Provide an implementation of RFC 8446 (TLS 1.3) HKDF-Expand-Label
Signed-off-by: Chris Leech <cleech@xxxxxxxxxx>
Signed-off-by: Hannes Reinecke <hare@xxxxxxxxxx>
---
drivers/nvme/common/auth.c | 53 ++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
index 91e273b89fea3..c6eae8e6b6f99 100644
--- a/drivers/nvme/common/auth.c
+++ b/drivers/nvme/common/auth.c
@@ -683,6 +683,59 @@ int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
}
EXPORT_SYMBOL_GPL(nvme_auth_generate_digest);
+/**
+ * hkdf_expand_label - HKDF-Expand-Label (RFC 8846 section 7.1)
+ * @hmac_tfm: hash context keyed with pseudorandom key
+ * @label: ASCII label without "tls13 " prefix
+ * @labellen: length of @label
+ * @context: context bytes
+ * @contextlen: length of @context
+ * @okm: output keying material
+ * @okmlen: length of @okm
+ *
+ * Build the TLS 1.3 HkdfLabel structure and invoke hkdf_expand().
+ *
+ * Returns 0 on success with output keying material stored in @okm,
+ * or a negative errno value otherwise.
+ */
+static int hkdf_expand_label(struct crypto_shash *hmac_tfm,
+ const u8 *label, unsigned int labellen,
+ const u8 *context, unsigned int contextlen,
+ u8 *okm, unsigned int okmlen)
+{
+ int err;
+ u8 *info;
+ unsigned int infolen;
+ const char *tls13_prefix = "tls13 ";
+ unsigned int prefixlen = strlen(tls13_prefix);
+
+ if (WARN_ON(labellen > (255 - prefixlen)))
+ return -EINVAL;
+ if (WARN_ON(contextlen > 255))
+ return -EINVAL;
+
+ infolen = 2 + (1 + prefixlen + labellen) + (1 + contextlen);
+ info = kzalloc(infolen, GFP_KERNEL);
+ if (!info)
+ return -ENOMEM;
+
+ /* HkdfLabel.Length */
+ put_unaligned_be16(okmlen, info);
+
+ /* HkdfLabel.Label */
+ info[2] = prefixlen + labellen;
+ memcpy(info + 3, tls13_prefix, prefixlen);
+ memcpy(info + 3 + prefixlen, label, labellen);
+
+ /* HkdfLabel.Context */
+ info[3 + prefixlen + labellen] = contextlen;
+ memcpy(info + 4 + prefixlen + labellen, context, contextlen);
+
+ err = hkdf_expand(hmac_tfm, info, infolen, okm, okmlen);
+ kfree_sensitive(info);
+ return err;
+}
+
/**
* nvme_auth_derive_tls_psk - Derive TLS PSK
* @hmac_id: Hash function identifier
--
2.50.1
