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jwt.py
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jwt.py
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import binascii
import json
from calendar import timegm
from collections import Mapping
from datetime import datetime
from datetime import timedelta
from six import string_types
from jose import jws
from .exceptions import JWSError
from .exceptions import JWTClaimsError
from .exceptions import JWTError
from .exceptions import ExpiredSignatureError
from .utils import timedelta_total_seconds
def encode(claims, key, algorithm=None, headers=None):
"""Encodes a claims set and returns a JWT string.
JWTs are JWS signed objects with a few reserved claims.
Args:
claims (dict): A claims set to sign
key (str): The key to use for signing the claim set
algorithm (str, optional): The algorithm to use for signing the
the claims. Defaults to HS256.
headers (dict, optional): A set of headers that will be added to
the default headers. Any headers that are added as additional
headers will override the default headers.
Returns:
str: The string representation of the header, claims, and signature.
Raises:
JWTError: If there is an error encoding the claims.
Examples:
>>> jwt.encode({'a': 'b'}, 'secret', algorithm='HS256')
'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJhIjoiYiJ9.jiMyrsmD8AoHWeQgmxZ5yq8z0lXS67_QGs52AzC8Ru8'
"""
for time_claim in ['exp', 'iat', 'nbf']:
# Convert datetime to a intDate value in known time-format claims
if isinstance(claims.get(time_claim), datetime):
claims[time_claim] = timegm(claims[time_claim].utctimetuple())
if algorithm:
return jws.sign(claims, key, headers=headers, algorithm=algorithm)
return jws.sign(claims, key, headers=headers)
def decode(token, key, algorithms=None, options=None, audience=None, issuer=None):
"""Verifies a JWT string's signature and validates reserved claims.
Args:
token (str): A signed JWS to be verified.
key (str): A key to attempt to verify the payload with.
algorithms (str or list): Valid algorithms that should be used to verify the JWS.
audience (str): The intended audience of the token. If the "aud" claim is
included in the claim set, then the audience must be included and must equal
the provided claim.
issuer (str): The issuer of the token. If the "iss" claim is
included in the claim set, then the issuer must be included and must equal
the provided claim.
options (dict): A dictionary of options for skipping validation steps.
defaults = {
'verify_signature': True,
'verify_aud': True,
'verify_iat': True,
'verify_exp': True,
'verify_nbf': True,
'verify_iss': True,
'verify_sub': True,
'verify_jti': True,
'leeway': 0,
}
Returns:
dict: The dict representation of the claims set, assuming the signature is valid
and all requested data validation passes.
Raises:
JWTError: If the signature is invalid in any way.
Examples:
>>> payload = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJhIjoiYiJ9.jiMyrsmD8AoHWeQgmxZ5yq8z0lXS67_QGs52AzC8Ru8'
>>> jwt.decode(payload, 'secret', algorithms='HS256')
"""
defaults = {
'verify_signature': True,
'verify_aud': True,
'verify_iat': True,
'verify_exp': True,
'verify_nbf': True,
'verify_iss': True,
'verify_sub': True,
'verify_jti': True,
'leeway': 0,
}
if options:
defaults.update(options)
verify_signature = defaults.get('verify_signature', True)
try:
payload = jws.verify(token, key, algorithms, verify=verify_signature)
except JWSError as e:
raise JWTError(e)
try:
claims = json.loads(payload.decode('utf-8'))
except ValueError as e:
raise JWTError('Invalid payload string: %s' % e)
if not isinstance(claims, Mapping):
raise JWTError('Invalid payload string: must be a json object')
_validate_claims(claims, audience=audience, issuer=issuer, options=defaults)
return claims
def get_unverified_header(token):
"""Returns the decoded headers without verification of any kind.
Args:
token (str): A signed JWT to decode the headers from.
Returns:
dict: The dict representation of the token headers.
Raises:
JWTError: If there is an exception decoding the token.
"""
try:
headers = jws.get_unverified_headers(token)
except:
raise JWTError('Error decoding token headers.')
return headers
def get_unverified_headers(token):
"""Returns the decoded headers without verification of any kind.
This is simply a wrapper of get_unverified_header() for backwards
compatibility.
Args:
token (str): A signed JWT to decode the headers from.
Returns:
dict: The dict representation of the token headers.
Raises:
JWTError: If there is an exception decoding the token.
