JWT

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A ruby implementation of the RFC 7519 OAuth JSON Web Token (JWT) standard.

If you have further questions related to development or usage, join us: ruby-jwt google group.

See CHANGELOG.md for a complete set of changes.

Upcoming breaking changes

Notable changes in the upcoming version 3.0:

  • The indirect dependency to rbnacl will be removed:

    • Support for the non-standard SHA512256 algorithm will be removed.
    • Support for Ed25519 will be moved to a separate gem for better dependency handling.

  • Base64 decoding will no longer fallback on the looser RFC 2045.

  • Claim verification has been split into separate classes and has a new api and lead to the following deprecations:

    • The ::JWT::ClaimsValidator class will be removed in favor of the functionality provided by ::JWT::Claims.
    • The ::JWT::Claims::verify! method will be removed in favor of ::JWT::Claims::verify_payload!.
    • The ::JWT::JWA.create method will be removed.
    • The ::JWT::Verify class will be removed in favor of the functionality provided by ::JWT::Claims.
    • Calling ::JWT::Claims::Numeric.new with a payload will be removed in favor of ::JWT::Claims::verify_payload!(payload, :numeric).
    • Calling ::JWT::Claims::Numeric.verify! with a payload will be removed in favor of ::JWT::Claims::verify_payload!(payload, :numeric).

  • The internal algorithms were restructured to support extensions from separate libraries. The changes lead to a few deprecations and new requirements:

    • The sign and verify static methods on all the algorithms (::JWT::JWA) will be removed.
    • Custom algorithms are expected to include the JWT::JWA::SigningAlgorithm module.

Sponsors

Logo Message
auth0 logo If you want to quickly add secure token-based authentication to Ruby projects, feel free to check Auth0's Ruby SDK and free plan at auth0.com/developers

Installing

Using Rubygems:

gem install jwt

Using Bundler:

Add the following to your Gemfile

gem 'jwt'

And run bundle install

Finally require the gem in your application

require 'jwt'

Algorithms and Usage

The jwt gem natively supports the NONE, HMAC, RSASSA, ECDSA and RSASSA-PSS algorithms via the openssl library. The gem can be extended with additional or alternative implementations of the algorithms via extensions.

Additionally the EdDSA algorithm is supported via a separate gem.

For safe cryptographic signing, you need to specify the algorithm in the options hash whenever you call JWT.decode to ensure that an attacker cannot bypass the algorithm verification step. It is strongly recommended that you hard code the algorithm, as you may leave yourself vulnerable by dynamically picking the algorithm

See: JSON Web Algorithms (JWA) 3.1. "alg" (Algorithm) Header Parameter Values for JWS

Deprecation warnings

Deprecation warnings are logged once (:once option) by default to avoid spam in logs. Other options are :silent to completely silence warnings and :warn to log every time a deprecated path is executed.

  JWT.configuration.deprecation_warnings = :warn # default is :once

Base64 decoding

In the past the gem has been supporting the Base64 decoding specified in RFC2045 allowing newlines and blanks in the base64 encoded payload. In future versions base64 decoding will be stricter and only comply to RFC4648.

The stricter base64 decoding when processing tokens can be done via the strict_base64_decoding configuration accessor.

  JWT.configuration.strict_base64_decoding = true # default is false

NONE

  • none - unsigned token

payload = { data: 'test' }

# IMPORTANT: set nil as password parameter
token = JWT.encode(payload, nil, 'none')

# eyJhbGciOiJub25lIn0.eyJkYXRhIjoidGVzdCJ9.
puts token

# Set password to nil and validation to false otherwise this won't work
decoded_token = JWT.decode(token, nil, false)

# Array
# [
#   {"data"=>"test"}, # payload
#   {"alg"=>"none"} # header
# ]
puts decoded_token

HMAC

  • HS256 - HMAC using SHA-256 hash algorithm
  • HS384 - HMAC using SHA-384 hash algorithm
  • HS512 - HMAC using SHA-512 hash algorithm
# The secret must be a string. With OpenSSL 3.0/openssl gem `<3.0.1`, JWT::DecodeError will be raised if it isn't provided.
hmac_secret = 'my$ecretK3y'

token = JWT.encode(payload, hmac_secret, 'HS256')

