PublicKey Info Base » History » Revision 69
Revision 68 (Yingdi Yu, 03/01/2015 08:49 PM) → Revision 69/79 (Yingdi Yu, 03/02/2015 11:27 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.
PIB service is run as a separate service for each user.
Users' public key information is managed in three tables in PIB: identity table, key table, and certificate table.
Identity table schema:
Identities(
id INTEGER PRIMARY KEY,
identity BLOB NOT NULL,
is_default INETEGER DEFAULT 0
);
A unique index is created on (identity).
Key table schema:
Keys(
id INTEGER PRIMARY KEY,
identity BLOB NOT NULL,
key_id BLOB NOT NULL,
key_type INTEGER NOT NULL,
key_bits BLOB NOT NULL,
is_default INETEGER DEFAULT 0,
FOREIGN KEY(identity) REFERENCES identities(identity) ON DELETE CASCADE
);
A unique index is created on (identity, key_id).
Certificate table schema:
Certificate(
id INTEGER PRIMARY KEY,
certificate_name BLOB NOT NULL,
identity BLOB NOT NULL,
key_id BLOB NOT NULL,
certificate_data BLOB NOT NULL,
is_default INETEGER DEFAULT 0,
FOREIGN KEY(identity, key_id) REFERENCES keys(identity, key_id) ON DELETE CASCADE
);
A unique index is created on (certificate_name).
Besides these tables PIB has one more management tables: `mgmt` table.
`mgmt` table stores owner name, corresponding tpm locator, and local management key (we will discuss it later).
User table schema:
User(
id INTEGER PRIMARY KEY
owner BLOB NOT NULL,
tpm_locator BLOB,
local_management_cert BLOB NOT NULL,
);
The read access to PIB is not restricted,
while the write access to PIB 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 local management key is allowed to change anything in the PIB info in the three tables. The identity of the user local management key is `/localhost/pib/user/[UserName]`, and the name of the key should be `/localhost/pib/user/[UserName]/[KeyId]`. Adding a new normal user's local management key is not restricted for now, because we expect in future that OS will prevent a user from registering another user in PIB. However, changing a existing user's local management key requires a signature generated by the existing 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`. Importing a self-signed regular key requires the signature generated by the corresponding user's local management key.
## 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.
Five types of operations are defined:
Verb | Access Type | Description
-------------------- | ----------------- | ----------------------------------------------------------
Get | Read | Get a single entity (user, identity, key, or certificate)
Default | Read | Get the default setting of an entity
List | Read | List the name of a set of entities
Update | Write | Add/Change an entity
Delete | Write | Delete an entity
`Param` is a TLV block containing parameters of the query.
Different types of operations have their own parameters.
### 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.
Several TLVs are defined for the content of query responses.
`Identity` TLV:
PibIdentity := PIB-IDENTITY-TYPE TLV-LENGTH
Name
`PublicKey` TLV:
PibPublicKey := PIB-PUBLIC-KEY-TYPE TLV-LENGTH
Name
PibBytes
`Certificate` TLV:
PibCertificate := PIB-CERTIFICATE-TYPE TLV-LENGTH
Data
`User` TLV:
PibUser := PIB-USER-TYPE TLV-LENGTH
Data // local management certificate
... // Other information to add if exists
A response may also be a error code defined a non-negative integer:
PibError := PIB-ERROR-TYPE TLV-LENGTH
ErrorCode
Bytes
ErrorCode := ERROR-CODE-TYPE TLV-LENGTH
nonNegativeInteger
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
A response is signed by a PIB instance key with the name `/localhost/pib/<user_name>/dsk-...`. `/localhost/pib/dsk-...`.
The PIB instance key is signed by another key with the name `/localhost/pib/<user_name>/ksk-...` `/localhost/pib/ksk-...` which is the trust anchor of the PIB service.
### `Get` Parameters
For `get` operation, `Param` is defined as:
PibGetParam := PIB-GET-PARAM-TYPE TLV-LENGTH
PibType
Name?
`Type` indicates which table the query will be applied eventually.
PibType := PIB-TYPE-TYPE TLV-LENGTH
nonNegativeInteger
Type constant | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
USER | 0 | 0x00
ID | 1 | 0x01
KEY | 2 | 0x02
CERT | 3 | 0x03
`Name` is the name of the queried entity. It is a TLV defined in [NDN-TLV spec](http://named-data.net/doc/ndn-tlv/name.html#name).
