From 8c47a16b2878de0525bbe564a30779ece40694f1 Mon Sep 17 00:00:00 2001
From: Jason Bowman <jason@json64.dev>
Date: Thu, 13 Aug 2026 18:09:31 -0700
Subject: [PATCH] feat: proxy SSH certificates via ssh-agent-lib 0.6
 PublicCredential (fix #56)

ssh-agent-lib 0.5.1 typed identities as ssh_key::public::KeyData, which cannot
represent an OpenSSH certificate: request_identities decoded a
...-cert-v01@openssh.com blob into a lossy opaque key and re-serialized a
truncated identity, so any upstream agent holding a certificate made
`ssh-add -l` fail with "incomplete message" and (with #94) silently dropped
every other agent's keys.

Bump to ssh-agent-lib 0.6.0, whose PublicCredential (Key | Cert) round-trips
certificates losslessly in both identity listings and sign requests. Key the
known-keys map by credential.key_data() so a certificate, its bare public key,
and the sign request ssh issues all resolve to the same upstream agent.

Note: certificates with valid_before = u64::MAX ("Valid: forever") still fail
to decode under the ssh-key 0.6.7 that ssh-agent-lib 0.6.0 builds on
(RustCrypto/SSH#504, fixed in ssh-key 0.7). Certificates with a real
expiration -- as OpenSSH and correctly configured issuers produce -- work now.
---
 Cargo.lock | 10 +++++-----
 Cargo.toml |  2 +-
 src/lib.rs | 16 +++++++++++++---
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 08f4f82..8ccf8df 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1296,9 +1296,9 @@ dependencies = [
 
 [[package]]
 name = "secrecy"
-version = "0.8.0"
+version = "0.10.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9bd1c54ea06cfd2f6b63219704de0b9b4f72dcc2b8fdef820be6cd799780e91e"
+checksum = "e891af845473308773346dc847b2c23ee78fe442e0472ac50e22a18a93d3ae5a"
 dependencies = [
  "zeroize",
 ]
@@ -1499,9 +1499,9 @@ dependencies = [
 
 [[package]]
 name = "ssh-agent-lib"
-version = "0.5.1"
+version = "0.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "faf67cca8055cc41de60ac7344a98b9c8f9e2a9ee9b1adf3e142b78ec1e7abba"
+checksum = "b528981371b3bfdfe927a5ef37221446e0ba44551e673b569fd0fd38e5dcb292"
 dependencies = [
  "async-trait",
  "byteorder",
@@ -1513,7 +1513,7 @@ dependencies = [
  "ssh-encoding",
  "ssh-key",
  "subtle",
- "thiserror 1.0.69",
+ "thiserror 2.0.12",
  "tokio",
  "tokio-util",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index d1cde64..6bcc358 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@ rust-version = "1.83.0"
 [dependencies]
 clap-serde-derive = "0.2.1"
 flexi_logger = "0.31.7"
-ssh-agent-lib = "0.5.1"
+ssh-agent-lib = "0.6.0"
 toml = "0.9.8"
 
 [dependencies.shellexpand]
diff --git a/src/lib.rs b/src/lib.rs
index 0976790..cc40147 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -31,10 +31,16 @@ impl Session for MuxAgent {
     }
 
     async fn sign(&mut self, request: SignRequest) -> Result<Signature, AgentError> {
-        let fingerprint = request.pubkey.fingerprint(Default::default());
+        let fingerprint = request
+            .credential
+            .key_data()
+            .fingerprint(Default::default());
         log::trace!("incoming: sign({})", &fingerprint);
 
-        if let Some(agent_sock_path) = self.get_agent_sock_for_pubkey(&request.pubkey).await? {
+        if let Some(agent_sock_path) = self
+            .get_agent_sock_for_pubkey(request.credential.key_data())
+            .await?
+        {
             log::info!(
                 "Requesting signature with key {} from upstream agent <{}>",
                 &fingerprint,
@@ -215,7 +221,11 @@ impl MuxAgent {
             };
             {
                 for id in &agent_identities {
-                    known_keys.insert(id.pubkey.clone(), sock_path.clone());
+                    // Key the map by the underlying public key. For an OpenSSH
+                    // certificate this is the cert's public key, which also matches
+                    // the plain-key sign request that ssh issues, so both resolve to
+                    // the same upstream agent.
+                    known_keys.insert(id.credential.key_data().clone(), sock_path.clone());
                 }
             }
             log::trace!(