(Objective-C) 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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#import <CkoPublicKey.h>
#import <CkoJwt.h>
#import <NSString.h>
#import <CkoJsonObject.h>

// 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.

CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];
BOOL success = [pubKey LoadFromFile: @"qa_data/pem/rsa_public.pem"];

CkoJwt *jwt = [[CkoJwt alloc] init];

NSString *token = @"eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDQ1MjM4LCJuYmYiOjE0NjM0NDUyMzgsImV4cCI6MTQ2MzQ0ODgzOH0.XRtqed6nuJ9lrp0wbNdDX3fCkSh_d9cHAniPbNcqm7G-5N3mtI5ntQvZBDP3pHtECVqufuDwW7XgUtzAi0ZXhyiRm1iZ3wMSN5lHWv52OQJmMHPA7VPd8Q1hDG-tx-QswzJKd75OEUHP7wIXq2Mg_YVElfDvJI6TGjGyS1y-RLHlz-ldlGsEwIBkO0PtzIYTVov97x8p9KCsPNhS4lZUIqKOYoTZUV5LpuAWARl-636DfMEB_A5_IEaw_W8leh2suP2ULVZxwE-Tk1kBC9tsSGrBrPTtg7sziaV4Lbb0JRANmh98uTRu5f8ji9CVOnpbMiAzjsJSy56kz_olweXSuA";

// First verify the signature.
BOOL sigVerified = [jwt VerifyJwtPk: token key: pubKey];
NSLog(@"%@%d",@"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.
int leeway = 60;
BOOL bTimeValid = [jwt IsTimeValid: token leeway: [NSNumber numberWithInt: leeway]];
NSLog(@"%@%d",@"time constraints valid: ",bTimeValid);

// Now let's recover the original claims JSON (the payload).
NSString *payload = [jwt GetPayload: token];
// The payload will likely be in compact form:
NSLog(@"%@",payload);

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
CkoJsonObject *json = [[CkoJsonObject alloc] init];
success = [json Load: payload];
json.EmitCompact = NO;
NSLog(@"%@",[json Emit]);

// We can recover the original JOSE header in the same way:
NSString *joseHeader = [jwt GetHeader: token];
// The payload will likely be in compact form:
NSLog(@"%@",joseHeader);

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
success = [json Load: joseHeader];
json.EmitCompact = NO;
NSLog(@"%@",[json Emit]);