I want to create and verify JWTs

Tink's JWT library allows the creation and verification of JSON Web Tokens (JWTs).

Create JWTs

We recommend the JwtPublicKeySign primitives with the JWT_ES256 key type for most use cases.

The following examples show how to create JWTs, and how to convert the public keyset into the JWK set format.

C++

// An example for signing JSON Web Tokens (JWT).
#include <iostream>
#include <memory>
#include <ostream>
#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 "absl/time/clock.h"
#include "absl/time/time.h"
#include "tink/config/global_registry.h"
#include "util/util.h"
#include "tink/jwt/jwt_public_key_sign.h"
#include "tink/jwt/jwt_signature_config.h"
#include "tink/jwt/raw_jwt.h"
#include "tink/keyset_handle.h"
#include "tink/util/status.h"

ABSL_FLAG(std::string, keyset_filename, "", "Keyset file in JSON format");
ABSL_FLAG(std::string, audience, "", "Expected audience in the token");
ABSL_FLAG(std::string, token_filename, "", "Path to the token file");

namespace {

using ::crypto::tink::JwtPublicKeySign;
using ::crypto::tink::KeysetHandle;
using ::crypto::tink::RawJwt;
using ::crypto::tink::RawJwtBuilder;
using ::crypto::tink::util::Status;
using ::crypto::tink::util::StatusOr;

void ValidateParams() {
  // ...
}

}  // namespace

namespace tink_cc_examples {

// JWT sign example CLI implementation.
Status JwtSign(const std::string& keyset_filename, absl::string_view audience,
               const std::string& token_filename) {
  Status result = crypto::tink::JwtSignatureRegister();
  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();
  StatusOr<RawJwt> raw_jwt =
      RawJwtBuilder()
          .AddAudience(audience)
          .SetExpiration(absl::Now() + absl::Seconds(100))
          .Build();
  if (!raw_jwt.ok()) return raw_jwt.status();
  StatusOr<std::unique_ptr<JwtPublicKeySign>> jwt_signer =
      (*keyset_handle)
          ->GetPrimitive<crypto::tink::JwtPublicKeySign>(
              crypto::tink::ConfigGlobalRegistry());
  if (!jwt_signer.ok()) return jwt_signer.status();

  StatusOr<std::string> token = (*jwt_signer)->SignAndEncode(*raw_jwt);
  if (!token.ok()) return token.status();

  return WriteToFile(*token, token_filename);
}

}  // namespace tink_cc_examples

int main(int argc, char** argv) {
  absl::ParseCommandLine(argc, argv);

  ValidateParams();

  std::string keyset_filename = absl::GetFlag(FLAGS_keyset_filename);
  std::string audience = absl::GetFlag(FLAGS_audience);
  std::string token_filename = absl::GetFlag(FLAGS_token_filename);

  std::clog << "Using keyset in " << keyset_filename << " to ";
  std::clog << " generate and sign a token using audience '" << audience
            << "'; the resulting signature is written to " << token_filename
            << '\n';

  CHECK_OK(
      tink_cc_examples::JwtSign(keyset_filename, audience, token_filename));
  return 0;
}
jwt_sign.cc

Go

func Example_signAndVerify() {
	// A private keyset created with
	// "tinkey create-keyset --key-template=JWT_ES256 --out private_keyset.cfg".
	// Note that this keyset has the secret key information in cleartext.
	privateJSONKeyset := `{
		"primaryKeyId": 1742360595,
		"key": [
			{
				"keyData": {
					"typeUrl": "type.googleapis.com/google.crypto.tink.JwtEcdsaPrivateKey",
					"value": "GiBgVYdAPg3Fa2FVFymGDYrI1trHMzVjhVNEMpIxG7t0HRJGIiBeoDMF9LS5BDCh6YgqE3DjHwWwnEKEI3WpPf8izEx1rRogbjQTXrTcw/1HKiiZm2Hqv41w7Vd44M9koyY/+VsP+SAQAQ==",
					"keyMaterialType": "ASYMMETRIC_PRIVATE"
				},
				"status": "ENABLED",
				"keyId": 1742360595,
				"outputPrefixType": "TINK"
			}
		]
	}`

