2 files changed, 72 insertions, 0 deletions
diff --git a/src/crypto/mod.rs b/src/crypto/mod.rs
new file mode 100644
index 0000000..41e9259
--- /dev/null
+++ b/src/crypto/mod.rs
@@ -0,0 +1 @@
+pub mod signed;
diff --git a/src/crypto/signed.rs b/src/crypto/signed.rs
new file mode 100644
index 0000000..436f3d1
--- /dev/null
+++ b/src/crypto/signed.rs
@@ -0,0 +1,71 @@
+use hex;
+use hmac::{Hmac, Mac};
+use sha2::Sha256;
+use std::str;
+use std::time::{SystemTime, UNIX_EPOCH};
+
+const SEP: &str = "-";
+
+pub fn sign(key: &str, raw: &str) -> Result<String, String> {
+    let nonce = get_nonce()?;
+    let joined = format!("{nonce}{SEP}{raw}");
+    let signature = get_signature(key, &joined)?;
+    Ok(format!("{signature}{SEP}{joined}"))
+}
+
+pub fn verify(key: &str, signed: &str) -> Result<String, String> {
+    let mut iter = signed.split(SEP);
+    match (iter.next(), iter.next()) {
+        (Some(signature), Some(nonce)) => {
+            let raw = iter.collect::<Vec<&str>>().join(SEP);
+            if signature == get_signature(key, &format!("{nonce}{SEP}{raw}"))? {
+                Ok(raw)
+            } else {
+                Err("Signature does not match".to_string())
+            }
+        }
+        _ => Err("Malformed signed".to_string()),
+    }
+}
+
+fn get_signature(key: &str, message: &str) -> Result<String, String> {
+    let mut mac = Hmac::<Sha256>::new_from_slice(key.as_bytes())
+        .map_err(|e| format!("Error initializing MAC: {e}"))?;
+    mac.update(message.as_bytes());
+    let result = mac.finalize();
+    Ok(hex::encode(result.into_bytes()))
+}
+
+fn get_nonce() -> Result<String, String> {
+    Ok(SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map_err(|e| format!("Failure getting unix expoch: {e}"))?
+        .as_millis()
+        .to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn sign_and_validate() {
+        let key = "xagrlBUobnTj32Rm8tvmsZ6mh8qLfip5".to_string();
+        assert_eq!(verify(&key, &sign(&key, "").unwrap()), Ok("".to_string()));
+        assert_eq!(
+            verify(&key, &sign(&key, "hello").unwrap()),
+            Ok("hello".to_string())
+        );
+        assert_eq!(
+            verify(&key, &sign(&key, "with-sep").unwrap()),
+            Ok("with-sep".to_string())
+        );
+    }
+
+    #[test]
+    fn fail_when_key_mismatch() {
+        let key1 = "xagrlBUobnTj32Rm8tvmsZ6mh8qLfip5".to_string();
+        let key2 = "8KJBK6axEr9wQ390GgdWA8Pjn8FwILDa".to_string();
+        assert!(verify(&key1, &sign(&key2, "hello").unwrap()).is_err());
+    }
+}