Add HadSessions to check if there have ever been sessions (#487)

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Co-authored-by: terrorbyte <terrorbyte@users.noreply.github.com>

Author: lobsterjerusalem

c2/channel/channel.go

@@ -35,6 +35,19 @@ type Session struct {
 	LastSeen       time.Time
 }
 
+// HadSessions checks if a channel has any tracked sessions. This can be used to lookup if a C2
+// successfully received callbacks ever, regardless of whether or not it is currently active.
+//
+//	c, ok := c2.GetInstance(conf.C2Type)
+//	c.Channel().HadSessions()
+func (c *Channel) HadSessions() bool {
+	// Currently sessions are only added to the session structure and then their states are modified.
+	// This will only work as long as the sessions are never actually removed from the map, which for
+	// now isn't an issue but if we ever switch to a history vs active tracking systtem then this will
+	// not be sufficient.
+	return len(c.Sessions) > 0
+}
+
 // HasSessions checks if a channel has any tracked sessions. This can be used to lookup if a C2
 // successfully received callbacks:
 //

c2/factory.go

@@ -152,6 +152,35 @@ func CreateFlags(implementation Impl) {
 	}
 }
 
+// HadSessions returns if the underlying channel has any sessions, regardless of their Active value.
+func HadSessions(implementation Impl) bool {
+	switch implementation.Category {
+	case SimpleShellServerCategory:
+		return simpleshell.GetServerInstance().Channel().HadSessions()
+	case SimpleShellClientCategory:
+		return simpleshell.GetClientInstance().Channel().HadSessions()
+	case SSLShellServerCategory:
+		return sslshell.GetInstance().Channel().HadSessions()
+	case HTTPServeFileCategory:
+		return httpservefile.GetInstance().Channel().HadSessions()
+	case HTTPServeShellCategory:
+		return httpserveshell.GetInstance().Channel().HadSessions()
+	case ExternalCategory:
+		if implementation.Name != "" {
+			return external.GetInstance(implementation.Name).Channel().HadSessions()
+		}
+	case HTTPShellServerCategory:
+		return httpshellserver.GetInstance().Channel().HadSessions()
+	case ShellTunnelCategory:
+		return shelltunnel.GetInstance().Channel().HadSessions()
+	case InvalidCategory:
+	default:
+	}
+	output.PrintFrameworkError("Invalid C2 Server")
+
+	return false
+}
+
 // HasSessions returns if the underlying channel has active sessions. This is useful for code that
 // needs to validate if callbacks have occurred and is a helper wrapper around the channel package
 // function of the same name.