Objective-C

Verify JWT Using HS256, HS384, or HS512

See more JSON Web Token (JWT) Examples

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.

Objective-C

#import <CkoJwt.h>
#import <NSString.h>
#import <CkoJsonObject.h>

BOOL success = NO;

//  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.

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

NSString *token = @"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU";

//  First verify the signature.
//  The password used to create this JWT was "secret".
BOOL sigVerified = [jwt VerifyJwt: token password: @"secret"];
NSLog(@"%@%d",@"with correct password: ",sigVerified);

//  Now try with a different password:
sigVerified = [jwt VerifyJwt: token password: @"secret2"];
NSLog(@"%@%d",@"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.
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]);