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/*
GoToSocial
Copyright (C) 2021-2023 GoToSocial Authors admin@gotosocial.org
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package transport
import (
"context"
"encoding/xml"
"fmt"
"io"
"net/http"
"net/url"
apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
)
// webfingerURLFor returns the URL to try a webfinger request against, as
// well as if the URL was retrieved from cache. When the URL is retrieved
// from cache we don't have to try and do host-meta discovery
func (t *transport) webfingerURLFor(targetDomain string) (string, bool) {
url := "https://" + targetDomain + "/.well-known/webfinger"
wc := t.controller.state.Caches.GTS.Webfinger()
// We're doing the manual locking/unlocking here to be able to
// safely call Cache.Get instead of Get, as the latter updates the
// item expiry which we don't want to do here
wc.Lock()
item, ok := wc.Cache.Get(targetDomain)
wc.Unlock()
if ok {
url = item.Value
}
return url, ok
}
func prepWebfingerReq(ctx context.Context, loc, domain, username string) (*http.Request, error) {
req, err := http.NewRequestWithContext(ctx, http.MethodGet, loc, nil)
if err != nil {
return nil, err
}
value := url.QueryEscape("acct:" + username + "@" + domain)
req.URL.RawQuery = "resource=" + value
req.Header.Add("Accept", string(apiutil.AppJSON))
req.Header.Add("Accept", "application/jrd+json")
req.Header.Set("Host", req.URL.Host)
return req, nil
}
func (t *transport) Finger(ctx context.Context, targetUsername string, targetDomain string) ([]byte, error) {
// Generate new GET request
url, cached := t.webfingerURLFor(targetDomain)
req, err := prepWebfingerReq(ctx, url, targetDomain, targetUsername)
if err != nil {
return nil, err
}
// Perform the HTTP request
rsp, err := t.GET(req)
if err != nil {
return nil, err
}
defer rsp.Body.Close()
// Check if the request succeeded so we can bail out early or if we explicitly
// got a "this resource is gone" response which will happen when a user has
// deleted the account
if rsp.StatusCode == http.StatusOK || rsp.StatusCode == http.StatusGone {
if cached {
// If we got a response we consider successful on a cached URL, i.e one set
// by us later on when a host-meta based webfinger request succeeded, set it
// again here to renew the TTL
t.controller.state.Caches.GTS.Webfinger().Set(targetDomain, url)
}
if rsp.StatusCode == http.StatusGone {
return nil, fmt.Errorf("account has been deleted/is gone")
}
return io.ReadAll(rsp.Body)
}
// From here on out, we're handling different failure scenarios and
// deciding whether we should do a host-meta based fallback or not
if (rsp.StatusCode >= 500 && rsp.StatusCode < 600) || cached {
// In case we got a 5xx, bail out irrespective of if the value
// was cached or not. The target may be broken or be signalling
// us to back-off.
//
// If it's any error but the URL was cached, bail out too
return nil, fmt.Errorf("GET request to %s failed: %s", req.URL.String(), rsp.Status)
}
// So far we've failed to get a successful response from the expected
// webfinger endpoint. Lets try and discover the webfinger endpoint
// through /.well-known/host-meta
host, err := t.webfingerFromHostMeta(ctx, targetDomain)
if err != nil {
return nil, fmt.Errorf("failed to discover webfinger URL fallback for: %s through host-meta: %w", targetDomain, err)
}
// Check if the original and host-meta URL are the same. If they
// are there's no sense in us trying the request again as it just
// failed
if host == url {
return nil, fmt.Errorf("webfinger discovery on %s returned endpoint we already tried: %s", targetDomain, host)
}
// Now that we have a different URL for the webfinger
// endpoint, try the request against that endpoint instead
req, err = prepWebfingerReq(ctx, host, targetDomain, targetUsername)
if err != nil {
return nil, err
}
// Perform the HTTP request
rsp, err = t.GET(req)
if err != nil {
return nil, err
}
defer rsp.Body.Close()
if rsp.StatusCode != http.StatusOK {
// A HTTP 410 indicates we got a response to our webfinger query, but the resource
// we asked for is gone. This means the endpoint itself is valid and we should
// cache it for future queries to the same domain
if rsp.StatusCode == http.StatusGone {
t.controller.state.Caches.GTS.Webfinger().Set(targetDomain, host)
return nil, fmt.Errorf("account has been deleted/is gone")
}
// We've reached the end of the line here, both the original request
// and our attempt to resolve it through the fallback have failed
return nil, fmt.Errorf("GET request to %s failed: %s", req.URL.String(), rsp.Status)
}
// Set the URL in cache here, since host-meta told us this should be the
// valid one, it's different from the default and our request to it did
// not fail in any manner
t.controller.state.Caches.GTS.Webfinger().Set(targetDomain, host)
return io.ReadAll(rsp.Body)
}
func (t *transport) webfingerFromHostMeta(ctx context.Context, targetDomain string) (string, error) {
// Build the request for the host-meta endpoint
hmurl := "https://" + targetDomain + "/.well-known/host-meta"
req, err := http.NewRequestWithContext(ctx, http.MethodGet, hmurl, nil)
if err != nil {
return "", err
}
// We're doing XML
req.Header.Add("Accept", string(apiutil.AppXML))
req.Header.Add("Accept", "application/xrd+xml")
req.Header.Set("Host", req.URL.Host)
// Perform the HTTP request
rsp, err := t.GET(req)
if err != nil {
return "", err
}
defer rsp.Body.Close()
// Doesn't look like host-meta is working for this instance
if rsp.StatusCode != http.StatusOK {
return "", fmt.Errorf("GET request for %s failed: %s", req.URL.String(), rsp.Status)
}
e := xml.NewDecoder(rsp.Body)
var hm apimodel.HostMeta
if err := e.Decode(&hm); err != nil {
// We got something, but it's not a host-meta document we understand
return "", fmt.Errorf("failed to decode host-meta response for %s at %s: %w", targetDomain, req.URL.String(), err)
}
for _, link := range hm.Link {
// Based on what we currently understand, there should not be more than one
// of these with Rel="lrdd" in a host-meta document
if link.Rel == "lrdd" {
u, err := url.Parse(link.Template)
if err != nil {
return "", fmt.Errorf("lrdd link is not a valid url: %w", err)
}
// Get rid of the query template, we only want the scheme://host/path part
u.RawQuery = ""
urlStr := u.String()
return urlStr, nil
}
}
return "", fmt.Errorf("no webfinger URL found")
}
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