PowerShell

Validate a JWS Using ECDSA P-256 SHA-256

See more JSON Web Signatures (JWS) Examples

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

Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

# 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 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 = New-Object Chilkat.StringBuilder
$sbPubKey.Append("{`"kty`":`"EC`",")
$sbPubKey.Append("`"crv`":`"P-256`",")
$sbPubKey.Append("`"x`":`"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU`",")
$sbPubKey.Append("`"y`":`"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0`"")
$sbPubKey.Append("}")

$pubKey = New-Object Chilkat.PublicKey
$success = $pubKey.LoadFromString($sbPubKey.GetAsString())
if ($success -eq $false) {
    $($pubKey.LastErrorText)
    exit
}

$jws = New-Object Chilkat.Jws

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

# Load the JWS.
$sbJws = New-Object Chilkat.StringBuilder
$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 -eq $false) {
    $($jws.LastErrorText)
    exit
}

# Validate the 1st (and only) signature at index 0..
$v = $jws.Validate($signatureIndex)
if ($v -lt 0) {
    # Perhaps Chilkat was not unlocked or the trial expired..
    $("Method call failed for some other reason.")
    $($jws.LastErrorText)
    exit
}

if ($v -eq 0) {
    $("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.")
    exit
}

# If we get here, the signature was validated..
$("Signature validated.")
$("--")

# Recover the original content:
$("Recovered content:")
$($jws.GetPayload("utf-8"))
$("--")

# Examine the protected header:

$joseHeader = New-Object Chilkat.JsonObject
$success = $jws.GetProtectedH($signatureIndex,$joseHeader)
if ($success -eq $false) {
    $($jws.LastErrorText)
    exit
}

$joseHeader.EmitCompact = $false

$("Protected (JOSE) header:")
$($joseHeader.Emit())

# Output:

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