Index: src/github.com/cloudflare/cfssl/cmd/cfssljson/cfssljson.go
--- src/github.com/cloudflare/cfssl/cmd/cfssljson/cfssljson.go.orig	2018-02-03 08:55:25.000000000 +0100
+++ src/github.com/cloudflare/cfssl/cmd/cfssljson/cfssljson.go	2018-02-03 09:02:46.958949000 +0100
@@ -112,7 +112,7 @@
 	}
 	if cert != "" {
 		outs = append(outs, outputFile{
-			Filename: baseName + ".pem",
+			Filename: baseName + ".crt",
 			Contents: cert,
 			Perms:    0664,
 		})
@@ -125,7 +125,7 @@
 	}
 	if key != "" {
 		outs = append(outs, outputFile{
-			Filename: baseName + "-key.pem",
+			Filename: baseName + ".key",
 			Contents: key,
 			Perms:    0600,
 		})
@@ -171,12 +171,12 @@
 				os.Exit(1)
 			}
 			outs = append(outs, outputFile{
-				Filename: baseName + "-bundle.pem",
+				Filename: baseName + "-bundle.crt",
 				Contents: certificateBundle + "\n" + rootCertificate,
 				Perms:    0644,
 			})
 			outs = append(outs, outputFile{
-				Filename: baseName + "-root.pem",
+				Filename: baseName + "-root.crt",
 				Contents: rootCertificate,
 				Perms:    0644,
 			})