mastodon-glitch/app/javascript/entrypoints/remote_interaction_helper.ts

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/*
This script is meant to to be used in an `iframe` with the sole purpose of doing webfinger queries
client-side without being restricted by a strict `connect-src` Content-Security-Policy directive.
It communicates with the parent window through message events that are authenticated by origin,
and performs no other task.
*/
import './public-path';
import axios from 'axios';
interface JRDLink {
rel: string;
template?: string;
href?: string;
}
const isJRDLink = (link: unknown): link is JRDLink =>
typeof link === 'object' &&
link !== null &&
'rel' in link &&
typeof link.rel === 'string' &&
(!('template' in link) || typeof link.template === 'string') &&
(!('href' in link) || typeof link.href === 'string');
const findLink = (rel: string, data: unknown): JRDLink | undefined => {
if (
typeof data === 'object' &&
data !== null &&
'links' in data &&
data.links instanceof Array
) {
return data.links.find(
(link): link is JRDLink => isJRDLink(link) && link.rel === rel,
);
} else {
return undefined;
}
};
const findTemplateLink = (data: unknown) =>
findLink('http://ostatus.org/schema/1.0/subscribe', data)?.template;
const fetchInteractionURLSuccess = (
uri_or_domain: string,
template: string,
) => {
window.parent.postMessage(
{
type: 'fetchInteractionURL-success',
uri_or_domain,
template,
},
window.origin,
);
};
const fetchInteractionURLFailure = () => {
window.parent.postMessage(
{
type: 'fetchInteractionURL-failure',
},
window.origin,
);
};
const isValidDomain = (value: unknown) => {
if (typeof value !== 'string') return false;
const url = new URL('https:///path');
url.hostname = value;
return url.hostname === value;
};
// Attempt to find a remote interaction URL from a domain
const fromDomain = (domain: string) => {
const fallbackTemplate = `https://${domain}/authorize_interaction?uri={uri}`;
axios
.get(`https://${domain}/.well-known/webfinger`, {
params: { resource: `https://${domain}` },
})
.then(({ data }) => {
const template = findTemplateLink(data);
fetchInteractionURLSuccess(domain, template ?? fallbackTemplate);
return;
})
.catch(() => {
fetchInteractionURLSuccess(domain, fallbackTemplate);
});
};
// Attempt to find a remote interaction URL from an arbitrary URL
const fromURL = (url: string) => {
const domain = new URL(url).host;
const fallbackTemplate = `https://${domain}/authorize_interaction?uri={uri}`;
axios
.get(`https://${domain}/.well-known/webfinger`, {
params: { resource: url },
})
.then(({ data }) => {
const template = findTemplateLink(data);
fetchInteractionURLSuccess(url, template ?? fallbackTemplate);
return;
})
.catch(() => {
fromDomain(domain);
});
};
// Attempt to find a remote interaction URL from a `user@domain` string
const fromAcct = (acct: string) => {
acct = acct.replace(/^@/, '');
const segments = acct.split('@');
if (segments.length !== 2 || !segments[0] || !isValidDomain(segments[1])) {
fetchInteractionURLFailure();
return;
}
const domain = segments[1];
const fallbackTemplate = `https://${domain}/authorize_interaction?uri={uri}`;
if (!domain) {
fetchInteractionURLFailure();
return;
}
axios
.get(`https://${domain}/.well-known/webfinger`, {
params: { resource: `acct:${acct}` },
})
.then(({ data }) => {
const template = findTemplateLink(data);
fetchInteractionURLSuccess(acct, template ?? fallbackTemplate);
return;
})
.catch(() => {
// TODO: handle host-meta?
fromDomain(domain);
});
};
const fetchInteractionURL = (uri_or_domain: string) => {
if (uri_or_domain === '') {
fetchInteractionURLFailure();
} else if (/^https?:\/\//.test(uri_or_domain)) {
fromURL(uri_or_domain);
} else if (uri_or_domain.includes('@')) {
fromAcct(uri_or_domain);
} else {
fromDomain(uri_or_domain);
}
};
window.addEventListener('message', (event: MessageEvent<unknown>) => {
// Check message origin
if (
!window.origin ||
window.parent !== event.source ||
event.origin !== window.origin
) {
return;
}
if (
event.data &&
typeof event.data === 'object' &&
'type' in event.data &&
event.data.type === 'fetchInteractionURL' &&
'uri_or_domain' in event.data &&
typeof event.data.uri_or_domain === 'string'
) {
fetchInteractionURL(event.data.uri_or_domain);
}
});