Change libpq's internal uses of PQhost() to inspect host field directly.

Commit 1944cdc98 changed PQhost() to return the hostaddr value when that
is specified and host isn't.  This is a good idea in general, but
fe-auth.c and related files contain PQhost() calls for which it isn't.
Specifically, when we compare SSL certificates or other server identity
information to the host field, we do not want to use hostaddr instead;
that's not what's documented, that's not what happened pre-v10, and
it doesn't seem like a good idea.

Instead, we can just look at connhost[].host directly.  This does what
we want in v10 and up; in particular, if neither host nor hostaddr
were given, the host field will be replaced with the default host name.
That seems useful, and it's likely the reason that these places were
coded to call PQhost() originally (since pre-v10, the stored field was
not replaced with the default).

Back-patch to v10, as 1944cdc98 (just) was.

Discussion: https://postgr.es/m/23287.1533227021@sss.pgh.pa.us

1 files changed, 9 insertions, 2 deletions

diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index 40203f3b642..b3f580f5950 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -88,10 +88,17 @@ pq_verify_peer_name_matches_certificate_name(PGconn *conn,
 {
 	char	   *name;
 	int			result;
-	char	   *host = PQhost(conn);
+	char	   *host = conn->connhost[conn->whichhost].host;
 
 	*store_name = NULL;
 
+	if (!(host && host[0] != '\0'))
+	{
+		printfPQExpBuffer(&conn->errorMessage,
+						  libpq_gettext("host name must be specified\n"));
+		return -1;
+	}
+
 	/*
 	 * There is no guarantee the string returned from the certificate is
 	 * NULL-terminated, so make a copy that is.
@@ -145,7 +152,7 @@ pq_verify_peer_name_matches_certificate_name(PGconn *conn,
 bool
 pq_verify_peer_name_matches_certificate(PGconn *conn)
 {
-	char	   *host = PQhost(conn);
+	char	   *host = conn->connhost[conn->whichhost].host;
 	int			rc;
 	int			names_examined = 0;
 	char	   *first_name = NULL;