1 files changed, 250 insertions, 0 deletions
diff --git a/src/pluto/rnd.c b/src/pluto/rnd.c
new file mode 100644
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--- /dev/null
+++ b/src/pluto/rnd.c
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+/* randomness machinery
+ * Copyright (C) 1997 Angelos D. Keromytis.
+ * Copyright (C) 1998-2001  D. Hugh Redelmeier.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU 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/gpl.txt>.
+ *
+ * This program 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 General Public License
+ * for more details.
+ *
+ * RCSID $Id: rnd.c,v 1.3 2005/09/08 16:26:30 as Exp $
+ */
+
+/* A true random number generator (we hope)
+ *
+ * Under LINUX ("linux" predefined), use /dev/urandom.
+ * Under OpenBSD ("__OpenBSD__" predefined), use arc4random().
+ * Otherwise use our own random number generator based on clock skew.
+ *   I (ADK) first heard of the idea from John Ioannidis, who heard it
+ *   from Matt Blaze and/or Jack Lacy.
+ * ??? Why is mixing need for linux but not OpenBSD?
+ */
+
+/* Pluto's uses of randomness:
+ *
+ * - Setting up the "secret_of_the_day".  This changes every hour!  20
+ *   bytes a shot.  It is used in building responder cookies.
+ *
+ * - generating initiator cookies (8 bytes, once per Phase 1 initiation).
+ *
+ * - 32 bytes per DH local secret.  Once per Main Mode exchange and once
+ *   per Quick Mode Exchange with PFS.  (Size is our choice, with
+ *   tradeoffs.)
+ *
+ * - 16 bytes per nonce we generate.  Once per Main Mode exchange and
+ *   once per Quick Mode exchange.  (Again, we choose the size.)
+ *
+ * - 4 bytes per SPI number that we generate.  We choose the SPIs for all
+ *   inbound SPIs, one to three per IPSEC SA (one for AH (rare, probably)
+ *   one for ESP (almost always), and one for tunnel (very common)).
+ *   I don't actually know how the kernel would generate these numbers --
+ *   currently Pluto generates them; this isn't the way things will be
+ *   done in the future.
+ *
+ * - 4 bytes per Message ID we need to generate.  One per Quick Mode
+ *   exchange.  Eventually, one per informational exchange.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <fcntl.h>
+
+#include <freeswan.h>
+
+#include "sha1.h"
+#include "constants.h"
+#include "defs.h"
+#include "rnd.h"
+#include "log.h"
+#include "timer.h"
+
+#ifdef linux
+# define USE_DEV_RANDOM	1
+# define RANDOM_PATH    DEV_URANDOM
+#else
+# ifdef __OpenBSD__
+#  define USE_ARC4RANDOM
+# else
+#   define USE_CLOCK_SLEW
+# endif
+#endif
+
+#ifdef USE_ARC4RANDOM
+
+#define get_rnd_byte() (arc4random() % 256)
+
+#else	/**** start of large #else ****/
+
+#ifdef USE_DEV_RANDOM
+static int random_fd = NULL_FD;
+#endif
+
+#define RANDOM_POOL_SIZE   SHA1_DIGEST_SIZE
+static u_char random_pool[RANDOM_POOL_SIZE];
+
+#ifdef USE_DEV_RANDOM
+
+/* Generate (what we hope is) a true random byte using /dev/urandom  */
+static u_char
+generate_rnd_byte(void)
+{
+    u_char c;
+
+    if (read(random_fd, &c, sizeof(c)) == -1)
+	exit_log_errno((e, "read() failed in get_rnd_byte()"));
+
+    return c;
+}
+
+#else /* !USE_DEV_RANDOM */
+
+/* Generate (what we hope is) a true random byte using the clock skew trick.
+ * Note: this code is not maintained!  In particular, LINUX signal(2)
+ * semantics changed with glibc2 (and not for the better).  It isn't clear
+ * that this code will work.  We keep the code because someday it might
+ * come in handy.
