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Authorization and authentication

GalaChain uses two layers of authorization and authentication to ensure that only authorized users can access the system. First level, exposed to the client, is based on secp256k1 signatures and private/public key authorization. Second level uses native Hyperledger Fabric CA users and organizations MSPs.

How it works

  1. Client application signs the transaction with the end user private key.
  2. GalaChain REST API uses custom CA user credentials to call the chaincode.
  3. Chaincode checks the MSP of the CA user (Organization based authorization).
  4. Chaincode recovers the end user public key from the dto and signature, and verifies if the end user is registered (Signature based authorization).
  5. The transaction is executed if both checks pass.

Note the difference between the end user and the CA user. The end user is the person who is using the client application, while the CA user is the system-level application user that is used to call the chaincode.

In this document, if we refer to the user, we mean the end user.

Signature based authorization

Signature based authorization user secp256k1 signatures to verify the identity of the end user. It uses the same algorithm as Ethereum.

Signing the transaction payload

Client side it is recommended to use @gala-chain/api, or @gala-chain/cli, or @gala-chain/connect library to sign the transactions. These libraries will automatically sign the transaction in a way it is compatible with GalaChain.

Using @gala-chain/api:

import { createValidDto } from '@gala-chain/api';
import { ChainCallDTO } from "./dtos";
import { signatures } from "./index";

class MyDtoClass extends ChainCallDTO { ... }

// recommended way to sign the transaction
const dto1 = await createValidDto(MyDtoClass, {myField: "myValue"}).signed(userPrivateKey);

// alternate way, imperative style
const dto2 = new MyDtoClass({myField: "myValue"});

// when you don't have the dto class, but just a plain object
const dto3 = {myField: "myValue"};
dto3.signature = signatures.getSignature(dto3, Buffer.from(userPrivateKey));

Using @gala-chain/cli:

galachain dto:sign -o=./output/path.json ./priv-key-file '{ "myField": "myValue" }'

Using @gala-chain/connect:

For the @gala-chain/connect library, signing is done automatically when you call the sendTransaction method, and it is handled by MetaMask wallet provider.

import { GalachainConnectClient } from "@gala-chain/connect";

const client = new GalaChainConnectClient(contractUrl);
await client.connectToMetaMask();

const dto = ...;
const response = await client.send({ method: "TransferToken", payload: dto });

"Manual" process:

If you are not using any of the libraries, you can sign the transaction with the following steps:

  1. You need to have secp256k1 private key of the end user.
  2. Given the transaction payload as JSON object, you need to serialize it to a string in a way that it contains no additional spaces or newlines, fields are sorted alphabetically, and all BigNumber values are converted to strings with fixed notation. Also, you need to exclude top-level signature and trace fields from the payload.
  3. You need to hash the serialized payload with keccak256 algorithm (note this is NOT the same algorithm as SHA-3).
  4. You need to get the signature of the hash using the private key, and add it to the payload as a signature field. The signature should be in the format of rsv array, where r and s are 32-byte integers, and v is a single byte.

It is important to follow these steps exactly, because chain side the same way of serialization and hashing is used to verify the signature. If the payload is not serialized and hashed in the same way, the signature will not be verified.

Authenticating and authorizing in the chaincode

In the chaincode, before the transaction is executed, GalaChain SDK will recover the public key from the signature and check if the user is registered. If the user is not registered, the transaction will be rejected with an error.

By default @Submit and @Evaluate decorators for contract methods enforce signature based authorization. The @GalaTransaction decorator is more flexible and can be used to disable signature based authorization for a specific method. Disabling signature based authorization is useful when you want to allow anonymous access to a method, but it is not recommended for most use cases.

Chain side ctx.callingUser property will be populated with the user's alias, which is either client|<custom-name> or eth|<eth-addr> (if there is no custom name defined). Also, ctx.callingUserEthAddress will contain the user's Ethereum address. This way it is possible to get the current user's properties in the chaincode and use them in the business logic.

Additionally, we plan to support role-based access control (RBAC) in the future, which will allow for more fine-grained control over who can access what resources. See the RBAC section for more information.

User registration

Gala chain does not allow anonymous users to access the chaincode. In order to access the chaincode, the user must be registered with the chaincode. There are two methods to register a user:

  1. RegisterUser method in the PublicKeyContract.
  2. RegisterEthUser method in the PublicKeyContract.

Both methods require the user to provide their secp256k1 public key. The only difference between these two methods is that RegisterEthUser does not require the alias parameter, and it uses the Ethereum address (prefixed with eth|) as the user's alias.

Access to RegisterUser and RegisterEthUser methods is restricted on the organization level. Only the organization that is specified in the chaincode as CURATOR_ORG_MSP environment variable can access these methods (it's CuratorOrg by default). Technically that means that the client application must use the CA user that is registered with the CuratorOrg organization to call these methods. See the Organization based authorization section for more information.

Default admin user

When the chaincode is deployed, it contains a default admin end user. It is provided by two environment variables: * DEV_ADMIN_PUBLIC_KEY - it contains the admin user public key (sample: 88698cb1145865953be1a6dafd9646c3dd4c0ec3955b35d89676242129636a0b). * DEV_ADMIN_USER_ID - it contains the admin user alias (sample: client|admin; this variable is optional),

If the user profile is not found in the chain data, and the public key recovered from the signature is the same as the admin user public key (DEV_ADMIN_PUBLIC_KEY), the admin user is set as the calling user. Additionally, if the admin user alias is specified (DEV_ADMIN_USER_ID), it is used as the calling user alias. Otherwise, the default admin user alias is eth|<eth-addr-from-public-key>.

The admin user is required to register other users.

For GalaChain TestNet the admin user public key is specified by the adminPublicKey registration parameter.

Note the admin uses is an end user, not a CA user, and it cannot bypass the organization based authorization. If you want to use the admin user to register other users, you need to use the CA user that is registered with the curator organization.

Organization based authorization

Organization based authorization uses Hyperledger Fabric CA users and organizations MSPs to verify the identity of the caller. It is used to restrict access to the chaincode method to a specific organization.

You can restrict access to the contract method to a specific organizations by setting the allowedOrgs property in the @GalaTransaction.

    allowedOrgs: ["SomeRandomOrg"]

For the PublicKeyContract chaincode, the CURATOR_ORG_MSP environment variable is used as the organization that is allowed to register users (default value is CuratorOrg). It is recommended to use the same variable for curator-level access to the chaincode methods.

Next: Role Based Access Control (RBAC)

GalaChain v2 will drop support for the chaincode level authorization using Orgs and MSPs. Instead, we will introduce a new Role Based Access Control (RBAC) system that will allow for more fine-grained control over who can access what resources.

The allowedOrgs property will be removed from the chaincode definition and replaced with a new allowedRoles property. For instance, instead of specifying that only CuratorOrg can access a certain chaincode, you will be able to specify that only users with the CURATOR role can access it. User roles will be saved with UserProfile objects in chain data.

See the current progress in the RBAC issue.