Add comments and function descriptions

1 files changed, 21 insertions, 3 deletions

diff --git a/core/verification.go b/core/verification.go
index f1e1f0b..289ce1e 100644
--- a/core/verification.go
+++ b/core/verification.go
@@ -12,8 +12,7 @@ import (
 	"github.com/tarm/serial"
 )
 
-//var TotalReadBlocks int = 0
-
+// fileReadKey reads the public minisign key from a file specified in config.KeyLocation.
 func fileReadKey() (string, error) {
 	if _, err := os.Stat(config.KeyLocation); os.IsNotExist(err) {
 		return "", fmt.Errorf("Key location %s does not exist", config.KeyLocation)
@@ -23,6 +22,7 @@ func fileReadKey() (string, error) {
 		return "", err
 	}
 	defer file.Close()
+	// A public key is never longer than 56 bytes
 	key := make([]byte, 56)
 	reader := bufio.NewReader(file)
 	n, err := reader.Read(key)
@@ -35,7 +35,11 @@ func fileReadKey() (string, error) {
 	return string(key), nil
 }
 
+// serialReadKey reads the public minisign key from a usb tty specified in config.KeyLocation.
 func serialReadKey() (string, error) {
+	// Since the usb serial is tested with an arduino
+	// it is assumed that the tty device does not always exist
+	// and can be manually plugged in by the user
 	if _, err := os.Stat(config.KeyLocation); !os.IsNotExist(err) {
 		fmt.Println("Reconnect arduino now")
 		for true {
@@ -67,6 +71,9 @@ func serialReadKey() (string, error) {
 		}
 		defer s.Close()
 		key = key + fmt.Sprintf("%q", buf[:n])
+		// ensure that two tab sequences are read
+		// meaning that the entire key has been captured
+		// since the key is surrounded by a tab sequence
 		if strings.Count(key, "\\t") == 2 {
 			break
 		}
@@ -79,6 +86,7 @@ func serialReadKey() (string, error) {
 	return key, nil
 }
 
+// ReadKey is a wrapper function to call the proper readKey function according to config.KeyStore.
 func ReadKey() (string, error) {
 	switch config.KeyStore {
 	case 0:
@@ -86,14 +94,21 @@ func ReadKey() (string, error) {
 	case 1:
 		return fileReadKey()
 	case 2:
-		return "", nil
+		return "", nil // TPM
 	case 3:
 		return serialReadKey()
 	}
 	return "", nil
 }
 
+// ReadBlock reads a data area of a bytes.Reader specified in the given node.
+// It additionally verifies that the amount of bytes read equal the wanted amount and returns an error if this is not the case.
 func ReadBlock(node Node, part *bytes.Reader, totalReadBlocks int) ([]byte, int, error) {
+	if node.BlockEnd-node.BlockStart < 0 {
+		return []byte{}, -1, fmt.Errorf("tried creating byte slice with negative length. %d to %d total %d\n", node.BlockStart, node.BlockEnd, node.BlockEnd-node.BlockStart)
+	} else if node.BlockEnd-node.BlockStart > 2000 {
+		return []byte{}, -1, fmt.Errorf("tried creating byte slice with length over 2000. %d to %d total %d\n", node.BlockStart, node.BlockEnd, node.BlockEnd-node.BlockStart)
+	}
 	block := make([]byte, node.BlockEnd-node.BlockStart)
 	blockSize := node.BlockEnd - node.BlockStart
 	_, err := part.Seek(int64(node.BlockStart), 0)
@@ -109,6 +124,7 @@ func ReadBlock(node Node, part *bytes.Reader, totalReadBlocks int) ([]byte, int,
 	return block, totalReadBlocks + 1, err
 }
 
+// VerifySignature verifies the database using a given signature and public key.
 func VerifySignature(key string, signature string, database string) (bool, error) {
 	var pk minisign.PublicKey
 	if err := pk.UnmarshalText([]byte(key)); err != nil {
@@ -123,6 +139,7 @@ func VerifySignature(key string, signature string, database string) (bool, error
 	return minisign.Verify(pk, data, []byte(signature)), nil
 }
 
+// VerifyBlock verifies a byte slice with the hash in a given Node.
 func VerifyBlock(block []byte, node Node) error {
 	calculatedBlockHash, err := CalculateBlockHash(block)
 	if err != nil {
@@ -135,6 +152,7 @@ func VerifyBlock(block []byte, node Node) error {
 	return fmt.Errorf("Node %s ranging from %d to %d does not match block. Expected %s, got %s.", node.PrevNodeSum, node.BlockStart, node.BlockEnd, wantedBlockHash, calculatedBlockHash)
 }
 
+// VerifyNode verifies that the current Node is valid by matching the checksum of it with the PrevNodeSum field of the next node.
 func VerifyNode(node Node, nextNode Node) error {
 	nodeHash, err := calculateStringHash(fmt.Sprintf("%d%d%s%s", node.BlockStart, node.BlockEnd, node.BlockSum, node.PrevNodeSum))
 	if err != nil {