From 9f074d8b3a5868eca3b4f7504c951aaa20231d3f Mon Sep 17 00:00:00 2001
From: "Heiko Schlittermann (HS12-RIPE)" <hs@schlittermann.de>
Date: Thu, 23 Mar 2023 19:19:18 +0100
Subject: [PATCH] feat: allow logging to stdout

The --log option accepts "-" as filename. This prevents rest-server from
opening the log file, it simply writes to the STDOUT stream provided by
the caller.

**BREAKING** in case use really used "-" to specify a file named "-"
you'll need to update your rest-server invocation to use "./-".
---
 changelog/unreleased/pull-217 | 13 +++++++++++++
 cmd/rest-server/main.go       |  2 +-
 mux.go                        | 14 +++++++++++---
 3 files changed, 25 insertions(+), 4 deletions(-)
 create mode 100644 changelog/unreleased/pull-217

diff --git a/changelog/unreleased/pull-217 b/changelog/unreleased/pull-217
new file mode 100644
index 0000000..902d09c
--- /dev/null
+++ b/changelog/unreleased/pull-217
@@ -0,0 +1,13 @@
+Feature: Allows "-" as filename for the `--log` option.
+
+When (e.g. for debugging purpose) the rest server is invoked like
+
+	sudo -u restic rest-server … --log /dev/stdout
+
+it tries to open `/dev/stdout` (O_CREATE, O_WRITE, O_APPEND). This
+operation fails, as in the above invocation, `/dev/stdout` is owned by
+the caller (here: root) and only writable for the caller. Subprocesses
+get just the filedescriptor. Using `/proc/self/fd/1` didn't work either,
+for the same reasons.
+
+https://github.com/restic/rest-server/pull/217
diff --git a/cmd/rest-server/main.go b/cmd/rest-server/main.go
index e1baa39..ccace4d 100644
--- a/cmd/rest-server/main.go
+++ b/cmd/rest-server/main.go
@@ -46,7 +46,7 @@ func init() {
 	flags.StringVar(&cpuProfile, "cpu-profile", cpuProfile, "write CPU profile to file")
 	flags.BoolVar(&server.Debug, "debug", server.Debug, "output debug messages")
 	flags.StringVar(&server.Listen, "listen", server.Listen, "listen address")
-	flags.StringVar(&server.Log, "log", server.Log, "write HTTP requests in the combined log format to the specified `filename`")
+	flags.StringVar(&server.Log, "log", server.Log, "write HTTP requests in the combined log format to the specified `filename` (use \"-\" for logging to stdout)")
 	flags.Int64Var(&server.MaxRepoSize, "max-size", server.MaxRepoSize, "the maximum size of the repository in bytes")
 	flags.StringVar(&server.Path, "path", server.Path, "data directory")
 	flags.BoolVar(&server.TLS, "tls", server.TLS, "turn on TLS support")
diff --git a/mux.go b/mux.go
index 43e73b8..77fcdb4 100644
--- a/mux.go
+++ b/mux.go
@@ -2,6 +2,7 @@ package restserver
 
 import (
 	"fmt"
+	"io"
 	"log"
 	"net/http"
 	"os"
@@ -21,9 +22,16 @@ func (s *Server) debugHandler(next http.Handler) http.Handler {
 }
 
 func (s *Server) logHandler(next http.Handler) http.Handler {
-	accessLog, err := os.OpenFile(s.Log, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
-	if err != nil {
-		log.Fatalf("error: %v", err)
+	var accessLog io.Writer
+
+	if s.Log == "-" {
+		accessLog = os.Stdout
+	} else {
+		var err error
+		accessLog, err = os.OpenFile(s.Log, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+		if err != nil {
+			log.Fatalf("error: %v", err)
+		}
 	}
 
 	return handlers.CombinedLoggingHandler(accessLog, next)