On Thu, 2022-03-31 at 16:32 +0200, Peter Eisentraut wrote:
> Why add a (failry complicated) pg_inet_pton() when a perfectly
> reasonable inet_pton() exists?

I think it was mostly just that inet_aton() and pg_inet_net_ntop() both
had ports, and I figured I might as well port the other one since we
already had the implementation. (I don't have a good intuition yet for
the community's preference for port vs dependency.)

> I would get rid of all that refactoring and just have your code call
> inet_pton()/inet_ntop() directly.
> 
> If you're worried about portability, and you don't want to go through
> the effort of proving libpgport substitutes, just have your code raise
> an error in the "#else" code paths.  We can fill that in later if there
> is demand.

Switched to inet_pton() in v12, with no #if/else for now. I think this
should work with Winsock as-is; let's see if the bot agrees...

Thanks,
--Jacob
From a973663f1b4b98a427692bb6291ddc2c3ce9bb4f Mon Sep 17 00:00:00 2001
From: Jacob Champion <pchamp...@vmware.com>
Date: Thu, 18 Nov 2021 15:36:18 -0800
Subject: [PATCH v12] libpq: allow IP address SANs in server certs

The current implementation supports exactly one IP address in a server
certificate's Common Name, which is brittle (the strings must match
exactly).  This patch adds support for IPv4 and IPv6 addresses in a
server's Subject Alternative Names.

Per discussion on-list:

- If the client's expected host is an IP address, we allow fallback to
  the Subject Common Name if an iPAddress SAN is not present, even if
  a dNSName is present. This matches the behavior of NSS, in violation
  of the relevant RFCs.

- We also, counter-intuitively, match IP addresses embedded in dNSName
  SANs. From inspection this appears to have been the behavior since the
  SAN matching feature was introduced in acd08d76.

- Unlike NSS, we don't map IPv4 to IPv6 addresses, or vice-versa.

- Move PGSQL_AF_INET* to inet-common.h to reduce copy-paste.

Co-authored-by: Kyotaro Horiguchi <horikyota....@gmail.com>
Co-authored-by: Daniel Gustafsson <dan...@yesql.se>
---
 doc/src/sgml/libpq.sgml                       |  21 ++-
 src/backend/utils/adt/inet_net_pton.c         |   2 +-
 src/include/common/inet-common.h              |  35 +++++
 src/include/utils/inet.h                      |  13 +-
 src/interfaces/libpq/fe-secure-common.c       |  99 +++++++++++++
 src/interfaces/libpq/fe-secure-common.h       |   4 +
 src/interfaces/libpq/fe-secure-openssl.c      | 139 ++++++++++++++++--
 src/port/inet_net_ntop.c                      |  12 +-
 .../conf/server-cn-and-ip-alt-names.config    |  24 +++
 src/test/ssl/conf/server-ip-alt-names.config  |  19 +++
 .../conf/server-ip-cn-and-alt-names.config    |  21 +++
 .../server-ip-cn-and-dns-alt-names.config     |  21 +++
 src/test/ssl/conf/server-ip-cn-only.config    |  12 ++
 src/test/ssl/conf/server-ip-in-dnsname.config |  18 +++
 .../ssl/ssl/server-cn-and-ip-alt-names.crt    |  20 +++
 .../ssl/ssl/server-cn-and-ip-alt-names.key    |  27 ++++
 src/test/ssl/ssl/server-ip-alt-names.crt      |  19 +++
 src/test/ssl/ssl/server-ip-alt-names.key      |  27 ++++
 .../ssl/ssl/server-ip-cn-and-alt-names.crt    |  19 +++
 .../ssl/ssl/server-ip-cn-and-alt-names.key    |  27 ++++
 .../ssl/server-ip-cn-and-dns-alt-names.crt    |  20 +++
 .../ssl/server-ip-cn-and-dns-alt-names.key    |  27 ++++
 src/test/ssl/ssl/server-ip-cn-only.crt        |  18 +++
 src/test/ssl/ssl/server-ip-cn-only.key        |  27 ++++
 src/test/ssl/ssl/server-ip-in-dnsname.crt     |  18 +++
 src/test/ssl/ssl/server-ip-in-dnsname.key     |  27 ++++
 src/test/ssl/sslfiles.mk                      |   6 +
 src/test/ssl/t/001_ssltests.pl                | 110 +++++++++++++-
 28 files changed, 791 insertions(+), 41 deletions(-)
 create mode 100644 src/include/common/inet-common.h
 create mode 100644 src/test/ssl/conf/server-cn-and-ip-alt-names.config
 create mode 100644 src/test/ssl/conf/server-ip-alt-names.config
 create mode 100644 src/test/ssl/conf/server-ip-cn-and-alt-names.config
 create mode 100644 src/test/ssl/conf/server-ip-cn-and-dns-alt-names.config
 create mode 100644 src/test/ssl/conf/server-ip-cn-only.config
 create mode 100644 src/test/ssl/conf/server-ip-in-dnsname.config
 create mode 100644 src/test/ssl/ssl/server-cn-and-ip-alt-names.crt
 create mode 100644 src/test/ssl/ssl/server-cn-and-ip-alt-names.key
 create mode 100644 src/test/ssl/ssl/server-ip-alt-names.crt
 create mode 100644 src/test/ssl/ssl/server-ip-alt-names.key
 create mode 100644 src/test/ssl/ssl/server-ip-cn-and-alt-names.crt
 create mode 100644 src/test/ssl/ssl/server-ip-cn-and-alt-names.key
 create mode 100644 src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.crt
 create mode 100644 src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.key
 create mode 100644 src/test/ssl/ssl/server-ip-cn-only.crt
 create mode 100644 src/test/ssl/ssl/server-ip-cn-only.key
 create mode 100644 src/test/ssl/ssl/server-ip-in-dnsname.crt
 create mode 100644 src/test/ssl/ssl/server-ip-in-dnsname.key

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 0b2a8720f0..b785008045 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -8356,16 +8356,31 @@ ldap://ldap.acme.com/cn=dbserver,cn=hosts?pgconnectinfo?base?(objectclass=*)
 
