keylime: Introduce the registrar_client module

The registrar_client module implements the builder pattern to allow
setting the optional parameters as needed.

This also implements the mechanism to allow the agent to communicate
with the registrar that support different API versions:

- The client will make a GET request to the '/version' endpoint of the
  registrar.  If the request is successful, the client will use the
  provided API version if it is enabled.
- If the registrar does not support the '/version' endpoint, the client
  will try to register using each of the enabled API versions, starting
  from the latest. If none of the enabled versions is supported by the
  registrar, the registration fails.

This is part of the implementation of the enhancement proposal 114:
keylime/enhancements#115

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>

keylime-agent/src/api.rs

@@ -3,18 +3,13 @@ use crate::{
     notifications_handler, quotes_handler, QuoteData,
 };
 use actix_web::{http, web, HttpRequest, HttpResponse, Responder, Scope};
-use keylime::list_parser::parse_list;
+use keylime::{list_parser::parse_list, version::KeylimeVersion};
 use log::*;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 
 pub static SUPPORTED_API_VERSIONS: &[&str] = &["2.1", "2.2"];
 
-#[derive(Serialize, Deserialize, Debug)]
-struct KeylimeVersion {
-    supported_version: String,
-}
-
 #[derive(Error, Debug, PartialEq)]
 pub enum APIError {
     #[error("API version \"{0}\" not supported")]

keylime/Cargo.toml

@@ -14,6 +14,7 @@ log.workspace = true
 openssl.workspace = true
 pest.workspace = true
 pest_derive.workspace = true
+reqwest.workspace = true
 serde.workspace = true
 serde_derive.workspace = true
 serde_json.workspace = true
@@ -23,11 +24,17 @@ tss-esapi.workspace = true
 picky-asn1-der.workspace = true
 picky-asn1-x509.workspace = true
 tokio.workspace = true
+# wiremock was moved to be a regular dependency because optional
+# dev-dependencies are not supported
+# see: https://github.com/rust-lang/cargo/issues/1596
+wiremock = {version = "0.6", optional = true}
 
 [dev-dependencies]
 tempfile.workspace = true
+actix-rt.workspace = true
 
 [features]
 # This feature enables tests that require a TPM and the TCTI environment
 # variable properly configured
-testing = []
+# This should change to dev-dependencies when we have integration testing
+testing = ["wiremock"]

keylime/src/lib.rs

@@ -5,8 +5,10 @@ pub mod hostname_parser;
 pub mod ima;
 pub mod ip_parser;
 pub mod list_parser;
+pub mod registrar_client;
 pub mod serialization;
 pub mod tpm;
+pub mod version;
 
 #[macro_use]
 extern crate static_assertions;