1 files changed, 165 insertions, 0 deletions
diff --git a/verify/core/verification.go b/verify/core/verification.go
new file mode 100644
index 0000000..289ce1e
--- /dev/null
+++ b/verify/core/verification.go
@@ -0,0 +1,165 @@
+package core
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"strings"
+
+	"aead.dev/minisign"
+	"github.com/axtloss/fsverify/config"
+	"github.com/tarm/serial"
+)
+
+// 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)
+	}
+	file, err := os.Open(config.KeyLocation)
+	if err != nil {
+		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)
+	if n != 56 {
+		return "", fmt.Errorf("Key does not match expected key size. Expected 56, got %d", n)
+	}
+	if err != nil {
+		return "", err
+	}
+	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 {
+			if _, err := os.Stat(config.KeyLocation); os.IsNotExist(err) {
+				break
+			}
+		}
+	} else {
+		fmt.Println("Connect arduino now")
+	}
+	for true {
+		if _, err := os.Stat(config.KeyLocation); !os.IsNotExist(err) {
+			break
+		}
+	}
+	fmt.Println("Arduino connected")
+	c := &serial.Config{Name: config.KeyLocation, Baud: 9600}
+	s, err := serial.OpenPort(c)
+	if err != nil {
+		return "", err
+	}
+
+	key := ""
+	for true {
+		buf := make([]byte, 128)
+		n, err := s.Read(buf)
+		if err != nil {
+			return "", err
+		}
+		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
+		}
+	}
+	key = strings.ReplaceAll(key, "\\t", "")
+	key = strings.ReplaceAll(key, "\"", "")
+	if len(key) != 56 {
+		return "", fmt.Errorf("Key does not match expected key size. Expected 56, got %d", len(key))
+	}
+	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:
+		return fileReadKey()
+	case 1:
+		return fileReadKey()
+	case 2:
+		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)
+	if err != nil {
+		return []byte{}, -1, err
+	}
+	n, err := part.Read(block)
+	if err != nil {
+		return block, -1, err
+	} else if n != blockSize {
+		return block, -1, fmt.Errorf("Did not read correct amount of bytes. Expected: %d, Got: %d", blockSize, n)
+	}
+	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 {
+		return false, err
+	}
+
+	data, err := os.ReadFile(database)
+	if err != nil {
+		return false, err
+	}
+
+	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 {
+		return err
+	}
+	wantedBlockHash := node.BlockSum
+	if strings.Compare(calculatedBlockHash, strings.TrimSpace(wantedBlockHash)) == 0 {
+		return nil
+	}
+	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 {
+		return err
+	}
+	if strings.Compare(nodeHash, nextNode.PrevNodeSum) != 0 {
+		return fmt.Errorf("Node %s is not valid!", node.PrevNodeSum)
+	}
+	return nil
+}