(Objective-C) JWS Using RSASSA-PSS using SHA-256 and MGF1 with SHA-256

Creates and validates a JSON Web Signature (JWS) using RSASSA-PSS using SHA-256 and MGF1 with SHA-256.

Chilkat supports all of the following JWS algorithms:

   +--------------+-------------------------------+--------------------+
   | "alg" Param  | Digital Signature or MAC      | Implementation     |
   | Value        | Algorithm                     | Requirements       |
   +--------------+-------------------------------+--------------------+
   | HS256        | HMAC using SHA-256            | Required           |
   | HS384        | HMAC using SHA-384            | Optional           |
   | HS512        | HMAC using SHA-512            | Optional           |
   | RS256        | RSASSA-PKCS1-v1_5 using       | Recommended        |
   |              | SHA-256                       |                    |
   | RS384        | RSASSA-PKCS1-v1_5 using       | Optional           |
   |              | SHA-384                       |                    |
   | RS512        | RSASSA-PKCS1-v1_5 using       | Optional           |
   |              | SHA-512                       |                    |
   | ES256        | ECDSA using P-256 and SHA-256 | Recommended+       |
   | ES384        | ECDSA using P-384 and SHA-384 | Optional           |
   | ES512        | ECDSA using P-521 and SHA-512 | Optional           |
   | PS256        | RSASSA-PSS using SHA-256 and  | Optional           |
   |              | MGF1 with SHA-256             |                    |
   | PS384        | RSASSA-PSS using SHA-384 and  | Optional           |
   |              | MGF1 with SHA-384             |                    |
   | PS512        | RSASSA-PSS using SHA-512 and  | Optional           |
   |              | MGF1 with SHA-512             |                    |
   +--------------+-------------------------------+--------------------+

Note: This example requires Chilkat v9.5.0.66 or greater.

Chilkat Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

#import <CkoStringBuilder.h>
#import <CkoPrivateKey.h>
#import <CkoJsonObject.h>
#import <CkoJws.h>
#import <NSString.h>
#import <CkoPublicKey.h>

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

// Note: This example requires Chilkat v9.5.0.66 or greater.

// Use the following RSA key loaded from JWK format.
CkoStringBuilder *sbJwk = [[CkoStringBuilder alloc] init];
[sbJwk Append: @"{\"kty\":\"RSA\","];
[sbJwk Append: @"\"n\":\"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx"];
[sbJwk Append: @"HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs"];
[sbJwk Append: @"D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH"];
[sbJwk Append: @"SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV"];
[sbJwk Append: @"MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8"];
[sbJwk Append: @"NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ\","];
[sbJwk Append: @"\"e\":\"AQAB\","];
[sbJwk Append: @"\"d\":\"Eq5xpGnNCivDflJsRQBXHx1hdR1k6Ulwe2JZD50LpXyWPEAeP88vLNO97I"];
[sbJwk Append: @"jlA7_GQ5sLKMgvfTeXZx9SE-7YwVol2NXOoAJe46sui395IW_GO-pWJ1O0"];
[sbJwk Append: @"BkTGoVEn2bKVRUCgu-GjBVaYLU6f3l9kJfFNS3E0QbVdxzubSu3Mkqzjkn"];
[sbJwk Append: @"439X0M_V51gfpRLI9JYanrC4D4qAdGcopV_0ZHHzQlBjudU2QvXt4ehNYT"];
[sbJwk Append: @"CBr6XCLQUShb1juUO1ZdiYoFaFQT5Tw8bGUl_x_jTj3ccPDVZFD9pIuhLh"];
[sbJwk Append: @"BOneufuBiB4cS98l2SR_RQyGWSeWjnczT0QU91p1DhOVRuOopznQ\","];
[sbJwk Append: @"\"p\":\"4BzEEOtIpmVdVEZNCqS7baC4crd0pqnRH_5IB3jw3bcxGn6QLvnEtfdUdi"];
[sbJwk Append: @"YrqBdss1l58BQ3KhooKeQTa9AB0Hw_Py5PJdTJNPY8cQn7ouZ2KKDcmnPG"];
[sbJwk Append: @"BY5t7yLc1QlQ5xHdwW1VhvKn-nXqhJTBgIPgtldC-KDV5z-y2XDwGUc\","];
[sbJwk Append: @"\"q\":\"uQPEfgmVtjL0Uyyx88GZFF1fOunH3-7cepKmtH4pxhtCoHqpWmT8YAmZxa"];
[sbJwk Append: @"ewHgHAjLYsp1ZSe7zFYHj7C6ul7TjeLQeZD_YwD66t62wDmpe_HlB-TnBA"];
[sbJwk Append: @"-njbglfIsRLtXlnDzQkv5dTltRJ11BKBBypeeF6689rjcJIDEz9RWdc\","];
[sbJwk Append: @"\"dp\":\"BwKfV3Akq5_MFZDFZCnW-wzl-CCo83WoZvnLQwCTeDv8uzluRSnm71I3Q"];
[sbJwk Append: @"CLdhrqE2e9YkxvuxdBfpT_PI7Yz-FOKnu1R6HsJeDCjn12Sk3vmAktV2zb"];
[sbJwk Append: @"34MCdy7cpdTh_YVr7tss2u6vneTwrA86rZtu5Mbr1C1XsmvkxHQAdYo0\","];
[sbJwk Append: @"\"dq\":\"h_96-mK1R_7glhsum81dZxjTnYynPbZpHziZjeeHcXYsXaaMwkOlODsWa"];
[sbJwk Append: @"7I9xXDoRwbKgB719rrmI2oKr6N3Do9U0ajaHF-NKJnwgjMd2w9cjz3_-ky"];
[sbJwk Append: @"NlxAr2v4IKhGNpmM5iIgOS1VZnOZ68m6_pbLBSp3nssTdlqvd0tIiTHU\","];
[sbJwk Append: @"\"qi\":\"IYd7DHOhrWvxkwPQsRM2tOgrjbcrfvtQJipd-DlcxyVuuM9sQLdgjVk2o"];
[sbJwk Append: @"y26F0EmpScGLq2MowX7fhd_QJQ3ydy5cY7YIBi87w93IKLEdfnbJtoOPLU"];
[sbJwk Append: @"W0ITrJReOgo1cq9SbsxYawBgfp_gh6A5603k2-ZQwVK0JKSHuLFkuQ3U\""];
[sbJwk Append: @"}"];

