//

//  MYSymmetricKey.m

//  MYCrypto

//

//  Created by Jens Alfke on 4/2/09.

//  Copyright 2009 Jens Alfke. All rights reserved.

//

#import "MYSymmetricKey.h"

#import "MYCryptor.h"

#import "MYCrypto_Private.h"

#if MYCRYPTO_USE_IPHONE_API

typedef uint32_t CSSM_ALGORITHMS;

enum {

// Taken from cssmtype.h in OS X 10.5 SDK:

	CSSM_ALGID_NONE =					0x00000000L,

	CSSM_ALGID_DES =					CSSM_ALGID_NONE + 14,

	CSSM_ALGID_3DES_3KEY_EDE =			CSSM_ALGID_NONE + 17,

	CSSM_ALGID_3DES_3KEY =           	CSSM_ALGID_3DES_3KEY_EDE,

	CSSM_ALGID_RC4 =					CSSM_ALGID_NONE + 25,

	CSSM_ALGID_CAST =					CSSM_ALGID_NONE + 27,

	CSSM_ALGID_VENDOR_DEFINED =			CSSM_ALGID_NONE + 0x80000000L,

	CSSM_ALGID_AES

};

#else

#import <Security/cssmtype.h>

#endif

static const CSSM_ALGORITHMS kCSSMAlgorithms[] = {

    CSSM_ALGID_AES, CSSM_ALGID_DES, CSSM_ALGID_3DES_3KEY, CSSM_ALGID_CAST, CSSM_ALGID_RC4

};

static const char *kCCAlgorithmNames[] = {"AES", "DES", "DES^3", "CAST", "RC4"};

#pragma mark -

@implementation MYSymmetricKey

- (id) _initWithKeyData: (NSData*)keyData

              algorithm: (CCAlgorithm)algorithm

             inKeychain: (MYKeychain*)keychain

{

    Assert(algorithm <= kCCAlgorithmRC4);

    Assert(keyData);

    SecKeyRef keyRef = NULL;

#if MYCRYPTO_USE_IPHONE_API

    NSNumber *keySizeInBits = [NSNumber numberWithUnsignedInt: keyData.length * 8];

    NSDictionary *keyAttrs = $dict( {(id)kSecClass, (id)kSecClassKey},

                                    //{(id)kSecAttrKeyClass, (id)kSecAttrKeyClassSymmetric},

                                    {(id)kSecAttrKeyType, [NSNumber numberWithUnsignedInt: kCSSMAlgorithms[algorithm]]},

                                    {(id)kSecAttrKeySizeInBits, keySizeInBits},

                                    {(id)kSecAttrEffectiveKeySize, keySizeInBits},

                                    {(id)kSecAttrIsPermanent, keychain ?$true :$false},

                                    {(id)kSecAttrCanEncrypt, $true},

                                    {(id)kSecAttrCanDecrypt, $true},

                                    {(id)kSecAttrCanWrap, $false},

                                    {(id)kSecAttrCanUnwrap, $false},

                                    {(id)kSecAttrCanDerive, $false},

                                    {(id)kSecAttrCanSign, $false},

                                    {(id)kSecAttrCanVerify, $false},

                                    {(id)kSecValueData, keyData},

                                    {(id)kSecReturnPersistentRef, $true});

    if (!check(SecItemAdd((CFDictionaryRef)keyAttrs, (CFTypeRef*)&keyRef), @"SecItemAdd")) {

        [self release];

        return nil;

    }

    Assert(keyRef, @"SecItemAdd didn't return anything");

#else

    Assert(NO,@"Unimplemented"); //FIX

    /* The technique below doesn't work, because there's no way to tell SecKeychainItemImport

       what algorithm to use when importing a raw key. Still looking for a solution... --jpa 4/2009

    SecKeyImportExportParameters params = {};

    keyRef = importKey(keyData, kSecItemTypeSessionKey, keychain.keychainRefOrDefault, &params);

    if (!keyRef) {

        [self release];

        return nil;

    }

     */

#endif

    self = [self initWithKeyRef: keyRef];

    CFRelease(keyRef);

    return self;

}

- (id) initWithKeyData: (NSData*)keyData

             algorithm: (CCAlgorithm)algorithm

{

    return [self _initWithKeyData: keyData algorithm: algorithm inKeychain: nil];

}

+ (MYSymmetricKey*) _generateSymmetricKeyOfSize: (unsigned)keySizeInBits

                                      algorithm: (CCAlgorithm)algorithm

                                     inKeychain: (MYKeychain*)keychain

{

#if MYCRYPTO_USE_IPHONE_API

    return [[[self alloc] _initWithKeyData: [MYCryptor randomKeyOfLength: keySizeInBits]

                                 algorithm: algorithm

                                inKeychain: keychain]

                    autorelease];

#else

    Assert(algorithm <= kCCAlgorithmRC4);

    CSSM_KEYATTR_FLAGS flags = CSSM_KEYATTR_EXTRACTABLE;

    if (keychain)

        flags |= CSSM_KEYATTR_PERMANENT | CSSM_KEYATTR_SENSITIVE | CSSM_KEYATTR_EXTRACTABLE;

    CSSM_KEYUSE usage = CSSM_KEYUSE_ANY;

    SecKeyRef keyRef = NULL;

    if (!check(SecKeyGenerate(keychain.keychainRefOrDefault,    // nil kc generates a transient key

                              kCSSMAlgorithms[algorithm],

                              keySizeInBits, 

                              0, usage, flags, NULL, &keyRef),

               @"SecKeyGenerate")) {

        return nil;

    }

    return [[[self alloc] initWithKeyRef: keyRef] autorelease];

