Change in osmocom-bb[master]: Move from libc random() to osmo_get_rand_id (2nd attempt)

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Vadim Yanitskiy gerrit-no-reply at lists.osmocom.org
Tue Jul 24 10:09:08 UTC 2018 

Vadim Yanitskiy has submitted this change and it was merged. ( https://gerrit.osmocom.org/10098 )

Change subject: Move from libc random() to osmo_get_rand_id (2nd attempt)
......................................................................

Move from libc random() to osmo_get_rand_id (2nd attempt)

When starting multiple mobile in the same second, the libc random number
generator will be seeded to exactly the same value.

The random bits inside the RACH request(s) will be exactly the same
across multiple mobile and when the channel fails they all pick the same
randomized back-off timing.

Use stronger random numbers and replace all calls to random(2) with
osmo_get_rand_id. Add a fallback to try random().

[v2: Add helper to make sure the result is int and between 0 and
RAND_MAX]

Change-Id: Icdd4be88c62bba1e9d954568e48f0c12a67ac182
---
M src/host/layer23/include/osmocom/bb/common/Makefile.am
A src/host/layer23/include/osmocom/bb/common/utils.h
M src/host/layer23/src/common/Makefile.am
A src/host/layer23/src/common/utils.c
M src/host/layer23/src/mobile/gsm322.c
M src/host/layer23/src/mobile/gsm48_mm.c
M src/host/layer23/src/mobile/gsm48_rr.c
M src/host/layer23/src/mobile/settings.c
8 files changed, 61 insertions(+), 8 deletions(-)

Approvals:
  Jenkins Builder: Verified
  Harald Welte: Looks good to me, approved
  Vadim Yanitskiy: Looks good to me, but someone else must approve



diff --git a/src/host/layer23/include/osmocom/bb/common/Makefile.am b/src/host/layer23/include/osmocom/bb/common/Makefile.am
index 945c73d..cd3437e 100644
--- a/src/host/layer23/include/osmocom/bb/common/Makefile.am
+++ b/src/host/layer23/include/osmocom/bb/common/Makefile.am
@@ -1,2 +1,2 @@
 noinst_HEADERS = l1ctl.h l1l2_interface.h l23_app.h logging.h \
-		 networks.h gps.h sysinfo.h osmocom_data.h
+		 networks.h gps.h sysinfo.h osmocom_data.h utils.h
diff --git a/src/host/layer23/include/osmocom/bb/common/utils.h b/src/host/layer23/include/osmocom/bb/common/utils.h
new file mode 100644
index 0000000..8ca61f8
--- /dev/null
+++ b/src/host/layer23/include/osmocom/bb/common/utils.h
@@ -0,0 +1,3 @@
+#pragma once
+
+int layer23_random(void);
diff --git a/src/host/layer23/src/common/Makefile.am b/src/host/layer23/src/common/Makefile.am
index 71081c0..b76094c 100644
--- a/src/host/layer23/src/common/Makefile.am
+++ b/src/host/layer23/src/common/Makefile.am
@@ -3,4 +3,4 @@
 
 noinst_LIBRARIES = liblayer23.a
 liblayer23_a_SOURCES = l1ctl.c l1l2_interface.c sap_interface.c \
-	logging.c networks.c sim.c sysinfo.c gps.c l1ctl_lapdm_glue.c
+	logging.c networks.c sim.c sysinfo.c gps.c l1ctl_lapdm_glue.c utils.c
diff --git a/src/host/layer23/src/common/utils.c b/src/host/layer23/src/common/utils.c
new file mode 100644
index 0000000..4ecb134
--- /dev/null
+++ b/src/host/layer23/src/common/utils.c
@@ -0,0 +1,47 @@
+/* Utilities used by mobile */
+
+/* (C) 2018 by Holger Hans Peter Freyther
+ *
+ * All Rights Reserved
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <osmocom/bb/common/utils.h>
+
+#include <osmocom/gsm/gsm_utils.h>
+
+#include <stdlib.h>
+#include <stdint.h>
+
+
+/**
+ * A secure replacement for random(3).
+ *
+ * \return a secure random number using osmo_get_rand_id between
+ * 0 and RAND_MAX.
+ */
+int layer23_random(void)
+{
+	unsigned int r;
+
+	if (osmo_get_rand_id((uint8_t *) &r, sizeof(r)) != 0)
+		return random();
+
+	r &= ~(1U << 31);
+	r %= RAND_MAX;
+	return (int) r;
+}
diff --git a/src/host/layer23/src/mobile/gsm322.c b/src/host/layer23/src/mobile/gsm322.c
index c3485b6..3bc8b5c 100644
--- a/src/host/layer23/src/mobile/gsm322.c
+++ b/src/host/layer23/src/mobile/gsm322.c
@@ -31,7 +31,6 @@
 #include <osmocom/core/talloc.h>
 #include <osmocom/core/utils.h>
 #include <osmocom/gsm/gsm48.h>
-#include <osmocom/gsm/gsm_utils.h>
 #include <osmocom/core/signal.h>
 
