[PATCH proxmox v4 2/8] http: tls: use legacy behavior when PROXMOX_OLD_TLS_CHECK is set to "1"

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

If that environment variable is set to "1", give the openssl result
priority, and potentially ignore a given fingerprint that is not
matching. If that's the case, print a warning.

Co-developed-by: Shannon Sterz <s.sterz@proxmox.com>
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 proxmox-http/src/tls.rs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/proxmox-http/src/tls.rs b/proxmox-http/src/tls.rs
index 5c2b1743..abdf51e9 100644
--- a/proxmox-http/src/tls.rs
+++ b/proxmox-http/src/tls.rs
@@ -103,6 +103,8 @@ impl std::str::FromStr for Fingerprint {
     }
 }
 
+pub const PROXMOX_OLD_TLS_CHECK_VAR: &str = "PROXMOX_OLD_TLS_CHECK";
+
 ///
 /// Error type returned by failed [`openssl_verify_callback`].
 ///
@@ -159,15 +161,24 @@ impl PartialEq for SslVerifyError {
 
 /// Intended as an openssl verification callback.
 ///
-/// The following things are checked:
+/// If the 'PROXMOX_OLD_TLS_CHECK' environment variable is not set to "1",
+/// the following things are checked:
 ///
 /// * If no fingerprint is given, return the openssl verification result
-/// * If a fingerprint is given get the leaf fp and check that against the given
+/// * If a fingerprint is given, check it against the leaf fp
+///
+/// Otherwise, we trust the openssl result if the whole chain was trusted
 pub fn openssl_verify_callback(
     openssl_valid: bool,
     ctx: &mut X509StoreContextRef,
     expected_fp: Option<Fingerprint>,
 ) -> Result<(), SslVerifyError> {
+    let old_check = matches!(std::env::var(PROXMOX_OLD_TLS_CHECK_VAR).as_deref(), Ok("1"));
+
+    if old_check && openssl_valid {
+        return Ok(());
+    }
+
     match expected_fp {
         Some(expected_fp) => {
             let fingerprint = get_leaf_fp(ctx)?;
-- 
2.47.3