From bdd640e7e63d5ea3ff0af9a63261a252949b71c5 Mon Sep 17 00:00:00 2001
From: James M Snell <jasnell@gmail.com>
Date: Sun, 5 Jan 2020 13:27:19 -0800
Subject: [PATCH] Additional crypto helper function
* `ngtcp2_crypto_generate_stateless_reset_token` - Used to generate
a stateless reset token as an HKDF extraction using the CID and
a token secret as input.
---
crypto/includes/ngtcp2/ngtcp2_crypto.h | 15 +++++++++++++++
crypto/shared.c | 23 +++++++++++++++++++++++
2 files changed, 38 insertions(+)
diff --git a/crypto/includes/ngtcp2/ngtcp2_crypto.h b/crypto/includes/ngtcp2/ngtcp2_crypto.h
index 99d2f687..1368c368 100644
--- a/crypto/includes/ngtcp2/ngtcp2_crypto.h
+++ b/crypto/includes/ngtcp2/ngtcp2_crypto.h
@@ -492,6 +492,21 @@ NGTCP2_EXTERN int
ngtcp2_crypto_set_remote_transport_params(ngtcp2_conn *conn, void *tls,
ngtcp2_crypto_side side);
+/**
+ * @function
+ *
+ * `ngtcp2_crypto_generate_stateless_reset_token` generates a
+ * stateless reset token using HKDF extraction with |md| using the
+ * given |cid| and static key |secret| as input. The token will be
+ * written to the buffer pointed by |token| and it must have a
+ * capacity of at least NGTCP2_STATELESS_RESET_TOKENLEN bytes.
+ *
+ * This function returns 0 if it succeeds, or -1.
+ */
+NGTCP2_EXTERN int ngtcp2_crypto_generate_stateless_reset_token(
+ uint8_t *token, const ngtcp2_crypto_md *md, const uint8_t *secret,
+ size_t secretlen, const ngtcp2_cid *cid);
+
#ifdef __cplusplus
}
#endif
diff --git a/crypto/shared.c b/crypto/shared.c
index 9d5feb60..f12736ce 100644
--- a/crypto/shared.c
+++ b/crypto/shared.c
@@ -25,6 +25,7 @@
#include "shared.h"
#include <string.h>
+#include <assert.h>
#include "ngtcp2_macro.h"
@@ -419,3 +420,25 @@ int ngtcp2_crypto_update_key_cb(ngtcp2_conn *conn, uint8_t *rx_secret,
}
return 0;
}
+
+int ngtcp2_crypto_generate_stateless_reset_token(uint8_t *token,
+ const ngtcp2_crypto_md *md,
+ const uint8_t *secret,
+ size_t secretlen,
+ const ngtcp2_cid *cid) {
+ uint8_t buf[64];
+ int rv;
+
+ assert(ngtcp2_crypto_md_hashlen(md) <= sizeof(buf));
+ assert(NGTCP2_STATELESS_RESET_TOKENLEN <= sizeof(buf));
+
+ rv = ngtcp2_crypto_hkdf_extract(buf, md, secret, secretlen, cid->data,
+ cid->datalen);
+ if (rv != 0) {
+ return -1;
+ }
+
+ memcpy(token, buf, NGTCP2_STATELESS_RESET_TOKENLEN);
+
+ return 0;
+}
--
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