	// The corresponding public keyset created with
	// "tinkey create-public-keyset --in private_keyset.cfg"
	publicJSONKeyset := `{
		"primaryKeyId": 1742360595,
		"key": [
			{
				"keyData": {
					"typeUrl": "type.googleapis.com/google.crypto.tink.JwtEcdsaPublicKey",
					"value": "EAEaIG40E1603MP9RyoomZth6r+NcO1XeODPZKMmP/lbD/kgIiBeoDMF9LS5BDCh6YgqE3DjHwWwnEKEI3WpPf8izEx1rQ==",
					"keyMaterialType": "ASYMMETRIC_PUBLIC"
				},
				"status": "ENABLED",
				"keyId": 1742360595,
				"outputPrefixType": "TINK"
			}
		]
	}`

	// Create a keyset handle from the cleartext private keyset in the previous
	// step. The keyset handle provides abstract access to the underlying keyset to
	// limit the access of 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.
	privateKeysetHandle, err := insecurecleartextkeyset.Read(
		keyset.NewJSONReader(bytes.NewBufferString(privateJSONKeyset)))
	if err != nil {
		log.Fatal(err)
	}

	// Retrieve the JWT Signer primitive from privateKeysetHandle.
	signer, err := jwt.NewSigner(privateKeysetHandle)
	if err != nil {
		log.Fatal(err)
	}

	// Use the primitive to create and sign a token. In this case, the primary key of the
	// keyset will be used (which is also the only key in this example).
	expiresAt := time.Now().Add(time.Hour)
	audience := "example audience"
	subject := "example subject"
	rawJWT, err := jwt.NewRawJWT(&jwt.RawJWTOptions{
		Audience:  &audience,
		Subject:   &subject,
		ExpiresAt: &expiresAt,
	})
	if err != nil {
		log.Fatal(err)
	}
	token, err := signer.SignAndEncode(rawJWT)
	if err != nil {
		log.Fatal(err)
	}

	// Create a keyset handle from the keyset containing the public key. Because the
	// public keyset does not contain any secrets, we can use [keyset.ReadWithNoSecrets].
	publicKeysetHandle, err := keyset.ReadWithNoSecrets(
		keyset.NewJSONReader(bytes.NewBufferString(publicJSONKeyset)))
	if err != nil {
		log.Fatal(err)
	}

	// Retrieve the Verifier primitive from publicKeysetHandle.
	verifier, err := jwt.NewVerifier(publicKeysetHandle)
	if err != nil {
		log.Fatal(err)
	}

	// Verify the signed token.
	validator, err := jwt.NewValidator(&jwt.ValidatorOpts{ExpectedAudience: &audience})
	if err != nil {
		log.Fatal(err)
	}
	verifiedJWT, err := verifier.VerifyAndDecode(token, validator)
	if err != nil {
		log.Fatal(err)
	}

	// Extract subject claim from the token.
	if !verifiedJWT.HasSubject() {
		log.Fatal(err)
	}
	extractedSubject, err := verifiedJWT.Subject()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(extractedSubject)
	// Output: example subject
}
jwt_test.go

Java

package jwt;

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.RegistryConfiguration;
import com.google.crypto.tink.TinkJsonProtoKeysetFormat;
import com.google.crypto.tink.jwt.JwtPublicKeySign;
import com.google.crypto.tink.jwt.JwtSignatureConfig;
import com.google.crypto.tink.jwt.RawJwt;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.Instant;

/**
 * A command-line utility for signing JSON Web Tokens (JWTs).
 *
 * <p>It loads cleartext private keys from disk - this is not recommended!
 *
 * <p>It requires the following arguments:
 *
 * <ul>
 *   <li>private-keyset-file: Name of the input file containing the private keyset.
 *   <li>audience: The audience claim to be used in the token
 *   <li>token-file: name of the output file containing the signed JWT.
 */
public final class JwtSign {
  public static void main(String[] args) throws Exception {
    if (args.length != 3) {
      System.err.printf("Expected 3 parameters, got %d\n", args.length);
      System.err.println("Usage: java JwtSign private-keyset-file audience token-file");
      System.exit(1);
    }

