(Tcl) Validate a JWS Using ECDSA P-521 SHA-512

Validates a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512

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 an ECDSA public key to validate and recover the protected header and payload.

# We only need a public key for signature validation.  This is the ECDSA public key
# that is used:

#      {"kty":"EC", 
#       "crv":"P-521", 
#       "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk", 
#       "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" 
#      } 

set sbPubKey [new_CkStringBuilder]

CkStringBuilder_Append $sbPubKey "{\"kty\":\"EC\","
CkStringBuilder_Append $sbPubKey "\"crv\":\"P-521\","
CkStringBuilder_Append $sbPubKey "\"x\":\"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk\","
CkStringBuilder_Append $sbPubKey "\"y\":\"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2\""
CkStringBuilder_Append $sbPubKey "}"

set pubKey [new_CkPublicKey]

set success [CkPublicKey_LoadFromString $pubKey [CkStringBuilder_getAsString $sbPubKey]]
if {$success != 1} then {
    puts [CkPublicKey_lastErrorText $pubKey]
    delete_CkStringBuilder $sbPubKey
    delete_CkPublicKey $pubKey
    exit
}

set jws [new_CkJws]

# Set the ECC public key:
set signatureIndex 0
CkJws_SetPublicKey $jws $signatureIndex $pubKey

# Load the JWS.
set sbJws [new_CkStringBuilder]

CkStringBuilder_Append $sbJws "eyJhbGciOiJFUzUxMiJ9"
CkStringBuilder_Append $sbJws "."
CkStringBuilder_Append $sbJws "UGF5bG9hZA"
CkStringBuilder_Append $sbJws "."
CkStringBuilder_Append $sbJws "AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq"
CkStringBuilder_Append $sbJws "wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp"
CkStringBuilder_Append $sbJws "EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn"

set success [CkJws_LoadJwsSb $jws $sbJws]
if {$success != 1} then {
    puts [CkJws_lastErrorText $jws]
    delete_CkStringBuilder $sbPubKey
    delete_CkPublicKey $pubKey
    delete_CkJws $jws
    delete_CkStringBuilder $sbJws
    exit
}

# 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_CkStringBuilder $sbPubKey
    delete_CkPublicKey $pubKey
    delete_CkJws $jws
    delete_CkStringBuilder $sbJws
    exit
}

if {$v == 0} then {
    puts "Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both."
    delete_CkStringBuilder $sbPubKey
    delete_CkPublicKey $pubKey
    delete_CkJws $jws
    delete_CkStringBuilder $sbJws
    exit
}

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

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

# 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_CkStringBuilder $sbPubKey
    delete_CkPublicKey $pubKey
    delete_CkJws $jws
    delete_CkStringBuilder $sbJws
    exit
}

CkJsonObject_put_EmitCompact $joseHeader 0

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

# Output:
# (the string "Payload" was the content that was signed.)

# 	Signature validated.
# 	--
# 	Recovered content:
# 	Payload
# 	--
# 	Protected (JOSE) header:
# 	{
# 	  "alg": "ES512"
# 	}

delete_CkStringBuilder $sbPubKey
delete_CkPublicKey $pubKey
delete_CkJws $jws
delete_CkStringBuilder $sbJws