1 files changed, 241 insertions, 0 deletions
diff --git a/random.c b/random.c
new file mode 100644
index 0000000..cbbe016
--- /dev/null
+++ b/random.c
@@ -0,0 +1,241 @@
+/*
+ * Dropbear - a SSH2 server
+ * 
+ * Copyright (c) 2002,2003 Matt Johnston
+ * All rights reserved.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE. */
+
+#include "includes.h"
+#include "buffer.h"
+#include "dbutil.h"
+#include "bignum.h"
+
+static int donerandinit = 0;
+
+/* this is used to generate unique output from the same hashpool */
+static uint32_t counter = 0;
+#define MAX_COUNTER 1<<31 /* the max value for the counter, so it won't loop */
+
+static unsigned char hashpool[SHA1_HASH_SIZE];
+
+#define INIT_SEED_SIZE 32 /* 256 bits */
+
+static void readrand(unsigned char* buf, unsigned int buflen);
+
+/* The basic setup is we read some data from /dev/(u)random or prngd and hash it
+ * into hashpool. To read data, we hash together current hashpool contents,
+ * and a counter. We feed more data in by hashing the current pool and new
+ * data into the pool.
+ *
+ * It is important to ensure that counter doesn't wrap around before we
+ * feed in new entropy.
+ *
+ */
+
+static void readrand(unsigned char* buf, unsigned int buflen) {
+
+	static int already_blocked = 0;
+	int readfd;
+	unsigned int readpos;
+	int readlen;
+#ifdef DROPBEAR_PRNGD_SOCKET
+	struct sockaddr_un egdsock;
+	char egdcmd[2];
+#endif
+
+#ifdef DROPBEAR_RANDOM_DEV
+	readfd = open(DROPBEAR_RANDOM_DEV, O_RDONLY);
+	if (readfd < 0) {
+		dropbear_exit("couldn't open random device");
+	}
+#endif
+
+#ifdef DROPBEAR_PRNGD_SOCKET
+	memset((void*)&egdsock, 0x0, sizeof(egdsock));
+	egdsock.sun_family = AF_UNIX;
+	strlcpy(egdsock.sun_path, DROPBEAR_PRNGD_SOCKET,
+			sizeof(egdsock.sun_path));
+
+	readfd = socket(PF_UNIX, SOCK_STREAM, 0);
+	if (readfd < 0) {
+		dropbear_exit("couldn't open random device");
+	}
+	/* todo - try various common locations */
+	if (connect(readfd, (struct sockaddr*)&egdsock, 
+			sizeof(struct sockaddr_un)) < 0) {
+		dropbear_exit("couldn't open random device");
+	}
+
+	if (buflen > 255)
+		dropbear_exit("can't request more than 255 bytes from egd");
+	egdcmd[0] = 0x02;	/* blocking read */
+	egdcmd[1] = (unsigned char)buflen;
+	if (write(readfd, egdcmd, 2) < 0)
+		dropbear_exit("can't send command to egd");
+#endif
+
+	/* read the actual random data */
+	readpos = 0;
+	do {
+		if (!already_blocked)
+		{
+			int ret;
+			struct timeval timeout;
+			fd_set read_fds;
+
+			timeout.tv_sec = 2; /* two seconds should be enough */
+			timeout.tv_usec = 0;
+
+			FD_ZERO(&read_fds);
+			FD_SET(readfd, &read_fds);
+			ret = select(readfd + 1, &read_fds, NULL, NULL, &timeout);
+			if (ret == 0)
+			{
+				dropbear_log(LOG_INFO, "Warning: Reading the random source seems to have blocked.\nIf you experience problems, you probably need to find a better entropy source.");
+				already_blocked = 1;
+			}
+		}
+		readlen = read(readfd, &buf[readpos], buflen - readpos);
+		if (readlen <= 0) {
+			if (readlen < 0 && errno == EINTR) {
+				continue;
+			}
+			dropbear_exit("error reading random source");
+		}
+		readpos += readlen;
+	} while (readpos < buflen);
+
+	close (readfd);
+}
+
+/* initialise the prng from /dev/(u)random or prngd */
+void seedrandom() {
+		
+	unsigned char readbuf[INIT_SEED_SIZE];
+
+	hash_state hs;
+
+	/* initialise so that things won't warn about
+     * hashing an undefined buffer */
+	if (!donerandinit) {
+		m_burn(hashpool, sizeof(hashpool));
+	}
+
+	/* get the seed data */
+	readrand(readbuf, sizeof(readbuf));
+
+	/* hash in the new seed data */
+	sha1_init(&hs);
+	sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
+	sha1_process(&hs, (void*)readbuf, sizeof(readbuf));
+	sha1_done(&hs, hashpool);
+
+	counter = 0;
+	donerandinit = 1;
+}
+
+/* hash the current random pool with some unique identifiers
+ * for this process and point-in-time. this is used to separate
+ * the random pools for fork()ed processes. */
+void reseedrandom() {
+
+    pid_t pid;
+    struct timeval tv;
+
+	if (!donerandinit) {
+		dropbear_exit("seedrandom not done");
+	}
+
+    pid = getpid();
+    gettimeofday(&tv, NULL);
+
+	hash_state hs;
+	unsigned char hash[SHA1_HASH_SIZE];
+	sha1_init(&hs);
+	sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
+	sha1_process(&hs, (void*)&pid, sizeof(pid));
+	sha1_process(&hs, (void*)&tv, sizeof(tv));
+	sha1_done(&hs, hashpool);
+}
+
+/* return len bytes of pseudo-random data */
+void genrandom(unsigned char* buf, unsigned int len) {
+
+	hash_state hs;
+	unsigned char hash[SHA1_HASH_SIZE];
+	unsigned int copylen;
+
+	if (!donerandinit) {
+		dropbear_exit("seedrandom not done");
+	}
+
+	while (len > 0) {
+		sha1_init(&hs);
+		sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
+		sha1_process(&hs, (void*)&counter, sizeof(counter));
+		sha1_done(&hs, hash);
+
+		counter++;
+		if (counter > MAX_COUNTER) {
+			seedrandom();
+		}
+
+		copylen = MIN(len, SHA1_HASH_SIZE);
+		memcpy(buf, hash, copylen);
+		len -= copylen;
+		buf += copylen;
+	}
+	m_burn(hash, sizeof(hash));
+}
+
+/* Generates a random mp_int. 
+ * max is a *mp_int specifying an upper bound.
+ * rand must be an initialised *mp_int for the result.
+ * the result rand satisfies:  0 < rand < max 
+ * */
+void gen_random_mpint(mp_int *max, mp_int *rand) {
+
+	unsigned char *randbuf = NULL;
+	unsigned int len = 0;
+	const char masks[] = {0xff, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f};
+
+	const int size_bits = mp_count_bits(max);
+
+	len = size_bits / 8;
+	if ((size_bits % 8) != 0) {
+		len += 1;
+	}
+
+	randbuf = (unsigned char*)m_malloc(len);
+	do {
+		genrandom(randbuf, len);
+		/* Mask out the unrequired bits - mp_read_unsigned_bin expects
+		 * MSB first.*/
+		randbuf[0] &= masks[size_bits % 8];
+
+		bytes_to_mp(rand, randbuf, len);
+
+		/* keep regenerating until we get one satisfying
+		 * 0 < rand < max    */
+	} while ( ( (max != NULL) && (mp_cmp(rand, max) != MP_LT) )
+			|| (mp_cmp_d(rand, 0) != MP_GT) );
+	m_burn(randbuf, len);
+	m_free(randbuf);
+}