(Tcl) JWS Using HMAC SHA-256

Creates a JSON Web Signatures (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.

# First create the JWS Protected Header
set jwsProtHdr [new_CkJsonObject]

CkJsonObject_AppendString $jwsProtHdr "typ" "JWT"
CkJsonObject_AppendString $jwsProtHdr "alg" "HS256"
puts "JWS Protected Header: [CkJsonObject_emit $jwsProtHdr]"

# Output:
# JWS Protected Header: {"typ":"JWT","alg":"HS256"}

set jws [new_CkJws]

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

# Set the protected header:
CkJws_SetProtectedHeader $jws $signatureIndex $jwsProtHdr

# Set the payload.
set bIncludeBom 0
set payloadStr "In our village, folks say God crumbles up the old moon into stars."
CkJws_SetPayload $jws $payloadStr "utf-8" $bIncludeBom

# Create the JWS
# By default, the compact serialization is used.
set jwsCompact [CkJws_createJws $jws]
if {[CkJws_get_LastMethodSuccess $jws] != 1} then {
    puts [CkJws_lastErrorText $jws]
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    exit
}

puts "JWS: $jwsCompact"

# sample output:
# JWS: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.bsYsi8HJ0N6OqGI1hKQ9QQRNPxxA5qMpcHLtOvXatk8

# Now load the JWS, validate, and recover the original text.
set jws2 [new_CkJws]

# Load the JWS.
set success [CkJws_LoadJws $jws2 $jwsCompact]

# Set the MAC key used for validation.
set signatureIndex 0
CkJws_SetMacKey $jws2 $signatureIndex $hmacKey "base64url"

# Validate the 1st (and only) signature at index 0..
set v [CkJws_Validate $jws2 $signatureIndex]
if {$v < 0} then {
    # Perhaps Chilkat was not unlocked or the trial expired..
    puts "Method call failed for some other reason."
    puts [CkJws_lastErrorText $jws2]
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

if {$v == 0} then {
    puts "Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both."
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

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

# Recover the original content:
puts [CkJws_getPayload $jws2 utf-8]

# Examine the protected header:
# joseHeader is a CkJsonObject
set joseHeader [CkJws_GetProtectedHeader $jws2 $signatureIndex]
if {[CkJws_get_LastMethodSuccess $jws2] != 1} then {
    puts "No protected header found at the given index."
    delete_CkJsonObject $jwsProtHdr
    delete_CkJws $jws
    delete_CkJws $jws2
    exit
}

CkJsonObject_put_EmitCompact $joseHeader 0

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

# Output:

# 	Signature validated.
# 	In our village, folks say God crumbles up the old moon into stars.
# 	Protected (JOSE) header:
# 	{ 
# 	  "typ": "JWT",
# 	  "alg": "HS256"
# 	} 

delete_CkJsonObject $jwsProtHdr
delete_CkJws $jws
delete_CkJws $jws2