# eyJhbGciOiJIUzI1NiJ9.eyJkYXRhIjoidGVzdCJ9.pNIWIL34Jo13LViZAJACzK6Yf0qnvT_BuwOxiMCPE-Y
puts token

decoded_token = JWT.decode(token, hmac_secret, true, { algorithm: 'HS256' })

# Array
# [
#   {"data"=>"test"}, # payload
#   {"alg"=>"HS256"} # header
# ]
puts decoded_token

RSA

  • RS256 - RSA using SHA-256 hash algorithm
  • RS384 - RSA using SHA-384 hash algorithm
  • RS512 - RSA using SHA-512 hash algorithm
rsa_private = OpenSSL::PKey::RSA.generate(2048)
rsa_public = rsa_private.public_key

token = JWT.encode(payload, rsa_private, 'RS256')

# eyJhbGciOiJSUzI1NiJ9.eyJkYXRhIjoidGVzdCJ9.GplO4w1spRgvEJQ3-FOtZr-uC8L45Jt7SN0J4woBnEXG_OZBSNcZjAJWpjadVYEe2ev3oUBFDYM1N_-0BTVeFGGYvMewu8E6aMjSZvOpf1cZBew-Vt4poSq7goG2YRI_zNPt3af2lkPqXD796IKC5URrEvcgF5xFQ-6h07XRDpSRx1ECrNsUOt7UM3l1IB4doY11GzwQA5sHDTmUZ0-kBT76ZMf12Srg_N3hZwphxBtudYtN5VGZn420sVrQMdPE_7Ni3EiWT88j7WCr1xrF60l8sZT3yKCVleG7D2BEXacTntB7GktBv4Xo8OKnpwpqTpIlC05dMowMkz3rEAAYbQ
puts token

decoded_token = JWT.decode(token, rsa_public, true, { algorithm: 'RS256' })

# Array
# [
#   {"data"=>"test"}, # payload
#   {"alg"=>"RS256"} # header
# ]
puts decoded_token

ECDSA

  • ES256 - ECDSA using P-256 and SHA-256
  • ES384 - ECDSA using P-384 and SHA-384
  • ES512 - ECDSA using P-521 and SHA-512
  • ES256K - ECDSA using P-256K and SHA-256
ecdsa_key = OpenSSL::PKey::EC.generate('prime256v1')

token = JWT.encode(payload, ecdsa_key, 'ES256')

# eyJhbGciOiJFUzI1NiJ9.eyJkYXRhIjoidGVzdCJ9.AlLW--kaF7EX1NMX9WJRuIW8NeRJbn2BLXHns7Q5TZr7Hy3lF6MOpMlp7GoxBFRLISQ6KrD0CJOrR8aogEsPeg
puts token

decoded_token = JWT.decode(token, ecdsa_key, true, { algorithm: 'ES256' })

# Array
# [
#    {"test"=>"data"}, # payload
#    {"alg"=>"ES256"} # header
# ]
puts decoded_token

EDDSA

In order to use this algorithm you need to add the RbNaCl gem to you Gemfile.

gem 'rbnacl'

For more detailed installation instruction check the official repository on GitHub.

