From 93887dfe46225b4b7aafb63907ca26cce68c1510 Mon Sep 17 00:00:00 2001
From: Paul Selkirk <paul@psgd.org>
Date: Tue, 27 Oct 2020 13:35:26 -0400
Subject: Minor hashsig cleanup, add hal_hashsig_public_key_len().

---
 hal.h     |  2 ++
 hashsig.c | 45 ++++++++++++++++++++++++---------------------
 2 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/hal.h b/hal.h
index 6ed8c9d..99f0456 100644
--- a/hal.h
+++ b/hal.h
@@ -1023,6 +1023,8 @@ extern hal_error_t hal_hashsig_private_key_from_der(hal_hashsig_key_t **key_,
                                                     void *keybuf, const size_t keybuf_len,
                                                     const uint8_t *der, const size_t der_len);
 
+extern size_t hal_hashsig_public_key_len(const hal_lms_algorithm_t lms_type);
+
 extern hal_error_t hal_hashsig_public_key_to_der(const hal_hashsig_key_t * const key,
                                                  uint8_t *der, size_t *der_len, const size_t der_max);
 
diff --git a/hashsig.c b/hashsig.c
index f55558d..6a8ac8f 100644
--- a/hashsig.c
+++ b/hashsig.c
@@ -1,9 +1,11 @@
 /*
  * hashsig.c
  * ---------
- * Implementation of draft-mcgrew-hash-sigs-15.txt
+ * Implementation of RFC 8554 Leighton-Micali Hash-Based Signatures
  *
  * Copyright (c) 2018, NORDUnet A/S All rights reserved.
+ * Copyright: 2020, The Commons Conservancy Cryptech Project
+ * SPDX-License-Identifier: BSD-3-Clause
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ -15,9 +17,9 @@
  *   notice, this list of conditions and the following disclaimer in the
  *   documentation and/or other materials provided with the distribution.
  *
- * - Neither the name of the NORDUnet nor the names of its contributors may
- *   be used to endorse or promote products derived from this software
- *   without specific prior written permission.
+ * - Neither the name of the copyright holder nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
@@ -230,9 +232,15 @@ static hal_error_t lmots_generate(lmots_key_t * const key, bytestring32 *seed)
     if (key == NULL || key->type != HAL_KEY_TYPE_HASHSIG_LMOTS || key->lmots == NULL || key->x == NULL)
         return HAL_ERROR_BAD_ARGUMENTS;
 
-    size_t n = key->lmots->n;
-    size_t p = key->lmots->p;
-    size_t w = key->lmots->w;
+    const size_t n = key->lmots->n;
+    const size_t p = key->lmots->p;
+    const size_t w = key->lmots->w;
+
+    uint8_t statebuf[512];
+    hal_hash_state_t *state = NULL;
+    uint32_t l;
+    uint16_t s;
+    uint8_t b;
 
     /* generate the private key */
 
@@ -245,12 +253,6 @@ static hal_error_t lmots_generate(lmots_key_t * const key, bytestring32 *seed)
     else {
         /* use the pseudorandom key generation scheme */
         for (size_t i = 0; i < p; ++i) {
-            uint8_t statebuf[512];
-            hal_hash_state_t *state = NULL;
-            uint32_t l;
-            uint16_t s;
-            uint8_t b;
-
             /* x_q[i] = H(I || u32str(q) || u16str(i) || u8str(0xff) || SEED) */
             check(hal_hash_initialize(NULL, hal_hash_sha256, &state, statebuf, sizeof(statebuf)));
             check(hal_hash_update(state, (const uint8_t *)&key->I, sizeof(key->I)));
@@ -264,13 +266,7 @@ static hal_error_t lmots_generate(lmots_key_t * const key, bytestring32 *seed)
 
     /* generate the public key */
 
-    uint8_t statebuf[512];
-    hal_hash_state_t *state = NULL;
     bytestring32 y[p];
-    uint32_t l;
-    uint16_t s;
-    uint8_t b;
-
     for (size_t i = 0; i < p; ++i) {
         y[i] = key->x[i];
         for (size_t j = 0; j < (1U << w) - 1; ++j) {
@@ -1091,13 +1087,20 @@ static hss_key_t *hss_find(hal_uuid_t *I)
     return NULL;
 }
 
-#if 0 /* currently unused */
 static inline size_t hss_public_key_len(lms_parameter_t * const lms)
 {
     /* L || pub[0] */
     return sizeof(uint32_t) + lms_public_key_len(lms);
 }
-#endif
+
+size_t hal_hashsig_public_key_len(const hal_lms_algorithm_t lms_type)
+{
+    lms_parameter_t * const lms = lms_select_parameter_set(lms_type);
+    if (lms == NULL)
+        return 0;
+
+    return hss_public_key_len(lms);
+}
 
 static inline size_t hss_signature_len(const size_t L, lms_parameter_t * const lms, lmots_parameter_t * const lmots)
 {
-- 
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