Tcl Requires Chilkat v11.0.0+

Validate JWS Using HMAC SHA-256

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) using HMAC SHA-256. Tcl

load ./chilkat.dll

set success 0

#  This requires the Chilkat API to have been previously unlocked.
#  See Global Unlock Sample for sample code.

#  This example takes a JSON signature in compact serialization format,
#  and uses a MAC key to validate and recover the protected header and payload.

set jws [new_CkJws]

#  Set the HMAC key:
set hmacKey "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
set signatureIndex 0
CkJws_SetMacKey $jws $signatureIndex $hmacKey "base64url"

#  Load the JWS.
set jwsCompact "eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"
set success [CkJws_LoadJws $jws $jwsCompact]

#  Validate the 1st (and only) signature at index 0..
set v [CkJws_Validate $jws $signatureIndex]
if {$v < 0} then {
    #  Perhaps Chilkat was not unlocked or the trial expired..
    puts "Method call failed for some other reason."
    puts [CkJws_lastErrorText $jws]
    delete_CkJws $jws
    exit
}

if {$v == 0} then {
    puts "Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both."
    delete_CkJws $jws
    exit
}

#  If we get here, the signature was validated..
puts "Signature validated."

#  Recover the original content:
puts "Recovered content:"
puts [CkJws_getPayload $jws utf-8]

#  Examine the protected header:

set joseHeader [new_CkJsonObject]

set success [CkJws_GetProtectedH $jws $signatureIndex $joseHeader]
if {$success == 0} then {
    puts [CkJws_lastErrorText $jws]
    delete_CkJws $jws
    delete_CkJsonObject $joseHeader
    exit
}

CkJsonObject_put_EmitCompact $joseHeader 0

puts "Protected (JOSE) header:"
puts [CkJsonObject_emit $joseHeader]

#  Output:

#  	Signature validated.
#  	Recovered content:
#  	{"iss":"joe",
#  	 "exp":1300819380,
#  	 "http://example.com/is_root":true}
#  	Protected (JOSE) header:
#  	{ 
#  	  "typ": "JWT",
#  	  "alg": "HS256"
#  	}

delete_CkJws $jws
delete_CkJsonObject $joseHeader