Always check if the context is available inside appl_agentx_recv().

Not every PDU goes through application.c.

OK tb@

3 files changed, 12 insertions, 4 deletions

diff --git a/usr.sbin/snmpd/application.c b/usr.sbin/snmpd/application.c
index dd92864786d..33bb8d7ceba 100644
--- a/usr.sbin/snmpd/application.c
+++ b/usr.sbin/snmpd/application.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: application.c,v 1.17 2022/12/20 20:04:55 martijn Exp $	*/
+/*	$OpenBSD: application.c,v 1.18 2023/10/24 13:28:11 martijn Exp $	*/
 
 /*
  * Copyright (c) 2021 Martijn van Duren <martijn@openbsd.org>
@@ -175,7 +175,7 @@ appl_shutdown(void)
 	}
 }
 
-static struct appl_context *
+struct appl_context *
 appl_context(const char *name, int create)
 {
 	struct appl_context *ctx;
diff --git a/usr.sbin/snmpd/application.h b/usr.sbin/snmpd/application.h
index 8b2c5678c3a..39e7b5fc410 100644
--- a/usr.sbin/snmpd/application.h
+++ b/usr.sbin/snmpd/application.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: application.h,v 1.5 2022/09/01 14:34:17 martijn Exp $	*/
+/*	$OpenBSD: application.h,v 1.6 2023/10/24 13:28:11 martijn Exp $	*/
 
 /*
  * Copyright (c) 2021 Martijn van Duren <martijn@openbsd.org>
@@ -88,6 +88,7 @@ struct appl_varbind {
 struct snmp_message;
 enum snmp_version;
 struct appl_backend;
+struct appl_context;
 
 struct appl_backend_functions {
 	void (*ab_close)(struct appl_backend *, enum appl_close_reason);
@@ -121,6 +122,7 @@ struct appl_backend {
 void appl(void);
 void appl_init(void);
 void appl_shutdown(void);
+struct appl_context *appl_context(const char *, int);
 enum appl_error appl_register(const char *, uint32_t, uint8_t, struct ber_oid *,
     int, int, uint8_t, uint32_t, struct appl_backend *);
 enum appl_error appl_unregister(const char *, uint8_t, struct ber_oid *,
diff --git a/usr.sbin/snmpd/application_agentx.c b/usr.sbin/snmpd/application_agentx.c
index 3a67f9dc0f1..81b37bd9280 100644
--- a/usr.sbin/snmpd/application_agentx.c
+++ b/usr.sbin/snmpd/application_agentx.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: application_agentx.c,v 1.7 2023/10/24 12:57:40 martijn Exp $ */
+/*	$OpenBSD: application_agentx.c,v 1.8 2023/10/24 13:28:11 martijn Exp $ */
 /*
  * Copyright (c) 2022 Martijn van Duren <martijn@openbsd.org>
  *
@@ -370,6 +370,12 @@ appl_agentx_recv(int fd, short event, void *cookie)
 			error = APPL_ERROR_PARSEERROR;
 			goto fail;
 		}
+		if (appl_context(pdu->ap_context.aos_string, 0) == NULL) {
+			log_warnx("%s: %s: Unsupported context",
+			    name, ax_pdutype2string(pdu->ap_header.aph_flags));
+			error = APPL_ERROR_UNSUPPORTEDCONTEXT;
+			goto fail;
+		}
 	}
 	switch (pdu->ap_header.aph_type) {
 	case AX_PDU_TYPE_OPEN: