 jmc Exp $	*/
+/*	$OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $	*/
+
+/*
+ * Arc4 random number generator for OpenBSD.
+ * Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
+ *
+ * Modification and redistribution in source and binary forms is
+ * permitted provided that due credit is given to the author and the
+ * OpenBSD project by leaving this copyright notice intact.
+ */
+
+/*
+ * This code is derived from section 17.1 of Applied Cryptography,
+ * second edition, which describes a stream cipher allegedly
+ * compatible with RSA Labs "RC4" cipher (the actual description of
+ * which is a trade secret).  The same algorithm is used as a stream
+ * cipher called "arcfour" in Tatu Ylonen's ssh package.
+ *
+ * Here the stream cipher has been modified always to include the time
+ * when initializing the state.  That makes it impossible to
+ * regenerate the same random sequence twice, so this can't be used
+ * for encryption, but will generate good random numbers.
+ *
+ * RC4 is a registered trademark of RSA Laboratories.
+ */
+
+#include <features.h>
+#ifdef __UCLIBC_HAS_ARC4RANDOM__
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/time.h>
+#ifdef __ARC4RANDOM_USE_ERANDOM__
+#include <sys/sysctl.h>
+#endif
+
+struct arc4_stream {
+	u_int8_t i;
+	u_int8_t j;
+	u_int8_t s[256];
+};
+
+static int    rs_initialized;
+static struct arc4_stream rs;
+
+static inline void arc4_init(struct arc4_stream *);
+static inline void arc4_addrandom(struct arc4_stream *, u_char *, int);
+static void arc4_stir(struct arc4_stream *);
+static inline u_int8_t arc4_getbyte(struct arc4_stream *);
+static inline u_int32_t arc4_getword(struct arc4_stream *);
+
+static inline void
+arc4_init(as)
+	struct arc4_stream *as;
+{
+	int     n;
+
+	for (n = 0; n < 256; n++)
+		as->s[n] = n;
+	as->i = 0;
+	as->j = 0;
+}
+
+static inline void
+arc4_addrandom(as, dat, datlen)
+	struct arc4_stream *as;
+	u_char *dat;
+	int     datlen;
+{
+	int     n;
+	u_int8_t si;
+
+	as->i--;
+	for (n = 0; n < 256; n++) {
+		as->i = (as->i + 1);
+		si = as->s[as->i];
+		as->j = (as->j + si + dat[n % datlen]);
+		as->s[as->i] = as->s[as->j];
+		as->s[as->j] = si;
+	}
+	as->j = as->i;
+}
+
+static void
+arc4_stir(as)
+	struct arc4_stream *as;
+{
+	int     fd;
+	struct {
+		struct timeval tv;
+		u_int rnd[(128 - sizeof(struct timeval)) / sizeof(u_int)];
+	}       rdat;
+	int	n;
+
+	gettimeofday(&rdat.tv, NULL);
+	fd = __open("/dev/urandom", O_RDONLY);
+	if (fd != -1) {
+		__read(fd, rdat.rnd, sizeof(rdat.rnd));
+		__close(fd);
+	}
+#ifdef __ARC4RANDOM_USE_ERANDOM__
+	else {
+		int mib[3];
+		u_int i;
+		size_t len;
+
+		/* Device could not be opened, we might be chrooted, take
+		 * randomness from sysctl. */
+
+		mib[0] = CTL_KERN;
+		mib[1] = KERN_RANDOM;
+		mib[2] = RANDOM_ERANDOM;
+
+		for (i = 0; i < sizeof(rdat.rnd) / sizeof(u_int); i++) {
+			len = sizeof(u_int);
+			if (sysctl(mib, 3, &rdat.rnd[i], &len, NULL, 0) == -1)
+				break;
+		}
+	}
+#endif
+
+	arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
+
+	/*
+	 * Throw away the first N words of output, as suggested in the
+	 * paper "Weaknesses in the Key Scheduling Algorithm of RC4"
+	 * by Fluher, Mantin, and Shamir.
+	 * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
+	 * N = 256 in our case.
+	 */
+	for (n = 0; n < 256 * 4; n++)
+		arc4_getbyte(as);
+}
+
+static inline u_int8_t
+arc4_getbyte(as)
+	struct arc4_stream *as;
+{
+	u_int8_t si, sj;
+
+	as->i = (as->i + 1);
+	si = as->s[as->i];
+	as->j = (as->j + si);
+	sj = as->s[as->j];
+	as->s[as->i] = sj;
+	as->s[as->j] = si;
+	return (as->s[(si + sj) & 0xff]);
+}
+
+static inline u_int32_t
+arc4_getword(as)
+	struct arc4_stream *as;
+{
+	u_int32_t val;
+	val = arc4_getbyte(as) << 24;
+	val |= arc4_getbyte(as) << 16;
+	val |= arc4_getbyte(as) << 8;
+	val |= arc4_getbyte(as);
+	return val;
+}
+
+void
+arc4random_stir()
+{
+	if (!rs_initialized) {
+		arc4_init(&rs);
+		rs_initialized = 1;
+	}
+	arc4_stir(&rs);
+}
+
+void
+arc4random_addrandom(dat, datlen)
+	u_char *dat;
+	int     datlen;
+{
+	if (!rs_initialized)
+		arc4random_stir();
+	arc4_addrandom(&rs, dat, datlen);
+}
+
+u_int32_t
+arc4random()
+{
+	if (!rs_initialized)
+		arc4random_stir();
+	return arc4_getword(&rs);
+}
+
+#if 0
+/*-------- Test code --------*/
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(void) {
+    int random_number;
+    random_number = arc4random() % 65536;
+    printf("%d\n", random_number);
+    return 0;
+}
+#endif
+
+#endif /* __UCLIBC_HAS_ARC4RANDOM__ */