== How to fix it in Core PHP

=== Code examples
The following code is vulnerable to SSRF as it opens a URL defined by untrusted data.

==== Noncompliant code example

[source,php,diff-id=1,diff-type=noncompliant]
----
$host = $_GET['host'];
$url = "https://$host/.well-known/openid-configuration";

$ch = curl_init($url); // Noncompliant
curl_exec($ch);
----

==== Compliant solution

[source,php,diff-id=1,diff-type=compliant]
----
$allowedHosts = ["trusted1" => "trusted1.example.com", "trusted2" => "trusted2.example.com"];
$host = $allowedHosts[$_GET['host']];
$url = "https://$host/.well-known/openid-configuration";

$ch = curl_init($url);
curl_exec($ch);
----

=== How does this work?

include::../../common/fix/pre-approved-list.adoc[]

include::../../common/fix/blacklist.adoc[]

=== Pitfalls

include::../../common/pitfalls/starts-with.adoc[]

include::../../common/pitfalls/blacklist-toctou.adoc[]