bootloader: Calculate SHA-256 of image while loading/verifying

components/bootloader_support/src/bootloader_sha.c

@@ -0,0 +1,156 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// 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.
+#include "bootloader_sha.h"
+#include <stdbool.h>
+#include <string.h>
+#include <assert.h>
+#include <sys/param.h>
+
+#ifndef BOOTLOADER_BUILD
+// App version is a wrapper around mbedTLS SHA API
+#include <mbedtls/sha256.h>
+
+bootloader_sha256_handle_t bootloader_sha256_start()
+{
+    mbedtls_sha256_context *ctx = (mbedtls_sha256_context *)malloc(sizeof(mbedtls_sha256_context));
+    if (!ctx) {
+        return NULL;
+    }
+    mbedtls_sha256_init(ctx);
+    mbedtls_sha256_starts(ctx, false);
+    return ctx;
+}
+
+void bootloader_sha256_data(bootloader_sha256_handle_t handle, const void *data, size_t data_len)
+{
+    assert(handle != NULL);
+    mbedtls_sha256_context *ctx = (mbedtls_sha256_context *)handle;
+    mbedtls_sha256_update(ctx, data, data_len);
+}
+
+void bootloader_sha256_finish(bootloader_sha256_handle_t handle, uint8_t *digest)
+{
+    assert(handle != NULL);
+    mbedtls_sha256_context *ctx = (mbedtls_sha256_context *)handle;
+    mbedtls_sha256_finish(ctx, digest);
+}
+
+#else // Bootloader version
+
+#include "rom/sha.h"
+#include "soc/dport_reg.h"
+#include "soc/hwcrypto_reg.h"
+
+#include "rom/ets_sys.h" // TO REMOVE
+
+static uint32_t words_hashed;
+
+// Words per SHA256 block
+static const size_t BLOCK_WORDS = (64/sizeof(uint32_t));
+
+bootloader_sha256_handle_t bootloader_sha256_start()
+{
+    // Enable SHA hardware
+    ets_sha_enable();
+    words_hashed = 0;
+    return (bootloader_sha256_handle_t)&words_hashed; // Meaningless non-NULL value
+}
+
+void bootloader_sha256_data(bootloader_sha256_handle_t handle, const void *data, size_t data_len)
+{
+    assert(handle != NULL);
+    assert(data_len % 4 == 0);
+
+    const uint32_t *w = (const uint32_t *)data;
+    size_t word_len = data_len / 4;
+    uint32_t *sha_text_reg = (uint32_t *)(SHA_TEXT_BASE);
+
+    //ets_printf("word_len %d so far %d\n", word_len, words_hashed);
+    while (word_len > 0) {
+        size_t block_count = words_hashed % BLOCK_WORDS;
+        size_t copy_words = (BLOCK_WORDS - block_count);
+
+        copy_words = MIN(word_len, copy_words);
+
+        // Wait for SHA engine idle
+        while(REG_READ(SHA_256_BUSY_REG) != 0) { }
+
+        // Copy to memory block
+        //ets_printf("block_count %d copy_words %d\n", block_count, copy_words);
+        for (int i = 0; i < copy_words; i++) {
+            sha_text_reg[block_count + i] = __builtin_bswap32(w[i]);
+        }
+        asm volatile ("memw");
+
+        // Update counters
+        words_hashed += copy_words;
+        block_count += copy_words;
+        word_len -= copy_words;
+        w += copy_words;
+
+        // If we loaded a full block, run the SHA engine
+        if (block_count == BLOCK_WORDS) {
+            //ets_printf("running engine @ count %d\n", words_hashed);
+            if (words_hashed == BLOCK_WORDS) {
+                REG_WRITE(SHA_256_START_REG, 1);
+            } else {
+                REG_WRITE(SHA_256_CONTINUE_REG, 1);
+            }
+            block_count = 0;
+        }
+    }
+}
+
+void bootloader_sha256_finish(bootloader_sha256_handle_t handle, uint8_t *digest)
+{
+    assert(handle != NULL);
+
+    uint32_t data_words = words_hashed;
+    ets_printf("Padding from %d bytes\n", data_words * 4);
+
+    // Pad to a 60 byte long block loaded in the engine
+    // (normally end of block is a 64-bit length, but we know
+    // the upper 32 bits will be zeroes.)
+    int block_bytes = (words_hashed % BLOCK_WORDS) * 4;
+    int pad_bytes = 60 - block_bytes;
+    if (pad_bytes < 0) {
+        pad_bytes += 64;
+    }
+    static const uint8_t padding[64] = { 0x80, 0, };
+
+    bootloader_sha256_data(handle, padding, pad_bytes);
+
+    assert(words_hashed % BLOCK_WORDS == 56/4);
+
+    // Calculate 32-bit length for final 32 bits of data
+    uint32_t bit_count = __builtin_bswap32( data_words * 32 );
+    bootloader_sha256_data(handle, &bit_count, sizeof(bit_count));
+
+    assert(words_hashed % BLOCK_WORDS == 0);
+
+    ets_printf("Padded to %d bytes\n", words_hashed * 4);
+
+    while(REG_READ(SHA_256_BUSY_REG) == 1) { }
+    REG_WRITE(SHA_256_LOAD_REG, 1);
+    while(REG_READ(SHA_256_BUSY_REG) == 1) { }
+
+    uint32_t *digest_words = (uint32_t *)digest;
+    uint32_t *sha_text_reg = (uint32_t *)(SHA_TEXT_BASE);
+    for (int i = 0; i < BLOCK_WORDS; i++) {
+        digest_words[i] = __builtin_bswap32(sha_text_reg[i]);
+    }
+    asm volatile ("memw");
+}
+
+#endif