   <para>
    In <literal>verify-full</literal> mode, the host name is matched against the
-   certificate's Subject Alternative Name attribute(s), or against the
-   Common Name attribute if no Subject Alternative Name of type <literal>dNSName</literal> is
+   certificate's Subject Alternative Name attribute(s) (SAN), or against the
+   Common Name attribute if no SAN of type <literal>dNSName</literal> is
    present.  If the certificate's name attribute starts with an asterisk
    (<literal>*</literal>), the asterisk will be treated as
    a wildcard, which will match all characters <emphasis>except</emphasis> a dot
    (<literal>.</literal>). This means the certificate will not match subdomains.
    If the connection is made using an IP address instead of a host name, the
-   IP address will be matched (without doing any DNS lookups).
+   IP address will be matched (without doing any DNS lookups) against SANs of
+   type <literal>iPAddress</literal> or <literal>dNSName</literal>.  If no
+   <literal>iPAddress</literal> SAN is present and no
+   matching <literal>dNSName</literal> SAN is present, the host IP address is
+   matched against the Common Name attribute.
   </para>
 
+  <note>
+    <para>
+      For backward compatibility with earlier versions of PostgreSQL, the host
+      IP address is verified in a manner different
+      from <ulink url="https://tools.ietf.org/html/rfc6125";>RFC 6125</ulink>.
+      The host IP address is always matched against <literal>dNSName</literal>
+      SANs as well as <literal>iPAddress</literal> SANs, and can be matched
+      against the Common Name attribute if no relevant SANs exist.
+   </para>
+  </note>
+
   <para>
    To allow server certificate verification, one or more root certificates
    must be placed in the file <filename>~/.postgresql/root.crt</filename>
diff --git a/src/backend/utils/adt/inet_net_pton.c b/src/backend/utils/adt/inet_net_pton.c
index d3221a1313..7752012ad9 100644
--- a/src/backend/utils/adt/inet_net_pton.c
+++ b/src/backend/utils/adt/inet_net_pton.c
@@ -29,9 +29,9 @@ static const char rcsid[] = "Id: inet_net_pton.c,v 1.4.2.3 2004/03/17 00:40:11 m
 #include <assert.h>
 #include <ctype.h>
 
+#include "common/inet-common.h"
 #include "utils/builtins.h" /* pgrminclude ignore */	/* needed on some
 														 * platforms */
-#include "utils/inet.h"
 
 
 static int	inet_net_pton_ipv4(const char *src, u_char *dst);
diff --git a/src/include/common/inet-common.h b/src/include/common/inet-common.h
new file mode 100644
index 0000000000..3ad72261b6
--- /dev/null
+++ b/src/include/common/inet-common.h
@@ -0,0 +1,35 @@
+/*-------------------------------------------------------------------------
+ *
+ * inet-common.h
+ *
+ *	  Common code for clients of the inet_* APIs.
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/common/inet-common.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef INET_COMMON_H
+#define INET_COMMON_H
+
+/*
+ * We use these values for the "family" field of inet_struct.
+ *
+ * Referencing all of the non-AF_INET types to AF_INET lets us work on
+ * machines which may not have the appropriate address family (like
+ * inet6 addresses when AF_INET6 isn't present) but doesn't cause a
+ * dump/reload requirement.  Pre-7.4 databases used AF_INET for the family
+ * type on disk.
+ *
+ * In a frontend build, we can't include inet.h, but we still need to have
+ * sensible definitions of these two constants.  (Frontend clients should
+ * include this header directly.)  Note that pg_inet_net_ntop()
+ * assumes that PGSQL_AF_INET is equal to AF_INET.
+ */
+#define PGSQL_AF_INET	(AF_INET + 0)
+#define PGSQL_AF_INET6	(AF_INET + 1)
+
+#endif							/* INET_COMMON_H */
diff --git a/src/include/utils/inet.h b/src/include/utils/inet.h
index 3073c0307e..c56c016987 100644
--- a/src/include/utils/inet.h
+++ b/src/include/utils/inet.h
@@ -14,6 +14,7 @@
 #ifndef INET_H
 #define INET_H
 
+#include "common/inet-common.h"
 #include "fmgr.h"
 
 /*
@@ -27,18 +28,6 @@ typedef struct
 	unsigned char ipaddr[16];	/* up to 128 bits of address */
 } inet_struct;
 
-/*
- * We use these values for the "family" field.
- *
- * Referencing all of the non-AF_INET types to AF_INET lets us work on
- * machines which may not have the appropriate address family (like
- * inet6 addresses when AF_INET6 isn't present) but doesn't cause a
- * dump/reload requirement.  Pre-7.4 databases used AF_INET for the family
- * type on disk.
- */
-#define PGSQL_AF_INET	(AF_INET + 0)
-#define PGSQL_AF_INET6	(AF_INET + 1)
-
 /*
  * Both INET and CIDR addresses are represented within Postgres as varlena
  * objects, ie, there is a varlena header in front of the struct type
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index bd46f08fae..6628eb8318 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -19,9 +19,13 @@
 
 #include "postgres_fe.h"
 
+#include <arpa/inet.h>
+
+#include "common/inet-common.h"
 #include "fe-secure-common.h"
 
 #include "libpq-int.h"
+#include "port.h"
 #include "pqexpbuffer.h"
 
 /*
@@ -144,6 +148,101 @@ pq_verify_peer_name_matches_certificate_name(PGconn *conn,
 	return result;
 }
 
