From f8a34f9e3997923479d571c850acaf57f759c564 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 13 Aug 2026 09:57:27 +0900
Subject: [PATCH v2] Use explicit fetching of digests in channel binding
 (OpenSSL >= 3.0)

This touches both the libpq and backend-side code of channel binding
where respectively pgtls_get_peer_certificate_hash() and
be_tls_get_certificate_hash() are upgraded to retrieve digests using the
method recommended by OpenSSL 3.0: no more EVP_sha256(), just a
EVP_get_digestbynid() through EVP.

The pre-3.0 code is still required for LibreSSL and as long as we
support OpenSSL 1.1.1.
---
 src/backend/libpq/be-secure-openssl.c    | 34 +++++++++++++++++++++
 src/interfaces/libpq/fe-secure-openssl.c | 38 ++++++++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 047647008458..4f4ffca21b86 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -2282,7 +2282,12 @@ be_tls_get_certificate_hash(Port *port, size_t *len)
 {
 	X509	   *server_cert;
 	char	   *cert_hash;
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+	EVP_MD	   *algo_type;
+	const char *algo_name;
+#else
 	const EVP_MD *algo_type = NULL;
+#endif
 	unsigned char hash[EVP_MAX_MD_SIZE];	/* size for SHA-512 */
 	unsigned int hash_size;
 	int			algo_nid;
@@ -2311,6 +2316,25 @@ be_tls_get_certificate_hash(Port *port, size_t *len)
 	 * (https://tools.ietf.org/html/rfc5929#section-4.1).  If something else
 	 * is used, the same hash as the signature algorithm is used.
 	 */
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+	switch (algo_nid)
+	{
+		case NID_md5:
+		case NID_sha1:
+			algo_name = "SHA256";
+			break;
+		default:
+			algo_name = OBJ_nid2sn(algo_nid);
+			if (algo_name == NULL)
+				elog(ERROR, "could not find digest for NID %s",
+					 OBJ_nid2sn(algo_nid));
+			break;
+	}
+
+	algo_type = EVP_MD_fetch(NULL, algo_name, NULL);
+	if (algo_type == NULL)
+		elog(ERROR, "could not fetch digest \"%s\"", algo_name);
+#else
 	switch (algo_nid)
 	{
 		case NID_md5:
@@ -2324,10 +2348,20 @@ be_tls_get_certificate_hash(Port *port, size_t *len)
 					 OBJ_nid2sn(algo_nid));
 			break;
 	}
+#endif
 
 	/* generate and save the certificate hash */
 	if (!X509_digest(server_cert, algo_type, hash, &hash_size))
+	{
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+		EVP_MD_free(algo_type);
+#endif
 		elog(ERROR, "could not generate server certificate hash");
+	}
+
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+	EVP_MD_free(algo_type);
+#endif
 
 	cert_hash = palloc(hash_size);
 	memcpy(cert_hash, hash, hash_size);
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 3ef12987feea..47ca0f470141 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -371,7 +371,12 @@ char *
 pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 {
 	X509	   *peer_cert;
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+	EVP_MD	   *algo_type;
+	const char *algo_name;
+#else
 	const EVP_MD *algo_type;
+#endif
 	unsigned char hash[EVP_MAX_MD_SIZE];	/* size for SHA-512 */
 	unsigned int hash_size;
 	int			algo_nid;
@@ -406,6 +411,31 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 	 * (https://tools.ietf.org/html/rfc5929#section-4.1).  If something else
 	 * is used, the same hash as the signature algorithm is used.
 	 */
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+	switch (algo_nid)
+	{
+		case NID_md5:
+		case NID_sha1:
+			algo_name = "SHA256";
+			break;
+		default:
+			algo_name = OBJ_nid2sn(algo_nid);
+			if (algo_name == NULL)
+			{
+				libpq_append_conn_error(conn, "could not find digest for NID %s",
+										OBJ_nid2sn(algo_nid));
+				return NULL;
+			}
+			break;
+	}
+
+	algo_type = EVP_MD_fetch(NULL, algo_name, NULL);
+	if (algo_type == NULL)
+	{
+		libpq_append_conn_error(conn, "could not fetch digest \"%s\"", algo_name);
+		return NULL;
+	}
+#else
 	switch (algo_nid)
 	{
 		case NID_md5:
@@ -422,13 +452,21 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			}
 			break;
 	}
+#endif
 
 	if (!X509_digest(peer_cert, algo_type, hash, &hash_size))
 	{
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+		EVP_MD_free(algo_type);
+#endif
 		libpq_append_conn_error(conn, "could not generate peer certificate hash");
 		return NULL;
 	}
 
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+	EVP_MD_free(algo_type);
+#endif
+
 	/* save result */
 	cert_hash = malloc(hash_size);
 	if (cert_hash == NULL)
-- 
2.55.0