Identity Transaction Family

Overview

On-chain permissioning is desired for transactor key and validator key permissioning. This feature requires that authorized participants for each role be stored. Currently, the only form of identification on the network is the entity's public key. Since lists of public keys are difficult to manage, an identity namespace will be used to streamline managing identities.

The identity system described here is an extensible role and policy based system for defining permissions in a way which can be utilized by other pieces of the architecture. This includes the existing permissioning components for transactor key and validator key, but in the future may also be used by transaction family implementations.

The identity namespace:

• Encompasses ways to identify participants based on public keys
• Stores a set of permit and deny rules called "policies"
• Stores the roles that those policies apply to

Policies describe a set of identities that have permission to perform some action, without specifying the logic of the action itself. Roles simply reference a policy, providing a more flexible interface. For example, a policy could be referenced by multiple roles. This way if the policy is updated, all roles referencing the policy are updated as well. An example role might be named "transactor", and references the policy that controls who is allowed to submit batches and transactions on the network. This example is further described in Transactor Permissioning.

Note

This transaction family will serve as a reference specification and implementation and may also be used in production. A custom implementation can be used so long as they adhere to the same addressing scheme and content format for policies and roles.

State

Policies

A policy will have a name and a list of entries. Each policy entry will have a list of type/key pairs. The type will be either PERMIT_KEY or DENY_KEY. Each key in a type/key pair will be a public key.

// Policy will be stored in a PolicyList to account for hash collisions
message PolicyList {
  repeated Policy policies = 1;
}

message Policy {

  enum EntryType {
    ENTRY_TYPE_UNSET = 0;
    PERMIT_KEY = 1;
    DENY_KEY = 2;
  }

  message Entry {
    // Whether this is a PERMIT_KEY or DENY_KEY entry
    EntryType type = 1;

    // This should a public key or * to refer to all participants.
    string key = 2;
  }

  // name of the policy, this should be unique.
  string name = 1;

  // list of Entries
  // The entries will be processed in order from first to last.
  repeated Entry entries = 2;
}

Roles

A role will be made up of a role name and the name of the policy to be enforced for that role. The data will be stored in state at the address described above using the following protobuf messages:

// Roles will be stored in a RoleList to handle state collisions. The Roles
// will be sorted by name.
message RoleList {
  repeated Role roles = 1;
}

message Role{
  // Role name
  string name = 1;

  // Name of corresponding policy
  string policy_name = 2;
}

Addressing

All identity data will be stored under the special namespace of “00001d”.

For each policy, the address will be formed by concatenating the namespace, the special policy namespace of “00”, and the first 62 characters of the SHA-256 hash of the policy name:

>>> "00001d" + "00" + hashlib.sha256(policy_name.encode()).hexdigest()[:62]

Address construction for roles will follow a pattern similar to address construction in the settings namespace. Role names will be broken into four parts, where parts of the string are delimited by the "." character. For example, the key a.b.c would be split into the parts "a", "b", "c", and the empty string. If a key would have more than four parts the extra parts are left in the last part. For example, the key a.b.c.d.e would be split into "a", "b", "c", and "d.e".

A short hash is computed for each part. For the first part the first 14 characters of the SHA-256 hash are used. For the remaining parts the first 16 characters of the SHA-256 hash are used. The address is formed by concatenating the identity namespace “00001d”, the role namespace “01”, and the four short hashes.

For example, the address for the role client.query_state would be constructed as follows:

>>> "00001d"+ "01" + hashlib.sha256('client'.encode()).hexdigest()[:14]+ \
  hashlib.sha256('query_state'.encode()).hexdigest()[:16]+ \
  hashlib.sha256(''.encode()).hexdigest()[:16]+ \
  hashlib.sha256(''.encode()).hexdigest()[:16]

Transaction Payload

Identity transaction family payloads are defined by the following protocol buffers code:

File: sawtooth-core/families/identity/protos/identity.proto

message IdentityPayload {
    enum IdentityType {
      POLICY = 0;
      ROLE = 1;
    }

    // Which type of payload this is for
    IdentityType type = 1;

    // Serialize bytes of a role or a policy
    bytes data = 2;
}

Transaction Header

Inputs and Outputs

The inputs for Identity family transactions must include:

• the address of the setting sawtooth.identity.allowed_keys
• the address of the role or policy being changed
• if setting a role, the address of the policy to assign to the role

The outputs for Identity family transactions must include:

• the address of the role or policy being changed

Dependencies

None.

Family

• family_name: "sawtooth_identity"
• family_version: "1.0"

Execution

Initially, the transaction processor gets the current values of sawtooth.identity.allowed_keys from the state.

The public key of the transaction signer is checked against the values in the list of allowed keys. If it is empty, no roles or policy can be updated. If the transaction signer is not in the allowed keys the transaction is invalid.

Whether this is a role or a policy transaction is checked by looking at the IdentityType in the payload.

If the transaction is for setting a policy, the data in the payload will be parsed to form a Policy object. The Policy object is then checked to make sure it has a name and at least one entry. If either are missing, the transaction is considered invalid. If the policy is determined to be whole, the address for the new policy is fetched. If there is no data found at the address, a new PolicyList object is created, the new policy is added, and the policy list is applied to state. If there is data, it is parsed into a PolicyList. The new policy is added to the policy list, replacing any policy with the same name, and the policy list is applied to state.

If the transaction is for setting a role, the data in the payload will be parsed to form a Role object. The Role object is then checked to make sure it has a name and a policy_name. If either are missing, the transaction is considered invalid. The policy_name stored in the role must match a Policy already stored in state, if no policy is found stored at the address created by the policy_name, the transaction is invalid. If the policy exist, the address for the new role is fetched. If there is no data found at the address, a new RoleList object is created, the new role is added, and the policy list is applied to state. If there is data, it is parsed into a RoleList. The new role is added to the role list, replacing any role with the same name, and the role list is applied to state.