  • ED25519
private_key = RbNaCl::Signatures::Ed25519::SigningKey.new('abcdefghijklmnopqrstuvwxyzABCDEF')
public_key = private_key.verify_key
token = JWT.encode payload, private_key, 'ED25519'

# eyJhbGciOiJFRDI1NTE5In0.eyJkYXRhIjoidGVzdCJ9.6xIztXyOupskddGA_RvKU76V9b2dCQUYhoZEVFnRimJoPYIzZ2Fm47CWw8k2NTCNpgfAuxg9OXjaiVK7MvrbCQ
puts token

decoded_token = JWT.decode token, public_key, true, { algorithm: 'ED25519' }
# Array
# [
#  {"test"=>"data"}, # payload
#  {"alg"=>"ED25519"} # header
# ]

RSASSA-PSS

In order to use this algorithm you need to add the openssl gem to your Gemfile with a version greater or equal to 2.1.

gem 'openssl', '~> 2.1'
  • PS256 - RSASSA-PSS using SHA-256 hash algorithm
  • PS384 - RSASSA-PSS using SHA-384 hash algorithm
  • PS512 - RSASSA-PSS using SHA-512 hash algorithm
rsa_private = OpenSSL::PKey::RSA.generate 2048
rsa_public = rsa_private.public_key

token = JWT.encode(payload, rsa_private, 'PS256')

# eyJhbGciOiJQUzI1NiJ9.eyJkYXRhIjoidGVzdCJ9.KEmqagMUHM-NcmXo6818ZazVTIAkn9qU9KQFT1c5Iq91n0KRpAI84jj4ZCdkysDlWokFs3Dmn4MhcXP03oJKLFgnoPL40_Wgg9iFr0jnIVvnMUp1kp2RFUbL0jqExGTRA3LdAhuvw6ZByGD1bkcWjDXygjQw-hxILrT1bENjdr0JhFd-cB0-ps5SB0mwhFNcUw-OM3Uu30B1-mlFaelUY8jHJYKwLTZPNxHzndt8RGXF8iZLp7dGb06HSCKMcVzhASGMH4ZdFystRe2hh31cwcvnl-Eo_D4cdwmpN3Abhk_8rkxawQJR3duh8HNKc4AyFPo7SabEaSu2gLnLfN3yfg
puts token

decoded_token = JWT.decode(token, rsa_public, true, { algorithm: 'PS256' })

# Array
# [
#   {"data"=>"test"}, # payload
#   {"alg"=>"PS256"} # header
# ]
puts decoded_token

Add custom header fields

Ruby-jwt gem supports custom header fields To add custom header fields you need to pass header_fields parameter

token = JWT.encode(payload, key, algorithm='HS256', header_fields={})

Example:


payload = { data: 'test' }

# IMPORTANT: set nil as password parameter
token = JWT.encode(payload, nil, 'none', { typ: 'JWT' })

# eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0.eyJkYXRhIjoidGVzdCJ9.
puts token

# Set password to nil and validation to false otherwise this won't work
decoded_token = JWT.decode(token, nil, false)

# Array
# [
#   {"data"=>"test"}, # payload
#   {"typ"=>"JWT", "alg"=>"none"} # header
# ]
puts decoded_token

Custom algorithms

When encoding or decoding a token, you can pass in a custom object through the algorithm option to handle signing or verification. This custom object must include or extend the JWT::JWA::SigningAlgorithm module and implement certain methods:

  • For decoding/verifying: The object must implement the methods alg and verify.
  • For encoding/signing: The object must implement the methods alg and sign.

For customization options check the details from JWT::JWA::SigningAlgorithm.

module CustomHS512Algorithm
  extend JWT::JWA::SigningAlgorithm

  def self.alg
    'HS512'
  end

  def self.sign(data:, signing_key:)
    OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha512'), signing_key, data)
  end

  def self.verify(data:, signature:, verification_key:)
    ::OpenSSL.secure_compare(sign(data: data, signing_key: verification_key), signature)
  end
end

token = ::JWT.encode({'pay' => 'load'}, 'secret', CustomHS512Algorithm)
payload, header = ::JWT.decode(token, 'secret', true, algorithm: CustomHS512Algorithm)

JWT::Token and JWT::EncodedToken

The JWT::Token and JWT::EncodedToken classes can be used to manage your JWTs.

token = JWT::Token.new(payload: { exp: Time.now.to_i + 60, jti: '1234', sub: "my-subject" }, header: { kid: 'hmac' })
token.sign!(algorithm: 'HS256', key: "secret")

token.jwt # => "eyJhbGciOiJIUzI1N..."

