# NAME Crypt::JWT - JSON Web Token (JWT, JWS, JWE) as defined by RFC7519, RFC7515, RFC7516 # SYNOPSIS # encoding use Crypt::JWT qw(encode_jwt); my $jws_token = encode_jwt(payload=>$data, alg=>'HS256', key=>'secret'); my $jwe_token = encode_jwt(payload=>$data, alg=>'PBES2-HS256+A128KW', enc=>'A128GCM', key=>'secret'); # decoding use Crypt::JWT qw(decode_jwt); my $data1 = decode_jwt(token=>$jws_token, key=>'secret'); my $data2 = decode_jwt(token=>$jwe_token, key=>'secret'); # DESCRIPTION Implements **JSON Web Token (JWT)** - [https://tools.ietf.org/html/rfc7519](https://tools.ietf.org/html/rfc7519). The implementation covers not only **JSON Web Signature (JWS)** - [https://tools.ietf.org/html/rfc7515](https://tools.ietf.org/html/rfc7515), but also **JSON Web Encryption (JWE)** - [https://tools.ietf.org/html/rfc7516](https://tools.ietf.org/html/rfc7516). The module implements all algorithms defined in [https://tools.ietf.org/html/rfc7518](https://tools.ietf.org/html/rfc7518) - **JSON Web Algorithms (JWA)**. This module supports **Compact JWS/JWE** and **Flattened JWS/JWE JSON** serialization. General (multi-recipient) JSON serialization is not supported. # EXPORT Nothing is exported by default. You can export selected functions: use Crypt::JWT qw(decode_jwt encode_jwt); Or all of them at once: use Crypt::JWT ':all'; # FUNCTIONS ## decode\_jwt my $data = decode_jwt(%named_args); my ($header, $data) = decode_jwt(%named_args, decode_header=>1); Returns the decoded payload (in scalar context) or the decoded header followed by the decoded payload (when `decode_header => 1`). Croaks on any verification, decryption, or claim-check failure. Named arguments: - token Mandatory. The serialized JWS or JWE token as a string. Both compact (`.`-separated, 3 segments for JWS / 5 for JWE) and flattened JSON serialization are accepted. ### JWS compact (3 segments) $t = "eyJhbGciOiJIUzI1NiJ9.dGVzdA.ujBihtLSr66CEWqN74SpLUkv28lra_CeHnxLmLNp4Jo"; my $data = decode_jwt(token=>$t, key=>$k); ### JWE compact (5 segments) $t = "eyJlbmMiOiJBMTI4R0NNIiwiYWxnIjoiQTEyOEtXIn0.UusxEbzhGkORxTRq0xkFKhvzPrXb9smw.VGfOuq0Fxt6TsdqLZUpnxw.JajIQQ.pkKZ7MHS0XjyGmRsqgom6w"; my $data = decode_jwt(token=>$t, key=>$k); - key A key used for token decryption (JWE) or token signature validation (JWS). The value depends on the `alg` token header value. **Since: 0.038** **SECURITY:** how the `key` argument is shaped matters. - A bare scalar (e.g. `'secret'`) is always interpreted as a raw octet string (HMAC secret, AES key, etc.). - PEM, DER, and JWK-JSON key material **must** be passed as a SCALAR ref (`\$pem`) or as an appropriate key object - never as a bare string. - If a public-key string is mistakenly passed as a bare scalar and `accepted_alg` is not set, an attacker who flips the token's `alg` to `HS*` can forge a signature using the public-key bytes as the HMAC secret (the so-called "alg confusion" attack). - For defense in depth, **always** pin the algorithm with `accepted_alg`. Overview of supported keys: JWS alg header key value ------------------ ---------------------------------- none no key required HS256 string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') HS384 same as HS256 HS512 same as HS256 RS256 public RSA key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, object: Crypt::PK::RSA, Crypt::OpenSSL::RSA, Crypt::X509 or Crypt::OpenSSL::X509 RS384 public RSA key, see RS256 RS512 public RSA key, see RS256 PS256 public RSA key, see RS256 PS384 public RSA key, see RS256 PS512 public RSA key, see RS256 ES256 public ECC