Add helper methods to make it more convenient to reuse a URL

Fixes #7

src/jose.rs

@@ -1,4 +1,5 @@
 use std::fmt;
+use std::time::Duration;
 
 use base64ct::{Base64Url, Base64UrlUnpadded, Encoding};
 use elliptic_curve::sec1::{EncodedPoint, FromEncodedPoint, ModulusSize, ToEncodedPoint};
@@ -16,7 +17,7 @@ use zeroize::Zeroize;
 
 use crate::key_exchange::{create_enc_key, recover_enc_key};
 use crate::util::{b64_to_bytes, b64_to_str};
-use crate::{EncryptionKey, Error, Result};
+use crate::{EncryptionKey, Error, Result, TangClient};
 
 /// Representation of a tang advertisment response which is a JWS of available keys.
 ///
@@ -486,7 +487,6 @@ struct TangParams {
 
 impl KeyMeta {
     /// Serialize this data to a JSON string
-    #[must_use]
     pub fn to_json(&self) -> String {
         serde_json::to_string(self).expect("serialization failure")
     }
@@ -496,6 +496,16 @@ impl KeyMeta {
         serde_json::from_str(val).map_err(Into::into)
     }
 
+    /// Create a [`TangClient`] from the URL used to generate this key
+    pub fn client(&self, timeout: Option<Duration>) -> TangClient {
+        TangClient::new(&self.clevis.tang.url, timeout)
+    }
+
+    /// The URL that was used to generate this key
+    pub fn url(&self) -> &str {
+        &self.clevis.tang.url
+    }
+
     pub(crate) fn recover_key<const N: usize>(
         &self,
         server_key_exchange: impl FnOnce(&str, &Jwk) -> Result<Jwk>,

src/lib.rs

@@ -4,20 +4,20 @@
 //! This is still under development, but works reasonibly well.
 //!
 //! ```
-//! # #[cfg(not(feature = "_backend"))] fn main() {}
-//! # #[cfg(feature = "_backend")]
 //! # fn main() {
+//! # #[cfg(feature = "_backend")] test();
+//! # }
+//! #
+//! # fn test() {
 //! use clevis::{KeyMeta, TangClient};
 //!
-//! /// 32-byte (256 bit) key
+//! /// 32-byte (256 bit) key, such as for AES256-GCM
 //! const KEY_BYTES: usize = 32;
 //!
 //! /* key provisioning */
 //!
-//! let client = TangClient::new("localhost:11697", None);
-//!
 //! // create a key suitible for encryption (i.e. has gone through a KDF)
-//! let out = client
+//! let out = TangClient::new("localhost:11697", None)
 //!     .create_secure_key::<KEY_BYTES>()
 //!     .expect("failed to generate key");
 //!
@@ -33,7 +33,8 @@
 //! /* key recovery */
 //!
 //! let new_meta = KeyMeta::from_json(&meta_str).expect("invalid metadata");
-//! let new_key = client
+//! let new_key = new_meta
+//!     .client(None)
 //!     .recover_secure_key::<KEY_BYTES>(&new_meta)
 //!     .expect("failed to retrieve key");
 //!
@@ -44,6 +45,7 @@
 #![warn(clippy::pedantic)]
 #![allow(clippy::missing_panics_doc)]
 #![allow(clippy::missing_errors_doc)]
+#![allow(clippy::must_use_candidate)]
 
 mod error;
 mod jose;

src/tang_interface.rs

@@ -6,7 +6,9 @@ use crate::{EncryptionKey, Result};
 // const DEFAULT_URL: &str = "http://tang.local";
 const DEFAULT_TIMEOUT: Duration = Duration::from_secs(120);
 
-/// A tang server connection specification
+/// A tang server connection specification.
+///
+/// This does not hold an active connection, only connection parameters.
 #[derive(Clone, Debug)]
 pub struct TangClient {
     url: String,
@@ -28,6 +30,11 @@ impl TangClient {
         }
     }
 
+    /// This client's connection URL
+    pub fn url(&self) -> &str {
+        &self.url
+    }
+
     /// Locate derive keys from the server and provision an encryption key with specified lengh.
     pub fn create_secure_key<const KEYBYTES: usize>(&self) -> Result<ProvisionedData<KEYBYTES>> {
         let (keys, signing_thp) = self.fetch_keys(None)?;