+/*
+ * Check if an IP address from a server's certificate matches the peer's
+ * hostname (which must itself be an IPv4/6 address).
+ *
+ * Returns 1 if the address matches, and 0 if it does not. On error, returns
+ * -1, and sets the libpq error message.
+ *
+ * A string representation of the certificate's IP address is returned in
+ * *store_name. The caller is responsible for freeing it.
+ */
+int
+pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
+										   const unsigned char *ipdata,
+										   size_t iplen,
+										   char **store_name)
+{
+	char	   *addrstr;
+	int			match = 0;
+	char	   *host = conn->connhost[conn->whichhost].host;
+	int			family;
+	char		tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
+	char		sebuf[PG_STRERROR_R_BUFLEN];
+
+	*store_name = NULL;
+
+	if (!(host && host[0] != '\0'))
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("host name must be specified\n"));
+		return -1;
+	}
+
+	/*
+	 * The data from the certificate is in network byte order. Convert our host
+	 * string to network-ordered bytes as well, for comparison. (The host string
+	 * isn't guaranteed to actually be an IP address, so if this conversion
+	 * fails we need to consider it a mismatch rather than an error.)
+	 */
+	if (iplen == 4)
+	{
+		/* IPv4 */
+		struct in_addr addr;
+
+		family = PGSQL_AF_INET;
+
+		/*
+		 * The use of inet_aton() is deliberate; we accept alternative IPv4
+		 * address notations that are accepted by inet_aton() but not
+		 * inet_pton() as server addresses.
+		 */
+		if (inet_aton(host, &addr))
+		{
+			if (memcmp(ipdata, &addr.s_addr, iplen) == 0)
+				match = 1;
+		}
+	}
+	else if (iplen == 16)
+	{
+		/* IPv6 */
+		struct in6_addr addr;
+
+		family = PGSQL_AF_INET6;
+
+		if (inet_pton(AF_INET6, host, &addr) == 1)
+		{
+			if (memcmp(ipdata, &addr.s6_addr, iplen) == 0)
+				match = 1;
+		}
+	}
+	else
+	{
+		/*
+		 * Not IPv4 or IPv6. We could ignore the field, but leniency seems wrong
+		 * given the subject matter.
+		 */
+		appendPQExpBuffer(&conn->errorMessage,
+						  libpq_gettext("certificate contains IP address with invalid length %lu\n"),
+						  (unsigned long) iplen);
+		return -1;
+	}
+
+	/* Generate a human-readable representation of the certificate's IP. */
+	addrstr = pg_inet_net_ntop(family, ipdata, 8 * iplen, tmp, sizeof(tmp));
+	if (!addrstr)
+	{
+		appendPQExpBuffer(&conn->errorMessage,
+						  libpq_gettext("could not convert certificate's IP address to string: %s\n"),
+						  strerror_r(errno, sebuf, sizeof(sebuf)));
+		return -1;
+	}
+
+	*store_name = strdup(addrstr);
+	return match;
+}
+
 /*
  * Verify that the server certificate matches the hostname we connected to.
  *
diff --git a/src/interfaces/libpq/fe-secure-common.h b/src/interfaces/libpq/fe-secure-common.h
index 1cca6d785a..d18db7138c 100644
--- a/src/interfaces/libpq/fe-secure-common.h
+++ b/src/interfaces/libpq/fe-secure-common.h
@@ -21,6 +21,10 @@
 extern int	pq_verify_peer_name_matches_certificate_name(PGconn *conn,
 														 const char *namedata, size_t namelen,
 														 char **store_name);
+extern int	pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
+													   const unsigned char *addrdata,
+													   size_t addrlen,
+													   char **store_name);
 extern bool pq_verify_peer_name_matches_certificate(PGconn *conn);
 
 #endif							/* FE_SECURE_COMMON_H */
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 0cba5c5cf2..1828a3cb8c 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -26,6 +26,7 @@
 #include <fcntl.h>
 #include <ctype.h>
 
+#include "common/inet-common.h"
 #include "libpq-fe.h"
 #include "fe-auth.h"
 #include "fe-secure-common.h"
@@ -72,6 +73,9 @@ static int	verify_cb(int ok, X509_STORE_CTX *ctx);
 static int	openssl_verify_peer_name_matches_certificate_name(PGconn *conn,
 															  ASN1_STRING *name,
 															  char **store_name);
+static int	openssl_verify_peer_name_matches_certificate_ip(PGconn *conn,
+															ASN1_OCTET_STRING *addr_entry,
+															char **store_name);
 static void destroy_ssl_system(void);
 static int	initialize_SSL(PGconn *conn);
 static PostgresPollingStatusType open_client_SSL(PGconn *);
@@ -509,6 +513,51 @@ openssl_verify_peer_name_matches_certificate_name(PGconn *conn, ASN1_STRING *nam
 	return pq_verify_peer_name_matches_certificate_name(conn, (const char *) namedata, len, store_name);
 }
 
+/*
+ * OpenSSL-specific wrapper around
+ * pq_verify_peer_name_matches_certificate_ip(), converting the
+ * ASN1_OCTET_STRING into a plain C string.
+ */
+static int
+openssl_verify_peer_name_matches_certificate_ip(PGconn *conn,
+												ASN1_OCTET_STRING *addr_entry,
+												char **store_name)
+{
+	int			len;
+	const unsigned char *addrdata;
+
+	/* Should not happen... */
+	if (addr_entry == NULL)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("SSL certificate's address entry is missing\n"));
+		return -1;
+	}
+
+	/*
+	 * GEN_IPADD is an OCTET STRING containing an IP address in network byte
+	 * order.
+	 */
+#ifdef HAVE_ASN1_STRING_GET0_DATA
+	addrdata = ASN1_STRING_get0_data(addr_entry);
+#else
+	addrdata = ASN1_STRING_data(addr_entry);
+#endif
+	len = ASN1_STRING_length(addr_entry);
+
+	return pq_verify_peer_name_matches_certificate_ip(conn, addrdata, len, store_name);
+}
+
+static bool
+is_ip_address(const char *host)
+{
+	struct in_addr	dummy4;
+	struct in6_addr	dummy6;
+
+	return inet_aton(host, &dummy4)
+		|| (inet_pton(AF_INET6, host, &dummy6) == 1);
+}
+
 /*
  *	Verify that the server certificate matches the hostname we connected to.
  *
@@ -522,6 +571,36 @@ pgtls_verify_peer_name_matches_certificate_guts(PGconn *conn,
 	STACK_OF(GENERAL_NAME) * peer_san;
 	int			i;
 	int			rc = 0;
+	char	   *host = conn->connhost[conn->whichhost].host;
+	int			host_type;
+	bool		check_cn = true;
+
+	Assert(host && host[0]); /* should be guaranteed by caller */
+
+	/*
+	 * We try to match the NSS behavior here, which is a slight departure from
+	 * the spec but seems to make more intuitive sense:
+	 *
+	 * If connhost contains a DNS name, and the certificate's SANs contain any
+	 * dNSName entries, then we'll ignore the Subject Common Name entirely;
+	 * otherwise, we fall back to checking the CN. (This behavior matches the
+	 * RFC.)
+	 *
+	 * If connhost contains an IP address, and the SANs contain iPAddress
+	 * entries, we again ignore the CN. Otherwise, we allow the CN to match,
+	 * EVEN IF there is a dNSName in the SANs. (RFC 6125 prohibits this: "A
+	 * client MUST NOT seek a match for a reference identifier of CN-ID if the
+	 * presented identifiers include a DNS-ID, SRV-ID, URI-ID, or any
+	 * application-specific identifier types supported by the client.")
+	 *
+	 * NOTE: Prior versions of libpq did not consider iPAddress entries at all,
+	 * so this new behavior might break a certificate that has different IP
+	 * addresses in the Subject CN and the SANs.
+	 */
+	if (is_ip_address(host))
+		host_type = GEN_IPADD;
+	else
+		host_type = GEN_DNS;
 
