(Ruby) Validate a JWS Using ECDSA P-256 SHA-256

Validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

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

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# 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-256", 
#       "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU", 
#       "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" 
#      } 

sbPubKey = Chilkat::CkStringBuilder.new()
sbPubKey.Append("{\"kty\":\"EC\",")
sbPubKey.Append("\"crv\":\"P-256\",")
sbPubKey.Append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",")
sbPubKey.Append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\"")
sbPubKey.Append("}")

pubKey = Chilkat::CkPublicKey.new()
success = pubKey.LoadFromString(sbPubKey.getAsString())
if (success != true)
    print pubKey.lastErrorText() + "\n";
    exit
end

jws = Chilkat::CkJws.new()

# Set the ECC public key:
signatureIndex = 0
jws.SetPublicKey(signatureIndex,pubKey)

# Load the JWS.
sbJws = Chilkat::CkStringBuilder.new()
sbJws.Append("eyJhbGciOiJFUzI1NiJ9")
sbJws.Append(".")
sbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
sbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
sbJws.Append(".")
sbJws.Append("DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA")
sbJws.Append("pmWQxfKTUJqPP3-Kg6NU1Q")

success = jws.LoadJwsSb(sbJws)
if (success != true)
    print jws.lastErrorText() + "\n";
    exit
end

# Validate the 1st (and only) signature at index 0..
v = jws.Validate(signatureIndex)
if (v < 0)
    # Perhaps Chilkat was not unlocked or the trial expired..
    print "Method call failed for some other reason." + "\n";
    print jws.lastErrorText() + "\n";
    exit
end

if (v == 0)
    print "Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both." + "\n";
    exit
end

# If we get here, the signature was validated..
print "Signature validated." + "\n";
print "--" + "\n";

# Recover the original content:
print "Recovered content:" + "\n";
print jws.getPayload("utf-8") + "\n";
print "--" + "\n";

# Examine the protected header:
# joseHeader is a CkJsonObject
joseHeader = jws.GetProtectedHeader(signatureIndex)
if (jws.get_LastMethodSuccess() != true)
    print "No protected header found at the given index." + "\n";
    exit
end

joseHeader.put_EmitCompact(false)

print "Protected (JOSE) header:" + "\n";
print joseHeader.emit() + "\n";

# Output:

# 	Signature validated.
# 	--
# 	Recovered content:
# 	{"iss":"joe",
# 	 "exp":1300819380,
# 	 "http://example.com/is_root":true}
# 	--
# 	Protected (JOSE) header:
# 	{ 
# 	  "alg": "ES256"
# 	}