Secure boot: initial image signature support

components/bootloader_support/src/secure_boot_signatures.c

@@ -0,0 +1,99 @@
+// 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 "sdkconfig.h"
+
+#include "bootloader_flash.h"
+#include "esp_log.h"
+#include "esp_image_format.h"
+#include "esp_secure_boot.h"
+
+#include "uECC.h"
+
+#ifdef BOOTLOADER_BUILD
+#include "rom/sha.h"
+typedef SHA_CTX sha_context;
+#else
+#include "hwcrypto/sha.h"
+typedef esp_sha_context sha_context;
+#endif
+
+typedef struct {
+    uint32_t version;
+    uint8_t signature[64];
+} signature_block_t;
+
+static const char* TAG = "secure_boot";
+
+extern const uint8_t signature_verification_key_start[] asm("_binary_signature_verification_key_bin_start");
+extern const uint8_t signature_verification_key_end[] asm("_binary_signature_verification_key_bin_end");
+
+#define SIGNATURE_VERIFICATION_KEYLEN 64
+
+esp_err_t esp_secure_boot_verify_signature(uint32_t src_addr, uint32_t length)
+{
+    sha_context sha;
+    uint8_t digest[64];
+    ptrdiff_t keylen;
+    const uint8_t *data;
+    const signature_block_t *sigblock;
+    bool is_valid;
+
+    ESP_LOGD(TAG, "verifying signature src_addr 0x%x length 0x%x", src_addr, length);
+
+    data = bootloader_mmap(src_addr, length + sizeof(signature_block_t));
+    if(data == NULL) {
+        ESP_LOGE(TAG, "bootloader_mmap(0x%x, 0x%x) failed", src_addr, length+sizeof(signature_block_t));
+        return ESP_FAIL;
+    }
+
+    sigblock = (const signature_block_t *)(data + length);
+
+    if (sigblock->version != 0) {
+        ESP_LOGE(TAG, "src 0x%x has invalid signature version field 0x%08x", src_addr, sigblock->version);
+        goto unmap_and_fail;
+    }
+
+#ifdef BOOTLOADER_BUILD
+    /* Use ROM SHA functions directly */
+    ets_sha_enable();
+    ets_sha_init(&sha);
+    ets_sha_update(&sha, SHA2_512, data, length);
+    ets_sha_finish(&sha, SHA2_512, digest);
+    ets_sha_disable();
+#else
+    /* Use thread-safe esp-idf SHA layer */
+    esp_sha512_init(&sha);
+    esp_sha512_start(&sha, false);
+    esp_sha512_update(&sha, data, length);
+    esp_sha512_finish(&sha, digest);
+    esp_sha512_free(&sha);
+#endif
+
+    keylen = signature_verification_key_end - signature_verification_key_start;
+    if(keylen != SIGNATURE_VERIFICATION_KEYLEN) {
+        ESP_LOGE(TAG, "Embedded public verification key has wrong length %d", keylen);
+        goto unmap_and_fail;
+    }
+
+    is_valid = uECC_verify(signature_verification_key_start,
+                           digest, sizeof(digest), sigblock->signature,
+                           uECC_secp256r1());
+
+    bootloader_unmap(data);
+    return is_valid ? ESP_OK : ESP_ERR_IMAGE_INVALID;
+
+ unmap_and_fail:
+    bootloader_unmap(data);
+    return ESP_FAIL;
+}