v2-0001-Enable-SSL-library-detection-via-PQsslAttribute.patch

From a5e5549ccec9c70a510f031a678e9f0f32a35382 Mon Sep 17 00:00:00 2001
From: Jacob Champion <pchampion@vmware.com>
Date: Mon, 29 Nov 2021 14:36:38 -0800
Subject: [PATCH v2 1/2] Enable SSL library detection via PQsslAttribute()

Currently, libpq client code must have a connection handle before it can
query the "library" SSL attribute. This poses problems if the client
needs to know what SSL library is in use before constructing a
connection string. (For example, with the NSS proposal, a client would
have to decide whether to use the "ssldatabase" connection setting
rather than "sslcert" et al.)

Allow PQsslAttribute(NULL, "library") to return the library in use --
currently, just "OpenSSL" or NULL. The new behavior is announced with
the LIBPQ_HAS_SSL_LIBRARY_DETECTION feature macro, allowing clients to
differentiate between a libpq that was compiled without SSL support and
a libpq that's just too old to tell.
---
 src/interfaces/libpq/fe-secure-openssl.c | 6 +++---
 src/interfaces/libpq/libpq-fe.h          | 2 ++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index f6e563a2e5..e095a0f538 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -1597,14 +1597,14 @@ PQsslAttributeNames(PGconn *conn)
 const char *
 PQsslAttribute(PGconn *conn, const char *attribute_name)
 {
+	if (strcmp(attribute_name, "library") == 0)
+		return "OpenSSL";
+
 	if (!conn)
 		return NULL;
 	if (conn->ssl == NULL)
 		return NULL;
 
-	if (strcmp(attribute_name, "library") == 0)
-		return "OpenSSL";
-
 	if (strcmp(attribute_name, "key_bits") == 0)
 	{
 		static char sslbits_str[12];
diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index 20eb855abc..7986445f1a 100644
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -36,6 +36,8 @@ extern "C"
 #define LIBPQ_HAS_PIPELINING 1
 /* Indicates presence of PQsetTraceFlags; also new PQtrace output format */
 #define LIBPQ_HAS_TRACE_FLAGS 1
+/* Indicates that PQsslAttribute(NULL, "library") is useful */
+#define LIBPQ_HAS_SSL_LIBRARY_DETECTION 1
 
 /*
  * Option flags for PQcopyResult
-- 
2.25.1