The JWT::EncodedToken can be used to create a token object that allows verification of signatures and claims

encoded_token = JWT::EncodedToken.new(token.jwt)

encoded_token.verify_signature!(algorithm: 'HS256', key: "secret")
encoded_token.verify_signature!(algorithm: 'HS256', key: "wrong_secret") # raises JWT::VerificationError
encoded_token.verify_claims!(:exp, :jti)
encoded_token.verify_claims!(sub: ["not-my-subject"]) # raises JWT::InvalidSubError
encoded_token.claim_errors(sub: ["not-my-subject"]).map(&:message) # => ["Invalid subject. Expected [\"not-my-subject\"], received my-subject"]
encoded_token.payload # => { 'exp'=>1234, 'jti'=>'1234", 'sub'=>'my-subject' }
encoded_token.header # {'kid'=>'hmac', 'alg'=>'HS256'}

Detached payload

The ::JWT::Token#detach_payload! method can be use to detach the payload from the JWT.

token = JWT::Token.new(payload: { pay: 'load' })
token.sign!(algorithm: 'HS256', key: "secret")
token.detach_payload!
token.jwt # => "eyJhbGciOiJIUzI1NiJ9..UEhDY1Qlj29ammxuVRA_-gBah4qTy5FngIWg0yEAlC0"
token.encoded_payload # => "eyJwYXkiOiJsb2FkIn0"

The JWT::EncodedToken class can be used to decode a token with a detached payload by providing the payload to the token instance in separate.

encoded_token = JWT::EncodedToken.new(token.jwt)
encoded_token.encoded_payload = "eyJwYXkiOiJsb2FkIn0"
encoded_token.verify_signature!(algorithm: 'HS256', key: "secret")
encoded_token.payload # => {"pay"=>"load"}

Claims

JSON Web Token defines some reserved claim names and defines how they should be used. JWT supports these reserved claim names:

  • 'exp' (Expiration Time) Claim
  • 'nbf' (Not Before Time) Claim
  • 'iss' (Issuer) Claim
  • 'aud' (Audience) Claim
  • 'jti' (JWT ID) Claim
  • 'iat' (Issued At) Claim
  • 'sub' (Subject) Claim

Expiration Time Claim

From Oauth JSON Web Token 4.1.4. "exp" (Expiration Time) Claim:

The exp (expiration time) claim identifies the expiration time on or after which the JWT MUST NOT be accepted for processing. The processing of the exp claim requires that the current date/time MUST be before the expiration date/time listed in the exp claim. Implementers MAY provide for some small leeway, usually no more than a few minutes, to account for clock skew. Its value MUST be a number containing a NumericDate value. Use of this claim is OPTIONAL.

Handle Expiration Claim

exp = Time.now.to_i + 4 * 3600
exp_payload = { data: 'data', exp: exp }

token = JWT.encode(exp_payload, hmac_secret, 'HS256')

begin
  decoded_token = JWT.decode(token, hmac_secret, true, { algorithm: 'HS256' })
rescue JWT::ExpiredSignature
  # Handle expired token, e.g. logout user or deny access
end

The Expiration Claim verification can be disabled.

# Decode token without raising JWT::ExpiredSignature error
JWT.decode(token, hmac_secret, true, { verify_expiration: false, algorithm: 'HS256' })

Adding Leeway

exp = Time.now.to_i - 10
leeway = 30 # seconds

exp_payload = { data: 'data', exp: exp }

# build expired token
token = JWT.encode(exp_payload, hmac_secret, 'HS256')

begin
  # add leeway to ensure the token is still accepted
  decoded_token = JWT.decode(token, hmac_secret, true, { exp_leeway: leeway, algorithm: 'HS256' })
rescue JWT::ExpiredSignature
  # Handle expired token, e.g. logout user or deny access
end

Not Before Time Claim

From Oauth JSON Web Token 4.1.5. "nbf" (Not Before) Claim:

The nbf (not before) claim identifies the time before which the JWT MUST NOT be accepted for processing. The processing of the nbf claim requires that the current date/time MUST be after or equal to the not-before date/time listed in the nbf claim. Implementers MAY provide for some small leeway, usually no more than a few minutes, to account for clock skew. Its value MUST be a number containing a NumericDate value. Use of this claim is OPTIONAL.