key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, an instance of Crypt::PK::ECC ES256K public ECC key, see ES256 ES384 public ECC key, see ES256 ES512 public ECC key, see ES256 EdDSA public Ed25519 key JWE alg header key value ------------------ ---------------------------------- dir string (raw octets) or perl HASH ref with JWK, kty=>'oct', length depends on 'enc' algorithm A128KW string (raw octets) 16 bytes (or perl HASH ref with JWK, kty=>'oct') A192KW string (raw octets) 24 bytes (or perl HASH ref with JWK, kty=>'oct') A256KW string (raw octets) 32 bytes (or perl HASH ref with JWK, kty=>'oct') A128GCMKW string (raw octets) 16 bytes (or perl HASH ref with JWK, kty=>'oct') A192GCMKW string (raw octets) 24 bytes (or perl HASH ref with JWK, kty=>'oct') A256GCMKW string (raw octets) 32 bytes (or perl HASH ref with JWK, kty=>'oct') PBES2-HS256+A128KW string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') PBES2-HS384+A192KW string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') PBES2-HS512+A256KW string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') RSA-OAEP private RSA key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, an instance of Crypt::PK::RSA or Crypt::OpenSSL::RSA RSA-OAEP-256 private RSA key, see RSA-OAEP RSA1_5 private RSA key, see RSA-OAEP ECDH-ES private ECC or X25519 key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, an instance of Crypt::PK::ECC ECDH-ES+A128KW private ECC or X25519 key, see ECDH-ES ECDH-ES+A192KW private ECC or X25519 key, see ECDH-ES ECDH-ES+A256KW private ECC or X25519 key, see ECDH-ES Example using the key from `jwk` token header: my $data = decode_jwt(token=>$t, key_from_jwk_header=>1); my ($header, $data) = decode_jwt(token=>$t, decode_header=>1, key_from_jwk_header=>1); Examples with raw octet keys: #string my $data = decode_jwt(token=>$t, key=>'secretkey'); #binary key my $data = decode_jwt(token=>$t, key=>pack("H*", "788A6E38F36B7596EF6A669E94")); #perl HASH ref with JWK structure (key type 'oct') my $data = decode_jwt(token=>$t, key=>{kty=>'oct', k=>"GawgguFyGrWKav7AX4VKUg"}); Examples with RSA keys: my $pem_key_string = <<'EOF'; -----BEGIN PRIVATE KEY----- MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCoVm/Sl5r+Ofky jioRSZK26GW6WyjyfWKddsSi13/NOtCn0rRErSF/u3QrgGMpWFqKohqbi1VVC+SZ ... 8c1vm2YFafgdkSk9Qd1oU2Fv1aOQy4VovOFzJ3CcR+2r7cbRfcpLGnintHtp9yek 02p+d5g4OChfFNDhDtnIqjvY -----END PRIVATE KEY----- EOF my $jwk_key_json_string = '{"kty":"RSA","n":"0vx7agoebG...L6tSoc_BJECP","e":"AQAB"}'; #a reference to SCALAR string with PEM or DER or JSON/JWK data, my $data = decode_jwt(token=>$t, key=>\$pem_key_string); my $data = decode_jwt(token=>$t, key=>\$der_key_string); my $data = decode_jwt(token=>$t, key=>\$jwk_key_json_string); #instance of Crypt::PK::RSA my $data = decode_jwt(token=>$t, key=>Crypt::PK::RSA->new('keyfile.pem')); my $data = decode_jwt(token=>$t, key=>Crypt::PK::RSA->new(\$pem_key_string)); #instance of Crypt::OpenSSL::RSA my $data = decode_jwt(token=>$t, key=>Crypt::OpenSSL::RSA->new_private_key($pem_key_string)); #instance of Crypt::X509 (public key only) my $data = decode_jwt(token=>$t, key=>Crypt::X509->new(cert=>$cert)); #instance of Crypt::OpenSSL::X509 (public key only) my $data = decode_jwt(token=>$t, key=>Crypt::OpenSSL::X509->new_from_file('cert.pem')); my $data = decode_jwt(token=>$t, key=>Crypt::OpenSSL::X509->new_from_string($cert)); #perl HASH ref with JWK structure (key type 'RSA') my $rsa_priv = { kty => "RSA", n => "0vx7agoebGcQSuuPiLJXZpt...eZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw", e => "AQAB", d => "X4cTteJY_gn4FYPsXB8rdXi...FLN5EEaG6RoVH-HLKD9Mdx5ooGURknhnrRwUkC7h5fJLMWbFAKLWY2v7B6NqSzUvx0_YSf", p => "83i-7IvMGXoMXCskv73TKr8...Z27zvoj6pbUQyLPBQxtPnwD20-60eTmD2ujMt5PoMrm8RmNhVWtjjMmMjOpSicFHjXOuVI", q => "3dfOR9cuYq-0S-mkFLzgItg...q3hWeMuG0ouqnb3obLyuqjVZQ1dIrdgTnCdYzBcOW5r37AFXjift_NGiovonzhKpoVVS78", dp => "G4sPXkc6Ya9y8oJW9_ILj4...zi_H7TkS8x5SdX3oE0oiYwxIiemTAu0UOa5pgFGyJ4c8t2VF40XRugKTP8akhFo5tA77Qe", dq => "s9lAH9fggBsoFR8Oac2R_E...T2kGOhvIllTE1efA6huUvMfBcpn8lqW6vzzYY5SSF7pMd_agI3G8IbpBUb0JiraRNUfLhc", qi => "GyM_p6JrXySiz1toFgKbWV...4ypu9bMWx3QJBfm0FoYzUIZEVEcOqwmRN81oDAaaBk0KWGDjJHDdDmFW3AN7I-pux_mHZG", }; my $data = decode_jwt(token=>$t, key=>$rsa_priv); Examples with ECC keys: my $pem_key_string = <<'EOF'; -----BEGIN EC PRIVATE KEY----- MHcCAQEEIBG1c3z52T8XwMsahGVdOZWgKCQJfv+l7djuJjgetdbDoAoGCCqGSM49 AwEHoUQDQgAEoBUyo8CQAFPeYPvv78ylh5MwFZjTCLQeb042TjiMJxG+9DLFmRSM lBQ9T/RsLLc+PmpB1+7yPAR+oR5gZn3kJQ== -----END EC PRIVATE KEY----- EOF my $jwk_key_json_string = '{"kty":"EC","crv":"P-256","x":"MKB..7D4","y":"4Et..FyM"}'; #a reference to SCALAR string with PEM or DER or JSON/JWK data, my $data = decode_jwt(token=>$t, key=>\$pem_key_string); my $data = decode_jwt(token=>$t, key=>\$der_key_string); my $data = decode_jwt(token=>$t, key=>\$jwk_key_json_string); #instance of Crypt::PK::ECC my $data = decode_jwt(token=>$t, key=>Crypt::PK::ECC->new('keyfile.pem')); my $data = decode_jwt(token=>$t, key=>Crypt::PK::ECC->new(\$pem_key_string)); #perl HASH ref with JWK structure (key type 'EC') my $ecc_priv = { kty => "EC", crv => "P-256", x => "MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4", y => "4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM", d => "870MB6gfuTJ4HtUnUvYMyJpr5eUZNP4Bk43bVdj3eAE", }; my $data = decode_jwt(token=>$t, key=>$ecc_priv); - keypass Optional. When the `key` parameter is an encrypted private RSA or ECC key (PEM/DER), this parameter holds the password used to decrypt it. - kid\_keys This parameter can be either a JWK Set JSON string (see RFC7517) or a perl HASH ref with JWK Set structure like this: my $keylist = { keys => [ { kid=>"key1", kty=>"oct", k=>"GawgguFyGrWKav7AX4VKUg" }, { kid=>"key2", kty=>"oct", k=>"ulxLGy4XqhbpkR5ObGh1gX" }, ] }; my $payload = decode_jwt(token=>$t, kid_keys=>$keylist); You can use ["export\_key\_jwk" in Crypt::PK::RSA](https://metacpan.org/pod/Crypt%3A%3APK%3A%3ARSA#export_key_jwk) to generate a JWK for RSA: my $pubkey = Crypt::PK::RSA->new('rs256-4096-public.pem'); my $jwk_hash = $pubkey->export_key_jwk('public', 1); $jwk_hash->{kid} = 'key1'; my $keylist = { keys => [ $jwk_hash, ] }; The structure described above is used e.g. by [https://www.googleapis.com/oauth2/v2/certs](https://www.googleapis.com/oauth2/v2/certs) use Mojo::UserAgent; my $ua = Mojo::UserAgent->new; my $google_keys = $ua->get('https://www.googleapis.com/oauth2/v2/certs')->result->json; my $payload = decode_jwt(token => $t, kid_keys => $google_keys); **Since: 0.019** An alternative structure (used e.g. by [https://www.googleapis.com/oauth2/v1/certs](https://www.googleapis.com/oauth2/v1/certs)) is also accepted: use LWP::Simple; my $google_certs = get('https://www.googleapis.com/oauth2/v1/certs'); my $payload = decode_jwt(token => $t, kid_keys => $google_certs); When the token header contains a `kid` item, the corresponding key is looked up in the `kid_keys` list and used for token decoding (you do not need to pass the explicit key via the `key` parameter). Add a `kid` header on the encode side via ["extra\_headers"](#extra_headers). **INCOMPATIBLE CHANGE Since: 0.023** When `kid_keys` is specified, decoding croaks if the token header does not contain a `kid` value or if the `kid` was not found in `kid_keys`. - key\_from\_jwk\_header **Since: 0.023** `1` - use `jwk` header value for validating JWS signature if neither `key` nor `kid_keys` specified, **BEWARE: DANGEROUS, INSECURE.