+ */
+# error "This code is not maintained.  Please define USE_DEV_RANDOM."
+
+static volatile sig_atomic_t i, j, k;
+
+/* timer signal handler */
+static void
+rnd_handler(int ignore_me UNUSED)
+{
+    k <<= 1;	/* Shift left by 1 */
+    j++;
+    k |= (i & 0x1); /* Get lsbit of counter */
+
+    if (j != 8)
+	signal(SIGVTALRM, rnd_handler);
+}
+
+static u_char
+generate_rnd_byte(void)
+{
+    struct itimerval tmval, ntmval;
+
+# ifdef NEVER	/* ??? */
+#  ifdef linux
+    int mask = siggetmask();
+
+    mask |= SIGVTALRM;
+    sigsetmask(mask);
+#  endif
+# endif
+
+    i = 0;
+    j = 0;
+
+    ntmval.it_interval.tv_sec = 0;
+    ntmval.it_interval.tv_usec = 1;
+    ntmval.it_value.tv_sec = 0;
+    ntmval.it_value.tv_usec = 1;
+    signal(SIGVTALRM, rnd_handler);
+    setitimer(ITIMER_VIRTUAL, &ntmval, &tmval);
+
+    while (j != 8)
+	i++;
+
+    setitimer(ITIMER_VIRTUAL, &tmval, &ntmval);
+    signal(SIGVTALRM, SIG_IGN);
+
+# ifdef NEVER	/* ??? */
+#  ifdef linux
+    mask ^= SIGVTALRM;
+    sigsetmask(mask);
+#  endif
+# endif
+
+    return k;
+}
+
+#endif /* !USE_DEV_RANDOM */
+
+static void
+mix_pool(void)
+{
+    SHA1_CTX ctx;
+
+    SHA1Init(&ctx);
+    SHA1Update(&ctx, random_pool, RANDOM_POOL_SIZE);
+    SHA1Final(random_pool, &ctx);
+}
+
+/*
+ * Get a single random byte.
+ */
+static u_char
+get_rnd_byte(void)
+{
+    random_pool[RANDOM_POOL_SIZE - 1] = generate_rnd_byte();
+    random_pool[0] = generate_rnd_byte();
+    mix_pool();
+    return random_pool[0];
+}
+
+#endif /* !USE_ARC4RANDOM */	/**** end of large #else ****/
+
+void
+get_rnd_bytes(u_char *buffer, int length)
+{
+    int i;
+
+    for (i = 0; i < length; i++)
+	buffer[i] = get_rnd_byte();
+}
+
+/*
+ * Initialize the random pool.
+ */
+void
+init_rnd_pool(void)
+{
+#ifndef USE_ARC4RANDOM
+# ifdef USE_DEV_RANDOM
+    DBG(DBG_KLIPS, DBG_log("opening %s", RANDOM_PATH));
+    random_fd = open(RANDOM_PATH, O_RDONLY);
+    if (random_fd == -1)
+	exit_log_errno((e, "open of %s failed in init_rnd_pool()", RANDOM_PATH));
+    fcntl(random_fd, F_SETFD, FD_CLOEXEC);
+# endif
+
+    get_rnd_bytes(random_pool, RANDOM_POOL_SIZE);
+    mix_pool();
+#endif /* !USE_ARC4RANDOM */
+
+    /* start of rand(3) on the right foot */
+    {
+	unsigned int seed;
+
+	get_rnd_bytes((void *)&seed, sizeof(seed));
+	srand(seed);
+    }
+}
+
+u_char    secret_of_the_day[SHA1_DIGEST_SIZE];
+
+#ifndef NO_PLUTO
+
+void
+init_secret(void)
+{
+    /*
+     * Generate the secret value for responder cookies, and
+     * schedule an event for refresh.
+     */
+    get_rnd_bytes(secret_of_the_day, sizeof(secret_of_the_day));
+    event_schedule(EVENT_REINIT_SECRET, EVENT_REINIT_SECRET_DELAY, NULL);
+}
+
+#endif /* NO_PLUTO */