Fix indefinite loop in SHA alter.

Author: ccli8

features/mbedtls/targets/TARGET_NUVOTON/TARGET_M480/sha/sha_alt_hw.c

@@ -23,6 +23,7 @@
 #if defined(MBEDTLS_SHA1_ALT) || defined(MBEDTLS_SHA256_ALT) || defined(MBEDTLS_SHA512_ALT)
 
 #include "nu_bitutil.h"
+#include "nu_timer.h"
 #include "mbed_assert.h"
 #include "mbed_error.h"
 #include "crypto-misc.h"
@@ -374,9 +375,20 @@ void crypto_sha_update_nobuf(crypto_sha_context *ctx, const unsigned char *input
     if (islast) {   // Finish of last block
         while (CRPT->HMAC_STS & CRPT_HMAC_STS_BUSY_Msk);
     } else { // Finish of non-last block
-        // No H/W flag to indicate finish of non-last block process.
-        // Values of SHA_DGSTx registers will change as last word of the block is input, so use it for judgement.
+        /* SHA accelerator doesn't export a flag to indicate non-last block process has finished.
+         * Per designer, if the digest (SHA_DGSTx) code changes after the last word of the block is input,
+         * this indicates the non-last block process has finished.
+         *
+         * There is a rare case that two digest codes are the same for 
+         * two non-last block processes in a row.
+         * To address it, we use a count-down timer to detect it.
+         * As the count-down timer expires, we see it as finished.
+         */
         int isfinish = 0;
+        struct nu_countdown_ctx_s ctx;
+
+        // Set up 2s timeout
+        nu_countdown_init(&ctx, 2000*1000);
         while (! isfinish) {
             switch (sha_opmode) {
             case SHA_MODE_SHA512:
@@ -408,7 +420,14 @@ void crypto_sha_update_nobuf(crypto_sha_context *ctx, const unsigned char *input
                     break;
                 }
             }
+            
+            if (nu_countdown_expired(&ctx)) {
+                // We may meet a rare case that the current digest code and the previous one are the same.
+                isfinish = 1;
+            }
         }
+        // Must pair nu_countdown_init with nu_countdown_free in the end
+        nu_countdown_free(&ctx);
     }
 }
 

features/mbedtls/targets/TARGET_NUVOTON/TARGET_NUC472/sha/sha_alt_hw.c

@@ -23,6 +23,7 @@
 #if defined(MBEDTLS_SHA1_ALT) || defined(MBEDTLS_SHA256_ALT) || defined(MBEDTLS_SHA512_ALT)
 
 #include "nu_bitutil.h"
+#include "nu_timer.h"
 #include "mbed_assert.h"
 #include "mbed_error.h"
 #include "crypto-misc.h"
@@ -283,9 +284,20 @@ void crypto_sha_update_nobuf(crypto_sha_context *ctx, const unsigned char *input
     if (islast) {   // Finish of last block
         while (CRPT->SHA_STS & CRPT_SHA_STS_BUSY_Msk);
     } else { // Finish of non-last block
-        // No H/W flag to indicate finish of non-last block process.
-        // Values of SHA_DGSTx registers will change as last word of the block is input, so use it for judgement.
+        /* SHA accelerator doesn't export a flag to indicate non-last block process has finished.
+         * Per designer, if the digest (SHA_DGSTx) code changes after the last word of the block is input,
+         * this indicates the non-last block process has finished.
+         *
+         * There is a rare case that two digest codes are the same for 
+         * two non-last block processes in a row.
+         * To address it, we use a count-down timer to detect it.
+         * As the count-down timer expires, we see it as finished.
+         */
         int isfinish = 0;
+        struct nu_countdown_ctx_s ctx;
+
+        // Set up 2s timeout
+        nu_countdown_init(&ctx, 2000*1000);
         while (! isfinish) {
             switch (sha_opmode) {
             case SHA_MODE_SHA256:
@@ -305,7 +317,14 @@ void crypto_sha_update_nobuf(crypto_sha_context *ctx, const unsigned char *input
                     break;
                 }
             }
+            
+            if (nu_countdown_expired(&ctx)) {
+                // We may meet a rare case that the current digest code and the previous one are the same.
+                isfinish = 1;
+            }
         }
+        // Must pair nu_countdown_init with nu_countdown_free in the end
+        nu_countdown_free(&ctx);
     }
 }
 

targets/TARGET_NUVOTON/nu_timer.h

@@ -0,0 +1,93 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2015-2016 Nuvoton
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef NU_TIMER_H
+#define NU_TIMER_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include "cmsis.h"
+#include "mbed_sleep.h"
+#include "mbed_critical.h"
+#include "ticker_api.h"
+#include "us_ticker_api.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* A simple count-down timer used for Nuvoton ported drivers
+ *
+ * NOTE: nu_countdown_init must be paired with nu_countdown_free.
+ *
+ * Example:
+ * nu_countdown_ctx_s ctx;
+ * 
+ * // Set up 2 ms timeout
+ * nu_countdown_init(&ctx, 2000);
+ *
+ * // Timed-wait for a task
+ * while (true) {
+ *     // Poll the task
+ *
+ *     if (nu_countdown_expired(&ctx)) {
+ *         // Timeout
+ *     }
+ * }
+ *
+ * // Must pair nu_countdown_init with nu_countdown_free in the end
+ * nu_countdown_free(&ctx);
+ */
+
+struct nu_countdown_ctx_s {
+    const ticker_data_t *   _ticker_data;       // Hold ticker_data_t
+    us_timestamp_t          _interval_end_us;   // End of interval in us
+    bool                    _expired;           // Expired or not
+};
+
+__STATIC_INLINE void nu_countdown_init(struct nu_countdown_ctx_s *ctx, us_timestamp_t interval_us)
+{
+    core_util_critical_section_enter();
+    sleep_manager_lock_deep_sleep();
+    ctx->_ticker_data = get_us_ticker_data();
+    ctx->_interval_end_us = ticker_read_us(ctx->_ticker_data) + interval_us;
+    ctx->_expired = false;
+    core_util_critical_section_exit();
+}
+
+__STATIC_INLINE bool nu_countdown_expired(struct nu_countdown_ctx_s *ctx)
+{
+    core_util_critical_section_enter();
+    if (! ctx->_expired) {
+        ctx->_expired = ticker_read_us(ctx->_ticker_data) >= ctx->_interval_end_us;
+    }
+    core_util_critical_section_exit();
+    
+    return ctx->_expired;
+}
+
+__STATIC_INLINE void nu_countdown_free(struct nu_countdown_ctx_s *ctx)
+{
+    core_util_critical_section_enter();
+    sleep_manager_unlock_deep_sleep();
+    core_util_critical_section_exit();
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif