Add 'paddle' crate

Should verify a Paddle webhook. This ensures that the request really
does come from Paddle.

In order to verify the request, we need to sign the serialized POST
parameters. And, weirdly, Paddle requires you to serialize parameters in
PHP's serialization format.

Using this Gist by 'drewmccormack' as a reference for the format:
https://gist.github.com/drewmccormack/a51b18ffeda8f596a11a8623481344d8

1 files changed, 40 insertions, 0 deletions

diff --git a/license-generator/paddle/src/lib.rs b/license-generator/paddle/src/lib.rs
new file mode 100644
index 0000000..a1db417
--- /dev/null
+++ b/license-generator/paddle/src/lib.rs
@@ -0,0 +1,40 @@
+// https://paddle.com/docs/reference-verifying-webhooks/
+fn verify_signature<'a, I>(params: I) -> bool
+where I: ExactSizeIterator<Item = (&'a str, &'a str)> {
+    false
+}
+
+fn php_serialize<'a, I>(pairs: I) -> String
+where I: ExactSizeIterator<Item = (&'a str, &'a str)> {
+    let mut serialized = String::with_capacity(500);
+
+    serialized.push_str(
+        &format!("a:{pairs_count}:{{", pairs_count = pairs.len())
+    );
+
+    for (key, value) in pairs {
+        serialized.push_str(
+            &format!(
+                "s:{key_length}:\"{key}\";s:{value_length}:\"{value}\";",
+                key_length = key.len(),
+                key = key,
+                value_length = value.len(),
+                value = value
+            )
+        );
+    }
+
+    serialized.push_str("}");
+
+    serialized
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn php_serialize_serializes_key_values_as_php_string() {
+    }
+}