PublicKey Info Base » History » Revision 40
Revision 39 (Yingdi Yu, 07/16/2014 09:39 AM) → Revision 40/79 (Yingdi Yu, 07/16/2014 09:45 AM)
Public key Info Base (PIB) Service
==================================
## Public Key Info Management
NDN data packets are secured through digital signatures.
In order to generate a valid signature, an NDN application needs to know not only the correct key to use but also the correct public key information that should be put into the `KeyLocator` of a data packet.
The information needs to be managed locally on the system where the application is running.
The information related to keys is managed at three granularities: identities, keys, and certificates.
A key is always associated with a namespace, called "identity".
An identity however may have more than one keys.
Each key is named as `/<Identity>/[KeyId]`.
The `KeyId` uniquely identifies a key which belongs to the `Identity`.
Among these keys, only one is the default key of the identity.
If only identity is provided when signing a packet, the default key of the identity will be used to sign the packet.
A certificate is always associated with the key in the certificate
If a certificate is provided when signing a packet, the corresponding private key should be used to sign the packet
and the name of the certificate name may be put into the `KeyLocator` of the packet.
A key may have more than one certificates (e.g., certificates may be issued by different parties).
Among these certificates, only one is the default certificate of the key.
The default certificate of the default key of an identity is the default certificate of the identity.
If only identity is provided when signing a packet, the name of the default certificate of the identity may be put into the `KeyLocator` of the packet.
All the information above may be accessed by different APIs and applications on the same system,
therefore it is desirable to make the information provisioning as a system service.
Since public keys and certificates are supposed to be publicly available,
the service also serves as a local storage of certificate and public keys,
besides providing the public key related information.
## PIB management model
The public key information of each system user is managed separately in PIB.
For now, PIB service is a system service (i.e., run by root).
PIB service may be separated into several user services (i.e., run by each user) in the future.
Each user has three tables in PIB: identity table, key table, and certificate table.
The public key information of a user is managed in these tables.
Identity table consists of two columns: `identity` (primary key) and `default_key_id`.
Identity table schema:
User_[UserName]_ID(
identity BLOB NOT NULL,
default_key_id BLOB,
PRIMARY KEY (identity)
);
Key Table consists of five columns: `identity`, `key_id`, `key_type`, `key_bits`, and `default_cert_name`.
The combination of `identity` and `key_id` is the primary key of key table.
Key table schema:
User_[UserName]_KEY(
identity BLOB NOT NULL,
key_id BLOB NOT NULL,
key_type INTEGER NOT NULL,
key_bits BLOB NOT NULL,
default_cert_name BLOB,
PRIMARY KEY (identity, key_id)
);
Certificate table consists of four columns: `certificate_name` (primary key), `identity`, `key_id`, and `certificate_data`.
Certificate table schema:
User_[UserName]_CERT(
certificate_name BLOB NOT NULL,
identity BLOB NOT NULL,
key_id BLOB NOT NULL,
certificate_data BLOB NOT NULL,
PRIMARY KEY (certificate_name)
);
Besides the tables for each user, PIB has two more management tables: user table and certificate_publishing table.
User table stores user's local management key (we will discuss it later) and user's default identity
Each user has its own default identity.
From the default identity, the default key and certificate of the user can be derived.
User table schema:
User(
user_name BLOB NOT NULL,
has_default_identity INTEGER DEFAULT 0,
default_identity BLOB,
local_management_cert BLOB NOT NULL,
PRIMARY KEY (user_name)
);
Certificate_Publishing table schema:
Certificate_Publishing(
user_name BLOB NOT NULL,
publish_namespace BLOB NOT NULL,
PRIMARY KEY (user_name, publish_namespace)
);
The read access to a user's public key information is not restricted,
while the write access to a user's public key information requires authentication.
The write access is expressed as signed commands.
The signing key can be authenticated only if the key already exists in the corresponding user's PIB tables.
Each key has its own write access privilege which is defined as:
* The root user has the **root key** of the local system. The root key has the highest privilege, i.e., its owner is allowed to change anything in PIB. The identity of the root key is `/localhost`, and the name of the root key should be `/localhost/[KeyId]`.
* Each user has its own **local management key**. The local management key is allowed to change anything in the user's PIB info including the three tables and user's own entry in the user table. The identity of the user local management key is `/localhost/user/[UserName]`, and the name of the key should be `/localhost/user/[UserName]/[KeyId]`. Note that the local management key of the root user is the root key.
* All the other keys are called **regular keys**. A regular key is allowed to change keys/certificates with identities under the key's own namespace, e.g., a key with the identity `/ndn/ucla/alice` is allowed to change a key with the identity `/ndn/ucla/alice/chat` but is not allowed to change a key with the identity `/ndn/ucla/bob`.
## PIB Service Protocol
PIB service provides an interface to NDN applications for public key info lookup.
The interface is defined in terms of NDN packets (interest/data).
Depending on the query type, a query to PIB is expressed as a **[signed interest](http://redmine.named-data.net/projects/ndn-cxx/wiki/SignedInterest)** (for Write operation) or normal interest (for Read operation).
The query interest is defined as:
/localhost/pib/[UserName]/[Verb]/[Param]/<signed_interest_security_components>
|<-- Required for Write operation -->|
`UserName` indicates the tables in which the query should apply.
`Verb` indicates the access operation.