    Path privateKeysetFile = Paths.get(args[0]);
    String audience = args[1];
    Path tokenFile = Paths.get(args[2]);

    // Register all JWT signature key types with the Tink runtime.
    JwtSignatureConfig.register();

    // Read the private keyset into a KeysetHandle.
    KeysetHandle privateKeysetHandle =
        TinkJsonProtoKeysetFormat.parseKeyset(
            new String(Files.readAllBytes(privateKeysetFile), UTF_8),
            InsecureSecretKeyAccess.get());

    // Get the primitive.
    JwtPublicKeySign signer =
        privateKeysetHandle.getPrimitive(RegistryConfiguration.get(), JwtPublicKeySign.class);

    // Use the primitive to sign a token that expires in 100 seconds.
    RawJwt rawJwt =
        RawJwt.newBuilder()
            .addAudience(audience)
            .setExpiration(Instant.now().plusSeconds(100))
            .build();
    String signedToken = signer.signAndEncode(rawJwt);
    Files.write(tokenFile, signedToken.getBytes(UTF_8));
  }

  private JwtSign() {}
}
JwtSign.java

Python

"""A utility for creating and signing JSON Web Tokens (JWT).

It loads cleartext keys from disk - this is not recommended!
"""

import datetime

from absl import app
from absl import flags
from absl import logging
import tink
from tink import jwt
from tink import secret_key_access


_PRIVATE_KEYSET_PATH = flags.DEFINE_string(
    'private_keyset_path', None,
    'Path to the keyset used for the JWT signature operation.')
_AUDIENCE = flags.DEFINE_string('audience', None,
                                'Audience to be used in the token')
_TOKEN_PATH = flags.DEFINE_string('token_path', None, 'Path to the token file.')


def main(argv):
  del argv  # Unused.

  # Initialise Tink
  jwt.register_jwt_signature()

  # Read the keyset into a KeysetHandle
  with open(_PRIVATE_KEYSET_PATH.value, 'rt') as keyset_file:
    try:
      text = keyset_file.read()
      keyset_handle = tink.json_proto_keyset_format.parse(
          text, secret_key_access.TOKEN
      )
    except tink.TinkError as e:
      logging.exception('Error reading keyset: %s', e)
      return 1

  now = datetime.datetime.now(tz=datetime.timezone.utc)

  # Get the JwtPublicKeySign primitive
  try:
    jwt_sign = keyset_handle.primitive(jwt.JwtPublicKeySign)
  except tink.TinkError as e:
    logging.exception('Error creating JwtPublicKeySign: %s', e)
    return 1

  # Create token
  raw_jwt = jwt.new_raw_jwt(
      audiences=[_AUDIENCE.value],
      expiration=now + datetime.timedelta(seconds=100))
  token = jwt_sign.sign_and_encode(raw_jwt)
  with open(_TOKEN_PATH.value, 'wt') as token_file:
    token_file.write(token)
  logging.info('Token has been written to %s', _TOKEN_PATH.value)


if __name__ == '__main__':
  flags.mark_flags_as_required(
      ['private_keyset_path', 'audience', 'token_path'])
  app.run(main)
jwt_sign_cli.py

A common way to share the public keyset is the JWK set format. The following example shows how to convert the public keyset into the JWK set format.

C++

// An example for converting a Tink keyset with public keys into a JWK set.
#include <iostream>
#include <memory>
#include <ostream>
#include <string>

#include "absl/flags/flag.h"
#include "absl/flags/parse.h"
#include "absl/log/check.h"
#include "util/util.h"
#include "tink/jwt/jwk_set_converter.h"
#include "tink/jwt/jwt_signature_config.h"
#include "tink/keyset_handle.h"
#include "tink/util/status.h"

