Unsigned Firmware Layout

The unsigned firmwares updates are essentially device trees that contain the binary data.

For example, fdtdump <image> on PRIMEGO-4.1.0-Update.img outputs:

/dts-v1/;
// magic:               0xd00dfeed
// totalsize:           0x8d01113 (147853587)
// off_dt_struct:       0x38
// off_dt_strings:      0x8d00d2c
// off_mem_rsvmap:      0x28
// version:             17
// last_comp_version:   16
// boot_cpuid_phys:     0x0
// size_dt_strings:     0x67
// size_dt_struct:      0x8d00cf4

/ {
    timestamp = <0x66ece023>;
    description = "JP11 upgrade image";
    compatible = "inmusic,jp11";
    inmusic,devices = <0x15e4d00c>;
    inmusic,version = "4.1.0";
    images {
        splash {
            description = "Splash screen";
            data = <0xfd377a58 0x5a000004 0xe6d6b446 0x04c08929 ...>
            partition = "splash";
            compression = "xz";
            hash {
                value = <0x4faf3337 0xf95a722d 0xb1b3acf9 0xc3b9b835 0x08a8e9ad>;
                algo = "sha1";
            };
        };
        recoverysplash {
            description = "Update mode splash screen";
            data = <0xfd377a58 0x5a000004 0xe6d6b446 0x04c0be2a ...>;
            partition = "recoverysplash";
            compression = "xz";
            hash {
                value = <0xf48fe31c 0xa9d64549 0xc9bf418e 0xd2f8867b 0x2d179bce>;
                algo = "sha1";
            };
        };
        rootfs {
            description = "Root filesystem";
            data = <0xfd377a58 0x5a000004 0xe6d6b446 0x04c08ddc ...>;
            partition = "rootfs";
            compression = "xz";
            hash {
                value = <0xa4407de0 0xfd5ba759 0x5e1bf541 0x317844a5 0xe591ab1f>;
                algo = "sha1";
            };
        };
    };
};

Metadata

Timestamp (timestamp): The creation or release timestamp of the firmware.
Description (description): A brief description of the firmware image.
Compatibility (compatible): Specifies compatible devices.
Device ID (devices): An identifier for the target device(s).
Firmware Version (version): Indicates the firmware version.

Images

Each firmware may contain multiple images, each with specific properties:

Image Name (images->[image_name]): Unique identifier or name of the image.
- Description (description): Describes the purpose of the image.
- Data (data): Binary data for the image, represented as a series of hexadecimal values.
- Partition (partition): Indicates the target partition for this image (e.g., rootfs, splash, recoverysplash).
- Compression (compression): Specifies the compression type used on this image (e.g., xz).
- Hash (hash): Contains hash information for data integrity:
  - Value (hash->value): The hash value used to verify the data.
  - Algorithm (hash->algo): The hashing algorithm used (e.g., sha1).

Last modified: 05 December 2024