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wolfBoot Library Integration Guide

Overview

wolfBoot can be integrated as a secure-boot library into:

Third-party bootloaders
Custom staging solutions
Existing boot chains
Verification modules

Core API

Image Verification Interface

Key Components

struct wolfBoot_image {
    // Image metadata and state
    // See wolfboot/include/image.h
};

Opening Images

int wolfBoot_open_image_address(
    struct wolfBoot_image* img,  // Uninitialized image struct
    uint8_t* image              // Pointer to manifest header
);

Return Values

Value	Description
0	Success
-1	Invalid magic number or size

Size Constraints

Maximum size: WOLFBOOT_PARTITION_SIZE
Includes manifest header
Enforced at runtime

Verification Functions

1. Integrity Check

int wolfBoot_verify_integrity(
    struct wolfBoot_image *img  // Initialized image struct
);

Operation:

Calculates SHA hash
Compares with manifest
Verifies image content

Returns:

Value	Meaning
0	Integrity verified
-1	Verification failed

2. Authenticity Verification

int wolfBoot_verify_authenticity(
    struct wolfBoot_image *img  // Initialized image struct
);

Operation:

Verifies signature
Checks against public keys
Validates trust chain

Returns:

Value	Meaning
0	Authentication successful
-1	Operation error
-2	Invalid signature

Example Implementation

Test Application

Location: hal/library.c

Features

Command-line interface
File-based verification
Integrity checking
Signature validation

Build Instructions

1. Configuration Setup

# Copy library configuration
cp config/examples/library.config .config

2. Target Configuration

Create include/target.h:

#ifndef H_TARGETS_TARGET_
#define H_TARGETS_TARGET_

/* Disable partition support */
#define WOLFBOOT_NO_PARTITIONS

/* Configure memory layout */
#define WOLFBOOT_SECTOR_SIZE     0x20000
#define WOLFBOOT_PARTITION_SIZE  0x20000

#endif /* !H_TARGETS_TARGET_ */

Important: Adjust WOLFBOOT_PARTITION_SIZE based on your requirements:

Maximum image size = PARTITION_SIZE - HEADER_SIZE
Oversized images rejected automatically

Testing Process

1. Key Generation

# Build key tools
make keytools

# Generate ED25519 keypair
./tools/keytools/keygen \
    --ed25519 \
    -g wolfboot_signing_private_key.der

2. Image Signing

# Create test image
touch empty

# Sign image
./tools/keytools/sign \
    --ed25519 \
    --sha256 \
    empty \
    wolfboot_signing_private_key.der \
    1

3. Build Test Application

# Compile with library support
make test-lib

4. Verification Test

# Run verification
./test-lib empty_v1_signed.bin

# Expected output:
# Firmware Valid
# booting 0x5609e3526590(actually exiting)

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