(Objective-C) Ibanity HTTP Signature for XS2A, Isabel Connect, Ponto Connect

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Demonstrates how to add a Signature header for Ibanity HTTP requests.

For more information, see https://documentation.ibanity.com/http-signature

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#import <CkoJsonObject.h>
#import <NSString.h>
#import <CkoDateTime.h>
#import <CkoCrypt2.h>
#import <CkoStringBuilder.h>
#import <CkoPrivateKey.h>
#import <CkoRsa.h>

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

BOOL success;

// In order to sign your HTTP requests, you have to add 2 headers to the HTTP request: Digest: the digest of the request payload and Signature: the actual signature of the request. 

// POST /xs2a/customer-access-tokens HTTP/1.1
// Host: api.ibanity.com
// Content-Type: application/json
// Digest: SHA-512=z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg/SpIdNs6c5H0NE8XYXysP+DGNKHfuwvY7kxvUdBeoGlODJ6+SfaPg==
// Ibanity-Idempotency-Key: 61f02718-eeee-46e1-b5eb-e8fd6e799c2d
// Signature: keyId="62f02718-eeee-46e1-b5eb-e8fd6e799c2e",created=1599659223,algorithm="hs2019",headers="(request-target) host digest (created) ibanity-idempotency-key",signature="SjWJWbWN7i0...zsbM="
// 
// {"data":{"type":"customerAccessToken", "attributes":{"applicationCustomerReference":"15874569"}}}

// The payload (body) of the above HTTP request is the JSON.
// Build the JSON above.
// Use this online tool to generate code from sample JSON: 
// Generate Code to Create JSON
CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json UpdateString: @"data.type" value: @"customerAccessToken"];
[json UpdateString: @"data.attributes.applicationCustomerReference" value: @"15874569"];

NSString *payload = [json Emit];
NSLog(@"%@%@",@"payload = ",payload);

// Step 1: Build the (created) virtual header

CkoDateTime *dtNow = [[CkoDateTime alloc] init];
[dtNow SetFromCurrentSystemTime];
NSString *created = [dtNow GetAsUnixTimeStr: NO];
NSLog(@"%@%@",@"created = ",created);

// Step 2: Build the Digest header
CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];
crypt.HashAlgorithm = @"sha512";
crypt.EncodingMode = @"base64";
crypt.Charset = @"utf-8";

CkoStringBuilder *sbDigestHdrValue = [[CkoStringBuilder alloc] init];
[sbDigestHdrValue Append: @"SHA-512="];
[sbDigestHdrValue Append: [crypt HashStringENC: [json Emit]]];

NSLog(@"%@",[sbDigestHdrValue GetAsString]);

// Step 3: Build the (request target) virtual header

// In order to build the signature you will need a virtual header named (request-target) (the parentheses are important). 
// The (request-target) is the string concatenation of the HTTP method (in lowercase) with the path and query parameters.
NSString *request_target = @"post /xs2a/customer-access-tokens";

// Step 4: Build the signing string

// The signing string is the concatenation of the signed header names (in lowercase) and values separated by a LF.

// You must always sign the following headers: (request-target), host, (created), digest. 
// If used, you must also sign the authorization header and any ibanity-* headers, such as ibanity-idempotency-key. 

CkoStringBuilder *sbSigningString = [[CkoStringBuilder alloc] init];
[sbSigningString Append: @"(request-target): "];
[sbSigningString AppendLine: request_target crlf: NO];
[sbSigningString Append: @"host: "];
[sbSigningString AppendLine: @"api.ibanity.com" crlf: NO];
[sbSigningString Append: @"digest: "];
[sbSigningString AppendLine: [sbDigestHdrValue GetAsString] crlf: NO];
[sbSigningString Append: @"(created): "];
[sbSigningString AppendLine: created crlf: NO];
[sbSigningString Append: @"ibanity-idempotency-key: "];
NSString *idempotencyKey = [crypt GenerateUuid];
[sbSigningString Append: idempotencyKey];

// Step 5: Build the signed headers list

// To allow Ibanity to check the signed headers, you must provide a list of the header names. They should be lowercase and in the same order used to create the signing string. 
NSString *signed_headers_list = @"(request-target) host digest (created) ibanity-idempotency-key";

// Step 6: Build the Signature header

// This is where the real signing happens. The signature header is a combination of several sub-headers -
// 
//     keyId: the identifier for the application's signature certificate, obtained from the Developer Portal
//     algorithm: the digital signature algorithm used to generate the signature (must be hs2019)
//     headers: The list of HTTP headers created in step 5
//     signature: the Base64-encoded digital signature of the signing string created in step 4.

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
success = [privKey LoadEncryptedPemFile: @"my_ibanity_signature_private_key.pem" password: @"pem_password"];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

CkoRsa *rsa = [[CkoRsa alloc] init];
rsa.PssSaltLen = [NSNumber numberWithInt:32];
rsa.EncodingMode = @"base64";
// Use the RSASSA-PSS signature algorithm
rsa.OaepPadding = YES;

success = [rsa ImportPrivateKeyObj: privKey];
if (success == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

// Sign the signing string.
NSString *sigBase64 = [rsa SignStringENC: [sbSigningString GetAsString] hashAlg: @"sha-256"];
if (rsa.LastMethodSuccess == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

// Build the signature header value.
CkoStringBuilder *sbSigHeaderValue = [[CkoStringBuilder alloc] init];
[sbSigHeaderValue Append: @"keyId=\""];
// Use your identifier for the application's signature certificate, obtained from the Developer Portal
[sbSigHeaderValue Append: @"62f02718-eeee-46e1-b5eb-e8fd6e799c2e"];
[sbSigHeaderValue Append: @"\",created="];
[sbSigHeaderValue Append: created];
[sbSigHeaderValue Append: @",algorithm=\"hs2019\",headers=\""];
[sbSigHeaderValue Append: signed_headers_list];
[sbSigHeaderValue Append: @"\",signature=\""];
[sbSigHeaderValue Append: sigBase64];
[sbSigHeaderValue Append: @"\""];

NSLog(@"%@",[sbSigHeaderValue GetAsString]);