CkoPrivateKey *rsaKey = [[CkoPrivateKey alloc] init];
// Note: This example loads the RSA key from JWK format.  Any format can be loaded
// into the private key object. (See the online reference documentation..)
BOOL success = [rsaKey LoadJwk: [sbJwk GetAsString]];
if (success != YES) {
    NSLog(@"%@",rsaKey.LastErrorText);
    return;
}

// Create the JWS Protected Header
CkoJsonObject *jwsProtHdr = [[CkoJsonObject alloc] init];
[jwsProtHdr AppendString: @"alg" value: @"PS256"];

CkoJws *jws = [[CkoJws alloc] init];

// Set the protected header:
int signatureIndex = 0;
[jws SetProtectedHeader: [NSNumber numberWithInt: signatureIndex] json: jwsProtHdr];

// Set the RSA key:
[jws SetPrivateKey: [NSNumber numberWithInt: signatureIndex] privKey: rsaKey];

// Set the payload.
BOOL bIncludeBom = NO;
NSString *payloadStr = @"In our village, folks say God crumbles up the old moon into stars.";
[jws SetPayload: payloadStr charset: @"utf-8" includeBom: bIncludeBom];

// Create the JWS
// By default, the compact serialization is used.
NSString *jwsCompact = [jws CreateJws];
if (jws.LastMethodSuccess != YES) {
    NSLog(@"%@",jws.LastErrorText);
    return;
}

NSLog(@"%@%@",@"JWS: ",jwsCompact);

// Note: RSA PSS padding uses random values, so the output will be different each time a signature is produced.
// sample output:
// JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

// Now load the JWS, validate, and recover the original text.
CkoJws *jws2 = [[CkoJws alloc] init];

// Load the JWS.
success = [jws2 LoadJws: jwsCompact];

CkoPublicKey *rsaPubKey = [rsaKey GetPublicKey];

// Set the RSA public key used for validation.
signatureIndex = 0;
[jws2 SetPublicKey: [NSNumber numberWithInt: signatureIndex] pubKey: rsaPubKey];

// Validate the 1st (and only) signature at index 0..
int v = [[jws2 Validate: [NSNumber numberWithInt: signatureIndex]] intValue];
if (v < 0) {
    // Perhaps Chilkat was not unlocked or the trial expired..
    NSLog(@"%@",@"Method call failed for some other reason.");
    NSLog(@"%@",jws2.LastErrorText);
    return;
}

if (v == 0) {
    NSLog(@"%@",@"Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both.");
    return;
}

// If we get here, the signature was validated..
NSLog(@"%@",@"Signature validated.");

// Recover the original content:
NSLog(@"%@",[jws2 GetPayload: @"utf-8"]);

// Examine the protected header:
CkoJsonObject *joseHeader = [jws2 GetProtectedHeader: [NSNumber numberWithInt: signatureIndex]];
if (jws2.LastMethodSuccess != YES) {
    NSLog(@"%@",@"No protected header found at the given index.");
    return;
}

joseHeader.EmitCompact = NO;

NSLog(@"%@",@"Protected (JOSE) header:");
NSLog(@"%@",[joseHeader Emit]);

// Output:

// 	Signature validated.
// 	In our village, folks say God crumbles up the old moon into stars.
// 	Protected (JOSE) header:
// 	{ 
// 	  "alg": "PS256"
// 	}