1 files changed, 73 insertions, 0 deletions
diff --git a/go/internal/logger/logger.go b/go/internal/logger/logger.go
new file mode 100644
index 0000000..6a4f2e3
--- /dev/null
+++ b/go/internal/logger/logger.go
@@ -0,0 +1,73 @@
+package logger
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"log/syslog"
+	"os"
+	"sync"
+	"time"
+
+	"gitlab.com/gitlab-org/gitlab-shell/go/internal/config"
+)
+
+var (
+	logWriter       io.Writer
+	bootstrapLogger *log.Logger
+	pid             int
+	mutex           sync.Mutex
+	ProgName        string
+)
+
+func Configure(cfg *config.Config) error {
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	pid = os.Getpid()
+
+	var err error
+	logWriter, err = os.OpenFile(cfg.LogFile, os.O_WRONLY|os.O_APPEND, 0)
+	return err
+}
+
+func logPrint(msg string, err error) {
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	if logWriter == nil {
+		bootstrapLogPrint(msg, err)
+		return
+	}
+
+	// Emulate the existing log format of gitlab-shell
+	t := time.Now().Format("2006-01-02T15:04:05.999999")
+	prefix := fmt.Sprintf("E, [%s #%d] ERROR -- : %s:", t, pid, ProgName)
+	fmt.Fprintf(logWriter, "%s %s: %v\n", prefix, msg, err)
+}
+
+func Fatal(msg string, err error) {
+	logPrint(msg, err)
+	// We don't show the error to the end user because it can leak
+	// information that is private to the GitLab server.
+	fmt.Fprintf(os.Stderr, "%s: fatal: %s\n", ProgName, msg)
+	os.Exit(1)
+}
+
+// If our log file is not available we want to log somewhere else, but
+// not to standard error because that leaks information to the user. This
+// function attemps to log to syslog.
+//
+// We assume the logging mutex is already locked.
+func bootstrapLogPrint(msg string, err error) {
+	if bootstrapLogger == nil {
+		var err error
+		bootstrapLogger, err = syslog.NewLogger(syslog.LOG_ERR|syslog.LOG_USER, 0)
+		if err != nil {
+			// The message will not be logged.
+			return
+		}
+	}
+
+	bootstrapLogger.Print(ProgName+":", msg+":", err)
+}