ABSL_FLAG(std::string, public_keyset_filename, "",
          "Public keyset file in Tink's JSON format");
ABSL_FLAG(std::string, public_jwk_set_filename, "",
          "Path to the output public JWK set file");

namespace {

using ::crypto::tink::JwkSetFromPublicKeysetHandle;
using ::crypto::tink::KeysetHandle;
using ::crypto::tink::util::Status;
using ::crypto::tink::util::StatusOr;

void ValidateParams() {
  // ...
}

}  // namespace

namespace tink_cc_examples {

Status JwtGeneratePublicJwkSet(const std::string& public_keyset_filename,
                               const std::string& public_jwk_set_filename) {
  Status result = crypto::tink::JwtSignatureRegister();
  if (!result.ok()) return result;

  StatusOr<std::unique_ptr<KeysetHandle>> keyset_handle =
      ReadJsonCleartextKeyset(public_keyset_filename);
  if (!keyset_handle.ok()) return keyset_handle.status();

  StatusOr<std::string> public_jwk_set =
      JwkSetFromPublicKeysetHandle(**keyset_handle);
  if (!public_jwk_set.ok()) return keyset_handle.status();

  return WriteToFile(*public_jwk_set, public_jwk_set_filename);
}

}  // namespace tink_cc_examples

int main(int argc, char** argv) {
  absl::ParseCommandLine(argc, argv);

  ValidateParams();

  std::string public_keyset_filename =
      absl::GetFlag(FLAGS_public_keyset_filename);
  std::string public_jwk_set_filename =
      absl::GetFlag(FLAGS_public_jwk_set_filename);

  std::clog << "Convert public keyset in " << public_keyset_filename << " to ";
  std::clog << " to JWK set format; the result is written to "
            << public_jwk_set_filename << '\n';

  CHECK_OK(tink_cc_examples::JwtGeneratePublicJwkSet(public_keyset_filename,
                                                     public_jwk_set_filename));
  return 0;
}
jwt_generate_public_jwk_set.cc

Go

func Example_generateJWKS() {
	// A Tink keyset in JSON format with one JWT public key.
	publicJSONKeyset := `{
		"primaryKeyId": 1742360595,
		"key": [
			{
				"keyData": {
					"typeUrl": "type.googleapis.com/google.crypto.tink.JwtEcdsaPublicKey",
					"value": "EAEaIG40E1603MP9RyoomZth6r+NcO1XeODPZKMmP/lbD/kgIiBeoDMF9LS5BDCh6YgqE3DjHwWwnEKEI3WpPf8izEx1rQ==",
					"keyMaterialType": "ASYMMETRIC_PUBLIC"
				},
				"status": "ENABLED",
				"keyId": 1742360595,
				"outputPrefixType": "TINK"
			}
		]
	}`

	// Create a keyset handle from the keyset containing the public key. Because the
	// public keyset does not contain any secrets, we can use [keyset.ReadWithNoSecrets].
	publicKeysetHandle, err := keyset.ReadWithNoSecrets(
		keyset.NewJSONReader(bytes.NewBufferString(publicJSONKeyset)))
	if err != nil {
		log.Fatal(err)
	}

	// Create a publicJWKset from publicKeysetHandle.
	publicJWKset, err := jwt.JWKSetFromPublicKeysetHandle(publicKeysetHandle)
	if err != nil {
		log.Fatal(err)
	}

	// Remove whitespace so that we can compare it to the expected string.
	compactPublicJWKset := &bytes.Buffer{}
	err = json.Compact(compactPublicJWKset, publicJWKset)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(compactPublicJWKset.String())
	// Output:
	// {"keys":[{"alg":"ES256","crv":"P-256","key_ops":["verify"],"kid":"Z9pQEw","kty":"EC","use":"sig","x":"bjQTXrTcw_1HKiiZm2Hqv41w7Vd44M9koyY_-VsP-SA","y":"XqAzBfS0uQQwoemIKhNw4x8FsJxChCN1qT3_IsxMda0"}]}
}
jwt_test.go

Java

package jwt;