"""
return get_unverified_header(token)
def get_unverified_claims(token):
"""Returns the decoded claims without verification of any kind.
Args:
token (str): A signed JWT to decode the headers from.
Returns:
dict: The dict representation of the token claims.
Raises:
JWTError: If there is an exception decoding the token.
"""
try:
claims = jws.get_unverified_claims(token)
except:
raise JWTError('Error decoding token claims.')
return claims
def _validate_iat(claims):
"""Validates that the 'iat' claim is valid.
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. Its
value MUST be a number containing a NumericDate value. Use of this
claim is OPTIONAL.
Args:
claims (dict): The claims dictionary to validate.
"""
if 'iat' not in claims:
return
try:
int(claims['iat'])
except ValueError:
raise JWTClaimsError('Issued At claim (iat) must be an integer.')
def _validate_nbf(claims, leeway=0):
"""Validates that the 'nbf' claim is valid.
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.
Args:
claims (dict): The claims dictionary to validate.
leeway (int): The number of seconds of skew that is allowed.
"""
if 'nbf' not in claims:
return
try:
nbf = int(claims['nbf'])
except ValueError:
raise JWTClaimsError('Not Before claim (nbf) must be an integer.')
now = timegm(datetime.utcnow().utctimetuple())
if nbf > (now + leeway):
raise JWTClaimsError('The token is not yet valid (nbf)')
def _validate_exp(claims, leeway=0):
"""Validates that the 'exp' claim is valid.
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.
Args:
claims (dict): The claims dictionary to validate.
leeway (int): The number of seconds of skew that is allowed.
"""
if 'exp' not in claims:
return
try:
exp = int(claims['exp'])
except ValueError:
raise JWTClaimsError('Expiration Time claim (exp) must be an integer.')
now = timegm(datetime.utcnow().utctimetuple())
if exp < (now - leeway):
raise ExpiredSignatureError('Signature has expired.')
def _validate_aud(claims, audience=None):
"""Validates that the 'aud' claim is valid.
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.
Args:
claims (dict): The claims dictionary to validate.
audience (str): The audience that is verifying the token.
"""
if 'aud' not in claims:
# if audience:
# raise JWTError('Audience claim expected, but not in claims')
return
audience_claims = claims['aud']
if isinstance(audience_claims, string_types):
audience_claims = [audience_claims]
if not isinstance(audience_claims, list):
raise JWTClaimsError('Invalid claim format in token')
if any(not isinstance(c, string_types) for c in audience_claims):
raise JWTClaimsError('Invalid claim format in token')
if audience not in audience_claims:
raise JWTClaimsError('Invalid audience')
def _validate_iss(claims, issuer=None):
"""Validates that the 'iss' claim is valid.
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.
Args:
claims (dict): The claims dictionary to validate.
issuer (str): The issuer that sent the token.
"""
if issuer is not None:
if claims.get('iss') != issuer:
raise JWTClaimsError('Invalid issuer')
def _validate_sub(claims):
"""Validates that the 'sub' claim is valid.
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.
Args:
claims (dict): The claims dictionary to validate.
"""
if 'sub' not in claims:
return
if not isinstance(claims['sub'], string_types):
raise JWTClaimsError('Subject must be a string.')
def _validate_jti(claims):
"""Validates that the 'jti' claim is valid.
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.
Args:
claims (dict): The claims dictionary to validate.
"""
if 'jti' not in claims:
return
if not isinstance(claims['jti'], string_types):
raise JWTClaimsError('JWT ID must be a string.')
def _validate_claims(claims, audience=None, issuer=None, options=None):
leeway = options.get('leeway', 0)
if isinstance(leeway, timedelta):
leeway = timedelta_total_seconds(leeway)
if not isinstance(audience, (string_types, type(None))):
raise JWTError('audience must be a string or None')
if options.get('verify_iat'):
_validate_iat(claims)
if options.get('verify_nbf'):
_validate_nbf(claims, leeway=leeway)
if options.get('verify_exp'):
_validate_exp(claims, leeway=leeway)
if options.get('verify_aud'):
_validate_aud(claims, audience=audience)
if options.get('verify_iss'):
_validate_iss(claims, issuer=issuer)
if options.get('verify_sub'):
_validate_sub(claims)
if options.get('verify_jti'):
_validate_jti(claims)