 	/*
 	 * First, get the Subject Alternative Names (SANs) from the certificate,
@@ -537,38 +616,62 @@ pgtls_verify_peer_name_matches_certificate_guts(PGconn *conn,
 		for (i = 0; i < san_len; i++)
 		{
 			const GENERAL_NAME *name = sk_GENERAL_NAME_value(peer_san, i);
+			char	   *alt_name = NULL;
 
-			if (name->type == GEN_DNS)
+			if (name->type == host_type)
 			{
-				char	   *alt_name;
+				/*
+				 * This SAN is of the same type (IP or DNS) as our host name, so
+				 * don't allow a fallback check of the CN.
+				 */
+				check_cn = false;
+			}
 
+			if (name->type == GEN_DNS)
+			{
 				(*names_examined)++;
 				rc = openssl_verify_peer_name_matches_certificate_name(conn,
 																	   name->d.dNSName,
 																	   &alt_name);
+			}
+			else if (name->type == GEN_IPADD)
+			{
+				(*names_examined)++;
+				rc = openssl_verify_peer_name_matches_certificate_ip(conn,
+																	 name->d.iPAddress,
+																	 &alt_name);
+			}
 
-				if (alt_name)
-				{
-					if (!*first_name)
-						*first_name = alt_name;
-					else
-						free(alt_name);
-				}
+			if (alt_name)
+			{
+				if (!*first_name)
+					*first_name = alt_name;
+				else
+					free(alt_name);
 			}
+
 			if (rc != 0)
+			{
+				/*
+				 * Either we hit an error or a match, and either way we should
+				 * not fall back to the CN.
+				 */
+				check_cn = false;
 				break;
+			}
 		}
 		sk_GENERAL_NAME_pop_free(peer_san, GENERAL_NAME_free);
 	}
 
 	/*
-	 * If there is no subjectAltName extension of type dNSName, check the
+	 * If there is no subjectAltName extension of the matching type, check the
 	 * Common Name.
 	 *
 	 * (Per RFC 2818 and RFC 6125, if the subjectAltName extension of type
-	 * dNSName is present, the CN must be ignored.)
+	 * dNSName is present, the CN must be ignored. We break this rule if host is
+	 * an IP address; see the comment above.)
 	 */
-	if (*names_examined == 0)
+	if (check_cn)
 	{
 		X509_NAME  *subject_name;
 
@@ -581,10 +684,20 @@ pgtls_verify_peer_name_matches_certificate_guts(PGconn *conn,
 												  NID_commonName, -1);
 			if (cn_index >= 0)
 			{
+				char   *common_name = NULL;
+
 				(*names_examined)++;
 				rc = openssl_verify_peer_name_matches_certificate_name(conn,
 																	   X509_NAME_ENTRY_get_data(X509_NAME_get_entry(subject_name, cn_index)),
-																	   first_name);
+																	   &common_name);
+
+				if (common_name)
+				{
+					if (!*first_name)
+						*first_name = common_name;
+					else
+						free(common_name);
+				}
 			}
 		}
 	}
diff --git a/src/port/inet_net_ntop.c b/src/port/inet_net_ntop.c
index b8ad69c390..af28056132 100644
--- a/src/port/inet_net_ntop.c
+++ b/src/port/inet_net_ntop.c
@@ -31,17 +31,7 @@ static const char rcsid[] = "Id: inet_net_ntop.c,v 1.1.2.2 2004/03/09 09:17:27 m
 #include <netinet/in.h>
 #include <arpa/inet.h>
 
-#ifndef FRONTEND
-#include "utils/inet.h"
-#else
-/*
- * In a frontend build, we can't include inet.h, but we still need to have
- * sensible definitions of these two constants.  Note that pg_inet_net_ntop()
- * assumes that PGSQL_AF_INET is equal to AF_INET.
- */
-#define PGSQL_AF_INET	(AF_INET + 0)
-#define PGSQL_AF_INET6	(AF_INET + 1)
-#endif
+#include "common/inet-common.h"
 