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.TinkJsonProtoKeysetFormat;
import com.google.crypto.tink.jwt.JwkSetConverter;
import com.google.crypto.tink.jwt.JwtSignatureConfig;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * A command-line example for generating the public JWT keyset in JWK set format.
 *
 * <p>It loads cleartext private keys from disk - this is not recommended!
 *
 * <p>It requires the following arguments:
 *
 * <ul>
 *   <li>private-keyset-file: Name of the input file containing the private keyset.
 *   <li>public-jwkset-file: Name of the output file containing the public key in JWK set format.
 */
public final class JwtGeneratePublicJwkSet {
  public static void main(String[] args) throws Exception {
    if (args.length != 2) {
      System.err.printf("Expected 2 parameters, got %d\n", args.length);
      System.err.println(
          "Usage: java JwtGeneratePublicJwkSet private-keyset-file public-jwk-set-file");
      System.exit(1);
    }

    Path privateKeysetFile = Paths.get(args[0]);
    Path publicJwkSetFile = Paths.get(args[1]);

    // Register all JWT signature key types with the Tink runtime.
    JwtSignatureConfig.register();

    // Read the keyset into a KeysetHandle.
    KeysetHandle privateKeysetHandle =
        TinkJsonProtoKeysetFormat.parseKeyset(
            new String(Files.readAllBytes(privateKeysetFile), UTF_8),
            InsecureSecretKeyAccess.get());

    // Export the public keyset as JWK set.
    String publicJwkSet =
        JwkSetConverter.fromPublicKeysetHandle(privateKeysetHandle.getPublicKeysetHandle());
    Files.write(publicJwkSetFile, publicJwkSet.getBytes(UTF_8));
  }

  private JwtGeneratePublicJwkSet() {}
}
JwtGeneratePublicJwkSet.java

Python

"""A utility for generating the public JWK set from the public keyset.
"""

from absl import app
from absl import flags
from absl import logging
import tink
from tink import jwt


_PUBLIC_KEYSET_PATH = flags.DEFINE_string(
    'public_keyset_path', None,
    'Path to the public keyset in Tink JSON format.')
_PUBLIC_JWK_SET_PATH = flags.DEFINE_string(
    'public_jwk_set_path', None, 'Path to public keyset in JWK format.')


def main(argv):
  del argv  # Unused.

  # Initialise Tink
  jwt.register_jwt_signature()

  # Read the keyset into a KeysetHandle
  with open(_PUBLIC_KEYSET_PATH.value, 'rt') as keyset_file:
    try:
      text = keyset_file.read()
      public_keyset_handle = tink.json_proto_keyset_format.parse_without_secret(
          text
      )
    except tink.TinkError as e:
      logging.exception('Error reading keyset: %s', e)
      return 1

  # Export Public Keyset as JWK set
  public_jwk_set = jwt.jwk_set_from_public_keyset_handle(public_keyset_handle)
  with open(_PUBLIC_JWK_SET_PATH.value, 'wt') as public_jwk_set_file:
    public_jwk_set_file.write(public_jwk_set)
  logging.info('The public JWK set has been written to %s',
               _PUBLIC_JWK_SET_PATH.value)


if __name__ == '__main__':
  flags.mark_flags_as_required(['public_keyset_path', 'public_jwk_set_path'])
  app.run(main)
jwt_generate_public_jwk_set.py

Verify JWTs

We recommend the JwtPublicKeyVerify primitives with the JWT_ES256 key type for most use cases.

The following examples show how to verify JWTs using a public keyset in the JWK set format, which is a commonly used format for sharing public keysets with other parties.

C++

// A utility for creating, signing and verifying JSON Web Tokens (JWT).
#include <iostream>
#include <memory>
#include <ostream>
#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 "tink/config/global_registry.h"
#include "util/util.h"
#include "tink/jwt/jwk_set_converter.h"
#include "tink/jwt/jwt_public_key_verify.h"
#include "tink/jwt/jwt_signature_config.h"
#include "tink/jwt/jwt_validator.h"
#include "tink/keyset_handle.h"
#include "tink/util/status.h"

