121 lines
3.8 KiB
Go
121 lines
3.8 KiB
Go
package verifier
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import (
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"context"
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"crypto/ed25519"
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"encoding/base64"
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"fmt"
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"strconv"
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"strings"
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"time"
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"golang.org/x/crypto/blake2b"
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)
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// Config struct for Verifier.
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type Config struct {
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}
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// Verifier implements the Verifier interface.
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type Verifier struct {
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config *Config
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}
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// New creates a new Verifier instance.
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func New(ctx context.Context, config *Config) (*Verifier, func() error, error) {
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v := &Verifier{config: config}
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return v, v.Close, nil
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}
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// Verify checks the signature for the given payload and public key.
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func (v *Verifier) Verify(ctx context.Context, body []byte, header []byte, publicKeyBase64 string) (bool, error) {
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createdTimestamp, expiredTimestamp, signature, err := parseAuthHeader(string(header))
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if err != nil {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return false, fmt.Errorf("error parsing header: %w", err)
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}
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signatureBytes, err := base64.StdEncoding.DecodeString(signature)
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if err != nil {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return false, fmt.Errorf("error decoding signature: %w", err)
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}
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currentTime := time.Now().Unix()
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if createdTimestamp > currentTime || currentTime > expiredTimestamp {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return false, fmt.Errorf("signature is expired or not yet valid")
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}
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createdTime := time.Unix(createdTimestamp, 0)
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expiredTime := time.Unix(expiredTimestamp, 0)
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signingString := hash(body, createdTime.Unix(), expiredTime.Unix())
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decodedPublicKey, err := base64.StdEncoding.DecodeString(publicKeyBase64)
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if err != nil {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return false, fmt.Errorf("error decoding public key: %w", err)
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}
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if !ed25519.Verify(ed25519.PublicKey(decodedPublicKey), []byte(signingString), signatureBytes) {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return false, fmt.Errorf("signature verification failed")
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}
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return true, nil
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}
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// parseAuthHeader extracts signature values from the Authorization header.
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func parseAuthHeader(header string) (int64, int64, string, error) {
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header = strings.TrimPrefix(header, "Signature ")
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parts := strings.Split(header, ",")
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signatureMap := make(map[string]string)
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for _, part := range parts {
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keyValue := strings.SplitN(strings.TrimSpace(part), "=", 2)
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if len(keyValue) == 2 {
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key := strings.TrimSpace(keyValue[0])
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value := strings.Trim(keyValue[1], "\"")
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signatureMap[key] = value
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}
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}
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createdTimestamp, err := strconv.ParseInt(signatureMap["created"], 10, 64)
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if err != nil {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return 0, 0, "", fmt.Errorf("invalid created timestamp: %w", err)
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}
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expiredTimestamp, err := strconv.ParseInt(signatureMap["expires"], 10, 64)
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if err != nil {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return 0, 0, "", fmt.Errorf("invalid expires timestamp: %w", err)
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}
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signature := signatureMap["signature"]
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if signature == "" {
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// TODO: Return appropriate error code when Error Code Handling Module is ready
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return 0, 0, "", fmt.Errorf("signature missing in header")
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}
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return createdTimestamp, expiredTimestamp, signature, nil
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}
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// hash constructs a signing string for verification.
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func hash(payload []byte, createdTimestamp, expiredTimestamp int64) string {
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hasher, _ := blake2b.New512(nil)
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hasher.Write(payload)
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hashSum := hasher.Sum(nil)
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digestB64 := base64.StdEncoding.EncodeToString(hashSum)
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return fmt.Sprintf("(created): %d\n(expires): %d\ndigest: BLAKE-512=%s", createdTimestamp, expiredTimestamp, digestB64)
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}
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// Close releases resources (mock implementation returning nil).
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func (v *Verifier) Close() error {
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return nil
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}
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