 
 #define NS_IN6ADDRSZ 16
diff --git a/src/test/ssl/conf/server-cn-and-ip-alt-names.config b/src/test/ssl/conf/server-cn-and-ip-alt-names.config
new file mode 100644
index 0000000000..a6fa09bad3
--- /dev/null
+++ b/src/test/ssl/conf/server-cn-and-ip-alt-names.config
@@ -0,0 +1,24 @@
+# An OpenSSL format CSR config file for creating a server certificate.
+#
+# This certificate contains a CN and SANs for both IPv4 and IPv6.
+
+
+[ req ]
+distinguished_name     = req_distinguished_name
+req_extensions         = v3_req
+prompt                 = no
+
+[ req_distinguished_name ]
+# Note: According to RFC 2818 and 6125, the CN is ignored, when DNS names are
+# present in the SANs. But they are silent on whether the CN is checked when IP
+# addresses are present.
+CN = common-name.pg-ssltest.test
+OU = PostgreSQL test suite
+
+# For Subject Alternative Names
+[ v3_req ]
+subjectAltName = @alt_names
+
+[ alt_names ]
+IP.1 = 192.0.2.1
+IP.2 = 2001:DB8::1
diff --git a/src/test/ssl/conf/server-ip-alt-names.config b/src/test/ssl/conf/server-ip-alt-names.config
new file mode 100644
index 0000000000..c22f22951a
--- /dev/null
+++ b/src/test/ssl/conf/server-ip-alt-names.config
@@ -0,0 +1,19 @@
+# An OpenSSL format CSR config file for creating a server certificate.
+#
+# This certificate has a two IP-address SANs, and no CN.
+
+[ req ]
+distinguished_name     = req_distinguished_name
+req_extensions         = v3_req
+prompt                 = no
+
+[ req_distinguished_name ]
+OU = PostgreSQL test suite
+
+# For Subject Alternative Names
+[ v3_req ]
+subjectAltName = @alt_names
+
+[ alt_names ]
+IP.1 = 192.0.2.1
+IP.2 = 2001:DB8::1
diff --git a/src/test/ssl/conf/server-ip-cn-and-alt-names.config b/src/test/ssl/conf/server-ip-cn-and-alt-names.config
new file mode 100644
index 0000000000..a4087f0a18
--- /dev/null
+++ b/src/test/ssl/conf/server-ip-cn-and-alt-names.config
@@ -0,0 +1,21 @@
+# An OpenSSL format CSR config file for creating a server certificate.
+#
+# This certificate contains both a CN and SANs in IP address format.
+
+
+[ req ]
+distinguished_name     = req_distinguished_name
+req_extensions         = v3_req
+prompt                 = no
+
+[ req_distinguished_name ]
+CN = 192.0.2.1
+OU = PostgreSQL test suite
+
+# For Subject Alternative Names
+[ v3_req ]
+subjectAltName = @alt_names
+
+[ alt_names ]
+IP.1 = 192.0.2.2
+IP.2 = 2001:DB8::1
diff --git a/src/test/ssl/conf/server-ip-cn-and-dns-alt-names.config b/src/test/ssl/conf/server-ip-cn-and-dns-alt-names.config
new file mode 100644
index 0000000000..7121803b49
--- /dev/null
+++ b/src/test/ssl/conf/server-ip-cn-and-dns-alt-names.config
@@ -0,0 +1,21 @@
+# An OpenSSL format CSR config file for creating a server certificate.
+#
+# This certificate contains both a CN and SANs in IP address format.
+
+
+[ req ]
+distinguished_name     = req_distinguished_name
+req_extensions         = v3_req
+prompt                 = no
+
+[ req_distinguished_name ]
+CN = 192.0.2.1
+OU = PostgreSQL test suite
+
+# For Subject Alternative Names
+[ v3_req ]
+subjectAltName = @alt_names
+
+[ alt_names ]
+DNS.1 = dns1.alt-name.pg-ssltest.test
+DNS.2 = dns2.alt-name.pg-ssltest.test
diff --git a/src/test/ssl/conf/server-ip-cn-only.config b/src/test/ssl/conf/server-ip-cn-only.config
new file mode 100644
index 0000000000..585d8bdae8
--- /dev/null
+++ b/src/test/ssl/conf/server-ip-cn-only.config
@@ -0,0 +1,12 @@
+# An OpenSSL format CSR config file for creating a server certificate.
+#
+
+[ req ]
+distinguished_name     = req_distinguished_name
+prompt                 = no
+
+[ req_distinguished_name ]
+CN = 192.0.2.1
+OU = PostgreSQL test suite
+
+# No Subject Alternative Names
diff --git a/src/test/ssl/conf/server-ip-in-dnsname.config b/src/test/ssl/conf/server-ip-in-dnsname.config
new file mode 100644
index 0000000000..b15649aef7
--- /dev/null
+++ b/src/test/ssl/conf/server-ip-in-dnsname.config
@@ -0,0 +1,18 @@
+# An OpenSSL format CSR config file for creating a server certificate.
+#
+
+[ req ]
+distinguished_name     = req_distinguished_name
+req_extensions         = v3_req
+prompt                 = no
+
+[ req_distinguished_name ]
+OU = PostgreSQL test suite
+
+# For Subject Alternative Names
+[ v3_req ]
+subjectAltName = @alt_names
+
+# Normally IP addresses should not go into a dNSName.
+[ alt_names ]
+DNS.1 = 192.0.2.1
diff --git a/src/test/ssl/ssl/server-cn-and-ip-alt-names.crt b/src/test/ssl/ssl/server-cn-and-ip-alt-names.crt
new file mode 100644
index 0000000000..4e58c85ccb
--- /dev/null
+++ b/src/test/ssl/ssl/server-cn-and-ip-alt-names.crt
@@ -0,0 +1,20 @@
+-----BEGIN CERTIFICATE-----
+MIIDLzCCAhegAwIBAgIIICERKRE1UQAwDQYJKoZIhvcNAQELBQAwQjFAMD4GA1UE
+Aww3VGVzdCBDQSBmb3IgUG9zdGdyZVNRTCBTU0wgcmVncmVzc2lvbiB0ZXN0IHNl
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+0WB9akxMi2NxwS2+BQ4k/McPlwIDAQABoyUwIzAhBgNVHREEGjAYhwTAAAIBhxAg
+AQ24AAAAAAAAAAAAAAABMA0GCSqGSIb3DQEBCwUAA4IBAQAQLo2RzC07dG9p+J3A
+W6C0p3Y+Os/YE2D9wfp4TIDTZxcRUQZ0S6ahF1N6sp8l9KHBJHPU1cUpRAU1oD+Y
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+kH+HswajhdpdnZIgh0FYTlTCPILDrB49aOWwqLa54AUA6WXa35hPsP8SoqL9Eucq
+ifPhBYyadsjOb+70N8GbbAsDPN1jCX9L8RuNcEkxSCKCYx91cWXh7K5KMPuGlzB7
+j8xB
+-----END CERTIFICATE-----
diff --git a/src/test/ssl/ssl/server-cn-and-ip-alt-names.key b/src/test/ssl/ssl/server-cn-and-ip-alt-names.key
new file mode 100644
index 0000000000..837eef996d
--- /dev/null
+++ b/src/test/ssl/ssl/server-cn-and-ip-alt-names.key
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----
+MIIEpAIBAAKCAQEA6+8IYKAFnZ7V+fDo1cyMpbGBLzCfJOQ/1o2jOGP4+GjpsZgv
+6S6UT2MheC8MiiEFrYwdsSIZyYc3jEZrluy/UuR0bCGtqU92BCqa0iBLhvHOgjR5
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+cG5kehboPf86vxBt3iHByrU/9/DY5IvQCfSXVNa6rb5w5/pGja9aCei6Mv1jQY/V
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+j2aFi81A4VptNPjLGNblAKhMGnhp7UUzspeRQYuNoSFcnpxoDKtrvK/OIq/pQeBh
+AIfECHRDh+yEG32Tb44FuPQkB1eTYl8xbMEImrhNUaSjJk7tTsmydHy0DjmqHVKX
+HUj0TREfDBDOBiHtY0XV6Pu3bnqDH/TKLTfUf3UdfTuay3Yai9aEcRPWp9GrMO7G
+axsKCifTz6177gyr6Fv8HLeMZMh9rMZRn3e0zfaF6vrH1QnZZOts5jpUa0KugSCd
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+ZZHfN8tI39+zucfJskPWmGECgYEAg9guF1Fn6InJrqwR82IYj6SN6CeXHufSM392
+C/4xDDd3rDf4QlwECV2J0RzGf9I5Ae2EshNwWScE6Be0RweTh6cw2tJq6h7J6D8f
+2x4Dw49TF7klMdRIJUf2f5pLpHJccLswqTqzz7V69PCSABVxmUi8m6EiEYconp5W
+v7nfE2UCgYALrEqzncuSIX3q6TVAjnzT7gO4h8h2TUekIWdHQFldFx8R7Kncggnd
+48gQqhewchNR83UCcd7pPsCcTqu6UR1QRdq/DV5P6J3xdZ2iS/2gCM6hvWIvKZEv
+/ClnkyFCOW7zX6RKIXtRYZTV1kz3TajApi34RTIeIMTieaCarnBJbA==
+-----END RSA PRIVATE KEY-----
diff --git a/src/test/ssl/ssl/server-ip-alt-names.crt b/src/test/ssl/ssl/server-ip-alt-names.crt
new file mode 100644
index 0000000000..8a1bc620bb
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-alt-names.crt
@@ -0,0 +1,19 @@
+-----BEGIN CERTIFICATE-----
+MIIDCTCCAfGgAwIBAgIIICERKREEUAAwDQYJKoZIhvcNAQELBQAwQjFAMD4GA1UE
