(PowerShell) Verify JWT Using HS256, HS384, or HS512

Demonstrates how to verify a JWT that was signed using HS256, HS384, or HS512. (HS256 is JWT's acronym for HMAC-SHA256.)

This example verifies the signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# Demonstrates how to verify an HMAC JWT using a shared secret (password).

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

$jwt = New-Object Chilkat.Jwt

$token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU"

# First verify the signature.
# The password used to create this JWT was "secret".
$sigVerified = $jwt.VerifyJwt($token,"secret")
$("with correct password: " + $sigVerified)

# Now try with a different password:
$sigVerified = $jwt.VerifyJwt($token,"secret2")
$("with incorrect password " + $sigVerified)

# Let's see if the time constraints, if any, are valid.
# The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
# If the current system time is before the "nbf" time, or after the "exp" time,
# then IsTimeValid will return false/0.
# Also, we'll allow a leeway of 60 seconds to account for any clock skew.
# Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
$leeway = 60
$bTimeValid = $jwt.IsTimeValid($token,$leeway)
$("time constraints valid: " + $bTimeValid)

# Now let's recover the original claims JSON (the payload).
$payload = $jwt.GetPayload($token)
# The payload will likely be in compact form:
$($payload)

# We can format for human viewing by loading it into Chilkat's JSON object
# and emit.
$json = New-Object Chilkat.JsonObject
$success = $json.Load($payload)
$json.EmitCompact = $false
$($json.Emit())

# We can recover the original JOSE header in the same way:
$joseHeader = $jwt.GetHeader($token)
# The payload will likely be in compact form:
$($joseHeader)

# We can format for human viewing by loading it into Chilkat's JSON object
# and emit.
$success = $json.Load($joseHeader)
$json.EmitCompact = $false
$($json.Emit())