[bugfix] Update `GetURL` to extract url from Link objects with href (#4249)

# Description

> If this is a code change, please include a summary of what you've coded, and link to the issue(s) it closes/implements.
>
> If this is a documentation change, please briefly describe what you've changed and why.

This pull request updates our parsing of the `url` property in incoming ActivityPub items to also include Link items, and not just bare URIs.

The first discovered url is still used as the *gtsmodel.Account or *gtsmodel.Status `url` property, so this change only really affects our dereference URL anti-spoof check thingy.

~~Should fix https://codeberg.org/superseriousbusiness/gotosocial/issues/4248 but I need to run it and test it myself first to be sure.~~

Fixes https://codeberg.org/superseriousbusiness/gotosocial/issues/4248

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [x] I/we have commented the added code, particularly in hard-to-understand areas.
- [ ] I/we have made any necessary changes to documentation.
- [x] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4249
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

1 files changed, 24 insertions, 1 deletions

diff --git a/internal/ap/properties.go b/internal/ap/properties.go
index b5154c0aa..722c3fca5 100644
--- a/internal/ap/properties.go
+++ b/internal/ap/properties.go
@@ -135,7 +135,8 @@ func AppendBcc(with WithBcc, bcc ...*url.URL) {
 	}, bcc...)
 }
 
-// GetURL returns the IRIs contained in the URL property of 'with'.
+// GetURL returns IRIs contained
+// in the URL property of 'with'.
 func GetURL(with WithURL) []*url.URL {
 	urlProp := with.GetActivityStreamsUrl()
 	if urlProp == nil || urlProp.Len() == 0 {
@@ -144,9 +145,31 @@ func GetURL(with WithURL) []*url.URL {
 	urls := make([]*url.URL, 0, urlProp.Len())
 	for i := 0; i < urlProp.Len(); i++ {
 		at := urlProp.At(i)
+
+		// See if it's a plain URI.
 		if at.IsXMLSchemaAnyURI() {
 			u := at.GetXMLSchemaAnyURI()
 			urls = append(urls, u)
+			continue
+		}
+
+		// See if it's a Link obj
+		// with an href property.
+		if at.IsActivityStreamsLink() {
+			l := at.GetActivityStreamsLink()
+			hr := l.GetActivityStreamsHref()
+			if hr == nil {
+				// No href.
+				continue
+			}
+
+			if hr.IsXMLSchemaAnyURI() {
+				u := hr.Get()
+				urls = append(urls, u)
+			} else if hr.IsIRI() {
+				u := hr.GetIRI()
+				urls = append(urls, u)
+			}
 		}
 	}
 	return urls