ABSL_FLAG(std::string, jwk_set_filename, "", "Path to the JWK set file");
ABSL_FLAG(std::string, audience, "", "Expected audience in the token");
ABSL_FLAG(std::string, token_filename, "", "Path to the token file");

namespace {

using ::crypto::tink::JwkSetToPublicKeysetHandle;
using ::crypto::tink::JwtPublicKeyVerify;
using ::crypto::tink::JwtValidator;
using ::crypto::tink::KeysetHandle;
using ::crypto::tink::util::Status;
using ::crypto::tink::util::StatusOr;

void ValidateParams() {
  // ...
}

}  // namespace

namespace tink_cc_examples {

// JWT verify example CLI implementation.
Status JwtVerify(const std::string& jwk_set_filename,
                 absl::string_view audience,
                 const std::string& token_filename) {
  Status result = crypto::tink::JwtSignatureRegister();
  if (!result.ok()) return result;

  // Read the JWK set from file and convert it.
  StatusOr<std::string> jwk_set = ReadFile(jwk_set_filename);
  if (!jwk_set.ok()) return jwk_set.status();
  StatusOr<std::unique_ptr<KeysetHandle>> keyset_handle =
      JwkSetToPublicKeysetHandle(*jwk_set);

  // Read the token.
  StatusOr<std::string> token = ReadFile(token_filename);
  if (!token.ok()) return token.status();

  StatusOr<JwtValidator> validator =
      crypto::tink::JwtValidatorBuilder().ExpectAudience(audience).Build();
  if (!validator.ok()) return validator.status();

  StatusOr<std::unique_ptr<JwtPublicKeyVerify>> jwt_verifier =
      (*keyset_handle)
          ->GetPrimitive<crypto::tink::JwtPublicKeyVerify>(
              crypto::tink::ConfigGlobalRegistry());
  if (!jwt_verifier.ok()) return jwt_verifier.status();

  return (*jwt_verifier)->VerifyAndDecode(*token, *validator).status();
}

}  // namespace tink_cc_examples

int main(int argc, char** argv) {
  absl::ParseCommandLine(argc, argv);

  ValidateParams();

  std::string jwk_set_filename = absl::GetFlag(FLAGS_jwk_set_filename);
  std::string audience = absl::GetFlag(FLAGS_audience);
  std::string token_filename = absl::GetFlag(FLAGS_token_filename);

  std::clog << "Using keyset in " << jwk_set_filename << " to ";
  std::clog << " verify a token with expected audience '" << audience << '\n';

  CHECK_OK(
      tink_cc_examples::JwtVerify(jwk_set_filename, audience, token_filename));
  return 0;
}
jwt_verify.cc

Go

func Example_verifyWithJWKS() {
	// A signed token with the subject 'example subject', audience 'example audience'.
	// and expiration on 2023-03-23.
	token := `eyJhbGciOiJFUzI1NiIsICJraWQiOiJaOXBRRXcifQ.eyJhdWQiOiJleGFtcGxlIGF1ZGllbmNlIiwgImV4cCI6MTY3OTUzMzIwMCwgInN1YiI6ImV4YW1wbGUgc3ViamVjdCJ9.ZvI0T84fJ1aouiB7n62kHOmbm0Hpfiz0JtYs15XVDT8KyoVYZ8hu_DGJUN47BqZIbuOI-rdu9TxJvutj8uF3Ow`

	// A public keyset in the JWK set format.
	publicJWKset := `{
		"keys":[
			{
				"alg":"ES256",
				"crv":"P-256",
				"key_ops":["verify"],
				"kid":"Z9pQEw",
				"kty":"EC",
				"use":"sig",
				"x":"bjQTXrTcw_1HKiiZm2Hqv41w7Vd44M9koyY_-VsP-SA",
				"y":"XqAzBfS0uQQwoemIKhNw4x8FsJxChCN1qT3_IsxMda0"
			}
		]
	}`

	// Create a keyset handle from publicJWKset.
	publicKeysetHandle, err := jwt.JWKSetToPublicKeysetHandle([]byte(publicJWKset))
	if err != nil {
		log.Fatal(err)
	}

	// Retrieve the Verifier primitive from publicKeysetHandle.
	verifier, err := jwt.NewVerifier(publicKeysetHandle)
	if err != nil {
		log.Fatal(err)
	}