Name is ignored if type is USER.
If error happens during processing the query, the content of the response is an ErrorCode TLV.
If no error happens, the content depends on the `Type`.
When `Type` is `ID`, the query is actually invalid.
The response is an ErrorCode with value `ERR_WRONG_PARAM`.
For `USER`, the content is a `PibUser` TLV.
For `KEY`, the content is a `PibPublicKey` TLV.
For `CERT`, the content is a `PibCertificate` TLV.
### `Default` Parameters
The parameters of `default` operation is defined as.
PibDefaultParam := PIB-DEFAULT-PARAM-TYPE TLV-LENGTH
PibType // target type
PibType // origin type
Name? // origin name
The response to a `default` query is the default entity of the "target type" of the "origin".
Possible values of target type include `ID`, `KEY`, and `CERT`.
Possible values of origin type include `USER`, `ID`, and `KEY`.
The target type should be always "below" the origin type (e.g., it is wrong to have a target type `ID` and an origin type `CERT`.)
The origin name should be consistent with the origin type.
Origin name is ignored if origin type is `USER`.
When wrong parameters are supplied, the content of response is an ErrorCode with value `ERR_WRONG_PARAM`.
If no error happens in processing the query, the response could be `PibIdentity`, `PibPublicKey`, or `PibCertificate`, depending on the target type.
### `List` Parameters
The parameters of `list` operation are defined as:
PibListParam := PIB-LIST-PARAM-TYPE TLV-LENGTH
PibType // origin type
Name? // origin name
The response to the `list` query is a list of `Name`, depending on the origin type.
Possible values of origin type include `USER`, `ID`, and `KEY`.
Origin name is ignored if origin type is `USER`.
If the origin type is `USER`, the response is a list of identities of the user.
If the origin type is `ID`, the response is a list of names of keys of the identity.
If the origin type is `KEY`, the response is a list of names of certificates of the key.
PibNameList := PIB-NAME-LIST-TYPE TLV-LENGTH
Name+
### `Update` Parameters
The parameters of `update` operation are defined as:
PibUpdateParam := PIB-UPDATE-PARAM-TYPE TLV-LENGTH
(PibUser | PibIdentity | PibPublicKey | PibCertificate)
PibDefaultOpt
`DefaultOpt` is the default option:
PibDefaultOpt := PIB-DEFAULT-OPT-TYPE TLV-LENGTH
nonNegativeInteger
DefaultOpt constant | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
DEFAULT\_OPT\_NO | 0 | 0x00
DEFAULT\_OPT\_KEY | 1 | 0x01
DEFAULT\_OPT\_ID | 3 | 0x03
DEFAULT\_OPT\_USER | 7 | 0x07
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 `PibDefaultOpt`.
The response is always an ErrorCode: `ERR_SUCCESS` for a successful operation, others for failure.
### `Delete` Parameters
The parameters of `delete` operation are defined as:
PibDeleteParam := PIB-DELETE-PARAM-TYPE TLV-LENGTH
PibType
Name
The entity and its belonging entities will be deleted once the operation is validated.
The response is always an ErrorCode: `ERR_SUCCESS` for a successful deletion, others for failure.
### TLV-TYPE assignments
Type | Assigned value | Assigned value (hex)
----------------------------------------------- | ----------------- | --------------------
PibGetParam | 128 | 0x80
PibDefaultParam | 129 | 0x81
PibListParam | 130 | 0x82
PibUpdateParam | 131 | 0x83
PibDeleteParam | 132 | 0x84
PibType | 144 | 0x90
PibIdentity | 145 | 0x91
PibPublicKey | 146 | 0x92
PibCertificate | 147 | 0x93
PibBytes | 148 | 0x94
PibDefaultOpt | 149 | 0x95
PibNameList | 150 | 0x96
PibUser | 151 | 0x97
PibError | 152 | 0x98
PibErrorCode | 252 | 0xfc
## Misc
In that case root user's private key is lost in TPM, you have to delete the root user directly in the database.
Since the database file is guarded by filesystem, only system admin can do that.