(Objective-C) Signed Zip as Base64 with XAdES-BES

This example is to help companies implement a solution for sending XAdES-BES to the Polish government for reporting purposes. Specifically:

Przed podpisaniem deklaracja zbiorcza (PIT-11Z, PIT-8CZ, PIT-40Z, PIT-RZ) musi zostać
umieszczona w archiwum ZIP. W tym przypadku, podpisywany jest plik archiwum ZIP,
przyjmujący w podpisie XAdES-BES formę zakodowaną base64.

The example demonstrates the following:

1. Zip an XML file (PIT-11Z.xml is zipped to PIT-11Z.zip)
2. Create XML to be signed, where the XML contains the base64 encoded content of the PIT-11Z.zip archive.
3. XAdES-BES sign the XML containing the base64 zip.

This example will also show the reverse:

1. Verify the signed XML.
2. Extract the PIT-11z.zip from the signed XML.
3. Unzip the PIT-11Z.zip to get the original PIT-11Z.xml

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

#import <CkoStringBuilder.h>
#import <CkoZip.h>
#import <CkoZipEntry.h>
#import <CkoBinData.h>
#import <CkoXmlDSigGen.h>
#import <CkoXml.h>
#import <CkoCert.h>
#import <CkoXmlDSig.h>
#import <NSString.h>

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

// Zip the PIT-11Z.xml to create PIT-11Z.zip (not as a .zip file, but in-memory).
CkoStringBuilder *sbXmlToZip = [[CkoStringBuilder alloc] init];
BOOL success = [sbXmlToZip LoadFile: @"qa_data/xml/PIT-11Z.xml" charset: @"utf-8"];
if (success != YES) {
    NSLog(@"%@",@"Failed to load the XML to be zipped.");
    return;
}

CkoZip *zip = [[CkoZip alloc] init];

// Initialize the zip object. No file is created in this call.
// It should always return YES.
success = [zip NewZip: @"PIT-11Z.zip"];

// Add the XML to be zipped.
CkoZipEntry *entry = [zip AppendString: @"PIT-11Z.xml" str: [sbXmlToZip GetAsString]];

// Write the zip to a BinData object.
CkoBinData *bdZip = [[CkoBinData alloc] init];
[zip WriteBd: bdZip];
// The contents of the bdZip will be retrieved in base64 format when needed below..

CkoXmlDSigGen *gen = [[CkoXmlDSigGen alloc] init];

gen.SigLocation = @"";
gen.SigLocationMod = [NSNumber numberWithInt:0];

gen.SigId = @"Signature_2a8df7f8-b958-40cc-83f6-edb53b837347_19";
gen.SigNamespacePrefix = @"ds";
gen.SigNamespaceUri = @"http://www.w3.org/2000/09/xmldsig#";
gen.SigValueId = @"SignatureValue_2a8df7f8-b958-40cc-83f6-edb53b837347_52";
gen.SignedInfoId = @"SignedInfo_2a8df7f8-b958-40cc-83f6-edb53b837347_41";
gen.SignedInfoCanonAlg = @"C14N";
gen.SignedInfoDigestMethod = @"sha1";

// Set the KeyInfoId before adding references..
gen.KeyInfoId = @"KeyInfo_2a8df7f8-b958-40cc-83f6-edb53b837347_24";

// Create an Object to be added to the Signature.
CkoXml *object1 = [[CkoXml alloc] init];
object1.Tag = @"xades:QualifyingProperties";
[object1 AddAttribute: @"xmlns:xades" value: @"http://uri.etsi.org/01903/v1.3.2#"];
[object1 AddAttribute: @"Id" value: @"QualifyingProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_43"];
[object1 AddAttribute: @"Target" value: @"#Signature_2a8df7f8-b958-40cc-83f6-edb53b837347_19"];
[object1 UpdateAttrAt: @"xades:SignedProperties" autoCreate: YES attrName: @"Id" attrValue: @"SignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4e"];
[object1 UpdateAttrAt: @"xades:SignedProperties|xades:SignedSignatureProperties" autoCreate: YES attrName: @"Id" attrValue: @"SignedSignatureProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_0a"];
// Chilkat will replace the strings "TO BE GENERATED BY CHILKAT" with actual values when the signature is created.
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningTime" value: @"TO BE GENERATED BY CHILKAT"];
// Note: It may be that http://www.w3.org/2001/04/xmlenc#sha256 is needed in the following line instead of http://www.w3.org/2000/09/xmldsig#sha1
[object1 UpdateAttrAt: @"xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningCertificateV2|xades:Cert|xades:CertDigest|ds:DigestMethod" autoCreate: YES attrName: @"Algorithm" attrValue: @"http://www.w3.org/2000/09/xmldsig#sha1"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningCertificateV2|xades:Cert|xades:CertDigest|ds:DigestValue" value: @"TO BE GENERATED BY CHILKAT"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningCertificateV2|xades:Cert|xades:IssuerSerialV2" value: @"TO BE GENERATED BY CHILKAT"];
[object1 UpdateAttrAt: @"xades:SignedProperties|xades:SignedDataObjectProperties" autoCreate: YES attrName: @"Id" attrValue: @"SignedDataObjectProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4b"];
[object1 UpdateAttrAt: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat" autoCreate: YES attrName: @"ObjectReference" attrValue: @"#Reference1_2a8df7f8-b958-40cc-83f6-edb53b837347_27"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:Description" value: @"MIME-Version: 1.0\r\nContent-Type: application/zip\r\nContent-Transfer-Encoding: binary\r\nContent-Disposition: filename=&quot;PIT-11Z.zip&quot;"];
[object1 UpdateAttrAt: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:Identifier" autoCreate: YES attrName: @"Qualifier" attrValue: @"OIDAsURI"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:Identifier" value: @"http://www.certum.pl/OIDAsURI/signedFile/1.2.616.1.113527.3.1.1.3.1"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:Description" value: @"Opis formatu dokumentu oraz jego pelna nazwa"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:DocumentationReferences|xades:DocumentationReference" value: @"http://www.certum.pl/OIDAsURI/signedFile.pdf"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:MimeType" value: @"application/zip"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:CommitmentTypeIndication|xades:CommitmentTypeId|xades:Identifier" value: @"http://uri.etsi.org/01903/v1.2.2#ProofOfApproval"];
[object1 UpdateChildContent: @"xades:SignedProperties|xades:SignedDataObjectProperties|xades:CommitmentTypeIndication|xades:AllSignedDataObjects" value: @""];
[object1 UpdateAttrAt: @"xades:UnsignedProperties" autoCreate: YES attrName: @"Id" attrValue: @"UnsignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_55"];

