[pbs-devel] [PATCH proxmox-backup] proxy: check permissions on proxy.key and proxy.pem files

[Gabriel Goller <g.goller@proxmox.com>]

Check the owner and permission of the proxy.key and proxy.pem files.
This avoids openssl's unhelpful error message and prints a nicer one.

Motivation: https://forum.proxmox.com/threads/proxmox-backup-tailscale-proxmox-backup-proxy-service-wont-boot.153204

Signed-off-by: Gabriel Goller <g.goller@proxmox.com>
---

Note: not sure about the correct permissions, we currently default to
640, but maybe a minimum of 400 is enough?

 src/bin/proxmox-backup-proxy.rs | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/bin/proxmox-backup-proxy.rs b/src/bin/proxmox-backup-proxy.rs
index 041f3aff999c..544196b8bc5d 100644
--- a/src/bin/proxmox-backup-proxy.rs
+++ b/src/bin/proxmox-backup-proxy.rs
@@ -367,6 +367,30 @@ async fn run() -> Result<(), Error> {
     Ok(())
 }
 
+/// Check permissions and owner of passed path.
+fn check_permissions<T: AsRef<Path>>(path: T, file_mode: u32) -> Result<(), Error> {
+    match nix::sys::stat::stat(path.as_ref()) {
+        Ok(stat) => {
+            if stat.st_uid != u32::from(pbs_config::backup_user()?.uid)
+                || stat.st_gid != u32::from(pbs_config::backup_group()?.gid)
+                || stat.st_mode & 0o770 < file_mode
+            {
+                bail!(
+                        "file {:?} has wrong permissions - check if it's owned by {}:{} and has {} permissions",
+                        path.as_ref(),
+                        pbs_config::backup_user()?.uid,
+                        pbs_config::backup_group()?.gid,
+                        file_mode
+                    );
+            }
+        }
+        Err(err) => {
+            bail!("unable to open file {:?} - {err}", path.as_ref(),);
+        }
+    }
+    Ok(())
+}
+
 fn make_tls_acceptor() -> Result<SslAcceptor, Error> {
     let key_path = configdir!("/proxy.key");
     let cert_path = configdir!("/proxy.pem");
@@ -375,6 +399,9 @@ fn make_tls_acceptor() -> Result<SslAcceptor, Error> {
     let ciphers_tls_1_3 = config.ciphers_tls_1_3;
     let ciphers_tls_1_2 = config.ciphers_tls_1_2;
 
+    check_permissions(key_path, 0o640)?;
+    check_permissions(cert_path, 0o640)?;
+
     let mut acceptor = proxmox_rest_server::connection::TlsAcceptorBuilder::new()
         .certificate_paths_pem(key_path, cert_path);
 
-- 
2.39.2



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