1 files changed, 48 insertions, 0 deletions
diff --git a/finger/system.go b/finger/system.go
new file mode 100644
index 0000000..7112967
--- /dev/null
+++ b/finger/system.go
@@ -0,0 +1,48 @@
+package finger
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"os/exec"
+
+	"tildegit.org/tjp/gus"
+)
+
+// ListingDenied is returned to reject online user listing requests.
+var ListingDenied = errors.New("Finger online user list denied.")
+
+// SystemFinger handles finger requests by invoking the finger(1) command-line utility.
+func SystemFinger(allowListings bool) gus.Handler {
+	return func(ctx context.Context, request *gus.Request) *gus.Response {
+		fingerPath, err := exec.LookPath("finger")
+		if err != nil {
+			_ = request.Server.LogError(
+				"msg", "handler failure",
+				"ctx", "exec.LookPath(\"finger\")",
+				"err", err,
+			)
+			return Error("Could not resolve request.")
+		}
+
+		path := request.Path[1:]
+
+		if len(path) == 0 && !allowListings {
+			return Error(ListingDenied.Error())
+		}
+
+		args := make([]string, 0, 1)
+		if len(path) > 0 {
+			args = append(args, path)
+		}
+
+		cmd := exec.CommandContext(ctx, fingerPath, args...)
+		outbuf := &bytes.Buffer{}
+		cmd.Stdout = outbuf
+
+		if err := cmd.Run(); err != nil {
+			return Error(err.Error())
+		}
+		return Success(outbuf)
+	}
+}