// Emit XML in compact (single-line) format to avoid whitespace problems.
object1.EmitCompact = YES;
[gen AddObject: @"" content: [object1 GetXml] mimeType: @"" encoding: @""];

// Create an Object to be added to the Signature.
// This is where we add the base64 representation of the PIT-11Z.zip
[gen AddObject: @"Object1_2a8df7f8-b958-40cc-83f6-edb53b837347" content: [bdZip GetEncoded: @"base64"] mimeType: @"" encoding: @"http://www.w3.org/2000/09/xmldsig#base64"];

// -------- Reference 1 --------
[gen AddObjectRef: @"Object1_2a8df7f8-b958-40cc-83f6-edb53b837347" digestMethod: @"sha1" canonMethod: @"C14N_WithComments" prefixList: @"" refType: @""];
[gen SetRefIdAttr: @"Object1_2a8df7f8-b958-40cc-83f6-edb53b837347" value: @"Reference1_2a8df7f8-b958-40cc-83f6-edb53b837347_27"];

// -------- Reference 2 --------
[gen AddObjectRef: @"SignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4e" digestMethod: @"sha1" canonMethod: @"" prefixList: @"" refType: @"http://uri.etsi.org/01903#SignedProperties"];
[gen SetRefIdAttr: @"SignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4e" value: @"SignedProperties-Reference_2a8df7f8-b958-40cc-83f6-edb53b837347_28"];

// Provide a certificate + private key. (PFX password is test123)
CkoCert *cert = [[CkoCert alloc] init];
success = [cert LoadPfxFile: @"qa_data/pfx/cert_test123.pfx" password: @"test123"];
if (success != YES) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

[gen SetX509Cert: cert usePrivateKey: YES];

gen.KeyInfoType = @"X509Data";
gen.X509Type = @"Certificate";

// This will be an enveloping signature where the Signature element
// is the XML document root, the signed data is contained within Object
// tag(s) within the Signature.
// Therefore, pass an empty sbXml to CreateXmlDsigSb.
CkoStringBuilder *sbXml = [[CkoStringBuilder alloc] init];

// The Polish government's XmlDSig implementation requires that we reproduce an attribute-sorting error.
// (This is an error in the XML canonicalization that is not noticed when both the signature-creation code and signature-verification code use
// the same XML canonicalization implementation w/ the bug.)
gen.Behaviors = @"AttributeSortingBug,CompactSignedXml";

// Sign the XML...
success = [gen CreateXmlDSigSb: sbXml];
if (success != YES) {
    NSLog(@"%@",gen.LastErrorText);
    return;
}

// -----------------------------------------------

// Save the signed XML to a file.
success = [sbXml WriteFile: @"qa_output/signedXml.xml" charset: @"utf-8" emitBom: NO];

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

// ----------------------------------------
// Verify the signature we just produced...
CkoXmlDSig *verifier = [[CkoXmlDSig alloc] init];
success = [verifier LoadSignatureSb: sbXml];
if (success != YES) {
    NSLog(@"%@",verifier.LastErrorText);
    return;
}

BOOL verified = [verifier VerifySignature: YES];
if (verified != YES) {
    NSLog(@"%@",verifier.LastErrorText);
    return;
}

NSLog(@"%@",@"This signature was successfully verified.");

// ------------------------------------
// Finally, let's extract the .zip from the signed XML, and then unzip the original PIT-11Z.xml from the in-memory zip.
CkoXml *xml = [[CkoXml alloc] init];
[xml LoadSb: sbXml autoTrim: YES];

// The base64 image of the PIT-11Z.zip is in the 2nd ds:Object child of the ds:Signature (the ds:Signature is the root element of the signed XML).
// (ds:Object[0] would be the 1st ds:Object child.  Index 1 is the 2nd ds:Object child.)
NSString *strZipBase64 = [xml GetChildContent: @"ds:Object[1]"];

[bdZip Clear];
[bdZip AppendEncoded: strZipBase64 encoding: @"base64"];
if ([bdZip.NumBytes intValue] == 0) {
    NSLog(@"%@",@"Something went wrong.. we dont' have any data..");
    return;
}

success = [zip OpenBd: bdZip];
if (success != YES) {
    NSLog(@"%@",zip.LastErrorText);
    return;
}

// Get the 1st file in the zip, which should be the PIT-11Z.xml
entry = [zip GetEntryByIndex: [NSNumber numberWithInt: 0]];
if (zip.LastMethodSuccess != YES) {
    NSLog(@"%@",@"Zip contains no files...");
    return;
}

// Get the XML:
NSString *origXml = [entry UnzipToString: [NSNumber numberWithInt: 0] srcCharset: @"utf-8"];
NSLog(@"%@",@"Original XML extracted from base64 zip:");
NSLog(@"%@",origXml);