+Aww3VGVzdCBDQSBmb3IgUG9zdGdyZVNRTCBTU0wgcmVncmVzc2lvbiB0ZXN0IHNl
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+GIcEwAACAYcQIAENuAAAAAAAAAAAAAAAATANBgkqhkiG9w0BAQsFAAOCAQEAwZJ+
+8KpABTlMEgKnHIYb35ItGhtFiTLQta9RkXx7vaeDwpOdPP/IvuvpjpQZkobRgBsk
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+B1+5vnUjZaCfnSEA7A==
+-----END CERTIFICATE-----
diff --git a/src/test/ssl/ssl/server-ip-alt-names.key b/src/test/ssl/ssl/server-ip-alt-names.key
new file mode 100644
index 0000000000..b210b3a991
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-alt-names.key
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----
+MIIEpQIBAAKCAQEA4zzIHppVZvXu6OvdrJTrabEdCiqfgK8b3JeUm8Y4a/+6uxZW
+zRRgl1z3ouw1k3WzN2b1rI3MIjDd6Nr5QuyPEKLr7cszik7vog5Ev9cVqaVM9hsF
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+W8D4WdSi0jyqr99TuVBWhbTZJviMB3pHqKaHQ07hnd/lPtvzsiH12qk=
+-----END RSA PRIVATE KEY-----
diff --git a/src/test/ssl/ssl/server-ip-cn-and-alt-names.crt b/src/test/ssl/ssl/server-ip-cn-and-alt-names.crt
new file mode 100644
index 0000000000..2be02feb03
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-cn-and-alt-names.crt
@@ -0,0 +1,19 @@
+-----BEGIN CERTIFICATE-----
+MIIDHTCCAgWgAwIBAgIIICIBBBQ2MQAwDQYJKoZIhvcNAQELBQAwQjFAMD4GA1UE
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+-----END CERTIFICATE-----
diff --git a/src/test/ssl/ssl/server-ip-cn-and-alt-names.key b/src/test/ssl/ssl/server-ip-cn-and-alt-names.key
new file mode 100644
index 0000000000..54fe80fc68
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-cn-and-alt-names.key
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----
+MIIEpAIBAAKCAQEAwmqTdQJfs2Ti9tPitYp227I0HvL/kNSgA6egFr0foRo0Borw
+JNIzdbV0+EnsfiBNTWL5It26gqO7UP3ms8t2vHD5gkXfT+f6ts0lVJEcIOkUD/8w
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+qTQSDIeoDC/V8cyRoIfqPvTVqY8Rgew6GEkv0bAImdxhoSng7vIseg==
+-----END RSA PRIVATE KEY-----
diff --git a/src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.crt b/src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.crt
new file mode 100644
index 0000000000..23c06da01c
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.crt
@@ -0,0 +1,20 @@
+-----BEGIN CERTIFICATE-----
+MIIDQzCCAiugAwIBAgIIICIBBBQ2MQEwDQYJKoZIhvcNAQELBQAwQjFAMD4GA1UE
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+aZERhX5TA9DYk4gC8OY0yGaYCIj3Dd4=
+-----END CERTIFICATE-----
diff --git a/src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.key b/src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.key
new file mode 100644
index 0000000000..0ace41e0a1
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-cn-and-dns-alt-names.key
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----
+MIIEogIBAAKCAQEA8xddbo/x2TOSIa/br8BNo/URdTr9+l2R5YojiZKDuLxiQVkg
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+C7ZYZYmfG9agcZb5NkqKPTfCxkBhWbdgTTgBKVO/xQst8EUgko8=
+-----END RSA PRIVATE KEY-----
diff --git a/src/test/ssl/ssl/server-ip-cn-only.crt b/src/test/ssl/ssl/server-ip-cn-only.crt
new file mode 100644
index 0000000000..9bf015cf18
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-cn-only.crt
@@ -0,0 +1,18 @@
+-----BEGIN CERTIFICATE-----
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+4sI3XWqzkPmG9Vsxm9Vu9/Ma+PRO76VyCoIwBd+Ufg5vNXhMmw==
+-----END CERTIFICATE-----
diff --git a/src/test/ssl/ssl/server-ip-cn-only.key b/src/test/ssl/ssl/server-ip-cn-only.key
new file mode 100644
index 0000000000..1966530e72
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-cn-only.key
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----
+MIIEowIBAAKCAQEA1azW5QvvWcdgX1mPqn4zcylgO/HfaIKNV20flraqlJYddODS
+tHx0tfTL3Zy85i8xcdFqNlPVq+kevx2ig9hJVpekYwo28X9CL5YVii9Fs/a+Z3XK
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+nnJ1OINY9ziXJZfju7FpVWpkiuPzWCh6y/o3gZ/veq5mIUxuDMVa
+-----END RSA PRIVATE KEY-----
diff --git a/src/test/ssl/ssl/server-ip-in-dnsname.crt b/src/test/ssl/ssl/server-ip-in-dnsname.crt
new file mode 100644
index 0000000000..78ad8d99c8
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-in-dnsname.crt
@@ -0,0 +1,18 @@
+-----BEGIN CERTIFICATE-----
+MIIC/DCCAeSgAwIBAgIIICIDFRVYUgAwDQYJKoZIhvcNAQELBQAwQjFAMD4GA1UE
+Aww3VGVzdCBDQSBmb3IgUG9zdGdyZVNRTCBTU0wgcmVncmVzc2lvbiB0ZXN0IHNl
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+3C0BPj9Yx2VtWi4U0qoef/iLJxJBCLvE/97+duPdKx0AkkOWA9VuenkWLp797UM8
+-----END CERTIFICATE-----
diff --git a/src/test/ssl/ssl/server-ip-in-dnsname.key b/src/test/ssl/ssl/server-ip-in-dnsname.key
new file mode 100644
index 0000000000..ba319b001e
--- /dev/null
+++ b/src/test/ssl/ssl/server-ip-in-dnsname.key
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----
+MIIEowIBAAKCAQEAymfls/X858FBH/K86Q4HPECsTWPVhKFVralyPz3r4JUMSBU3
+keW7PsodT8ljM1kIAdvlYAe69fEp6iPhOLlt7Uqyo7SY3Wn5Ew3tWUKkKlvQBZPP
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+18urAmwuPp2mEQK/f+e9AhlRLdcvlqDyKm+zMrVixK77Hj5JiEkh3rfZ3onHHKGE
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+FGSg5WUiAERU/OgODoqZNTeIwIDB/f9NK45dEY3Hw6BsSFfU2VChrlNoVlzFUx2k
+yaH5Y4ECgYEA8rht3crh3GTy0jBJjNqB2iul8fkG/uiaiSvERWT/+KZnmV1+JGAW
+h2/wvd5apagOJjqKY0bCHMei/qYF9r4yJnkIy4qNper3QUz7TMCjsWduCm8S834A
+Z+Vwi3RBGJiQQH9Dfexko5sDjo+w5g4RsH52INCeReInNdxHOv06jZECgYEA1XrR
+QNwZlxHt3H93YKmKDZXikqW12Cuq6RSwf5VVdeuzV+pUN+/JaSgEuYsBilW7Q5p2
+gPROi0l8/eUPsBJb+dh1BcGzSjI2Kkzf66QOTG83S7tCPwQhwJUAylFuADvURjPQ
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+mARzkg59BxfZRN7IxcG4k0a1v98i+xISdYqwkP7cdOU18Tf8k1mwsrKytrcheqaf
+mn2bzJ5gJKs9s+DgWmjQ45dpCCqb4hfpnro8lKVwdSifkNKB6gYZ8RHYdMYkq+S1
+6SGeBbv95/qNrXjZq8POUQKBgHyaDwD4dsdCY79LdvYofrenQHOv3Q+rjTo2JT6S
+fysww6EQ2M89WiXSgc96Xw/LMl4nDfv+nMmXvyjCRgHS9XRC7yrJAEjSPeM6s4fq
+XZ4nW/ML/YKiesDZN3jfRoFEaoX/QFBLpcuLzG9uQw1ymwy5RSxK7b7kE+eGQU82
+XOihAoGBAI3xvT9fG3jRsSuw/8OQBlmDUFZcT0fRPRZ3pg8XlSreAam4b607d2WY
+u/bBHIclG3CLJ2EFqBtxl9AQeM0OTweF0KmV3dbtdBmaTbnhbK8/NLYnl5+aosEJ
+YrFKD8k8z6z+mYQs+7bAnfRa53TjfC7f24BpgEQyEfKL2fa3PF+J
+-----END RSA PRIVATE KEY-----
diff --git a/src/test/ssl/sslfiles.mk b/src/test/ssl/sslfiles.mk
index 7ed3a30f5c..d6a3870079 100644
--- a/src/test/ssl/sslfiles.mk
+++ b/src/test/ssl/sslfiles.mk
@@ -22,9 +22,15 @@
 # key/certificate pair will be generated for you, signed by the appropriate CA.
 #
 SERVERS := server-cn-and-alt-names \
+	server-cn-and-ip-alt-names \
 	server-cn-only \
+	server-ip-cn-only \
+	server-ip-cn-and-alt-names \
+	server-ip-cn-and-dns-alt-names \
+	server-ip-in-dnsname \
 	server-single-alt-name \
 	server-multiple-alt-names \
+	server-ip-alt-names \
 	server-no-names \
 	server-revoked
 CLIENTS := client client-dn client-revoked client_ext
diff --git a/src/test/ssl/t/001_ssltests.pl b/src/test/ssl/t/001_ssltests.pl
index d8eeb085da..051de4efb0 100644
--- a/src/test/ssl/t/001_ssltests.pl
+++ b/src/test/ssl/t/001_ssltests.pl
@@ -229,6 +229,30 @@ $node->connect_fails(
 	  qr/\Qserver certificate for "common-name.pg-ssltest.test" does not match host name "wronghost.test"\E/
 );
 
