Web API (JSON/HTTPS)

Both the cloud and on-premises versions of Structurizr provide a JSON/HTTPS API for getting and putting workspaces, and a number of client libraries are available for a diagrams as code or diagrams as text approach.

The API consists of two endpoints, to get and put a workspace definition respectively.

  • GET /workspace/{workspaceId}
  • PUT /workspace/{workspaceId}

There are also some endpoints to lock and unlock a workspace (paid plans only).

  • PUT /workspace/{workspaceId}/lock
  • DELETE /workspace/{workspaceId}/lock

Authentication/authorisation

Authentication/authorisation of API calls is performed using a HMAC scheme, with the workspace API key and secret pair being used in creating the request.

HTTP headers

GET and PUT requests must include the following HTTP headers.

  • X-Authorization: The authorisation header, taking the form apiKey:base64(HMAC(apiSecret, messageDigest)) (see below).
  • Nonce: A "number once" to prevent reply attacks; for example the current UTC timestamp in milliseconds.

PUT requests must also include the following HTTP headers.

  • Content-Type: Typically a value of application/json; charset=UTF-8.
  • Content-MD5: A base64 encoded version of the MD5 hash of the workspace definition being sent to the server.

Message digest

The message digest is calculated by appending the following items together, with a newline character (\n) after every item:

  • The HTTP verb (i.e. GET or PUT).
  • The URI path (e.g. /workspace/1234).
  • The MD5 hash of the workspace definition being sent to the server (or the MD5 hash of an empty string, d41d8cd98f00b204e9800998ecf8427e, for GET requests), as a hex string.
  • The content type being sent to the server (application/json; charset=UTF-8 for PUT requests, and an empty string for GET requests).
  • The nonce (e.g. the current UTC timestamp in milliseconds; 1529225966174).

The message digest must then be hashed using the HMAC-SHA256 algorithm, and the result base64 encoded for inclusion into the X-Authorization HTTP header. The workspace API secret should be used as the key for the HMAC process. The final X-Authorization would look something like this:

  • caea989b-80a3-4db2-8e5e-7e89be284847:YTQ1NzgxZWQxZjkzYjQwNjk2MzAxNmQ5YTkyODdkZTZlNDEyYjIwZDJhMjc3OWU3MjgxM2RhODE0NzkyMDZlZg==

On receiving the request, the server will check that the workspace ID and API key combination is valid, before calculating its own version of the HMAC message digest based upon the information contained within the HTTP request. This is then compared with the version submitted in the X-Authorization header, to determine whether the API call is permitted or not.

API rate limiting

To help ensure a fair service to all users, API rate limiting is enforced for all workspace API calls (GET and PUT). See the pricing page for more details.

Workspace JSON schema

See Structurizr JSON for details of the JSON schema.