sync: allow sync for non-superusers

by requiring
- Datastore.Backup permission for target datastore
- Remote.Read permission for source remote/datastore
- Datastore.Prune if vanished snapshots should be removed
- Datastore.Modify if another user should own the freshly synced
snapshots

reading a sync job entry only requires knowing about both the source
remote and the target datastore.

note that this does not affect the Authid used to authenticate with the
remote, which of course also needs permissions to access the source
datastore.

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

src/api2/config/remote.rs

@@ -6,6 +6,7 @@ use proxmox::api::{api, ApiMethod, Router, RpcEnvironment, Permission};
 use proxmox::tools::fs::open_file_locked;
 
 use crate::api2::types::*;
+use crate::config::cached_user_info::CachedUserInfo;
 use crate::config::remote;
 use crate::config::acl::{PRIV_REMOTE_AUDIT, PRIV_REMOTE_MODIFY};
 
@@ -22,7 +23,8 @@ use crate::config::acl::{PRIV_REMOTE_AUDIT, PRIV_REMOTE_MODIFY};
         },
     },
     access: {
-        permission: &Permission::Privilege(&["remote"], PRIV_REMOTE_AUDIT, false),
+        description: "List configured remotes filtered by Remote.Audit privileges",
+        permission: &Permission::Anybody,
     },
 )]
 /// List all remotes
@@ -31,16 +33,25 @@ pub fn list_remotes(
     _info: &ApiMethod,
     mut rpcenv: &mut dyn RpcEnvironment,
 ) -> Result<Vec<remote::Remote>, Error> {
+    let auth_id: Authid = rpcenv.get_auth_id().unwrap().parse()?;
+    let user_info = CachedUserInfo::new()?;
 
     let (config, digest) = remote::config()?;
 
     let mut list: Vec<remote::Remote> = config.convert_to_typed_array("remote")?;
-
     // don't return password in api
     for remote in &mut list {
         remote.password = "".to_string();
     }
 
+    let list = list
+        .into_iter()
+        .filter(|remote| {
+            let privs = user_info.lookup_privs(&auth_id, &["remote", &remote.name]);
+            privs & PRIV_REMOTE_AUDIT != 0
+        })
+        .collect();
+
     rpcenv["digest"] = proxmox::tools::digest_to_hex(&digest).into();
     Ok(list)
 }