 #include <osmocom/bb/common/logging.h>
@@ -40,6 +39,7 @@
 #include <osmocom/bb/common/networks.h>
 #include <osmocom/bb/mobile/vty.h>
 #include <osmocom/bb/mobile/app_mobile.h>
+#include <osmocom/bb/common/utils.h>
 
 #include <l1ctl_proto.h>
 
@@ -959,7 +959,7 @@
 			entries++;
 	}
 	while(entries) {
-		move = random() % entries;
+		move = layer23_random() % entries;
 		i = 0;
 		llist_for_each_entry(temp, &temp_list, entry) {
 			if (rxlev2dbm(temp->rxlev) > -85) {
diff --git a/src/host/layer23/src/mobile/gsm48_mm.c b/src/host/layer23/src/mobile/gsm48_mm.c
index a7af1f5..02d861e 100644
--- a/src/host/layer23/src/mobile/gsm48_mm.c
+++ b/src/host/layer23/src/mobile/gsm48_mm.c
@@ -41,6 +41,7 @@
 #include <osmocom/bb/mobile/app_mobile.h>
 #include <osmocom/bb/mobile/primitives.h>
 #include <osmocom/bb/mobile/vty.h>
+#include <osmocom/bb/common/utils.h>
 
 extern void *l23_ctx;
 
@@ -2099,7 +2100,7 @@
 			mm->t3212.timeout.tv_sec = current_time.tv_sec
 				+ (t % s->t3212);
 		} else {
-			uint32_t rand = random();
+			uint32_t rand = layer23_random();
 
 			LOGP(DMM, LOGL_INFO, "New T3212 while timer is not "
 				"running (value %d)\n", s->t3212);
diff --git a/src/host/layer23/src/mobile/gsm48_rr.c b/src/host/layer23/src/mobile/gsm48_rr.c
index dd3fe93..c074323 100644
--- a/src/host/layer23/src/mobile/gsm48_rr.c
+++ b/src/host/layer23/src/mobile/gsm48_rr.c
@@ -79,6 +79,7 @@
 #include <osmocom/bb/common/networks.h>
 #include <osmocom/bb/common/l1ctl.h>
 #include <osmocom/bb/mobile/vty.h>
+#include <osmocom/bb/common/utils.h>
 
 #include <l1ctl_proto.h>
 
@@ -1628,7 +1629,7 @@
 		}
 	}
 
-	chan_req = random();
+	chan_req = layer23_random();
 	chan_req &= rr->chan_req_mask;
 	chan_req |= rr->chan_req_val;
 
diff --git a/src/host/layer23/src/mobile/settings.c b/src/host/layer23/src/mobile/settings.c
index 7370b0a..6a7cd81 100644
--- a/src/host/layer23/src/mobile/settings.c
+++ b/src/host/layer23/src/mobile/settings.c
@@ -25,6 +25,7 @@
 #include <osmocom/core/talloc.h>
 
 #include <osmocom/bb/mobile/app_mobile.h>
+#include <osmocom/bb/common/utils.h>
 #include <osmocom/bb/common/logging.h>
 #include <osmocom/bb/common/osmocom_data.h>
 #include <osmocom/bb/common/networks.h>
@@ -184,8 +185,8 @@
 	if (digits > 15)
 		digits = 15;
 
-	sprintf(rand, "%08ld", random() % 100000000);
-	sprintf(rand + 8, "%07ld", random() % 10000000);
+	sprintf(rand, "%08d", layer23_random() % 100000000);
+	sprintf(rand + 8, "%07d", layer23_random() % 10000000);
 
 	strcpy(set->imei + 15 - digits, rand + 15 - digits);
 	strncpy(set->imeisv, set->imei, 15);

-- 
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Gerrit-Project: osmocom-bb
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: Icdd4be88c62bba1e9d954568e48f0c12a67ac182
Gerrit-Change-Number: 10098
Gerrit-PatchSet: 4
Gerrit-Owner: Holger Freyther <holger at freyther.de>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Holger Freyther <holger at freyther.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: Vadim Yanitskiy <axilirator at gmail.com>
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