NVS Partition Generator Utility

Introduction

The utility nvs_flash/nvs_partition_generator/nvs_partition_gen.py creates a binary file, compatible with the NVS architecture defined in Non-Volatile Storage Library, based on the key-value pairs provided in a CSV file.

This utility is ideally suited for generating a binary blob, containing data specific to ODM/OEM, which can be flashed externally at the time of device manufacturing. This allows manufacturers to generate many instances of the same application firmware with customized parameters for each device, such as a serial number.

Prerequisites

To use this utility in encryption mode, install the following packages:

• cryptography

All the required packages are included in requirements.txt in the root of the ESP-IDF directory.

CSV File Format

Each line of a CSV file should contain 4 parameters, separated by a comma. The table below describes each of these parameters.

No.	Parameter	Description	Notes
1	Key	Key of the data. The data can be accessed later from an application using this key.
2	Type	Supported values are file, data, and namespace.
3	Encoding	Supported values are: u8, i8, u16, i16, u32, i32, u64, i64, string, hex2bin, base64, and binary. This specifies how actual data values are encoded in the resulting binary file. The difference between the string and binary encoding is that string data is terminated with a NULL character, whereas binary data is not.	As of now, for the file type, only hex2bin, base64, string, and binary encoding is supported.
4	Value	Data value	Encoding and Value cells for the namespace field type should be empty. Encoding and Value of namespace are fixed and are not configurable. Any values in these cells are ignored.

Note

The first line of the CSV file should always be the column header and it is not configurable.

Below is an example dump of such a CSV file:

key,type,encoding,value     <-- column header
namespace_name,namespace,,  <-- First entry should be of type "namespace"
key1,data,u8,1
key2,file,string,/path/to/file

Note

Make sure there are no spaces :

• before and after ','

• at the end of each line in a CSV file

NVS Entry and Namespace Association

When a namespace entry is encountered in a CSV file, each following entry will be treated as part of that namespace until the next namespace entry is found. At this point, all the following entries will be treated as part of the new namespace.

Note

First entry in a CSV file should always be a namespace entry.

Multipage Blob Support

By default, binary blobs are allowed to span over multiple pages and are written in the format mentioned in Section Structure of Entry. If you intend to use the older format, the utility provides an option to disable this feature.

Encryption-Decryption Support

The NVS Partition Generator utility also allows you to create an encrypted binary file and decrypt an encrypted one. The utility uses the XTS-AES encryption. Please refer to NVS Encryption for more details.

Running the Utility

Usage :

python nvs_partition_gen.py [-h] {generate,generate-key,encrypt,decrypt} ...

Optional Arguments :

No.	Parameter	Description
1	-h / --help	Show the help message and exit

Commands :

Run nvs_partition_gen.py {command} -h for additional help

No.	Parameter	Description
1	generate	Generate NVS partition
2	generate-key	Generate keys for encryption
3	encrypt	Generate NVS encrypted partition
4	decrypt	Decrypt NVS encrypted partition

Generate NVS Partition (Default)

Usage :

python nvs_partition_gen.py generate [-h] [--version {1,2}] [--outdir OUTDIR] input output size

Positional Arguments :

Parameter	Description
input	Path to CSV file to parse
output	Path to output NVS binary file
size	Size of NVS partition in bytes (must be multiple of 4096)

Optional Arguments :

Parameter	Description
-h / --help	Show the help message and exit
--version {1,2}	Set multipage blob version (Default: Version 2) Version 1 - Multipage blob support disabled Version 2 - Multipage blob support enabled
--outdir OUTDIR	Output directory to store file created (Default: current directory)

You can run the utility to generate NVS partition using the command below. A sample CSV file is provided with the utility:

python nvs_partition_gen.py generate sample_singlepage_blob.csv sample.bin 0x3000

Generate Encryption Keys Partition

Usage :

python nvs_partition_gen.py generate-key [-h] [--keyfile KEYFILE] [--outdir OUTDIR]

Optional Arguments :

