add support for multiple secrets (independent agents) on the knock daemon

This allows you to generate more than one pre-shared secret on the knock daemon so that you can distribute the secret and control revocation at a more granular level.  Each additional secret creates one more concurrent authentic knock sequence.

hypd/configuration/configuration.go

@@ -12,7 +12,6 @@ type HypdConfiguration struct {
 	SuccessAction         string `json:"successAction"`         // The action to take for a successful knock, each argument is a separate string
 	TimeoutSeconds        int    `json:"timeoutSeconds"`        // If > 0, once a knock sequence has been successful this value will count down and when it reaches 0, it will perform the TimeoutAction on the client
 	TimeoutAction         string `json:"timeoutAction"`         // The action to take after TimeoutSeconds has elapsed.  only applicable if TimeoutSeconds is > 0, each argument is a separate string
-
 }
 
 // LoadConfiguration opens and parses the configuration file into a HypdConfiguration struct

hypd/configuration/secrets.go

@@ -0,0 +1,49 @@
+package configuration
+
+import (
+	"encoding/base32"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+var secrets [][]byte
+
+// LoadSecrets processes all files within the specified directory and attempts to
+// convert the file contents to secrets to by used by hypd
+func LoadSecrets(preSharedKeyDirectory string) ([][]byte, error) {
+	secrets = make([][]byte, 0)
+	err := filepath.Walk(preSharedKeyDirectory, processSecretFile)
+	if err != nil {
+		return nil, fmt.Errorf("failed to walk directory '%s': %w", preSharedKeyDirectory, err)
+	}
+
+	return secrets, nil
+}
+
+// processSecretFile is called against each file in the preSharedKeyDirectory
+// It reads each file and attemts to base32 decode their contents
+func processSecretFile(path string, info fs.FileInfo, err error) error {
+	if err != nil {
+		return fmt.Errorf("failed to process file '%s': %w", path, err)
+	}
+
+	if info.IsDir() {
+		return nil
+	}
+
+	secretBytes, err := os.ReadFile(path)
+	if err != nil {
+		return fmt.Errorf("failed to read file '%s': %w", path, err)
+	}
+
+	decodedSecret, err := base32.StdEncoding.DecodeString(string(secretBytes))
+	if err != nil {
+		return fmt.Errorf("failed to base32 decode secret '%s': %w", path, err)
+	}
+
+	secrets = append(secrets, decodedSecret)
+
+	return nil
+}