Handle Not Before Claim

nbf = Time.now.to_i - 3600
nbf_payload = { data: 'data', nbf: nbf }

token = JWT.encode(nbf_payload, hmac_secret, 'HS256')

begin
  decoded_token = JWT.decode(token, hmac_secret, true, { algorithm: 'HS256' })
rescue JWT::ImmatureSignature
  # Handle invalid token, e.g. logout user or deny access
end

The Not Before Claim verification can be disabled.

# Decode token without raising JWT::ImmatureSignature error
JWT.decode(token, hmac_secret, true, { verify_not_before: false, algorithm: 'HS256' })

Adding Leeway

nbf = Time.now.to_i + 10
leeway = 30

nbf_payload = { data: 'data', nbf: nbf }

# build expired token
token = JWT.encode(nbf_payload, hmac_secret, 'HS256')

begin
  # add leeway to ensure the token is valid
  decoded_token = JWT.decode(token, hmac_secret, true, { nbf_leeway: leeway, algorithm: 'HS256' })
rescue JWT::ImmatureSignature
  # Handle invalid token, e.g. logout user or deny access
end

Issuer Claim

From Oauth JSON Web Token 4.1.1. "iss" (Issuer) Claim:

The iss (issuer) claim identifies the principal that issued the JWT. The processing of this claim is generally application specific. The iss value is a case-sensitive string containing a StringOrURI value. Use of this claim is OPTIONAL.

You can pass multiple allowed issuers as an Array, verification will pass if one of them matches the iss value in the payload.

iss = 'My Awesome Company Inc. or https://my.awesome.website/'
iss_payload = { data: 'data', iss: iss }

token = JWT.encode(iss_payload, hmac_secret, 'HS256')

begin
  # Add iss to the validation to check if the token has been manipulated
  decoded_token = JWT.decode(token, hmac_secret, true, { iss: iss, verify_iss: true, algorithm: 'HS256' })
rescue JWT::InvalidIssuerError
  # Handle invalid token, e.g. logout user or deny access
end

You can also pass a Regexp or Proc (with arity 1), verification will pass if the regexp matches or the proc returns truthy. On supported ruby versions (>= 2.5) you can also delegate to methods, on older versions you will have to convert them to proc (using to_proc)

JWT.decode(token, hmac_secret, true,
           iss: %r'https://my.awesome.website/',
           verify_iss: true,
           algorithm: 'HS256')

JWT.decode(token, hmac_secret, true,
           iss: ->(issuer) { issuer.start_with?('My Awesome Company Inc') },
           verify_iss: true,
           algorithm: 'HS256')

JWT.decode(token, hmac_secret, true,
           iss: method(:valid_issuer?),
           verify_iss: true,
           algorithm: 'HS256')

# somewhere in the same class:
def valid_issuer?(issuer)
  # custom validation
end

Audience Claim

From Oauth JSON Web Token 4.1.3. "aud" (Audience) Claim:

The aud (audience) claim identifies the recipients that the JWT is intended for. Each principal intended to process the JWT MUST identify itself with a value in the audience claim. If the principal processing the claim does not identify itself with a value in the aud claim when this claim is present, then the JWT MUST be rejected. In the general case, the aud value is an array of case-sensitive strings, each containing a StringOrURI value. In the special case when the JWT has one audience, the aud value MAY be a single case-sensitive string containing a StringOrURI value. The interpretation of audience values is generally application specific. Use of this claim is OPTIONAL.