** `0` (default) - ignore `jwk` header value when validating JWS signature Keep in mind that enabling `key_from_jwk_header` requires the `jwk` header to exist and to be a valid RSA/ECDSA public key (otherwise it croaks). - allow\_none `1` - accept JWS tokens with `none` 'alg' header value (which means that token has no signature), **BEWARE: DANGEROUS, INSECURE.** `0` (default) - do not allow JWS with `none` 'alg' header value - ignore\_signature `1` - do not check signature on JWS tokens, **BEWARE: DANGEROUS, INSECURE.** `0` (default) - check signature on JWS tokens - accepted\_alg **Since: 0.038** **SECURITY:** strongly recommended. Pinning `accepted_alg` to the algorithm (or family) you actually expect prevents "alg confusion" attacks where a forged token swaps the `alg` header to a different family \- see the SECURITY note under `key`. Accepted value types: - `undef` (default) - accept all `alg` algorithms except `none` (for accepting `none` use `allow_none`) - Scalar string - the single accepted `alg` name - ARRAY ref - list of accepted `alg` names - `Regexp` - the `alg` value must match this regexp Example: my $payload = decode_jwt(token=>$t, key=>$k, accepted_alg=>'HS256'); my $payload = decode_jwt(token=>$t, key=>$k, accepted_alg=>['HS256','HS384']); my $payload = decode_jwt(token=>$t, key=>$k, accepted_alg=>qr/^HS(256|384|512)$/); **INCOMPATIBLE CHANGE Since: 0.038** Any other argument type (HASH ref, CODE ref, GLOB ref, etc.) now croaks at decode time; previously such typos silently became no-ops on the JWE side. - accepted\_enc JWE only. Restricts which content-encryption algorithms are accepted. Accepted value types (same shape as ["accepted\_alg"](#accepted_alg)): - `undef` (default) - accept all `enc` algorithms - Scalar string - the single accepted `enc` name - ARRAY ref - list of accepted `enc` names - `Regexp` - the `enc` value must match this regexp Example: my $payload = decode_jwt(token=>$t, key=>$k, accepted_enc=>'A192GCM'); my $payload = decode_jwt(token=>$t, key=>$k, accepted_enc=>['A192GCM','A256GCM']); my $payload = decode_jwt(token=>$t, key=>$k, accepted_enc=>qr/^A(128|192|256)GCM$/); - decode\_payload `0` - do not decode payload, return it as a raw string (octets). `1` - decode payload from JSON string, return it as perl hash ref (or array ref) - decode\_json failure means fatal error (croak). `undef` (default) - if possible decode payload from JSON string, if decode\_json fails return payload as a raw string (octets). - decode\_header `0` (default) - `decode_jwt` returns just the decoded payload (scalar context). `1` - `decode_jwt` returns `($header, $payload)`; useful when you need to inspect the JWT header (e.g. `alg`, `kid`, `typ`). my $payload = decode_jwt(token=>$t, key=>$k); my ($header, $payload) = decode_jwt(token=>$t, key=>$k, decode_header=>1); - verify\_iss **INCOMPATIBLE CHANGE Since: 0.024** If `verify_iss` is specified and the `iss` (Issuer) claim is completely missing, verification fails. `CODE ref` - subroutine (with 'iss' claim value passed as argument) should return `true` otherwise verification fails `Regexp ref` - 'iss' claim value has to match given regexp otherwise verification