	// Verify the signed token. For this example, we use a fixed date. Usually, you would
	// either not set FixedNow, or set it to the current time.
	audience := "example audience"
	validator, err := jwt.NewValidator(&jwt.ValidatorOpts{
		ExpectedAudience: &audience,
		FixedNow:         time.Date(2023, 3, 23, 0, 0, 0, 0, time.UTC),
	})
	if err != nil {
		log.Fatal(err)
	}
	verifiedJWT, err := verifier.VerifyAndDecode(token, validator)
	if err != nil {
		log.Fatal(err)
	}

	// Extract subject claim from the token.
	if !verifiedJWT.HasSubject() {
		log.Fatal(err)
	}
	extractedSubject, err := verifiedJWT.Subject()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(extractedSubject)
	// Output: example subject
}
jwt_test.go

Java

package jwt;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.crypto.tink.KeysetHandle;
import com.google.crypto.tink.RegistryConfiguration;
import com.google.crypto.tink.jwt.JwkSetConverter;
import com.google.crypto.tink.jwt.JwtPublicKeyVerify;
import com.google.crypto.tink.jwt.JwtSignatureConfig;
import com.google.crypto.tink.jwt.JwtValidator;
import com.google.crypto.tink.jwt.VerifiedJwt;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.Instant;
import java.time.temporal.ChronoUnit;
import java.util.List;

/**
 * A command-line utility for verifying JSON Web Tokens (JWTs).
 *
 * <p>It requires the following arguments:
 *
 * <ul>
 *   <li>public-jwkset-file: Name of the input file containing the public keyset in JWK set format.
 *   <li>audience: The audience claim to be used in the token
 *   <li>token-file: name of the input file containing the signed JWT.
 */
public final class JwtVerify {
  public static void main(String[] args) throws Exception {
    if (args.length != 3) {
      System.err.printf("Expected 3 parameters, got %d\n", args.length);
      System.err.println(
          "Usage: java JwtVerify public-jwk-set-file audience token-file");
      System.exit(1);
    }

    Path publicJwkSetFile = Paths.get(args[0]);
    String audience = args[1];
    Path tokenFile = Paths.get(args[2]);

    // Register all JWT signature key types with the Tink runtime.
    JwtSignatureConfig.register();

    // Read the public keyset in JWK set format into a KeysetHandle.
    KeysetHandle publicKeysetHandle =
        JwkSetConverter.toPublicKeysetHandle(
            new String(Files.readAllBytes(publicJwkSetFile), UTF_8));

    List<String> lines = Files.readAllLines(tokenFile, UTF_8);
    if (lines.size() != 1) {
      System.err.printf("The signature file should contain only one line,  got %d", lines.size());
      System.exit(1);
    }
    String signedToken = lines.get(0).trim();

    // Get the primitive.
    JwtPublicKeyVerify verifier =
        publicKeysetHandle.getPrimitive(RegistryConfiguration.get(), JwtPublicKeyVerify.class);

    // Use the primitive to verify a token.
    JwtValidator validator = JwtValidator.newBuilder().expectAudience(audience).build();
    VerifiedJwt verifiedJwt = verifier.verifyAndDecode(signedToken, validator);
    long seconds = ChronoUnit.SECONDS.between(Instant.now(), verifiedJwt.getExpiration());
    System.out.println("Token is valid and expires in " + seconds + " seconds.");
  }

  private JwtVerify() {}
}
JwtVerify.java

Python

"""A utility for verifying Json Web Tokens (JWT)."""

import datetime

from absl import app
from absl import flags
from absl import logging
import tink
from tink import jwt


FLAGS = flags.FLAGS

_PUBLIC_JWK_SET_PATH = flags.DEFINE_string(
    'public_jwk_set_path', None, 'Path to public keyset in JWK set format.')
_AUDIENCE = flags.DEFINE_string('audience', None,
                                'Audience to be used in the token')
_TOKEN_PATH = flags.DEFINE_string('token_path', None,
                                  'Path to the signature file.')


def main(argv):
  del argv  # Unused.