aud = ['Young', 'Old']
aud_payload = { data: 'data', aud: aud }

token = JWT.encode(aud_payload, hmac_secret, 'HS256')

begin
  # Add aud to the validation to check if the token has been manipulated
  decoded_token = JWT.decode(token, hmac_secret, true, { aud: aud, verify_aud: true, algorithm: 'HS256' })
rescue JWT::InvalidAudError
  # Handle invalid token, e.g. logout user or deny access
  puts 'Audience Error'
end

JWT ID Claim

From Oauth JSON Web Token 4.1.7. "jti" (JWT ID) Claim:

The jti (JWT ID) claim provides a unique identifier for the JWT. The identifier value MUST be assigned in a manner that ensures that there is a negligible probability that the same value will be accidentally assigned to a different data object; if the application uses multiple issuers, collisions MUST be prevented among values produced by different issuers as well. The jti claim can be used to prevent the JWT from being replayed. The jti value is a case-sensitive string. Use of this claim is OPTIONAL.

# Use the secret and iat to create a unique key per request to prevent replay attacks
jti_raw = [hmac_secret, iat].join(':').to_s
jti = Digest::MD5.hexdigest(jti_raw)
jti_payload = { data: 'data', iat: iat, jti: jti }

token = JWT.encode(jti_payload, hmac_secret, 'HS256')

begin
  # If :verify_jti is true, validation will pass if a JTI is present
  #decoded_token = JWT.decode(token, hmac_secret, true, { verify_jti: true, algorithm: 'HS256' })
  # Alternatively, pass a proc with your own code to check if the JTI has already been used
  decoded_token = JWT.decode(token, hmac_secret, true, { verify_jti: proc { |jti| my_validation_method(jti) }, algorithm: 'HS256' })
  # or
  decoded_token = JWT.decode(token, hmac_secret, true, { verify_jti: proc { |jti, payload| my_validation_method(jti, payload) }, algorithm: 'HS256' })
rescue JWT::InvalidJtiError
  # Handle invalid token, e.g. logout user or deny access
  puts 'Error'
end

Issued At Claim

From Oauth JSON Web Token 4.1.6. "iat" (Issued At) Claim:

The iat (issued at) claim identifies the time at which the JWT was issued. This claim can be used to determine the age of the JWT. The leeway option is not taken into account when verifying this claim. The iat_leeway option was removed in version 2.2.0. Its value MUST be a number containing a NumericDate value. Use of this claim is OPTIONAL.

Handle Issued At Claim

iat = Time.now.to_i
iat_payload = { data: 'data', iat: iat }

token = JWT.encode(iat_payload, hmac_secret, 'HS256')

begin
  # Add iat to the validation to check if the token has been manipulated
  decoded_token = JWT.decode(token, hmac_secret, true, { verify_iat: true, algorithm: 'HS256' })
rescue JWT::InvalidIatError
  # Handle invalid token, e.g. logout user or deny access
end

Subject Claim

From Oauth JSON Web Token 4.1.2. "sub" (Subject) Claim:

The sub (subject) claim identifies the principal that is the subject of the JWT. The Claims in a JWT are normally statements about the subject. The subject value MUST either be scoped to be locally unique in the context of the issuer or be globally unique. The processing of this claim is generally application specific. The sub value is a case-sensitive string containing a StringOrURI value. Use of this claim is OPTIONAL.

sub = 'Subject'
sub_payload = { data: 'data', sub: sub }

token = JWT.encode(sub_payload, hmac_secret, 'HS256')

begin
  # Add sub to the validation to check if the token has been manipulated
  decoded_token = JWT.decode(token, hmac_secret, true, { sub: sub, verify_sub: true, algorithm: 'HS256' })
rescue JWT::InvalidSubError
  # Handle invalid token, e.g. logout user or deny access
end

Standalone claim verification

The JWT claim verifications can be used to verify any Hash to include expected keys and values.

