The SightingDB format is in the JSON [@!RFC8259] format. In SightingDB, a Sighting Object is composed of a single JSON object. This object contains the following fields: value, first_seen, last_seen, count, tags, ttl, frequency and manifold.
### Attribute Storage
The fields described previously describe an Attribute and all the required characteristics. However they are stored in a Namespace. A Namespace is similar to a path in a filesystem where the same file can be stored in multiple places.
A Namespace with multiple levels **MUST** be separated with the slash '/' character. There is no specification on how they are structured, since it depends on the use cases.
A Namespace starting with the underscore '_' character means it is private and internal to SightingDB. There are all reserved for the engine and **MUST** NOT be used.
The attribute value, used to store and retrieve information about an attribute. Note that value is not returned back in the JSON object, since it is queried, it is known. The Value is described in a section below, as it is very specific and can be either "as is", a hash, encoded in base64 or any other convenient mechanism.
The value implementation **MUST** offer at least: 1) Raw value 2) Base64 URL Encoded 3) SHA256 Hash
Time in UTC of the first time this value was captured
#### last_seen
Time in UTC of the last time this value was captured
#### count
How many time this value was written
#### tags
Tags follow how they are defined in MISP using the MISP Taxonomy. Each Tag is separated with the ';' character.
#### ttl
Time To Live, represents the expiration in seconds since the time the Attribute was created. Once it has expired, it moves in the private Namespace _expired.
When an Attribute has this field set to 0, it means it is not set to expired. This is the default behavior.
When an Attribute has this field set to a number greater than 0, the expiration status is computed only at retrieval time.
When a given Attribute Value is stored in different namespaces, the manifold field keeps track of them so it returns in how many different places this attributes exists. This is a simple counter.
The value submitted can be in multiple format according to the use-case. Any implementation **MUST** offer three alternatives:
1) Raw value: where nothing is encoded and the value is stored AS IS, such as show in the example above with the One Attribute in JSON.
2) SHA256: which prevents from seeing content (see Security Considerations), has a fixed size and is convenient for most requirements
3) Base64 URL: Where the specification of Base64 is followed, except the characters conflicting with an URL argument are replaced
The value is configured as part of the Namespace. The private "_config" Namespace prefix stores this value storage mechanism.
## Configuring the value format for a Namespace
If one has the Namespace "/Organization1/BU1/ip" and want to store those IP addresses in SHA256, it will be configured like this:
The Namespace is kept but prefixed by "_config" and has a json object about value format set.
"/_config/Organization1/BU1/ip"
~~~~
{
"value_format":"SHA256"
}
~~~~
Where "value_format" is either: "SHA256", "RAW" or "BASE64URL".
# Security Considerations
While this document solely focuses on the format, the reference implementation is SightingDB. The authentication, the data access is not handled by SightingDB.
It is possible a value can leak if the access is too permissive.
Even a Hashed value can be discovered, as re-hashing known values would match.