fix(logs): contain server-name-derived log path within log dir

CodeQL go/path-injection flagged the daemon log reader
(internal/server/server.go) where a user-controlled server name flows into
the log file path. logs.ServerLogFilename already sanitizes the name to a
single path element, so the flow is safe, but CodeQL does not recognize the
strings.Map char-whitelist as a barrier. Add an explicit filepath.Clean +
prefix containment guard at both log-read sites (daemon reader and the
no-daemon CLI reader, which feeds tail) so the resolved path can never escape
the log directory. Defense-in-depth + clears the alert without weakening any
check. Valid namespaced names (io.github.owner/repo) are unaffected — their
sanitized filename stays a single element under logDir.

Related #604

Author: Dumbris

cmd/mcpproxy/upstream_cmd.go

@@ -774,6 +774,14 @@ func runUpstreamLogsFromFile(globalConfig *config.Config, serverName string) err
 
 	logFile := filepath.Join(logDir, logs.ServerLogFilename(serverName))
 
+	// Defense-in-depth: logs.ServerLogFilename already sanitizes the (user-controlled)
+	// server name to a single path element, but verify the resolved path stays inside
+	// logDir before it reaches os.Stat/tail so a crafted name can never escape the log
+	// directory (path-injection barrier).
+	if !strings.HasPrefix(filepath.Clean(logFile), filepath.Clean(logDir)+string(os.PathSeparator)) {
+		return fmt.Errorf("invalid server name: %s", serverName)
+	}
+
 	// Check if file exists
 	if _, err := os.Stat(logFile); os.IsNotExist(err) {
 		return fmt.Errorf("log file not found: %s (daemon may not have run yet)", logFile)

internal/server/server.go

@@ -2284,6 +2284,13 @@ func (s *Server) GetServerLogs(serverName string, tail int) ([]contracts.LogEntr
 
 	logFile := filepath.Join(logDir, logs.ServerLogFilename(serverName))
 
+	// Defense-in-depth: logs.ServerLogFilename already sanitizes the (user-controlled)
+	// server name to a single path element, but verify the resolved path stays inside
+	// logDir so a crafted name can never escape the log directory (path-injection barrier).
+	if !strings.HasPrefix(filepath.Clean(logFile), filepath.Clean(logDir)+string(os.PathSeparator)) {
+		return nil, fmt.Errorf("invalid server name: %s", serverName)
+	}
+
 	// Check if file exists
 	if _, err := os.Stat(logFile); os.IsNotExist(err) {
 		return nil, fmt.Errorf("log file not found: %s (server may not have run yet)", logFile)