A few example on verifying the claims for a payload:

JWT::Claims.verify_payload!({"exp" => Time.now.to_i + 10}, :numeric, :exp)
JWT::Claims.valid_payload?({"exp" => Time.now.to_i + 10}, :exp)
# => true
JWT::Claims.payload_errors({"exp" => Time.now.to_i - 10}, :exp)
# => [#<struct JWT::Claims::Error message="Signature has expired">]
JWT::Claims.verify_payload!({"exp" => Time.now.to_i - 10}, exp: { leeway: 11})

JWT::Claims.verify_payload!({"exp" => Time.now.to_i + 10, "sub" => "subject"}, :exp, sub: "subject")

Finding a Key

To dynamically find the key for verifying the JWT signature, pass a block to the decode block. The block receives headers and the original payload as parameters. It should return with the key to verify the signature that was used to sign the JWT.

issuers = %w[My_Awesome_Company1 My_Awesome_Company2]
iss_payload = { data: 'data', iss: issuers.first }

secrets = { issuers.first => hmac_secret, issuers.last => 'hmac_secret2' }

token = JWT.encode(iss_payload, hmac_secret, 'HS256')

begin
  # Add iss to the validation to check if the token has been manipulated
  decoded_token = JWT.decode(token, nil, true, { iss: issuers, verify_iss: true, algorithm: 'HS256' }) do |_headers, payload|
    secrets[payload['iss']]
  end
rescue JWT::InvalidIssuerError
  # Handle invalid token, e.g. logout user or deny access
end

Required Claims

You can specify claims that must be present for decoding to be successful. JWT::MissingRequiredClaim will be raised if any are missing

# Will raise a JWT::MissingRequiredClaim error if the 'exp' claim is absent
JWT.decode(token, hmac_secret, true, { required_claims: ['exp'], algorithm: 'HS256' })

X.509 certificates in x5c header

A JWT signature can be verified using certificate(s) given in the x5c header. Before doing that, the trustworthiness of these certificate(s) must be established. This is done in accordance with RFC 5280 which (among other things) verifies the certificate(s) are issued by a trusted root certificate, the timestamps are valid, and none of the certificate(s) are revoked (i.e. being present in the root certificate's Certificate Revocation List).

root_certificates = [] # trusted `OpenSSL::X509::Certificate` objects
crl_uris = root_certificates.map(&:crl_uris)
crls = crl_uris.map do |uri|
  # look up cached CRL by `uri` and return it if found, otherwise continue
  crl = Net::HTTP.get(uri)
  crl = OpenSSL::X509::CRL.new(crl)
  # cache `crl` using `uri` as the key, expiry set to `crl.next_update` timestamp
end

begin
  JWT.decode(token, nil, true, { x5c: { root_certificates: root_certificates, crls: crls } })
rescue JWT::DecodeError
  # Handle error, e.g. x5c header certificate revoked or expired
end

JSON Web Key (JWK)

JWK is a JSON structure representing a cryptographic key. This gem currently supports RSA, EC, OKP and HMAC keys. OKP support requires RbNaCl and currently only supports the Ed25519 curve.

To encode a JWT using your JWK:

optional_parameters = { kid: 'my-kid', use: 'sig', alg: 'RS512' }
jwk = JWT::JWK.new(OpenSSL::PKey::RSA.new(2048), optional_parameters)

# Encoding
payload = { data: 'data' }
token = JWT.encode(payload, jwk.signing_key, jwk[:alg], kid: jwk[:kid])

# JSON Web Key Set for advertising your signing keys
jwks_hash = JWT::JWK::Set.new(jwk).export

To decode a JWT using a trusted entity's JSON Web Key Set (JWKS):

jwks = JWT::JWK::Set.new(jwks_hash)
jwks.filter! {|key| key[:use] == 'sig' } # Signing keys only!
algorithms = jwks.map { |key| key[:alg] }.compact.uniq
JWT.decode(token, nil, true, algorithms: algorithms, jwks: jwks)

The jwks option can also be given as a lambda that evaluates every time a kid is resolved. This can be used to implement caching of remotely fetched JWK Sets.

