Consigliamo il tipo di chiave HMAC_SHA256 per la maggior parte dei casi d'uso. Per tutti i tipi di chiavi supportati, consulta la sezione Tipi di chiavi supportati.
Se vuoi assicurarti che nessuno possa manomettere i tuoi dati, ti consigliamo la primitiva MAC (Message Authentication Code). che usa un'unica chiave per generare i codici di autenticazione dei messaggi e verificarli. L'indirizzo MAC non cripta i dati. Nella maggior parte dei casi, la protezione dei dati con AEAD, che include crittografia e MAC, è preferibile rispetto a solo MAC.
Gli esempi riportati di seguito mostrano come iniziare a utilizzare la primitiva MAC.
C++
// A command-line utility for showcasing using the Tink MAC primitive.
#include <fstream>
#include <iostream>
#include <memory>
#include <ostream>
#include <sstream>
#include <string>
#include <utility>
#include "absl/flags/flag.h"
#include "absl/flags/parse.h"
#include "absl/log/check.h"
#include "absl/strings/string_view.h"
#include "util/util.h"
#include "tink/keyset_handle.h"
#include "tink/mac.h"
#include "tink/mac/mac_config.h"
#include "tink/util/status.h"
ABSL_FLAG(std::string, keyset_filename, "", "Keyset file in JSON format");
ABSL_FLAG(std::string, mode, "", "Mode of operation {compute|verify}");
ABSL_FLAG(std::string, data_filename, "", "Data file name");
ABSL_FLAG(std::string, tag_filename, "", "Authentication tag file name");
namespace {
using ::crypto::tink::KeysetHandle;
using ::crypto::tink::Mac;
using ::crypto::tink::MacConfig;
using ::crypto::tink::util::Status;
using ::crypto::tink::util::StatusOr;
constexpr absl::string_view kCompute = "compute";
constexpr absl::string_view kVerify = "verify";
void ValidateParams() {
// ...
}
} // namespace
namespace tink_cc_examples {
// MAC example CLI implementation.
Status MacCli(absl::string_view mode, const std::string keyset_filename,
const std::string& data_filename,
const std::string& tag_filename) {
Status result = MacConfig::Register();
if (!result.ok()) return result;
// Read the keyset from file.
StatusOr<std::unique_ptr<KeysetHandle>> keyset_handle =
ReadJsonCleartextKeyset(keyset_filename);
if (!keyset_handle.ok()) return keyset_handle.status();
// Get the primitive.
StatusOr<std::unique_ptr<Mac>> mac_primitive =
(*keyset_handle)
->GetPrimitive<crypto::tink::Mac>(
crypto::tink::ConfigGlobalRegistry());
if (!mac_primitive.ok()) return mac_primitive.status();
// Read the input.
StatusOr<std::string> data_file_content = ReadFile(data_filename);
if (!data_file_content.ok()) return data_file_content.status();
std::string output;
if (mode == kCompute) {
// Compute authentication tag.
StatusOr<std::string> compute_result =
(*mac_primitive)->ComputeMac(*data_file_content);
if (!compute_result.ok()) return compute_result.status();
// Write out the authentication tag to tag file.
return WriteToFile(*compute_result, tag_filename);
} else { // operation == kVerify.
// Read the authentication tag from tag file.
StatusOr<std::string> tag_result = ReadFile(tag_filename);
if (!tag_result.ok()) {
std::cerr << tag_result.status().message() << std::endl;
exit(1);
}
// Verify authentication tag.
Status verify_result =
(*mac_primitive)->VerifyMac(*tag_result, *data_file_content);
if (verify_result.ok()) std::clog << "Verification succeeded!" << std::endl;
return verify_result;
}
}
} // namespace tink_cc_examples
int main(int argc, char** argv) {
absl::ParseCommandLine(argc, argv);
ValidateParams();
std::string mode = absl::GetFlag(FLAGS_mode);
std::string keyset_filename = absl::GetFlag(FLAGS_keyset_filename);
std::string data_filename = absl::GetFlag(FLAGS_data_filename);
std::string tag_filename = absl::GetFlag(FLAGS_tag_filename);
std::clog << "Using keyset from file '" << keyset_filename << "' to " << mode
<< " authentication tag from file '" << tag_filename
<< "' for data file '" << data_filename << "'." << std::endl;
std::clog << "The tag will be "
<< ((mode == kCompute) ? "written to" : "read from") << " file '"
<< tag_filename << "'." << std::endl;
CHECK_OK(tink_cc_examples::MacCli(mode, keyset_filename, data_filename,
tag_filename));
return 0;
}
Go
import (
"bytes"
"fmt"
"log"
"github.com/tink-crypto/tink-go/v2/insecurecleartextkeyset"
"github.com/tink-crypto/tink-go/v2/keyset"
"github.com/tink-crypto/tink-go/v2/mac"
)
func Example() {
// A keyset created with "tinkey create-keyset --key-template=HMAC_SHA256_128BITTAG".
// Note that this keyset has the secret key information in cleartext.
jsonKeyset := `{
"key": [{
"keyData": {
"keyMaterialType":
"SYMMETRIC",
"typeUrl":
"type.googleapis.com/google.crypto.tink.HmacKey",
"value":
"EgQIAxAQGiA0LQjovcydWhVQV3k8W9ZSRkd7Ei4Y/TRWApE8guwV4Q=="
},
"keyId": 1892702217,
"outputPrefixType": "TINK",
"status": "ENABLED"
}],
"primaryKeyId": 1892702217
}`
// Create a keyset handle from the cleartext keyset in the previous
// step. The keyset handle provides abstract access to the underlying keyset to
// limit the exposure of accessing the raw key material. WARNING: In practice,
// it is unlikely you will want to use a insecurecleartextkeyset, as it implies
// that your key material is passed in cleartext, which is a security risk.