fails `Scalar` - 'iss' claim value has to be equal to given string. **Since: 0.029** `undef` (default) - do not verify 'iss' claim - verify\_aud **INCOMPATIBLE CHANGE Since: 0.024** If `verify_aud` is specified and the `aud` (Audience) claim is completely missing, verification fails. `CODE ref` - subroutine (with 'aud' claim value passed as argument) should return `true` otherwise verification fails `Regexp ref` - 'aud' claim value has to match given regexp otherwise verification fails `Scalar` - 'aud' claim value has to be equal to given string. **Since: 0.029** `undef` (default) - do not verify 'aud' claim **Since: 0.036** The `aud` claim may also be an array of strings. The check succeeds if at least one array element matches; the configured check (CODE, Regexp, Scalar) is applied individually to each element. - verify\_sub **INCOMPATIBLE CHANGE Since: 0.024** If `verify_sub` is specified and the `sub` (Subject) claim is completely missing, verification fails. `CODE ref` - subroutine (with 'sub' claim value passed as argument) should return `true` otherwise verification fails `Regexp ref` - 'sub' claim value has to match given regexp otherwise verification fails `Scalar` - 'sub' claim value has to be equal to given string. **Since: 0.029** `undef` (default) - do not verify 'sub' claim - verify\_jti **INCOMPATIBLE CHANGE Since: 0.024** If `verify_jti` is specified and the `jti` (JWT ID) claim is completely missing, verification fails. `CODE ref` - subroutine (with 'jti' claim value passed as argument) should return `true` otherwise verification fails `Regexp ref` - 'jti' claim value has to match given regexp otherwise verification fails `Scalar` - 'jti' claim value has to be equal to given string. **Since: 0.029** `undef` (default) - do not verify 'jti' claim - verify\_iat **NOTE:** `verify_iat` is asymmetric with `verify_nbf`/`verify_exp`. Omitting the key entirely (the true default) means "no iat check". Passing `verify_iat => undef` is **not** the same as omitting it - it explicitly enables the present-but-must-be-valid check below. `undef` - "validate-if-present" mode: if the payload contains an 'iat' claim it must not be in the future (modulo `leeway`), otherwise verification croaks; if 'iat' is absent, no error is raised. Useful when you want to honor an issuer's 'iat' when they provide one but not insist on it being there. `0` - ignore 'iat' claim (same as omitting the key) `1` - require valid 'iat' claim: payload must contain 'iat' and it must not be in the future (modulo `leeway`); croaks otherwise. If the `verify_iat` key is not passed at all, no iat check is performed regardless of whether the payload contains an 'iat' claim. - verify\_nbf `undef` (default) - Not Before 'nbf' claim must be valid if present `0` - ignore 'nbf' claim `1` - require valid 'nbf' claim - verify\_exp `undef` (default) - Expiration Time 'exp' claim must be valid if present `0` - ignore 'exp' claim `1` - require valid 'exp' claim - leeway Tolerance in seconds related to `verify_exp`, `verify_nbf` and `verify_iat`. Default is `0`. - ignore\_claims `1` - do not check claims (iat, exp, nbf, iss, aud, sub, jti), **BEWARE: DANGEROUS, INSECURE.