If the requested kid is not found from the given set the loader will be called a second time with the kid_not_found option set to true. The application can choose to implement some kind of JWK cache invalidation or other mechanism to handle such cases.

Tokens without a specified kid are rejected by default. This behaviour may be overwritten by setting the allow_nil_kid option for decode to true.

jwks_loader = ->(options) do
  # The jwk loader would fetch the set of JWKs from a trusted source.
  # To avoid malicious requests triggering cache invalidations there needs to be
  # some kind of grace time or other logic for determining the validity of the invalidation.
  # This example only allows cache invalidations every 5 minutes.
  if options[:kid_not_found] && @cache_last_update < Time.now.to_i - 300
    logger.info("Invalidating JWK cache. #{options[:kid]} not found from previous cache")
    @cached_keys = nil
  end
  @cached_keys ||= begin
    @cache_last_update = Time.now.to_i
    # Replace with your own JWKS fetching routine
    jwks = JWT::JWK::Set.new(jwks_hash)
    jwks.select! { |key| key[:use] == 'sig' } # Signing Keys only
    jwks
  end
end

begin
  JWT.decode(token, nil, true, { algorithms: ['RS512'], jwks: jwks_loader })
rescue JWT::JWKError
  # Handle problems with the provided JWKs
rescue JWT::DecodeError
  # Handle other decode related issues e.g. no kid in header, no matching public key found etc.
end

Importing and exporting JSON Web Keys

The ::JWT::JWK class can be used to import both JSON Web Keys and OpenSSL keys and export to either format with and without the private key included.

To include the private key in the export pass the include_private parameter to the export method.

# Import a JWK Hash (showing an HMAC example)
jwk = JWT::JWK.new({ kty: 'oct', k: 'my-secret', kid: 'my-kid' })

# Import an OpenSSL key
# You can optionally add descriptive parameters to the JWK
desc_params = { kid: 'my-kid', use: 'sig' }
jwk = JWT::JWK.new(OpenSSL::PKey::RSA.new(2048), desc_params)

# Export as JWK Hash (public key only by default)
jwk_hash = jwk.export
jwk_hash_with_private_key = jwk.export(include_private: true)

# Export as OpenSSL key
public_key = jwk.verify_key
private_key = jwk.signing_key if jwk.private?

# You can also import and export entire JSON Web Key Sets
jwks_hash = { keys: [{ kty: 'oct', k: 'my-secret', kid: 'my-kid' }] }
jwks = JWT::JWK::Set.new(jwks_hash)
jwks_hash = jwks.export

Key ID (kid) and JWKs

The key id (kid) generation in the gem is a custom algorithm and not based on any standards. To use a standardized JWK thumbprint (RFC 7638) as the kid for JWKs a generator type can be specified in the global configuration or can be given to the JWK instance on initialization.

JWT.configuration.jwk.kid_generator_type = :rfc7638_thumbprint
# OR
JWT.configuration.jwk.kid_generator = ::JWT::JWK::Thumbprint
# OR
jwk = JWT::JWK.new(OpenSSL::PKey::RSA.new(2048), nil, kid_generator: ::JWT::JWK::Thumbprint)

jwk_hash = jwk.export

thumbprint_as_the_kid = jwk_hash[:kid]

Development and testing

The tests are written with rspec. Appraisal is used to ensure compatibility with 3rd party dependencies providing cryptographic features.

bundle install
bundle exec appraisal rake test

Releasing

To cut a new release adjust the version.rb and CHANGELOG with desired version numbers and dates and commit the changes. Tag the release with the version number using the following command:

rake release:source_control_push

This will tag a new version an trigger a GitHub action that eventually will push the gem to rubygems.org.

How to contribute

See CONTRIBUTING.

Contributors

See AUTHORS.

License

See LICENSE.