From: Rafael Sadowski <rafael@sizeofvoid.org>
Subject: relayd: check imsg_composev() / imsgbuf_flush() fail
To: tech@openbsd.org
Date: Tue, 24 Feb 2026 07:52:16 +0100

If imsg_composev() or imsgbuf_flush() fail, the message was never sent
to the CA process. Without return -1, poll() waits for the full timeout
for a response that can never come and blocks the event loop of the
relay worker.

Or what is the intention?  Comment in code:

   * Send a synchronous imsg because we cannot defer the RSA
   * operation in OpenSSL's engine layer.

Can we do better these days? As I understand it, the poll is the sync
workaround here.

Index: ca.c
===================================================================
RCS file: /cvs/src/usr.sbin/relayd/ca.c,v
diff -u -p -r1.46 ca.c
--- ca.c	24 Feb 2026 06:03:29 -0000	1.46
+++ ca.c	24 Feb 2026 06:45:53 -0000
@@ -335,10 +335,14 @@ rsae_send_imsg(int flen, const u_char *f
 	 * Send a synchronous imsg because we cannot defer the RSA
 	 * operation in OpenSSL's engine layer.
 	 */
-	if (imsg_composev(ibuf, cmd, 0, 0, -1, iov, cnt) == -1)
+	if (imsg_composev(ibuf, cmd, 0, 0, -1, iov, cnt) == -1) {
 		log_warn("%s: imsg_composev", __func__);
-	if (imsgbuf_flush(ibuf) == -1)
+		return -1;
+	}
+	if (imsgbuf_flush(ibuf) == -1) {
 		log_warn("%s: imsgbuf_flush", __func__);
+		return -1;
+	}
 
 	pfd[0].fd = ibuf->fd;
 	pfd[0].events = POLLIN;