** `0` (default) - check claims - verify\_typ **Since: 0.036** `CODE ref` - subroutine (with 'typ' header parameter value passed as argument) should return `true` otherwise verification fails `Regexp ref` - 'typ' header parameter value has to match given regexp otherwise verification fails `Scalar` - 'typ' header parameter value has to be equal to given string `undef` (default) - do not verify 'typ' header parameter - tolerate\_padding **Since: 0.037** (semantics clarified **Since: 0.038**). Both modes accept tokens whose segments include trailing `=` Base64 padding characters (which are not produced by spec-compliant encoders); they differ only in what gets fed to the signature check. `0` (default) - strip `=` padding from each segment **before** computing the signature input. Compatible with the strict RFC 7515 producer (no padding signed). If the producer signed the _padded_ form, signature verification will fail in this mode. `1` - keep `=` padding as part of the signature input. Required to verify tokens produced by libraries (some Java implementations) that include padding in the bytes that were signed. ## encode\_jwt my $token = encode_jwt(%named_args); Returns the encoded JWT as a string - either compact serialization (the default; three or five `.`-separated segments) or flattened JSON serialization (when `serialization => 'flattened'`; a JSON object). Croaks on bad arguments or unsupported algorithm combinations. Named arguments: - payload Mandatory. Accepts a string (raw bytes), a HASH ref, or an ARRAY ref. HASH ref and ARRAY ref payloads are serialized as JSON strings; string payloads are passed through verbatim. my $token = encode_jwt(payload=>"any raw data", key=>$k, alg=>'HS256'); my $token = encode_jwt(payload=>{a=>1, b=>2}, key=>$k, alg=>'HS256'); my $token = encode_jwt(payload=>[11,22,33,44], key=>$k, alg=>'HS256'); - alg The 'alg' header value is mandatory for both JWE and JWS tokens. Supported JWE 'alg' algorithms: dir A128KW A192KW A256KW A128GCMKW A192GCMKW A256GCMKW PBES2-HS256+A128KW PBES2-HS384+A192KW PBES2-HS512+A256KW RSA-OAEP RSA-OAEP-256 RSA1_5 ECDH-ES+A128KW ECDH-ES+A192KW ECDH-ES+A256KW ECDH-ES Supported JWS algorithms: none ... no integrity (NOTE: disabled by default) HS256 ... HMAC+SHA256 integrity HS384 ... HMAC+SHA384 integrity HS512 ... HMAC+SHA512 integrity RS256 ... RSA+PKCS1-V1_5 + SHA256 signature RS384 ... RSA+PKCS1-V1_5 + SHA384 signature RS512 ... RSA+PKCS1-V1_5 + SHA512 signature PS256 ... RSA+PSS + SHA256 signature PS384 ... RSA+PSS + SHA384 signature PS512 ... RSA+PSS + SHA512 signature ES256 ... ECDSA + SHA256 signature ES256K ... ECDSA + SHA256 signature ES384 ... ECDSA + SHA384 signature ES512 ... ECDSA + SHA512 signature EdDSA ... Ed25519 signature - enc The 'enc' header is mandatory for JWE tokens. Supported 'enc' algorithms: A128GCM A192GCM A256GCM A128CBC-HS256 A192CBC-HS384 A256CBC-HS512 - key A key used for token encryption (JWE) or token signing (JWS). The value depends on `alg` token header value. JWS alg header key value ------------------ ---------------------------------- none no key required HS256 string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') HS384 same as HS256 HS512 same as HS256 RS256 private RSA key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, object: Crypt::PK::RSA, Crypt::OpenSSL::RSA, Crypt::X509 or Crypt::OpenSSL::X509 RS384 private RSA key, see RS256 RS512 private RSA key, see RS256 PS256 private RSA key, see RS256 PS384 private RSA key, see RS256 PS512 private RSA key, see RS256 ES256 private ECC key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, an instance of Crypt::PK::ECC ES256K private ECC key, see ES256 ES384 private ECC key, see ES256 ES512 private ECC key, see ES256 EdDSA private Ed25519 key JWE alg header key value ------------------ ---------------------------------- dir string (raw octets) or perl HASH ref with JWK, kty=>'oct', length depends