cdh/kms: cckbc use AA to get evidence rather than token

When we use one AA and multiple CDH to connect to different KBS in one
confidential VM, AATokenProvider will strict the KBS be the same. If we
use AAEvidenceProvider, the target KBS address can be specified in CDH's
config and share a same AA.

This will also make the workflow simpler. Before this commit, if we want
to get a confidential resource from KBS, AA should connect to a KBS to
get a token. Then CDH get the token from AA. Then CDH access the KBS.

After this commit, only CDH will access the KBS.

Signed-off-by: Xynnn007 <[email protected]>

confidential-data-hub/hub/src/kms/plugins/kbs/cc_kbc.rs

@@ -8,7 +8,7 @@ use std::env;
 use async_trait::async_trait;
 use kbs_protocol::{
     client::KbsClient as KbsProtocolClient,
-    token_provider::{AATokenProvider, TokenProvider},
+    evidence_provider::{AAEvidenceProvider, EvidenceProvider},
     KbsClientCapabilities, ResourceUri,
 };
 use log::{info, warn};
@@ -18,16 +18,16 @@ use super::{Error, Result};
 use super::Kbc;
 
 pub struct CcKbc {
-    client: KbsProtocolClient<Box<dyn TokenProvider>>,
+    client: KbsProtocolClient<Box<dyn EvidenceProvider>>,
 }
 
 impl CcKbc {
     pub async fn new(kbs_host_url: &str) -> Result<Self> {
-        let token_provider = AATokenProvider::new().await.map_err(|e| {
-            Error::KbsClientError(format!("create AA token provider failed: {e:?}"))
+        let evidence_provider = AAEvidenceProvider::new().await.map_err(|e| {
+            Error::KbsClientError(format!("create AA evidence provider failed: {e:?}"))
         })?;
-        let client = kbs_protocol::KbsClientBuilder::with_token_provider(
-            Box::new(token_provider),
+        let client = kbs_protocol::KbsClientBuilder::with_evidence_provider(
+            Box::new(evidence_provider),
             kbs_host_url,
         );