  # Initialise Tink
  jwt.register_jwt_signature()

  with open(_PUBLIC_JWK_SET_PATH.value, 'rt') as public_jwk_set_file:
    try:
      text = public_jwk_set_file.read()
      keyset_handle = jwt.jwk_set_to_public_keyset_handle(text)
    except tink.TinkError as e:
      logging.exception('Error reading public JWK set: %s', e)
      return 1

  now = datetime.datetime.now(tz=datetime.timezone.utc)
  try:
    jwt_verify = keyset_handle.primitive(jwt.JwtPublicKeyVerify)
  except tink.TinkError as e:
    logging.exception('Error creating JwtPublicKeyVerify: %s', e)
    return 1

  # Verify token
  with open(_TOKEN_PATH.value, 'rt') as token_file:
    token = token_file.read()
  validator = jwt.new_validator(expected_audience=_AUDIENCE.value)
  try:
    verified_jwt = jwt_verify.verify_and_decode(token, validator)
    expires_in = verified_jwt.expiration() - now
    logging.info('Token is valid and expires in %s seconds', expires_in.seconds)
    return 0
  except tink.TinkError as e:
    logging.info('JWT verification failed: %s', e)
    return 1


if __name__ == '__main__':
  flags.mark_flags_as_required(['audience', 'token_path'])
  app.run(main)
jwt_verify_cli.py

JSON Web Tokens (JWTs)

Tink supports generating and verifying JWTs, which are a widely used standard on the web. Tink's JWT implementation provides a subset of the JWT standard defined in RFC 7519 that the Tink team considers safe to use, and that fits well into the Tink library.

Tink does not support parts of the standard that are rarely used or difficult to use correctly. These are the limitations:

• Tink only supports the JWS Compact Serialization format. JWS JSON Serialization and JWE are not supported.
• Tink does not support the None value in the alg header.
• Tink only supports the headers typ, alg, and kid. All other headers are not supported.
• Tink does not allow tokens to be parsed before the signature or MAC is verified.

JWT Signatures

If tokens are generated and verified by different entities, then you should use asymmetric keys with the primitives JwtPublicKeySign and JwtPublicKeyVerify. The private key is used to generate tokens, and the public key is used to verify tokens. The algorithms supported by these primitives are: ES256, ES384, ES512, RS256, RS384, RS512, PS256, PS384 and PS512.

Choose a key type

JWT signatures use different key types than the normal digital signature in Tink. This is needed because some metadata (such as algand kid) needs to be stored with the key.

We recommend using JWT_ES256 for most use cases. Tokens generated with this key type always have a kid header. If you prefer slightly shorter tokens without a kid header, choose the key type JWT_ES256_RAW. For all supported key types, see Supported Key Types.

Public keyset distribution

Tink allows public keysets to be converted to and from the JWK Sets format defined in RFC 7517, which most JWT libraries understand.

Note: Tink's JSON keyset serialization format is not a JWK Set and other libraries will probably not be able to read it.

Tink does not support exporting public JWT keys in any other format. The reason for this is that other formats don't contain the alg and kid metadata to be used in the verification, which makes using them more error-prone and may make it more difficult to rotate keys.

It is preferable to not just share the public keyset once, but to provide a way to automatically update the public keyset. (If not, rotating to a new key is very hard.) This is often done by publishing the public keyset on a trusted and secured URL. A server that verifies tokens then has to periodically re-fetch the public keyset from that URL, for example once per day. To rotate the key, the new public key needs to be added to the public keyset at least one day before it is used to sign tokens. Otherwise the new tokens signed with the new private key will be rejected by servers that still use the old public keyset.

Note: Some implementations re-fetch the public key as soon as a token with an unknown kid header is received. Implementing this logic is not possible in Tink, since the token is not parsed before it is verified. We don't recommend doing this anyway, as it may result in lots of extra requests to the keyset URL if malicious tokens with random kid headers are sent.

JWT MAC

Tink also supports JWT with symmetric keys with the primitive JwtMac. Only use this primitive if the tokens are generated and verified by the same entity. The algorithms supported by this primitive are HS256, HS384 and HS512.

Choose a key type

JWT MAC key types are different from normal MAC key types. We recommend using JWT_HS256 for most use cases.