+# Test with an IP address in the Common Name. This is a strange corner case that
+# nevertheless is supported, as long as the address string matches exactly.
+switch_server_cert($node, certfile => 'server-ip-cn-only');
+
+$common_connstr =
+  "$default_ssl_connstr user=ssltestuser dbname=trustdb sslrootcert=ssl/root+server_ca.crt hostaddr=$SERVERHOSTADDR sslmode=verify-full";
+
+$node->connect_ok("$common_connstr host=192.0.2.1",
+	"IP address in the Common Name");
+
+$node->connect_fails(
+	"$common_connstr host=192.000.002.001",
+	"mismatch between host name and server certificate IP address",
+	expected_stderr =>
+	  qr/\Qserver certificate for "192.0.2.1" does not match host name "192.000.002.001"\E/
+);
+
+# Similarly, we'll also match an IP address in a dNSName SAN. (This is
+# long-standing behavior.)
+switch_server_cert($node, certfile => 'server-ip-in-dnsname');
+
+$node->connect_ok("$common_connstr host=192.0.2.1",
+	"IP address in a dNSName");
+
 # Test Subject Alternative Names.
 switch_server_cert($node, certfile => 'server-multiple-alt-names');
 
@@ -281,7 +305,58 @@ $node->connect_fails(
 	  qr/\Qserver certificate for "single.alt-name.pg-ssltest.test" does not match host name "deep.subdomain.wildcard.pg-ssltest.test"\E/
 );
 
