[pbs-devel] [PATCH proxmox-backup 3/3] config/tfa: webauthn: disallow registering a token twice

[Dominik Csapak <d.csapak@proxmox.com>]

by adding the existing credential id to the 'excludeCredentials' list

this prevents the browser from registering a token twice, which
lets authentication fail on some browser/token combinations
(e.g. onlykey+chromium)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/config/tfa.rs         | 15 +++++++++++++--
 www/window/AddWebauthn.js |  7 +++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/config/tfa.rs b/src/config/tfa.rs
index 29e0fb48..7c656d20 100644
--- a/src/config/tfa.rs
+++ b/src/config/tfa.rs
@@ -803,9 +803,20 @@ impl TfaUserData {
         userid: &Userid,
         description: String,
     ) -> Result<String, Error> {
+        let cred_ids: Vec<_> = self
+            .enabled_webauthn_entries()
+            .map(|cred| cred.cred_id.clone())
+            .collect();
+
         let userid_str = userid.to_string();
-        let (challenge, state) = webauthn
-            .generate_challenge_register(&userid_str, Some(UserVerificationPolicy::Discouraged))?;
+        let (challenge, state) = webauthn.generate_challenge_register_options(
+            userid_str.as_bytes().to_vec(),
+            userid_str.clone(),
+            userid_str.clone(),
+            Some(cred_ids),
+            Some(UserVerificationPolicy::Discouraged),
+        )?;
+
         let challenge_string = challenge.public_key.challenge.to_string();
         let challenge = serde_json::to_string(&challenge)?;
 
diff --git a/www/window/AddWebauthn.js b/www/window/AddWebauthn.js
index 16731a63..a3888206 100644
--- a/www/window/AddWebauthn.js
+++ b/www/window/AddWebauthn.js
@@ -82,6 +82,13 @@ Ext.define('PBS.window.AddWebauthn', {
 		challenge_obj.publicKey.user.id =
 		    PBS.Utils.base64url_to_bytes(challenge_obj.publicKey.user.id);
 
+		// convert existing authenticators structure
+		challenge_obj.publicKey.excludeCredentials =
+		    (challenge_obj.publicKey.excludeCredentials || []).map((cred) => ({
+			id: PBS.Utils.base64url_to_bytes(cred.id),
+			type: cred.type,
+		    }));
+
 		let msg = Ext.Msg.show({
 		    title: `Webauthn: ${gettext('Setup')}`,
 		    message: gettext('Please press the button on your Webauthn Device'),
-- 
2.20.1