// Consider encrypting it with a remote key in Cloud KMS, AWS KMS or HashiCorp Vault.
// See https://github.com/google/tink/blob/master/docs/GOLANG-HOWTO.md#storing-and-loading-existing-keysets.
keysetHandle, err := insecurecleartextkeyset.Read(
keyset.NewJSONReader(bytes.NewBufferString(jsonKeyset)))
if err != nil {
log.Fatal(err)
}
// Retrieve the MAC primitive we want to use from the keyset handle.
primitive, err := mac.New(keysetHandle)
if err != nil {
log.Fatal(err)
}
// Use the primitive to create a MAC tag for some data. In this case the primary
// key of the keyset will be used (which is also the only key in this example).
data := []byte("data")
tag, err := primitive.ComputeMAC(data)
if err != nil {
log.Fatal(err)
}
// Use the primitive to verify the tag. VerifyMAC finds the correct key in
// the keyset. If no key is found or verification fails, it returns an error.
err = primitive.VerifyMAC(tag, data)
if err != nil {
log.Fatal(err)
}
fmt.Printf("tag is valid")
// Output: tag is valid
}
Java
package mac;
import static java.nio.charset.StandardCharsets.UTF_8;
import com.google.crypto.tink.InsecureSecretKeyAccess;
import com.google.crypto.tink.KeysetHandle;
import com.google.crypto.tink.Mac;
import com.google.crypto.tink.TinkJsonProtoKeysetFormat;
import com.google.crypto.tink.mac.MacConfig;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
/**
* A command-line utility for checking file integrity with a Message Authentication Code (MAC).
*
* <p>It loads cleartext keys from disk - this is not recommended!
*
* <p>It requires the following arguments:
*
* <ul>
* <li>mode: either 'compute' or 'verify'.
* <li>key-file: Read the key material from this file.
* <li>input-file: Read the input from this file.
* <li>mac-file: name of the file containing a hexadecimal MAC of the input data.
*/
public final class MacExample {
public static void main(String[] args) throws Exception {
if (args.length != 4) {
System.err.printf("Expected 4 parameters, got %d\n", args.length);
System.err.println("Usage: java MacExample compute/verify key-file input-file mac-file");
System.exit(1);
}
String mode = args[0];
if (!mode.equals("compute") && !mode.equals("verify")) {
System.err.println("Incorrect mode. Please select compute or verify.");
System.exit(1);
}
Path keyFile = Paths.get(args[1]);
byte[] msg = Files.readAllBytes(Paths.get(args[2]));
Path macFile = Paths.get(args[3]);
// Register all MAC key types with the Tink runtime.
MacConfig.register();
// Read the keyset into a KeysetHandle.
KeysetHandle handle =
TinkJsonProtoKeysetFormat.parseKeyset(
new String(Files.readAllBytes(keyFile), UTF_8), InsecureSecretKeyAccess.get());
// Get the primitive.
Mac macPrimitive = handle.getPrimitive(Mac.class);
if (mode.equals("compute")) {
byte[] macTag = macPrimitive.computeMac(msg);
Files.write(macFile, macTag);
} else {
byte[] macTag = Files.readAllBytes(macFile);
// This will throw a GeneralSecurityException if verification fails.
macPrimitive.verifyMac(macTag, msg);
}
}
private MacExample() {}
}
Python
import tink
from tink import mac
from tink import secret_key_access
def example():
"""Compute and verify MAC tags."""
# Register the MAC key managers. This is needed to create a Mac primitive
# later.
mac.register()
# Created with "tinkey create-keyset --key-template=HMAC_SHA256_128BITTAG".
# Note that this keyset has the secret key information in cleartext.
keyset = r"""{
"key": [{
"keyData": {
"keyMaterialType":
"SYMMETRIC",
"typeUrl":
"type.googleapis.com/google.crypto.tink.HmacKey",
"value":
"EgQIAxAQGiA0LQjovcydWhVQV3k8W9ZSRkd7Ei4Y/TRWApE8guwV4Q=="
},
"keyId": 1892702217,
"outputPrefixType": "TINK",
"status": "ENABLED"
}],
"primaryKeyId": 1892702217
}"""
# Create a keyset handle from the cleartext keyset in the previous
# step. The keyset handle provides abstract access to the underlying keyset to
# limit access of the raw key material. WARNING: In practice, it is unlikely
# you will want to use tink.json_proto_keyset_format.parse, as it implies that
# your key material is passed in cleartext, which is a security risk.
keyset_handle = tink.json_proto_keyset_format.parse(
keyset, secret_key_access.TOKEN
)
# Retrieve the Mac primitive we want to use from the keyset handle.
primitive = keyset_handle.primitive(mac.Mac)
# Use the primitive to compute the MAC for a message. In this case the primary
# key of the keyset will be used (which is also the only key in this example).
data = b'data'
tag = primitive.compute_mac(data)
# Use the primitive to verify the MAC for the message. Verify finds the
# correct key in the keyset and verifies the MAC. If no key is found or
# verification fails, it raises an error.
primitive.verify_mac(tag, data)