From 1bb941d6fcd7ac2db5a54b95ee0ed07ec9861e70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Josef=20=C5=98=C3=ADdk=C3=BD?= <jridky@redhat.com>
Date: Fri, 12 Mar 2021 10:15:30 +0100
Subject: [PATCH] Prevent parsing IP address twice (#199)

This fixes issue, that is caused by parsing IP address twice.
First as IPv4 and as IPv6 at second, even thow the address was
properly parsed as a valid IPv4 address.
---
 snmplib/transports/snmpUDPDomain.c     |  2 +-
 snmplib/transports/snmpUDPIPv6Domain.c | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/snmplib/transports/snmpUDPDomain.c b/snmplib/transports/snmpUDPDomain.c
index b96497f3a3..b594a389b9 100644
--- a/snmplib/transports/snmpUDPDomain.c
+++ b/snmplib/transports/snmpUDPDomain.c
@@ -387,7 +387,7 @@ netsnmp_udp_parse_security(const char *token, char *param)
             /* Nope, wasn't a dotted quad.  Must be a hostname. */
             int ret = netsnmp_gethostbyname_v4(sourcep, &network.s_addr);
             if (ret < 0) {
-                config_perror("cannot resolve source hostname");
+                config_perror("cannot resolve IPv4 source hostname");
                 return;
             }
         }
diff --git a/snmplib/transports/snmpUDPIPv6Domain.c b/snmplib/transports/snmpUDPIPv6Domain.c
index 238c8a9d63..7db19c5c02 100644
--- a/snmplib/transports/snmpUDPIPv6Domain.c
+++ b/snmplib/transports/snmpUDPIPv6Domain.c
@@ -736,7 +736,15 @@ netsnmp_udp6_parse_security(const char *token, char *param)
                 memset(&pton_addr.sin6_addr.s6_addr, '\0',
                        sizeof(struct in6_addr));
             } else if (inet_pton(AF_INET6, sourcep, &pton_addr.sin6_addr) != 1) {
-                /* Nope, wasn't a numeric address. Must be a hostname. */
+                /* Nope, wasn't a numeric IPv6 address. Must be IPv4 or a hostname. */
+
+                /* Try interpreting as dotted quad - IPv4 */
+                struct in_addr network;
+                if (inet_pton(AF_INET, sourcep, &network) > 0){
+                    /* Yes, it's IPv4 - so it's already parsed and we can return. */
+                    DEBUGMSGTL(("com2sec6", "IPv4 detected for IPv6 parser. Skipping.\n"));
+                    return;
+                }
 #if HAVE_GETADDRINFO
                 int             gai_error;