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From d13302656d9ff0807c5defe18623adc947f43a2b Mon Sep 17 00:00:00 2001
From: Narpat Mali <narpat.mali@windriver.com>
Date: Wed, 8 Feb 2023 13:15:39 +0000
Subject: [PATCH] agent: Disallow SET requests with any NULL varbind Merge pull
request #490 from fenner/set-null
fixes: #474 and #475
CVE: CVE-2022-44792, CVE-2022-44793
Upstream-Status: Backport [https://github.com/net-snmp/net-snmp/commit/be804106fd0771a7d05236cff36e199af077af57]
Signed-off-by: Narpat Mali <narpat.mali@windriver.com>
---
agent/snmp_agent.c | 32 +++++++++++++++++++
apps/snmpset.c | 1 +
.../default/T0142snmpv2csetnull_simple | 31 ++++++++++++++++++
3 files changed, 64 insertions(+)
create mode 100644 testing/fulltests/default/T0142snmpv2csetnull_simple
diff --git a/agent/snmp_agent.c b/agent/snmp_agent.c
index 867d0c1..3f678fe 100644
--- a/agent/snmp_agent.c
+++ b/agent/snmp_agent.c
@@ -3719,12 +3719,44 @@ netsnmp_handle_request(netsnmp_agent_session *asp, int status)
return 1;
}
+static int
+check_set_pdu_for_null_varbind(netsnmp_agent_session *asp)
+{
+ int i;
+ netsnmp_variable_list *v = NULL;
+
+ for (i = 1, v = asp->pdu->variables; v != NULL; i++, v = v->next_variable) {
+ if (v->type == ASN_NULL) {
+ /*
+ * Protect SET implementations that do not protect themselves
+ * against wrong type.
+ */
+ DEBUGMSGTL(("snmp_agent", "disallowing SET with NULL var for varbind %d\n", i));
+ asp->index = i;
+ return SNMP_ERR_WRONGTYPE;
+ }
+ }
+ return SNMP_ERR_NOERROR;
+}
+
int
handle_pdu(netsnmp_agent_session *asp)
{
int status, inclusives = 0;
netsnmp_variable_list *v = NULL;
+#ifndef NETSNMP_NO_WRITE_SUPPORT
+ /*
+ * Check for ASN_NULL in SET request
+ */
+ if (asp->pdu->command == SNMP_MSG_SET) {
+ status = check_set_pdu_for_null_varbind(asp);
+ if (status != SNMP_ERR_NOERROR) {
+ return status;
+ }
+ }
+#endif /* NETSNMP_NO_WRITE_SUPPORT */
+
/*
* for illegal requests, mark all nodes as ASN_NULL
*/
diff --git a/apps/snmpset.c b/apps/snmpset.c
index 48e14bd..d542713 100644
--- a/apps/snmpset.c
+++ b/apps/snmpset.c
@@ -182,6 +182,7 @@ main(int argc, char *argv[])
case 'x':
case 'd':
case 'b':
+ case 'n': /* undocumented */
#ifdef NETSNMP_WITH_OPAQUE_SPECIAL_TYPES
case 'I':
case 'U':
diff --git a/testing/fulltests/default/T0142snmpv2csetnull_simple b/testing/fulltests/default/T0142snmpv2csetnull_simple
new file mode 100644
index 0000000..0f1b8f3
--- /dev/null
+++ b/testing/fulltests/default/T0142snmpv2csetnull_simple
@@ -0,0 +1,31 @@
+#!/bin/sh
+
+. ../support/simple_eval_tools.sh
+
+HEADER SNMPv2c set of system.sysContact.0 with NULL varbind
+
+SKIPIF NETSNMP_DISABLE_SET_SUPPORT
+SKIPIF NETSNMP_NO_WRITE_SUPPORT
+SKIPIF NETSNMP_DISABLE_SNMPV2C
+SKIPIFNOT USING_MIBII_SYSTEM_MIB_MODULE
+
+#
+# Begin test
+#
+
+# standard V2C configuration: testcomunnity
+snmp_write_access='all'
+. ./Sv2cconfig
+STARTAGENT
+
+CAPTURE "snmpget -On $SNMP_FLAGS -c testcommunity -v 2c $SNMP_TRANSPORT_SPEC:$SNMP_TEST_DEST$SNMP_SNMPD_PORT .1.3.6.1.2.1.1.4.0"
+
+CHECK ".1.3.6.1.2.1.1.4.0 = STRING:"
+
+CAPTURE "snmpset -On $SNMP_FLAGS -c testcommunity -v 2c $SNMP_TRANSPORT_SPEC:$SNMP_TEST_DEST$SNMP_SNMPD_PORT .1.3.6.1.2.1.1.4.0 n x"
+
+CHECK "Reason: wrongType"
+
+STOPAGENT
+
+FINISHED
--
2.34.1
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