Four types of operations are defined:
Verb | Access Type
-------------------- | -----------------
ID | 0
KEY | 1
CERT | 2
`get` (Read), `search` (Read), `update` (Write), and `delete` (Write).
The operation `get` and `search` are quite similar to each other.
The only difference is that the response to `get` is the queried entity per se while the response to `search` operation is the existence (a boolean value) of the queried entity.
`Param` is a TLV block containing parameters of the query.
Different types of operations have their own parameters.
### `Get` Parameters
For `get` operation, `Param` is defined as:
GetParam := Type
Filter
Filter := DirectFilter | DefaultOfFilter | ListOfFilter
DirectFilter := Name
DefaultOfFilter := Type
Name
ListOfFilter := Type
Name
Type := ID | KEY | CERT
`Type` indicates which table the query will be applied eventually.
`Filter` indicates how to apply the query.
When `Name` is specified in `Filter`, PIB will directly lookup the entry with the same name in the table indicated by `Type`.
When `DefaultOf` is specified in `Filter`, PIB will first derive the name of the target through the default information and lookup the entry in the table indicated by `Type`.
When `ListOf` is specified in `Filter`, PIB will collect all the entries that satisfy the condition specified in `ListOf`.
Here are some examples of `GetParam`:
GetParam
{
Type: KEY
DirectFilter
{
Name: /ndn/edu/ucla/ksk-1234
}
}
The example above is a query to get a key with the name `/ndn/edu/ucla/ksk-1234`.
GetParam
{
Type: CERT
DefaultOfFilter
{
Type: ID
Name: /ndn/edu/ucla/alice
}
}
The example above is a query to get the default certificate of an identity `/ndn/edu/ucla/alice`.
GetParam
{
Type: CERT
ListOfFilter
{
Type: KEY
Name: /ndn/edu/ucla/ksk-1234
}
}
The example above is a query to get a list of certificates of a key `/ndn/edu/ucla/alice`.
### `Search` Parameters
The parameters of `search` operation is quite similar to `get` operation except that there is no `ListOf` filter.
SearchParam := Type
Filter
Filter := NameFilter | DefaultOfFilter
NameFilter := Name
DefaultOfFilter := Type
Name
Type := ID | KEY | CERT
The response to `search` operation is a boolean value to indicate the existence of the searched entity
### `Update` Parameters
The parameters of `update` operation are defined as:
UpdateParam := Entity
DefaultOpt
Entity := Identity | PublicKey | Certificate
Identity := Name
PublicKey := Name
Bytes
Certificate := Data
DefaultOpt := USER_DEFAULT | ID_DEFAULT | KEY_DEFAULT | NO_DEFAULT
The operation, once validated, will add a new entry in the corresponding table if no such an entry exists or update the existing entry,
and change the default setting according to `DefaultOpt`.
### `Delete` Parameters
The parameters of `delete` operation are defined as:
DeleteParam := Type
Name
Type := ID | KEY | CERT
The entity and its belonging entities will be deleted once the operation is validated.
### TLV-TYPE assignments
Type | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
GetParam | 128 | 0x80
SearchParam | 129 | 0x81
UpdateParam | 130 | 0x82
DeleteParam | 131 | 0x83
Type | 132 | 0x84
NameFilter | 133 | 0x85
DefaultOfFilter | 134 | 0x86
ListOfFilter | 135 | 0x87
Identity | 136 | 0x88
PublicKey | 137 | 0x89
Certificate | 138 | 0x8a
Bytes | 139 | 0x8b
DefaultOpt | 140 | 0x8c
### Constant value assignments
For type `Type`:
Constant | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
ID | 0 | 0x00
KEY | 1 | 0x01
CERT | 2 | 0x02
For type `DefaultOpt`:
Constant | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
NO_DEFAULT | 0 | 0x00
USER_DEFAULT | 1 | 0x01
ID_DEFAULT | 2 | 0x02
KEY_DEFAULT | 3 | 0x03
### Query Responses
The response to a query interest is a data packet signed by PIB.
The public key certificate of PIB is stored in a read-only file and is accessible to all users on the system.
The content of the response to `get` operation could be one of the three TLV defined above: `Identity` (0x8b), `PublicKey` (0x8c), and `Certificate` (0x8d), or a list of these TLVs.
The content of the response to `search` operation is a byte. Non-zero byte stands for true while 0x00 stands for false.
The content of the response to `update` or `delete` operation is an uint32_t which serves as an error code.
0 stands for success while non-zero byte stands for failure.
Error code:
Error code | Value | Description
----------------------------- | ----------------- | ----------------------------------
ERR\_SUCCESS | 0 | No error
ERR\_INCOMPLETE\_COMMAND | 1 | Incomplete interest
ERR\_WRONG\_VERB | 2 | Wrong verb in interest
ERR\_WRONG\_PARAM | 3 | Wrong parameter in interest
ERR\_NON\_EXISTING\_USER | 128 | User does not exist
ERR\_NON\_EXISTING\_ID | 129 | Identity does not exist
ERR\_NON\_EXISTING\_KEY | 130 | Public key does not exist
ERR\_NON\_EXISTING\_CERT | 131 | Certificate does not exist
ERR\_NO\_DEFAULT\_ID | 256 | No default identity is set
ERR\_NO\_DEFAULT\_KEY | 257 | No default public key is set
ERR\_NO\_DEFAULT\_CERT | 258 | No default certificate is set
ERR\_DELETE\_DEFAULT\_SETTING | 384 | Trying to delete default setting