Module csp 

CSP — Declarative Content Security Policy for widgets

This module owns the config types and the merge function that together decide which domains appear in a widget’s CSP when mcpr rewrites an MCP response.

Model

A widget’s CSP has three independent directive arrays:

• connectDomains — allowed targets for fetch, WebSocket, EventSource.
• resourceDomains — allowed sources for scripts, styles, images, fonts, media.
• frameDomains — allowed sources for nested <iframe> content.

Each directive carries its own DirectivePolicy — a list of domains and a Mode (extend or replace) that decides how to combine declared domains with whatever the upstream MCP server already returned.

A top-level CspConfig holds one policy per directive plus an optional list of WidgetScoped entries. Widget entries match resource URIs with glob patterns (e.g. ui://widget/payment*) and layer on top of the global policy.

Merge

effective_domains computes the final domain list for one directive, given upstream domains, a resource URI, and the config. The rules are:

1. If the global directive’s mode is replace, discard upstream entirely; otherwise start from upstream minus localhost and the upstream host itself.
2. Append the global directive’s declared domains.
3. For each widget entry whose match glob matches the resource URI, in config order, either extend (append) or replace (overwrite) the working list with the widget’s domains for this directive.
4. Prepend the proxy URL and dedupe.

Replace semantics are scoped: a global replace only ignores upstream; a widget replace wipes everything accumulated above it.

Example

[csp.connectDomains]
domains = ["api.example.com"]
mode    = "extend"

[csp.resourceDomains]
domains = ["cdn.example.com"]
mode    = "extend"

[csp.frameDomains]
domains = []
mode    = "replace"

[[csp.widget]]
match              = "ui://widget/payment*"
connectDomains     = ["api.stripe.com"]
connectDomainsMode = "extend"

Structs

CspConfig

Complete CSP configuration: three global directives plus widget overrides.

DirectivePolicy

A domain list paired with a merge mode.

WidgetScoped

Per-widget override matched by glob on resource URI.

Enums

Directive

Which of the three CSP directive arrays a policy targets.

Mode

Merge mode for a single CSP directive.

Functions

effective_domains

Compute the effective domain list for one directive.

glob_match

Minimal glob matcher over bytes. Supports * (any sequence) and ? (single character). Everything else matches literally.