From 0b3161aeea388a092fd5a128191d64e7fd2fd941 Mon Sep 17 00:00:00 2001
From: Matthew Holt <mholt@users.noreply.github.com>
Date: Tue, 13 Sep 2022 17:21:04 -0600
Subject: [PATCH] cmd: Customizable user agent (close #2795)

---
 cmd/main.go | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/cmd/main.go b/cmd/main.go
index b91559ce8..17da8bd07 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -41,10 +41,15 @@ func init() {
 	// set a fitting User-Agent for ACME requests
 	version, _ := caddy.Version()
 	cleanModVersion := strings.TrimPrefix(version, "v")
-	certmagic.UserAgent = "Caddy/" + cleanModVersion
+	ua := "Caddy/" + cleanModVersion
+	if uaEnv, ok := os.LookupEnv("USERAGENT"); ok {
+		ua = uaEnv + " " + ua
+	}
+	certmagic.UserAgent = ua
 
 	// by using Caddy, user indicates agreement to CA terms
-	// (very important, or ACME account creation will fail!)
+	// (very important, as Caddy is often non-interactive
+	// and thus ACME account creation will fail!)
 	certmagic.DefaultACME.Agreed = true
 }