[PATCH 07/18] nvme-keyring: implement nvme_tls_psk_default()

[Hannes Reinecke <hare@suse.de>]

Implement a function to select the 'best' PSK for TLS.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/nvme/common/keyring.c | 47 +++++++++++++++++++++++++++++++++++
 include/linux/nvme-keyring.h  |  2 ++
 2 files changed, 49 insertions(+)

diff --git a/drivers/nvme/common/keyring.c b/drivers/nvme/common/keyring.c
index 4ac33538f839..ca36a061bd48 100644
--- a/drivers/nvme/common/keyring.c
+++ b/drivers/nvme/common/keyring.c
@@ -103,6 +103,53 @@ struct key *nvme_tls_psk_lookup(struct key *keyring,
 }
 EXPORT_SYMBOL_GPL(nvme_tls_psk_lookup);
 
+/*
+ * NVMe PSK priority list
+ *
+ * 'Retained' PSKs (ie 'generated == false')
+ * should be preferred to 'generated' PSKs,
+ * and SHA-384 should be preferred to SHA-256.
+ */
+struct nvme_psk_priority_list {
+	bool generated;
+	enum nvme_tcp_tls_cipher cipher;
+} nvme_psk_prio[] = {
+	{ .generated = false,
+	  .cipher = NVME_TCP_TLS_CIPHER_SHA384, },
+	{ .generated = false,
+	  .cipher = NVME_TCP_TLS_CIPHER_SHA256, },
+	{ .generated = true,
+	  .cipher = NVME_TCP_TLS_CIPHER_SHA384, },
+	{ .generated = true,
+	  .cipher = NVME_TCP_TLS_CIPHER_SHA256, },
+};
+
+/*
+ * nvme_tls_psk_default - Return 'best' PSK to use for TLS ClientHello
+ */
+key_serial_t nvme_tls_psk_default(struct key *keyring,
+		      const char *hostnqn, const char *subnqn)
+{
+	struct key *tls_key;
+	key_serial_t tls_key_id;
+	int prio;
+
+	for (prio = 0; prio < ARRAY_SIZE(nvme_psk_prio); prio++) {
+		bool generated = nvme_psk_prio[prio].generated;
+		enum nvme_tcp_tls_cipher cipher = nvme_psk_prio[prio].cipher;
+
+		tls_key = nvme_tls_psk_lookup(keyring, hostnqn, subnqn,
+					      cipher, generated);
+		if (!IS_ERR(tls_key)) {
+			tls_key_id = tls_key->serial;
+			key_put(tls_key);
+			return tls_key_id;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvme_tls_psk_default);
+
 int nvme_keyring_init(void)
 {
 	int err;
diff --git a/include/linux/nvme-keyring.h b/include/linux/nvme-keyring.h
index 5be60485ddfa..5293e0a90167 100644
--- a/include/linux/nvme-keyring.h
+++ b/include/linux/nvme-keyring.h
@@ -9,6 +9,8 @@
 struct key *nvme_tls_psk_lookup(struct key *keyring,
 				const char *hostnqn, const char *subnqn,
 				int hmac, bool generated);
+key_serial_t nvme_tls_psk_default(struct key *keyring,
+				  const char *hostnqn, const char *subnqn);
 
 key_serial_t nvme_keyring_id(void);
 
-- 
2.35.3