(Tcl) Verify JWT Using an RSA Public Key (RS256, RS384, RS512)

Demonstrates how to verify a JWT that was signed using an RSA private key.

This example verifies the RSA 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 JWT using an RSA public key.

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

set pubKey [new_CkPublicKey]

set success [CkPublicKey_LoadFromFile $pubKey "qa_data/pem/rsa_public.pem"]

set jwt [new_CkJwt]

set token "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDQ1MjM4LCJuYmYiOjE0NjM0NDUyMzgsImV4cCI6MTQ2MzQ0ODgzOH0.XRtqed6nuJ9lrp0wbNdDX3fCkSh_d9cHAniPbNcqm7G-5N3mtI5ntQvZBDP3pHtECVqufuDwW7XgUtzAi0ZXhyiRm1iZ3wMSN5lHWv52OQJmMHPA7VPd8Q1hDG-tx-QswzJKd75OEUHP7wIXq2Mg_YVElfDvJI6TGjGyS1y-RLHlz-ldlGsEwIBkO0PtzIYTVov97x8p9KCsPNhS4lZUIqKOYoTZUV5LpuAWARl-636DfMEB_A5_IEaw_W8leh2suP2ULVZxwE-Tk1kBC9tsSGrBrPTtg7sziaV4Lbb0JRANmh98uTRu5f8ji9CVOnpbMiAzjsJSy56kz_olweXSuA"

# First verify the signature.
set sigVerified [CkJwt_VerifyJwtPk $jwt $token $pubKey]
puts "verified: $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_CkPublicKey $pubKey
delete_CkJwt $jwt
delete_CkJsonObject $json