PublicKey Info Base » History » Revision 78
Revision 77 (Yingdi Yu, 03/03/2015 04:42 PM) → Revision 78/79 (Davide Pesavento, 06/28/2020 02:27 PM)
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 INTEGER 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 INTEGER DEFAULT 0, FOREIGN KEY(identity) REFERENCES identities(identity) ON DELETE CASCADE ); A unique index is created on (identity, key_id). Certificate table schema: certificates( 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 INTEGER 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: mgmt( 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 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/[UserName]/dsk-...`. The PIB instance key is signed by another key with the name `/localhost/pib/[UserName]/ksk-...` which is the trust anchor of the PIB service. Note that it is difference from the management key name which is `/localhost/pib/`**user**`/[UserName]/dsk-...`. Management key is used by PIB owner to sign update/delete command interest, while PIB instance key is used by PIB service to sign PIB responses. ### `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 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 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 PibUser | 144 | 0x90 PibIdentity | 145 | 0x91 PibPublicKey | 146 | 0x92 PibCertificate | 147 | 0x93 PibBytes | 148 | 0x94 PibDefaultOpt | 149 | 0x95 PibNameList | 150 | 0x96 PibType | 151 | 0x97 PibError | 152 | 0x98 PibTpmLocator | 153 | 0x99 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.