-# Test server certificate with a CN and SANs. Per RFCs 2818 and 6125, the CN
+# Test certificate with IP addresses in the SANs.
+switch_server_cert($node, certfile => 'server-ip-alt-names');
+
+$node->connect_ok(
+	"$common_connstr host=192.0.2.1",
+	"host matching an IPv4 address (Subject Alternative Name 1)");
+
+$node->connect_ok(
+	"$common_connstr host=192.000.002.001",
+	"host matching an IPv4 address in alternate form (Subject Alternative Name 1)");
+
+$node->connect_fails(
+	"$common_connstr host=192.0.2.2",
+	"host not matching an IPv4 address (Subject Alternative Name 1)",
+	expected_stderr =>
+	  qr/\Qserver certificate for "192.0.2.1" (and 1 other name) does not match host name "192.0.2.2"\E/
+);
+
+$node->connect_fails(
+	"$common_connstr host=192.0.2.1/32",
+	"IPv4 host with CIDR mask does not match",
+	expected_stderr =>
+	  qr/\Qserver certificate for "192.0.2.1" (and 1 other name) does not match host name "192.0.2.1\/32"\E/
+);
+
+$node->connect_ok(
+	"$common_connstr host=2001:DB8::1",
+	"host matching an IPv6 address (Subject Alternative Name 2)");
+
+$node->connect_ok(
+	"$common_connstr host=2001:db8:0:0:0:0:0:1",
+	"host matching an IPv6 address in alternate form (Subject Alternative Name 2)");
+
+$node->connect_ok(
+	"$common_connstr host=2001:db8::0.0.0.1",
+	"host matching an IPv6 address in mixed form (Subject Alternative Name 2)");
+
+$node->connect_fails(
+	"$common_connstr host=::1",
+	"host not matching an IPv6 address (Subject Alternative Name 2)",
+	expected_stderr =>
+	  qr/\Qserver certificate for "192.0.2.1" (and 1 other name) does not match host name "::1"\E/
+);
+
+$node->connect_fails(
+	"$common_connstr host=2001:DB8::1/128",
+	"IPv6 host with CIDR mask does not match",
+	expected_stderr =>
+	  qr/\Qserver certificate for "192.0.2.1" (and 1 other name) does not match host name "2001:DB8::1\/128"\E/
+);
+
+# Test server certificate with a CN and DNS SANs. Per RFCs 2818 and 6125, the CN
 # should be ignored when the certificate has both.
 switch_server_cert($node, certfile => 'server-cn-and-alt-names');
 
@@ -299,6 +374,39 @@ $node->connect_fails(
 	  qr/\Qserver certificate for "dns1.alt-name.pg-ssltest.test" (and 1 other name) does not match host name "common-name.pg-ssltest.test"\E/
 );
 
+# But we will fall back to check the CN if the SANs contain only IP addresses.
+switch_server_cert($node, certfile => 'server-cn-and-ip-alt-names');
+
+$node->connect_ok("$common_connstr host=common-name.pg-ssltest.test",
+	"certificate with both a CN and IP SANs matches CN");
+$node->connect_ok("$common_connstr host=192.0.2.1",
+	"certificate with both a CN and IP SANs matches SAN 1");
+$node->connect_ok("$common_connstr host=2001:db8::1",
+	"certificate with both a CN and IP SANs matches SAN 2");
+
+# And now the same tests, but with IP addresses and DNS names swapped.
+switch_server_cert($node, certfile => 'server-ip-cn-and-alt-names');
+
+$node->connect_ok("$common_connstr host=192.0.2.2",
+	"certificate with both an IP CN and IP SANs 1");
+$node->connect_ok("$common_connstr host=2001:db8::1",
+	"certificate with both an IP CN and IP SANs 2");
+$node->connect_fails(
+	"$common_connstr host=192.0.2.1",
+	"certificate with both an IP CN and IP SANs ignores CN",
+	expected_stderr =>
+	  qr/\Qserver certificate for "192.0.2.2" (and 1 other name) does not match host name "192.0.2.1"\E/
+);
+
+switch_server_cert($node, certfile => 'server-ip-cn-and-dns-alt-names');
+
+$node->connect_ok("$common_connstr host=192.0.2.1",
+	"certificate with both an IP CN and DNS SANs matches CN");
+$node->connect_ok("$common_connstr host=dns1.alt-name.pg-ssltest.test",
+	"certificate with both an IP CN and DNS SANs matches SAN 1");
+$node->connect_ok("$common_connstr host=dns2.alt-name.pg-ssltest.test",
+	"certificate with both an IP CN and DNS SANs matches SAN 2");
+
 # Finally, test a server certificate that has no CN or SANs. Of course, that's
 # not a very sensible certificate, but libpq should handle it gracefully.
 switch_server_cert($node, certfile => 'server-no-names');
-- 
2.25.1

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