on 'enc' algorithm A128KW string (raw octets) 16 bytes (or perl HASH ref with JWK, kty=>'oct') A192KW string (raw octets) 24 bytes (or perl HASH ref with JWK, kty=>'oct') A256KW string (raw octets) 32 bytes (or perl HASH ref with JWK, kty=>'oct') A128GCMKW string (raw octets) 16 bytes (or perl HASH ref with JWK, kty=>'oct') A192GCMKW string (raw octets) 24 bytes (or perl HASH ref with JWK, kty=>'oct') A256GCMKW string (raw octets) 32 bytes (or perl HASH ref with JWK, kty=>'oct') PBES2-HS256+A128KW string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') PBES2-HS384+A192KW string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') PBES2-HS512+A256KW string (raw octets) of any length (or perl HASH ref with JWK, kty=>'oct') RSA-OAEP public RSA key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, an instance of Crypt::PK::RSA or Crypt::OpenSSL::RSA RSA-OAEP-256 public RSA key, see RSA-OAEP RSA1_5 public RSA key, see RSA-OAEP ECDH-ES public ECC or X25519 key, perl HASH ref with JWK key structure, a reference to SCALAR string with PEM or DER or JSON/JWK data, an instance of Crypt::PK::ECC ECDH-ES+A128KW public ECC or X25519 key, see ECDH-ES ECDH-ES+A192KW public ECC or X25519 key, see ECDH-ES ECDH-ES+A256KW public ECC or X25519 key, see ECDH-ES - keypass Optional. When the `key` parameter is an encrypted private RSA or ECC key (PEM/DER), this parameter holds the password used to decrypt it. - allow\_none `1` - allow JWS with `none` 'alg' header value (which means that token has no signature), **BEWARE: DANGEROUS, INSECURE.** `0` (default) - do not allow JWS with `none` 'alg' header value - extra\_headers This optional parameter may contain a HASH ref with items that will be added to JWT header. If you want to use PBES2-based 'alg' like `PBES2-HS512+A256KW` you can set PBES2 salt len (p2s) in bytes and iteration count (p2c) via `extra_headers` like this: my $token = encode_jwt(payload=>$p, key=>$k, alg=>'PBES2-HS512+A256KW', extra_headers=>{p2c=>8000, p2s=>32}); #NOTE: handling of p2s header is a special case, in the end it is replaced with the generated salt You can also use this to specify a `kid` value (see ["kid\_keys"](#kid_keys)): my $token = encode_jwt(payload=>$p, key=>$k, alg=>'RS256', extra_headers=>{kid=>'key1'}); - unprotected\_headers A HASH ref with additional integrity-unprotected headers (JWS and JWE). Not available for `compact` serialization. - shared\_unprotected\_headers A HASH ref with additional integrity-unprotected headers (JWE only). Not available for `compact` serialization. - aad Additional Authenticated Data: a scalar of arbitrary bytes that is authenticated but not encrypted (JWE only). Not available for `compact` serialization. - serialization Specify serialization method: `compact` (default) for Compact JWS/JWE serialization or `flattened` for Flattened JWS/JWE JSON serialization. General JSON serialization is not supported yet. - zip Compression method, currently 'deflate' is the only one supported. `undef` (default) means no compression. my $token = encode_jwt(payload=>$p, key=>$k, alg=>'HS256', zip=>'deflate'); #or define compression level my $token = encode_jwt(payload=>$p, key=>$k, alg=>'HS256', zip=>['deflate', 9]); - auto\_iat `1` - set the `iat` (Issued At) claim to the current time (epoch seconds since 1970) at the moment of token encoding. `0` (default) - do not set the `iat` claim. **NOTE:** takes effect only when the `payload` argument is a HASH ref; silently ignored for string/ARRAY-ref payloads. Same applies to `relative_exp` and `relative_nbf`. - relative\_exp Set the `exp` (Expiration Time) claim to current time + `relative_exp` value (in seconds). See note under `auto_iat` about HASH-ref payloads. - relative\_nbf Set the `nbf` (Not Before) claim to current time + `relative_nbf` value (in seconds). See note under `auto_iat` about HASH-ref payloads. # SECURITY CONSIDERATIONS ## Configuration knobs The library exposes four tunable package variables. Set them once at program startup (typically in a `BEGIN` block) before any `encode_jwt`/`decode_jwt` call. - `$Crypt::JWT::MAX_PBES2_ITER` (default `3_000_000`) Maximum accepted PBES2 `p2c` (iteration count) on decode. Caps CPU time spent on PBKDF2 for an attacker-controlled token. **Since: 0.038** - `$Crypt::JWT::MAX_INFLATED_SIZE` (default `10 * 1024 * 1024`) Maximum size (in bytes) of a payload after `zip=DEF` inflation. Caps memory blow-up from "zip-bomb" tokens. **Since: 0.038** - `$Crypt::JWT::MIN_HMAC_KEY_LEN` (default `4`) Minimum HMAC key length (bytes) for HS256/384/512. See ["Key-strength minimums"](#key-strength-minimums) below for the rationale and recommended override values. **Since: 0.038** - `$Crypt::JWT::MIN_RSA_BITS` (default `2048`) Minimum RSA modulus size (bits). Applies to all RSA-based algorithms (RS256/384/512, PS256/384/512, RSA-OAEP, RSA-OAEP-256, RSA1\_5). **Since: 0.038** ## Key-strength minimums The library enforces the following minimums; tokens that try to sign or verify with weaker keys are rejected with a croak. Both knobs are package variables and can be tuned at startup if a deployer has a stricter or looser policy. - **HMAC keys for HS<n>:** minimum length **4 bytes** (overridable via `$Crypt::JWT::MIN_HMAC_KEY_LEN`). Applies to `encode_jwt` and `decode_jwt` on the HS256 / HS384 / HS512 paths. Tokens that try to sign or verify with a shorter key are rejected with a croak. **CAUTION:** this default is intentionally **much lower** than RFC 7518 section 3.2, which requires the key to be at least the size of the hash output (32 / 48 / 64 bytes for HS256 / HS384 / HS512). The 4-byte floor is a backward-compatibility compromise - the library has long accepted short keys and many existing deployments rely on that - that just blocks the most trivially weak keys (single characters, two-letter strings) while leaving the policy decision in the deployer's hands. Cryptographically, HMAC security is bounded by the entropy of the key: 16 random bytes (128 bits) is the smallest size that gives a comfortable security margin against brute-force key recovery; below that you start losing real security. - **RSA modulus size:** minimum **2048 bits** (overridable via `$Crypt::JWT::MIN_RSA_BITS`). Applies to RS256/384/512, PS256/384/512, RSA-OAEP, RSA-OAEP-256, and RSA1\_5 - both signing/encryption and verification/decryption. RSA keys with smaller moduli are rejected. This matches RFC 7518 section 3.3: "A key of size 2048 bits or larger MUST be used with these algorithms". # SEE ALSO [Crypt::Cipher::AES](https://metacpan.org/pod/Crypt%3A%3ACipher%3A%3AAES), [Crypt::AuthEnc::GCM](https://metacpan.org/pod/Crypt%3A%3AAuthEnc%3A%3AGCM), [Crypt::PK::RSA](https://metacpan.org/pod/Crypt%3A%3APK%3A%3ARSA), [Crypt::PK::ECC](https://metacpan.org/pod/Crypt%3A%3APK%3A%3AECC), [Crypt::KeyDerivation](https://metacpan.org/pod/Crypt%3A%3AKeyDerivation), [Crypt::KeyWrap](https://metacpan.org/pod/Crypt%3A%3AKeyWrap) # LICENSE This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. # COPYRIGHT Copyright (c) 2015-2026 DCIT, a.s. [https://www.dcit.cz](https://www.dcit.cz) / Karel Miko