(Tcl) Validate JWS Using HMAC SHA-256

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

Note: This example requires Chilkat v9.5.0.66 or greater.

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load ./chilkat.dll

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

# Note: This example requires Chilkat v9.5.0.66 or greater.

# 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:
# joseHeader is a CkJsonObject
set joseHeader [CkJws_GetProtectedHeader $jws $signatureIndex]
if {[CkJws_get_LastMethodSuccess $jws] != 1} then {
    puts "No protected header found at the given index."
    delete_CkJws $jws
    exit
}

CkJsonObject_put_EmitCompact $joseHeader 0

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