#endif

}

+ (MYSymmetricKey*) generateSymmetricKeyOfSize: (unsigned)keySizeInBits

                                     algorithm: (CCAlgorithm)algorithm {

    return [self _generateSymmetricKeyOfSize: keySizeInBits

                                   algorithm: algorithm

                                  inKeychain: nil];

}

#if !TARGET_OS_IPHONE

- (NSData*) exportKeyInFormat: (SecExternalFormat)format

                      withPEM: (BOOL)withPEM

{

    SecKeyImportExportParameters params = {

        .version = SEC_KEY_IMPORT_EXPORT_PARAMS_VERSION,

        .flags = kSecKeySecurePassphrase,

    };

    CFDataRef data = NULL;

    if (check(SecKeychainItemExport(self.keyRef,

                                    format, (withPEM ?kSecItemPemArmour :0), 

                                    &params, &data),

              @"SecKeychainItemExport"))

        return [(id)CFMakeCollectable(data) autorelease];

    else

        return nil;

}

#endif

- (SecExternalItemType) keyType {

#if MYCRYPTO_USE_IPHONE_API

    return kSecAttrKeyClassSymmetric;

#else

    return kSecItemTypeSessionKey;

#endif

}

- (CCAlgorithm) algorithm {

    CSSM_ALGORITHMS cssmAlg;

#if MYCRYPTO_USE_IPHONE_API

    id keyType = [self _attribute: kSecAttrKeyType];

    Assert(keyType!=nil, @"Key has no kSecAttrKeyType");

    cssmAlg = [keyType unsignedIntValue];

#else

    cssmAlg = self.cssmKey->KeyHeader.AlgorithmId;

#endif

    switch(cssmAlg) {

        case CSSM_ALGID_AES:

            return kCCAlgorithmAES128;

        case CSSM_ALGID_DES:

            return kCCAlgorithmDES;	

        case CSSM_ALGID_3DES_3KEY:

            return kCCAlgorithm3DES;

        case CSSM_ALGID_CAST:

            return kCCAlgorithmCAST;

        case CSSM_ALGID_RC4:

            return kCCAlgorithmRC4;	

        default:

            Warn(@"CSSM_ALGORITHMS #%u doesn't map to any CCAlgorithm", cssmAlg);

            return (CCAlgorithm)-1;

    }

}

- (const char*) algorithmName {

    CCAlgorithm a = self.algorithm;

    if (a >= 0 && a <= kCCAlgorithmRC4)

        return kCCAlgorithmNames[a];

    else

        return "???";

}

- (unsigned) keySizeInBits {

#if MYCRYPTO_USE_IPHONE_API

    id keySize = [self _attribute: kSecAttrKeySizeInBits];

    Assert(keySize!=nil, @"Key has no kSecAttrKeySizeInBits");

    return [keySize unsignedIntValue];

#else

    const CSSM_KEY *key = self.cssmKey;

    Assert(key);

    return key->KeyHeader.LogicalKeySizeInBits;

#endif

}

- (NSString*) description {

    return $sprintf(@"%@[%u-bit %s]", [self class], self.keySizeInBits, self.algorithmName);

}

- (NSData*) _cryptData: (NSData*)data operation: (CCOperation)op options: (CCOptions)options

{

    NSData *keyData = self.keyData;

    Assert(keyData, @"Couldn't get key data");

    NSMutableData *output = [NSMutableData dataWithLength: data.length + 256];

    size_t bytesWritten = 0;

    CCCryptorStatus status = CCCrypt(op, self.algorithm, options, 

                                     keyData.bytes, keyData.length, NULL,

                                     data.bytes, data.length, output.mutableBytes, output.length,

                                     &bytesWritten);

    if (status) {

        Warn(@"MYSymmetricKey: CCCrypt returned error %i",status);

        return nil;

    }

    output.length = bytesWritten;

    return output;

}

- (NSData*) encryptData: (NSData*)data {

    return [self _cryptData: data operation: kCCEncrypt options: kCCOptionPKCS7Padding];

}

- (NSData*) decryptData: (NSData*)data {

    return [self _cryptData: data operation: kCCDecrypt options: kCCOptionPKCS7Padding];

}

@end

/* (Turned out I could just use SecKeyExport for this.)

static NSData* wrap(SecKeyRef key, CSSM_ALGORITHMS algorithm) {

    CAssert(key);

    const CSSM_KEY* cssmKey;

    const CSSM_ACCESS_CREDENTIALS *credentials;

    CSSM_CSP_HANDLE cspHandle;

    CSSM_CC_HANDLE ccHandle;

    if (!check(SecKeyGetCSSMKey(key, &cssmKey), @"GetCSSMKey")

        || !check(SecKeyGetCredentials(key, 

                                       CSSM_ACL_AUTHORIZATION_EXPORT_WRAPPED, 

                                       kSecCredentialTypeDefault,

                                       &credentials), @"GetCredentials")

        || !check(SecKeyGetCSPHandle(key, &cspHandle), @"GetCSPHandle")

        || !checkcssm(CSSM_CSP_CreateSymmetricContext(cspHandle, algorithm, CSSM_ALGMODE_WRAP,

                                                      NULL, NULL, NULL,

                                                      CSSM_PADDING_NONE, NULL, &ccHandle),

                      @"CSSM_CSP_CreateSymmetricContext"))

        return nil;

    CSSM_WRAP_KEY wrapped;

    NSData *result = nil;

    if(checkcssm(CSSM_WrapKey(ccHandle, credentials, cssmKey, NULL, &wrapped),

                 @"CSSM_WrapKey")) {

        result = [NSData dataWithBytes: wrapped.KeyData.Data 

                                length: wrapped.KeyData.Length];

    }

    CSSM_DeleteContext(ccHandle);

    return result;

}

*/