Parameter	Description
-h / --help	Show the help message and exit
--keyfile KEYFILE	Path to output encryption keys file
--outdir OUTDIR	Output directory to store files created. (Default: current directory)

You can run the utility to generate only the encryption key partition using the command below:

python nvs_partition_gen.py generate-key

Generate Encrypted NVS Partition

Usage :

python nvs_partition_gen.py encrypt [-h] [--version {1,2}] [--keygen]
                                    [--keyfile KEYFILE] [--inputkey INPUTKEY] [--outdir OUTDIR]
                                    input output size

Positional Arguments :

Parameter	Description
input	Path to CSV file to parse
output	Path to output NVS binary file
size	Size of NVS partition in bytes (must be multiple of 4096)

Optional Arguments :

Parameter	Description
-h / --help	Show the help message and exit
--version {1,2}	Set multipage blob version (Default: Version 2) Version 1 - Multipage blob support disabled Version 2 - Multipage blob support enabled
--keygen	Generates key for encrypting NVS partition
--keyfile KEYFILE	Path to output encryption keys file
--inputkey INPUTKEY	File having key for encrypting NVS partition
--outdir OUTDIR	Output directory to store file created (Default: current directory)

You can run the utility to encrypt NVS partition using the command below. A sample CSV file is provided with the utility:

• Encrypt by allowing the utility to generate encryption keys:

  python nvs_partition_gen.py encrypt sample_singlepage_blob.csv sample_encr.bin 0x3000 --keygen
  

Note

Encryption key of the format <outdir>/keys/keys-<timestamp>.bin is created.

• Encrypt by allowing the utility to generate encryption keys and store it in provided custom filename:

  python nvs_partition_gen.py encrypt sample_singlepage_blob.csv sample_encr.bin 0x3000 --keygen --keyfile sample_keys.bin
  

Note

• Encryption key of the format <outdir>/keys/sample_keys.bin is created.

• This newly created file having encryption keys in keys/ directory is compatible with NVS key-partition structure. Refer to NVS Key Partition for more details.

• Encrypt by providing the encryption keys as input binary file:

  python nvs_partition_gen.py encrypt sample_singlepage_blob.csv sample_encr.bin 0x3000 --inputkey sample_keys.bin
  

Decrypt Encrypted NVS Partition

Usage :

python nvs_partition_gen.py decrypt [-h] [--outdir OUTDIR] input key output

Positional Arguments :

Parameter	Description
input	Path to encrypted NVS partition file to parse
key	Path to file having keys for decryption
output	Path to output decrypted binary file

Optional Arguments :

Parameter	Description
-h / --help	Show the help message and exit
--outdir OUTDIR	Output directory to store files created. (Default: current directory)

You can run the utility to decrypt encrypted NVS partition using the command below:

python nvs_partition_gen.py decrypt sample_encr.bin sample_keys.bin sample_decr.bin

You can also provide the format version number:

• Multipage blob support disabled (Version 1)

• Multipage blob support enabled (Version 2)

Multipage Blob Support Disabled (Version 1)

You can run the utility in this format by setting the version parameter to 1, as shown below. A sample CSV file for the same is provided with the utility:

python nvs_partition_gen.py generate sample_singlepage_blob.csv sample.bin 0x3000 --version 1

Multipage Blob Support Enabled (Version 2)

You can run the utility in this format by setting the version parameter to 2, as shown below. A sample CSV file for the same is provided with the utility:

python nvs_partition_gen.py generate sample_multipage_blob.csv sample.bin 0x4000 --version 2

Note

• Minimum NVS Partition Size needed is 0x3000 bytes.

• When flashing the binary onto the device, make sure it is consistent with the application's sdkconfig.

Caveats

• Utility does not check for duplicate keys and will write data pertaining to both keys. You need to make sure that the keys are distinct.

• Once a new page is created, no data will be written in the space left on the previous page. Fields in the CSV file need to be ordered in such a way as to optimize memory.

• 64-bit datatype is not yet supported.