(Tcl) 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.

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load ./chilkat.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.

set jwt [new_CkJwt]

set token "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU"

# First verify the signature.
# The password used to create this JWT was "secret".
set sigVerified [CkJwt_VerifyJwt $jwt $token "secret"]
puts "with correct password: $sigVerified"

# Now try with a different password:
set sigVerified [CkJwt_VerifyJwt $jwt $token "secret2"]
puts "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.
set leeway 60
set bTimeValid [CkJwt_IsTimeValid $jwt $token $leeway]
puts "time constraints valid: $bTimeValid"

# Now let's recover the original claims JSON (the payload).
set payload [CkJwt_getPayload $jwt $token]
# The payload will likely be in compact form:
puts "$payload"

# We can format for human viewing by loading it into Chilkat's JSON object
# and emit.
set json [new_CkJsonObject]

set success [CkJsonObject_Load $json $payload]
CkJsonObject_put_EmitCompact $json 0
puts [CkJsonObject_emit $json]

# We can recover the original JOSE header in the same way:
set joseHeader [CkJwt_getHeader $jwt $token]
# The payload will likely be in compact form:
puts "$joseHeader"

# We can format for human viewing by loading it into Chilkat's JSON object
# and emit.
set success [CkJsonObject_Load $json $joseHeader]
CkJsonObject_put_EmitCompact $json 0
puts [CkJsonObject_emit $json]

delete_CkJwt $jwt
delete_CkJsonObject $json